Process Engineering

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Table of content

Introduction

Calculation

C T o 10 m in   Stream Ts (°C) Tt (°C) Q (kW) CP (kW/°C) T*s (°C) T*t (°C) No Type 4-6/1 Cold 35.5 150 2,567.8244 22.4 40.5 155 5-7/2 Cold 126.3 150 91.7826 3.9 131.3 155 13-14/3 Cold 80 102 2,934.5150 133.4 85 107 19-20 /4 Hot 62.2 35 -482.4474 17.7 57.2 30

For Hot Stream T*= T -

2

m in

T



For Cold Stream T*= T + 2 m in T 

T



∑ Hinterval 155 0 131.3 1 2 23.7 26.3 623.31 107 24.3 22.4 544.32 85 3 22 155.8 3427.60 27.8 22.4 622.72

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3 57.2 4 40.5 16.7 4.6 76.82 30 10.5 -17.8 -186.90

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4 Cascade diagram

First cascade

Second cascade

155 0 5294.77 623.31 131.3 -623.31 4671.46 544.32 107 -1167.63 4127.14 3427.60 85 -4595.23 699.54 622.72 57.2 -5217.95 76.82 76.82 40.5 -5294.77 0 -186.90 30 5107.87 186.90 Tpinch* = 40.5 0C Tpinch hot =45.50C Tpinch cold =35.50C QHmin =5294.77 kW Qcmin =186.90 kW

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5

Heat Exchanger Network (HEN)

CP 62.2°C 45.5°C 35°C 17.7 150°C 35.5°C 22.4 150°C 126.3°C 35.5°C 3.9 102°C 80°C 35.5°C 133.4

CPH < CPC (above pinch) CPH > CPC (below pinch) 17.7 < 133.4 22.4 17.7 3.9 17.7 2 3 4 1 295.59 1 1 H H H C 2639.21 1 92.43 2564.8 186.9

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6

Feasibility Study

Q=CP

ΔT 295.59=133.4(T-80) T=82.22°C T (°C) T (°C) 82.22 62.2 80 ΔT= 20.02 45.5 ΔT= 34.5 Feasibility ΔT1 = 82.22-62.20=20.02°C ΔT2 = 80.00-45.5-=34.50°C

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7 Selection of the utilities

Grand Composite Curve Medium pressure Low pressure

Cooling water

The most common heat utility is steam and available at several levels (Smith, 2009, p. 372). The levels address as low pressure, medium pressure, high pressure and very high pressure steam. Table 1 shows the typical steam available for hot utilities and the shifted temperature for the ΔTmin= 20OC 0 20 40 60 80 100 120 140 160 180 0 1000 2000 3000 4000 5000 6000 T sh ifted H

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8

Table 1: Typical steams available for hot utility (Venkatesan, V., 2008).

No. Steam for heating Pressure (Psig) Temperature (°C) Temperature Shifted (°C)

1 Low Pressure >50 130 120

2 Medium Pressure 50 - 250 230 – 280 220

3 High Pressure 250 350 340

4 Very High Pressure >600 500 490

Usually for the cold utilities, refrigeration, cooling water, air-cooling are used for the cold utilities and there are more cold utilities that not been mentioned.

Table 2: General information of typical refrigerant available for cold utility (Application guide-refrigerants, 2012).

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Table 3: Operation information of typical refrigerant available for cold utility (Application guide-refrigerants, 2012).

So, in this process, we used cooling water as the cold utilities since it has 100oC boiling point and the temperature below the pinch is below 40 oC.

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10 SAVING

In terms of the amount (kW and %) For hot utility

QH before = 482.4474 KW QH after = 5294.77 KW

Saving = (482.4474 - 5294.77) KW × 100 % 482.4474 KW

= 997.48%

For cold utility

QC before = 2567.8244 + 91.7826 + 2934.5150 KW = 5594.122 KW QC after = 186.9 KW Saving = (5594.122 – 186.9) KW × 100 % 5594.122 KW = 96.66%

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11

Simulation

SIMULATION BY USING ASPEN PLUS

C1

C2

C3

H1

4

5

7

13

14

19

20

6

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12 STREAM TABLE

FORMALIN P RODUCT ION

Stream ID 4 5 6 7 13 14 19 20

From C1 C2 C3 H1

T o C1 C2 C3 H1

Phase LIQUID VAPOR VAPOR VAPOR MIXED VAPOR MIXED MIXED

Subst ream: MIXED

Mole Flow kmol/sec

METHANOL .0560555 0.0 .0560555 0.0 6.98611E-3 6.98611E-3 6.94444E-5 6.94444E-5 W AT ER 8.86111E-4 0.0 8.86111E-4 0.0 .0886777 .0886777 .1369305 .1369305 OXYGEN 0.0 .0274250 0.0 .0274250 0.0 0.0 0.0 0.0 NIT ROGEN 0.0 .1036056 0.0 .1036056 0.0 0.0 0.0 0.0 CH2O 2.77778E-6 0.0 2.77778E-6 0.0 .0485111 .0485111 .0485083 .0485083 T otal Flow kmol/sec .0569444 .1310306 .0569444 .1310306 .1441750 .1441750 .1855083 .1855083 T otal Flow kg/sec 1.812188 3.779919 1.812188 3.779919 3.278013 3.278013 3.925592 3.925592 T otal Flow cum/sec 2.31902E-3 1.972754 .9838637 2.306237 1.653269 3.798914 .5374885 .5027440 T emperature K 308.6500 399.4500 423.1500 423.1500 353.1500 375.1500 335.3500 308.1500 Pressure N/sqm 2.41317E+5 2.20632E+5 1.99948E+5 1.99948E+5 1.37895E+5 1.17211E+5 2.65448E+5 2.44764E+5 Vapor Frac 0.0 1.000000 1.000000 1.000000 .5454918 1.000000 .2825654 .2664842 Liquid Frac 1.000000 0.0 0.0 0.0 .4545082 0.0 .7174346 .7335158 Solid Frac 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Ent halpy J/kmol -2.4082E+8 2.95694E+6 -1.9572E+8 3.65740E+6 -2.1272E+8 -1.9237E+8 -2.3740E+8 -2.4000E+8 Ent halpy J/kg -7.5671E+6 1.02502E+5 -6.1502E+6 1.26784E+5 -9.3561E+6 -8.4609E+6 -1.1219E+7 -1.1341E+7 Ent halpy W at t -1.3713E+7 3.87449E+5 -1.1145E+7 4.79232E+5 -3.0669E+7 -2.7735E+7 -4.4039E+7 -4.4522E+7 Ent ropy J/kmol-K -2.4376E+5 6333.582 -1.1666E+5 8855.751 -84066.30 -26807.96 -1.2029E+5 -1.2818E+5 Ent ropy J/kg-K -7659.544 219.5530 -3665.845 306.9838 -3697.441 -1179.079 -5684.661 -6057.519 Density kmol/cum 24.55540 .0664201 .0578783 .0568157 .0872059 .0379516 .3451392 .3689916 Density kg/cum 781.4459 1.916062 1.841910 1.638998 1.982746 .8628816 7.303584 7.808332 Average MW 31.82379 28.84762 31.82379 28.84762 22.73635 22.73635 21.16127 21.16127 Liq Vol 60F cum/sec 2.27709E-3 7.01771E-3 2.27709E-3 7.01771E-3 3.86992E-3 3.86992E-3 4.46178E-3 4.46178E-3

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13

Conclusion

References

Smith, R. (2009). Chemical Process Design. West Sussex, England: John Wiley & Sons Ltd. Venkatesan, V. (2008). How do you define steam? Retrieved May 06, 2013 from