Maleic Anhydride - Process Design

PROCESS DESIGN OF MALEIC ANHYDRIDE PLANTBY WORIL TURNER DUDLEY VIJAYA KRISHNA BODLA

TABLE OF CONTENTS1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Introduction The five processes selected Product and Process Selected for Design Screening of Process Alternatives Material Balance Energy Balance Equipment Sizing Equipment Costing Heat Intergration Economic evaluation Environmental Analysis Conclusion

INTRODUCTIONThe process design project involves designing a process plant for producing a particular product. A list of five products are selected, then from that list one product is selected for the design project. Selection of the best process for the design from a list of alternatives is then done. Material and energy balances are done, equipment sizing and costing, and then an economic evaluation of the process. Different tools of process optimization were considered for cost savings. Heat integration is done for the process to calculate the additional heating or cooling required. An environmental analysis was also done to determine the environmental impact of effluent discharge streams.

Product Names

Raw Materials

Process References

Maleic Anhydride

n-butane and air

Huntsmann fixed bed maleic anhydride process, Kirk Othmer Encyclopaedia of Chemical Technology by Timothy R. Felthouse, Joseph C. Burnett, Ben Horrell, Micheal J. Mummey and YeongYeong-Jen Kuo Fermentation of sugars to produce citric acid, Shreves Chemical Process Industries 5th Edition by George T. Austin, page 598 Oxidation of ethylene to produce acetaldehyde, Shreves Chemical Process Industries

Citric Acid

Sucrose or dextrose

Acetaldehyde

Oxygen, water and ethylene

Ammonia

Nitrogen and Hydrogen

Ammonia process, Shreves Chemical Process Industries 5th Edition by George T. Austin page 306 Cinnamic aldehyde production by aldol condensation, Shreves Chemical Process Industries 5th Edition by George T. Austin page 494

Cinnamic Aldehyde

Water and aldol

PRODUCT SELECTEDThe unique nature of maleic anhydride's chemical structure results in a highly reactive and versatile raw material. Its unsaturated double bond and acid anhydride group lend themselves to a variety of chemical reactions. Maleic anhydride's largest use today is in the production of unsaturated polyester resins. Another significant use is in the manufacture of alkyd resins, which are in turn used in paints and coatings. Other applications where maleic anhydride is used include the production of agricultural chemicals, maleic acid, copolymers, fumaric acid, lubricant additives, surfactants and plasticizers. Future applications are anticipated to be numerous given the versatility and usefulness of the product.

REACTIONS INVOLVED C4H10 + 3.5 O2 ------- C4H2O3 + 4 H2O H = -1236 kJ/mol (-295.4 kcal/mol) (-

C4H10 + 6.5 O2 4 CO2 + 5 H2O H = -2656 kJ/mol (-634.8 kcal/mol) (-

C4H10 + 4.5 O2 4 CO + 5 H2O H = -1521 kJ/mol (-363.5 kcal/mol) (-

SCREENING OF PROCESS ALTERNATIVESThere are two predominant raw materials for producing maleic anhydride, nnbutane and benzene. Benzene however is a major environmental concern, because it is deemed as carcinogenic, so on environmental grounds, without even looking at raw material costs, benzene is rejected as the raw material for the maleic anhydride manufacture. The process is a high temperature process so all the components leaving the reactor are gases, so several separation options exist. The gases can be flashed, to recover water and maleic anhydride as liquids, while the other gases will remain in the vapor phase. We then consider separating water from maleic anhydride by exploiting the differences between their physical properties. A solvent can be used for the product recovery, by contacting the product gases with a liquid solvent and then separating the maleic anhydride from the solvent. A number of alternatives exist for the solvent. The conversion of butane is 85%, so recycling the unreacted butane is an option. It is decided to use a process in which a solvent is used for absorbing the maleic anhydride produced.

