Download - Urea Final Report
Comprehensive design project
Group Members:
G.A.M.C. Ariyathilaka 050029P
A.N. Buddhika 050050V
K.R.M.G. Kahatapitiya 050192G
K.D.N. Karunarathna 050206G
D.D.D.P.Sandasiri 050404L
Project Coordinator:
Dr. Maneesha Gunasekara
UREA MANUFACTURING PLANT
CH 4200 – Comprehensive Design Project
Urea Manufacturing Plant
Comprehensive design project I
ACKNOWLEDGEMENT
First of all we would like to grant our heartiest gratitude to our project coordinator,
Dr. Maneesha Gunasekara (lecturer- Chemical & Process Engineering department, University of
Moratuwa) for all the guidance and support that she has given us to complete this design project
in a successful manner. Dear Madam, please expect our sincere thanks for your kind hearted
support and genuine friendly attitude shown towards our work. Thank you very much for
spending your precious time to share your knowledge & experience with us.
Then again, we must not forget all the staff members of Chemical & Process Engineering
department, including the head of the department Dr. Jagath Premachandra , for all the assistance
and support given us for accomplish the project. Without your support we may have not come
this far, so please accept our sincere thanks .Also we thank the level-4, semester-1 coordinator,
Dr. Suren Wijekoon, lecturer- Chemical & Process Engineering Department, University of
Moratuwa. And finally, a special thank should be given to the staff of Sri Lanka Custom Office
who provide us data related to urea imports.
Thank you,
G.A.M.C. Ariyathilaka
A.N. Buddhika.
K.R.M.G. Kahatapitiya
K.D.N. Karunarathna
D.D.D.P.Sandasiri
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Comprehensive design project II
PREFACE
The final year project is task, where we apply our knowledge & experience, gained throughout
the four year degree course, in a practical scenario. Here we have done it in our best capacity. It
is a step which finally determines the capability to perform as chemical engineers.
The ultimate goal of the final year design project on urea manufacturing plant is to
find out the feasibility of setting up such a plant in Sri Lanka. In Sri Lanka urea is being used as
a fertilizer in the agriculture sector. Other than as a fertilizer, urea is hardly used in any industry
or any other sector even though urea has number of industrial and commercial uses. Sri Lanka
imports urea from other countries such as Saudi Arabia, India, and China. The total import
volume of urea is around 330,000 MT per annum. Sri Lankan government gives urea fertilizer in
subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15 billion rupees for
fertilizer subsidies.
However in the past with the establishment of The Urea Plant at Sapugaskanda, Sri
Lanka became self sufficient in fertilizer requirements of the country. In 1982, the annual
production of urea at Sapugaskanda factory was 310,000 tons. Then the country's annual demand
was only 290,000 tons. The excessive production of 20,000 tons of urea was exported earning
foreign exchange around Rs. 200 million. In 1982 the annual savings of State Fertilizer
Corporation stood at Rs.750 million. In addition it had provided direct employment opportunities
to 1,250 workers. Sapugaskanda Urea plant was closed in January 1987.
In the world point of view urea is produced on a scale of some 100,000,000 tons per
year worldwide. Urea is produced from synthetic ammonia and carbon dioxide. Urea can be
produced as prills, granules, flakes, pellets, crystals, and solutions. More than 90% of world
production is destined for use as a fertilizer. Urea has the highest nitrogen content of all solid
nitrogenous fertilizers in common use (46.7%).Urea is highly soluble in water and is, therefore,
also very suitable for use in fertilizer solutions. Solid urea is marketed as prills or granules. The
advantage of prills is that, in general, they can be produced more cheaply than granules, which,
because of their narrower particle size distribution, have an advantage over prills if applied
mechanically to the soil.
In Sri Lanka establishing urea manufacturing plant has many advantages. It will
have greater effect on country‟s economy, development in agriculture sector, providing
employment and other tangible and intangible benefits. But without having an ammonia
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Comprehensive design project III
production process from which in most cases raw materials for urea manufacturing (ammonia
and carbon dioxide) is derived, it is rather difficult and unfeasible to establish a urea plant along
considering the availability of raw materials. Considering the project it is presumed that
ammonia and some instance carbon dioxide is imported.
According to the current demand of Sri Lanka, the urea demand of the country with
in next five years will be around 350,000 MT per annum. So we decided to design a Urea
manufacturing plant to fulfill that requirement. Our plant is operated for 328 days per year. And
rest of the year can be allocated for maintenance of the plant.
Constructing of this kind of manufacturing plant will enhance the country‟s
development since the ultimate product urea is directly related with country‟s economy and
growth in agriculture sector and a utility for many other industries. On the other hand the global
demand for urea is increasing rapidly; specially in Asian countries. Under those circumstances
we present the final year comprehensive design project which would be beneficial for country‟s
development.
The design project is combined in to this report, consist of 8 chapters. Chapters
include Literature survey, Process selection and Economic aspects, Process description and Flow
sheet, Site selection, Mass balance calculation, Material flow sheet, Heat balance calculation,
Tabulated heat balance.
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CONTENTS Page No
Chapter 01
1.0 Literature Survey.……………………………………………………………….. 02
1.1 Urea …………………………………………………………………………….. 02
1.1.1 Synthetic urea ………………………………………………………. 02
1.1.2 Commercial production of urea …………………………………….. 02
1.1.3 Chemical characteristics of urea …………………………………… 03
1.1.4 Physical characteristics of urea …………………………………….. 04
1.1.5 Raw materials of urea manufacturing ……………………………… 04
1.1.5.1 Ammonia …………………………………………………. 04
1.1.5.1.1 Ammonia Production ………………………… 05
1.1.5.1.2 Ammonia storage ……………………………. 06
1.1.5.2 Carbon Dioxide ………………………………………....... 06
1.1.6 Applications of urea……………………….……………………….. 06
1.1.6.1 Agricultural use …………………………………………… 06
1.1.6.1.1 Advantages of Fertilizer Urea……………….. 07
1.1.6.1.2 Soil Application and Placement of Urea…….. 07
1.1.6.1.3 Spreading of Urea…………………………… 08
1.1.6.2 Industrial use……………………………………………… 08
1.1.6.3 Further commercial uses………………………………….. 08
1.1.6.4 Laboratory use……………………………………………. 10
1.1.6.5 Medical use………………………………………………. 10
1.1.6.5.1 Drug use …………………………………….. 10
1.1.6.5.2 Diagnostic use ……………………………… 10
1.1.6.6 Textile use………………………………………………… 10
1.2 Global production and consumption of Urea………………………………….. 11
1.2.1 Range of global uses of urea……………………………………….. 14
1.3 Urea Prices…………………………………………………………………….. 15
1.4 Urea Production and Consumption in Sri Lanka……………………………… 15
Chapter 2
2.0 Process Selection & Economic Aspects……………………………………….. 18
2.1 Feasibility Study……………………………………………………………….. 18
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2.1.1 Introduction………………………………………………………… 18
2.1.2 Technical & Economic Feasibility………………………………… 19
2.1.2.1 Plant Capacity……………………………………………. 19
2.1.3 Social & Environmental Feasibility………………………………… 20
2.1.4 Plant Components………………………………………………….. 20
2.2 Process Selection………………………………………………………………. 21
2.2.1 Conventional Processes……………………………………………. 21
2.2.1.1 Once through Process…………………………………….. 21
2.2.1.2 Conventional Recycle Process …………………………… 21
2.2.2 Stamicarbon CO2 – stripping process……………………………… 24
2.2.3 Snamprogetti Ammonia and self stripping processes……………… 27
2.2.4 Isobaric double recycle process …………………………………… 28
2.2.5 ACES process……………………………………………………… 29
2.2.6 Process comparison………………………………………………… 29
2.2.6.1 Advantages of ACES Process……………………………. 30
Chapter 3
3.0 Process Description and flow sheet…………………………………………… 32
3.1 Process Description – ACES Process…………………………………………. 32
3.1.1 ACES Urea plants available in the world………………………….. 34
3.2 Main component of the process………………………………………………. 34
3.2.1 Reactor…………………………………………………………….. 34
3.2.2 Stripper…………………………………………………………….. 34
3.2.3 Carbamate Condenser……………………………………………… 35
3.2.4 Scrubber…………………………………………………………… 35
3.2.5 Medium Pressure Decomposer…………………………………….. 35
3.2.6 Low Pressure Decomposer………………………………………… 35
3.2.7 Medium Pressure Absorber………………………………………... 35
3.2.8 Low Pressure Absorber…………………………….……………… 36
3.2.9 Flash Separator…………………………………………………….. 36
3.2.10 Lower Separator………………………………………………….. 36
3.2.11 Upper Separator………………………………………………….. 36
3.2.12 Granulation Plant…………………………………………………. 37
3.3 Typical product quality………………………………………………………... 38
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Chapter 4
4.0 Site Selection & Plant Layout……………………………………………….… 40
4.1 Site Selection…………………………………………………………………… 40
4.1.1 Availability of raw materials……………………………………..… 40
4.1.2 Infrastructure facilities……………………………………………… 41
4.1.3 Legal obligations enforced by relevant authority or the government 42
4.1.4 Environment and Climate Conditions……………………………… 42
4.1.5 Labour Force availability…………………………………………… 42
4.1.6 Social considerations………………………………………………. 42
4.1.7 Waste Management……………………………………………...… 43
4.2 Plant Layout …………………………………………………………………… 43
4.2.1 Importance …………………………………………………..…….. 43
4.3 Environmental Impact Assessment……………………………………………. 44
4.3.1 Objectives of EIA Assessment…………………………………….. 44
4.3.2 Impact of the Urea Plant on the environment ……………………… 45
4.3.3 Emissions to Air…………………………………………………… 46
4.3.4 Emissions to Water………………………………………………… 46
4.3.5 Emissions to Land………………………………………………….. 46
4.3.6 Elimination Methods………………………………………………. 47
4.4 Safety Of the Urea Plant……………………………………………………….. 49
4.4.1 Safety factors relevant to urea …………………………………….. 50
4.4.2 Safety Factors Relevant to Ammonia……………………………… 53
4.4.3 Safety Factors Relevant to Ammonium Carbamate ……………… 57
4.4.4 Safety Factors Relevant to Biurete (byproduct)…………………… 60
Chapter 5
5.0 Mass Balance Calculation…………………………………………………….. 64
5.1 Material Balance……………………………………………………………… 64
5.1.1 Reactor…………………………………………………………….. 66
5.1.2 Stripper…………………………………………………………….. 67
5.1.3 Carbamate Condenser……………………………………………… 68
5.1.4 Scrubber…………………………………………………………… 69
5.1.5 High Pressure Decomposer………………………………...……… 70
5.1.6 Low Pressure Decomposer ………………………………………… 71
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5.1.7 Low Pressure Absorber……………………………………………. 72
5.1.8 Medium Pressure Absorber………………………………………… 73
5.1.9 Flash Separator…………………………………………………….. 74
5.1.10 Lower Separator………………………………………………….. 75
5.1.11 Upper Separator…………………………………………………... 76
5.1.12 Waste Water Treatment Unit………………………………….….. 77
5.1.13 Granulator………………………………………………………… 78
5.1.14 Screen……………………………………………………………... 79
5.1.15 Product Cooler……………………………………………………. 80
5.1.16 Bag Filter…………………………………………………………. 81
Chapter 6
Material Flow Sheet……………………………………………………………… 83
Chapter 7
7.0 Heat Balance Calculation……………………………………………………… 85
7.1 Main Process Energy Balance………………………………………………… 85
7.1.1 Reactor…………………………………………………………….. 88
7.1.2 Stripper…………………………………………………………….. 90
7.1.3 Scrubber…………………………………………….……………… 91
7.1.4 Carbamate Condenser……………………………………………… 93
7.1.5 High pressure decomposer………………………………………… 95
7.1.6 Low pressure decomposer………………………………………… 96
7.1.7 Low pressure absorber…………………………………………….. 98
7.1.8 High pressure absorber…………………………………………….. 99
7.1.9 Flash separator…………………………………………………….. 101
7.1.10 Lower separator………………………………………………….. 102
7.1.11 Upper separator…………………………………………………... 103
7.1.12 Process wastewater treatment unit……………………………….. 104
7.2 Granulation Plant……………………………………………………………… 105
7.2.1 Granulator…………………………………………………………. 105
7.2.2 Product cooler……………………………………………………... 105
Chapter 8
8.0 Tabulated Heat Balance……………………………………………………….. 107
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References ………………………………………………………... 109
List of Figures Page No
Figure 1.1 Chemical structures of urea molecules………………………………… 03
Figure 1.2 (a) The change in world consumption…………………………………. 11
Figure 1.3: Global distribution of the consumption of urea fertilizer…………….. 13
Figure 1.4 Urea import data……………………………………………………..… 16
Figure 2.1 Conventional process flow diagram…………………………………… 23
Figure 2.2 CO2 stripping process flow diagram…………………………………… 26
Figure 3.2 Functional block diagram of the ACES………………………………… 32
Figure 3.1 Process Flow Sheet…………………………………………………….. 32
Figure 3.3 Pipe and Instrumentation diagram……………………………………… 33
Figure 3.4 Granulation plant ……………………………………………………… 37
Figure 3.5 Spout-Fluid Bed Granulator……………………………………………. 37
Figure 3.6 Power Consumption of Spout-Fluid Bed Granulation…………………. 38
Figure 3.7 Various sizes of granules ……………………………………………… 38
Figure 4.1 Plant layout……………………………………………………….……. 43
Figure 6.1 Material Flow Sheet……………………………………………………. 83
List of Tables Page No
Table1.1 chemical characteristics of urea…….…………………………………… 04
Table 1.2 Physical Characteristics of Urea………………………………………… 04
Table 1.3 Urea Prices……………………………………………………………… 15
Table 3.1 ACES Urea plants available in the world Process………………………. 34
Table 4.1 Ammonia releases from urea plants…………………………………….. 45
Table 4.2 Typical consumption figures for a granulation plant…………………… 45
Table 4.3 Emissions from Urea manufacturing process………………………….. 45
Table 5.1 Compound in urea manufacturing………………………………………. 65
Table 8.1 Tabulated Heat Balance………………………………………………… 107
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CHAPTER 1
LITERATURE SURVEY
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1.0 Literature Survey
1.1 Urea
Urea is an oraganic compound with the chemical formula (NH2)2CO. Urea is also
known by the International Nonproprietary Name (INN) carbamide, as established by the World
Health Organization. Other names include carbamide resin, isourea, carbonyl diamide, and
carbonyldiamine.
1.1.1 Synthetic urea
It was the first organic compound to be artificially synthesized from inorganic
starting materials, in 1828 by Friedrich Wöhler, who prepared it by the reaction of potassium
cyanate with ammonium sulfate. Although Wöhler was attempting to prepare ammonium
cyanate, by forming urea, he inadvertently discredited vitalism, the theory that the chemicals of
living organisms are fundamentally different from inanimate matter, thus starting the discipline
of organic chemistry.
This artificial urea synthesis was mainly relevant to human health because of urea
cycle in human beings. Urea was discovered; synthesis in human liver in order to expel excess
nitrogen from the body. So in past urea was not considered as a chemical for agricultural and
industrial use. Within the 20th
century it was found to be a by far the best nitrogenic fertilizer for
the plants and became widely used as a fertilizer. Urea was the leading nitrogen fertilizer
worldwide in the 1990s.Apart from that urea is being utilized in many other industries.
Urea is produced on a scale of some 100,000,000 tons per year worldwide. For use in
industry, urea is produced from synthetic ammonia and carbon dioxide. Urea can be produced as
prills, granules, flakes, pellets, crystals, and solutions.More than 90% of world production is
destined for use as a fertilizer. Urea has the highest nitrogen content of all solid nitrogenous
fertilizers in common use (46.7%). Therefore, it has the lowest transportation costs per unit of
nitrogen nutrient. Urea is highly soluble in water and is, therefore, also very suitable for use in
fertilizer solutions (in combination with ammonium nitrate).
1.1.2 Commercial production of urea
Urea is commercially produced from two raw materials, ammonia, and carbon
dioxide. Large quantities of carbon dioxide are produced during the manufacture of ammonia
from coal or from hydrocarbons such as natural gas and petroleum-derived raw materials. This
allows direct synthesis of urea from these raw materials. The production of urea from ammonia
and carbon dioxide takes place in an equilibrium reaction, with incomplete conversion of the
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reactants. The various urea processes are characterized by the conditions under which urea
formation takes place and the way in which unconverted reactants are further processed.
Unconverted reactants can be used for the manufacture of other products, for example
ammonium nitrate or sulfate, or they can be recycled for complete conversion to urea in a total-
recycle process. Two principal reactions take place in the formation of urea from ammonia and
carbon dioxide. The first reaction is exothermic:
2 NH3 + CO2 ↔ H2N-COONH4 (ammonium carbamate)
Whereas the second reaction is endothermic:
H2N-COONH4 ↔ (NH2)2CO + H2O
Both reactions combined are exothermic.
