ATRAINING REPORTONSTEAM GENERATION & AMMONIA PLANT

NATIONAL FERTILIZER LIMITED

Submitted by:YUDHVIR SINGH AHLAWAT13001005057

Department of Chemical EngineeringDeenbandhu Chhotu Ram University of Science & TechnologyMurthal, Sonipat 131039 (Haryana)June 1 July 11, 2015

ACKNOWLEDGEMENT

I am glad to inform you that I have been provided with a golden opportunity to get my practical training in National Fertilizers Limited, Panipat, Haryana and I express my deep sense of indebtedness to Dr.D.P.Tiwari (Head of Chemical Engg. Department, DCRUST, Murthal, Sonipat), Training & Placement Cell and to all officers who made me to get imparted with valuable knowledge during the training period from 1 June 2015 to 11 July 2015.I am very thankful to all officers of steam generation & ammonia plant who helped me directly or indirectly during my training at NFL, Panipat.

Yudhvir Singh Ahlawat13001005057

ABSTRACT

The training report of the working in NFL, PANIPAT is the part of professional training done after B.TECH 2nd year. The report is completely based on the generation of steam & working of Ammonia Plant. In the report the explanation of every process is given. In the Ammonia Plant our main aim is to produce Ammonia which can be supplied to UREA Plant for the manufacture of UREA. In the plant, Ammonia is produced by HABERs process. The molecular formula of Ammonia is NH3 which means we require one molecule of N2 and three molecules of H2 to produce two Ammonia molecule.For Ammonia synthesis, the required nitrogen is obtained from the atmospheric air through Air Separation Unit and during this process we also get O2 which is used for the partial oxidation of Natural Gas in the shell gasification section then the gases evolved are taken to the desulfurization section where H2s is removed and then remaining gases are send to Shift Conversion Process to obtain CO2 from CO. Now this generated CO2 is removed in the decarbonation section for the use in Urea plant. Now the gases are sent to Nitrogen wash unit from which these finally reaches to Ammonia Synthesis Section where AMMONIA is produced.This project report comprises of my 04 weeks industrial training here at NFL Panipat. The vocational training was divided into two sections. For the first two weeks my training was done at Ammonia Plant of NFL and for the remaining time the training was done at Urea Plant.This report consists of brief introduction of the plant, the synthesis of various chemicals and their usage in plant as well as for various purposes. I would like to thank the staff here appointed for their commendable help in each and every stage of my training. I learnt a lot from them. My training became successful because of them.

CONTENTSS.No.TitlePage no.AcknowledgementiAbstract ii1. THE COMPANY 12. PANIPAT UNIT 13. STEAM GENERATION PLANT 24. AMMONIA & UREA PRODUCTION 65. AMMONIA PLANT 76. DETAILED PROCESS DESCRIPTION 97. RAW MATERIALS REQUIRED108. HYRDROGEN PRODUCTION119. DESULFURISATION1110. REFORMER1111. NITROGEN ADDITION1212. REMOVAL OF CARBON MONOXIDE1313. WATER REMOVAL1314. REMOVAL OF CARBON OXIDES1315. SYNTHESIS OF AMMONIA1316. CATALYST USED IN NFL, PANIPAT1517. AMMONIA STORAGE (HORTON SPHERES)1618. UTILITIES1719. THE ROLE OF THE LABORATORY1720. ENVIRONMENTAL IMPLICATIONS1821. ENVIRONMENT CONTROL1822. SAFETY & PRECAUTIONS1923. FIRE PROTECTION2124. CONCLUSION22 References

1. NATIONAL FERTILIZERS LIMITED National Fertilizers Limited(NFL) is a majorIndian producer of inorganic and organic fertilizersand industrial chemicals. National Fertilizers Limited was established in August, 1974 to set up two Fuel Oil based plants Bhatinda (Punjab) and Panipat (Haryana). Both of them were commissioned in 1979. The Nangal Fertilizer Plant of Fertilizer Corporation of India (FCI) IN 1978 on the reorganization of FCI and NFL group of companies. Later, NFL executed the countrys 1st inland gas based plant at Vijaipur (MP) on HBJ gas pipeline. Vijaipur plant had gone in commercial production in July, 1988. Subsequently, expansion was undertaken in 1997 for doubling the capacity of Vijaipur Unit.

