1

PLANT DESIGN PROJECT PRODUCTION OF ACETIC ACID AND

METHANOL

GROUP NO 18

SHEET

JOB CODE A

DESIGNER MUHAMAD FAIZ BIN ISHAK

(11151)

DETAILED DESIGN OF

MAJOR EQUIPMENT

METHANOL REACTOR (R-201)

And

DESIGN OF MINOR EQUIPMENT

COMPRESSOR (K-301)

PUMP (P-203)

DOC NO

DESCRIPTION PREPARED

BY REVIEWED

BY DATE

01 GENERAL DESCRIPTION MF 21/4/12

02 PROCESS DESIGN MF 21/4/12

03 MECHANICAL DESIGN MF 21/4/12

04 SPECIFICATION SHEET AND DRAWING MF 21/4/12

05 COSTING MF 21/4/12

06 OPERATING MANUAL MF 21/4/12

07 MINOR EQUIPMENT DESIGN 1 MF 21/4/12

08 MINOR EQUIPMENT DESIGN 2 MF 21/4/12

INFORMATION CONTAINED IS OUR PROPERTY AND MUST NOT BE USED BY OR CONVEYED TO ANY PERSON WITHOUT AUTHORITY

2

TABLE OF CONTENT

1. GENERAL DESCRIPTION 6

1.1. INTRODUCTION 6

1.2. DESIGN METHODOLOGY 6

1.3. FEEDSTOCK, REACTION AND RATE OF REACTION 8

1.4. REACTOR SELECTION 9

1.5. THERMAL AND BED ARRANGEMENT 12

2. PROCESS DESIGN 14

2.1. OPERATING CONDITIONS 14

2.2. REACTOR VOLUME DETERMINATION 17

2.3. CATALYST 22

2.4. TUBE SELECTION 22

2.5. NUMBER OF TUBES REQUIRED 22

2.6. PRESSURE DROP ON TUBE 23

2.7. TUBE LENGTH SUITABILITY CHECKING 24

2.8. TUBE THICKNESS SUITABILITY CHECKING 25

2.9. TUBE ARRANGEMENT 26

2.10. TUBE-SHEET LAYOUT 26

2.11. SHELL INSIDE DIAMETER, DS 27

2.12. BAFFLE DIAMETER 27

2.13. HEAT REMOVAL SYSTEM OF REACTOR 28

2.14. AMOUNT OF COOLANT NEEDED 28

2.15. HEAT TRANSFER AREA CHECKING 29

2.16. PRESSURE DROP ON SHELL SIDE 32

3. MECHANICAL DESIGN 35

3.1. REACTOR DESIGN PRESSURE 35

3.2. REACTOR DESIGN TEMPERATURE 36

3.3. REACTOR CYLINDRICAL VESSEL THICKNESS 37

3.4. BAFFLE CUT 38

3.5. REACTOR CLOSURES (HEAD AND CLOSURE) 39

3.6. HEIGHT OF REACTOR 40

3

3.7. DESIGN OF BOLTED FLANGE JOINTS 41

3.8. GASKET DESIGN 41

3.9. BOLT SIZING 44

3.10. DESIGN OF FLANGE 48

3.11. REACTOR WEIGHT 51

3.12. WEIGHT OF SHELL 52

3.13. TOTAL WEIGHT OF BAFFLES PLATE 53

3.14. WEIGHT OF TUBES 53

3.15. WEIGHT OF FLUID IN REACTOR 54

3.16. WEIGHT OF INSULATION MATERIAL 55

3.17. WIND LOADING 55

3.18. PRESSURE STRESSES 56

3.19. DEAD WEIGHT STRESS 56

3.20. BENDING STRESS 56

3.21. ELASTIC STABILITY (BUCKLING) 58

3.22. REACTOR SUPPORT 59

3.23. NOZZLES SIZING 61

3.24. FEED NOZZLE 61

3.25. OUTLET PRODUCT NOZZLE 62

3.26. COOLING WATER INLET NOZZLE 63

3.27. COOLING WATER OUTLET NOZZLE 63

4. SPECIFICATION SHEET 64

5. COST ESTIMATION 68

6. OPERATING MANUAL PROCEDURE 69

6.1. SCOPE AND OBJECTIVE 69

6.2. STANDARD OPERATING CONDITION 69

6.3. PROCEDURES 70

6.4. CATALYST CHANGE OUT PROCEDURE 72

7. MINOR EQUIPMENT DESIGN 1: COMPRESSOR 79

8. MINOR EQUIPMENT DESIGN 2: PUMP 85

8.1. INTRODUCTION 85

8.2. SELECTION OF THE PUMP TYPE 85

8.3. PROCESS DESIGN 86

9. REFERENCES 92

4

LIST OF FIGURES

Figure 1.1: Graph of Economic Potential Vs Purge Fraction

Figure 1.2: Types of Fixed-bed catalytic reactor

Figure 2.1: Temperature profiles for co-current flow

Figure 3.1: Torispherical flanged standard dished head

Figure 3.2: Full Face Flange

Figure 3.3: Gasket Width

Figure 3.4: Bolt Sizing

Figure 3.5: Bolt Spacing

Figure 3.6: Position of Gasket on Flange

Figure 3.7: Resultant Stress of Reactor

Figure 6.1: Vacuum System for Unloading Catalyst

Figure 6.2: Installation of Thermocouple

Figure 7.1: Four types of compressor, centrifugal, axial, reciprocating and rotary

compressor (clockwise) (Saeid et al. 2006)

Figure 7.2: Approximate polytrophic efficiency centrifugal and axial flow

compressor (Sinnot 2000)

Figure 8.1: Schematic diagram of basic element of a diaphragm pump

5

LIST OF TABLES

Table 1.1: Reactor Type Screening

Table 1.2: The advantages and disadvantages of FBR and MTFBR

Table 1.3: Main characteristics of Fixed-bed multi tubular reactor

Table 2.1: Feed Stream Composition

Table 2.2: Outlet Stream Composition

Table 2.3: Stoichiometric table for methanol process

Table 2.4: R-201 Coolant Information

Table 3.1: Bolt Sizing

Table 4.1: Specification Sheet for Methanol reactor, R-201

Table 5.1: Correction factor for pressure vessels

Table 7.1: Specification Sheet for compressor K-301

Table 8.1: Properties of process streams of P-203

Table 8.2: Pipe roughness

Table 8.3: Specification Sheet for pump P-203

6

CHAPTER 1

GENERAL DESCRIPTION

1.1 INTRODUCTION

The major equipment that will be discussed in this paper is methanol reactor. The

process design begins with the centre of the process, which is reaction conversion

and it is important criteria to have a good reaction conversion. This will determine

the economic viability of the overall design and fundamentally important to the

environment as well.

This will also give impact to the decision of choosing between one shell and multiple

contact tubes multi-tubular fixed bed reactors to be use in the methanol conversion

process. This is very important decision as this process is highly exothermic process.

This methanol reactor is basically to convert syngas into methanol by a

heterogeneous catalytic system

1.2 DESIGN METHODOLOGY

The design methodology for the methanol reactor (R-201) can be divided into 2

major sections; the process design and mechanical design. The process design give

impact to the determination of reactor volume (Levenspiel plot) and heat transfer.

The mechanical design of R-201 utilizes British Standard 5500 reference and design

values were referred to data provided in the Mechanical Design of Process

Equipment Data Hand Book.

Overall design was carried out accordingly, as per listed follows

7

1. Select the major equipment Methanol Reactor, R-201

2. Justify the type of reactor that is suitable for the process.

3. Determine the optimum operating conditions.

4. Perform calculation based on rate of reaction to obtain the volume of the

reactor.

5. The value from calculation is used as input data in ICON simulation.

6. Size reactor accordingly.

7. Obtain the necessary parameters from reactor sizing calculation and proceed

with equipment mechanical design.

8. Costing is done on the reactor and the utilities needed.

9. Perform technical drawing of the designed reactor.

10. Perform start up and shut down procedures for the reactor.

From research and development done, it is proven that methanol conversion by using

low temperature reactor. This is due to the effect of having a catalyst operating at

high temperature will damage or shorten its lifespan, losses in form of catalyst

replacement will take place and low yield (due to hotspots) will be incurred. Thus,

having a lower temperature reactor will give a lower probability of runaway reaction

and catalyst deactivation.

The overall reactions involved in production of methanol are as follows:

CO+2H2 CH3OH Hrxn = -9.1104 kJmol-1

CO2+3H2 CH3OH+H2O Hrxn = -4.9104 kJmol-1

CO + H2O CO2 + H2 Hrxn = -4.2104 kJmol-1

The operating conditions of reactor are as follows:

Catalyst : Cu (60-70%) - ZnO (20-30%) Al2O3 (5-15%)

Temperature : 220oC-300oC

Pressure : 50-100Atm (5-10MPa)

Composition of the feed : 59 -74%H2 27- 15% CO 8% C02

Conversion : CO to methanol per pass is normally 16 40 %.

H2 : CO ratio : 2-4

The selectivity : Around 99.8 %

8

1.3 FEEDSTOCK, REACTION AND RATE OF REACTION

Feedstock of this reaction is mainly syngas. Feed impurities are in gaseous form

which is difficult to be purified. Rule of thumb stated that it is desired to recover

more than 99% of valuable reactants. Syngas cost is expected to increase every year;

losses incurred for not recovering unconverted syngas of would be significant over

minimum plant life of 15 years.

Hence, there shall be a recycle stream to recycle unconverted syngas together with

other inert gaseous. Purging is needed in order to prevent accumulation in the

system. The ratio of recycle-purge composition is to be justified economically.

Figure 2.1 exhibits the economic potential versus purge fraction, from here; it can be

deduced that the optimum purge fraction which yield the highest economic potential

is at 0.4.

Figure 2.1 : Graph of Economic Potential Vs Purge Fraction

Reaction will take place in gaseous phase, under continuous mode. The market for

methanol is available all the time, methanol is not a seasonal product and due to its

wide applications it is used all year long by numerous industries. Besides that, the

reaction rate involve in synthesizing methanol is very fast having short residence and

the product itself does not have short product lifetime.