Process Flow sheetR1 9. Splitter Purge (92)

41

CM24. Condenser

42

C131 01 1. Mixer 1 2. Reactor 3. Absorber 32 5. Mixer 2 51 6. Distillationp 61

2 8162

C3 R171

7. Distillation

Final Column

CM1 HE1So

8. Mixer 3

C272

HE2

R2

R3

S

MASS BALANCE FLOW CHARTR1 9. Splitter Purge (92)

41 42

4. Condenser

31 01 1. Mixer 1 2. Reactor 2 3. Absorber 32 5. Mixer 2 5161

6. Distillationp

62

81 7. Distillation

71

Final Column

8. Mixer 3 So

72

S

MASS BALANCEAssume an inlet flow of 100 Kmol/h of butane Assume compressed air is fed in a ratio, where the amount of Oxygen is 1.5 times the amount required Using the yield of Maleic Anhydride, percentage conversion of butane and the reaction stoichiometry of the reaction material balance relations are written for the reactor For the side reactions, it is assumed that equal amounts of butane reacts to form Carbon Dioxide as for Carbon Monoxide Split factors are then specified for all the separation equipment as well as for the purge The absorber is specified to be an isothermal absorber It is assumed that the solvent entering the column doesnot contain any Maleic Anhydride For the absorber mass balance model, the Kremser equation is used to determine the number of stages, using the split factor for the key component recovery.

The remaining split factors for the other components are calculated from the Kremser relationship To solve the mass balance model, the flow sheet is partitioned into two modules and the recycle broken by tearing the inlet stream to the reactor. Once the component flows to the reactor are calculated, from the mass balance model, we can sequentially calculate all the other flowrates With the flowrates calculated, distillation column temperatures can be calculated. Temperature for the vapor leaving top of the column is found from a dew point calculation. The temperature in the condenser and reboiler is calculated from a bubble point calculation It is assumed that the distillation column operates at one atmosphere of pressure.

Component

01

1

2

31

32

41

42

51

61

62

71

72

Maleic Anhydride Succinic Anhydride

0.0

0.1

57.8

0.3

57.5

0.1

0.2

57.7

0.3

57.4

57.4

0.1

0.0

5.7

5.7

98.9

2243.7

7.1

91.8

2335.5

0.0

2335.5

2.3

2333.2

Nitrogen Oxygen Butane Carbon Dioxide

2238.0 525.0 100.0 0.0

11187.0 965.0 113.4 61.6

11187.0 550.5 17.0 77.1

11187.0 550.5 16.8 77.1

0.0 0.0 0.2 0.0

11187.0 550.5 16.7 77.0

0.0 0.0 0.1 0.0

0.0 0.0 0.3 0.1

0.0 0.0 0.3 0.1

0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0

Carbon Monoxide Water

0.0 0.0

61.7 284.2

77.1 424.1

77.1 375.2

0.0 48.9

77.1 355.2

0.0 20.0

0.0 68.9

0.0 68.6

0.0 0.3

0.0 0.3

0.0 0.0

Total (Kmol/h)

2863.0

12678.7

12396.4

12382.9

2350.4

12270.8

112.1

2462.6

69.2

2393.3

60.1

2333.3

Pressure(Kpa)