2. NATIONAL FERTILIZERS LIMITED-PANIPATThe Panipat project was approved by the Govt. of India on 10th February, 1975 for implementation. Prime consultants for design, engineering, erection and commissioning of plants were M/s Toyo Engineering Corporation of Japan and M/s Engineers of India Ltd. From the zero date 30.04.75, the feed in was achieved 0n 01.09.78 i.e. within 40 months of the zero date. The unit went in commercial production from 01.09.79. The total cost of project was rupees 221.33 crores The performance of the unit in all areas has also been widely acknowledged. It has won number of awards and recognitions in the fields of production, productivity, safety, welfare, innovation, environment protection, skill etc. the unit is also well known for its commitment towards environment protection and social welfare in the design.Brand name of product is Kisan Urea.Capacity of NH3 plant is 900 METRIC TPDCapacity of NH2CONH2 is 1550 METRIC TPD

3. STEAM GENERATION PLANT

INTRODUCTION

The Steam Generation Plant comprises of three identical pulverized coal fired boilers with oil support, having a maximum continuous rating (MCR) of 150 T/Hr steam at a pressure of Kgs/cm2g and 4950C. The normal rate of steam generation (NCR) is 84T/Hr. The boilers are tangentially fired, balanced draught, Natural circulation, radiant dry bottom and provided with bow mills.

MAJOR EQUIPMENT:

Bowl Bills- 3 Nos per boller.Fuel firing systemFurnance Ash hopperFurnance chamberForced draft fanInduced draft fanRegenerative type of Air-heaterSteam/air pre-heaterEconomiserElectrostatic Precipitation for fly ashWater drum, steam drum and boiler, tubesSteam desuperheater and super-heaterA common chimney is provided for final disposal of flue gases for all the three boilers.

DESCRIPTION OF THE PROCESS

FEED WATERBoiler feed water at a temperature of 131 0C and a pressure of 141Kg/cm2g is pumped from the Deaerator by boiler feed water pumps AGA-701AB. This feed water passes through a synthesis economizer and goes to boiler house at a temp of 200 0C. It boiler house it is distributed to each boiler through an 8 individual feed water line.FUEL AND ASH: Coal is pulverized in the bowl mill and used as feed for the boilers under normal operation. Ash which is formed as a result of burning of coal is collected in the bottom ash hopper/fly ash hoppers is disposed off through the ash disposal system. Flue gases are discharged out through the chimneys.I.D. FAN & F.D. FAN:Motor driven FD fan ID fan provide a draft for the furnance. FD fan supplies the combustion air to the furnance after heating the air in tee regenerative type air pre-heater. The flue gases are finally disposed off by the ID fan to the atmosphere via chimney.

STEAM SUPPLY AND DISTRIBUTION:Super heated steam at 105 Kg/cm2g and 4950C is produced in boiler. A part of this steam is let down to a pressure of 3 Kgs/cm2g in a de-superheater for use in fuel oil unloading system.Rest of high pressure steam is carried to Ammonia Plant where steam from Ammonia Plant steam superheaters ABA-701 at 103Kg/cm2 and 4950C is also mixed with it and the entire superheater steam is distributed as under:-1.Synth compressor turbine175.O T2.N2 Compressor turbine 80.O T3.O2 Compressor turbine 25.O T4.Air Compressor turbine 58.O TExhaust steam from Air Compressor, Oxygen compressor turbines and condensing turbines of synthesis is compressor is condensed in respective surface condensers and the condensate, thus obtained is sent to the DM/Plant for treatment for re-use as boiler feed water.

The extraction steam from back pressure turbines of synthesis compressor and N2 compressor meets the entire demand for the process plants, utilities and off site area at various pressure levels of 65,40,9 and 3 Kg/cm2g. The requirement of steam at different pressures for various plants are given below:

Sr. No.PlantSteam Pre. & temp.Qty.Source

1.Ammonia65kg/cm2 430oC60.0N2 Compressor

2.Urea40 Kg/cm2/370 oC80.0Syn. Compressor

3.NH3 Compressor40 Kg/cm270.0Syn. Compressor

4.Ammonia9 Kg/cm2/230 oC15.0NH3 Compressor

5.De-aerator3Kg/cm2/187 oC20.0Ammonia

6.FO Storage Tank3Kg/cm2/187 oC8.0NH3 Plant

7.Boiler FO dayTank3Kg/cm2/187 oC0.1-do-

8.LPG Vaporizer3 Kg/cm2/187oC0.1Ammonia

9.Caustic Soda-do-0.2 ----do----

10.Caustic soda Unloading-do-0.7 ----do----

11.Miscellaneous-do-3.0 ----do----

STEAM FOR FURNACE OIL UNLOADINGApart from the steam required for various plants, steam at a pressure of 3 Kg/cm2g is also required for fuel oil unloading facilities. The requirement may fluctuate from O T/hr to 21.7T/hr depending on the ambient conditions, quantity and quality of oil being unloaded.