Graph Of Economic Potential Versus Purge Fraction

326000000

327000000

328000000

329000000

330000000

331000000

332000000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Purge Fraction, Ypg

Eco

nom

ic P

ote

nti

al (

EP

3)

(US

D/Y

EA

R)

9

1.4 REACTOR SELECTION

Following table is to screen between three types of reactor which are: Stirred Tank

Reactor, Fixed Bed Catalytic Reactor and Fluidized Bed Catalytic Reactor

Table 2.1: Reactor Type Screening

Stirred Tank

Reactor

Fixed Bed Catalytic Reactor Fluidized Bed Catalytic

Reactor

Not practical for

gas-solid reaction

Highly suitable for gas-

solid reaction

Approximate plug flow

Not suitable for highly

exothermic reaction;

counteracted by having

shell and tube arrangement

shell and tube arrangement

give good temperature

control, can be operated

isothermally and provide

mixing

Tend to have hotspot in

catalyst if reaction is

exothermic; counteract by

diluting the catalyst

Low operating cost

High conversion per unit

mass of catalyst

Easy to scale up

Suitable for gas-solid

reaction

Could NOT approximate

plug flow behavior

Suitable for highly

exothermic reactions

Fluidized bed is difficult to

scale up; posed limitation

for future expansion

Carryover of catalyst; cause

fouling in equipment

broad residence time

distribution

Erosion of bed internal and

attrition of catalyst particles

is possible

From the choices given, Fixed Bed Catalytic Reactor is chosen to be the type of

reactor used in this process. Fixed-bed reactors are used because the process is a

heterogeneous catalysis process where the catalyst and reacting species are of

different phases [Timmerhaus et al,2003].

10

The advantages using fixed bed reactor compare fluidized has been summarized in

the table below.

Table 2.2: The advantages and disadvantages of FBR and MTFBR

Fluidized Bed Reactor Multi- Tubular Fix Bed Reactor

Advantages 1. Internal Cooling Coils For Heat

Removal- Effective Temperature

Control- Avoid Hot Spot

1. Efficient Contacting In The

Reactor Flow In PFR Manner

2. Internal Or External Cyclones To

Minimize Catalyst Carry Over

2. Gives Higher Conversion Per

Weight Of Catalyst

3. Usually Use For Liquid Phase-

Assure Intimate Contact Between

Feed & Product Vapors, Catalyst

And Heat Transfer Surface

3. Suitable Liquid And Gas Phase

4. No Catalyst Stickiness And

Highly Efficient Over Many Years

Of Operation

Disadvantages

1. Agglomeration Catalyst Carry

Over Downstream- Copper

Contaminated

1. Not Effective In Temperature

Control- Hot Spots - Overcome

This Problem By Putting The

Cooling Medium On The Shell Side

2. Reduce Heat Transfer Capability

In The Reactor And Reduce

Reaction Rates

2. Besides, Temperature Control By

Multiple Reactors In Series- But

Increase Cost

3. Inherent Back Mixing- Difficult

To Achieve Total Conversion Of

Limiting Feed (Hcl)

4. High Cost Of The Reactor And

Catalyst Regeneration Equipment

11

Generally, fixed-bed reactors operate with axial flow of fluid down the bed of solid

particles. Radial flow is not commonly used. Hence, Methanol Reactor, R-201

operates with axial flow of gas.

Figure 2: Types of Fixed-bed catalytic reactor

The decision on reactor hest effects is done by estimating the reactor heat load and

adiabatic temperature change for both of the reactors. Correlation used is as below.

)( ,, outRinRpFPRR TTFCFHQ ==

Where

RQ = Heat load

RH = Heat of reaction

FPF = F = Flow into reactor

pC = Heat capacity

RT = Reactor streams temperature

The result from heat integration using ICON simulation indicates that adiabatically

operated reactor is feasible in this case. According to heuristic, less than 15%

increment in the reactor outlet temperature, adiabatic reactor is feasible. For direct

FBCR

Axial Flow Radial Flow

Non-adiabatic operation

(multi tubular)

Adiabatic operation

Catalyst

outside tubes

Catalyst

insides tubes

Single-stage Multistage

Inter stage heat

transfer

Cold-shot

cooling

12

heating and cooling, heuristic states that the heat load should not be more than

hrBTU6108 .

Thus, since the heat effects do NOT exceed the limit. The reactor is to be operated

by direct heating and cooling. In addition, for reactions with significant heat of

reaction, adiabatic reactor is a better option.

1.5 THERMAL AND BED ARRANGEMENT

For axial flow of fluid, the division for thermal considerations is between adiabatic

and non adiabatic operation. In adiabatic operation, no attempt is made to adjust the

temperature within the bed by means of heat transfer. In production of methanol, the

operation is adiabatic. Heat transfer for control of temperature is accomplished

within the bed itself. Thus the reactors are multi tubular reactors and not multistage

reactors.

Table 2: Main characteristics of Fixed-bed multi tubular reactor

Characteristics Fixed Bed (Multi tubular)

Energy Transfer Mechanism Shell and tube heat exchanger

configuration with tubes packed with

catalyst

Design Variable(s) Tube surface area to volume ratio.

Conversion Plug flow behavior ensures high

conversion per unit mass of catalyst.

Operation Continuous operation

Maintenances Fixed-bed device will have to be taken

offline to regenerate the catalyst by

means of shutting down the plant or using

standby reactor. Not suitable for frequent

catalyst regeneration.

13

Temperature Control Temperature control with liquid, gaseous

or boiling heat transfer agent in shell side

space.

Suitability for heterogeneous

catalytic gas phase reaction

Catalyst attrition negligible.

Catalyst Lifetime For catalyst that is deactivated slowly

14

CHAPTER 2

PROCESS DESIGN

2.1 OPERATING CONDITIONS

The operating conditions of reactor R-201 are as follows:

Methanol Reactor Operating Conditions (R-201)

Operating Temperature : 250 C

Operating Pressure : 68.28 Bar

Based on the simulation on iCON, the following stream tables properties are obtain.

There are two main streams considered here which are the inlet stream of R-201 and

the outlet stream of R-201. The conditions of the streams are as follows:

Feed Stream into R-201:

Operating Temperature : 250 C

Operating Pressure : 70 Bar

Outlet Stream from R-201

Operating Temperature : 250 C

Operating Pressure : 68.28 Bar

15

The following table shows the Feed Stream Composition:

Table 2.1: Feed Stream Composition

No. Component Flowrate

(kmol/hr)

1 Methane 27.60

2 Ethane 0.00

3 Oxygen 0.00

4 Carbon monoxide 13221.39

5 Hydrogen 53776.42

6 Carbon dioxide 6725.35

7 Water 8526.30

8 Methanol 41.61

9 Propane 0.00

10 Acetic acid 0.00

11 Nitrogen 107.60

12 Hydrogen sulfide 0.00

13 Methyl acetate 0.00

14 Argon 12.08

TOTAL 82438.36

16

The following table shows the Outlet Stream Composition:

Table 2.2: Outlet Stream Composition

NO. Component Flowrate

(kmol/hr)

1 Methane 27.60

2 Ethane 0.00

3 Oxygen 0.00

4 Carbon monoxide 13221.39

5 Hydrogen 53776.42

6 Carbon dioxide 6725.35

7 Water 8526.30

8 Methanol 41.61

9 Propane 0.00

10 Acetic acid 0.00

11 Nitrogen 107.60

12 Hydrogen sulfide 0.00

13 Methyl acetate 0.00

14 Argon 12.08

TOTAL 82438.36

17

2.2 REACTOR VOLUME DETERMINATION

CO+2H2 CH3OH

Or, symbolically,

CO+2H2 CH3OH

The forward and reverse specific reaction rate constant , kA and k-A, respectively, will

be defined with respect to carbon monoxide. Carbon monoxide (A) is being depleted

by forward reaction

CO+2H2 CH3OH

In which the rate of disappearance of carbon monoxide is

CCkr bAAforwardA2

,=

For reverse reaction

CO+2H2 CH3OH

The rate of formation of carbon monoxide is given as

Ckr cAreverseA2

, =

The net rate of formation of methanol is the sum of the rates of formation from the

forward and reverse reaction

rrr reverseAforwardAA ,, +=

CkCCkr cAbAAA22

+=

kA

k-A

k-A

k-A

k-A

18

Multiplying both sides of the rate law equation by -1, we obtain rate law for the rate

of disappearance of nitrogen, -rA:

=+=

Ckk

CCkCkCCkr cA

A

bAAcAbAAA

2222

=

KC

CCkrC

c

bAAA

2

2

Where Kkk

C

A

A =

The Stoichiometric table for the gas phase-reaction is given in table below

Table 2.3: Stoichiometric table for methanol process

Species Symbol Concentration

CO A

=

PTX

X PTCC

OO

AOA 11

H2 B

=PTX

Xa

b

PTCC

OOB

AOB

1

CH3OH C

=

PTX

Xa

c

PTCC

OOC

AOC

1

19

= = = = 53776.4213221.39 = 4.067 = 12705.1213221.35 = 0.961

= = + 1 = 11 21 1 = 2 = 0.16038 2 = 0.32076

= !"# = 0.16038 68$% &0.082 $%%'%()* + 523* = 0.2543%()%'

Neglecting pressure drop in the reaction, P = PO and the reaction is isothermal T =

TO, we obtain as follows

=

X

XCC AOA 1

1

=X

Xa

b

B

AOB CC

1

=X

Xa

c

C

AOC CC

1

Therefore,

= 1 ,1 0.32076, = & 4.067 2,1 0.32076,+ = & 0.961 + ,1 0.32076,+

20

Since Ammonia reaction is an equilibrium reaction, therefore the equilibrium

constant can be dictated as follows:

* = ---. = /0.961 + ,1 0.32076,01 1 ,1 0.32076, 2 1 / 4.067 2,1 0.32076,02.

From literature review and previous calculation

* = 14.5& = 0.2543 %()%' Thus,

14.5 = 1/ 0.961 + ,-1 0.32076,-020.06467 1 1 ,-1 0.32076,- 2 1/ 4.067 2,-1 0.32076,-02.

