Systematic Methods for the Design and Scheduling of Flexible Multiproduct Continuous Plants

化工行业的一个趋势是设计更小、灵活的多产品工厂，这些工厂位于消费市场附近。建造这种工厂的动机不仅在于降低运输和库存成本，还在于提高提供稳定产品供应的能力，并对每个市场的需求变化做出更快的反应。因此，灵活的多产品工厂提供了提高化工企业竞争力的可能性。多产品工厂可以以批量或连续模式运行，也可以两者兼而有之。前者的典型例子包括制造药品、食品和特种化学品的工厂；后者的例子包括制造一些聚合物产品的工厂、造纸厂和炼油厂。多产品工厂与大型专用连续工厂的主要不同之处在于，调度和生产计划在这些工厂的运营中起着主要作用。另一个问题是，在多产品工厂中，产品需求的不确定性和波动往往要大得多。这项研究致力于开发系统的方法来设计和调度在连续模式下运行的各种类型的灵活的多产品化工过程。这项工作涉及开发模型和解决技术，用于同时设计和调度由一系列阶段组成并由中间库存储罐相互连接的工厂。基本目标是通过选择设计变量、操作条件、操作顺序、生产周期长度和库存水平来确定最佳权衡。将研究严格和简化的模型，以及在面对不确定需求时评估和优化设计灵活性的方法。

A trend in the chemical industry is the design of smaller flexible multiproduct plants that are located close to the markets of consumption. The motivation in building such plants lies not only in the reduction of transportation and inventory costs, but also for increasing the capability to provide a steady supply of products, and for responding more quickly to demand changes in each market. Thus, flexible multiproduct plants offer the possibility of improving the competitiveness of chemical companies. Multiproduct plants can operate in batch or continuous mode, or with a combination of the two. Typical examples of the former include plants for manufacturing pharmaceuticals, food and specialty chemicals; examples of the latter include plants for manufacturing a number of polymer products, paper mills and petroleum refineries. The main difference that arises in multiproduct plants compared to large scale dedicated continuous plants is that scheduling and production planning play a major role in the operation of these plants. Another issue is that uncertainties and fluctuations in the product demands tend to be much greater in multiproduct plants. This research deals with the development of systematic methods for the design and scheduling of various types of flexible multiproduct chemical processes that operate in the continuous mode. The work involves the development of models and solution techniques for the simultaneous design and scheduling of plants that consist of a sequence of stages and that are interconnected by intermediate inventory tanks. The basic objective is to determine optimal trade-offs arising from the selection of design variables, operating conditions, sequencing of operations, length of production cycles and inventory levels. Both rigorous and simplified models will be investigated, as well as methods for assessing and optimizing the flexibility of the designs in the face of uncertain demands.