che604_644_3

CONFIDENTIAL EH/APR 2010/CHE604/644

UNIVERSITI TEKNOLOGI MARA FINAL EXAMINATION

COURSE COURSE CODE EXAMINATION TIME

PLANT DESIGN AND ECONOMICS CHE604/644 APRIL 2010 3 HOURS

INSTRUCTIONS TO CANDIDATES

1.

2.

3.

This question paper consists of five (5) questions.

Answer ALL questions in the Answer Booklet. Start each answer on a new page.

Do not bring any material into the examination room unless permission is given by the invigilator.

Please check to make sure that this examination pack consists o f :

i) the Question Paper ii) a one - page Appendix 1 Hi) a four - page Appendix 2 iv) a seven - page Appendix 3 v) a one - page Appendix 4 vi) an Answer Booklet - provided by the Faculty

DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO This examination paper consists of 5 printed pages

Hak Cipta Universiti Teknologi MARA CONFIDENTIAL

CONFIDENTIAL 2 EH/APR 2010/CHE604/644

QUESTION 1

a) Dimethyl ether (DME) is used primarily as an aerosol propellant. It is miscible with most organic solvents, has a high solubility in water, and is completely miscible in water and 6% ethanol. Recently, the use of DME as a fuel additive for diesel engines has been investigated due to its high volatility (desirable for cold starting) and high cetane number. The production of DME is via the catalytic dehydration of methanol over an acid zeolite catalyst. The main reaction is

2CH.OH -+ (CH3)20 + H20 methanol DME

The production of DME is represented by the process flow diagram (PFD) and stream table shown in Appendix 2. Determine the following: i) The single pass conversion of methanol, ii) Overall conversion of methanol, iii) The yield of dimethyl ether.

(10 marks) b) Identification and definition of the recycle structure of the process is the third approach

proposed in hierarchical approach to conceptual process design. Explain each recycle structure possible in a chemical production process.

(10 marks)

QUESTION 2

a) A stream contains a mixture of liquid phase ethylene glycol and vapor phase of other chemicals are to be separated by using a horizontal separator. The operating pressure of the separator is 21 bar. Make a preliminary design for the separator.

Table 1 Stream properties

Properties

Ethylene glycol flowrate Ethylene glycol density

Other chemicals flowrate Other chemicals density

Value

10,000 kg/h 962.0 kg/m3 12,500 kg/h 23.6 kg/m3

(15 marks)



b) Reactive distillation is a process where the chemical reaction and product separation are carried out simultaneously in one unit, i) Explain the advantages of reactive distillation, ii) In which established processes, is reactive distillation usually used?

(5 marks)

QUESTION 3

For a new chemical production process, four streams must be cooled or heated.

Table 2 Process streams characteristics

Stream No.

1 2 3 4

mcp

kW/C

4.0 11.0 7.0 7.0

Temperature In (C)

100 250 400 600

Temperature Out (C)

550 500 120 300

By using the minimum number of exchanger algorithm for heat exchanger networks, assuming that only one hot and one cold utility are available and using a minimum approach temperature of 20C:

a) Determine the pinch temperatures and the minimum hot and cold utility duties. (5 marks)

b) Determine the minimum number of heat exchangers above and below the pinch. (4 marks)

c) Design the heat-exchange network above the pinch. (7 marks)

d) Design the heat-exchange network below the pinch. (4 marks)

QUESTION 4

a) You are working in a heat exchanger fabrication company and one of your client want to know the mid-2008 purchase cost of a stainless steel, shell and tube heat exchanger with the heat-exchange area of 1300 m2. From the information given by the client, the heat exchanger will be operated at working pressure of 5 barg. In order to make necessary preliminary estimation of the purchase cost wanted, your initial step is to check whether your company had previously made any heat exchangers similar to the one wanted by the client. After going through previous purchase orders, you found out the following data on similar heat exchangers (but designed for a shell side pressure of 25 barg) in stainless steel that were purchased back in 1993:



Table 3 Cost of heat exchangers

Heat-Exchange Area (m2)

500 1500

Purchase Cost ($) 30,000.00 64,700.00

(14 marks) b) Explain the difference between direct costs, fixed costs and general expenses. Give two

examples of each type of cost. (6 marks)

QUESTION 5

Consider a chemical process containing the following equipment:

Table 4 Purchase cost of equipment

Equipment

Pump P-901A/B Compressor C-901 Heat exchanger E-901 Heat exchanger E-902 Reactor R-901 Flash V-901 (contains vessel + heat exchanger) Tower T-901 Condenser E-903 Reboiler E-904 Total Purchased Cost of Equipment

Purchase Cost ($103)

5 750 75 45 250 125 450 70 105

1875

The annual cash flows start at the end of year 2 and are as follows:

Table 5 Cash flow data

Source of Cash Flow

Product revenue Raw material costs

Utilities + waste treatment costs Operating labor

Amount of Cash Flow ($106/year)

36.00 21.43 2.00 0.41



The criterion for profitability in your company has been set at 15% rate of return (aftertax) and a 10-year plant life should be assumed for economic evaluations. Assume that all the capital investments occurs at time 0; Lang factor = 4.8; land cost = 0; that the tax rate is 35%; that you will use MACRS depreciation; and a working capital equal to 0.1 of COMd at the end of year 1. Do you recommend construction of the above plant? Justify your answer quantitatively.