0.9377 = 1/ 0.961 + ,-1 0.32076,-021 1 ,-1 0.32076,- 2 1/ 4.067 2,-1 0.32076,-02. The equilibrium conversion, is computed using scientific calculator fx-570ES,

,- = 0.9515 According to Fogler (2006), the design equation for a fixed-bed reactor is analogous

to those for a plug-flow reactor. Thus, to obtain the volume of the reactor for a

specified conversion, the following equation will be used for the volume

determination

4 = 5 6789 4 = 5 6: /. *0

89

21

The rate constant, is obtained from the Arrhenius Equation (D.C. Dyson et al.,1968)

: = 0.1080 4 = 5 6:; 1 ,1 0.32076, 10.2543 / 4.067 2,1 0.32076,02. / 0.961 + ,1 0.32076,014.5 ?.89

4 = :5 14.5 1 0.32076, '614.50.2543 1 , 4.067 2, . 0.961 + , 1 0.32076, ..89 @ = ABC. DEF (Reactant Fluid Volume)

(Compute using scientific calculator fx-570ES)

Thus, the space time for R-201 can be calculated as follows:

G = 4H = 275.8%'34075.12%' 7J = 8.093 10K'7 = 29.14L R-6 has a contact time of 29.14 s. The space velocity is then the reciprocal of space

time = 123.557KM LNOHO)(P$ = 1G = H4 = 123.557KM = 0.03432LKM

For a plug flow reactor, the calculated V is only the volume of reactant fluid (not

including catalyst surface). The void fraction in a packed bed is defined as the

volume of voids in the bed divided by the total volume of the bed (Geankoplis,

1993). Assume the void fraction of the catalyst bed as 50% of the total volume of

reactor, = 0.5. Therefore, actual reactor volume:

22

4Q-RSTUQ =4 = 275.80.5 = 413.7%'

2.3 CATALYST

The volume of catalyst in the transalkylation reactor is assumed to be half of the

whole reactor volume of 413.7%'. For reactor R-201, the catalyst mainly composed of CuO, ZnO and Al2O3 is used. From the literature, the catalyst has a shape of

cylinder and diameter of 2.2 mm with density of 1300-1500 kg/m3. Thus

VLL(W$)L$ = 1300:X%' 275.8%' = 358540:X

2.4 TUBE SELECTION

Suitable material for tubes in the reactor must be chosen. Stainless steel type 304

material (18Cr/8Ni) is selected because of its good corrosion resistance and

mechanical properties, and is usually used for heat exchanger tubing. This multi tube

reactor can be designed with close approximation to a shell and tube heat exchanger.

In a multi tube reactor with catalyst inside the tubes, the reactor volume must equal

the inside volume of the tubes. By selecting a tube diameter and length, the volume

per tube is calculated.

2.5 NUMBER OF TUBES REQUIRED

Through literature review, a few tube dimensions have been recommended.

Ullmanns (1975) recommended tubes of 3 to 5 m long, 2.5 cm in diameter. Rohm

Haas (2003) suggested tubes of the same length as Ullmanns but 1.9 to 3.0 cm in

diameter. Each reactor would have approximately 15,000 to 35,000 tubes. McKetta

(1975) recommended 0.75 to 2 in diameter tubes of 10 to 20 feet length. Each reactor

will house 5000 to 10,000 tubes.

23

Preliminarily, tubes of 2 in. stainless steel 304 pipe, with 20 ft (6.096 m) length are

selected. This is a large size for heat exchanger tubing but a large size is desirable for

good catalyst distribution and minimal wall effects. The properties of the pipe are

stated as below (Values obtained from Timmerhaus (2003) Table D-13):

Outside diameter : 0.0605 m

Inside diameter : 0.0525 m

Wall thinkness : 0.00792 m

Cross sectional area : 0.00423 m2

Therefore,

Y = 4Z;S[ = 413.7%'0.00216m. 6.096m = 15674.8$]OL Thus, 15 675 tubes are required.

2.6 PRESSURE DROP ON TUBE

The reactor is to be operated at 68.28 bar or 6828kPa of pressure. An initial of 1.72

bar or 1720 kPa pressured drop is assumed. From Fogler (2001)

!!9 = 1 2^[!9 9._ ^9 = `1 XSab' c1501 db + 1.75`e

Where G = superficial mass velocity

= porosity = volume of void/total bed volume = 0.8 gc = 1.0 for metric system

Dp = diameter of particle in bed = 2mm d = viscosity of gas passing through the bed = 0.00002044Pa.s a = gas density = 27.398 kg/m3

24

From iCON, mass velocity = 933595.35 kg/hr = 259.33 kg/s

` = VLLHO)(P$#($)7O(W$]OL = 259.33kg/s0.00423m. 15675 = 3.911 :Xm.. L ^9 = `1 XSab' c1501 db + 1.75`e

^9 = 3.9111 0.8 1.0 27.398 0.002 0.8' c1501 0.8 0.000020440.002 + 1.753.911 e ^9 = 199.37!% = 0.199 :!%

!!9 = 1 2^[!9 9._ !!9 = 1 20.199 6.096 6828 9._ = 0.9998

! = 6826:! Thus, pressure drop = 6828-6826 = 2 kPa < the initial assumption

2.7 TUBE LENGTH SUITABILITY CHECKING

Average volumetric flow rate per tube:

4Rj-QRk- = HY =34075.12%' 7J15675$]OL = 2.173%' 7J

Superficial velocity through tube

lm = 4Rj-QRk-;S =2.173%' 7J0.00423m. = 513.9%' 7J

Calculated space time, G = 8.093 10K'7 = 29.14L

25

Therefore, for the period of space time specified, the distance passed by the liquid is

[ = lmG = 513.9%' 7J 8.093 10K'7 = 4.159%< 6.096% Therefore the selected length is long enough for the gas to react before leaving the

reactor.

2.8 TUBE THICKNESS SUITABILITY CHECKING

The minimum pipe thickness (given in British Standard, BS 5500) :

$ = !obo2W !o where

Di = internal diameter

f = design stress

t = minimum thickness required

Pi = internal pressure, 200 kPa

The value of design stress of stainless steel 304 at 250 oC is given in Table 13.2,

Chemical Engineering, Vol. 6. By interpolation:

W._9 = 95Y/%%. !o = 10.97 = 1090:! 1.05 = 911.45:!

The above pressure is calculated after considering 5% safety factor for internal

pressure. Therefore,

$P:qOLLros = 911.45:! 0.0525%2 95000:! 911.45:! = 0.00025% $P:qOLLros = 0.00025% < 0.00792m

Since the thickness of the tube selected is greater than the minimum required

thickness, it is capable to withstand the operating pressure of the reactor.

26

2.9 TUBE ARRANGEMENT

Since the reactor operates at high temperature, thus higher heat transfer rate is

required. The tubes arrangement need to be adjusted so that the heat transfer rate

between the shell side and tube side is efficient considering the distance between the

tubes. Therefore equivalent triangular pattern is selected. The recommended tube

pitch (distance between tube centre) is 1.25 time the outside diameter of the tube.

= 0.0605% !T = 1.250.0605% = 0.075625%

2.10 TUBE-SHEET LAYOUT

Estimation of Bundle diameter:

YT = *M &bt+su (7bt = &YT*M+Msu

where Nt = number of tubes

Db = bundle diameter, m

do = tube outside diameter, m

The value of K1 and n1 is available in Table 12.4, Chemical Engineering, Volume 6,

by R.K. Sinnot.

The triangular pattern is chosen because of the higher heat-transfer rate, but at the

expense of higher pressure drop. For triangular pattern and one pass flow:

K1 = 0.319

n1 = 2.142

Therefore:

bt = 0.0605 &156750.319 +M..Mv. = w. FBCE

27

2.11 SHELL INSIDE DIAMETER, DS

Practically, the shell diameter must be selected to give as close a fit to the tube

bundle and also to reduce bypassing round the outside of the bundle. Typical values

of clearance required between the outermost tubes in the bundle and the shell inside

diameter can be obtained from Figure 12.10 (Sinnot, 2000). Extrapolation on the

fixed and U-tube line is performed.

xO))PqLPOP%O$O7 ]q)OP%O$O7 = 10y]q)OP%O$O7 + 10 = )O7qO

= 109.375% + 10 = 103.75%

xO))PqLPOP%O$O7 = 0.10375% + y]q)OP%O$O7 = 0.10375% + 9.375% = w. zBDBCE

2.12 BAFFLE DIAMETER

Baffle type: single segmental baffle

From Table 12.5, Chemical Engineering, Vol. 6, the recommended baffle diameter

is:

Dbf = Ds - 4.8 mm

= (9.47875 - 0.0048) m

= 9.47395 m

The optimum baffle spacing is usually between 0.3 to 0.5 times the shell diameter.

Value of 0.3 is chosen.

lbf = 0.3 (9.47395) = 2.842185 m

Number of baffle required = Total tube length/baffle spacing

28

= 6.069 / 2.842185

= 2.14 3 baffles

3 baffles were chosen to ensure fluid stream across the tubes.

Baffle spacing = Tube length/(No. baffles+1) = 6.096/4 = 1.524 m

2.13 HEAT REMOVAL SYSTEM OF REACTOR

Since the reaction is exothermic, heat must be removed so that the temperature will

not increase too high which will affect the reaction. Heat is removed from the reactor

by generating steam on the shell sides of the tubes. Water flows to the reactor from a

steam drum, to which make-up water (BFW) is supplied.

The steam leaves the drum as saturated vapour. Cooling water with high pressure is

chosen well to ensure good heat transfer. Water is usually the first fluid consider,

since it is cheap, easy available, nonflammable, and compatible with many effluent

vapor. Its counter-currently circulated with respect to the gas inside the tube due to

nature of liquid and gas flow.

2.14 AMOUNT OF COOLANT NEEDED

It has been decided that the pressure for the closed loop recirculated cooling water

will be supplied at 400 kPa so as to ensure that there is not much difference of

pressure between the tube side and the shell side. At 400 kPa, the boiling point of

water is 144 C. The properties of water at 144 C, 400 kPa are as shown as below.

