An Optimal Control Approach to Scheduling and Production in a Process using Decaying Catalysts Abstract   This article presents a novel approach to optimise scheduling and production planning to meet seasonal demand in an industrial process using decaying catalysts, based on its formulation as a multistage mixedinteger optimal control problem (MSMIOCP). Unlike existing methodologies, the MSMIOCP formulation allows to solve this problem as a standard nonlinear optimisation problem without combinatorial optimisation methods, which can be advantageous in providing reliable, robust and efficient solutions. Using this formulation, four case studies of this problem, differing in reaction or deactivation kinetics, are investigated. Two different solution implementations are used, each having their own relative advantages. The first implementation demonstrates a bangbang behaviour for the linear scheduling controls, consistent with a theoretical analysis, but faces integration problems and does not always produce high quality solutions. The second implementation, while not demonstrating the bangbang property, always produces high quality solutions and shows the advantages of the MSMIOCP formulation over existing methodologies.

Optimal Production and Maintenance Scheduling for a Multiproduct Batch Plant Considering Degradation Abstract   Performance decay due to asset degradation is an important constraint in industrial production and therefore needs to be actively considered. This paper focuses on shortterm scheduling for multiproduct batch processes with sequencedependent degradation and is motivated by a case study in which the sequence of multiplegrade batch runs impacts evolution of fouling. A continuoustime scheduling formulation is proposed to incorporate realistic features of the case study processes. The precedence scheduling concept for the sequential process is employed to model sequences of multiproduct orders and maintenance and is implemented using the general disjunctive programming method. The scheduling formulation is applied to the case study and further analyzed through comprehensive computational tests, which illustrates the efficacy of the proposed formulation.