200.0

200.0

200.0

150.0

109.0

109.0

109.0

101.0

101.0

101.0

101.0

101.0

Temperature (K) Vapor Fraction

300.0 1.0

350.0 1.0

700.0 1.0

400.0 1.0

395.0 0.0

395.0 1.0

395.0 0.0

395.0 0.0

369.0 0.0

514.0 0.0

475.0 0.0

536.6 0.0

Components Maleic Anhydride

p

fs

S0 0.0

R1 0.1

92

Lo

57.3

0.1

0.0

Succinic Anhydride

0.0

2.3

1.3

5.7

1.4

2337.0

Nitrogen Oxygen Butane Carbon Dioxide Carbon Monoxide Water

0.0 0.0 0.0 0.0 0.0 0.3

0.0 0.0 0.0 0.0 0.0 0.0

0.0 0.0 0.0 0.0 0.0 0.0

8949.6 440.4 13.4 61.6 61.7 284.2

2237.4 110.1 3.3 15.4 15.4 71.0

Total (Kmol/h) Pressure(Kpa) Temperature (K) Vapor Fraction

57.7 101.0 474.6 0.0

2.4 101.0 532.9 0.0

0.0 101.0 394.0 0.0

9816.7 101.0 394.0 1.0

2454.2 101.0 394.0 1.0 0.0

ENERGY BALANCEThe heat contents of all the streams are evaluated and heating and cooling duties for all the heat exchangers in the process determined. Kinetic and potential energies are neglected, and only enthalpy changes for the streams are considered. It is assumed that there is no H of mixing, or pressure effects on H. A standard reference of 298 K and one 1 atm or 101 Kpa of pressure is chosen. The enthalpy of each stream is now considered in turn, using the following enthalpy correlations: To calculate the enthalpies of vapor mixtures the following correlation is used, Hv (T, y) = Hf + HT = k yk Hf, k (T1) + k yk Cpo, k (T) dT To calculate the enthalpies of liquid mixtures the following correlation is used, HLk (T) = Hof, k + Cpo, k (T) dT - Hkvap For the reactor the following expression is used, QR = 2 Hv (T, y2) 1 Hv (T, y1) QR is the heat of reaction, which is positive for an endothermic reaction and negative for an exothermic reaction. Hv (T, y2) = Hout and Hv (T, y1) = Hin With the stream enthalpies, and stream temperatures, the heating and cooling duties can now be calculated

Stream

0

1

2

31

32

41

42

R1

92

Flow (Kmol/h)

2863.0

12678.7

12396.4

12382.9

2350.4

12270.8

112.1

9816.7

2454.2

Pressure (Kpa)

200

200

200

150

150

109

109

200

101

Temperature (K)

300

372

619.3

400

400

393

393

393

393

Enthalpy (KJ/h)

-1.24E07

-8.9E07

-4.78E08

-1.45E08

-1.28E09

-9.62E07

-5.56E07

-7.66E07

-1.96E07

SizingAll the process equipments are sized for cost considerations based on the procedure given in the text book. Splitter is sized as a reverse mixer that the output flow is considered for sizing other than the input flow considered for mixers. For the heat exchangers the area of heat transfer and the amount of cooling water required have been calculated. The values of overall heat transfer coefficients are obtained from the book. Since nitrogen is the one carrying the maximum heat, it is considered as the main component from which heat has to be removed. Sizing of compressors is based on the assumption that the expansion is ideal, isentropic and adiabatic giving a Gamma value of 1.4 for an ideal system. Reactor Design is done by assuming a Space velocity or residence time and also that the reactor volume is twice that of the volume occupied by the catalyst.

SizingReactor:Reacto r Volume (m2) Outside tube diameter (m) Inside tube diameter (m) Inner cross sectional area (m2) Tube Length (m) Inside volume of each tube (m2) 0.003998 No. of tubes Outside surface area of each tube (m2) 0.669291

Multi Tubular

4.492676

0.035

0.02892

0.0006565

6.09

1123.625

Mixers:Mixer Fl (residence time) (1/hr) M1 M2 M3 2863 2462.5 2337 0,083333 0,083333 0,083333 Temp (K) Molar Density of the flow (kmol/m3) 188,1388 22,13813 15,38897 Volume (m3) Diamete r (m) Length (m) Area (m2)

372 399 399

2.53624 12.0502 15.1862

0,931295 1,565631 1,691115

3,725181 6,262522 6,764462

0,680838 1,924191 2,244998

Splitter:Fl (residence time) (1/hr) Temp (K) Molar Density of the flow (kmol/m3) Volume (m3) Diameter (m) Length (m) Area (m2)

Splitter

12270,8

0,033333

393

184,7362

4,42822

1,1214

4,48566 0,98719

Compressors:Compressor

P2CM1 (For stream R1) CM2 (For Air Compression)

P1 109 103,2

T1 393 298 1,4 1,4

9816,7 2763

W (kJ/hr) 2125869 4981751

c 0,8 0,8

m (Shaft driven) 0,9 0,9

Wb (shaft driven) (watts) 8,201658291 1,921971726

200 200

Heat Exchangers:Heat Exchangers Q U T1 T2 Delta Tln Area(A) (m2) Amount of cooling water(Km ol/hr) 14800 2100

