Process Heat Recovery Modification Assessment

It is not trivial to determine the best modification options that could feature minimal capital cost and the smallest effect on existing infrastructure and thus achieve maximum energy savings. The search for such options could be very time consuming for a complex heat recovery system. The incentives to find practical yet optimal modifications have been discussed by many other researchers and practitioners. The network pinch method developed by Zhu and Asante (1999) has been proven successful for practical applications, which will be discussed in detail in this chapter. 

Energy and Process Optimization for the Process Industries, First Edition. Frank (Xin X.) Zhu. 

In the past, the retrofit methods based on the proeess pineh concept was widely used (Tjoe and Linnhoff, 1986 Policy etal., 1990 Shokoya and Kotjabasakis, 1991). However, the process pinch is developed for grassroots design and is fundamentally irrelevant to the retrofit scenario. The method (Zhu and Asante, 1999) to be discussed here is a two-stage approach identify the network pinch, the true bottleneck of an existing heat recovery system, and determine modihcations with minimum capital costs to overcome the network pinch— that is the reason why this method is called the network pinch method. 

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Once specific process units have been identified for improved heat integration, pinch technology can be applied to efficiently screen potential modification options, which is explained in Chapter 9. Practical assessment (Chapter 10) is required, which considers not only the value and cost of improved heat recovery but also the impact in terms of operating flexibility, especially with respect to start-up, shutdown, maintenance, control, and safety. 

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