1.1.3 Chemical characteristics of urea
The urea molecule is planar and retains its full molecular point symmetry, due to
conjugation of one of each nitrogen's P orbital to the carbonyl double bond. Each carbonyl
oxygen atom accepts four N-H-O hydrogen bonds, a very unusual feature for such a bond type.
This dense (and energetically favorable) hydrogen bond network is probably established at the
cost of efficient molecular packing: The structure is quite open, the ribbons forming tunnels with
square cross-section. Urea is stable under normal conditions.
Figure 1.1 Chemical structures of urea molecules
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IUPAC name Diaminomethanal
Chemical formula (NH2)2CO
Molecular mass 60.07 g/mol (approximate)
Dipole moment 4.56 p/D
pH (100g.L-1 in water, 20ºC) ~9
1.1.4 Physical characteristics of urea
Urea is a white odourless solid. Due to extensive hydrogen bonding with water (up
to six hydrogen bonds may form - two from the oxygen atom and one from each hydrogen) urea
is very soluble.
Density 1.33·10³ kg/m³, solid
Melting point 132.7 °C (406 K) decomposes
Boiling point NA
Solubility in water
108 g/100 ml (20 °C)
167 g/100 ml (40 °C)
251 g/100 ml (60 °C)
400 g/100 ml (80 °C)
733 g/100 ml (100 °C)
Vapour pressure
<0.1 hPa
Bulk density
0.8 kg.m-3
1.1.5 Raw materials of urea manufacturing
1.1.5.1 Ammonia
Ammonia, NH3, is a comparatively stable, colourless gas at ordinary temperatures,
with a boiling point of –33 C. Ammonia gas is lighter than air, with a density of approximately
0.6 times that of air at the same temperature. The characteristic pungent odors of ammonia can
be detected as low as 1-5ppm. Ammonia can be highly toxic to a wide range of organisms. In
humans, the greatest risk is from inhalation of ammonia vapour, with effects including irritation
and corrosive damage to skin, eyes and respiratory tracts. At very high levels, inhalation of
Table1.1 chemical characteristics of urea
Table 1.2 Physical Characteristics of Urea
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ammonia vapour can be fatal. When dissolved in water, elevated levels of ammonia are also
toxic to a wide range of aquatic organisms. Ammonia is highly soluble in water, although
solubility decreases rapidly with increased temperature. Ammonia reacts with water in a
reversible reaction to produce ammonium (NH4)+ and hydroxide (OH)
- ions, as shown in
equation.
Ammonia is a weak base, and at room temperature only about 1 in 200 molecules are
present in the ammonium form (NH4)+. The formation of hydroxide ions in this reaction
increases the pH of the water, forming an alkaline solution. If the hydroxide or ammonium ions
react further with other compounds in the water, more ammonia with react to reestablish the
equilibrium.
NH3 + H2O (NH4)+
+ OH-
While ammonia-air mixtures are flammable when the ammonia content is 16-25% by
volume, these mixtures are quite difficult to ignite. About 85% of the ammonia produced
worldwide is used for nitrogen fertilizers. The remainder is used in various industrial products
including fibers, animal feed, and explosives.
1.1.5.1.1 Ammonia Production
Essentially all the processes employed for ammonia synthesis are variations of the
Haber-Bosch process, developed in Germany from 1904-1913. This process involves the
reaction of hydrogen and nitrogen under high temperatures and pressures with an iron based
catalyst. This process also requires large energy consumption. Ammonia is generally produced at
a few large plants with stream capacities of 1000 tonnes/day or greater. The formation of
ammonia from hydrogen and nitrogen is a reversible reaction, as shown in equation [2]. The
fraction of ammonia in the final gas mixture is dependent on the conditions employed. Unreacted
hydrogen and nitrogen gases separated from the ammonia and are usually recycled. In almost all
modern plants, the ammonia produced is recovered by condensation to give liquid ammonia.
H2 + 3N2 2NH3
The source of nitrogen is always air. Hydrogen can be derived from a number of raw
materials including water, hydrocarbons from crude oil refining, coal, and most commonly
natural gas. Hydrogen rich reformer off-gases from oil refineries have also been used as a source
of hydrogen. Steam reforming is generally employed for the production of hydrogen from these
raw materials. This process also generates carbon dioxide, which can then be used as a raw
material in the production of urea.
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Trace impurities in the feed gases, such as sulphur compounds and chlorides, can
have a detrimental effect on the production of ammonia by poisoning the catalysts employed.
The feed gases, therefore, need to be purified prior to use.
1.1.5.1.2 Ammonia storage
Anhydrous ammonia is usually stored as a liquid in refrigerated tanks at –33.3 C and
atmospheric pressure, often in doubled-walled tanks with the capacity for hundreds or thousands
of tonnes. The low temperature is usually maintained by the venting of ammonia gas. The vented
gas is reliquefied for recycling, or absorbed in water to make aqueous ammonia. Relatively small
quantities of anhydrous ammonia are sometimes stored under pressure in spherical vessel at
ambient temperature. Ammonia is corrosive to alloys of copper and zinc and these materials
must never be used in ammonia service. Iron and steel are usually the only metals used in
ammonia storage tanks, piping and fittings.
1.1.5.2 Carbon Dioxide
CO2 is a odourless and colourless gas which contain 0.03% in the atmosphere. It is
emitted as a pollutant from number of industries. CO2 can be obtained from ammonia production
process as a by product.
1.1.6 Applications of urea
1.1.6.1 Agricultural use
More than 90% of world production is destined for use as a fertilizer. Urea is used as
a nitrogen-release fertilizer, as it hydrolyses back to ammonia and carbon dioxide, but its most
common impurity, biuret, must be present at less than 2%, as it impairs plant growth. Urea has
the highest nitrogen content of all solid nitrogeneous fertilizers in common use (46.4%N.) It
therefore has the lowest transportation costs per unit of nitrogen nutrient. In the past decade urea
has surpassed and nearly replaced ammonium nitrate as a fertilizer
In the soil, urea is converted into the ammonium ion form of nitrogen. For most
floras, the ammonium form of nitrogen is just as effective as the nitrate form. The ammonium
form is better retained in the soil by the clay materials than the nitrate form and is therefore less
subject to leaching. Urea is highly soluble in water and is therefore also very suitable for use in
fertilizer solutions, e.g. in “foliar feed‟ fertilizers.
Commercially, fertilizer urea can be purchased as prills or as a granulated material.
In the past, it was usually produced by dropping liquid urea from a "prilling tower" while drying
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the product. The prills formed a smaller and softer substance than other materials commonly
used in fertilizer blends. Today, though, considerable urea is manufactured as granules. Granules
are larger, harder, and more resistant to moisture. As a result, granulated urea has become a more
suitable material for fertilizer blends.
1.1.6.1.1 Advantages of Fertilizer Urea
Urea can be applied to soil as a solid or solution or to certain crops as a foliar spray.
Urea usage involves little or no fire or explosion hazard.
Urea's high analysis, 46% N, helps reduce handling, storage and transportation costs over
other dry N forms.
Urea manufacture releases few pollutants to the environment.
Urea, when properly applied, results in crop yield increases equal to other forms of
nitrogen.
Nitrogen from urea can be lost to the atmosphere if fertilizer urea remains on the soil
surface for extended periods of time during warm weather. The key to the most efficient use of
urea is to incorporate it into the soil during a tillage operation. It may also be blended into the
soil with irrigation water. A rainfall of as little as 0.25 inches is sufficient to blend urea into the
soil to a depth at which ammonia losses will not occur.
Urea breakdown begins as soon as it is applied to the soil. If the soil is totally dry, no
reaction happens. But with the enzyme urease, plus any small amount of soil moisture, urea
normally hydrolizes and converts to ammonium and carbon dioxide. This can occur in 2 to 4
days and happens quicker on high pH soils. Unless it rains, urea must be incorporated during this
time to avoid ammonia loss. Losses might be quite low if the soil temperature is cold. The
chemical reaction is as follows:
CO(NH2)2 + H2O + urease 2NH3 +CO2
1.1.6.1.2 Soil Application and Placement of Urea
The volatility of urea depends to a great extent on soil temperature and soil pH. If
properly applied, urea and fertilizers containing urea are excellent sources of nitrogen for crop
production. After application to the soil, urea undergoes chemical changes and ammonium (NH4
+) ions form. Soil moisture determines how rapidly this conversion takes place.
When a urea particle dissolves, the area around it becomes a zone of high pH and
ammonia concentration. This zone can be quite toxic for a few hours. Seed and seedling roots
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within this zone can be killed by the free ammonia that has formed. Fortunately, this toxic zone
becomes neutralized in most soils as the ammonia converts to ammonium. Usually it's just a few
days before plants can effectively use the nitrogen. Although urea imparts an alkaline reaction
when first applied to the soil, the net effect is to produce an acid reaction.
Urea or materials containing urea should, in general, be broadcast and immediately
incorporated into the soil. Urea-based fertilizer applied in a band should be separated from the
seed by at least two inches of soil.
1.1.6.1.3 Spreading of Urea
Urea can be bulk-spread, either alone or blended with most other fertilizers. Urea
often has a lower density than other fertilizers with which it is blended. This lack of "weight"
produces a shorter "distance-of-throw" when the fertilizer is applied with spinner-type
equipment. In extreme cases this will result in uneven crop growth and "wavy" or "streaky"
fields.
Urea and fertilizers containing urea can be blended quite readily with
monoammonium phosphate (11-52-0) or diammonium phosphate (18-46-0). Urea should not be
blended with superphosphates unless applied shortly after mixing. Urea will react with
superphosphates, releasing water molecules and resulting in a damp material which is difficult to
store and apply.
Urea fertilizer can be coated with certain materials, such as sulfur, to reduce the rate
at which the nitrogen becomes available to plants. Under certain conditions these slow-release
materials result in more efficient use by growing plants. Urea in a slow-release form is popular
for use on golf courses, parks, and other special lawn situations.
1.1.6.2 Industrial use
Urea has the ability to form 'loose compounds', called clathrates, with many organic
compounds. The organic compounds are held in channels formed by interpenetrating helices
comprising of hydrogen-bonded urea molecules. This behaviour can be used to separate
mixtures, and has been used in the production of aviation fuel and lubricating oils. As the helices
are interconnected, all helices in a crystal must have the same 'handedness'. This is determined
when the crystal is nucleated and can thus be forced by seeding. This property has been used to
separate racemic mixtures.
1.1.6.3 Further commercial uses
A stabilizer in nitrocellulose explosives
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A reactant in the NOx-reducing SNCR and SCR reactions in exhaust gases from
combustion, for example, from power plants and diesel engines
A component of fertilizer and animal feed, providing a relatively cheap source of
nitrogen to promote growth
A raw material for the manufacture of plastics, to be specific, urea-formaldehyde resin
A raw material for the manufacture of various glues (urea-formaldehyde or urea-
melamine-formaldehyde); the latter is waterproof and is used for marine plywood
An alternative to rock salt in the de-icing of roadways and runways; it does not promote
metal corrosion to the extent that salt does
An additive ingredient in cigarettes, designed to enhance flavour
A browning agent in factory-produced pretzels
An ingredient in some hair conditioners, facial cleansers, bath oils, and lotions
A reactant in some ready-to-use cold compresses for first-aid use, due to the endothermic
reaction it creates when mixed with water
A cloud seeding agent, along with salts, to expedite the condensation of water in clouds,
producing precipitation
An ingredient used in the past to separate paraffins, due to the ability of urea to form
clathrates (also called host-guest complexes, inclusion compounds, and adducts)
A flame-proofing agent (commonly used in dry chemical fire extinguishers as Urea-
potassium bicarbonate)
An ingredient in many tooth whitening products
A cream to soften the skin, especially cracked skin on the bottom of one's feet
An ingredient in dish soap.
To make potassium cyanate
A melt agent used in re-surfacing snowboarding halfpipes and terrain park features
A raw material for melamine production More than 95% of all melamine production is
based on urea. Stamicarbon‟s parent company DSM is the largest melamine producer in
the world.
A supplementary substitute protein source in feedstuffs for cattle and other ruminants.
Because of the activity of micro-organisms in their cud, ruminants are able to metabolize
certain nitrogen containing compounds, including urea, as protein substitutes. In the USA
this capability is exploited on a large scale. Western Europe, in contrast, uses little urea in
cattle feed.
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Feed for hydrolyzation into ammonia which in turn is used to reduce emissions from
power plants and combustion engines.
Other, miscellaneous products such as de-icing material for airport runways. Although on
a smaller scale than as a fertilizer or as raw material for synthetic resins, urea is also used
as a raw material or auxiliary material in the pharmaceutical industry, the fermenting and
rewing industries and in the petroleum industry.
1.1.6.4 Laboratory use
Urea is a powerful protein denaturant. This property can be exploited to increase the
solubility of some proteins. For this application, it is used in concentrations up to 10 M. Urea is
used to effectively disrupt the noncovalent bonds in proteins. Urea is an ingredient in the
synthesis of urea nitrate. Urea nitrate is also a high explosive very similar to ammonium nitrate,
however it may even be more powerful because of its complexity.
1.1.6.5 Medical use
1.1.6.5.1 Drug use
Urea is used in topical dermatological products to promote rehydration of the skin. If
covered by an occlusive dressing, 40% urea preparations may also be used for nonsurgical
debridement of nails. This drug is also used as an earwax removal aid. Like saline, urea injection
is used to perform abortions. It is also the main component of an alternative medicinal treatment
referred to as urine therapy.
1.1.6.5.2 Diagnostic use
Isotopically-labeled urea (carbon-14 - radioactive, or carbon-13 - stable isotope) is used
in the urea breath test, which is used to detect the presence of the bacteria Helicobacter pylori
(H. pylori) in the stomach and duodenum of humans. The test detects the characteristic enzyme
urease, produced by H. pylori, by a reaction that produces ammonia from urea. This increases the
pH (reduces acidity) of the stomach environment around the bacteria. Similar bacteria species to
H. pylori can be identified by the same test in animals such as apes, dogs, and cats .
1.1.6.6 Textile use
Urea is a raw material for urea-formaldehyde resins production in the adhesives and
textile industries. A significant portion of urea production is used in the preparation of urea-
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formaldehyde resins. These synthetic resins are used in the manufacture of adhesives, moulding
powders, varnishes and foams. They are also used for impregnating paper, textiles and leather. In
textile laboratories they are frequently used both in dyeing and printing as an important auxiliary,
which provides solubility to the bath and retains some moisture required for the dyeing or
printing process.
1.2 Global production and consumption of Urea
Commercial urea production began in the 1920s with the development of the Haber-Bosch
process.
Figure 1.2 (a) The change in world consumption (million metric tons of N) of total synthetic
nitrogen fertilizers (solid line) and urea consumption (solid bars) since 1960. Data for 2005–
2020 (shown as the shaded region) are calculated assuming an annual increase of 3% in total
consumption and 5% in the fraction that is urea. (b) Same data as in panel (a) with the fraction
that is urea displayed as a percentage of the total nitrogen fertilizer.
Urea is processed into granules or other forms. Urea production is energy intensive.
Most commonly, it is produced using natural gas, so the major producing regions are those
where natural gas is abundant. Several leading manufacturing countries for urea are Russia,
Canada, and Saudi Arabia, but other Middle East producers, including Iran and Iraq are (or were
before the Gulf Wars) significant. In the US, urea production facilities are located mainly in the
Gulf of Mexico states.
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Production of urea has at least doubled every decade since 1980 in the Middle East,
increasing from 2 million metric tons per year in 1980 to 10 million metric tons year per in 2000.
Further expansion of production is anticipated in the coming years in Kuwait, Qatar, Egypt,
Oman and Iran. From the mid-1970s to the early 1990s, Russia (USSR) erected at least 40 new
ammonia and urea production facilities. Production of urea in China tripled from 1989 to 1999.
Dramatic increases in global production have also occurred in many countries since 2000, with
several Latin American countries increasing production by more than 25%. As late as the 1960s,
urea represented only about 5% of world nitrogen fertilizer use. However, urea usage escalated
in the 1980s, such that it represented about 40% of global nitrogen fertilizer by the early 1990s,
and soon thereafter urea surpassed ammonium nitrate as the most common nitrogen fertilizer. It
is now estimated that urea represents >50% of world nitrogen fertilizer (Figure 1b).
Assuming urea consumption continues at 5% per year, as projected for many parts of
the world, urea consumption may reach 70% of total nitrogen use by the end of the next decade
(Figure 1b): this is a dramatic global change in the composition of nitrogen applied to land
throughout the globe. Such projections depend on global commodity markets, construction of
new plants, and other factors that are difficult to project, but most of this increase is expected to
occur in developing countries, particularly in Asia and Latin America. China and India together
account for about half of the global consumption, and have at least doubled their consumption of
urea in the past decade. In India, Bangladesh and Pakistan, urea fertilizer has been heavily
subsidized (as much as 50% of the cost of production) leading to its widespread use and over-
application.