HE1 HE2

8,38E+07 1,19E+07

919,8756 1430,922

619,3 536

400 400

163,6839 130,1257

556.5563 63.90984

Condenser:Condenser

Q

U

T1

T2

Delta Tln

Area(A) (m2)

Amount of cooling water (Kmol/hr)

C

2,64E+06

919,8756

400

394 54,39447

52,76186

467

For the distillation columns, the number of trays and the reflux ratio were determined by the method of Westerberg, assuming ideality. ICAS PDS was used to determine the number of trays for comparative checks. In cases where the method of Westerberg was giving a reflux ratio which when used in ICAS was giving tray number in excess of 100, the method of Underwood was used to determine the minimum reflux ratio and the heuristic of the reflux ratio being 1.2 * the minimum reflux ratio used to get the reflux ratio. An overall column efficiency of 80% is assumed. The column height is calculated using specified values for the tray spacing, extra feed space, disengagement space, skirt height and calculating the height of the tray stack from the number of trays and the value of the tray spacing. The column diameter is calculated by using the Souder Brown equation to determine the maximum allowable vapor velocity based on the column crosssectional area.

For the absorber and flash drum, number of theoretical stages calculated by the Kremser equation. Column efficiency is however much lower than distillation columns, generally around 20%, which was the figure used. The column diameter for the absorber is determined where total flows Vj and Lj are largest. This is at the bottom of the column. The diameter is then determined as for distillation column. The solvent recovery unit is a flash drum. The vapor velocity is calculated and is used to determine the column diameter as done for the absorber and the distillation column.

Column 1lk/hk

(avg) 25.33

N1 3.54

N2 3.54

lk ( lk) 0.995

hk (1- hk) 0.995

YN 0.8

NT 3.54

YR 0.8

R1 0.13

R2 0.13

R 0.13

Trays 7

Tray Stack 3.6

Extra Feed Space 1.5

Diseng Space 3

Skirt Ht 1.5

Total Ht 9.6

Bottom of the Column 1l (kg/m3) 920.29 g (Kg/m3) 2.59 V'(Kg/h) 13841.91 L' (Kg/h) 253198.29 b(dyne/cm ) 8.76 Flv 0.97 Csb 0.10 Uf(ft/s) 2.13 m/s 0.65 Db(m) 1.97

Top of the Column 1l (kg/m3) 923.27 g (Kg/m3) 0.61 V'(Kg/h) 2565.37 L' (Kg/h) 1282.68 b (dyne/cm) 0.16 Flv 0.01 Csb 0.29 Uf(ft/s) 4.25 m/s 1.04 Db(m) 1.93

Column 2lk/hk

(avg) 4.69

N1 16.29

N2 16.29

lk ( lk) 0.999

hk (1- hk) 0.999

YN 0.80

NT 16.29

YR 0.80

R1 0.85

R2 0.85

R 0.85

Trays 50

Tray Stack 24.5


Diseng Space 3

Skirt Ht 1.5

Total Ht 30.5

l(kg/m3) 568.87

g (Kg/m3) 2.27

V'(Kg/h) 87064.30

L' (Kg/h) 320560.95

Uv (m/s) 0.71555296

Dc (m) 4.35772

Column 3lk/hk

(avg) 4.31

N1 11.94

N2 17.53

lk ( lk) 0.99

hk (1- hk) 1.00

YN 0.80

NT 16.41

YR 0.80

R1 0.75

R2 0.94

R 0.90

N 20.51

Trays 20

Tray Stack 9.5


Diseng Space 3

Skirt Ht 1.5

Total Ht 15.5

l (kg/m3) 634.78

g (Kg/m3) 2.28

V' (Kg/h) 11536.25

L' (Kg/h) 11769.68

Uv (m/s) 0.75364887

Dc (m) 1.54079

Condensers and ReboilersCondenser No. Qc (kJ/hr) Tcond (K) Circulating Cooling water Tin (K) Tout (K) Amount (kmol) 97.4 509 552 Overall heat transfer Coefficient (U) (kJ/hr.m2.0K) 4292,767 1430,922 1430,922 Area (m2)

C1 C2 C3

3,82E+05 2,88E+06 3,12E+06

372 473,89 474,58

298 298 298

350 373 373

2.075829299 14.91611077 16.07479274

Reboiler No.

