Optimal Design of Heat-Integrated Multipurpose Batch Facilities with Economic Savings in Utilities: A Mixed Integer Mathematical Formulation

Abstract

The increasing importance of utilities rationalization is an aspect that must be addressed from the early steps of the industrial design procedure. This paper addresses this problem and presents a mathematical formulation for the detailed design of multi-purpose batch process facilities where heat-integration and economic savings in utilities are considered. This generalization appears as an extension of the work of Barbosa-Povoa et al. [3] where some important design aspects were not considered. In particular, no consideration was given to the economic savings in utility requirements, while considering both the cost of the auxiliary structures (i.e. heat-exchanger through their transfer area) and the design of the utility circuits and associated piping costs. These aspects can appear quite relevant at the design level if the connectivity cost and consumption utilities account for a significant share of capital investment within the plant budget. Also, and at the operational level, heat-integration considerations often result in important plant savings. The problem is formulated as a Mixed Integer Linear Problem (MILP) where binary variables are introduced to characterise operational and topological choices, and continuous ones define the equipment capacities, as well as the amounts of material within the overall process. The applicability of the proposed model is shown via the solution of some illustrative examples.