FUELS COMBUSTION :Each boiler is designed for steaming with two mills supported with FO guns. Pulverized cool is supplied to the furnance at the four corners of the boiler in three elevations A.B and C. Each mill suppliers PF coal in all the four corners of one elevation only. There are two types of FO guns in between elevation AB and BC in all the four corners of the boilers. As such, there are 12 Nos. of pulverized cool burners and 8 Nos of FO guns. There is provision to burn HSD in lower tyre FO guns as and when required.The coal from unloading bay comes to the raw coal bunkers passing through crusher houses conveyed by a system of conveyer belts. Coal coming from raw coal bunkers comes to raw cola feeder and then supplied to the mill Quantity of coal supplied to the mill is controlled by changing the speed of raw coal feeder. This coal is crushed in between bowl and bull ring segments of mill. Hot air is introduced to mill, which is coming from RHS and LHS wind boxes of the boiler. There is provision to supply cold air to maintain the temperature of coal dust and air mixture from 70oC to 90oC. This coal dust and air mixture is passing via classifier vanes and exhauster of the mills, supplied to all the four corners of the boiler furnance through distributor. Size of the coal dust is 200 m of 70% passing Regulating of the fireness of grinding is done by changing the angle of the vanes of classifier of the mill.In order to ensure safety against explosion hazards are provided peepholes in furnace and explosion diaphragms in flue gas path at different placed on flue gas ducts after Air Pre-heater.This cola dust and air mixture burns in the furnace with the support of fuel oil. Adequate quantity of secondary air supplied to the furnace to boost up ignitions by both side wind boxes, regulated by aux.air dampers in each corner. Heat liberated due to combustion of fuel in furnace is absorbed by water walls for steaming inside tube water and remaining heat goes with flue gas for further use. This flue gas heat is used in superheaters to superheat steam temperature in bank tubes and economizer for further heating up water temperature in air pre-heatet to raise the temperature of air coming from FD fans.70 to 80% of the ash particles are driven out with flue gas and remaining are collected in bottom ash hoppers. More than 99% of ash particles are liberated in electro-static precipitators from flue gas. This flue gas, temp, about 140oC goes to chimney through 2 Nos. of ID fans, and then to atmosphere. The ashes of bottom ash hoppers and electrostatic precipitators hoppers transferred to the ash ponds, out side of factory by ashing system equipment.BASIC COMBUSTION REACTIONSCarbon, Hydrogen and Sulphur in the fuel, Combine with oxygen in the air to form CO2, H2O vapours and SO2 and releasing heat as follows:-

--- C+O2 CO2+8014 K.cals/Kg of Carbon--- 2C+O2 2CO+2430 K cals/Kg of Carbon--- 2H2+O2 2H2O+28922K cals/Kg of Hydrogen--- S+O2 SO2+2224 K.cals/kg of SulphurIf excess air is used for combustion, Sulphur trioxide(SO2) may also be formed as combustion product.TURN DOWN RATIO:The relationship between the maximum and minimum fuel input without heating excess air level is called Turn down Ration For example a burner whose maximum input is 250,000K cals and minimum rate is 50,000K, cals has a turn down ration of 5 to 1.

3. AMMONIA AND UREA PRODUCTIONUrea (NH2CONH2) is of great importance to the agriculture industry as a nitrogen- rich fertiliser. In Panipat, National Fertilizer Limited manufacture ammonia and then convert the majority of it into urea. The remainder is sold for industrial use.Ammonia synthesisAmmonia is synthesised from hydrogen (from natural gas) and nitrogen (from the air). Natural gas contains some sulfurous compounds which damage the catalysts used in this process. These are removed by reacting them with zinc oxide, e.g.ZnO + H2S ZnS + H2O The methane from the natural gas is then converted to hydrogen:CH4 + H2O 3H2 + COCH4 + 2H2O 4H2 + CO2CO + H2O H2 + CO2Air is mixed in with the gas stream to give a hydrogen:nitrogen ratio of 3:1.Water, carbon monoxide and carbon dioxide (all of which poison the iron catalyst used in the ammonia synthesis) are removed. The carbon monoxide is converted to carbon dioxide for use in urea production, and the carbon dioxide removed:CO + H2O CO2 + H2The remaining traces of CO and CO2 are converted to methane and then the gases cooled until the water becomes liquid and can be easily removed.The nitrogen and hydrogen are then reacted at high temperature and pressure using an iron catalyst to form ammonia:N2 + 3H22NH3Urea synthesisUrea is made from ammonia and carbon dioxide. The ammonia and carbon dioxide are fed into the reactor at high pressure and temperature, and the urea is formed in a two step reaction2NH3 + CO2NH2COONH4 (ammonium carbamate) NH2COONH4 H2O + NH2CONH2 (urea)The urea contains unreacted NH3 and CO2 and ammonium carbamate. As the pressure is reduced and heat applied the NH2COONH4 decomposes to NH3 and CO2. The ammonia and carbon dioxide are recycled.The urea solution is then concentrated to give 99.6% w/w molten urea, and granulated for use as fertiliser and chemical feedstock.