QB (kJ/hr)

Treb (K)

Circulating Steam Tin (K) Tout (K) Amount (kmol) 1010 1170 39.2

Overall heat transfer Coefficient (U) (kJ/hr.m2.0K) 4292,767 1430,922 1430,922

Area (m2)

R1 R2 R3

7,73E+07 8,73E+07 2,92E+06

468,93 536,54 532,92

1000 1000 1000

488,93 556,54 552,92

101.7213 131.6394 4.368935

AbsorberTrays 23 Tray Stack 11 Extra Feed Space 1.5 Diseng Space 3 Skirt Ht 1.5 Total Ht 17

l (kg/m3) 1157.01

g (Kg/m3) 1.28

V' (Kg/h) 351433.04

L' (Kg/h) 231038.67

Uv (m/s) 1.36

Dc (m) 4.23

Pumps Pump 1Right Elbows 2.00 Gate Valves 1.00 Ac (m2) 0.79

Leq 64.00

Leq 7.00

Check 1.00

Leq 170.00

Z1-Z2 4.00

I.D. (m) 1.00

Length 25.00

Velocity 7.06 5.69E-05

Re 1494573.9

e 4.60E-05

e/D 4.60E-05

R/ v2 1.50E-03

Hf 75.74

Ptotal (m) 79.74

Wp (KW) 87.15

Pump 2Right Elbows 2.00 Leq 64.00 Gate Valves 1.00 Leq 7.00 Check 1.00 Leq 170.00 Z1-Z2 25.00 I.D.(m) 1.00 Ac(m2) 0.79 Length 25.00

Velocity 8.977745 1.56E-05

Re 5.42E+06

e 0.000046

e/D 4.60E-05

R/ v2 0.001125

Hf 79.13129

Ptotal (m) 104.13129

Wp (KW) 113.2027

Pump 3Right Elbows 2 Gate Valves 1 Ac (m2) 0.021 029

Leq 10.47

Leq 1.15

Check 1

Leq 27.82

Z1-Z2 6.5

I.D. (m) 0.16

Length 25


Re 2.51E+07

e 0.000046

e/D 2.81E-04

R/ v2 1.75E-03

Hf 162.89

Ptotal (m) 169.39

Wp (KW) 4.51

Pump 4Right Elbows 2 Leq 64.00 Gate Valves 1 Leq 7.00 Check 0 Leq 0.00 Z1-Z2 0 I.D. (m) 1.00 Ac (m2) 0.7855 Length 25


Re 8.27E+07

e 0.000046

e/D 4.60E-05

R/ v2 1.25E-03

Hf 11.86

Ptotal (m) 11.86

Wp (KW) 12.58

Pump 5Right Elbows 0 Leq 0.00 Gate Valves 1 Leq 0.15 Check 0 Leq 0.00 Z1-Z2 0 I.D. (m) 0.02 Ac(m2) 0.00038 Length 25

Velocity 10.11 5.90E-05

Re 3.54E+04

e 0.000046

e/D 2.09E-03

R/ v2 2.75E-03

Hf 1230.65

Ptotal (m) 1230.65

Wp (KW) 0.73

Pump 6Right Elbows 2 Leq 64.00 Gate Valves 1 Leq 7.00 Check 1 Leq 170.0 0 Z1-Z2 14 I.D. (m) 1.00 Ac (m2) 0.7855 Length 25


Re 1.40E+06

e 0.000046

e/D 4.60E-05

R/ v2 2.75E-03

Hf 176.27

Ptotal (m) 190.27

Wp (KW) 202.10

Costing and Project EvaluationDistillation Columns, Flash Drum and Absorber Column # 1 2 3 4 5 6 7 Height (Ft) 31.68 91.5 51.15 56.1 56.1 56.1 56.1

Type D. C D. C D. C Abs Abs F.D. F.D.