The US and Canada now represent about 20% of the global urea market, with urea
constituting about 30% of US synthetic nitrogen fertilizer usage. Consumption is increasing even
in regions where land applications of nitrogen have heretofore been low. The rural Canadian
provinces of Manitoba, Saskatchewan and Alberta, for example, are now the regions where over
70% of Canada‟s urea is consumed. Urea is the only form of fertilizer used in British Columbia
forests. In Latin America, consumption of urea has fluctuated more than in Asia during the past
decade due to various economic crises and unstable political environments, leading to fluctuating
incentives and subsidies.
This global trend in increased urea consumption represents both a net increase in
total nitrogen applied, as well as a shift from the use of nitrate or anhydrous ammonium to urea.
These increases parallel the increases in the production of both cereal and meat (associated with
increasing human population) that have occurred globally in the past several decades. Urea is
used in the production of virtually all crops from corn to Christmas trees, sugar cane to sweet
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potatoes, and vegetables to vineyards. Urea is preferable to nitrate for growing rice in flooded
soils, and thus the Far East and the Mid-East are major consumers of urea. In coated form, urea
becomes a slow-release fertilizer and this is one of the most popular forms for applications to
lawns, golf courses, and parks, as well as many crops.
The global shift toward the use of urea fertilizer stems from several advantages it has
over other fertilizer forms. It is less explosive than ammonium and nitrate when stored, it can be
applied as a liquid or solid, and it is more stable and cost effective to transport than other forms
of reactive nitrogen. The increasing production of „granular‟ urea has contributed to its
widespread use, as this is safe and easy to transport. Urea also contains twice the nitrogen of
ammonium sulfate, making application rates per unit of fertilizer less costly for individual
farmers. With the growth of large, industrial farms, the economics and safety of urea transport
and storage are thus major factors in the shift away from ammonium nitrate.
Figure 1.3: Global distribution of the consumption of urea fertilizer, in metric tons per year by
country, in 1960 (upper panel) and in 1999 (lower panel), based on data from the Global
Fertilizer Industry data base (FAO 2001),These estimates of urea consumption do not include
uses other than fertilizer.
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1.2.1 Range of global uses of urea
While more than 75% of manufactured urea is consumed as nitrogen fertilizer, there
are other significant uses of urea, which also are increasing globally. One such use is as a feed
additive for ruminants, used to stimulate gut microbial flora. This application represents about
10% of non-fertilizer usage. Urea can be added directly to feed, such as in urea-treated wheat or
rice straw, or mixed with molasses („urea–molasses licks‟ or „urea multi-nutrient blocks‟) for
sheep, cattle, water buffalo, and horses. Urea may also be used as a fertilizer of the grasslands on
which cattle or sheep may graze.
Another direct application of urea to land is as urea-based herbicides or pesticides
(sulfonyl urea pesticides). In this case, urea is chemically synthesized with a poison or inhibitor.
Sulfonyl urea is one of the preferred herbicides for broadleaf and grassy weeds. It is also
commonly used in non-agricultural situations, such as to control weeds in railroad and electric
utility rights of way. Urea-based herbicides potentially have a large impact by both increasing
urea inputs and reducing the potential for local uptake. Urea has long been used as a de-icer.
Commercial airports and airfields are the largest consumers of these de-icing materials, although
recommendations are now in place to reduce its usage in the US and elsewhere because of its
recognized contribution to water pollution. Even with such reductions, it is still the de-icer of
choice under some weather conditions. It is also used fairly extensively for domestic ice-melting
applications (e.g. roads and sidewalks). Urea may also be spread on agricultural crops to prevent
frost when temperatures drop to a level that may cause crop damage, and commercial
formulations of urea are available for this purpose.
Urea is also used in some direct applications to seawater. It is used in the growing
world aquaculture industry. In intensive shrimp culture, for example, ponds may be fertilized
with urea and superphosphate to initiate an algal bloom that eventually serves as food for the
commercial resource. A significant proportion of such nutrients are subsequently discharged to
local waters with pond effluent, as only a small fraction of added nutrients ultimately winds up in
marketable product.
Urea may also be spread on coastal oil spills, to stimulate the growth of natural
bacteria populations which break down the oil; it was widely used, for example, during the
Exxon Valdez spill, and has been used in numerous other spills since. For the Exxon Valdez
spill, fertilizer applications continued for years following the initial crisis, and this approach was
estimated to have enhanced the degradation of the oil by 2–5-fold.
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In addition to the direct applications of urea to land and sea, urea is used in many
other applications, including manufacture of a wide range of common materials such as urea
formaldehyde and plastics. This use represents about 50% of the non-fertilizer urea. Urea is also
an additive in fire retardant paints, tobacco products, and in some wines. In the cosmetics
industry, urea is an ingredient in moisturizing creams. There are numerous uses of urea in
holistic medicine therapies. One application currently being considered which would greatly
expand the global use of urea is as a reductant in catalytic and non-catalytic reduction of
combustion products in vehicles.
1.3 Urea Prices
The world price for urea has trended downwards in real terms since 1975, although it can
be volatile. In real terms (1990s), the price per ton was $438 in 1975; $309 in 1980; $199 in
1985, and $131 in 1990. These prices are on a bulk FOB basis, and freight and bagging charges
of about $20 to $25 per ton must be added to arrive at bagged import costs. From 1991 to 2000,
the prices of urea ($/ton) are shown in the table below:
year 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 Mean
Urea
($/ton)
$151 $123 $ 94 $131 $194 $187 $128 $103 $ 78 $112 $130
Source: IMF, International Financial Statistics, Yearbook and July, 2001 issues.
Table 2.3 Urea Prices
1.4 Urea Production and Consumption in Sri Lanka
In Sri Lanka urea is being used as a fertilizer in the agriculture sector. Other than as
a fertilizer, urea is hardly used in any industry or any other sector even though urea has number
of industrial and commercial uses.
Sri Lanka imports urea from other countries such as Saudi Arabia, India, and China. .
The total import volume of urea is around 330,000 MT per annum. Sri Lankan government gives
urea fertilizer in subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15
billion rupees for fertilizer subsidies.
However in the past with the Urea Plant at Sapugaskanda, Sri Lanka was able to
became self sufficient in fertilizer requirements of the country. In 1982, the annual production of
urea at Sapugaskanda factory was 310,000 tons. Then the country's annual demand was only
290,000 tons. The excessive production of 20,000 tons of urea was exported earning foreign
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UREA IMPORTS
0
2000
4000
6000
8000
10000
12000
14000
1997 1999 2000 2001 2002 2004 2005 2006 2007
Year
To
tal
Co
st
in R
s M
illi
on
s
TOTAL UREA IMPORTS
0
50000
100000
150000
200000
250000
300000
350000
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
Qu
an
tity
(M
T)
exchange around Rs. 200 million. In 1982 the annual savings of State Fertilizer Corporation
stood at Rs.750 million. Urea plant was closed in January 1987.
According to the Sri Lanka Custom data records, following graphs shows total urea
imports to the country within past 10 years and relative costs involved.
With the development in agriculture sector under present government policies and
considering global food crisis, urea demand will further increase in spite there is a concern to use
organic fertilizers such as compost instead of urea. Urea is being used as the main fertilizer for
paddy as well as for other crops. Excessive applying of urea without considering the requirement
has damage water bodies in some part of Sri Lanka.
Figure 1.4 Urea import data
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CHAPTER 2
PROCESS SELECTION AND
ECONOMIC ASPECTS
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2.0 Process Selection & Economic Aspects
2.1 Feasibility Study
2.1.1 Introduction
Urea white crystalline solid containing 46% nitrogen is widely used in the agriculture
industry as an animal feed additive and fertilizer. Agriculture forms the major sector in the
national economy of the majority of the countries in the Southeast Asian region. As these
countries try to expand the sector, through diversification of agriculture and extensive multiple
cropping programs, the demand for agriculture chemicals growing day by day.
Large population countries like China, India, Pakistan, and Bangladesh are largely
manufacturing the Urea for Domestic consumption. Due to high cost of the production facility
Government incentives are common in 3rd
world countries. In Middle East Saudi Arabia
developed the large production facility of Urea production as an allied industry of the petroleum
product. The surplus amount is being exported to neighboring countries.
Sri Lanka imports urea from other countries such as Saudi Arabia, India, and China. .
The total import volume of urea is around 310,000 MT per annum. Sri Lankan government gives
urea fertilizer in subsidized price for farmers. From the budget 2008, Sri Lanka allocated 15
billion rupees for fertilizer subsidies.
The Urea Plant at Sapugaskanda, Sri Lanka was established in 1980s to fulfil
fertilizer requirement of the country. In 1982, the annual production of urea at Sapugaskanda
factory was 310,000 tons. Then the country's annual demand was only 290,000 tons. The
excessive production of 20,000 tons of urea was exported earning foreign exchange around Rs.
200 million. In 1982 the annual savings of State Fertilizer Corporation stood at Rs.750 million.
In addition it had provided direct employment opportunities to 1,250 workers. So the previous
plant is Sapugaskanda had been able to gain profits while making Sri Lanka self sufficient in
urea.
In the present urea fertilizer prices in global markets are increasing and most
countries establishing urea manufacturing plants to support growing agriculture sector while
saving cost of urea fertilizer imports. It is necessary to establish urea manufacturing plant in Sri
Lanka in order to meet growing demand for urea fertilizer and to save fertilizer subsidies given
by the government. Apart from those benefits it can earn foreign exchange by exporting excess
production and provide employment for local community.
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2.1.2 Technical & Economic Feasibility
When considering economic feasibility, raw material cost could be higher than usual
since all most all urea manufacturing plants is being operated along with ammonia plants in
order to produce raw materials (Ammonia and carbon dioxide: The carbon is produced as a bye-
product from the ammonia plant) for urea manufacturing process.
To establish a urea plant without ammonia plant, raw materials has to be imported. It
is not a better option, but under the circumstances Ammonia has to be imported from abroad.
Considering the carbon dioxide, it is emitted by number of industries as a waste from which it
has to be derived and purify. If it is not viable it is too has to be imported. Transportation cost
will quite high (shipping costs, import taxes etc) so imported raw materials will be higher than
when produced in ammonia plant.
Plant technology is considered as high. Japan, China and North European countries
are licensing the technology. Government incentives can be obtained for construction and
operation since high costs are involved.
The plant can be ordered directly from the manufacturers which basically sell the
license of technology. Local fabrication can be carried out. Where as more critical equipments
can be imported. Latest technology for confirming the quality and purity of the finished good is
very important to complete the existing units.
Companies involve in urea manufacturing technology and have license for technology.
1. Toyo Engineering corporation ( Japan )
2. Mitsubishi Heavy industries ( Japan )
2.1.2.1 Plant Capacity
Urea plant capacity is on the rise since its establishment in 1940. In 1969 1800
MT/day plant was the largest. In Nineties 2000 tons urea plants become standardized. Now up to
3500 tons/day plants are under construction and planning.
In this project we are planning to establish 1070 Mt/day plant having overall annual
production of 350,000 MT. Plant is expected to operate 328 days per annum. Current Sri Lankan
annual demand for urea is around 310,000 and it is not expected to fluctuate very much
according to the statistical data obtained for past ten years. So Plant capacity is sufficient for
meeting the current demand as well as growing demand in the future.
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2.1.3 Social & Environmental Feasibility
Environmental feasibility is discussed under environmental impact assessment (EIA) and in site
selection. Social issues are considered under site selection.
2.1.4 Plant Components
The components of a urea plant can be divided in to two categories
1. Static Equipment
2. Rotating equipment
Static Equipment
Reactor:
Reactor is the largest and heaviest key equipment in the urea plant. This is the place
where Ammonia and Carbon di-oxide react together. The performance of the reactor influences
the performance of the whole urea plant.
The size of the shell depends upon the size of plant. For a plant of 2000 tons capacity the height
of the shell will be around 30 Meters and Dia around 3 meters.
Stripper
Stripper is also a key component where the excess ammonia is separated.
Carbamate Condensers
They are relatively smaller in size
HP Rotating Machines
CO2 Compressors
This is the largest and most critical rotating equipment. Very large compressors are used of
approximate capacities of around 30,000 N cubic meter/hour capacity
HP Ammonia pumps and Carbomate pumps piping
Stainless steel 316 L pipes are utilized
HP Control Valves
Various control valves are required. The most critical is the solution feed control valve from the
reactor to stripper. The material is stainless steel
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2.2 Process Selection
Several processes are used to urea manufacturing. Some of them are used
conventional technologies and others use modern technologies to achieve high efficiency. These
processes have several comparable advantages and disadvantages based on capital cost,
maintenance cost, energy cost, efficiency and product quality. Some of the widely used urea
production processes are
1. Conventional processes
2. Stamicarbon CO2 – stripping process
3. Snamprogetti Ammonia and self stripping processes
4. Isobaric double recycle process
5. ACES process
2.2.1 Conventional Processes
2.2.1.1 Once through Process
In this process non converted ammonia was neutralized with acid such as nitric acid
to produce ammonium salt such as ammonium nitrate as co products of urea production. In this
way, a relatively simple urea process scheme was realized. The main disadvantages of this
process are the large quantity of ammonia salt formed as co product and the limited amount of
overall carbon dioxide conversion that can be achieved.
2.2.1.2 Conventional Recycle Process
Here all of the non converted ammonia and carbon dioxide were recycled to the urea
reactor. In first generation of this process the recirculation of non converted NH3 and CO2 was
performed in two stage. The first recirculation was operated at medium pressure (18-25 bar); the
second at low pressure (2-5 bar). The first recirculation comprises at least a decomposition
heater, in which carbamate decompose into gaseous NH3 and CO2, and while excess NH3
evaporate simultaneously. The off gas from this first decomposition step was subjected to
rectification, from which relatively pure ammonia at the top and a bottom product consisting of
an aqueous ammonium carbamate solution were obtained. Both products are recycled separately
to the urea reactor. In these processes, all non converted CO2 was recycled as associated water
recycle. Because of the detrimental effect of water on reaction conversion, achieving a minimum
CO2 recycle so achieve maximum CO2 conversion was more important than achieving a low
NH3 recycle. All conventional processes therefore typically operate at high NH3:CO2 ratios (4-5
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mol/mol) to maximize CO2 conversion per pass. Although some of these conventional processes
partly equipped with ingenious heat exchanging net works have survived until now. Their
importance decreased rapidly as the so-called stripping process was developed.
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Figure 2.1 Conventional process flow diagram
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2.2.2 Stamicarbon CO2 – stripping process
In this process to achieve maximum urea yield per pass through the reactor at the
stipulated optimum pressure of 140 bar, an NH3:CO2 molar ratio of 3:1 is applied. The greater
part of the unconverted carbamate is decomposed in the stripper, where ammonia and carbon
dioxide are stripped off. This stripping action is effected by countercurrent contact between the
urea solution and fresh carbon dioxide at synthesis pressure. Low ammonia and carbon dioxide
concentration in the stripped urea solution are obtained. Such that the recycle from the low
pressure recirculation stage is minimized. These low concentration of both ammonia and carbon
dioxide in the stripper effluent can be obtained at relatively low temperatures of the urea solution
because carbon dioxide is only sparingly soluble under such conditions.
Condensation of ammonia and carbon dioxide gases, leaving the stripper, occurs in
the high pressure carbamate condenser as synthesis pressure. As a result, the heat liberated from
ammonium carbamate formation is at a high temperature. This heat is used for the production of
4.5bar steam for use in the urea plant itself. The condensation in the high pressure carbamate
condenser is not effected completely. Remaining gases are condensed in the reactor and provide
the heat required for the dehydration of carbamate, as well as for heating the mixture to its
equilibrium temperature. In recent improvement to this process, the condensation of off gas from
the stripper is carried out in a pre reactor, where sufficient residence time for the liquid phase is
provided. As a result of urea and water formation in condensing zone, the condensation
temperature is increased, thus enabling the production of steam at higher pressure level.
The feed carbon dioxide, invariably originating from an associated ammonia plant,
always contains hydrogen. To avoid the formation of explosive hydrogen-oxygen mixture in the
tail gas of the plant, hydrogen is catalytically removed from the CO2 feed. Apart from the air
required for this purpose, additional air is supplied to the fresh CO2 input stream. This extra
potion of oxygen is needed to maintain a corrosion-resistance layer on the stainless steel in the
synthesis section. Before the inert gases, mainly oxygen and nitrogen, are purged from the
synthesis section, they are washed with carbamate solution from the low pressure recirculation
stage in the high pressure scrubber to obtain a low ammonia concentration in the subsequently
purged gas. Further washing of the off gas is performed in a low pressure absorber to obtain a
purge gas that is practically ammonia free. Only one low pressure recirculation stage is required
due to the low ammonia and carbon dioxide in the stripped urea solution. Because of the ideal
ratio between ammonia and carbon dioxide in the recovered gases in this section, water dilution
of the resultant ammonium carbamate is at a minimum despite the low pressure (about 4 bar). As
a result of efficiency of the stripper, the quantities of ammonium carbamate for recycle to the
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synthesis section are also minimized, and no separate ammonia recycle is required.
