Control Of Dividing Wall Columns And Dynamic Behavior Analysis Of Their Start-up And Turndown

The dividing-wall column(DWC)is a typical example of energy saving.DWC has the advantages of low energy consumption and high thermodynamic efficiency.In recent years,the research and application of DWC has become a hot topic in the chemical industry and petroleum industry.However,due to the complexity of DWC,the operation,control,start-up,shutdown of DWC become more complex,which is restricting the large-scale application of DWC.In this paper,through the hydrocarbon system and alcohol system,the control strategy,start-up,shutdown process of the DWC was studied.the detailed contents include:Aspen Plus Dynamics and Aspen HYSYS software were used to control the hydrocarbon system.the key components of the column top,side and bottom were observed by adjusting the flow rate and composition of the feed.By comparing the result,we can find two-point temperature control structure has a better control effect in resisting feed flow.However,three-point temperature control structure has a better control effect in resisting composition of the feed.At the same time,we can also compare the impact of different simulation software on the same system,finding that Aspen HYSYS is better for two-point temperature control and three-point temperature control,yet Aspen Plus Dynamics is better for four-point temperature control.Aspen Plus Dynamics were used to control the alcohol system.According to the steps of the hydrocarbon system,we can find that four-point temperature control structure has a better control effect in response to feed flow,composition.Comparing the impact of different systems on the DWC,we can find that different systems have different best control strategy.Aspen Plus Dynamics was used to study the start-up and shutdown of hydrocarbon system.By comparing the steam consumption,adjustment time,residual difference of every control plan in the start-up and shutdown process,we can find that the four-point temperature control structure has a smallest steam consumption,a shortest adjustment time and a strongest ability to overcome the disturbance.However,this paper is not covered the temperature difference control,double temperature difference control.In the start-up process,we also did not discuss the impact of different start-up style,which will be studied in the future.