Table 2.4: R-201 Coolant Information

Coolant Type Closed loop recirculated cooling water at 400 kPa

Density at Tav= 144oC 922.20 kg/m3

Heat Capacity at Tav= 144oC 4.255 kJ/kg.C

Viscosity at Tav= 144oC 0.000190 kg/m.s

29

From iCON simulation results, 1.6859 x106 kJ/hr of heat has to be removed. The

water in the tube side will be supplied at 110C at the inlet and will exit at the

temperature of 135 C which is before the point of boiling of water (400 kPa). The

amount of water needed for the heat transfer was calculated as below.

q = mCpT

Flow rate of coolant required:

m = TC

q

p

= )110135(255.4

/106859.1 6

hrkjx

= 15, 848.65 kg/hr = 4.40 kg/s

2.15 HEAT TRANSFER AREA CHECKING

The general equation for heat transfer across a surface is

Q = UATm (12)

Where Q = heat transferred per unit time

U = the overall heat transfer coefficient, W/m2C

A = heat transfer area in unit m2

Tm = the mean temperature difference, the temperature driving force in C

The objective here is to determine the surface area required for the specified heat

transfer duty. This is done through the calculation of mean temperature difference

Tm. Tm can be calculated by calculating logarithmic mean temperature

difference which can only be applied when there is no change in the specific heats,

the overall heat-transfer coefficient is constant and there are no heat losses. For co-

30

current flows, single pass tube, following figure shows the temperature profiles

whilst the formula prior to calculate the logarithmic mean temperature difference is

stated as follow

Tm = Tlm

( ) ( )( )( )22

11

2211

lntT

tT

tTtTTlm

=

Where Tlm =log mean temperature difference

T1, T2 = inlet and outlet temperature of shell side fluid

= water (400 kPa) temperature,

inlet = 110C, outlet = 135C

t1, t2 = inlet and outlet temperature of tube side fluid

= process fluid temperature,

inlet = 145C, outlet = 155C

Figure 2.1: Temperature profiles for co-current flow

T1 = 145

T1=110

T2 = 155

T2 = 135 Shell

tube

31

Tlm = ( )[ ]

)135155(

)110145(ln

)135155(110145

= 5.54 C

Assuming overall heat transfer coefficient, U = 50 W/m2.C

Therefore, the required heat transfers area:

A = lmTU

Q

= )/3600)(54.5(50

/106859.1 9

shrC

hrJ

= 1690.63 m2

As for heat transfer area checking purpose,

The number of tube in reactor = 15 675 tubes

Length of tube = 6.096 m

Heat transfer area per tube = d0L

= (3.142) x (0.0605 m) x (6.096 m)

= 1.1586 m2

Therefore,

Total surface area of tubes = 1.1586 m2 x 15 675 tubes

= 18161.7 m2 (> 1690.63 m2)

Hence, heat transfer area given by total number of tubes of the designed reactor is

sufficient to extract the heat required for the exothermic reaction to occur.

32

2.16 PRESSURE DROP ON SHELL SIDE

The flow pattern in the shell of a segmentally baffled multitubular reactor is complex

and this makes the prediction of the shell side heat transfer coefficient and pressure

drop much more difficult if compared to the tube side. Although the baffles are

installed to direct the flow across the tubes, the actual flow of the main stream of

fluid will be a mixture of cross flow between the baffles, coupled with axial (parallel)

flow in the baffle windows. There are 2 main methods in determining the pressure

drop at the shell side namely; Kerns and Bells method. As for this reactor design,

Kerns method has been applied.

Basically, Kerns method does not take into account of the bypass and leakage

streams, however it is simple to apply and can be consider accurate enough for the

preliminary design calculations. On the other hands, in Bells method the heat

transfer coefficient and pressure drop are estimated from the correlations for flow

over ideal tube-banks, and the effect of leakage, bypassing and flow in the window

zone are taken into consideration by applying the correction factors for each terms

respectively. [10] From Sinnott (1999), the shell side pressure drop is given by

14.02

28

=

w

s

e

s

B

fs

u

d

D

l

LjP

(16)

Where L = tube length = 6.096m

lB = baffle spacing = 2.842185 m

Ds = shell diameter = 9.47875 m

= water density = 922.20 kg/m3 at 144 C

= viscosity of water = 0.000190 kg/m.s

= 0.19 cP = 1.9 x 10-4 Pa.s at 144C

us = molten salt linear velocity, m/s

jf = friction factor, (can be determined after obtaining Reynolds number,

Re = u s de/)

pt = Tube pitch = 0.075625% m (obtained from previous calculation)

33

de = equivalent diameter ( equilateral triangular pitch arrangement)

= ( )22 917.010.1 oto

dpd

= ( )22 0605.0917.0075625.00605.0

10.1

= 0.043 m

us = water linear velocity = Gs/ and Gs = s

s

A

W

where Ws = fluid flowrate on the shell side in unit kg/s

From 2.14

The desired water flowrate, Ws = 4.40 kg/s

Cross-flow area, As = t

Bsot

p

lDdp )(

= 075625.0

842185.247875.9)0605.0075625.0(

= 5.388 m2

Thus Gs = 2388.5

/40.4

m

skg

= 0.8166 kg/s.m2

Water velocity, us = 0.8166 / 922.20 (density)

= 0.0009 m/s

34

Using this value, Reynolds number, Re is calculated:

Re = 00019.0

043.00009.020.922 = 1878.4

The Reynolds number falls in the region of laminar flow (Re 2100). Thus, Hagen

Poiseuille equation can be used. By referring to Equation 12-4 (Timmerhaus, 2003),

jf

To find the shell side pressure drop, viscosity correction term is neglected. Thus,

2

0009.020.922

0605.0

47875.9

842185.2

096.6)00851.0(8

28

2

2

=

= s

e

s

B

fs

u

d

D

l

LjP

= 0.01 Pa

= 0.00001 kPa

008517.0

Re

116

16

0

=

=

=

x

Vd

35

CHAPTER 3

MECHANICAL DESIGN

3.1 REACTOR DESIGN PRESSURE

In mechanical designs, the basic method or concept is to make the particular piece or

part of the equipment safe irrespective of the forces acting on it. Some examples of

the forces acting on a member are the forces due to the internal or external pressure

acting on the system, the gravitational force due to the weight of the vessel and

piping, force due to the wind acting on the vessel especially for the tall column and

finally the seismic forces cause by earth quakes.

For the mechanical design of the process equipment, the pressure is the most

important of all the forces acting on the equipment. The design pressure, Pd is the

maximum (worst case) pressure which the equipment has to withstand. Pd can be

calculated by modifying process design (i.e pressure acting on the system), Po

considering the noise in the control system and the effect of any safety relief valve

which may be present to arrive at the maximum working pressure, MWP.

In this reactor design, operating pressure of R-201 is Po = 68.28 Bar

Thus design pressure,

!{ = 68.287 1.10 = BC. |}D~ = BC|}. D The above pressure is calculated after considering 10% safety factor for internal

pressure.

36

3.2 REACTOR DESIGN TEMPERATURE

Determination of appropriate design temperature is vital prior to find the value of

allowable stress for the material of construction which is temperature dependent.

Design temperature is determined from the process design temperature. The

following heuristics are generally applied to determine design temperature:

i. For unheated part consider the highest temperature of the stored material.

ii. For part that is heated by means of steam, hot water, oil etc consider the highest

temperature of the heating media, or 10C higher than the maximum temperature that

any part of body is likely to attain during course of operation.

iii. For vessel where direct internal or external heating is employed by means of fire,

flue gas or electricity or for severe exothermic reactions that takes place

a) Consider the highest temperature of the inside material plus minimum of 20C if

vessel is shielded.

b) Consider the highest temperature of the inside material plus minimum of 50C if

vessel is not shielded.

c) For highly exothermic reactions, same condition as above applies.

For this reactor design, operating temperature of R-201 is To = 250 C, which is the

temperature at the outlet of the tube.

Thus design temperature,

#{ = 250 1.10 = ABC = CzD The above temperature is calculated after considering 10% safety factor for internal

pressure.

37

3.3 REACTOR CYLINDRICAL VESSEL THICKNESS

On the shell side, cooling water at an average temperature of 160C will be

circulating. As cooling water is not corrosive, carbon steel (Grade 2B IS : 2002-

1962) is chosen as material of fabrication for reactor shell as it is also can sustain

wide temperature condition from -40oC to 500oC.

The minimum shell thickness:

$ = !obo2W !o + Where

Di = internal diameter

f = design stress

t = minimum thickness required

Pi = internal pressure

J = Welding efficiency = 0.9 (Class 1)

c = corrosion allowance

38

Design stress of carbon steel (Grade 2B IS: 2002-1962)

W T-r._9 = 1.18 10 Y%%. Inside diameter of shell, DS = Di = 9.47875% Therefore:

$ = 7510.8 10'9.47875 21.18 10 0.9 7510.8 10' + $ = 0.3475% + = 347.5%% +

2mm corrosion allowance will be used. Therefore

$ = 347.5%% + 2%% = 349.5%% The above equation is only valid if and only if it satisfy the equation below,

bbo 1.5q $bo 0.25 b = bo + 2 $ = 10.17% bbo = 10.179.48 = 1.07 1.5

$bo = 0.34759.48 = 0.0366 0.25

3.4 BAFFLE CUT

Optimum baffle cut of 25% of baffle diameter is used. Therefore:

Baffle cut = 0.25 Dbf

= 0.25(9.47395 m)

= 2.368 m

39

3.5 REACTOR CLOSURES (HEAD AND CLOSURE)

A torispherical flanged standard dished head is chosen for this design. The advantages of

using this head are that it can be used for application of higher pressure and it has less

stress concentration as compared to flat plate. The minimum thickness required is:

$ = !"2W ! 0.2 = 14 3 + ""

Where J = joint factor = 0.9

f = design stress = 100 N/mm2

Rc = crown radius = should be greater than D0

Rk = knuckle radius = 0.06Rc

Rk/Rc should not be less than 0.06

b = bo + 2 $ = 10.17% < " = 14>3 + "0.06"? = 1.77

Therefore,

$ = 7510.8 10' 10.17 1.7721.0 10 0.9 7510.8 10'1.77 0.2 = 0.803% = 803%% Adding allowance, t = 803 mm + corrosion allowance + thinning of torus during

fabrication

$ = 803%% + 4%% + 0.06 7.28%% = 807%%

40

Volume of dish, V = 0.0847 Di3

= 0.0847 x 9.483

= 72.16 m3

Figure 3.1 : Torispherical flanged standard dished head

3.6 HEIGHT OF REACTOR

Height of the closure is also assumed, ho + Sf = 0.5 m. Thus,

the total height of the reactor = height of closures + tube length

= 2(0.5) + 6.096

= 7.096 m

807 mm

41

3.7 DESIGN OF BOLTED FLANGE JOINTS

Gasket and bolts are designed for both top and bottom closure flanges. Flanges are also

designed accordingly. Welding neck flanges are used here because it is suitable for

extreme service conditions such as high temperature. It has long tapered hub between

flange ring and weld joint. This helps reduce discontinuity stress between flange and

joint. It is commonly used for removable vessel heads for ease of access.

3.8 GASKET DESIGN

The function of gasket is to make a leak-tight joint between two surfaces. Gaskets are

produces from materials, which will deform and flow under load to fill the surface

irregularities between the flange faces, yet, at the same time retain sufficient elasticity to

take up the changes in the flange alignment that occur under load.

Selection of material of a gasket heavily depends on the process conditions, corrosive

nature of process fluid, the gasket location and type of gasket construction. For reactor

temperatures between 250 to 450C, metal reinforced gasket is recommended. Gasket

specification is obtained from Table 13 of Data Hand Book of Mechanical Design of

Process Equipment (ECB 5233).