The urea solution coming from the recirculation stage contains about 75 wt% urea.
This solution is concentrated in the evaporation section. If the process is combined with a
prilling tower for final product shaping, the final moisture content of urea from the evaporation
section is 0.25 wt%. If the process is combined with a granular unit, the final moisture content
may wary from 1 to 5 wt%, depending on granulation requirements. Higher moisture content can
be realized in a single stage evaporator; where as low moisture content are economically
achieved in a two stage evaporation section.
When urea with an extremely low biuret content is required ( at maximum of 0.3
wt%) pure urea crystals are produced in a crystallization section. These crystals are separated
from the mother liquor by combination of sieve bends and centrifuges and are melted prior to
final shaping in a prilling tower or granulation unit.
The process condensate emanating from water evaporation from the evaporation or
crystallization sections contains ammonia and urea. Before this process condensate is purged,
urea is hydrolyzed into ammonia and carbon dioxide, which are stripped off with steam and
return to urea synthesis via the recirculation section. This process condensate treatment section
can produce water with high purity, thus transforming this “waste water” treatment into the
production unit of a valuable process condensate, suitable for, e.g., cooling tower or boiler feed
water makeup. Since the introduction of the Stamicarbon CO2 stripping process, some 125 units
have been built according to this process all over the world.
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Figure 2.2 CO2 stripping process flow diagram
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2.2.3 Snamprogetti Ammonia and self stripping processes
In the first generation of NH3 and self strip ping processes, ammonia was used as
stripping agent. Because of the extreme solubility of ammonia in the urea containing synthesis
fluid, the stripper effluent contained rather large amount s of dissolved ammonia, causing
ammonia overload in down stream section of the plant. Later versions of the process abandoned
the idea of using ammonia as stripping agent; stripping was achieved only by supply of heat.
Even without using ammonia as a stripping agent, the NH3:CO2 ratio in the stripper effluent is
relatively high. So the recirculation section of the plant requires an ammonia-carbomate
separation section
The process uses a vertical layout in the synthesis section. Recycle within the
synthesis section, from the stripper via the high pressure carbamate condenser, through the
carbamate separator back to the reactor, is maintained by using an ammonia-driven liquid-liquid
ejector. In the reactor, which is operated at 150 bars, NH3:CO2 molar feed ratio of 3.5 is applied.
The stripper is of the falling film type. Since stripping is achieved thermally, relatively high
temperatures (200-210 0C) are required to obtain a reasonable stripping efficiency. Because of
this high temperature, stainless steel is not suitable as a construction material for the stripper
from a corrosion point of view; titanium and bimetallic zircornium – stainless steel tubes have
been used
Off gas from the stripper is condensed in a kettle type boiler. At the tube side of this
condenser the off gas is absorbed in recycled liquid carbamate from the medium pressure
recovery section. The heat of absorption is removed through the tubes, which are cooled by the
production of low pressure steam at the shell side. The steam produced is used effectively in the
back end of the process.
In the medium pressure decomposition and recirculation section , typically operated
at 18 bar, the urea solution from the high pressure stripper is subjected to the decomposition of
carbamate and evaporation of ammonia. The off gas from this medium pressure decomposer is
rectified. Liquid ammonia reflux is applied to the top of this rectifier; in this way a top product
consisting of pure gaseous ammonia and a bottom product of liquid ammonium carbamate are
obtained. The pure ammonia off gas is condensed and recycled to the synthesis section. To
prevent solidification of ammonium carbamate in the rectifier, some water is added to the bottom
section of the column to dilute the ammonium carbamate below its crystallization point. The
liquid ammonium carbamate-water mixture obtained in this way is also recycled to the synthesis
section. The purge gas of the ammonia condenser is treated in a scrubber prior to being purged to
the atmosphere.
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The urea solution from the medium pressure decomposer is subjected to a second
low pressure decomposition step. Here further decomposition of ammonium carbamate is
achieved, so that a substantially carbamate –free aqueous urea solution is obtained. Off gas from
this low pressure decomposer is condensed and recycled as an aqueous ammonium carbamate
solution to the synthesis section via the medium pressure recovery section.
Concentrating the urea water mixture obtained from the low pressure decomposer is
preformed in a single or double evaporator depending on the requirement of the finishing
section. Typically, if prilling is chosen as the final shaping procedure, a two stage evaporator is
required, whereas in the case of a fluidized bed granulator a single evaporation step is sufficient
to achieve the required final moisture content of the urea melt. In some versions of the process,
heat exchange is applied between the off gas from the medium pressure decomposer and the
aqueous urea solution to the evaporation section. In this way, the consumption of low pressure
steam by the process is reduced.
The process condensate obtained from the evaporation section is subjected to a
desorption hydrolysis operation to recover the urea and ammonia contained in the process
condensate.
2.2.4 Isobaric double recycle process
This process is developed by Montedison, is characterized by recycle of most of the
un reacted ammonia and ammonium carbamate in two decomposer in series, both operating at
the synthesis pressure. A high molar NH3:CO2 ratio (4:1 to 5:1) in the reactor is applied. As a
result of this choice ratio, the reactor effluent contains a relatively high amount of non converted
ammonia. In the first, steam heated, high pressure decomposer, this large quantity of free
ammonia is mainly removed from the urea solution. Most of the residual solution, as well as
some ammonium carbamate, is removed in the second high pressure decomposer where steam
heating and CO2 stripping are applied. The high pressure synthesis section is followed by two
low pressure decomposing stages of traditional design, where heat exchange between the
condensing off gas of the medium pressure decomposition stage and the aqueous urea solution to
the final concentration section improves the overall energy consumption of the process. Probably
because of the complexity of this process, it has not achieved great popularity so far. This
process or parts of the process are used in four revamps of older conventional plant.
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2.2.5 ACES process
ACSE (Advanced Process for Cost and Energy Saving) process has been developed
by Toyo Engineering Corporation. Its synthesis section consist of the reactor, stripper, two
parallel carbamate condensers and a scrubber all operated at 175 bar.
The reactor is operated at 1900C and an NH3:CO2 molar feed ratio of 4:1. Liquid
ammonia is fed directly to the reactor, whereas gaseous carbon dioxide after compression is
introduced into the bottom of the stripper as a stripping aid. The synthesis mixture from the
reactor, consisting of urea, unconverted ammonium carbamate, excess ammonia, and water, is
fed to the top of the stripper.
2.2.6 Process comparison .
Process Advantages Disadvantages
Conventional Processes -
Once through process
Simple process Large quantity of
ammonia salt is formed as
co product
Overall carbon dioxide
conversion is low.
High production cost
High energy cost
High environment
pollution
Conventional Processes
–
Conventional recycle
process
High CO2 conversion High production cost
High energy cost
High environment
pollution
Stamicarbon CO2 –
stripping process
Has high urea yield per
pass
High purity
High production cost
High energy cost
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Snamprogetti Ammonia
and self stripping
processes
Low consumption of low
pressure steam
High production cost
High energy cost
Isobaric double recycle
process
Complex process
ACES process Low production cost
High energy recovery
Low environment
pollution
High efficiency
High capital cost
Among above urea manufacturing processes, ACES process is selected because of it has
following advantages compared to other processes
2.2.6.1 Advantages of ACES Process
Less HP piping and construction materials owing to lower elevation layout, fewer HP
vessels and simplified synthesis loop
Easier erection using commonly available construction equipment and techniques owing
to low elevation layout and fewer and smaller HP vessels
Easier operation supported by forced circulation by HP ejector, low elevation layout and
fewer HP equipment
Easier maintenance owing to low elevation layout and fewer HP equipment
Less energy consumption owing to optimized synthesis conditions and proprietarily
designed reactor and stripper
Even though initial capital investment is higher than the other processes, it will
overcome by lower production cost per metric ton of urea
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CHAPTER 3
PROCESS DESCRIPTION AND
FLOW SHEET
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3.0 Process Description and flow sheet
3.1 Process Description – ACES Process
Advanced Process for Cost and Energy process consists of the reactor, stripper, two
parallel carbamate condensers and a scrubber. All above equipments are operated at 175 bar.
Figure 3.1 Functional block diagram of the ACES
Process
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The reactor is operated at 1900C and an NH3:CO2 molar feed ratio of 4:1. Liquid
ammonia is fed directly to the reactor, whereas gaseous carbon dioxide after compression is
introduced into the bottom of the stripper as a stripping aid. The synthesis mixture from the
reactor, consisting of urea, unconverted ammonium carbamate, excess ammonia, and water, is
fed to the top of the stripper. The stripper has two functions. Its upper part is equipped with trays
where excess ammonia is partly separated from the stripper feed by direct countercurrent contact
of the feed solution with the gas coming from the lower part of the stripper. This pre stripping in
the top is said to be required to achieve effective CO2 stripping in the lower part. In the lower
part of the stripper (a falling film heater), ammonium carbamate is decomposed and the resulting
CO2 and NH3 as well as the excess NH3 are evaporated by CO2 stripping and steam heating. The
overhead gaseous mixture from the top of the stripper is introduced into the carbamate
condenser. Here the gaseous mixture is condensed and absorbed by the carbamate solution
coming from the medium pressure recovery stage. Heat liberated in the high pressure carbamate
condenser is used to generate low pressure steam. The gas and liquid from the carbamate
condensers are recycled to the reactor by gravity flow. The urea solution from the stripper, with a
typical NH3 content of 15 wt%, is purified further in the subsequent medium and low pressure
decomposers, operating at 17.5 and 2.5 bars, respectively. Ammonia and carbon dioxide
separated from the urea solution here are recovered through stepwise absorption in the low and
medium pressure absorbers. Condensation heat in the medium pressure absorber is transferred
directly to the aqueous urea solution feed in the final concentration section; the purified urea
solution is concentrated further either by two stage evaporation up to 99.7 % for urea prill
production or by a single evaporation 98.5 % for urea granule production. Water vapour formed
in the final concentrating section is condensed in surface condensers to form process condensate.
Part of this condensate is used as an absorbent in the recovery sections, where as remainder is
purified in the process condensate treatment section by hydrolysis and steam stripping, before
being discharge from the urea plant.
The highly concentrated urea solution is finally processed either through the prilling
tower or via the urea granulator. Instead of concentration via evaporation, the ACES process can
also be combined with a crystallization section to produce urea with low biuret content.
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3.1.1ACES Urea plants available in the world
3.2 Main component of the process
3.2.1 Reactor
The reactor is operated at 190 °C and 175 bar. NH3:CO2 molar feed ratio to the
reactor is 4:1. One pass conversion rate of CO2 to urea is about 68%. NH3 is directly fed to the
reactor. Following reaction occurs inside the reactor.
NH2COONH4 + heat ↔ NH2CONH2 + H2O ∆H = +23 kJ/mol
2NH3 + CO2 ↔ NH2COONH4 + heat ∆H = -84 kJ/mol
3.2.2 Stripper
Carbon dioxide is introduced into the bottom of the stripper as a stripping aid. The
synthesis mixture from the reactor, consisting of urea, unconverted ammonium carbamate,
excess ammonia, and water, is fed to the top of the stripper. Medium pressure steam is supplied
to the stripper. The stripper has two functions. Its upper part is equipped with trays where excess
ammonia is partly separated from the stripper feed by direct countercurrent contact of the feed
solution with the gas coming from the lower part of the stripper. This pre stripping in the top is
said to be required to achieve effective CO2 stripping in the lower part. In the lower part of the
stripper (a falling film heater), ammonium carbamate is decomposed and the resulting CO2 and
NH3 as well as the excess NH3 are evaporated by CO2 stripping and steam heating. The overhead
gaseous mixture from the top of the stripper is introduced into the carbamate condenser.
Following reaction occurs inside the stripper.
Table 3.1 ACES Urea plants available in the world Process
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NH2COONH4 + heat ↔ 2NH3 + CO2 ∆H = +84 kJ/mol
NH3(l) → NH3(g)
3.2.3 Carbamate Condenser
Carbamate condenser is fed with overhead gaseous mixture from the top of the
stripper, In this unit the gaseous mixture is condensed and absorbed by the carbamate solution
coming from the medium pressure recovery stage. Heat liberated in the high pressure carbamate
condenser is used to generate low pressure steam. The gas and liquid from the carbamate
condensers are recycled to the reactor by gravity flow.
2NH3 + CO2 ↔ NH2COONH4 + heat ∆H = -84 kJ/mol
NH3(g) → NH3(l)
3.2.4 Scrubber
In the scrubber Ammonia and Carbon Dioxide coming from the reactor are absorbed
to ammonia and ammonium carbamate solution which is going to Carbamate Condenser.
3.2.5 Medium Pressure Decomposer
The urea solution from the stripper, with a typical NH3 content of 15 wt%, is purified
further in the medium pressure decomposer operating at 17.5 bars. No external heat supply.
NH2COONH4 + heat ↔ 2NH3 + CO2 ∆H = +84 kJ/mol
NH3(l) → NH3(g)
3.2.6 Low Pressure Decomposer
After the medium pressure decomposer, further purification of urea solution occurs inside
the low pressure decomposer which is operating at 2.5 bar. External heat supply is available. all
ammonia and ammonium carbamate are removed by the Low Pressure Decomposer.
NH2COONH4 + heat ↔ 2NH3 + CO2 ∆H = +84 kJ/mol
NH3(l) → NH3(g)
3.2.7 Medium Pressure Absorber
In medium pressure absorber ammonia and carbon dioxide separated from the urea
solution in medium pressure decomposer are recovered. Condensation heat in the medium
pressure absorber is transferred directly to the aqueous urea solution feed in the final
concentration section.
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2NH3 + CO2 ↔ NH2COONH4 + heat ∆H = -84 kJ/mol
3.2.8 Low Pressure Absorber
In low pressure absorber ammonia and carbon dioxide separated from the urea
solution in low pressure decomposer are recovered. Heat release from that reaction is used to
produce steam at 2 bar. This steam is used for evaporation process of lower and upper separator.
2NH3 + CO2 ↔ NH2COONH4 + heat ∆H = -84 kJ/mol
3.2.9 Flash Separator
This unit is operated at 1.0 bar and 110 °C. Here by reducing the pressure, let water
to evaporate and concentrate the urea solution.
H2O(l) → H2O(g)
3.2.10 Lower Separator
This is a calendria type evaporator. This is operated at 0.55 bar vacuum pressure and
at 110 °C Here the purified urea solution is further concentrated and required heat is taken from
2 bar pressure steam produced in low pressure absorber.
3.2.11 Upper Separator
This is evaporative type separator. This is operated at 0.55 bar vacuum pressure and
at 112 °C Urea solution coming from the lower separator is further concentrated. Output from
that unit has 99.2% pure urea. After that urea solution is sent to granulation section.
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3.2.12 Granulation Plant
The Urea Granulation process consists of following three
sections.
• granulation section
• recycle and product cooling section
• dust removal and recovery section
Aqueous urea solution from urea plant is fed to
the granulator to enlarge recycle particles in the granulator.
In the granulator, the granules are dried and cooled
simultaneously. The granulator is operated at 110-115oC
and at slightly negative pressure. Enlarged urea particles
are cooled to about 90ºC in the after-cooler inside the
granulator to be transported to the recycle section.
The discharged granules are separated into three sizes, product, small and large size by
the screen. Product size granules are further cooled below 60ºC in the product cooler to be sent
to the urea storage or bagging facility. Large size granules are crushed by the crusher. The rushed
particles and smaller size particles from the screen are recycled to the granulator as seed.Urea
dust contained in the exhaust air from the granulator and the product cooler is scrubbed in the
dust scrubber by contacting counter currently with aqueous urea solution. The urea dust content
in the exit air of the bag filter is 30 mg/m3 or less. Urea recovered in the bag filter, approximately
2.5-3.5 % of production rate, is recycled to the urea granulator.
Figure 3.4 Granulation plant
Figure 3.5 Spout-Fluid Bed Granulator
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3.3 Typical product quality
Total Nitrogen 46.3wt%
Biuret 0.7wt%
Moisture 0.25wt%
Formaldehyde 0.45wt%
Size (2-4mm) 95wt%
Hardness 3.5kg at 3mm
Various sizes of granules
Figure 3.7 Various sizes of granules
Figure 3.6 Power Consumption of Spout-Fluid Bed Granulation
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CHAPTER 4
SITE SELECTION
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4.0 Site Selection & Plant Layout
4.1 Site Selection
Site selection is the making the ultimate choice of site where business or
manufacturing plant is going to be established. It is an important task to be done in a business
case. By selecting the suitable site for the manufacturing plant it would be able to reduce the
transportation cost of raw materials and energy, make easy access to infrastructure facilities,
availability of labour force and many other benefits.
