Pinch technology series 1

By:

Anwaruddin Hisyam

An Introduction to An Introduction to

Heat Exchanger Network (HEN) Heat Exchanger Network (HEN) DesignDesign

Pinch technology series 2

In this lecture we will learn how to set energy recovery targets for a process.

Pinch technology series 3

Pinch identificationPinch identification

Pinch technology series 4

Base case

Reactor

50 C

160 C270 C210 C

210 C

220 C

180 C60 C

130 C

149 C

1620

2640

19801220

178 C

160 C

880

Pinch technology series 5

Data Extraction

Reactor

50 C

160 C270 C210 C

210 C

220 C

180 C60 C

130 C

149 C

1620

2640

19801220

178 C

160 C

880

Pinch technology series 6

…..from data extraction

Reactor

50 C

160 C270 C210 C

210 C

220 C 60 C

130 C

160 C

Pinch technology series 7

Stream Data (Problem Table)

NoT source,

CT target,

CHeat duty,

kWCP Type

1 220 60 3520 22 Hot

2 270 160 1980 18 Hot

3 50 210 3200 20 Cold

4 160 210 2500 50 Cold

CP = Heat duty/ABS(T source – T target)

Pinch technology series 8

Composite Curve

Composite Curve

0

50

100

150

200

250

300

0 1000 2000 3000 4000 5000 6000 7000

Heat duty (kW)

Tem

p in

terv

al (

K) DT min

Pinch technology series 9

Set DTmin = 20 CSet DTmin = 20 C

Pinch technology series 10

Shifted Stream DataHot - ½DTmin; Cold + ½DTmin

NoT source,

CT target,

CHeat duty,

kWCP Type

1 210 50 3520 22 Hot

2 260 150 1980 18 Hot

3 60 220 3200 20 Cold

4 170 220 2500 50 Cold

Pinch technology series 11

Shifted Composite Curve

Shifted Composite Curve

050

100150200250300

0 1000 2000 3000 4000 5000 6000 7000

Heat Duty (kW)

Tem

p in

terv

al (

K)

Pinch technology series 12

Cascade Diagram

0 720 -720 SURPLUS

700 180 520 DEFICIT

2800 1600 1200 DEFICIT

400 800 -400 SURPLUS

1800 1980 -180 SURPLUS

0 220 -220 SURPLUS

22

18

20

50

260

220

210

170

150

60

50

Cold HotCold-HotStream population

Pinch technology series 13

Heat balance in the interval

260

220

210

170

150

60

50

0

720

200

- 1000

- 600

- 420

- 200

Hot utility

-720

520

1200

-400

-180

-220

Cold utility

Heat flow

Pinch technology series 14

The heat flow must NOT be negative

Pinch technology series 15

Normalization

260

220

210

170

150

60

50

0

720

200

- 1000

- 600

- 420

- 200

Hot utility

-720

520

1200

-400

-180

-220

Cold utility

Need additional

heat

Pinch technology series 16

Original Grand Composite Curve

0

50

100

150

200

250

300

-1200 -1000 -800 -600 -400 -200 0 200 400 600 800 1000

Unfeasible region

Feasible region

Pinch technology series 17

…finding pinch

260

220

210

170

150

60

50

1000

1720

1200

0

400

580

800

Hot utility

-720

520

1200

-400

-180

-220

Cold utility

No heat flow at this point

Pinch technology series 18

Grand Composite Curve

0

50

100

150

200

250

300

0 500 1000 1500 2000

Heat duty (kW)

Tem

p in

terv

al (K

)

Qh min

Qc min

Pinch technology series 19

finally….finally….The PINCH POINT = 170 CThe PINCH POINT = 170 C

which means thatwhich means that

Hot stream PINCH = 170+Hot stream PINCH = 170+½DTmin = 180½DTmin = 180

Cold stream PINCH = 170-Cold stream PINCH = 170-½DTmin = 160½DTmin = 160

Pinch technology series 20

Heat source and sink

Heat source this part releases heat

Heat sink this part requires heat

Composite Curve

0

50

100

150

200

250

300

0 1000 2000 3000 4000 5000 6000 7000

Heat duty (kW)

Tem

p in

terv

al (K

)

PINCH

Heat Source Heat Sink

Pinch technology series 21

and, and, how can we design HEN how can we design HEN

based on the pinch?based on the pinch?