Gasket material = Corrugated metal (Stainless steel, asbestos)

Gasket factor, m = 3.75

Min design seating stress, y = 52.5 MN/m2

Min actual gasket width = 10 mm

Design pressure, PD = 73.474 bar

Shell outside diameter, B = 10.17 m

Shell thickness, go = 0.3495 m

Meanwhile, full faced flange is used to hold the gasket in place. Following figure shows

that the face contact area extends beyond the bolt circle. It has a large bearing area, tight

42

enough to prevent leaks and suitable for low pressure operations. High bolt tension is

required to achieve sufficient gasket pressure to maintain a good seal at high pressures.

Figure 3.2: Full Face Flange

Selection of material depends on the corrosive action of chemicals that may contact the

gasket, the gasket location and type of gasket construction. It also depends on gasket

width. If the gasket is made too narrow, the unit stress on it will be excessive. If the

gasket is too wide, the bolt load will unnecessarily increased.

Determine the blank diameter, DB, and height of dish, ho for the toripherical closure.

fK

o

oB SRD

DD 23

2

42+++=

+

+

= fKo

Co

CCo SRD

RD

RRh 222

Calculate ratio of inner diameter to outer diameter of the gasket, do/di.

( )1+

=mPy

mPy

d

d

D

D

i

o

Where do = gasket outer diameter

di = gasket inner diameter

y = minimum design seating stress

43

PD= Design Pressure

m = gasket factor

o = 52.5 10 7510.8 10' 3.75 52.5 10 7510.8 10' 3.75 + 1 = 1.0001

Rule of thumb states that inner gasket diameter is 10mm larger than vessel outer

diameter.

Thus, gasket inner diameter, di = Do, reactor + 10mm

= 9.48 m + 0.01 m =9.49 m

Determine the inner and outer diameter of the gasket. = 9.49 1.0001 = 9.491%

Calculate the gasket width, W, where result will be round off to the nearest even number

for convenience purposes.

Figure 3.3: Gasket Width

2

io ddW

=

= 9.491 9.492 = 0.00005%

W W

do

di

44

3.9 BOLT SIZING

To estimate bolt loads

Figure 3.4: Bolt Sizing

Under internal pressure, G = di + N

= 9.491 m + 0.00005 m = 9.4915 m

Allowable stress of bolting material

So = 144 MN/m2 (Table 11)

Sg = 212 MN/m2

Wo = force due to pressure + load to achieve minimum sealing

= H + Hp

DPGH2

4

=

Where G = Diameter of gasket load Reaction

PD = Design Pressure = 4 9.4915. 7510.8 10' = 531VY

Assume raised-faced flanges are used,

Basic gasket seating width, bo = N/2

= 0.5 mm /2

= 0.25 mm > 6.3 mm

G

45

Thus, effective gasket seating width, b = bo = 0.25 mm

Load to keep gasket in compression,

Hp = G 2bmP

= 2(9.4915)(0.00025)(3.75)(7510.8x103)

= 0.4199 MN

Therefore, Wo = 531 MN +0.4199 MN

= 531.4 MN

Under bolting condition,

Wg = Gby

= (9.4915)( 0.00025)(52.5)

= 0.391 MN

Since Wo > Wg

Therefore, controlling load = Wo = 531.45 MN

Minimum bolt area, A = Wo/allowable stress

= 531.4 MN/83x106

= 6.402 m2

To estimate optimum bolt size, bolt of various sizes chosen from Table 10 (Mechanical

Design of Process Equipment Data Hand Book).

46

Table 3.1: Bolt Sizing

Bolt

diameter

(Table

10)

Ar,Root

Area (m2) R(mm)

Bolt

spacing,

Bs(mm)

No of bolts,

Am/Ar

No of bolts,

(factor of

4)

C =

nBs/

C =

B

+2(g1+R)

M14 x 1.5 0.000153958 22 75 447.5246496 448 10.700637 3.9492

M16 x 1.5 0.000201088 25 75 342.6360598 344 8.211330 3.9552

M18 x 2 0.000254502 27 75 270.724788 272 6.492680 3.9592

M20 x 2 0.0003142 30 75 219.2870783 220 5.251432 3.9652

M22 x 2 0.000380182 33 75 181.2289903 184 4.392107 3.9712

M24 x 2 0.000452448 35 75 152.2826933 152 3.635010 3.9752

M27 x 2 0.00057263 38 75 120.322128 120 2.872107 3.9812

M30 x 2 0.00070695 44 75 97.46092369 100 2.387015 3.9932

Inner shell diameter, Di = 9.491 m

Bolt circle diameter, C = nBs/ or = Di +2(g1+R)

Shell Thickness go = 0.807m

Hub thickness, g1 = 1.415 go (thickness of shell)

= 1.142 m

Chosen bolt diameter = M14 x 1.5 (suitability)

Number of bolts, n = 448

47

Bolt spacing, Bs = 75 mm

Bolt circle diameter, C = 3.9492 m

Actual bolt area, Ab = n*Ar =448*0.000153958= 0.069 m2 Am

Flange outside diameter, A = C + bolt diameter + 0.02 (minimum)

= 3.9492 + 0.014 +0.807

= 4.7702 m

In order to check the suitability of the gasket width,

Gasket width = 66.36< 105 (valid)

Thus, gasket selected is acceptable for design application.

Recalculating the actual bolt spacing, Bs = C/n

= (3.9492) (1000)/100 = 389.77 mm

Figure 3.5: Bolt Spacing

75 mm

389.77 mm

3.9752 m

yGN

SA gb2 Mo. Thus Mg is used for further calculation.

Flange thickness,

Initially, assume bolt pitch correction factor, CF = 1.00

y = correction coefficient = 18.55

St = Allowable stress of flange material = 100 MN/m2

From the calculations, t =)100)(8486.3(

)55.18)(1)(6480.0(

= 0.1767 m

= 176.6mm

g

bm

g xSAA

W2

+=

t

F

BS

yCMt

.=

50

Recalculated Cf = td

Bsactual

+2

= 1767.0)024.0(2

1249.0

+

= 0.5559

fC = 0.7456

Thus, actual flange thickness, t = 0.1767 m (0.7456)

= 0.13175m

= 131.75 mm

From Table 8, the nearest standard steel sheet has a thickness of 180 mm.

Thus, flange thickness, t = 180 mm

51

3.11 REACTOR WEIGHT

Pressure vessels are subjected to other loads besides pressure. The main sources of loads

to consider are: [10]

i. Pressure

ii. Dead weight of vessel and contents

iii. Wind

iv. Earthquake (seismic)

v. External loads imposed by piping and attached equipment.

Figure 3.6: Position of Gasket on Flange

t = 0.13175m

R = 0.035 m

g1=0.0283 m

g0=0.02mm

A = 4.092 m

C = 3.9752m

di = 3.8686 m

do = 3.9038 m

Di = 3.8086 m

52

Here the major sources of dead weight loads are: [10]

vi. The vessel shell

vii. The vessel fittings such as manway, nozzles etc

viii. Internal fittings- plates (plus the fluid on the plates), heating and

cooling coils

ix. External fittings ladders, platforms, piping

x. Auxiliary equipment which is not self-supported; condensers,

agitators.

xi. Insulation materials

3.12 WEIGHT OF SHELL

For cylindrical vessel with domed ends and uniform wall thickness, the total weights of

the shell is

Wv = 240CvDm (Hv + 0.8Dm) t (21)

Where Cv = factor, 1.15 for vessel with several manways, internal support, etc.

Dm = mean diameter of vessel = (Di + tx10-3) in unit m

Hv = height or length between tangent lines, m

t = wall thickness, mm

From the calculations,

t = 807 mm

Dm = 9.375 + (0.807) m = 10.182 m

Hv = Closure Height + length of tube = 7.096 m

53

Weight of vessel,

Wv = 240 (1.15) (10.182) [7.096 + 0.8(10.182)] x (807)

= 34565.77 kN

3.13 TOTAL WEIGHT OF BAFFLES PLATE

Number of plates = 3

Plate diameter = Db = 9.47875 m

Baffle cut = 25%

b = angle subtended by the baffle chord, rads = 2.1 rads

Baffle area =( )

2tan%25

22

12

2

2

4

22

bb

bbb DD

xx

xD

+

= 56.77 m2

Weight of plate = 1.2 kN/m2 (Table 34, Mechanical Design Handbook)

Total weight of baffle = 56.77 x 1.2 kN/m2 x 3

= 204.4 kN

3.14 WEIGHT OF TUBES

Number of tubes = 15675

Weight per feet of tube= 5.8 lb/ft= 81.4 N/m

(Refer: Table D-13, Timmerhaus (2003))

Length of tube = 6.096 m

Total weight of tubes = 15675 (6.096) (81.4)

= 7778.16 kN

54

3.15 WEIGHT OF FLUID IN REACTOR

Total weight of fluid in reactor comprises of the weight of fluid, catalyst and coolant. On

the tube side, the volume of fluid and catalyst are calculated.

