Dynamic And Control Of Vapor Recompressed Dividing-wall Columns With Light-component Dominated Mixtures

Vapor recompressed dividing-wall distillation columns(DWDC-VRHPs),combining with vapor recompressed heat pump(VRHP)and dividing-wall distillation column(DWDC),has advantages in energy saving,but the strong coupling of DWDC-VRHPs makes it difficult to control them effectively and restricts the development of its control research and industrial application,therefore,it is necessary to study the dynamic properties and control of DWDC-VRHPs to solve the above problems.In order to study the dynamic properties and control of DWDC-VRHPs under the feed conditions of ternary wide boiling point system and absolute dominance of light components,in this paper,the dynamic properties and control of DWDC-VRHPs with one-stage VRHP structure(DWDC-1VRHP),DWDC-VRHPs with two-stage VRHP structure(DWDC-2VRHP)and DWDC without VRHP structure were studied for benzene / toluene / xylene systems with a proportion of 90%/5%/5% respectively,and the role of VRHP structure was explored.First of all,this paper studied dynamic properties of DWDC-VRHPs and DWDC.The results show that the open-loop response of DWDC-VRHPs is better than that of DWDC,and the open-loop response of DWDC-1VRHP is better than that of DWDC-2VRHP about DWDC-VRHPs.And then,in the research of closed-loop control,the single loop temperature distributed control strategy is proposed.The results show that the closed-loop control effect of DWDC-1VRHP is the best,followed by DWDC-2VRHP,and finally DWDC.Finally,aiming at the shortcomings of single loop temperature distributed control,an improved temperature and temperature cascade control scheme is proposed,and the effectiveness is verified by testing.The research of this paper confirms that the increase of the number of VRHP structures will enhance the coupling between DWDC-VRHPs variables,and even reverse the effect of manipulated variables on the controlled variables,affecting the dynamic controllability and closed-loop control of the system.Therefore,the number of VRHP structures needs to be limited.The VRHP structure of DWDC-VRHPs can respond to the change of feed in time,so that the existence of VRHP structure makes the dynamic characteristics and closed-loop control of DWDC-VRHPs better than that of DWDC without VRHP structure.Selecting the sensitive plate temperature with little interaction with the VRHP structures as the controlled variable can improve the control performance.