Selection should be done by considering cost and benefits of available alternative
sites. It is a strategic decision to be made, where improper decision may cause considerable loss.
So it may requied to select ideal or optimum location for the business.
Following Facts should be concern regarding site selection
Availability of raw material
Infrastructure facilities
Legal obligations enforced by relevant authority or the government
Environment and climate conditions
Labour force availability
Social considerations
Waste management
4.1.1 Availability of raw materials
Main raw materials for urea manufacturing are ammonia and carbon dioxide.
Currently ammonia plant is not there in Sri Lanka. Ammonia has to be imported from abroad.
Considering the carbon dioxide, it is emitted by number of industries as a waste from which it
has to be derived and purify. Otherwise any alternative option such as importing should be
concerned. In case of ammonia it is cost effective to locate the site near a harbor or sea where it
is directly taken in to the storage tanks. The previous urea plant was there in Sapugaskanda along
with ammonia plant and petroleum refinery. It is not viable to consider that site since ammonia
plant is not there and considering transportation cost. Considering available sites in costal areas
in Sri Lanka we select two sites Hambantota and Trincomalee for assessment. Hambantota has
many advantages regarding a large chemical plat like urea.
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Hambanthota is developing area under “Mahinda Chinthana” concept. Many
developing projects are underway. An international sea port is going to be established in
hambantota which can handle large ships which are unable to access in the Colombo port. Also
infrastructure facilities will be developed along with these projects. Vast amount of land is
available for low cost in order to establish the plant closed to Hambantota port. Even if there are
no enough qualified employees in Hambantota area, due to rapid development along with good
infrastructure facilities it would be easy to attract employees from outside areas. Government
welcomes projects related to hambantota area and many benefits can be gain such as reduction in
tax, grace periods for loans etc. The government is planning to establish a petroleum refinery in
Hambanthota. In Trincomalee much of above mentioned benefits are there, but considering the
establishment of petroleum refinery and massive port compared to Trincomalee, Hambantota
becomes the more suitable option.
It is not economical to import ammonia and carbon dioxide from abroad because of
high transportation cost and additional amount of money have to be spend on buying those
materials. Those raw materials can be produced at low cost in Sri Lanka. So it is better to have
an ammonia plant. Under the government‟s plan to establish a petroleum refinery in
Hambanthota, hydrogen can be gained as a byproduct from petroleum refinery and it can be use
as a raw material for ammonia production. So it would be better to have ammonia plant in future
to aid urea production.
4.1.2 Infrastructure facilities
Hambanthota is a one of main cities in southern part of Sri Lanka which is situated
237 km away from Colombo. Since it is a coastal area we have to consider climate as well as
infrastructure facilities such as water, electricity and roads. Direct Infrastructure facilities for
urea plant such as transportation, electricity, telecommunication and indirect infrastructures for
the employees such as education, health, food, accommodations etc. are being recently
developed in Hambantota. On the other hand in Hambanthota there is scarcity of sufficient water
reservoirs for the various purpose of the urea plant due to dry zone. But we can fulfill some
amount of our water requirement like cooling water using sea water and other requirements using
water distribution project which is being develop along with other development projects.
Highways are being constructed connecting hambantota port and other developing sites such as
air port. So Transportation of other required materials would be more convenient. Other private
and public sector facilities including telecommunication, government authorities will also be
developed.
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4.1.3 Legal obligations enforced by relevant authority or the government
Yala Sanctuary Park is situated in Hambanthota area. So government obligation may
arise for such a urea manufacturing plant construction. Some families may have to resettle to
clear the construction area of urea manufacturing plant. Legal obligations may arise from people.
Compensation and resettlement should be done in order to avoid such difficulties. Since
chemicals are used in the manufacturing it would be necessary to comply with government
regulations regarding handling and storing of such chemicals. Emissions from the urea plant
should be under permissible conditions. Since site is in costal area air emissions may not have
much impact. Sound regulations may not have to be considered extensively since area is remote.
Tax and other financial considerations may vary with related to selected site.
4.1.4 Environment and Climate Conditions
Hambantota is located in semi-arid zone in Sri Lanka. Climate is much dryer, but in
the coastal side it is much humid so it can lead to corrosion in metallic component in the plant.
Law rain fall is an advantage for urea production. Because of coastal wind emissions from the
plant may dilute easily and air emission problems may not arise. Only difficulty is the lack of
water resources. Sea water should be utilized in order to fulfill water requirement for some
extent. But water is needed to be transported from available area nearby. Accommodation for
labours and other staff should be constructed considering dry weather.
4.1.5 Labour Force availability
Many people in rural areas like Hambantota are not permanently employed. People
from villages may move in to cities nearby or even to Colombo to find employment. So
establishing a plant in such area will produce around 1200 direct jobs and many other indirect
job opportunities. It will solve unemployment problem to considerable extent. So labour
availability is not an issue, but difficulties may arise in finding qualified people.
4.1.6 Social considerations
Obstacles may arise from residential people and from environmentalists. Peoples will
resist construction work and may take legal actions. Proper mechanism to resettle residential
people who may lose their homes should be established collaboration with government.
Environmental concerns should be considered including air emissions, waste disposal, sound
levels and necessary steps should be take to control or maintain under permissible levels. Also
site should cause minimum environment damage during construction and operation.
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4.1.7 Waste Management
Waste management restrictions are being enforced by the regulations. Plant site
should accommodate disposal of waste in to the sea or to the land. Chemical wastes are there
from the plants which are considered hazardous. Selected site should have facilities for both
waste processing and for storage until waste is properly disposed. Social considerations are
important in waste management. Locating plant in a remote location is an advantage.
4.2 Plant Layout
The efficiency of production depends on how well the various machines; production
facilities and employee‟s amenities are located in a plant. Only the properly laid out plant can
ensure the smooth and rapid movement of material, from the raw material stage to the end
product stage.
Plant layout refers to the arrangement of physical facilities such as machinery,
equipment, storages, departments etc. with in the factory building in such a manner so as to have
quickest flow of material at the lowest cost and with the least cost in processing the product from
the raw material to the finished product.
4.2.1 Importance
Plant layout is an important decision as it represents long-term commitment. An ideal
plant layout should provide the optimum relationship among output, floor area and
manufacturing process. It facilitates the production process, minimizes material handling, time
and cost, and allows flexibility of operations, easy production flow, makes economic use of the
building, promotes effective utilization of manpower, and provides for employee‟s convenience,
safety, comfort at work, maximum exposure to natural light and ventilation. It is also important
because it affects the flow of material and processes, labour efficiency, supervision and control,
use of space and expansion possibilities etc.
An efficient plant layout is one that can be instrumental in achieving the Following objectives:
a) Proper and efficient utilization of available floor space
b) To ensure that work proceeds from one point to another point without any delay
c) Provide enough production capacity.
d) Reduce material handling costs
e) Reduce hazards to personnel
f) Utilize labour efficiently
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g) Increase employee morale
h) Reduce accidents
i) Provide for volume and product flexibility
j) Provide ease of supervision and control
k) Provide for employee safety and health
l) Allow ease of maintenance
m) Allow high machine or equipment utilization
n) Improve productivity
4.3 Environmental Impact Assessment
An Environment Impact Assessment is an assessment of the possible positive impact
or negative impact which the project may have on the natural environment. The purpose of the
assessment is to ensure that decision makers consider environmental impacts used to decide
whether to proceed with the project. The International Association for Impact Assessment
(IAIA) defines an environmental impact assessment as "the process of identifying, predicting,
evaluating and mitigating the biophysical, social, and other relevant effects of development
proposals prior to major decisions being taken and commitments made.
4.3.1 Objectives of EIA Assessment
To ensure that proponents take primary responsibility for protection of the environment
influenced by their proposals
To ensure that best practicable measures are taken to minimize adverse impacts on the
environment, and that proposals meet relevant environmental objectives and standards to
protect the environment, and implement the principles of sustainability
To provide opportunities for local community and public participation, as appropriate,
during the assessment of proposals
To encourage proponents to implement continuous improvement in environmental
performance and the application of best practice environmental management in
implementing their proposal
To ensure that independent, reliable advice is provided to the Government before
decisions are made
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4.3.2 Impact of the Urea Plant on the environment
In the early part of previous decade ammonia consumption per ton of final product of 575
kg or even higher used to be acceptable. This figure implies however a loss of some 8 kg per
tonne of final product produced (Table 1), which for a 2000 mtd plant would result in a loss of
16 mtpd ammonia either in the form of urea or straight ammonia.
Presently ammonia consumptions of some 567 kg per tonne are released in the large single
stream plants. Since this figure is very close to the theoretical consumption figure, the conclusion
is that losses in steady operation are approaching the zero targets.
Ammonia releases from urea plants
Early nineteen eighties
Presently
8 kg NH3/mt final product
0.7 kg NH3/mt final product
Not only ammonia, carbon dioxide and urea releases from process plants have a
negative influence on the environment but also the unnecessary use of energy is negative from an
environmental point of view and from the economic point of view as well.
Following table shows the present typical energy consumption for urea production
Typical consumption figures for a granulation plant
Steam (22 bar, 330oC)
Steam (4 bar saturated) (production)
Electricity (including granulation section)
Cooling water (including granulation section)
805 kg/mt urea
-415 kg/mt urea
50 kWh/mt urea
58 mt/mt urea
Emissions from Urea manufacturing process are listed below.
Substance
Emission Media
To
Atmosphere To Water Via Solid Waste
Ammonia
Formaldehyde
Methanol
Total Nitrogen
Particulate Matter (PM10)
Volatile Organic
Compounds(VOCs)
Table 4.3 Emissions from Urea manufacturing process
Table 4.2 Typical consumption figures for a granulation plant
Table 4.1 Ammonia releases from urea plants
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4.3.3 Emissions to Air
Air emissions may be categorised as either fugitive or point source emissions.
Fugitive Emissions
These are emissions that are not released through a vent or stack. Examples of fugitive
emissions include dust from stockpiles, volatilization of vapour from vats, open vessels, or
spills and materials handling. Emissions emanating from ridgeline roof-vents, louvres, and
open doors of a building as well as equipment leaks, and leaks from valves and flanges are
also examples of fugitive emissions.
Point Source Emissions
These emissions are exhausted into a vent or stack and emitted through a single point source
into the atmosphere. Above table highlights common air emissions from urea manufacturing
processes.
4.3.4 Emissions to Water
Emissions of substances to water can be categorised as discharges to:
Surface waters (eg. lakes, rivers, dams, and estuaries);
Coastal or marine waters
Storm water
Because of the significant environmental hazards posed by emitting toxic substances
to water, most facilities emitting above listed substances to waterways are required by the
relevant environment authority to closely monitor and measure these emissions. The existing
sampling data can be used to calculate annual emissions. If no wastewater monitoring data
exists, emissions to process water can be calculated based on a mass balance or using emission
factors.
4.3.5 Emissions to Land
Emissions of substances to land on-site include solid wastes, slurries, and sediments.
Emissions arising from spills, leaks, and storage and distribution of materials containing listed
substances may also occur to land. These emission sources can be broadly categorised as:
surface impoundments of liquids and slurries; and
unintentional leaks and spills.
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In general, there are four types of emission estimation techniques (EETs) that may be used to
estimate emissions from the facility. The four types are:
Sampling or direct measurement;
Mass balance;
Fuel analysis or other engineering calculations; and
Emission factors
4.3.6 Elimination Methods
Presently plants are equipped with the following features to keep the effluent and emission at
extremely low levels:
N/C ratio meter
Waste water treatment section
Absorbers
Special operational facilities
N/C ratio meter in the Synthesis section
Instead of using a gaschromatograph or a mass spectrometer in the gas phase of the
synthesis section, Nitrogen/Carbon (N/C) ratio meters are installed in the liquid phase (reactor
liquid outlet) of the urea synthesis section
The principle of this N/C meter is based on the linear relationship between liquid
density and the N/C ratio. The density is measured continuously with a solartron meter, being an
instrument in which vibrations are measured in an extremely accurate way whereby the
vibrations are a measure of the density of the reactor liquid.
This N/C ratio meter allows the process at all times to be operated at the optimum ratio to
achieve highest reactor efficiency combined with higher energy efficiency. Special procedures
are used to eliminate emissions during start-up.
Urea plant waste water treatment section
The process water in urea plants contains ammonia, carbon dioxide and urea. The
concentrations of these components vary within a range depending on the operating conditions,
On average, the concentrations in the process water are about 6 wt.% ammonia, 4 wt.% carbon
dioxide and 1 wt.% urea.
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Sources of the ammonia and urea are
Condensate from the evaporators.
Off-gases from the recirculation section, which are absorbed in the process water.
Off-gases from the synthesis section, which are absorbed in the process water.
Flush and purge water for pumps.
Liquid drains.
The purpose of the process water treatment is to remove ammonia, carbon dioxide
and urea from the process condensate. For every tonne of urea produced, approximately 0.3
tonnes of water are formed. This water is usually discharged from the urea concentration and
evaporation section of the plant. Removal of ammonia and urea from wastewaters can be a
problem as it is difficult to remove one in the presence of the other. One method used to
overcome this problem is the hydrolysis of urea to ammonium carbamate, which is decomposed
to ammonia and carbon dioxide. These gases can then be stripped from the wastewaters. Urea
plants are in operation that produces wastewaters with ammonia and urea levels below 1ppm.
This water can then be used for a variety of purposes depending on the required quality such as
cooling water or Boiling Feed Water make-up. The recovered ammonia and carbon dioxide are
returned to the process to be subsequently converted into urea.
Absorbers
Absorbers are used in urea plant to eliminate emissions to the atmosphere, can be classified as
follows:
(1) The vent from the synthesis section of the plant
The purge from the urea synthesis section contains inerts, ammonia and carbon
dioxide. To avoid ammonia emissions from this purge a low pressure absorber is installed in
purge stream. First the ammonia is washed out with a large flow of low concentrated and cooled
process water and secondly the remaining ammonia is absorbed in cooled condensate or clean
waste water.
(2) The vent from the low pressure section of the plant
The ammonia and carbon dioxide present in the off gases of the recirculation section,
the Process Water Treatment System and the evaporation section are washed out in an
atmospheric absorber where large amounts of cooled low concentrated process water are used to
absorb all the ammonia present in said off gases.
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Special start-up, shut-down and draining facilities
Because of the present low releases during steady state operation in urea
manufacturing the consideration regarding environmental issues has changed towards further
reducing of effluents and emissions from non-continuous sources during non-steady state
conditions such as start-up and shut-down situations. A change in the start-up procedure of the
urea synthesis section has reduced the impact on the environment considerably.
Presently the ability to measure the feed flows (NH3
and CO2) very accurate in
combination with the ability to measure the N/C ratio have enabled us to feed the synthesis
section from the very beginning of the start-up with the correct NH3/CO
2 ratio, thus eliminating
the need, during the initial stage of start-up, to vent excess CO2
accompanied by some NH3
into
the atmosphere.
Special shut-down and draining facilities assure that non converted NH3
and CO2
are
recovered by the process after a shut-down. To achieve this facility to feed clean water to dilute
the carbamate formed from non converted NH3
and CO2
from the synthesis section has been
introduced.
The dilution should be to the extent that no ammonia will escape from the liquid
under atmospheric pressure. The water is in principle introduced in the low pressure carbamate
condenser and subsequently cooled to increase absorption capacity, and drained in the ammonia
water tank. After restart of the plant the NH3
and CO2
in this tank are recovered via the waste
water treatment section. The clean water used for the dilution may be an amount of clean waste
water stored for such purpose. In case sufficient condensate is available in the complex no such
additional storage of clean waste water is required and condensate may be used as well.
4.4 Safety Of the Urea Plant
It is must to consider occupational safety and health when designing a manufacturing
plant. Safety is the major factor in any industrial process to safeguard employees, environment,
surrounding living peoples etc. Also there are legal obligations which are imposed by
government for chemical processing factories to operate and maintain.
When considering the safety, it is mainly due to the risk of urea which is the main
product of plant and ammonia; one of the main raw materials for production and risk caused by
other intermediate product.
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4.4.1 Safety factors relevant to urea
Stability and Reactivity
Produce biuret when expose to heat
Urea has high solubility. So it should store under dry conditions.
It has high stability and low reactivity with normal conditions
Flammability
Urea is non-flammable material
Flash point: Not applicable
Flammability limits: Not applicable
Auto-ignition temperature: Not applicable
The substance decomposes on heating above melting point, producing toxic gases,
and reacts violently with strong oxidants, nitrites, inorganic chlorides, chlorites and perchlorates,
causing fire and explosion hazard
Hazard identification
Classified as hazardous chemical according to criteria in the HS (Minimum Degrees of Hazard)
Regulations 2001
Route of entry and health hazards
Harmful if swallowed. - It may cause irritation
Harmful if inhaled.