Volume of fluid = 275.8 m3

Density of fluid = 27.3982 kg/m3

Weight of fluid = 275.8 x 27.3982 x 9.81

= 74128.5N = 74.1285 kN

Volume of catalyst = 275.8 m3

Density of catalyst = 1300 kg/m3

Weight of catalyst = 275.8 x 1300 x 9.81

= 3517277 N = 3517.277kN

Maximum Volume of Cooling water = volume of shell - volume occupied by tubes

= /4 (9.47875)2 (7.1) 15675[/4 (0.0605)2 (6.096)]

= 226.31m3

cooling water = 922.2 kg/m3

Weight of cooling water = 226.31 (922.2) (9.81)

= 2047.4 kN

Total weight of fluid = 74.1285 kN + 3517.277 kN + 2047.4 kN

= 5638.8 kN

55

3.16 WEIGHT OF INSULATION MATERIAL

Insulating material = mineral wool

Density = 130 kg/m3

Thickness = 100 mm

Approximate volume of insulation = (Do) (tinsulation) (L)

= (9.375) (0.100)(7.1)

= 20.91 m3

Weight of insulation = 20.91 x 130 x 9.81

= 26.668 kN

Total Weight of Reactor = 21474.1285 + 3517.277 + 2047.4 +26.668

= 5665.5 kN

3.17 WIND LOADING

Wind pressure Pw = kUw2

= 0.05 x 1602

= 1280 N/m2

Loading per unit length, Fw = PwDeff

Deff = Do + 2tinsulation + 0.4

= 9.375 + 2(0.1) + 0.4

= 9.975 m

56

Fw = 1280 x 9.975

= 12.768 kN/m

Bending moment at the bottom, M = Fw X2/2

= 12.768 x 7.12/2

= 321.81 kNm

3.18 PRESSURE STRESSES

The longitudinal and circumferential stresses due to pressure given by:

t

PDiL

4= =

8074

103753.9/882232.0 32

mmmmN= 2.5623 N/mm2

t

PDih

2= =

8072

103753.9/882232.0 32

mmN= 5.1247 N/mm2

3.19 DEAD WEIGHT STRESS

w = ttD

W

i

v

)( +=

807)807103753.9(

1000 1401.39713 +

x= 0.0543 N/mm2

3.20 BENDING STRESS

The longitudinal bending stress at the mid-span of the vessel is given by:

( )4464

2

DiDoI

tD

I

M

v

i

v

b

=

+=

57

Where,

M = Longitudinal bending stress at the mid-span

Iv = Second moment of area of the shell

)6.38086.3848(64

44 =

vI

= 4.4078x 1011 mm4

+= 202

6.3808

104078.4

10 .43521411

8

mmx

Nmmxb

= 0.6266N/mm2

Resultant longitudinal stress, z = L + w b

w is compressive, thus the value will be a negative value.

z (upwind)= (42.0001 - 5.8256 + 0.6266) N/mm2 = 36.8011 N/mm2

z (downwind)= (42.0001 - 5.8256 - 0.6266) N/mm2 = 35.5479 N/mm2

As assume that there is no torsional shear stress, the principal stresses will be z and h.

The radial stress is negligible,

2/4411.02

882232.0

2mmN

Pi ==

58

Figure 3.7: Resultant Stress of Reactor

To determine the maximum stress;

1 - radial = 84.0017 0.4411 = 83.5606 N/mm2

The value obtained is well below the maximum allowable design stress, f250C

(161N/mm2). Thus, the design is satisfactory.

3.21 ELASTIC STABILITY (BUCKLING)

If the resultant axial stress, z due to the combined loading is negative, the reactor may

fail due to elastic instability (buckling). The condition for this not to take place is the

maximum compression stress, c must be more than the critical buckling stress, c,max.

c,max = w + b (-ve)

= - 5.8256 - 0.6266

= -6.4522 N/mm2

36.8011

84.0017

Up-wind

35.8011

84.0017

Down-wind

59

c = 2 x 104 (t/Do)

= 2 x 104 (20/3848.6)

= 103.9338 N/mm2

The maximum compression stress is 6.4522 N/mm2< 103.9338 N/mm2, well below the

critical buckling stress. So design is satisfactory.

3.22 REACTOR SUPPORT

Reactor will be placed vertically. Cylindrical skirt support is used. The skirt thickness

must be sufficient to withstand the dead weight loads and bending moments imposed on

it by the vessel; it will not be under the vessel pressure. From Sinnot (2000) the resultant

stresses in the skirt will be:

wsbss tensile =)( And wsbss ecompressiv +=)(

Where =bs bending stress in the skirt

ssss

s

DttD

M

)(

4

+=

=ws the dead weight stress in the skirt,

sss ttD

W

)( +=

Where Ms = maximum bending moment, evaluated at the base of the skirt (due to wind,

seismic and eccentric loads,

60

W = total weight of the vessel and contents,

Ds = inside diameter of the skirt at the base,

ts = skirt thickness.

As first trial take the skirt thickness as the same as the shell thickness, 20 mm

ts = 20mm

Ds = 3.8086m (=Di shell)

W = 1401.3971 kN

Wind loading = Fw = 5.6942 kN/m

Bending moment at the base of the skirt

Ms = (5694.2 x (3.8086+0.020)2)/2 = 41.7333 kNm

=bs ssss

s

DttD

M

)(

4

+

= 4(41733.3)/((3.8086+0.020)(0.020)(3.8086))

=bs 0.1822 N/mm2

=wssss ttD

W

)( +

= 1401397.1/((3.8086+0.020)(0.020))

=ws 5.8256 N/mm2

wsbss tensile =)( = -5.6434 N/mm2

wsbss ecompressiv +=)( = 6.0078 N/mm2

61

The skirt thickness should be such that under the worst combination of wind and dead-

weight loading the following design criteria are satisfied:

sss Jftensile sin)(

s

s

s

sD

tEecompressiv sin125.0)(

where fs = maximum allowable design stress for the skirt material at ambient

temperature,

J = weld joint factor

s = base angle of a conical skirt, normally 80o to 90 o

E = Young modulus of the material = 200,000 N/mm2 for plain carbon steel

)(tensiles = -5.6434 N/mm2< 83.7 N/mm

2 satisfied

90sin4245

22000,200*125.0)(

ecompressivs

= 6.0078 N/mm2 < 131 N/mm

2 satisfied

3.23 NOZZLES SIZING

Four nozzles are designed according to each stream specifications: Feed stream nozzle,

reactor product outlet nozzle, cooling water (coolant) inlet, and cooling water outlet.

3.24 FEED NOZZLE

Optimum duct diameter, dopt = 226G0.5-0.35

Flow rate, G is obtained from HYSYS = 36.3945 kg/s

Density, also from HSYSY = 11.8126 kg/m3

dopt = 574.52 mm

= 0.5745 m

62

Nozzle thickness,

Design pressure = 7510.8 kPa

Material of construction = Stainless Steel 04 Cr 29 Ni 9

Design stress (250 )C = 0.98x108 N/m2

Nozzle thickness, e = 0.01466 m

= 14.66 mm

Adding corrosion allowance of 2mm, thickness of feed nozzle = 16.66 mm

3.25 OUTLET PRODUCT NOZZLE

Optimum duct diameter, dopt = 226G0.5-0.35

Flow rate, G is obtained from HYSYS = 36.3945 kg/s

Density, also from HSYSY = 8.7225 kg/m3

dopt = 638.85 mm

= 0.639 m

Nozzle thickness,

Design pressure = 7510.8 kPa

Material of construction = Stainless Steel 04 Cr 29 Ni 9

Design stress = 0.98x108 N/m2

Nozzle thickness, e = 0.01466 m

= 14.66 mm

Adding corrosion allowance of 2mm, thickness of feed nozzle = 16.66 mm

)P(2f

DPe

i

ii

=

)P(2f

DPe

i

ii

=

63

3.26 COOLING WATER INLET NOZZLE

Optimum duct diameter, dopt = 226G0.5-0.35

Flow rate, G decided = 4.40 kg/s

Density of water = 922.2 kg/m3

dopt = 43.6136 mm

= 0.04361 m

Nozzle thickness,

Design pressure = 7510.8 kPa

Material of construction = Carbon Steel

Design stress = 1.18x108 N/m2

Nozzle thickness, e = 0.12165 m = 121.65 mm

Adding corrosion allowance of 2mm, thickness of feed nozzle =123.65 mm

3.27 COOLING WATER OUTLET NOZZLE

Optimum duct diameter, dopt = 226G0.5-0.35

Flow rate, G decided = 4.40 kg/s

Density of water = 922.2 kg/m3

dopt = 43.6136 mm

= 0.04361 m

Nozzle thickness,

)P(2f

DPe

i

ii

=

)P(2f

DPe

i

ii

=

64

Design pressure = 882.232 kPa

Material of construction = Carbon Steel

Design stress = 1.18x108 N/m2

Nozzle thickness, e = 0.12165 m = 121.65 mm

Adding corrosion allowance of 2mm, thickness of feed nozzle =123.65 mm

CHAPTER 4

SPECIFICATION SHEET

Following table and figure are the specification sheet and drawing for the methanol reactor

which is the R-201. The specification sheet provides the summary of all the important

information of the methanol reactor and the figures shows the mechanical drawing of the reactor.

65

Table 4.1: Specification Sheet for Methanol reactor, R-201

Reactor Data Sheet Equipment No.(Tag) R-201

Description Methanol Reactor

Sheet no. 1/1

OPERATING DATA

No. REQUIRED 1 ORIENTATION Vertical

TYPE Multitubular Catalytic Fixed Bed JACKETED Yes

SHELL TUBE

CONTENTS Cooling water Methanol, hydrogen, carbon

monoxide, carbon dioxide, water

DIAMETER (OUTER) 9.47 m 0.0605 m

LENGTH 7.1 m 6.096 m

DESIGN CODE BS 5500 BS 5500

MAX. WORKING PRESSURE 6828.0 kPa 6828.0 kPa

DESIGN PRESSURE 7510.8 kPa 7510.8 kPa

PRESSURE DROP (ALLOWED/CALC) 0.1 kPa 2 kPa

MAX. WORKING TEMP 155`C 250`C

DESIGN TEMPERATURE 175C 275 C

VELOCITY 440 kg/s 259.3 kg/s

No. OF PASSES 1 1

HEAT EXCHANGED 1.6859x106 kJ/hr - 1.6859x106 kJ/hr

MECHANICAL DESIGN ON SHELL

MATERIAL Carbon Steel

JOINT FACTOR 0.9

CORROSION ALLOWANCE 2 mm

THICKNESS 807 mm

NO. OF BOLTS 448 DIAMETER 18mm MATERIAL Cr-Mo STEEL

NOZZLE Torispherical THICKNESS 16.66mm MATERIAL Carbon Steel

FLANGE Torispherical THICKNESS 131.75mm MATERIAL Carbon Steel

GASKET WIDTH 0.5mm MATERIAL Asbestos

MECHANICAL DESIGN ON TUBES

MATERIAL Stainless Steel 304 (18Cr/8Ni)

NO. OF TUBES 15675

NOMINAL SIZE 0.0565 m

OD 0.0605 m

ID 0.0525 m

THICKNESS 0.00792 m

TUBE PITCH 0.076 m (triangular)

CATALYST

TYPE CuO-ZnO-Al2O3

SPECIFIC SURFACE AREA 115 x 1015 m2/g

SHAPE Sphere

BULK DENSITY 1300-1500 kg/m3

DIAMETER 5 mm

POROSITY 0.5

LIFE SPAN 2years

REMARKS AND NOTES :-

66

67

68

CHAPTER 5

COST ESTIMATION

Purchased Cost, $ = ( )CFHDSM 82.0066.19.101280

&

Where D = diameter, ft = 14.58

H = height, ft = 87.48

Fc = Fm Fp

M&S = Marshall and Swift Index = 1309.8

Table 5.1: Correction factor for pressure vessels

Shell material CS SS Monel Titanium

Fm clad 1.00 2.25 3.89 4.25

Fm solid 1.00 3.67 6.34 7.89

Material of the reactor is SS therefore Fm = 3.67

Fp = 1.18

Fc = Fm Fp = 4.33

Purchased Cost, US$ = $1,404,881.68

F.o.b equipment cost, US$ = 55,056.43 (extrapolation from figure E.2-3, Douglas, 1988)

Total Cost, US$ = $1,459,938 = RM 4,470,330.49

69

CHAPTER 6

OPERATING MANUAL PROCEDURE

6.1 SCOPE AND OBJECTIVE

This procedure provides operating instruction for the Methanol Reactor System;

Included are operation instructions for system start-up and shutdown.

