Mapping the Current Value Chain Configuration

In the pilot application of the model, s2 was purchased externally at all sites except at the major production site of the value chain. A closure or significant downsizing of this major production site was excluded from the solution space up front. Therefore, it was decided not to include the production of s2 in the model even though the value chain analyzed is the only one using s2 as an intermediate. 

Within each plant class to be considered the production process consists of a number of chemical and/or physical tasks. While the type and/or quantity of input factors such as raw materials and utilities might differ significantly between products, the characteristics of the production process within a single plant class are usually similar (except for multi-purpose plants). Therefore, the activities taking place within a single plant class can normally be combined for strategic planning purposes. The overall capacity of a plant is then determined based on the bottleneck (usually the ma- 

In some cases, product mix-dependent effects might have to be considered. For example, only a subset of the products requires processing step t5. Reflecting this fact, the installed capacity of the equipment used for t5 was found to be less than the overall plant capacity at most plants. In situations like these, an additional capacity restriction is required to ensure that only feasible product-plant allocations are proposed by the model. If task t5 requires substantial resources such as dedicated equipments or personnel, the model has to be further extended to explicitly model this resource and the costs associated with its utilization based on the production volumes allocated to the respective plant. 

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