Operation Optimization Of Vacuum Distillation System Based On Exergy Analysis

In a vacuum distillation,operating conditions obviously influence the manufacture cost of the product which can be reduced by operation optimization and manufacture scheduling.Due to the complex objective function,operating feasible region and operating mode,it is difficult to optimize the vacuum distillation system.In this thesis,modeling,exergy analysis,parameters estimation,operation optimization and scheduling are studied as follows:(1)The model of the vacuum distillation is built with the process simulation software Aspen Plus.The field data of the system are reconciled to obtain 11 steady-state operating conditions.And important parameters including Murphree efficiency and draw out rate of the vacuum system can be obtained to prove the reliability of the model.(2)Establish the operation optimization problem with the objective based on exergy analysis.There are two decision variables: top pressure of column and feed rate.The objective function is to minimize the operating cost.The equality constraints include material balance and energy balance,and inequality constraints include the purity of product and equipment performance.The feasible region of operating parameters can be obtained.The effect of decision variables on the exergy loss and manufacture cost was investigated,and the optimal solution was searched.The result shows that the optimal solution decreases the manufacture cost by 12.2%.(3)Compare the various scheduling plans of the system which contains three parallel distillation columns with the same structure.Considered that the relationship between operation cost and operation parameters is not linear,the optimization work is divided into two parts: operation optimization and manufacture scheduling.Take the influence of operating pressure,feed rate,allocation of period and task into account,the optimal scheduling plans for different tasks can be obtained.