Control Of Reactive Distillation Columns Separating Reacting Mixtures With Somewhat Unfavorable Relative Volatilities

Reactive Distillation Columns and rectification technologies have a huge advantage over traditional chemical control processes in reducing investment,operating investment,and production costs.Reactive Distillation Columns require more in-depth research.However,due to defects in the structure of the conventional reactive distillation columns(CRDC),it is more affected by the relative volatilities of the reacting mixtures.When the reacting mixtures is used,insisting on using CRDC will cause the heaviest reactant B to accumulate at the bottom of the Columns.The reactant B cannot return to the reaction section to participate in the reaction again.Waste,increase in total investment in equipment,etc.,which is also the main defect of CRDC.In order to solve this defect,the use of external recycle reactive distillation columns(Reactive Distillation Columns with an External Recycle from Bottom to a Certain Stage of Reactive Section,RDC-ERBR),that is,at the bottom of the reactive distillation columns and in the reaction section An external recycle structure is added between the block plates,and the heaviest reactant B accumulated at the bottom of the Columns can be returned to the reaction section With the help of reflux to participate in the reaction,promote the progress of the reaction,and increase the conversion rate of the reactants.The external recycle structure improves the steady-state performance of the reactive distillation columns.At the same time,its effect on the dynamic performance of the reactive distillation columns is also worth studying.This subject focuses on studying the dynamic control of the external recycle Reactive Distillation columns under the relatively somewhat unfavorable relative volatilities ranking,and compares it with the dynamic performance of CRDC,and at the same time understands the influence of the control of the external recycle flow on the system dynamic performance.RDC-ERBR has 7 manipulated variables,one more than CRDC,which is the external recycle ER.Adopt return flow to control the top discharge concentration,discharge flow to control the top liquid level,B feed flow to control the B component concentration on the sensitive board,discharge flow to control the bottom liquid level,and reboiler heat load to control the bottom discharge concentration The control scheme has a total of four control structures:CSO-CRDC,CS1-RDC-ERBR(external circulating flow is a steady-state fixed value),CS2-RDC-ERBR(using external recycle flow to control the concentration of component B on the sensitive stage),CS3-RDC-ERBR(additional proportional control between external recycle flow rate and B component feed flow rate).Experiments show that the external recycle structure improves the dynamic performance and controllability of the reactive distillation columns.Two simulation experiments,ideal quaternary exothermic reversible reaction and esterification reaction of acetic acid and methanol,prove that the external recycle structure improves the system dynamic performance and anti-interference ability.When the added disturbances are the same(feed flow disturbances,feed component disturbances,discharge concentration disturbances),RDC-ERBR has better dynamic performance,while controlling the external recycle flow can also improve the dynamic performance of the system.The research of this subject proves that the dynamic characteristics and control effect of the RDC-ERBR system have been greatly improved in dealing with the reactions of relatively somewhat unfavorable relative volatilities ranking...