6.2 STANDARD OPERATING CONDITION

Parameter Normal Set point (R-201)

Temperature 250 C

Flow rate 933595 kg/hr

Pressure 6828 kPa

70

6.3 PROCEDURES

Reactor Pre-start up Procedures

No Procedures Steps Checklist

1 Ensure that inventory is available at each unit operation. Note that

reactor will be last unit operation to start up.

2 Verify Vessel Readiness for start up, i.e., all maintenance and I&E

works completed, the reactor is clean and rinse with process water

as necessary, man way close, and all blind are removed and proper

gasket are installed.

3 Line up cooling water to shell-side of R-201

4 Line up all transmitter and stroke all control valve

5 Close, plug and cap all bleeders

6 Place the reactor temperature indicators and pressure indicator (PI)

in service

7 Purge reactor with high pressure N2 until vent O2 is less than 6%.

8 Pressure up the reactor with high-pressure nitrogen to 400kPa and

performed leak check on all flanges.

10 Pressure up the reactor to 6828kPa and check flanges for leaks.

Initiate the Reactor

No. Procedures Steps Checklist

1 Condition reactor, R-201, 6828kPa and temperature 250C

2 Adjust the feed to desired flow rate

4 The system is stabilized once feed is heated up to the standard

operating condition.

71

Hot Hold and Shut Down the Reactor

No. Procedures Steps Checklist

1 Notify Wastewater Unit, Utilities Unit and Shipping Unit.

2 Reduce flow rate to 70% of feed rate.

3 Shut down heat exchanger by gradually reducing hot stream flow

rate

4 Reduce reactor feed further to 50% of feed rate, then to 30%.

5 To HOT HOLD the reactor, block all isolation valves, control

valves and manual block valves for cooling water, oxygen and

feed. Verify at field that all isolation and control valve are closed.

This is to put reactor on HOT HOLD.

6 To SHUT DOWN the reactor, block all isolation valves, control

valves and manual block valves for feed. Verify at field that all

shutoff and control valve are closed.

7 Open both man way of the reactor and inspect inside the reactor.

Access the need of cleaning. Prepare the reactor for washing with

process water if required.

8 Inspect the condition of catalyst inside reactor. Check if there is

any coking or crash powder of catalyst.

9 Prepare for vessel maintenance.

10 If not clean, perform washing.

Emergency Procedures: Placing Reactor on Hot Hold

When Reactor (R-201) is placed on Hot Hold, the reactor is isolated in an attempt to

maintain reactor pressure and temperature so that the feed stay in optimum temperature.

Cooling water is not allowed to cool down and solidify. An electric heater with backup

power supply (or generator) maybe used to keep cooling water temperature from

dropping. Loss of electrical power is the primary reason for placing the reactor on Hot

Hold. For power outages of short duration (< 10 minutes), the reactor shall be placed on

Hot Hold during power outage.

72

6.4 CATALYST CHANGE OUT PROCEDURE

The change out of the reactors catalyst is due to the end of the life of the catalyst.

Catalyst performance is monitored by the temperature profile across the reactor;

decrease in temperature profile across reactor indicates the deactivation of catalyst.

Thus, this will lead to the reduction in production of methanol. Once the production is

not at the target, decisions are made to change the catalyst.

Removal of Top and Bottom Cover of Methanol Reactor

Erect Scaffolding around the top and bottom part of methanol reactor prior to shut down.

Blind is put at the flange to avoid any foreign materials from entering the reactor or

lines. The top cover is removed and hanged by using 3 chain blocks

Dismantle thermocouples

There are 5 thermocouples that is to be removed Thermocouples are being removed very

slowly (unscrew) and carefully by vibrating it from side to side in order to avoid it being

stuck in the tubes.

Removal of Spool

The spool is removed after the top cover is being removed. Only the venting line is

removed (including the block valve).The process venting line is remained in position.

The venting line spool is removed and laid down at the side of the reactor. The un-

removed process line is covered with plastic to prevent any entrance of water or particle.

73

Removal of Spent Catalyst

For unloading of the old, spent catalyst, a large and powerful vacuum system is needed.

The vacuum host used must be in tight position the tube holes. The method used for

removing the spent catalyst is shown below.

Figure 6.1: Vacuum System for Unloading Catalyst

Tubes at the reactor

Plant air @4 bar

Step 2: The hollow rod is used to push the spent catalyst which is in packed and tight

condition. The vacuum host is used to suck all dust release during the activity.

Tube is pushed up

and down to remove

catalyst

Vacuum host

Step 1: A hollow rod is attached with the plant air source.

Plant air @4 bar

74

Tube cleaning

The reactor tubes may be fouled both on the inside and outside surface; thus reducing

the heat transfer of the heat of reaction from the process. Inside tube area fouling is

caused by compounds evaporated from the catalyst and condensed on the inner tube

surface.

Outside tube area may be fouled by compounds from decomposition, polymerization or

oxidation of the Dowtherm Oil. A long steel rod with a wire brush at the end of the rod

is used to clean the tubes.The brush rod is used to scrub the tubes for three times

(minimum) to ensure complete cleaning of the tube.

Upon completion of the tube cleaning, all the tubes are inspected to ensure the inner

surface of the tubes is clear of any deposit.

Eddy Current Test

300 tubes are selected randomly that are to be undergone eddy current test.The test is

concurrently carried out with the spent catalyst removal. Selected tubes for the test is

cleared and cleaned. Later the test is done while personnel removing catalyst from other

tubes. This is in order to minimize time lost.

A tube that has passed the test indicates that the tubes are free from corrosion or erosion

and the tube wall thickness is uniform.

Pneumatic Test

Blinding must be done before conducting the pneumatic test.Pneumatic test was

performed on the shell side as soon as the eddy current test completed. Shell side was

cleaned by hydro jet.

75

Loading a charge catalyst into a tubular reactor with thousands of tubes is not a enviable

job. It must be well planned and supervised in order to avoid poor loading. Poor loading

will results in poor performance of the reactor and uneven flow distribution among the

tubes.

For instance, a tube in which the catalyst has bridged during loading may end up with

too little catalyst with low pressure drop (equals high flow). This tube will pass more

unconverted syngas than the average tube. If a tube with bridging results in catalyst

being loaded far above the Dowtherm A level, overheating and possible damage to the

tube may occur during operation.

Catalyst Mixing

The catalyst loadings comprise a layer of diluted catalyst. It consists of a typical mixture

of Cu(60-70%)- ZnO(20-30%) Al2O3 (5-15%). Mixing is done by small amount (small

container where it is put in a bagging bag). This is to ensure thorough mixing of the

catalyst.

Installation of Mesh, Bottom Cover and Thermocouple

Before new catalyst is being charged in, the mesh, bottom cover and thermocouple must

be installed. There are 15 thermocouples of 5 different heights to be inserted inside the

reactor tubes.

Tubing or a string is to be used to guide the thermocouples so that the thermocouples

would be at the center of the tubes.The guiding rod is a hollow 10 mm instrument tubing

rod inserted into the tube; and the thermocouple is inserted into the hollow part of the

rod.

76

The thermocouples to be inserted inside tubing of slightly larger diameter and inserted

inside the reactor tubeIf string is used, the thermocouple need to be wrapped with the

string and the thermocouple is pull up inside the reactor tube using the string.

Thermocouples must be adjusted according to the height recommended by licensor and

properly tagged to ensure the right connection to DCS (Distributed Control System); but

in the actual situation, the thermocouples could not be adjusted after installation because

every 5 thermocouples (1 set) are tightened to each other.

It is very important for the thermocouples to be in an accurate height and radially centre,

to ensure the reliable readings and monitoring of catalyst activity during normal

operation.

As the thermocouples are inserted into the tubes, the bottom cover is simultaneously

closed, leaving a confined space for personnel inserting the thermocouples.

Figure 6.2: Installation of Thermocouple

77

Catalyst Loading

A plastic funnel connected with transparent host of 5000 mm length is used to load

the catalyst. This will avoid free fall of the catalyst and hence reduce the possibility of

broken catalyst. The catalyst is added little by little amount (piece by piece) to ensure

that the level of the catalyst loaded is not exceeding the limit.

Besides, bridging of catalyst in the tubes may happen if it is poured too fast. The

required height is obtained by level checking. The tubes which have been overloaded

with catalyst are emptied via vacuum and then reloaded again until the required height is

obtained.

Differential Pressure Test

The differential pressure (DP) test is carried out after the completion of level checking to

ensure the uniformity of the DP across the catalyst in every tube .Ideally, all tubes

should be checked for pressure drop after loading (or for equal flow at fixed upstream

pressure).

But, due to the time consuming in such checking, it is seldom done .As a minimum, it is

advisable to check a small fraction of the tubes. The equipment used for this test is a

differential pressure meter with instrument air supply at 0.5 bars.

300 tubes are selected randomly to perform the DP test, then the average reading is

taken and its standard deviation is calculated. For the rest of the tubes, any tubes that are

under/above the range compared to the calculated standard deviation is considered fail,

thus, the tube need to be reloaded. For the tubes with thermocouples, a different average

and standard deviation is used.

All data is recorded for future references.

78

Catalyst Blowing and Bottom Spool Installation

The reactor top cover is reinstalled as soon as the P test completed. The reactor is then

heated up by passing the heat transfer oil into the shell side of the reactor. The oil system

temperature is raised by 30oC every hour; until the temperature reaches 273 oC.

Once heating is done, the tube side of the reactor is blown to remove catalyst dust in the

tubes. Bottom spool is reinstalled after blowing is completed. The reactor now is ready

for start up.

79

CHAPTER 7

MINOR EQUIPMENT DESIGN 1: COMPRESSOR

Compressors are machines that compress air or gas. Compression is achieved through

the reduction of the volume that the gas occupies. Each compressor is generally a

function of the gas capacity, action and discharge head. There are four types of

compressors namely, centrifugal, axial, reciprocating and rotary.

