Heat Integration-Chap4a Lecture

8/12/2019 Heat Integration-Chap4a Lecture

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Application of PINCH Analysis Software

CBB 4313 HEAT INTEGRATION

So far, you have been taught on how to determine the energy target and design the heat exchanger

network that will attain it respectively

Temp.

Enthalpy (H)

QC

QH

DTmin

COLD UTILITIES

HOT UTILITIES

PINCH

POINT

Composite Curve Problem Table Algorithm

and Heat Cascade Diagram

alternatives

HOT 1

HOT 2

COLD 1

COLD 2

180 C 80 C

130 C 40 C

30 C120 C

60 C100 C

Cp Q

20

40

36

80

2000

3600

3240

3200

8002400

1080

70 C 43 C

60 C

2000

160120

90 C

115.56 C

PINCH

Energy Targeting

Maximum Energy Recovery Design


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CBB 4313 HEAT INTEGRATIONCBB 4313 HEAT INTEGRATION

Now we will learn on how to use a software that can perform the PINCH Analysis ..

The software is called STARand was developed by University of Manchester


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Let us suppose we do the data extraction for the process below .

R1

S1S2

CW

FEED

T = 30 C

T = 200 C T = 350 C

BOILER FEED WATER

MP STEAM

T = 220 C

T = 90 C

MP STEAM

T = 220 C

T = 100 C

T = 250 C

T = 150 C

T = 60 C

T = 130 C

T = 150 C

T = 180 C

T = 120 C

MP STEAM

T = 220 C

T = 150 C

CW

T = 40 C

PROD 1

T = 60 C

PROD 2

T = 40 C

PROD 3

T = 40 C

CWCW

LP STEAM

T = 120 C


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So where are the streams ?

R1

S1S2

CW

FEED

T = 30 C

T = 200 C T = 350 C

BOILER FEED WATER

MP STEAM

T = 220 C

T = 90 C

MP STEAM

T = 220 C

T = 100 C

T = 250 C

T = 150 C

T = 60 C

T = 130 C

T = 150 C

T = 180 C

T = 120 C

MP STEAM

T = 220 C

T = 150 C

CW

T = 40 C

PROD 1

T = 60 C

PROD 2

T = 40 C

PROD 3

T = 40 C

CWCW

LP STEAM

T = 120 C


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FEED30 C200 C

S1 REB130.1 C 130 C

130 C150 C S1 EFF

180.1 C 180 C S2 REB

350 C 100 CREACTOR EFF.

S1 COND60.1 C 60 C

180 C 40 C PROD 3

S2 COND120.1 C 120 C

120 C PROD 240 C

UTILITIES : COOLING WATER, MP STEAM AND LP STEAM

These are the set of streams extracted from the process flowsheet.

H (Enthalpy change)

2,500 kW

3,000 kW

1,200 kW

2,000 kW

600 kW

2,500 kW

3,500 kW

150 kW

2,300 kW


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To start with, go to the file option and click new.


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Go to the edit menu .

Click at stream data



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You will be required to fill up all the streams data



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After filling up the stream data click ok



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Go to the target menu .

Set your DTmin.



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As you change your DTmin, the energy target for hot and cold utility will also vary

The energy target for the

two utilities.



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You can also go back to the target menu, and select to see the problem table, composite curve, grand composite

curve and design grid .



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Composite Curve



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Problem Tableactually heat cascade



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Grand Composite Curve



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Design Grid representing stream data.



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Another software that can be used is called SPRINTand was also developed by the University of

Manchester.



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In order to input the stream data, similar steps as applied in STAR is used.



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You can basically obtain the same information for the MER target - Problem table, Composite

Curve, Grand Composite Curve, Design Grid etc.

You will also need to set the DTmin.



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Consider the flowsheet for the Phthalic Anhydride Production Process below,

Perform the stream extraction exercise



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Process Descr ip t ion

The phthalic anhydride is manufactured using controlled oxidation of o-xylene. The reaction uses a fixed bed

vanadium pentoxidetitanium dioxide catalyst. The reaction is carried out in vapour phase at a temperature

range of 380400 C. Reaction is exothermic. Reactor cooling is by means of a molten salt loop.

Air and o-xylene are heated and mixed in a venturi where the o-xylene vapourises. The gaseous reactor

product is cooled first by boiler feedwater before entering a cooling water condenser. The phthalic anhydride

forms a solid on the condenser tube walls and is cooled to 70 C. Periodically the condenser is taken off line and

the phthalic anhydride melted off the surface by recirculation of high pressure hot water. Two condensers are

used in parallel. The noncondensible gases contain small quantities of byproducts and traces of phthalic

anhydride are scrubbed prior to venting it to atmosphere.

The crude phthalic anhydride is heated and held at 260 C to allow some byproduct reactions to go to

completion.

Purification is by continuous distillation in two columns. In the first column, maleic anhydride, benzoic and toluic

acids are removed as the overhead. Pure phthalic anhydride is removed as the overhead in the 2ndcolumn

while the high boiling residues are removed as the bottoms.



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The hot stream locations


1

2

3

45



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The hot streams on grid diagram .

Reactor Cooling377 C 375 C

376 C 180 C

180 C 70 C

280 C 279 C

197 C 196 C

Reactor Product Cooling

Product Sublimation

Column 1 Condenser

Column 2 Condenser

H

-7000

-3600

-2400

-400

-800



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1

2

6

3 4

5

Next, lets work out the cold stream .



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Air Feed

O-xylene Feed

Product Melting

Holding Tank Feed

Column 1 Reboiler

H

200

1600

900

200

400

Column 2 Reboiler 700

160 C 60 C

130 C 20 C

180 C 70 C

260 C 160 C

291 C 290 C

236 C 235 C

The cold streams on grid diagram .



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Overall

Reactor Cooling377 C 375 C

376 C 180 C

180 C 70 C

280 C 279 C

197 C 196 C

Reactor Product Cooling

Product Sublimation

Column 1 Condenser

Column 2 Condenser

H

-7000

-3600

-2400

-400

-800

Air Feed

O-xylene Feed

Product Melting

Holding Tank Feed

Column 1 Reboiler

200

1600

900

200

400

Column 2 Reboiler 700

160 C 60 C

130 C 20 C

180 C 70 C

260 C 160 C

291 C 290 C

236 C 235 C


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Stream Data Entry



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i. The Composite Curve



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ii. Problem Table (Heat Cascade)



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iii. Grand Composite Curve



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iv. Grid Diagram

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Heat Integration-Chap4a Lecture

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