Practical Process Integration Retrofit Part 1. Cross-Pinch Method

AIChE Spring Meeting and Global Congress on Process Safety
April 3, 2012 - 12:00am

Practical Process Integration Retrofit

Part 1. Cross-Pinch Method

G.T.Polley

A number of techniques have been developed to aid the process engineer retrofit heat recovery networks. The first of these methods was called the ?Cross-Pinch Method? (Tjoe & Linnhoff [1986]) and whilst it is widely practised by specialist consultants it has not, to the author's knowledge, ever been formally described.

The first step in applying the cross-pinch method is the identification of a heat recovery target. This is achieved using an approximate economic analysis that seeks to relate project savings with capital investment.

Economics of Network Retrofit

Economic Criteria for Energy Saving Retrofit

Relationship Between Installed Area and Energy Consumption

Relating Energy Saving to Project Economics

Full Cost Considerations

Starting Point for Cross-Pinch Method

Example Problem

Cross-Pinch Design Method

Below

Pinch

Above

Pinch

Stream

Cp

Low Temp.

High Temp.

Load

Low

Temp.

High Temp.

Load

E1 (hot)

0.1

174

327

15.3

E1 (cold)

0.1

100

140

4.0

140

253

11.3

E2 (hot)

0.16

160

161

0.16

161

220

  9.44

E2 (cold)

0.2

140

188

  9.6

E3 (hot)

0.2

121

160

7.8

E3 (cold)

0.175

  80

125

7.9

E4 (hot)

0.06

110

161

3.06

161

220

3.54

E4 (cold)

0.06

  60

140

4.8

140

170

1.80

E5 (hot)

0.1

  84

161

7.7

161

174

1.3

E5 (cold)

0.07

  35

140

7.35

140

164

1.68

       

References

Tjoe T.N. & Linnhoff B. ?Using pinch technology for process retrofit?, Chem.Engng., 1986 April 28, pp47-60

Ahmad S. & Linnhoff B. ?Supertargeting: Different process structures for different economics?, ASME J.En.Res.Tech., 1989, 111(3), 131-136

Tjoe T.N.  Ph.D. Thesis 1986, UMIST, UK

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