Diameter 3.531 14.52 5.082 13.959 13.959 14.025 14.025

BC($US) 6342.824 66095.23 13704.26 42668.86 42668.86 42880.72 42880.72

UF 3.86261 3.86261 3.86261 3.86261 3.86261 3.86261 3.86261

MF 4.23 4.23 4.23 4.23 4.23 4.23 4.23

MPF 1 1 1 1 1 1 1

BMC($US) 103634.4 1079919 223911.6 697159.4 697159.4 700620.9 700620.9

Stack Ht 11.88 80.85 31.35 36.3 36.3

BC 485.068 24214.76 2108.044 10517.86 10517.86

UF 3.862609 3.862609 3.862609 3.862609 3.862609

MF 1 1 1 1 1

MPF 1.4 1.4 1.4 1.4 1.4

BMC($US) 2623.079 130945 11399.57 56876.9 56876.9

Total($US) 106257.44 1210864.1 235311.14 754036.34 754036.34

Heat Exchangers

HX Reactor H1 H2 H3 C1 C2 C3 R1 R2 R3

Area(ft2) 8094.5 5930 688 570 26.36 63.14 83.14 1095.00 1417.00 47.40

BC($US) 35314.62 28848.06 7113.175 6294.332 311.4985 318.0975 320.2053 9621.664 11376.83 315.9157

MF 3.29 3.29 3.29 3.29 1.83 1.83 1.83 3.29 3.29 1.83

MPF 2.529 2.529 0.85 0.85 0.85 0.85 0.85 2.529 2.529 0.85

UF

BMC

Total $1,756,010.1 8

3.862609 657343.2 3.862609 536975.2 3.862609 86272.79 3.862609 76341.38 3.862609 2021.371 3.862609 2064.192 3.862609 2077.871 3.862609 179096.8 3.862609 211767.4 3.862609 2050.035

Pumps

Capacity

# 1 2 3 4 5

(Hp) 117 150 6.0434 17 1

D (inches) 39 39 6 39 1

Cost ($US) 34917.21 34917.21 11823.23 34917.21 4419.90

Motor ($US) 7675.11 9908.91 911.52 1319.25 369.21

a1 4.81 5.41

a2 0.510 0.312

a3 0.05 0.10

HP 7.5-250 1-7.5

Total Cost 42592.324 44826.124 12734.749 36236.466 4789.1126

6

271

39

34917.21

18687.5 Total

53604.726 $194,783.5

CompressorsNumber 1 2 Capacity 11 2 BC($US) 4203.395 1131.152 MF 3.11 3.11 MPF 1 1 UF 3.862609 3.862609 BMC 50494.18 13588.2 Total $64,082.38

Mixers and SplittersMixer/Splitter

Area 7.32 20.71 24.16 10.62

Height 12.22 20.54 22.19 14.71

Diameter

BC ($US) 2518.5 4182.2 4789.6 3548.2

UF 3.8626 3.8626 3.8626 3.8626

MF 4.23 3.18 3.18 4.23

MPF 1 1 1 1 Total

BMC($US) 41149.506 51370.603 58831.994 57975.006 209327.11

1 2 3 4

3.055 5.13 5.54 3.67

Costing of entire ProjectFix Capital Equipment + PI 10,864,669.30 Building and Site 4,345,867.72 Working Capital 2,950,844.18 Capital Investment Fixed and Working Capital 18,161,381.21

Raw Materials n-Butane Succinic Anhydride Maintenance Labour Manager Insurance Lab Analyses Steam Cooling Water Plant Overheads Taxes

