Batch Scheduling and Planning

Saadet Ulas Acikgoz UOP, A Honeywell Company, 25 E. Algonquin Rd., Des Plaines, IL 60017 

Simple batch process flow diagram for Products A, B, and C 

The example shown above is a multipurpose, multiproduct batch plant consisting of multiple stages. These types of plants are called job-shop plants in literature. In job-shop scheduling problems, different products may follow different paths for production. Another example of a multiple product batch plant is a plant where all 

F = RIter H = Heater R1 = Reactor 1 R2 = Reactor 2 S = Separator D = Dryer 

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The last but one chapter in this book is devoted to batch scheduling and planning. These problems are part of optimization problems and hence an industrial case study illustrate how to formulate such problems and solve it. Batch process simulation is the last chapter, mostly devoted to batch process simulation software and illustrative case studies. 

Table 16.3 categorizes the typical problem statement for the manufacturing scheduling and planning problem. In a batch campaign or run, comprising smaller runs... 

G.V. Reklaitis. Overview of scheduling and planning of batch process operations. Proceedings of the NATO, Antalya, Turkey (1992) pp. 660-675. 

Romero J., Badell M., Bagajewicz M. and Puigjaner L. 2003b. Integrating budgeting models into scheduling and planning models for the chemical batch industry, Ind. Eng. Chem. Res., 42(24), 6125-6134. 

Linear programming (LP) The objective function and constraints are linear. The decision variables involved are scalar and continuous. Examples of LP problems involved in batch processing are scheduling and planning, and blending problems. 

Criteria and constraints in production planning, scheduling, and design of batch plants... 

A lot of contradictions in planning processes have their root in the separation of material requirements planning and resource scheduling. This leads to the situation that detailed planning of multipurpose batch plants is still the domain of experienced production schedulers and shift managers who have gained superior knowledge over the years that makes them indispensable. 

The nonlinear nature of these mixed-integer optimization problems may arise from (i) nonlinear relations in the integer domain exclusively (e.g., products of binary variables in the quadratic assignment model), (ii) nonlinear relations in the continuous domain only (e.g., complex nonlinear input-output model in a distillation column or reactor unit), (iii) nonlinear relations in the joint integer-continuous domain (e.g., products of continuous and binary variables in the schedul-ing/planning of batch processes, and retrofit of heat recovery systems). In this chapter, we will focus on nonlinearities due to relations (ii) and (iii). An excellent book that studies mixed-integer linear optimization, and nonlinear integer relationships in combinatorial optimization is the one by Nemhauser and Wolsey (1988). 

A number of issues need to be resolved when dealing with batch reactors in industrial applications, ranging from design and planning of the plant to scheduling, optimization, and performance achievement of batch operations. Performance is usually specified in terms of productivity of the plant, safety of operations, and quality of final products. In order to meet such requirements, several problems need to be addressed ... 

Pure simulation approaches are proposed by Pitty et al. (2008) and Adhitya and Srini-vasan (2010). Pitty et al. (2008) propose a discrete-event simulation model for a refinery supply chain. Operational decisions such as unloading schedules and production planning are made based on simple priority rules. Various configurations of the modelled SC are studied and compared to reveal optimization potentials. This approach explicitly considers some details of ship and pipeline transports. Adhitya and Srinivasan (2010) describe a discrete-event simulation model for an SC producing and distributing lubricant additives. Here, batch production is modelled. Again, operational production decisions are made by priority rules and a scenario analysis is conducted to evaluate the effects of other priority... 

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