Causes serious eye irritation.
Harmful to terrestrial vertebrates.
Inhalation: Slight irritant. Elevated exposure may result in mucous membrane irritation (nose &
throat). may cause nausea, vomiting, diarrhea and GI irritation.
Skin: Irritant. Prolonged contact may result in irritation, itching and possible skin rash.
Eyes: Irritant. May cause lachrymation, irritation, pain & redness
Ingestion: Has diuretic effect. Ingestion of large quantities may lead to nausea and vomiting.
No adverse health effects expected under normal conditions. Urea can be irritating to
skin and eyes.Too high concentrations in the blood can cause damage to organs of the body. Low
concentrations of urea such as in urine are not dangerous. It has been found that urea can cause
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algal blooms to produce toxins, and urea in runoff from fertilizers may play a role in the increase
of toxic blooms.
First aid (Emergency procedure)
In the event of an emergency, remove the victim from further exposure, send for medical
assistance, and initiate the following emergency procedures:
Skin
Wash exposed area with soap and water. If irritation persists, get medical attention as
soon as possible.
Eyes
Wash eyes with plenty of water for at least 15 minutes, lifting lids occasionally. Seek
Medical Aid.
Inhalation
Remove to fresh air. If not breathing, give artificial respiration. If breathing is difficult,
give oxygen
Ingestion
If swallowed, induce vomiting immediately after giving two glasses of water. Never give
anything by mouth to an unconscious person.
Fire Extinguisher
Any means suitable for extinguishing surrounding fire. Fire extinguisher should available in any
risky places in the plant.
Extinguishing media: CO2, foam, dry powder, water
Handling & Storage
Precautionary Statements
Keep out of reach of children.
Avoid breathing vapors, or dusts.
Wash hands thoroughly after handling.
Do not eat drink or smoke when using this product.
Avoid unintended release to the environment.
Use with adequate ventilation.
Avoid contact with eyes, skin, and clothes.
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Safe Handling
Avoid generating dusts. Use only outdoors or in a well-ventilated area.
Storage
Store in sealed containers in cool, dry, well ventilated place away from incompatible
materials. Wash thoroughly after handling.
Keep container closed.
Transportation
No special transport requirements necessary
Environmental Exposure Limit (EEL): Not assigned
Avoid washing excessive amounts into streams and waterways.
Exposure Controls & Personal Protection
Exposure Standards
Workplace Exposure Standards (WES): Particulates not otherwise classified
Inspirable dust 10mg/m3
Respirable dust 3mg/m3
Personal Protective Equipment
Respiratory: If dusts particles are present wear suitable dust mask.
Eyes/Face: Safety glasses. If dusts present wear goggles.
Skin: use Overalls and gloves.
Eye wash facilities should be available.
Wash hands after working with substance.
Collect and place in clean sealable containers.
Avoid generating dusts.
Engineering Controls
Ventilation: Use in well ventilated area. If dusts are generated use local extraction to control
Disposal Considerations
Observe local authority restrictions that may apply. Collection into sealable
containers and dispose of in an approved land fill. If practicable apply excess fertilizer at
recommended rates to appropriate land. Rinse containers thoroughly prior to re-use. Otherwise
render unusable, and dispose of as waste.
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4.4.2 Safety Factors Relevant to Ammonia
Stability and reactivity
Ammonia has very low stability because it converts to ammonium hydroxide or other
ammonium salt by combining with water or other salts. But it has no reactivity under normal
conditions.
Incompatible materials
Ammonia reacts vigorously with fluorine, chlorine, HCl, HBr, nitrosyl chloride,
chlorine monoxide, aldehydes, boron, boron halides, calcium, amides, chromyl chloride, nitrogen
dioxide, trioxygen difluoride, and nitrogen trichloride , halogens, heavy metals and many other
materials.
Hazardous decomposition products form with hydrogen at very high temperature.
Hazardous polymerization will not occur.
Flammability
Ammonia is slightly flammable material.
Flash point: Not applicable
Flammability limits: Not applicable
Auto-ignition temperature: 1274oF
Hazard identification
Irritating or corrosive to exposed tissues. Inhalation of vapors may result in pulmonary edema
and chemical pneumonitis
Route of entry and health hazards
Harmful if contact with eye
Harmful if inhaled.
Irritant if contact with skin and eye
Eye effects
Mild concentrations of product will cause conjunctivitis. Contact with higher
concentrations of product will cause swelling of the eyes and lesions with a possible
loss of vision.
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Exposure to 50 ppm or less for 5 minutes was not considered irritating by volunteers,
while exposure to 72 ppm was irritating to a few individuals and 134 ppm was irritating and
caused tearing. At 700 ppm, the gas is immediately and severely irritating.
Direct contact with the liquefied gas can cause frostbite and corrosive injury to eye.
Permanent eye damage or blindness could result. Severe, permanent eye injury, including an
almost complete loss of vision, has been reported following direct contact with liquefied
ammonia gas.
Skin effects
Mild concentrations of product will cause dermatitis or conjunctivitis. Contact with
higher concentrations of product will cause caustic-like dermal burns and
inflammation. Toxic level exposure may cause skin lesions resulting in early necrosis
and scarring.
High levels of airborne ammonia gas dissolve in moisture on the skin, forming corrosive
ammonium hydroxide. At 10000 ppm, ammonia is mildly irritating to moist skin. At 20000 ppm,
the effects are more pronounced and 30000 ppm may produce chemical burns with blistering.
These same exposure levels would be almost certainly fatal due to inhalation health effects.
Direct contact with liquefied gas can cause frostbite and corrosive burns. Symptoms
of mild frostbite include numbness, prickling and itching in the affected area. Symptoms of more
severe frostbite include a burning sensation and stiffness of the affected area. The skin may
become waxy white or yellow. Blistering, tissue death and gangrene may also develop in severe
cases. Corrosive burns of the skin have resulted from direct contact with a jet of liquefied
ammonia. Permanent scarring of the skin may result.
Ingestion effects
Since product is a gas at room temperature, ingestion is unlikely.
Inhalation effects
Corrosive and irritating to the upper respiratory system and all mucous type tissue.
Depending on the concentration inhaled, it may cause burning sensations, coughing,
wheezing, shortness of breath, headache, nausea, with eventual collapse.
Toxic effects to the respiratory system, senses, liver, kidneys and bladder observed in
mammalian species from prolonged inhalation exposures at above 100 ppm Inhalation of
excessive amounts affects the upper airway (larynx and bronchi) by causing caustic-like burning
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resulting in edema and chemical pneumonitis. If it enters the deep lung, pulmonary edema will
result. Pulmonary edema and chemical pneumonitis are potentially fatal conditions.
Long term health effects of exposure to Ammonia gas
No significant differences in lung function were observed in workers exposed to 9.2
ppm ammonia for an average of 12.2 years compared to controls with very low exposure (less
than 1 ppm). No conclusions can be drawn from one case report which described lung injury
following long-term exposure to ammonia because the person was a long-term smoker. People
with repeated exposure to ammonia may develop a tolerance (or acclimatization) to the irritating
effects after a few weeks.
First aid (Emergency procedure)
Eyes
Flush contaminated eye(s) with copious quantities of water. Part eyelids to assure
complete flushing. Continue for a minimum of 15 minutes. Persons with potential
exposure to ammonia should not wear contact lenses.
Skin
Remove contaminated clothing as rapidly as possible. Flush affected area with
copious quantities of water. In cases of frostbite or cryogenic "burns" flush area with
lukewarm water. Do not use hot water. A physician should see the patient promptly if
the cryogenic "burn" has resulted in blistering of the dermal surface or deep tissue
freezing.
Ingestion
Not specified. Seek immediate medical attention.
Inhalation
Prompt medical attention is mandatory in all cases of overexposure. Rescue personnel
should be equipped with self-contained breating apparatus. Conscious persons should
be assisted to an uncontaminated area and inhale fresh air. Quick removal from the
contaminated area is most important. Unconscious persons should be moved to an
uncontaminated area, given mouth-to-mouth resuscitation and supplemental oxygen.
Keep victim warm and quiet. Assure that mucus or vomited material does not
obstruct the airway by positional drainage.
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Fire Extinguisher
Extinguisher media
Water fog, foam. Use media suitable for surrounding fire.
Fire extinguished instruction
If possible, stop the flow of gas. Since ammonia is soluble in water, it is the best
extinguishing media not only in extinguishing the fire, but also absorbing the escaped
ammonia gas. Use water spray to cool surrounding containers.
Handling & Storage
Earth-ground and bond all lines and equipment associated with the ammonia system.
Electrical equipment should be non-sparking or explosion proof.
Gaseous or liquid anhydrous ammonia corrodes certain metals at ambient
temperatures. The presence of oxygen enhances the corrosion of ordinary or semi-
alloy steels. The addition of water inhibits this enhancement. Keep anhydrous
ammonia systems scrupulously dry.
Use only in well-ventilated areas. Valve protection caps must remain in place unless
container is secured with valve outlet piped to use point. Do not drag, slide or roll
cylinders. Use a suitable hand truck for cylinder movement. Use a pressure regulator
when connecting cylinder to lower pressure (<500 psig) piping or systems. Do not
heat cylinder by any means to increase the discharge rate of product from the
cylinder. Use a check valve to trap in the discharge line to prevent hazardous back
flow into the cylinder.
Protect cylinders from physical damage. Store in cool, dry, well-ventilated area away
from heavily trafficked areas and emergency exits. Do not allow the temperature
where cylinders are stored to exceed 125oF (52oC). Cylinders should be stored
upright and firmly secured to prevent falling or being knocked over. Full and empty
cylinders should be segregated. Use a "first in-first out" inventory system to prevent
full cylinders from being stored for excessive periods of time.
Never carry a compressed gas cylinder or a container of a gas in cryogenic liquid
form in an enclosed space such as a car trunk, van or station wagon. A leak can result
in a fire, explosion, asphyxiation or a toxic exposure.
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Engineering controls
Use local exhaust ventilation to reduce concentrations to within current exposure limits.
A laboratory type hood is suitable for handling small or limited quantities.
Personal protection
Eye/face protection
Gas tight chemical goggles or full-face piece respirator.
Skin protection
Protective gloves made of any suitable material.
Respiration protection
Respiratory protection with full face piece or self-contained breathing apparatus
should be available for emergency use. Air purifying respirators must be equipped
with suitable cartridges. Do not exceed maximum use concentrations. Do not use air
purifying respirators in oxygen deficient/immediately dangerous to life and health
(IDLH) atmosphere. Consult manufacturer‟s instructions before use.
Other general protections
Safety shoes, safety shower, eyewash "fountain".
Disposal Considerations
Do not attempt to dispose of residual waste or unused quantities. Return in the
shipping container properly labeled, with any valve outlet plugs or caps secured and valve
protection cap in place to BOC Gases or authorized distributor for proper disposal.
4.4.3 Safety Factors Relevant to Ammonium Carbamate
Stability and reactivity
Ammonium carbamate is stable compound, but may be moisture sensitive.
Incompatible with strong oxidizing agents, strong acids, strong bases
Hazardous polymerization will not occur
Decompose to ammonia and carbon dioxide when heated up to 140oF
Incompatible materials
Strong acids. Ammonium carbamate reacts with chlorine, bromine, mercury, silver
and hypochlorite to form explosive compounds.
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Flammability
Ammonium carbamate is not a flammable material
Ammonia vapors in the range of 16% to 25% by volume in air can explode on
contact with an ignition source. The use of welding or flame cutting equipment on process lines
is not recommended unless all ammonium carbamate has been removed. Avoid welding in
confined space.
Flash point: Not applicable
Flammability limits: Not applicable
Auto-ignition temperature: not applicable
Hazard identification
Ammonium carbamate has a potential for acute health effects
Eyes and Skins
Eyes: Noticeable irritation to the eyes will occur at ammonia concentrations of 100
PPM. Severe irritation to the eyes will occur at concentrations of 400 PPM.
Skin: Contact with ammonium carbamate can result in first, second and third degree
burns.
Inhalation
Severe irritation of nose and throat occurs at ammonia concentrations of 400 PPM.
Serious coughing and bronchial spasms occur at ammonia concentrations of 1,700
PPM. Less than a thirty minute exposure to ammonia concentrations of 1,700 PPM
may be fatal. IDLH at 300 PPM.
Ingestion
Ingestion may be fatal. May result in first, second or third degree burns.
First aid (Emergency procedure)
Eyes
Immediately flood with large amounts of water for at least 15 minutes. Seek medical
attention.
Skin
Remove contaminated clothing immediately. Flush the skin with large amounts of
water until all material is removed (at least 15 minutes). Wash all contaminated
clothing before re-use.
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Ingestion
Do not induce vomiting. Encourage the victim to drink large amounts of water,
substituting as available, diluted vinegar, lemon juice or orange juice.
Inhalation
Use respiratory protection as necessary and remove to fresh air at once. If breathing
stops, administer artificial respiration
Fire Extinguisher
Extinguisher media: Water
Avoid direct streams of water application which may result in chemical exposure due
to splashing Fire extinguishing agents to avoid CO2 may react violently.
Use water spray to control ammonia vapors. Adding water to ammonium carbamate
will generate heat and increase the ammonia vapors generated. Wear full protective
clothing with an approved self contained breathing apparatus.
Storage and Handling
Provide ventilation sufficient to maintain exposure to ammonia vapors below the
permissible exposure limit.
Avoid all contact with the body. Minimize gas contact. Employ good maintenance
practices to prevent leaks. Keep away from heat and open flames. Use good process
control measures to prevent releases.
Preferably stored outside. Otherwise in cool, dry well-ventilated non-combustible
location away from all ignition sources and oxidizers.
Exposure Controls/Personal Protection
Engineering Controls
Vessel and drum labels are required on all containers. Personnel training should include
adequate inspection techniques on equipment such as pumps, hoses, and valves.
Eye Protection
Face shield and tight fitting gas tight splash goggles
Protective Clothing
Chemical resistant suit with rubber or vinyl gloves and rubber boots
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Respiratory Protection
Use a NIOSH/MSHA approved full-face negative pressure respirator fitted with
ammonia cartridges for exposures at or below 300 PPM. For concentrations above 300
PPM, use a full-face positive pressure self-contained breathing apparatus
Other Protective Clothing or Equipment
Provide an eyewash station and safety shower at sites handling or storing Ammonium
Carbamate.
Disposal Considerations
Product Disposal
Disposal of ammonium carbamate may be subject to federal, state and local regulations.
General Comments
Handlers of this product should review their operations in terms of applicable laws and
regulations, and then consult with appropriate regulatory agencies before discharging or
disposing of any waste material.
4.4.4 Safety Factors Relevant to Biurete (byproduct)
Stability and reactivity
Product is very stable under normal conditions
Stability is not change with temperature
Stability is not change with varies conditions
Not available incompatibility substances
Non-corrosive in presence of glass.
Polymerization will not occur.
Flammability
Not flammable under normal conditions and may be combustible at high temperature.
Auto-Ignition Temperature: Not available.
Flash Points: Not available.
Flammable Limits: Not available
After the combustion products are carbon oxides (CO, CO2), nitrogen oxides (NO, NO2...).
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Hazard identification
Potential Acute Health Effects:
Hazardous in case of skin contact (irritant), of ingestion, of inhalation. Slightly
hazardous in case of skin contact (permeator), of eye contact (irritant).
Potential Chronic Health Effects:
Hazardous in case of skin contact (irritant), of ingestion, of inhalation.
Slightly hazardous in case of skin contact ( permeator ), of eye contact (irritant).
No carcinogenic effects
No mutagenic effects
No teratogenic effects
First aid (Emergency procedure)
Eye
Check for and remove any contact lenses. In case of contact, immediately flush eyes
with plenty of water for at least 15 minutes. Cold water may be used. Get medical
attention if irritation occurs.
Skin
In case of contact, immediately flush skin with plenty of water. Cover the irritated
skin with an emollient. Remove contaminated clothing and shoes. Cold water may be
used. Wash clothing before reuse. Thoroughly clean shoes before reuse. Get medical
attention.
Serious Skin Contact
Wash with a disinfectant soap and cover the contaminated skin with an anti-bacterial
cream. Seek medical attention.
Inhalation
If inhaled, remove to fresh air. If not breathing, give artificial respiration. If breathing
is difficult, give oxygen. Get medical attention.
Ingestion
Do not induce vomiting unless directed to do so by medical personnel. Never give
anything by mouth to an unconscious person. If large quantities of this material are
swallowed, call a physician immediately. Loosen tight clothing such as a collar, tie,
belt or waistband.
If the contamination is series it should call a doctor immediately
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Fire Extinguisher
Small fire: Use dry chemical powder.
Large fire: Use water spray, fog or foam. Do not use water jet.