5. AMMONIA PLANTIntroduction to plant:-AMMONIA: Ammonia is the key intermediate product for manufacture of urea.The primary use of ammonia is the nitrogen source in fertilizers. Until the turn of this century, the nitrogen supply in farm soils was entirely dependent upon natural sources of nitrogen, mainly mineral deposits and animal and vegetable wastes. Most of these were from industries other than agriculture.Today ammonia is primarily produced by the direct synthesis of hydrogen and nitrogen. The manufacturing technology stems from Haber-Bosch process of synthesizing ammonia, commercialized first in 1913.The commercial development of ammonia synthesis is rightly considered as one of the most significant technological advanced benefiting all mankind. For this achievement, Haber & Bosch were awarded noble prize in the year 1818 & 1931.Their achievement makes increased supplies of food available for a growing world population.

Ammonia storage is major potential hazard at NFL Panipat as quantity stored and handled is very high. The spread out ammonia may lead to atmospheric as well as water pollution due to its high solubility in water. It may affect the site as well as population around works. Though ammonia is lighter than air, it forms mixture with air which is heavier than air when stored at conditions of higher pressure and low temperature. Ammonia release can be instantaneous(puff) or continuous or steady(plum).In case of instantaneous, release total material will escape quickly forming flat cylindrical cloud which is then carried down by wind becoming larger and more dilute during its passage by means of air entrainment . In continuous release, gas is released steadily over long period of time Gas cloud forms a plume in which time averaged concentration at given point remains constant throughout duration of release.

CHARACTERISTICS

Color/odor: colorless/pungent TLV (8 hrs. exposure): 25 PPM Explosive Range (%v/v in air): 16-25 Mode of Entrance: inhalation - skin contact

Ammonia is a colorless, alkaline gas, lighter than air and possesses a unique, penetrating odor .The flammable limits of ammonia in air are 16 & 25 volume%, in oxygen the range is 15 to 70 volume%. Ammonia is comparatively stable at ordinary temperatures but decomposes into hydrogen and nitrogen at elevated temperatures. Initially in India, the ammonia was produced only based on coke even gas and electric power. However, we have changed over to other feedstock, namely naphtha, lignite natural gas, coal &Natural Gas. At NFL Panipat, Natural Gas is used as feedstock for making ammonia. At NFL PANIPAT, ammonia is produced as an intermediate product during process of manufacturing urea. Release may occur from pipelines carrying ammonia or storage vessels including Horton spheres. Affected range of ammonia depends on the relative humidity, wind velocity, ambient temperature and quantity of ammonia stored and rate of release. Worst case is during stable atmosphere in which ammonia moves up as vertical column.Process used for manufacture of ammonia is "Partial Oxidation" of Natural Gas with steam and oxygen .Process:- Feedstock is partially oxidized and gasifies with steam and oxygen at 55Kg/cm2G and 1370oC temperatures. Raw gas produced in gasification contains mainly the gases like CO, H2, CO2, H2S and CH4. H2S is removed from gas stream at 48kg/cm2Gpressure and -33oC, by physical absorption in circulating methanol in Rectisol section. The CO from desulfurized gas is converted to CO2& H2 by CO shift reaction at 46kg/cm2Gpressure of Fe catalyst in CO conversion section. The CO2 from shifted gas is physically absorbed in circulating methanol at 42kg/cm2G pressure and -66oC temperatures in second stage of rectisol Section. Decarbonated gas containing small proportions of CO, CO2& CH4 is scrubbed with liquid nitrogen in Nitrogen Wash Unit at -195oC. The gas from NWU is mainly hydrogen and nitrogen. Thereafter, N2 is mixed to maintain H2 to N2 ratio 3:1. Gas is compressed to 220Kg/cm2G and sent to ammonia synthesis converter where ammonia is produced in presence of catalyst at 500oC.

