Energy Saving Optimizing And Control Of Multi-effect Evaporation Process

Multi-effect evaporation technology has a broad application in the solution concentration process,how to achieve automatic control of multi-effect evaporation process has become the hot issue of the expert,The high concentration of ammonium sulfate solution was obtained by a dilute solution of ammonium sulfate that contains a certain of ammonia thought moisture vaporization,In the production process,the outlet concentration in vapor phase of final effect of ammonia as low as possible,however But at this stage the process has many problem that was irrational use of hot steam and it has not been able to achieve automatic control and regulation of the outlet concentration of ammonia in the actual operation.So this paper with three-effect evaporation system of ammonium sulfate as the research object,using chemical simulation method to simulate the process of evaporation of systematic research,optimization and control system operating conditions to achieve an effective guiding role for the research of self-control multi-effect evaporation of ammonium sulfate production process.In this paper,three effect cocurrent flow,three effect countercurrent flow and three effect mixed flow of the process of ammonium sulfate multi-effect evaporation was established by the use of Aspen Plus software HeatX,Heater,Flash2,Pump,Mixter and FSplit,and the accuracy of the model was verified according to the literature.The effects of feed flow rate,feed temperature,ammonium sulfate concentration of feed and the amount of heating steam of three kinds process on the concentrated were investigated respectively,and the consumption of fresh steam of three kinds of evaporated forms were investigated too when the temperature difference of heat unit outlet and cold unit of ex-changer was 2 ?,4 and 6 ? ?.The results show that when the heating steam consumption keep constant,liquid outlet concentration of the solution decreased with the increase of feed flow rate,liquid outlet concentration of the solution increased with the increase of feed temperature and feed composition content;when liquid outlet concentration of the solution keep constant,the heating steam consumption increased with the increase of feed flow rate,the heating steam consumption decreased with the increase of feed temperature and feed composition content,with decrease of the temperature difference of heat unit outlet and cold unit of ex-changer,the consumption of heating steam of three effect cocurrent flow decrease the most,followed by three effect mixed flow,three effect countercurrent flow the least.Uing Aspen Dynamics software for dynamic simulation of cocurrent flow triple,three kinds of control schemes were put forward,they are triple effect evaporation concentrated solution with basic control structures,feed flow cascade control liquid export solution concentration and heating steam flow cascade control liquid export solution concentration.their control effects were compared when the feed flow,temperature and composition changed.Results show that evaporation system with the basic control structures has a larger overshoot,and it cannot keep the liquid phase concentration of exports relatively stable,feed flow cascade control and heating steam flow cascade control both can satisfy the require that liquid outlet concentration is relatively constant,in comparison,the latter has a smaller maximum deviation and a shorter recovery time.