Plantwide Scheduling Model for the Typical Polyvinyl chloride Production by Calcium Carbide Method

The polyvinyl chloride (PVC) production by calcium carbide method accounts for the majority of PVC in the market in China, the largest market share in the world. Due to, high energy costs,, increasingly stringent requirements on emission reduction, and intense global competition, the scheduling optimization of PVC production processes, as an effective way to improve profit, is drawing increasing attention. However, most research is only focused on the scheduling of vinyl chloride monomer (VCM) polymerization processes rather than plantwide scheduling optimization. Moreover, the majority of energy consumption lies in the upstream VCM preparation process; including calcium carbide and chlorine production processes. Therefore, plantwide scheduling optimization is of great importance for reducing the energy consumption and improving the overall profit. Hence, a discrete time representation Based plantwide scheduling model is proposed in this paper. Since the operation characteristics in the tithe-scales for VCM preparation and VCM polymerization processes are distinct, different discrete time intervals are adopted to reduce the resulting scheduling model scale. The energy consumption piecewise linear models in terms of the production rates for both calcium carbide and chlorine production processes are addressed to approximate the real-world nonlinear processes. Several cases originated from areal industrial plant are provided to illustrate the effectiveness of the proposed model, and the comparative results with the conventional strategy (i.e.,, only optimizing the polymerization process when scheduling) further prove the necessity of plantwide scheduling optimization.