Optimization Of Production Scheduling And Heat Integration For Batch Plants

Batch processing is commonly used to manufacture high value added products when products are required in small quantities.Facing the challenge of sustainable development and global competition,the way to maximize resource utilization and reduce emissions has become the key role in keeping enterprises alive and flourishing.This paper aims to develop a system-oriented approach for the optimization of production scheduling and heat integration in order to improve the utilization of resources and minimize the operation cost and capital cost.The main contents addressed in this paper can be stated as follows:(1)Sequential methodology for production scheduling and heat integration of batch plants: First,scheduling models are established based on a continuous time expression and state task network representation with the objective of maximum production.Then,heat integration can be achieved through heuristic method applying time slice model to reduce the consumption of utilities.The results show that sequential optimization strategy may get sub-optimal solutions,but it is still an effective method especially dealing with large-scale problems.(2)Simultaneous optimization for production scheduling and heat integration of batch plants: To explore more opportunities for heat integration,simultaneous optimization strategy is investigated in this paper.Heat integration model is built on the scheduling framework.The proposed formulation can get global optimal results with the objective of profit maximization,with profit defined as the difference between product revenue and cost of utilities as well as heat exchange equipments.The innovations of this paper are as following: Firstly,the concept of associated task is introduced to describe the heat transfer requirements of production tasks and an improved State-Tasks-Network representation is adopted to capture all streams-streams,units-streams and units-units heat integration opportunities.Besides,the detailed design of heat transfer schemes and time sharing mechanism of heat exchangers are also involved in the proposed framework by considering heat transfer tasks-units allocation constraints.(3)Common use of heat exchangers by partitioning and reassembling heat transfer areas in batch plants: The cost of heat exchangers is related to its area,so it is an effective way to reduce capital cost through common use of heat exchangers by partitioning and reassembling heat transfer areas on different periods.In this paper,a difference order strategy is developed to introduce timesharing mechanisms into the preliminary heat exchanger network designs on each period which decrease the model solving difficulty.At last,an illustrative example is presented to demonstrate the validity and advantages of the proposed approach.