An integrated approach to computer-aided operation of batch chemical plants

Abstract

The design and implementation of a computer-based system which integrates planning and plant control of batch chemical plants is presented. Such a system is required so that the full benefits of computer-aided operation, increased production, improved product quality and reduced operating costs may be realized. A functional analysis of the operational requirements of batch plants indicate that a hierarchical and distributed system is favoured. A new operational activity, batch management, is defined which provides the necessary integration by coordinating the activities of the planning and control levels. Batch management allows the control level activities to be driven by events at the planning level such as changes in product demands. It also provides a feedback path from the control level back up to the planning level so that the inherent variability of batch processes can be accounted for and overcome. This is achieved by dynamic, on-line rescheduling. A very general implementation of this design is described. The implementation is centred around a real-time database and permits the operation of a wide range of processes including multiproduct, multipurpose plants with both serial and parallel lines, intermediate storage, shared utilities, etc. To demonstrate its effectiveness, two applications are presented, one in conjunction with an on-line, real-time control system, and the other with an off-line discrete event simulator. The significant benefits achieved in terms of improved operation are discussed.