(20 marks)

END OF QUESTION PAPER


CONFIDENTIAL APPENDIX 1 EH/APR 2010/CHE604/644

1) Single - pass conversion =

Formula List

reactant consumed in reaction reactant fed to the reactor

ON ~ . reactant consumed in process 2) Overall conversion = reactant fed to the process

_. y. , , _ moles of reactant to produce desired product moles of limiting reactant rreacted

P/2

5) us= 0.15M,

a, K-$ 7) / =0 .5

8) Ca=KAa"

9) logI0 FP=Cl+ C2 log10 P + C3 (log10 P)2

10) FCIL=FLangCP

11) COMd = 0.1SOFC/^ + 2.73COL +1.23^ +Cwr+CPM)

12) Economical Length to Diameter Ratio for Several Pressure Ranges

Operating pressure, bar Length/diameter, LJDV 0-20 3 20-35 4 >35 5


CONFIDENTIAL APPENDIX 2(1) EH/APR 2010/CHE604/644

i I 11

Flow Table for OME Unit 200

Stream Number

Temp(C) Pressure (bar) Vapor fraction Mass flow (tonne/h) Mole flow (kmol/h) Component (kmol/h)

Dimethyl ether Methanol Water

Stream Number

Temp(C) Pressure (bar) Vapor fraction Mass flow (tonne/h) Mole flow (kmol/h) Component (kmol/h)

Dimethyl ether Methanol Water

9

89 10.4 0.148

10.49 328.3

130.5 64.9

132.9

1

25 1.0 0.0 8.37

2622

0.0 259.7

2.5

10

46 11.4 0.0 5.97

129.7

129.1 0.6 0.0

2

25 15.5 0.0 8.37

262.2

0.0 259.7

2.5

11

153 10.5 0.0 4.52

198.6

1.4 64.3

132.9

3

45 152 0.0

10.49 328.3

1.5 323.0

3.8

12

139 7.4 0.04 4.52

198.6

1.4 64.3

132.9

4

154 15.1 1.0

10.49 328.3

1.5 323.0

3.8

13

121 15.5 0.0 2.13

66.3

1.4 63.6 1.3

5

250 14.7 1.0

10.49 328.3

1.5 323.0

3.8

14

167 7.6 0.0 2.39

132.3

0.0 0.7

131.6

6

364 13.9 1.0

10.49 328.3

130.5 64.9

132.9

15

50 12 0.0 2.39

132.3

0.0 0.7

131.6

7

278 13.8 1.0

10.49 328.3

130.5 64.9

132.9

16

46 11.4 0.0 2.17

47.1

46.9 0.2 0.0

8

100 13.4 0.0798

10.49 328.3

130.5 64.9

1319

17

121 7.3 0.0 3.62

113.0

2.4 108.4

2.2

o o

o m

> -u -o m z g x jo

m x -u TO IO

o X m o> o 35

Pressure Factors for Process Equipment (Correlated from Data in Guthrie [1, 2] , and Ulrich [3])

Equipment Type

Compressors Drives

Evaporators

Farts*

Furnaces

Heat exchangers

Equipment Description

Centrifugal, axial, rotary, and reciprocating Gas turbine Intern, comb, engine Steam turbine Electricexplosion-proof Electrictotally enclosed Electricopen/drip-proof Forced circulation (pumped), falling film,

agitated film (scraped wall), short tube, and long tube

Centrifugal radial, and centrifugal backward curve

Axial vane and axial tube

Reformer furnace

Pyrolysis furnace

Nonreactive fired heater

Scraped wall

Teflon tube

c.

0 0 0 0 0 0 0 0 0.1578

0 0 0 0 0 0.1405 0 0.1017 0 0.1347 0 0.6072

13.1467 0

c*

0 0 0 0 0 0 0 0

-0.2992

0 0.20899 0 020899 0

-0.2698 0

-0.1957 0

-0.2368 0

-0.9120 -12.6574

0

c3 0 0 0 p 0 0 0 0 0.1413

0 -0.0328

0 -0.0328

0 0.1293 0 0.09403 0 0.1021 0 0.3327 3.0705 0

Pressure Range (barg) -

-

-

-

P

Pressure Factors for Process Equipment (Correlated from Data in Guthrie [1 , 2], and Ulrich [3]) (Continued) Equipment Type Equipment Description Ci Pressure Range (barg)

Heaters

Packing Process vessels Pumps

Bayonet, fixed tube sheet, floating head, kettle reboiler, and U-tube (both shell and tube)

