Synthesis of Heat-Integrated Water Allocation Networks Through Pinch Analysis

Abstract

Thermal energy (or utility consumption) and water can be optimized through the synthesis of heat-integrated water allocation networks (HIWANs). Various numerical optimizations, pinch-based and hybrid tools, have been proposed for HIWAN synthesis. Numerical optimization techniques make it difficult to visualize the problem due to complex formulations involving non-linear equations and/or integer variables. Pinch-based methods provide physical insights but are restricted to graphical techniques. As a result of this, HIWAN synthesis through pinch-based techniques gets tedious for medium-scale to large-scale data. HIWAN synthesis can be solved using a hybrid technique that combines the physical understanding of pinch analysis with a series of linear programming (LP) formulations. The proposed methodology converts the LP into an algebraic solution strategy and thereby making the HIWAN synthesis procedure entirely based on pinch analysis. Unlike the other pinch-based methods that rely on temperature-based heuristics to guide the water re-use streams, this method synthesizes HIWAN as an outcome of a utility minimization algorithm. This algorithm is an extension of the compression work minimization algorithm in hydrogen networks. The nature of these two problems differs due to the requirement of two entities (heating and cooling) in the former instead of one entity (compression work) in the latter. Besides freshwater minimization, this methodology can be applied for the conservation of other resources as well. Illustrative examples of three water allocation networks (one with regeneration) and an ammonia allocation network demonstrate the proposed methodology.