Unit Kmol/h Kmol/h % Plant Cost $US/man*yr $US/man*yr %Plant Cost $US/man*yr

Amount 876000 11563.2 5 15 1 2 1 0

Price ($US) 2.3481692 800.592

Total 2,056,996.22 9,257,405.41 908,069.06

40000 200000

600,000.00 200,000.00 363,227.62

70000 0 0.017488189

70,000.00 0 177462.8666 300000 304210.7405

$US/Kmol/h %Labour Cost % Fix Capital

10147584 50 2

Total Operating Cost Revenue $US(Kmol Product/h) 501948 44.1261 Profit After Tax

14,237,371.93 22,149,007.64 7,911,635.72

ROI 0.435629627

Pay out Time 2.210530747

NPV 56,420,932.00

Rate of Return (NPV = 0) $0.00

IRR 0.43562

NPV = 0 2E-07

N 2.7

i 0.1

ECONOMIC EVALUATIONWith all the equipment size and cost, we now proceed to assess the economic viability of the project The capital investment is calculated. The capital Investment which is all the cost incurred at the beginning of the plant life is composed of two components: Fix capital and working capital. The equipment cost plus 25% contingency, represents a part of the fix capital investment. The other component is the cost for building and site, this is generally 40% of the bare module cost The working capital is all the funds require to operate the plant due to delays in payment and maintenance of inventories The other cost to consider is the cost of operating the plant. These costs are continuous over the entire life of the plant. These costs are broken down into the following parts: Raw material costs

Cost of utilities Labour Supervision Laboratory analyses Maintenance Plant Overheads/Supplies e.g. Office supplies and spares and sales costs etc. Taxes Insurance The net revenue generated by operating the plant, will be the amount made by selling the product produced, minus all the operating expenses Steam utility and electricity was not included in utility cost, because with heat integration, it was obvious that there are large amounts of heat available for the process that could be used for generating steam and electricity to operate the plant The project was evaluated in terms of the following markers: Net Present Worth An internal rate of return, IRR, also refers to as the minimum attractive rate of return, MARR, was computed The minimum payback period, at NPV = 0 was computed

The process is found to be highly profitable The MARR is 43.5%, well above the 10% interest rate used for computing the NPV. Pay back period is computed to be 2.7 years NPV is computed to be highly positive

Sensitivity AnalysesSensitivity analyses were done, using the following markers: A sharp increase in raw material cost. A 50% increase in the price of butane was used. The process remained profitable A 50% decrease in product price. The product was no longer profitable. This indicates that the profitability of the process is highly sensitive to sale price of the product. The minimum price the product can be sold for and the process remains profitable is $32.5/Kmol. This represent a 26% decrease in current selling price. High increase in interest rates. If the interest rates exceeds the MARR, then the process no longer remains profitable. Doing the analyses with an interest rate of 50%, the process becomes highly non-profitable, with a nonhighly negative NPV and a pay back period of over a hundred years.

Sensitivity analyses1) A sharp increase in raw material cost. A 50% increase in the price of butane was used.Raw Materials n-Butane Succinic Anhydride Maintenance Labour Manager Insurance Lab Analyses Steam Cooling Water Plant Overheads Taxes $US/Kmol/h %Labour Cost % Fix Capital Unit Kmol/h Kmol/h % Plant Cost $US/man*yr $US/man*yr %Plant Cost $US/man*yr Amount 876000 11563.2 5 15 1 2 1 0 10147584 50 2 Total Op. Cost Revenue $US (Kmol Product/h) 501948 44.1261 Profit After Tax 70000 0 0.017488189 40000 200000 Price ($US) 3.5222538 800.592 Total 3,085,494.33 9,257,405.41 908,069.06 600,000.00 200,000.00 363,227.62 70,000.00 0 177462.8666 300000 304210.7405 15,265,870.03 22,149,007.64 6,883,137.61

ROI 0.379

Pay out Time 2.526854178

NPV 46,725,368.29

NPV = 0(IRR) ($0.00)

IRR 0.37897

NPV = 0 5.59E-08

N 3.2

i 0.1

2) A 50% decrease in product cost.

Raw Materials n-Butane Succinic Anhydride Maintenance Labour Manager Insurance Lab Analyses Steam Cooling Water Plant Overheads Taxes

Unit Kmol/h Kmol/h % Plant Cost $US/man*yr $US/man*yr %Plant Cost $US/man*yr $US/Kmol/h %Labour Cost % Fix Capital $US (Kmol Product/h)

Amount 876000 11563.2 5 15 1 2 1 0 10147584 50 2

Price ($US) 2.3481692 800.592 40000 200000 70000 0 0.017488189

Total 2,056,996.22 9,257,405.41 908,069.06 600,000.00 200,000.00 363,227.62 70,000.00 0 177462.8666 300000 304210.7405