Pinch technology series 22

Base case….the existing network

Heat recovery = 1980 + 880 = 2860 kW

Cold utility = 2640 kW

Hot utility = 1220 + 1620 = 2840 kW

22060

270160

21050

160

210H

C

H H

2640

1620

880

1980

1220

Pinch technology series 23

Let’s start from Let’s start from the pinchthe pinch

Pinch technology series 24

22060

270160

21050

160

210

180

180

160

160

2200

PIN

CH

AT

170

0

360

2640

1000

2500

1640

880

20

50

18

22

CPBELOW ABOVE

Pinch technology series 25

Rules….

CP in ≤ CP out Start finding partners for streams OUT (with streams IN,

away from pinch, or utility)

N stream IN ≤ N stream out If Ns IN > Ns OUT, split stream(s) OUT

If CP in > CP out (no match), try to split stream(s) IN Set maximum heat recovery The remaining heat duty is covered by heater or

cooler

Pinch technology series 26

22060

270160

21050

160

210

1

180

2200

1

180

160

160

2200 √√

Step 1: Below the PINCH

Connect S1(22) and S3(20)

CP in < CP out

Pinch technology series 27

22060

270160

21050

160

210

1

180

2200

1

180

160

160

2200 √√

2

2

1620√√1620

Step 2: Above the PINCH

Connect S2(18) and S4(50)

CP in < CP out

Pinch technology series 28

22060

270160

21050

160

210

1

180

2200

1

180

160

160

2200 √√

2

2

1620√√1620

3

3

880

880

√√

2500√√

Step 3: Above the PINCH

Connect S1(22) and S4(50)

CP in < CP out

Pinch technology series 29

22060

270160

21050

160

210

1

180

2200

1

180

160

160

2200 √√

2

2

1620√√1620

3

3

880

880

√√

2500√√

H

1000

1000√√

Step 4: Above the PINCH

Install Heater at S3(20)

Pinch technology series 30

22060

270160

21050

160

210

1

180

2200

1

180

160

160

2200 √√

2

2

1620√√1620

3

3

880

880

√√

2500√√

H

1000

1000√√

C

C

360

360

2640

440

√√

√√

Step 5: Below the PINCH

Install Cooler at S1(22) and S2(18)

All heat requirements have been All heat requirements have been met !!!met !!!

Pinch technology series 31

22060

270160

21050

160

210

H

2200

440

1000

1620

880

C

360

C

…finally…Heat Exchanger Network (HEN)

Maximum Energy Recovery (MER) = 2200 + 880 + 1620 = 4700 kW

Minimum cooling heat duty (Qc min) = 440 + 360 = 800 kW

Minimum heating heat duty (Qh min) = 1000 kW

Pinch technology series 32

Then draw the flowsheet…

Reactor

50 C

160 C

270 C210 C

210 C220 C

60 C

130 C

160 C

880

1620

2200440

360

1000

177.6 C

180 C

180 C

80 C

160 C

Pinch technology series 33

Possible modifications

Pinch technology series 34

Grand Composite Curve

0

50

100

150

200

250

300

0 500 1000 1500 2000

Heat duty (kW)

Tem

p in

terv

al (K

)

Heat generation

Cooling water

MP steam

Pinch technology series 35

Pinch technology series 36

Working Session Working Session

Pinch technology series 37

Feed 2

Feed 1

H= 27 MW

H=32 MW

H= -31.5 MW

H=-30 MW

140 C

250 C

230 C

40 C

40 C

40 C

180 C

20 C

200 C

80 C

Product 2

Product 1

Reactor 1

Reactor 2

How will the HEN be….?