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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