6. Process DescriptionThis report describes the process for plant of National fertilizer Limited(NFL).The name plate capacity of plant is 900 MTPD of Ammonia. The plant is based on steam reforming of natural gas and is located at Panipat,Haryana.The report consists of information on chemical reactions, catalysts and an overview of the process in each of the main sections: Desulphurization Reforming CO conversion CO2 removal Methanation and compression Drying Compression Ammonia synthesis and refrigeration Process condensate strippingTHE AMMONIA MANUFACTURING PROCESSAmmonia is produced in a process known as the Haber process, in which nitrogen and hydrogen react in the presence of an iron catalyst to form ammonia. The hydrogen is formed by reacting natural gas and steam at high temperatures and the nitrogen is supplied from the air1 . Other gases (such as water and carbon dioxide) are removed from the gas stream and the nitrogen and hydrogen passed over an iron catalyst at high temperature and pressure to form the ammonia. The process is shown schematically in Figure 1.

7. RAW MATERIALS REQUIRED

For the production of 900 metric tons/day of ammonia and 1550 metric tons/day of urea, following raw materials are required; Natural Gas 910 metric tons/day COAL 1650 metric tons/day WATER 17 metric tons/day ELECTRICITY 26MWHFeed stock (Natural Gas) is obtained from refineries like IOCL, Panipat and IOCL Mathura.

FIGURE 2: SKECH OF AMMONIA PLANT

8. STEP 1 - HYDROGEN PRODUCTION

9.DESULFURISATION

Hydrogen is produced by the reaction of methane with water. However, before this can be carried out, all sulfurous compounds must be removed from the natural gas to prevent catalyst poisoning. These are removed by heating the gas to 400oC and reacting it with zinc oxide:

ZnO + H2S ZnS + H2O

FIGURE 3: DESULFURISATION SECTION

10. REFORMERFollowing this, the gas is sent to the primary reformer for steam reforming, where super-heated steam is fed into the reformer with the methane. The gas mixture heated with natural gas and purge gas to 770oC in the presence of a nickel catalyst. At this temperature the following equilibrium reactions are driven to the right, converting the methane to hydrogen, carbon dioxide and small quantities of carbon monoxide:CH4 + H2O > 3H2 + COCH4 + 2H2O > 4H2 + CO2CO + H2O > H2 + CO2This gaseous mixture is known as synthesis gas.

FIGURE 4: PRIMARY AND SECONDARY REFORMER

11. STEP 2 - NITROGEN ADDITIONThe synthesis gas is cooled slightly to 735oC. It then flows to the secondary reformer where it is mixed with a calculated amount of air. The highly exothermic reaction between oxygen and methane produces more hydrogen. Important reactions are:CO + H2O > CO2 + H2O2 + 2CH4> 2CO + 4H2O2 + CH4> CO2 + 2H22O2 + CH4> 2H2O + CO2

In addition, the necessary nitrogen is added in the secondary reformer.

As the catalyst that is used to form the ammonia is pure iron, water, carbon dioxide and carbon monoxide must be removed from the gas stream to prevent oxidation of the iron. This is carried out in the next three steps.12. STEP 3 - REMOVAL OF CARBON MONOXIDEHere the carbon monoxide is converted to carbon dioxide (which is used later in the synthesis of urea) in a reaction known as the water gas shift reaction:CO + H2O > CO2 + H2This is achieved in two steps. Firstly, the gas stream is passed over a Cr/Fe3O4 catalyst at 360oC and then over a Cu/ZnO/Cr catalyst at 210oC. The same reaction occurs in both steps, but using the two steps maximises conversion.13. STEP 4 - WATER REMOVALThe gas mixture is further cooled to 40oC, at which temperature the water condenses out and is removed.14. STEP 5 - REMOVAL OF CARBON OXIDESThe gases are then pumped up through a counter-current of UCARSOL solution (an MDEA solution, ). Carbon dioxide is highly soluble in UCARSOL, and more than 99.9% of the CO2 in the mixture dissolves in it. The remaining CO2 (as well as any CO that was not converted to CO2 in Step 3) is converted to methane (methanation) using a Ni/Al2O3 catalyst at 325oC: 2CO + 3H2 > CH4 + H2OCO2 + 4H2> CH4 + 2H2OThe water which is produced in these reactions is removed by condensation at 40oC as above. The carbon dioxide is stripped from the UCARSOL and used in urea manufacture. The UCARSOL is cooled and reused for carbon dioxide removal.15. STEP 6 - SYNTHESIS OF AMMONIAThe gas mixture is now cooled, compressed and fed into the ammonia synthesis loop (see Figure 1). A mixture of ammonia and unreacted gases which have already been around theloop are mixed with the incoming gas stream and cooled to 5oC. The ammonia present is removed and the unreacted gases heated to 400oC at a pressure of 330 barg and passed over an iron catalyst. Under these conditions 26% of the hydrogen and nitrogen are converted to ammonia. The outlet gas from the ammonia converter is cooled from 220oC to 30oC. This cooling process condenses more the half the ammonia, which is then separated out. (These reactions are the reverse of the primary reformer reactions seen in Step 1. The catalyst in both cases is nickel, illustrating the fact that a catalyst accelerates both the forward and back reactions of an equilibrium system. At reforming temperatures (~850oC) the methane is almost completely converted to carbon oxides and hydrogen as the reaction is endothermic and favoured by the high temperature. However, at the much lower temperature used for methanation (~325oC), the equilibrium lies to the right and practically complete conversion of the carbon oxides to methane is obtained.The remaining gas is mixed with more cooled, compressed incoming gas. The reaction occuring in the ammonia converter is:N2 + 3H2> 2NH3The ammonia is rapidly decompressed to 24 barg. At this pressure, impurities such as methane and hydrogen become gases. The gas mixture above the liquid ammonia (which also contains significant levels of ammonia) is removed and sent to the ammonia recovery unit. This is an absorber-stripper system using water as solvent. The remaining gas (purge gas) is used as fuel for the heating of the primary reformer. The pure ammonia remaining is mixed with the pure ammonia from the initial condensation above and is ready for use in urea production, for storage or for direct sale. Ammonia product specifications are given inTable 1 - Composition of the gas stream after each process step