Handling and storage
Keep away from heat. Keep away from sources of ignition. Empty containers pose a fire
risk; evaporate the residue under a fume hood. Ground all equipment containing material. Do not
breathe dust. Avoid contact with skin. Wear suitable protective clothing. In case of insufficient
ventilation, wear suitable respiratory equipment. If you feel unwell, seek medical attention and
show the label when possible. Keep container tightly closed. Keep container in a cool, well-
ventilated area.
Exposure Controls & Personal Protection
Engineering Controls
Use process enclosures, local exhaust ventilation, or other engineering controls to keep
airborne levels below recommended exposure limits. If user operations generate dust, fume or
mist, use ventilation to keep exposure to airborne contaminants below the exposure limit.
Personal Protection
Ware safety glasses, Lab coat, Dust respirator. Be sure to use an approved/certified
respirator or equivalent, Gloves.
In large Spill use Splash goggles, Full suit, Dust respirator, Boots, Gloves. A self
contained breathing apparatus should be used to avoid inhalation of the product. Suggested
protective clothing might not be sufficient; consult a specialist before handling this product.
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CHAPTER 5
MASS BALANCE CALCULATION
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5.0 Mass Balance Calculation
5.1 Material Balance
Urea production per day = 1060.0 MT
CO2 conversion = 68.00%
CO2 requirement per day = 777.3 MT
NH3 requirement per day = 600.7 MT
Compound Chemical Formula Molecular Weight (kg/kmol)
Ammonia NH3 17
Carbon dioxide CO2 44
Ammonium Carbamate NH2COONH4 78
Water H2O 18
Urea NH2CONH2 60
Input ratio to reactor NH3 : CO2
Molar ratio 4 : 1
Weight ratio 68 : 44
Reactions involved in the process
2NH3 + CO2 ↔ NH2COONH4 + heat
Sch 2 1 1
Mass 34 44 78
Wt% 0.4359 0.5641 1.0000
NH2COONH4 + heat ↔ NH2CONH2 + H2O
Sch: 1 1 1
Mass 78 60 18
Wt% 1.0000 0.7692 0.2308
Table 5.1 Compound in urea manufacturing
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2NH3 + CO2 ↔ NH2CONH2 + H2O
Sch: 2 1 1 1
Mass 34 44 60 18
Wt% 0.4359 0.5641 0.7692 0.2308
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5.1.1 Reactor
Component
Weight
MT/day Wt %
CO2 263.3 100.00%
Flow rate 263.3 MT/day
Temperature 170 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 4.8 12.79%
CO2 32.4 87.21%
Flow rate 37.2 MT
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 486.1 23.76%
A. Carbamate 1559.7 76.24%
Flow rate 2045.9 MT/day
Temperature 170 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
Urea 1060.0 36.90%
Carbamate 591.0 20.57%
NH3 903.6 31.46%
H2O 318.0 11.07%
Flow rate 2872.6 MT/day
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 600.7 100.00%
Flow rate 600.7 MT/day
Temperature 170 °C
Pressure 175 bar
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MP
STEAM
COND.
5.1.2 Stripper
Component
Weight
MT/day Wt %
CO2 700.0 100.00%
Flow rate 700.0 MT
Temperature 110 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
Urea 1060.0 36.90%
Carbamate 591.0 20.57%
NH3 903.6 31.46%
H2O 318.0 11.07%
Flow rate 2872.6 MT/day
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 612.4 44.89%
CO2 751.8 55.11%
Flow rate 1364.3 MT/day
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
Urea 1060.0 48.00%
Carbamate 499.1 22.60%
NH3 331.3 15.00%
H2O 318.0 14.40%
Flow rate 2208.3 MT/day
Temperature 178 °C
Pressure 175 bar
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SC
STM
5.1.3 Carbamate Condenser
Component
Weight
MT/day Wt %
NH3 612.4 44.89%
CO2 751.8 55.11%
Flow rate 1364.3 MT/day
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 56.4 26.89%
CO2 22.7 10.82%
Carbamate 130.7 62.29%
Flow rate 209.8 MT/day
Temperature 153 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 212.3 28.89%
Carbamate 522.7 71.11%
Flow rate 735.1 MT/day
Temperature 150 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
CO2 263.3 100.00%
Flow rate 263.3 MT
Temperature 170 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
CO2 263.3 14.44%
Carbamate 1559.7 85.56%
Flow rate 1823.0 MT/day
Temperature 170 °C
Pressure 175 bar
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5.1.4 Scrubber
Component
Weight
MT/day Wt %
NH3 1.4 12.79%
CO2 9.7 87.21%
Flow rate 11.2 MT/day
Temperature 189 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 53.1 28.89%
Carbamate 130.7 71.11%
Flow rate 183.8 MT/day
Temperature 150 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 4.8 12.79%
CO2 32.4 87.21%
Flow rate 37.2 MT
Temperature 190 °C
Pressure 175 bar
Component
Weight
MT/day Wt %
NH3 56.4 26.89%
CO2 22.7 10.82%
Carbamate 130.7 62.29%
Flow rate 209.8 MT/day
Temperature 153 °C
Pressure 175 bar
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5.1.5 High Pressure Decomposer
Component
Weight
MT/day Wt %
NH3 327.3 79.49%
CO2 84.5 20.51%
Flow rate 411.7 MT/day
Temperature 157 °C
Pressure 17.5 bar
Component
Weight
MT/day Wt %
Urea 1060 59.00%
Carbamate 349.4 19.45%
NH3 69.3 3.85%
H2O 318.0 17.70%
Flow rate 1796.6 MT/day
Temperature 157 °C
Pressure 17.5 bar
Component
Weight
MT/day Wt %
Urea 1060.0 48.00%
Carbamate 499.1 22.60%
NH3 331.3 15.00%
H2O 318.0 14.40%
Flow rate 2208.3 MT/day
Temperature 178 °C
Pressure 175 bar
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5.1.6 Low Pressure Decomposer
Component
Weight
MT/day Wt %
NH3 221.5 44.67%
CO2 274.4 55.33%
Flow rate 495.9 MT/day
Temperature 129 °C
Pressure 2.5 bar
Component
Weight
MT/day Wt %
Urea 1060 59.00%
Carbamate 349.4 19.45%
NH3 69.3 3.85%
H2O 318.0 17.70%
Flow rate 1796.6 MT/day
Temperature 157 °C
Pressure 17.5 bar
Component
Weight
MT/day Wt %
H2O 20 94.79%
Urea 0.6 2.84%
NH3 0.5 2.37%
Flow rate 21.1 MT/day
Temperature 129 °C
Pressure 2.6 bar
Component
Weight
MT/day Wt %
Urea 1060.6 75.81%
H2O 338.0 24.16%
NH3 0.5 0.04%
Flow rate 1399.1 MT/day
Temperature 129 °C
Pressure 2.5 bar
Component
Weight
MT/day Wt %
CO2 77.3 100.00%
Flow rate 77.3 MT
Temperature 80 °C
Pressure 20 bar
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5.1.7 Low Pressure Absorber
Component
Weight
MT/day Wt %
NH3 221.5 44.67%
CO2 274.4 55.33%
Flow rate 495.9 MT/day
Temperature 129 °C
Pressure 2.5 bar
Component
Weight
MT/day Wt %
NH3 9.5 1.91%
Carbamate 486.4 98.09%
Flow rate 495.9 MT/day
Temperature 129 °C
Pressure 1.5 bar
CW
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5.1.8 Medium Pressure Absorber
Component
Weight
MT/day Wt %
NH3 328.7 77.73%
CO2 94.2 22.27%
Flow rate 422.9 MT/day
Temperature 151 °C
Pressure 17.5 bar
Component
Weight
MT/day Wt %
NH3 265.4 28.89%
CO2 0.0 0.00%
Carbamate 653.4 71.11%
Flow rate 918.8 MT/day
Temperature 150 °C
Pressure 12 bar
Component
Weight
MT/day Wt %
NH3 9.5 1.91%
Carbamate 486.4 98.09%
Flow rate 495.9 MT/day
Temperature 129 °C
Pressure 17.5 bar
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5.1.9 Flash Separator
Component
Weight
MT/day Wt %
H2O 105.6 99.53%
Urea 0.3 0.28%
NH3 0.2 0.19%
Flow rate 106.1 MT/day
Temperature 190 °C
Pressure 0.55 bar
Component
Weight
MT/day Wt %
Urea 1060.6 75.81%
H2O 338.0 24.16%
NH3 0.5 0.04%
Flow rate 1399.1 MT/day
Temperature 178 °C
Pressure 2.5 bar Component
Weight
MT/day Wt %
Urea 1060.3 82.00%
H2O 232.4 17.98%
NH3 0.3 0.02%
Flow rate 1293.0 MT/day
Temperature 110 °C
Pressure 0.7 bar
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5.1.10 Lower Separator
Component
Weight
MT/day Wt %
H2O 152.8 99.74%
Urea 0.2 0.13%
NH3 0.2 0.13%
Flow rate 153.2 MT/day
Temperature 110 °C
Pressure 0.55 bar
Component
Weight
MT/day Wt %
Urea 1060.3 82.00%
H2O 232.4 17.98%
NH3 0.3 0.02%
Flow rate 1293.0 MT/day
Temperature 110 °C
Pressure 2 bar
Component
Weight
MT/day Wt %
Urea 1060.1 93.00%
H2O 79.7 6.99%
NH3 0.1 0.01%
Flow rate 1139.9 MT/day
Temperature 110 °C
Pressure 0.7 bar
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5.1.11 Upper Separator
Component
Weight
MT/day Wt %
H2O 71.1 99.72%
Urea 0.1 0.14%
NH3 0.1 0.14%
Flow rate 71.3 MT/day
Temperature 112 °C
Pressure 0.55 bar
Component
Weight
MT/day Wt %
Urea 1060.1 93.00%
H2O 79.7 6.99%
NH3 0.1 0.01%
Flow rate 1139.9 MT/day
Temperature 110 °C
Pressure 2 bar
Component
Weight
MT/day Wt %
Urea 1060.0 99.20%
H2O 8.5 0.80%
Flow rate 1068.5 MT/day
Temperature 112 °C
Pressure 0.8 bar
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5.1.12 Waste Water Treatment Unit
Component
Weight
MT/day Wt %
H2O 105.6 99.53%
Urea 0.3 0.28%
NH3 0.2 0.19%
Flow rate 106.1 MT/day
Temperature 110 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
H2O 223.9 99.73%
Urea 0.3 0.13%
NH3 0.3 0.13%
Flow rate 224.5 MT/day
Temperature 110 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
H2O 309.5 100.00%
Urea 0.0 0.00%
NH3 0.0 0.00%
Flow rate 309.5 MT/day
Temperature 40 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
H2O 20.0 94.79%
Urea 0.6 2.84%
NH3 0.5 2.37%
Flow rate 21.1 MT/day
Temperature 129 °C
Pressure 2.6 bar
Waste Water
Treatment Unit
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GRANULATION
SECTION
5.1.13 Granulator
Component
Weight
MT/day Wt %
Urea 720.8 99.20%
H2O 5.8 0.80%
Flow rate 726.6 MT/day
Temperature 89 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 1060.0 99.20%
H2O 8.5 0.80%
Flow rate 1068.5 MT/day
Temperature 112 °C
Pressure 2 bar
Component
Weight
MT/day Wt %
Urea 31.8 99.20%
H2O 0.3 0.80%
Flow rate 32.1 MT/day
Temperature 52 °C
Pressure 1.5 bar
Component
Weight
MT/day Wt %
Urea 10.6 0.45%
H2O 0.1 0.00%
Air 2356.9 99.55%
Flow rate 2367.6 MT/day
Temperature 55 °C
Pressure 6 bar
Component
Weight
MT/day Wt %
Urea 1802.0 99.20%
H2O 14.5 0.80%
Flow rate 1816.5 MT/day
Temperature 90 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Air 2356.89 100.00%
Flow rate 2356.89 MT/day
Temperature 35 °C
Pressure 6 bar
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5.1.14 Screen
Component
Weight
MT/day Wt %
Urea 1802.0 99.20%
H2O 14.5 0.80%
Flow rate 1816.5 MT/day
Temperature 89.5 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 477.0 99.20%
H2O 3.8 0.80%
Flow rate 480.8 MT/day
Temperature 89.5 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 1081.2 99.20%
H2O 8.7 0.80%
Flow rate 1089.9 MT/day
Temperature 89.5 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 243.8 99.20%
H2O 2.0 0.80%
Flow rate 245.8 MT/day
Temperature 89.5 °C
Pressure 1 bar
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5.1.15 Product Cooler
Component
Weight
MT/day Wt %
Urea 1081.2 99.20%
H2O 8.7 0.80%
Flow rate 1089.9 MT/day
Temperature 89 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 1060.0 99.20%
H2O 8.5 0.80%
Flow rate 1068.5 MT/day
Temperature 60 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 21.2 0.34%
H2O 0.2 0.00%
Air 6213.6 99.66%
Flow rate 6235.0 MT/day
Temperature 45 °C
Pressure 6 bar
Component
Weight
MT/day Wt %
Air 6213.62 100.00%
Flow rate 6213.62 MT/day
Temperature 35 °C
Pressure 6 bar
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5.1.16 Bag Filter
Component
Weight
MT/day Wt %
Urea 31.8 0.37%
H2O 0.3 0.00%
Air 8570.5 99.63%
Flow rate 8602.6 MT/day
Temperature 52 °C
Pressure 6 bar
Component
Weight
MT/day Wt %
Air 8570.5 100.00%
Flow rate 8570.5 MT/day
Temperature 52 °C
Pressure 1 bar
Component
Weight
MT/day Wt %
Urea 31.8 99.07%
H2O 0.3 0.93%
Flow rate 32.1 MT/day
Temperature 52 °C
Pressure 1 bar
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CHAPTER 6
MATERIAL FLOW SHEET
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Material Flow Sheet
Figure 6.1 Material Flow Sheet
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CHAPTER 7
HEAT BALANCE CALCULATION
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7.0 Heat Balance Calculation
7.1 Main Process Energy Balance
2 NH3 + CO2 NH2COONH4 + HEAT -84 KJ/mol
NH2COONH4 + HEAT NH2CONH2 + H2O +23 KJ/mol
2NH3 + CO2 NH2CONH2 + H2O -60 KJ/mol
Ammonia Liquid
T (ºC) 60 80 112
Cp (KJ/KgK) 5.6 5.87 8.6
Ammonia Vapour
T (ºC) 87 127 167 207
Cp (KJ/KgK) 2.2 2.3 2.37 2.44
CO2(g)
T (ºC) 27 127 227
Cp (KJ/KgK) 0.84 0.94 1.01
Urea Vapour
T (0C) 80 120 200
Cp (KJ/KgK) 1.26 1.36 1.56
Urea Liquid
T (0C) 80 120 200
Cp (KJ/KgK) 1.4 1.6 2.1
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Urea Solid
T (0C) 27 77 127
Cp (KJ/KgK) 1.56 1.8 2.04
Water Liquid
T (0C) 27 127 177
Cp (KJ/KgK) 4.18 4.26 4.39
Cp of the Carbamate = 2.3 KJ/KgK
For NH3 liquid
Cp = a + bT + cT2
5.6 = a + 333b + 3332c (1)
5.87 = a + 353b + 3532c (2)
8.6 = a + 385b + 3852c (3)
From (1), (2) & (3)
a = 163.44 b = - 0.9338 c = 1.38*10-3
For NH3 gas
Cp = a + bT + cT2
2.2 = a + 360b + 3602c (4)
2.3 = a + 400b + 4002c (5)
2.44 = a + 480b + 4802c (6)
From (4), (5) & (6)
a = 0.4 b = 7.25*10-3
c = -6.25*10-6
For CO2 gas
Cp = a + bT + cT2
0.84 = a + 300b + 3002c (7)
0.94 = a + 400b + 4002c (8)
1.01 = a + 500b + 5002c (9)
From (7), (8) & (9)
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a = 0.36 b = 2.05*10-3
c = -1.5*10-6
For Urea
Cp = a + bT + cT2
1.4 = a + 353b + 3532c (10)
1.6 = a + 393b + 3932c (11)
2.1 = a + 473b + 4732c (12)
From (10), (11) & (12)
a = 1.08 b = -2.77*10-3
c = 1.04*10-5
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7.1.1 Reactor
Low pressure steam load at 5 bar pressure and 151.8 ºC for ammonia heating
/day
Medium pressure steam load at 13 bar and 191.6 ºC for ammonia heating
Q1
Q2 130 ºC
34 ºC
170 ºC
190 ºC
170 ºC
170 ºC
190 ºC
MPS
LPS
MPS
COND.
