New pinch technology based hen analysis methodologies for cost‐effective retrofitting

Abstract

rocess integration methods were, generally speaking, originally developed for grass root situations. Already in the late 198Os, P however, methods for retrofit situations started to emerge. During the 1990s several approaches have been suggested and applied. They are based on pinch analysis (Tjoe and Linnhoff, 1986; Shokoya and Kotjabasakis, 1991;Carlsson et al ., 1993; Stromberg and Berntsson, 1 996), mathematical programming (Ciric and Floudas, 1989; Yee and Crossmann, 1991) or a combination of these two techniques (Zhu and Asante, 1999).In this paper two methods based on pinch technology are presented and exemplified. These are new composite curves (partly published earlier in (Stromberg and Berntsson, 1996), developed for use in a targeting and options scanning stage in retrofitting, and the matrix method (partly published earlier in Carlsson et al., 1993), developed as a tool for cost efficient design in retrofit situations. They both possess the traditional characteristics of pinch technology, i.e. and easy-to-follow way of identifying interesting options, insight and interaction with the user. The aim of this development has been to create pinch technology based methods, with which the general problems with process integration in retrofit situations can be treated, i.e.:restrictions and opportunities caused by the fact that a HEN already exists; targeting in a basic pinch technology sense cannot be done; aspects not related to temperature driving forces and number of units; (e.g. new piping, flow restrictions in existing piping and in space for new equipment); or existing industrial energy systems are normally far from 'pinch correct' designs. The new composite curves can be used for scanning of opportunities for integration of a HP, a CHP plant and retrofit of the existing HEN. In this article, only the HEN retrofit is discussed and exemplified.Below the two methods are explained and an example, in which their application is demonstrated, is presented. New Composite CurvesAn existing concept based on pinch technology for integrating new energy technologies is the grand composite curve (CCC). However, this curve is not well suited for retrofit situations, where mainly two problems with the CCC occur. Firstly, the temperatures are not estimated correctly "Author to whom correspondence may be addressed. Keywords: pinch technology, retrofit, composite curves, heat exchanger network, cost-effective.in existing systems having a heat demand that is large in relation to what could be achieved by enhanced heat recovery. Secondly, the CCC does not give any information about the existing heat exchanger network (HEN), which means that no illustration of the changes needed in the HEN in order to approach the theoretical levels is given.To cope with these problems novel composite curves, developed a t the Heat and Power Department, Chalmers University of Technology, are proposed in this paper. They are based on pinch technology, and permit accurate representation of the existing loads as well as the possible ones th...

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