Feed gasStep 1Step 2Step 3*Step 5Ideal

N22.90.821.719.924.725

H268.356.560.17475

CO6.28.90.1

CO24.114.511.818.9

CH483.410.20.70.71.0

Ar0.30.30.3

other9.6

hydrocarbons

Water is not listed among the gases considered because its levels are highly variable. All water is eliminated after step 4.

All figures are given in mol % (i.e. the percentage of the total number of moles of gas present that are due to this gas).

*The gaseous composition after Step 4 is the same as that after Step 3 as Step 4 is simply the removal of water.

Table 2 - Ammonia specifications

ComponentComposition

Ammonia98 % minimum

Moisture1500 g T-1 maximum

Oil85 g T-1 maximum

Iron1.0 g T-1 maximum

16.CATALYST USED IN NFL, PANIPAT11.3.1 Type : KMIRVOLUME 1st BED 7.6m3 2nd BED 16.2m3 Size BED 1.5-3mm11.3.3 Age 1st bed 24 months 2nd bed 84 months Concentration FeO: 31% Fe2O3: 66% K2O: 1% Al2O3: 1.8% Impurity: .2%Catalyst Poisoning O2, CO, CO2, H2O, temperature poisoning Cl2 compounds Arsenic compounds Some heavy metal compounds (permanent poisoning)

At low temperature reaction low, but equilibrium favored At high temperature shifts backward. Optimum temperature increases the life of catalyst .temperature is maintained 10oC higher than the temperature at which reaction stops. Catalyst temperature is controlled by TRC -602(COLD SHOT) and flow of gas by pass valve. Catalyst hot spot temperature limits 522oC. Converter temperature allowed 320oC. Ratio should be maintained 3:1.less than 2.5:1 or greater than 3:1, reaction speed decreases, temperature decreases and pressure of loop increases. Gas must be purged to maintain the ratio. High Inert (>1.26%) increases the loop pressure but effective pressure decreases and reaction velocity decreases. Ammonia concentration at conversion inlet: increase of ammonia concentration in the converter reduces the reaction rate and decrease in concentration increase the rate. Circulating rate: increase of circulating rate reduces the pressure of loop. Pressure: increase in pressure forwards the reaction but pressure increases due to:a) Increase of makeup gasb) Decrease of circulating ratec) Increase of inertd) H2/N2 ratio below 2.5:1 or greater than 3:1e) Reduction of catalyst activityIncrease in pressure due to make up gas favors reaction others do not.17. AMMONIA STORAGE (HORTON SPHERES)Two number of spheres of 1500 MT capacity are provided for ammonia storage but normally not more than 750 MT of ammonia is stored at any time in each of Horton spheres.a. Spheres are sited at a place away from main plant building and can be reached by the vehicles from two directions.b. Spheres have been designed as per standard codes to ensure safety even under extreme conditions.c. Two numbers of adequately designed relief valves with in di visual isolations have been provided on each Horton sphere.d. A 6size vent line remote operated valve has been provided to release any over pressure.e. Two number of refrigeration compressors have been provided.f. Spheres are earthed, insulated and fenced.g. Latest safety provisions have been made in new Horton spheres by providing single nozzle at bottom.h. Continuous ammonia monitoring sensors have been provided at strategic location around both Horton spheres with indication cum alarm in urea control room.i. Excess flow valves have been provided at five locations.

