Redesign of a multipurpose batch pilot plant with cleaning in place (CIP) integration

Abstract

The retrofit design of a multipurpose batch pilot plant is studied so as to accommodate the addition of a new product. A model is utilised which represents in detail structural and operational characteristics as required for production scheduling, while also accounting for cleaning in place (CIP) integration. The State Task Network concepts for defining process recipes and procedures are augmented by the definition of the equipment states (unit dirty, connection clean, etc.). A superstructure of several proposed plant modifications is considered to debottleneck the plant and provide increased flexibility, including piping reconfigurations and the replacement of the existing flow plates with double seat valves manifolds. The retrofit problem is formulated as a Mixed Integer Linear Program (MILP) and solved using a branch and bound technique. The best compromise between extra capital cost (plant reconfiguration) and operating cost/revenues (operating schedule and production amount of the new product) is obtained by maximising the annualised profit. Results show that a small capital expenditure permits the production of the new product within the original time horizon.