Figure 7.1: Four types of compressor, centrifugal, axial, reciprocating and rotary

compressor (clockwise) (Saeid et al. 2006)

80

Centrifugal and axial-flow units are continuous flow compressors. Centrifugal

compressors use a rotating disk or impeller in a shaped housing to force the gas to the

rim of the impeller, increasing the velocity of the gas. A diffuser (divergent duct) section

converts the velocity energy to pressure energy. Centrifugal compressors are generally

used for higher pressure ratios and lower flow rates.

On the other hand, axial-flow compressors are dynamic rotating compressors that use

arrays of fan-like airfoils to progressively compress the working fluid. Axial-flow

compressors are used for lower-stage pressure ratios and higher flow rates. Axial-flow

compressors are mainly used as compressors for turbines. The pressure ratio in a single-

stage centrifugal compressor is about 1.2:1, while axial is 1.05:1 and 1.15:1.

Reciprocating compressors are generally used when a high-pressure head is requested at

a low flow rate. However, because of difficulty in preventing gas leakage and lubricating

oil contamination, reciprocating compressors are seldom used for compression of gases

requiring high purity.

Centrifugal compressor is preferred in this case where high pressures are required at

relatively low flow rates. Natural gas at 255C and 963.25 kPa is to be compressed to

1920 kPa before feeding into the primary reformer. A 1.99 pressure ratio is required.

Centrifugal compressor is preferred over axial-flow compressor as it is generally used

for higher pressure ratios. In industrial compressors, the compression path will be

polytropic where Pvn = constant (P = pressure, v = volume). The work required is given

by a general expression,

=

11

1

1

21

n

n

P

P

n

nT

M

RZW

Where;

W = Compressor work (kJ/hr)

Z = Compressibility factor

81

R = Gas constant (kJ/kgmol.K)

T1 = Inlet temperature of the stream (K)

P1 = Initial pressure (bar)

P2 = Final pressure (bar)

= v

p

C

C = 1.34

Compressor efficiencies are usually expressed as isentropic efficiencies, i.e., on the basic

of an adiabatic reversible process. Isothermal efficiencies are sometimes quoted, and

design calculations are simplified when isothermal efficiencies are used. The work of

compressor and single stage compressor can be calculated by assuming the compressor

is operated ideally under adiabatic compression.

Parameter for Calculation:

Mass flowrate = 74 476.21 kg/hr

Volumetric flow = 24 795.55 m3/hr = 9.665 m3/s

Inlet temperature, T1 = 403.3 K

Gas Constant, R (kJ/kgmol K) = 8.314 kJ/kmol.K

From ICON simulation, = v

p

C

C 1.34

Inlet pressure, Pl = 243.18 kPa (ambient)

Outlet pressure, P2 = 2837 kPa

Compressibility factor, Z = 0.9667

82

From Figure X,

Figure 7.2 Approximate polytrophic efficiency centrifugal and axial flow compressor

(Sinnot 2000)

Design Pressure = 1.035 x 2837.1 kPa

= 2936.4 kPa

For Centrifugal Compressor, at volumetric flow rate = 3.53 m3/s,

Compressor efficiency, Ep = 74%

For compression, Ep = polytropic work/actual work required

From Equation 3.38, Sinnot (2000),

Polytropic temperature exponent, m = Ep 1-

= 74.034.1

1-34.1

83

= 0.341

Polytropic exponent, n = m1

1

= 341.01

1

= 1.518

Work required, -W =

11

1

1

21

n

n

P

P

n

nZRT

=

1238646

2784204

1518,1

518.1)3.403)(314.8(9667.0

518.1

1518.1

= 12 467.34 kJ/kmol

Actual work required = 74.0

12467

= 16 847.76 kJ/kmol

Shaft power = hrkmolxkmol

kJ/86.1862

16847.76

= 31 385 032.06 kJ/hr

= 8 718 kW

Outlet temperature, T2 =

m

P

PT

1

21

= 932 K = 659 C

84

Table 7.1: Specification Sheet for compressor K-301

Compressor Data Sheet

Equipment No. (Tag) K-301

Description High Speed Centrifugal

Compressor

Sheet No. 1/1

GENERAL

COMPRESSOR TYPE Centrifugal No. OF UNITS 1

LUBRICATION METHOD Oil Free Flooded Forced Lubrication Lube Oil Console COOLING METHOD Air Cooled Water Cooled OPERATION MODE Continuous Parallel Intermittent Indoor Outdoor

OPERATING CONDITIONS & REQUIREMENTS

INLET FLOW RATE Normal 1.8 m3/s Maximum n/a

INLET TEMPERATURE 403 K

OUTLET TEMPERATURE 932 K

INLET PRESSURE 2.43 bar

OUTLET PRESSURE 28.37 bar

DESIGN PRESSURE 29.36 bar

MOLECULAR WEIGHT 39.97 kg/kmol

RELATIVE HUMIDITY 0.4% RH

SITE CONDITIONS/UTILITIES

AIR QUALITY Saliferous Salt Laden Corrosive ALTITUDE ABOVE SEA LEVEL 50 m

AMBIENT TEMPERATURE

Normal 28C

Max 32C

Min 25C

REQUIRE TROPICALIZATION Yes No REQUIRE WINTERIZATION Yes No

COOLING WATER SUPPLY Pressure n/a

Temperature n/a

COOLING WATER RETUN Pressure n/a

Temperature n/a

COOLING WATER FLOW RATE n/a

AUXILIARIES TO BE SUPPLIED

Electric Motor Driver Diesel Engine Driver

Gear Unit / Accessories Guards

Inlet Filter / Silencer Blow-Off / Silencer

Inter Cooler / Water Cooled After Cooler / Water Cooled

Inter Cooler / Air Cooled After Cooler / Air Cooled

Outlet filter / Accessories Dual Dryer / Accessories

Air Reservoir / Accessories Safety Relief Valves

Barring Gear Noise Abatement Shroud

Air Reservoir / Accessories

Common Skid (Compressors Package / Dryer /Filter/ Reservoir)

Spreader Bar and Sling Assembly

ELECTRIC MOTOR DRIVER

Motor Rated Power 8 718 kW

Winding Configuration Delta Star

Space heater Yes

Power kW

Voltage V

No Power Factor Safety Factor 5%

Motor Type Squirrel Cage Synchronous Operation Method Direct On Line Soft Starting Rotation Viewing at Motor Fan CW CCW Remarks and Notes :- Driver rated power shall be at least 110% of the maximum power absorbed by the compressor.

85

CHAPTER 8

MINOR EQUIPMENT DESIGN 2: PUMP

8.1 INTRODUCTION

The function of this pump (P-203) is to pump the water to acetic acid reactor

8.1 SELECTION OF THE PUMP TYPE

Pumps can be classified into general types:

i- Dynamic pumps, such as centrifugal pumps

ii- Positive displacement pumps, such as reciprocating and diaphragm pumps

A sketch showing the essential features of a diaphragm pump is shown in figure follows.

Diaphragm pumps are a type of reciprocating positive displacement pump in which

liquid is pumped by a reciprocating diaphragm, which is driven by a solenoid, a

mechanical drive, or a fluid drive. Other versions are air operated. Pump has inlet and

outlet valves.

86

Figure 8.1: Schematic diagram of basic element of a diaphragm pump

8.3 PROCESS DESIGN

Table 8.1: Properties of process streams of P-203

Suction Discharge

Pumping temperature 109 C 50.00 C

Viscosity, 0.000257139 Pa.s 0.00097574 Pa.s

Pressure 137.389 kPa 3 189 406 kPa

Density 951.7791 kg/m3 997.3112 kg/m3

Parameter of the piping

Length = 100m Area = 0.0157 m2

Diameter = 0.1m Volume = 1.57 m3

From ICON;

Liquid volume Flow rate = 17.176 m3/hr = 0.004771 m3/s

Mass Flow = 17130.43kg/hr = 3.925:X/s

87

4O)(P$, ] = )(7$O;7O 4O)(P$, ] = 0.004771%'/L0.0157%. = 0.3037%L

"O = aH] "O = 951.7791 0.3037 0.1 0.000257139 = 112412

This is turbulent flow as Re > 4000.

Table 8.2: Pipe roughness

Material Absolute roughness ,mm

Drawn tubing 0.0015

Commercial steel pipe 0.046

Cast iron pipe 0.26

Concrete pipe 0.3 to 3.0

The type of pipe chosen is commercial steel pipe. for commercial steel is 0.046mm.

D = 0.046 10K'0.1 = 4.6 10Kv Referring to Moody chart, at /D = 4.6x10-4 and Re = 112412, the friction factor, f =

0.022. Assume that the frictional pressure drop due to the changing flow direction and

cross sectional area of the pipe is negligible compared to the pressure drop due to the

roughness. The equation below is applied.

ha = (p2 p1) + (z2 z1) + (V22

V11)

2g

Where 1 and 2 indicate point of suction and discharge respectively.

88

The pressure drop in a pipe:

Pf = 8f /M.0 V 2

Pf = 8 x 0.022 x M999.M x 0.5 x 951.7791 x 0.30372

Pf = 7 725Pa = 7.725kPa

To determine head losses; where the loss coefficient, KL, which is defined as

KL = &+ =

u By rearranging:

hL = u x

.k hL =

._u_M.9.'9' x 9.'9'..M

hL = 0.8 m

To find the actual head rise, ha:

P = gha

ha = k = '9_.9M_M.M.M

ha = 326.87 m

To find the total head required, assume that z = 20m

Total head required is given by:

Total head = mk + k + z

89

Total head = '9_.9M9.9.. _M.M.M + '9_.9M_M.M.M+ 20

Total head = 354 m

Theoretical hydraulic power, W

= 0.163 x` = 0.163 9336.91000 0.005 354 = 0.2693:

To calculate the capacity of the pump to be used to obtained the efficiency,

Capacity = rRmUQRT-{-soT

Capacity = MM'9/_M.M/

Capacity = 18 m3/hr

We assume that the efficiency of the pump is 65%.

To calculate the shaft power driving the pump, Wshaft,

= m

Wshaft = m

= 9...9._

Wshaft = 0.414kW

90

Brake horse power:

BHP = m x M__9

BHP = 9...9._ x M__9

BHP = 0.0075 hp

The pressure at the inlet to a pump must be high enough to prevent cavitations from

occurring in the pump. Cavitations occurs when bubbles of vapor, or gas, from in the

pump casing. Vapor bubbles will from if the pressure falls b