18. UTILITIES

The ammonia manufacturing has its own utilites. These are listed below.Ammonia manufactureHeat recoveryThe heat of the gas from the primary reformer (Step 1) is used to produce steam for the primary reformer using a boiler. The gas is then discharged. Heat from the process gas from the secondary reformer (Step 2) is used to produce steam for a turbogenerator.Water recyclingExcess water from the water gas shift converter, the methanator and the ammonia synthesis loop is used for boiler feed water and as the absorbing water for ammonia recovery.Carbon dioxide stripperThe used UCARSOL is sent to the carbon dioxide stripper. Here the UCARSOL is heated to remove a mixture of CO2 and water, cooled and reused. The water is removed from the CO2 by condensation and the pure CO2 sent directly to the urea plant for compression and use in urea synthesis.Ammonia recoveryGases purged from the ammonia synthesis loop and gases collected during ammonia decompression are mixed and sent to the ammonia recovery system. Here the gas mixture is introduced at the bottom of a column and passes up through a counter-current of cold water. 96% of the ammonia in the gas is absorbed into the water, leaving a gas mixture that is used as a fuel gas to heat the primary reformer. The ammonia is distilled out of the ammonia-water mixture, condensed and pumped to join the rest of the ammonia from the ammonia synthesiser.

19. THE ROLE OF THE LABORATORYIn Ammonia production The laboratory monitors the gaseous mixture exiting each vessel at each stage in the process using gas chromatography. The concentration of each component during the process is kept at a precalculated design figure and laboratory results are compared to these figures. Adjustments are made to the process based on the laboratory results to bring the process back to the design figures. The UCARSOL solution is analysed daily to determine the solution strength. The solution strength must be kept within a defined range and additions to the system are made according to laboratory results. Liquid ammonia product is analysed to ensure that impurity concentrations are below maximum levels set.

20. ENVIRONMENTAL IMPLICATIONSThe ammonia and urea complex is operated in accordance with stringent safety and environmental standards. The National Fertilizer Limited complex produces effluent in the form of storm water and waste water from the manufacturing process. All effluent is directed to large holding ponds where it is treated and carefully checked as to its composition prior to discharge. The effluent is spray irrigated onto National Fertilizer Limiteds pastures surrounding the complex. Many waste minimisation measures are carried out during the process, resulting in the plant having little effect on the environment.

21. ENVIRONMENT CONTROLTo keep the pollutants with in prescribed with in prescribed standard, highly innovative schemes have been adopted right from the design stage itself. Many measures have been taken for controlling pollution of water, air, soil and noise.The liquid effluent is treated by biological treatment, one of the most sophisticated schemes based on latest technology. It is the Asias best treating plant.The treated effluent water is tested every hour to meet ISO:2490 specifications. This water is normally reused for flushing. The ash from boilers sent to the ash pond.Modern sophisticated electrostatic precipitators are employed to remove the find suspended particles from stack gases disposed to atmosphere through a chimney at a height of 80m. For gaseous effluent many tall stacks 50-80m height has been provided to vent the gases high up into the atmosphere, so that ground level concentrations are not affected.The only effluents are treated in oil separators and treated oil is reused in the plant.Oil free water is sent to effluent treatment plant.Even fire urea dust is eliminated from top of 84m high prilling tower by scrubbing it with water,so that urea dust is not allowed to escape the surrounding.Trees have been planted around the plant and township to improve the atmospheric conditions as well as to remove the suspended dust in atmosphere.NFL is still finding out ways and means to reduce the generation of pollutants and improve the efficiency of plants.

22. SAFETY AND PRECAUTIONGENERAL:1. The purpose of these safety instructions is to prevent any possible accident in the urea plant to minimize the damage for employees and plant equipments. So operating personnel should always follow instructions keeping in mind that SAFETY IS THE PRIMARY CONCERN.2. Safety Training Programmes are organised throughout the year to assure safety awareness in the mind of employees. Company provides safety equipments such as breathing apparatus, gas masks, asbestos helmets (fire proof),goggles, gloves, ear plugs etc. free of cost. Safety and fire fighting training is imparted to employees through various techniques. CO and H2S monitoring system have been installed with indication in Ammonia Control Room.3.Wide publicity is given to safety through Safety Committee, Exhibitions, training programs, banners, holding stickers, pep talks etc.4.Due to the cooperation of employees ,the effort of management and the C.I.S.F., the accident rate has been dropped considerably. The unit has been awarded by National Safety Council with three Awards of Honour besides a no. of state national level Awards.