Total Op. Cost Revenue 501948 22.06305 Profit After Tax

14,237,371.93 11,074,503.82 -3,162,868.10

3) High increases in interest ratesRaw Materials n-Butane Succinic Anhydride Maintenance Labour Manager Insurance Lab Analyses Steam Cooling Water Plant Overheads Taxes $US/Kmol/h %Labour Cost % Fix Capital $US (Kmol Product/h) Unit Kmol/h Kmol/h % Plant Cost $US/man*yr $US/man*yr %Plant Cost $US/man*yr Amount 876000 11563.2 5 15 1 2 1 0 10147584 50 2 Total Op Cost Revenue 501948 44.1261 Profit After Tax 70000 0 0.017488189 40000 200000 Price ($US) 2.3481692 800.592 Total 2,056,996.22 9,257,405.41 908,069.06 600,000.00 200,000.00 363,227.62 70,000.00 0 177462.8666 300000 304210.7405 14,237,371.93 22,149,007.64 7,911,635.72

NPV -2,338,192.29

Heat IntegrationTin (K) 619.3 536 298 298 298 298 298 1000 1000 1000 400 298 Tout (K) 400 400 373 373 350 373 373 488.93 556.54 552.92 394 373 Enthalpy in (kJ) 9.84E+06 -5.05E+08 0 0 0 0 0 8.10E+07 8.10E+07 8.10E+07 3.83E+07 0 Enthalpy out (kJ) 3.07E+06 -5.56E+08 1.59E+07 1.59E+07 1.19E+07 1.59E+07 1.59E+07 6.34E+07 6.57E+07 6.55E+07 3.56E+07 1.59E+07 Available Heat -6.77E+06 -5.10E+07 1.59E+07 1.59E+07 1.19E+07 1.59E+07 1.59E+07 -1.76E+07 -1.53E+07 -1.54E+07 -2.70E+06 1.59E+07

No. 1 2 3 4 5 6 7 8 9 10 11 12

Streams u2 Lo He1cooling water He2cooling water C1 C2 C3 R1 R2 R3 u31 Ccooling water

Condition Hot Hot Cold Cold Cold Cold Cold Hot Hot Hot Hot Cold

Flow 12396.4 2336.97 14800 2100 67.6 509 552 15900 18000 602 12396.4 467

The PA tool box of ICAS was used to generate the Pinch Diagrams after giving all the streams input data. The Diagrams shows an additional cooling of 1.0811E11 kJ/hr. So this is the amount of excess heat which can be used for other purposes. The pinch point is at 394K for the hot stream and 383K for the cold stream obtained from the cascade diagram. The results shows an additional of 3 heat exchangers are needed to satisfy the condition. The heat duties have been added up and found that the process has excess heat than required in the process. This can be attributed to the highly exothermic reactions in the reactor.

Environmental Impact AnalysisStreams In 01 S0 Streams Out 92 61 p

Total PEI Input Sum Output Sum Impact Generated 8740.31 12064.7 3324.36

HTPI 1696.89 5060.28 3363.39

HTPE 0.90263 1668.93 1668.02

ATP 448.692 98.6746 -350.017

TTP 1696.89 5060.28 3363.39

GWP 0 0.21655 0.21655

ODP 0 0 0

PCOP 4896.93 176.289 -4720.64

AP 0 0 0

Analysis: The Report generated gives a higher value of the Total Potential Environmental Impact suggesting that the process has to be modified for environmental purposes. The high value of the PEI is because of the excess amounts of carbon dioxide released into the atmosphere. By analyzing all the individual output streams, it can be clearly observed that output stream 3 has quiet high values of the total PEI. It is because of the release of the purge gas from the splitter directly into the atmosphere. As a process improvement step, we can use incinerator to convert the Carbon monoxide to carbon dioxide before it is released into the atmosphere. As an alternative a scrubber can be used to scrub all the harmful gases and prevent them from entering into the atmosphere. The other 2 outlet streams mostly contain water other than the product, so they have less environmental impact. Changing the solvent in the absorption column from Succinic anhydride to water can increase the environmental attractiveness of the process but the required product yield cannot be attained.

Documents

Maleic Anhydride - Process Design