Research On Optimal Scheduling And Control Of Batch Chemical Processes

With the rapid development of globalized market economy, the competition in chemical industry is being raised, and orders from customers become more and more diverse. On the one hand, batch chemical processes have been widely used in the chemical industry due to its flexibility and product diversification. On the other hand, compared to continuous chemical processes, there are asynchronous, concurrent, conflict and uncertain behavior; this makes their modeling, scheduling and control problems much more difficult. Therefore, their researches have important academic and economic value.In this work, the methods based on Petri nets are proposed to model, schedule and control batch chemical processes. The main contents and contributions are summarized as follows:1. A method is proposed to design the Petri-net model of a batch chemical system according to its topological structure and recipes.2. Via the reachability graph of a Petri-net model, a method is proposed to calculate an optimal strategy that minimizes the total processing time. First, the reachability graph in maximum speed is calculated. Second, an optimal strategy is calculated via this reachability graph.3. A method based on A* algorithm is presented to calculate an optimal strategy minimizing the total processing time. First, the Petri-net model is reduced according to its topological structures. Second, an optimally scheduling model is constructed based on a place-timed Petri net. Finally, an optimal processing strategy is calculated by solving this problem using A* algorithm.4. A method is presented to compute the control matrix for valves given an optimal strategy.A typical batch chemical system is used to illustrate the theoretic results.