SCHEDULING OF MULTIPURPOSE BATCH CHEMICAL-PLANTS .1. FORMATION OF SINGLE-PRODUCT CAMPAIGNS

A mixed integer nonlinear programming (MINLP) formulation for the single-product campaign formation problem is presented. The formulation possesses considerable degeneracy among the feasible integer solutions and can have a large integrality gap, so that direct solution of the formulation with DICOPT++ requires considerable computation time. The campaign formation decomposition algorithm is presented which alternately solves an equipment group master problem, which provides an upper bound on the processing rate and determines an optimal equipment group profile, and a campaign formation subproblem, which provides a lower bound on the optimal processing rate and determines an equipment assignment and production line schedule for a given equipment group profile. An order of magnitude reduction in computation time is achieved with the campaign formation decomposition algorithm as compared with direct solution of the original MINLP.