Indirect and mixed direct-indirect heat integration of batch processes based on Pinch analysis

This paper introduces a methodology for the heat integration of industrial batch processes. Based on Pinch Analysis principles, this methodology resorts to intermediate heat storage to prevent adverse effects on the operating flexibility, which are often associated with direct heat exchange only. A systematic procedure, backed with a graphical representation, allows the determination of the minimum number of heat storage units assuming vertical heat transfer and their range of feasible operation as a function of the amount of heat recovery. Understanding the cause and the bottleneck effect of the so-called storage pinch, heuristic rules are proposed to screen major options corresponding to minimum cost solutions. For a given number of heat storage units, these rules could be automated to a large extent, making the procedure suitable for targeting purposes. The operating temperature of the heat storage units can be optimized with ease, while other continuous degrees of freedom are more difficult to address using the proposed methodology. Preliminary guidelines are proposed to extend the methodology to mixed direct-indirect heat integration.