As a result of product diversification and increasing volatility of markets, the capability to adapt the production output of chemical plants becomes crucial for economic success. The plant design for pharmaceutical products is determined by a shorter time-to-market and uncertain market sales. Therefore a product launch requires a production of small amounts during the market entry. Thus, pharmaceutical chemicals are conventionally produced batch-wise in a multi-product plant that is flexible regarding production rates. However, a batch-wise processing is inefficient in terms of resource consumption, batch failures and cleaning effort. Due to an uncertain market demand, for the production of increased product quantities a more efficient and flexible plant concept is required .
In this context, a continuously operated modular multi-product plant offers the solution of an efficient and flexible production. Continuously operated processes enable an increase of efficiency in production. The modular design enables a short time-to-market and a flexible adaptation of the production capacity. Thus, an efficient early market entry is possible due to the design of modular production line with a fixed design capacity for small product amounts. When market demand increases a stepwise numbering-up of the modular production line allows a fast and flexible adaptation of production capacities by reuse of engineering. The smaller the scale of the modular production line is, the more expansion steps are necessary to supply the increasing market demand. As a consequence, this capacity flexibility results in additional costs incurred by the loss of economy of scale. Furthermore, a flexible reallocation of the production of different products within the production capacity is possible. This planning flexibility also results in additional costs for setup changes and storage of the products. The increased flexibility provided by this modular plant concept has to be balanced with the consequent costs.
In this work the modular plant concept regarding capacity flexibility and planning flexibility is evaluated. Regarding an uncertain market development, the sequential expansion by numbering-up of a modular production line is investigated. Therefore, a long-term production planning for lot-sizing and scheduling of a multi-product production is applied. Thus, necessary expansion steps are identified when the market demand exceeds the production capacity. An economic evaluation is conducted to consider additional cost by the sequential investment and the production planning. A decision tree analysis is applied to balance the added value of flexibility with the additional costs. Therefore, the obtained flexibility of different scales of a modular production line is evaluated.
 T. Bieringer et al., Chemical Engineering & Technology, 36 (6), 2013, 900–910
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