Towards the use of mathematical optimization for work and heat exchange networks

Copyright © 2017, AIDIC Servizi S.r.l. Pinch Analysis is a well-known methodology that has achieved great success in increasing process efficiency since its inception in the 1970s. The traditional approach in Pinch Analysis has mainly been concerned with Heat Integration. However, most chemical processes also consist of pressure-changing units such as compressors, expanders and valves, which will influence the Heat Integration in the process. The problem is extended to that of Work and Heat Integration, a research topic that has gained a lot of interest recently. Pressure manipulation of streams affects the stream temperatures and thus the Heat Integration problem. Furthermore, the inlet temperature to expanders and compressors determines the power produced or consumed. The Work and Heat Integration problem is thus much more complex than Heat Integration alone, and a manual procedure is only possible for very small problems. To handle larger industrial problems and to properly handle the complex trade-offs involved, rigorous optimization models are necessary. This paper studies three existing superstructures for modeling Work and Heat Exchange Networks. It also looks at possible Pinch location algorithms that can be included in the models. Finally, the paper presents the disadvantages in each of the three modeling approaches, indicating the need for a new superstructure.