The following rules should be carefully followed as neglect of these may result in damage to personnel/and or equipment. However, attention should be paid to that these rules may not cover all necessary items for safe operation of urea plant.

1. Smoking shall allow only in designated areas. Lighters and matches shall not be carried within an operating plant handling inflammables.2. All personnel must know the location and use of all fire hoses and hydrants. Fire blanks, gas masks and respirators and other protective equipments such as hard hats, rubber gloves.3. Intoxicants of any kind shall not be allowed to bring into or use in the plant.4. Pass only the specified sidewalks in the plant unless necessary.5. Do not walk under cranes, booms, or loads being hosted.6. Do not jump from platforms, ladders etc.7. Operatingequipments should be checked frequently for any leakage, overheating, corrosion etc., so that corrective measures may be taken before these results in any serious damage to personnel and or equipments. Usual conditions should be reported immediately.8. Never disassemble any equipment or piping unless it is sure that no harmful substance such as ammonia etc. is present and it is depressurized.9. Without a work permit, no hot work should be allowed. All conditions should be properly kept seal off leakage of any inflammable material.10. Always flush with water and or steam, whenever flow of urea solution or carbamate solution is interrupted.11. Before starting operation check as to whether all the safety equipments are functioning properly.12. Always observe start-up and safe operating precautions for pumps and compressor as regards safely.13. Always ensure that steam is flowing through jacket tracing of safety valve etc.14. Never run a pump dry. Always keep suction strainer clean and maintain sufficient level in the equipment concerned to pump suction.15. Never stand directly facing safety valves, rupture disc, sight glass sampling valves etc.16. Isolation valve of safety valves are in open conditions.17. Do not allow water containing solid contaminants in system as otherwise they will damage valves and pumps.18. Do not pull vacuum on equipments unless it is design to withstand such a stress set up under such conditions.19. Switch pump regularly when spares are available. This will ensure that spares are ready whenever needed.20. Always wear proper dress while operating any machine.21. Never wear any loose clothes while operating in the plant.22. Never allow water containing more than 50 ppm of chlorine ion to come in contact with stainless steel either inside or outside equipment.23. Check that all the bleed valves are in open conditions.

23. FIRE PROTECTION1. From types extinguishers and water must not be used in fires around electrical equipment, carbon dioxide or dry powder extinguishers may be used safety.2. The carbon tetra chloride extinguishers which liberates poisonous fumes must not be used.3. Carbon dioxide, dry chemical or foam type extinguishers are suitable for oil fires,4. Do not use light distillates such as gasoline or naphtha to clean machinery or for any other cleaning purpose. Use kerosene or heavy oil instead.5. Keep all area free of waste paper and trash, especially oily rags and clothes should not be left in locker or tool boxes.6. Lighting fixtures and electrical equipment should be vapour proof.7. Fire and explosive hazards in urea plant.8. Ammonia is capable of forming flammable and explosive mixtures with air within certain range (16-28% by volume). Such concentrations are seldom encountered in practical handling; accordingly, the relative fire and explosion hazards are small. The presence of oil, or a ammonia with other combustible material will increase the fire hazard. The explosive range of ammonia of broadened by the following factors:9. Admixture of hydrogen or oxygen replacing air.10. Higher temperature and pressure.

24. CONCLUSIONIndustrial training is one of the most important components in the fulfillment of any engineering course conducted at any level and at any college. It is a bold attempt to bridge the gap between the world of work and studies being imparted to students. Training makes the trainee use the theoretical knowledge being imparted in the college for practical purposes. The students are made aware of rapid development taking place in the industrial scenario. It is essential that the students of technical institutes should be as near to the world of work as possible. The main objective of industrial training is to enable the students to:1. Exposure themselves to the industrial environment, which cannot be simulated in the classrooms.1. Apply theoretical knowledge to practical purposes.1. Appreciate the importance of discipline, punctuality, teamwork, sense of responsibility, value of time, money and dignity of labour.Appreciate research and development, innovation and improvement, expansion, diversification and moderation being carried out and planned in the industry

25. BIBLIOGRAPHY NFL manual NFL library

Websites www.google.com www.wikipedia.com ywfdcrustm.blogspot.com

Books Unit operations in chemical engineering (By McCabe & Smith) Unit process (P.H.Groggins) Outline of Chemical technology (By Dryden)

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