198.3°C
198.3°C
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Urea formation heat by decomposing Ammonium Carbamate
Ammonium Carbamate production in the reactor
Ammonium Carbamate formation heat
Heat required for increasing raw materials to 190 ºC
Energy required to reactor
Medium pressure steam load at 15 bar and 198.3ºC for reactor heating
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7.1.2 Stripper
Decomposition energy of Ammonium Carbamate
Heat released from Urea
Heat released from Ammonium Carbamate
Heat released from Water
MP
STEAM
COND.
178°C
190 °C
190°C
198.3 °C
110 °C
198.3 °C
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Heat absorbed by Carbon Dioxide
Heat absorbed for Ammonia vaporization
Energy required for stripper
Medium pressure steam load at 13bar and 191.6 ºC for heating
7.1.3 Scrubber
153 °C 190 °C
189 °C
150 °C
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Heat released from up flow
Heat released from down flow
Heat absorbed by Ammonia and Ammonium Carbamate
Energy loss
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SC
STM
7.1.4 Carbamate Condenser
Formation energy of Ammonium Carbamate at 170 C
Heat absorbed by Ammonium Carbamate
Heat absorbed by Carbon Dioxide
170 °C
190 °C
170 °C
150 °C
153 °C
145 °C
151.8 °C
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Heat absorbed by Ammonia
Condensation heat and sensible heat released by Ammonia
Heat released by Carbon Dioxide
Heat released from Carbamate condenser
Production of steam load at 5bar
Assume Cp of water at 145 C-150 C = 4.27 kJ/kg
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7.1.5 High pressure decomposer
Decomposition energy of Ammonium Carbamate
Heat released from Urea
Heat released from Ammonium Carbamate
Heat released from Water
178 °C
157 °C
157 °C
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Heat released by Ammonia
Heat absorbed for Ammonia vaporization
Energy loss
7.1.6 Low pressure decomposer
129 °C
129 °C
129 °C
157 °C
80°C
COND.
151.8
°C
151.8 °C
LPS
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Decomposition energy of Ammonium Carbamate
Heat absorbed for Ammonia vaporization
Heat released from Urea
Heat released from Water
Condensation heat released by water vapour from WWTU
Heat absorbed by Carbon Dioxide
Heat released by Ammonia
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Heat released by Carbon Dioxide
Energy required to reactor
Medium pressure steam load at 13 bar and 191.8 ºC for heating
Low pressure steam load at 5 bar and 151.8 ºC for heating
7.1.7 Low pressure absorber
Formation energy of Ammonium Carbamate at 129 C
CW
129 °C
129 °C
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Condensation heat released by Ammonia
Heat released from LP Absorber
Cooling water requirement
7.1.8 High pressure absorber
Operating temperature calculation
157 °C
129 °C
150 °C
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Formation energy of Ammonium Carbamate at 151 C
Condensation heat released by Ammonia
Energy loss due to reduce temperature
Energy released from HP Absorber
Heat released to heat output from LPD
Heat released to cooling water
Cooling water requirement
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7.1.9 Flash separator
Heat released from Urea
Heat released from water
Heat absorbed by water vaporization
Heat loss
Heat required for slurry heat to 178 C
110 °C
178 °C
Urea slurry
110 °C
191.8
°C MPS
140°C
150 °C
129°C
COND.
191.8
°C
150 °C
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Heat recovered from MP Absorber
Additional heat required by 13bar MP steam
MP steam load
7.1.10 Lower separator
Heat absorbed by water vaporization
Energy loss
110 °C
151.8 °C
COND.
LPS
110°C
110 °C
151.8 °C
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Total energy requirement
5bar LP steam load
7.1.11 Upper separator
Heat absorbed by water vaporization
Heat absorbed by urea and water
112 °C
151.8 °C
COND.
LPS
112 °C
110 °C
151.8 °C
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Energy loss
Total energy requirement
5bar LP steam load
7.1.12 Process wastewater treatment unit
Heat requirement of WWTU
Low pressure steam load at 5 bar and 151.8 ºC for heating
Cooling heat of process wastewater from flash separator
Cooling water load
Cooling heat of process wastewater from lower and upper separator
Cooling water load
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7.2 Granulation Plant
7.2.1 Granulator
Heat removed from granulator
6 bar cooling Air load
7.2.2 Product cooler
Heat removed from Product cooler
6 bar cooling Air load
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CHAPTER 8
TABULATED HEAT BALANCE
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8.0 Tabulated heat balance
8.1 Tabulated Heat Balance
Input Energy MJ/day
Heating of Ammonia due to low pressure steam 471962.08
Heating of Ammonia due to high pressure steam 300428.45
Heat supplied to Reactor 899260.67
Heat supplied to Stripper 123475.64
Heat supplied to LPD by low pressure steam 104259.64
Heat supplied to LPD by high pressure steam 97492.80
Heat supplied to Flash Separator 172190.9
Heat supplied to Lower Separator 416783.04
Heat supplied to Upper separator 199581.49
Heat supplied to Wastewater Treatment Plant 63000.50
Total input energy 2848435.21
Output Energy MJ/day
Heat out from Scrubber 124.70
Heat out from Carbamate condenser 1255586.69
Heat out from HPD 6596.25
Heat out from LP Absorber 570330.38
Heat out from HP Absorber 251197.87
Heat out from Wastewater cooling 1 255948.00
Heat out from Wastewater cooling 2 512283.2
Heat out from Granulator 47434.75
Heat out from Product Cooler 62527.63
Total output energy 2962029.47
Table 8.1 Tabulated Heat Balance
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Difference between input and output energy = 113594.26 MJ/day
Total heat output greater than the total heat input. So this difference is due to
heat generated in the reaction. But the amount of theoretical heat generated in the reaction
is much higher than this value. That difference between actual and theoretical value
happens because of the heat losses occurred during the process.
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Comprehensive design project 109
REFERENCES
Book References
Urea manufacturing processes in Ullmann's Encyclopedia of Industrial Chemistry, 5th
Edition, Volume A27
Perry's Chemical Engineers' Handbook - Perry, R.H. and Green, D.W. (Editors)
MARTYN S. RAY; DAVID W. JOHNSTON - Chemical Engineering Design Project: A
Case Study Approach
World Wide Web references
Ammonia and Urea Production -
http://www.nzic.org.nz/ChemProcesses/production/1A.pdf
Urea - http://www.stamicarbon.com/urea/_en/index.htm
Urea - www.epa.gov/ttn/chief/ap42/ch08/final/c08s02.pdf
Urea Production and Manufacturing process
www.icis.com/v2/chemicals/9076560/urea/process.html
Urea – Wikipedia, the free encyclopedia - en.wikipedia.org/wiki/Urea
Fertilizer Urea - www.extension.umn.edu/distribution/cropsystems/DC0636.html
UREA - www.jtbaker.com/msds/englishhtml/u4725.htm
Urea - www.3rd1000.com/urea/urea.htm
MSDS safety data sheets for ammonium carbamate, urea, and ammonium from
http://msds.chem.ox.ac.uk/
MSDS urea - http://www.sciencestuff.com/msds/C2950.html - Science Stuff Inc.,1104
Newport Ave, Austin, TX, USA
MSDS urea - http://www.pusri.co.id/data/MSDS-urea.PDF
E-book References
The Environmental Impact of a Stamicarbon 2000 mtpd Urea Plant - Authors: Will
Lemmen (Licensing Manager) and Hans van Baal (Licensing Manager)
Latest Urea Technology for Improving Performance and Product Quality by EIJI
SAKATA (Senior Process Engineer),TAKAHIRO YANAGAWA (PROCESS ENGINEER) ---
TOYO ENGINEERING CORPORATION , TOKYO JAPAN
Escalating worldwide use of urea – a global change contributing to coastal
eutrophication by PATRICIA M. GLIBERT, JOHN HARRISON, CYNTHIA HEIL and
SYBIL SEITZINGER
NH3
TCW
c
g
e
Steam
Cond.
h
TCW
i
CW
j
Steam
Cond.
k
l
m
Water
Urea melt to granulation
CO2
a
b
d
a) CO2 compressorb) Hydrogen removal reactorc) Urea reactord) High-pressure strippere) High-pressure carbamate condenserf) High-pressure scrubberg) Low-pressure absorberh) Low-pressure decomposer and rectifieri) Pre-evaporatorj) Low-pressure carbamate condenserk) Evaporatorl) Vacuum condensation sectionm) Process condensate treatmentCW - Cooling waterTCW - Tempered cooling water
Stamicarbon CO2 - Stripping Urea Process
ff
Steam
Cond.
NH3
CO2
Water
Air
Urea
a
b
cd
e
f
g h
i
j
Convectional Urea Plant
a) CO2 compressor; b) High pressure ammonia pump; c) Urea reactor; d) Medium-pressure decomposer;e) Ammonia carbamate separation column; f) Low-pressure decomposer; g) Evaporator; h) Prilling;
i) Desorber (waste water stripper); j) Vacuum condensation section
Garden
Administration section
Process area
Granualization area
Cooling tower
Ammonia storage
tank
CO2 Storage
tank
Urea store house
Waste water treatment plant
Cooling towerWater tank
Fuel tanks
Gua
rd ro
om
pond
Gua
rd ro
om
REACTOR
SCRUBBER
CARBAMATE CONDENSER
STRIPPER
LPD
HPD
COMPRESSOR
NH3
CO2
MP STEAM
COND.
UREA GRANULES
AIR
AIR
GRANULATION SECTION
SURFACE CONDENCER
SC
STM
HPABSORBER
FLASH SEPARATOR
LP ABSORBER
LOWERSEPARATOR
UPPERSEPARATOR
STM
SC
CW
CWUPC
PC STRIPPER
HYDROLYSER
Clean gas out
BAG FILTER
MP steam
LP steam
CW
CW
NH3 CO2
MP STEAM
COND.
UREA GRANULES
AIR
GRANULATION SECTION
SURFACE CONDENCER
SC
STM
HPABSORBER
FLASH SEPARATOR
LP ABSORBER
LOWERSEPARATOR
UPPERSEPARATOR
CW
CW
Waste water
PC STRIPPER
HYDROLYSER
P
COMPRESSOR
MP steam
LP steam
Clean gas out
BAG FILTER
STRIPPER
Feed Water
FIRE TUBE BOILER
CO2
CW
CW
CONDENSED WATER TANKS
COOLING TOWER
POND
T
T
T
T
WATER
T
T
T
TT
T
T
T
Urea flow linesother process linesSteam lineCondensed water lineCooling water line
MT/day Wt %1802 99.20%
Componeng
MT/day Wt % 14.5 0.80%g
MT/day Wt %
NH3 1.4 12.79% 1816.5 MT/day 31.8 99.20%Weight MT/day Wt %
CO2 9.7 87.21%Weight MT/day Wt %
Weight MT/day Wt % 90 °C 0.3 0.80% 31.8 0.37%
Flow rate 11.2 MT/day 1060.6 75.81% 1060.3 82.00% Pressure 1 bar 32.1 MT/day 0.3 0.00%Temperatu 189 °C 338 24.16% 232.4 17.98% 52 °C 8570.5 99.63%
Pressure 175 barWeight MT/day Wt % 0.5 0.04% 0.3 0.02% Pressure 1.5 bar 8602.6 MT/day
327.3 79.49% 1399.1 MT/day 1293 MT/day 52 °C84.5 20.51% 129 °C 110 °C Pressure 6 bar
Flow rate 411.7 MT/day Pressure 2.5 bar Pressure 0.7 bar157 °C
ComponenWeight Wt % Pressure 17.5 bar Weight Wt %NH3 53.1 28.89% 1060 99.20%
Component Weight Wt % Carbamate 130.7 71.11% 8.5 0.80% Weight Wt %
UreaH2O
NH3ComponentNH3
CO2
Temperature
Component
UreaH2O
NH3
Flow rateTemperature
Flow rateTemperature
Component
ComponentUreaH2O Component
Component
Urea
H2O
Flow rateTemperature
Flow rateTemperature
Urea
H2O
Flow rate
Temperature
Component
Component
Urea
H2OAir
SCRUBBER
FLASHSEPARATOR
GRANULATOR
BAG FILTER
CO2 263.3 100.00% Flow rate 183.8 MT/day 1068.5 MT/day 720.8 99.20%Flow rate 263.3 MT/day Temperatu 150 °C 112 °C 5.8 0.80%Temperature 170 °C Pressure 175 bar Pressure 2 bar 726.6 MT/day
Pressure 175 barWeight MT/day Wt % 89 °C
ComponenWeight MT/day Wt % 1060 59.00% Pressure 1 bar
NH3 212.3 28.89% MT/day Wt % 349.4 19.45% MT/day Wt %Weight Wt % Carbamate 522.7 71.11% Urea 1060 48.00% 69.3 3.85% 1060.1 93.00%
4.8 12.79% Flow rate 735.1 MT/day 499.1 22.60% 318 17.70% 79.7 6.99%Weight MT/day Wt %
Weight MT/day Wt %
32.4 87.21% Weight Wt % Temperatu 150 °C NH3 331.3 15.00% 1796.6 MT/day 0.1 0.01% 10.6 0.45% 21.2 0.34%37.2 MT CO2 263.3 100.00% Pressure 175 bar H2O 318 14.40% 157 °C 1139.9 MT/day 0.1 0.00% 0.2 0.00%190 °C Flow rate 263.3 MT/day 2208.3 MT/day Pressure 17.5 bar Temperature 110 °C 2356.9 99.55% 6213.6 99.66%175 bar 170 °C 178 °C Pressure 0.7 bar 2367.6 MT/day 6235 MT/day
175 bar 175 bar 55 °C 45 °CPressure 6 bar Pressure 6 bar
Weight MT/day Wt %
MT/day Wt % MT/day Wt % 1081.2 99.20%NH3 486.1 23.76% ComponenWeight Wt % Weight Wt % 1060.6 75.81% 8.7 0.80%
1559.7 76.24% NH3 612.4 44.89% 9.5 1.91% 338 24.16% 1089.9 MT/dayFlow rate 2045.9 MT/day CO2 751.8 55.11% 486.4 98.09% 0.5 0.04% 89 °C
Component
NH3CO2
Flow rateTemperature
Pressure
Component
TemperaturePressure
Component
A. Carbamate
Temperature
Carbamate
Flow rateTemperaturePressure
Component
UreaCarbamate NH3
H2OFlow rate
Component ComponentUrea
H2O
ComponentNH3
Carbamate
ComponentUreaH2ONH3
Flow rateTemperature
NH3
Flow rate
UreaH2OFlow rate
Temperature
ComponentUreaH2OAirFlow rateTemperature
ComponentUreaH2OAirFlow rateTemperature
ComponentUreaH2OFlow rateTemperature
CARBAMATECONDENSER
LPD
HPD
UPPER SEPARATO
R
LOWER SEPARATOR
SCREEN
PRODUCT
COOLER
Flow rate 2045.9 MT/day 2 751.8 55.11% 486.4 98.09% 0.5 0.04% 89 C170 °C Flow rate 1364.3 MT/day 495.9 MT/day 1399.1 MT/day Pressure 1 bar
175 bar Temperatu 190 °C 129 °C 129 °CWeight MT/day Wt % Component
Weight MT/day
Pressure 175 bar Pressure 1.5 bar Pressure 2.5 bar 20 94.79% Urea 10600.6 2.84% H2O 8.50.5 2.37% Flow rate 1068.5
21.1 MT/day Temperature 60129 °C Pressure 1
Pressure 2.6 bar
ComponentWeight MT/day Wt %
Urea 1060 36.90%Component Weight Wt % Carbamate 591 20.57%NH3 600.7 100.00% NH3 903.6 31.46%
Flow rate 600.7 MT/day H2O 318 11.07%Weight MT/day Wt %
Weight MT/day Wt %
Temperature 170 °C Flow rate 2872.6 MT/dayWeight MT/day Wt % 223.9 99.73% 309.5 100.00%
175 bar 190 °C CO2 263.3 100.00% 0.3 0.13% 0 0.00%
175 bar Flow rate 263.3 MT/dayWeight MT/day Wt % 0.3 0.13% 0 0.00%
170 °C 105.6 99.53% 224.5 MT/day 309.5 MT/dayht
Pressure
Wt %99.20%0.80%
MT/day°Cbar
Component
Temperature
Temperature
Pressure
Temperature
Pressure
Flow rate
Temperature
CarbamateFlow rate
Temperature
NH3
Component
H2OUrea
NH3
Flow rateComponentH2O Flow rate
Flow rateTemperature
Component
H2OUrea
NH3
ComponentH2OUreaNH3
TemperatureREACTOR
STRIPPERHP
ABSORBER
LP ABSORBER
175 barht MT/d Wt % 0.3 0.28% 110 °C 40 °C
CO2 77.3 100.00% 0.2 0.19% Pressure 1 bar Pressure 1 barFlow rate 77.3 MT 106.1 MT/day
80 °C 110 °C20 bar Pressure 1 bar
Component
Temperature
Pressure
Pressure
NH3
Flow rateTemperature
TemperatureUrea TemperatureWWTP UNIT
CO2
COMPRESSOR