Practical Process Integration Retrofit Part 1. Cross-Pinch Method

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

Table 3. Pinch Table

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