Study Of Separation Schemes For Tert-butanol/water Azeotrope

Anhydrous tert-butanol(TBA)is an important chemical raw material.However,it can form a minimum azeotrope with water in industrial production,making it difficult to produce highly purified TBA by simple distillation.In this article,the separation schemes for TBA dehydration of conventional two-column extractive distillation(CEDC),extractive dividing-wall column(EDWC)and reactive distillation column(RDC)were proposed.Firstly,in the optimization of CEDC and EDWC,the process was simulated via Aspen Plus software.With the minimum annual total cost(TAC)as the target function,the optimal operating conditions were obtained by the sequential iterative optimization method.Moreover,in the design of RDC,utilizing the non-catalytic,exothermic and irreversible characteristics of the ethylene oxide(EO)hydration,multiple feeds of EO was feed into the RDC,where EO can react with water and circumvent the azeotropic equilibrium of TBA/water to produce anhydrous TBA.In view of the complexity of the RDC,the detailed sensitivity analysis of operating parameters,including operating pressure,feed ratio,theoretical stages,feed location and liquid holdup,was performed to optimize the process parameters of RDC.The feasibility and potential of the RDC scheme for the removal of water from TBA/water mixture were discussed.Finally,based on the steady-state results of RDC,three control schemes were established in Aspen Dynamics.The disturbance of the feed flow(±10%)and the composition variation(±5%)were applied to the control structures,and then their anti-disturbance ability against two different types of load disturbances was tested.The computational results showed that the EDWC,compared with the CEDC,can reduce 2.23%of energy consumption,while the operating cost of EDWC increased by11.10%due to the use of high-pressure steam as heating medium.The overall TAC increased by 6.51%.Therefore,the EDWC was not economically superior to CEDC.Conversely,47.69%of energy consumption and 35.36%of TAC can be saved in the RDC process,exhibiting excellent application potential for TBA dehydration.It was found in the dynamic study of RDC that with the introduction of Q_R/F feedforward control and the R/F proportional control structure,the temperature-composition cascade control scheme could effectively resist the disturbances.The vibration amplitude of temperature curves and purity curves was reduced,and the purity of the products was also satisfactorily maintained.