SHORT-TERM SCHEDULING OF PIPELESS BATCH PLANTS

Pipeless batch plants comprise a number of processing stations of vary ing functionality (e.g., filling, mixing, reacting and emptying statio ns). A number of mobile vessels are used to hold material while it is being processed at stations, or being transferred from one station to another. The vessels may have their own built-in motion mechanism, or may be transported by a shared fleet of automated guided vehicles (AGV s). Examples of processes operated in this fashion include lubricants, adhesives, pharmaceuticals and paints manufacturing. In many applicat ions pipeless plants have advantages over more conventional ones becau se of their increased flexibility with respect to material transfers, and the reduced downtime of processing units caused by product changeo vers. However, the full realization of these potential benefits during operation necessitates solving a complex scheduling problem. The solu tion details the utilization of the processing stations, the transfera ble vessels, and, where appropriate, the AGVs over the time horizon of interest. This paper presents a systematic and rigorous approach to t he optimal detailed shortterm scheduling of pipeless plants. The mathe matical formulation of the problem as a mixed-integer linear programme allows recipes of arbitrary complexity to be accommodated while explo iting fully the flexibility of the available plant equipment.