Bayonet, fixed tube sheet, floating head, kettle reboiler, and U-tube (tube only)

Double pipe and multiple pipe

Hat plate and spiral plate Air cooler

Spiral tube (both shell and tube)

Spiral tube (tube only)

Diphenyl heater, molten salt heater, and hot water heater

Steam boiler

Loose (for towers) Horizontal and vertical Reciprocating

Positive displacement

Centrifugal

0 0.03881 0

-0.00164 0 0.6072

13.1467 -0 0

-0.1250 0

-0.4045 0

-0.2115 0

-0.01633 0 Z594072 0

0 -0.245382 0

-0.245382 0

-0.3935

0 -0.11272

0 -0.00627

0 -0.9120

-12.6574 0 0 0.15361 0 0.1859 0 0.09717 0 0.056875 0

-4.23476 0

0 O259016 0 0.259016 0 0.3957

0 0.08183 0 0.0123 0 03327 3.0705 0 0

-0.02861 0 0 0 0 0

-0.00876 0 1.722404 0 t 0-

-0.01363 0

-0.01363 0

-0.00226

P

Pressure Factors for Process Equipment (Correlated from Data in Guthrie [1, 2 ] , and Ulrich [3]) (Continued) Equipment Type

Towers Tanks

Trays

Turbines

Vaporizers

Equipment Description .

Tray and packed APIfixed roof APIfloating roof Sieve Valve Demisters Axial gas turbines Radial gas/liquid expanders Internal coils / jackets and jacket vessels

*Pressure factors for farts are written in terms of the pressure rise across +See Equation (A.2J.

C, CM

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

-0.16742 0.13428

i the fan, AP, where AP is measured in

c3 t

0 0 0 0 0 0 0 0 0.15058

kPa.

Pressure Range (barg)

P

Identification Numbers for Material Factors for Heat Exchangers, Process Vessels, and Pumps to Be Used with Fjgure A.18 (Continued)

Identification Number

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Equipment Type

Heat exchanger

Process vessels


Double pipe, multiple pipe. fixed tube sheet, floating head, U-tube, bayonet, kettle reboiler, scraped wall, and spiral tube

Air cooler Air cooler Air cooler Hat plate and spiral plate Flat plate and spiral plate Flat plate and spiral plate Flat plate and spiral plate Flat plate and spiral plate Horizontal, vertical (including towers) Horizontal, vertical (including towers) Horizontal, vertical (including towers) Horizontal, vertical (including towers) Horizontal, vertical (including towers) Horizontal, vertical (including towers) Horizontal, vertical (including towers)

Material of Construction

CS-shell/CS-tube CS-shell/Cu-tube Cu-shell/Cu-tube CS-sheU/SS-tube SS-shell/SS-tube CS-shell/Ni alloy tube Ni alloy, shell/Ni alloy-tube CS-shell/Ti-tube Ti-shell/Ti-tube CStube Altube SStube CS (in contact with fluid) Cu (in contact with fluid) SS (in contact with fluid) Ni alloy (in contact with fluid) Ti (in contact with fluid) CS SSclad SS Ni alloy clad Ni alloy Ticlad Ti

(continued)

o o z TI a m z

> o m z a ><

a.

m x

73 to o

O X m o> o

X a o a

c 3 < a

it 3 O o

>

Identification Numbers for Material Factors for Heat Exchangers, Process Vessels, and Pumps to Be Used with Figure A.18 (Continued)

o o z TI a m z

o o z

Identification Number

25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Equipment Type

Pumps


Reciprocating Reciprocating Reciprocating Reciprocating Reciprocating Reciprocating Positive displacement Positive displacement Positive displacement Positive displacement Positive displacement Positive displacement Centrifugal Centrifugal Centrifugal Centrifugal

Material of Construction

Cast iron Carbon steel Cu alloy SS Ni alloy Ti Cast iron Carbon steel Cu alloy SS Ni alloy Ti Cast iron Carbon steel SS Ni alloy

> "0 -a m z o X "3i

m x o 30 to o

O X


LU5

o I (0 "C Q>

2

12

11

10

9

8

7

6

5

4

3

2

1

0

"i I '

* ' J

'

1

'

^

1 1

1 r

, p.

'

"1

r-

r

i

i i

i r

-J L_ ,

_JL .

1

i r

_I rz

~~' Z J L _

'

_J C I

I F

,

0 10 20 30 40 Identification Number from Previous Table

Figure A.18 Material Factors for Equipment in previous table. Data from References [1,2,3,6,7, and 8]



Economic Indicators 2008 r 1 2007 I

mm\m&ma

CONFIDENTIAL APPENDIX 4 EH/APR 2010/CHE604/644

Depreciation Schedule for MACRS Method for Equipment with a 9.5-Year Class Life and a 5-Year Recovery Period [1]

Year

1 2 3 4 5 6

Depreciation Allowance (% of Capital Investment)

20.00 32.00 19.20 11.52 11.52 5.76


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