Algebraic approaches to resource conservation via process integration

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Texas A&M University

The primary objective of this dissertation is to introduce several algebraic procedures to the targeting of material recycle networks. The problem involves the allocation of process streams and fresh sources to process units (sinks) with the objective of minimizing fresh purchase and waste discharge. In the case of composition-limited sinks, allocation to process sinks is governed by feasibility constraints on flowrates and compositions. A systematic non-iterative algebraic approach is developed to identify rigorous targets for minimum usage of fresh resources, maximum recycle of process resources and minimum discharge of waste. These targets are identified a priori and without commitment to the detailed design of the recycle/reuse network. The approach is valid for both pure and impure fresh resources. The devised procedures also identifies the location of the material recycle pinch point and addresses its significance in managing process sources, fresh usage, and waste discharge. The dissertation also addresses the targeting of material-recycle networks when the constraints on the process units are described through flowrates and properties. This property-integration problem is solvedusing a non-iterative cascade-based algebraic procedure. Finally, for more complex cases with multiple fresh sources and with interception networks, a mathematical-programming approach is developed. Because of the nonlinear non-convex characteristics of the problem, the mathematical model is reformulated to enable the global solution of the problem. Several case studies are solved to illustrate the ease, rigor, and applicability of the developed targeting technique.