Design of multipurpose batch plants with operational pre-conditions

A formulation is presented for the optimal selection of both the equipment units and the network of connections for the multipurpose batch plants while accounting for operational pre-conditions. The model includes very general constraints and objective functions and permits us to optimise simultaneously the structural aspects of the plant and the associated production scheduling, accounting for capital costs of equipment units and pipework, operating costs and revenues. A special novelty of the formulation is that it provides the possibility of generating directly the optimal connectivity between the process units, optimal sizing and costs of the transfer lines and the optimal storage policies for stable products, while accounting for all the possible operational pre-conditions (e.g. need for cleaning, sequential productions and so on). The resulting Mixed Integer Linear Programming, in which binary variables are used to represent the operational and structural choices, is solved using a branch and bound method. Finally, an example is illustrated demonstrating the flexibility and applicability of the approach developed.