Process And Control Strategy Of Heat-Integrated Pressure-Swing Distillation For The Separation Of Benzene/Tert-Butyl Alcohol Azeotrope

Benzene and tert-butyl alcohol are two common organic solvents widely used in chemical and pharmaceutical industries.Because the two solvents will form a minimum-boiling azeotrope,conventional distillation processes are hard to achieve an effective separation at atmospheric condition,and special distillations can be used for the separation.Common special distillations include azeotrpic distillation,reactive distillation,extractive distillation,pervaporation,membrane distillation,and pressure-swing diatillation,etc.It has a certain practical significance for the resource utilization and environmental protection to separate benzene and tert-butyl alcohol azeotrope using reasonable process.Pressure-swing distillation rises more and more attention for the separation of binary azeotrope because no entrainer is introduced and high production purity can be obtained.In this paper,pressure-swing distillation process for the separation of benzene and tert-butyl alcohol was researched,the characteristic of the different feed composition and heat-integrated processes were examined,the robust control strategy was established,and the appropriate process was explored.?1?On the basis of Aspen Plus platformand,the steady-state simulation process was designed,the feasiblity of the pressure-swing distillation with the different feed composition was examined,and the differently heat-integrated pressure-swing distillations with different feed composition to separate benzene and tert-butyl alcohol were revealed?2?On the basis of pressure-swing distillation optimization software?PSDOS?explored by ourselves,the influence of operating parameters,such as number of trays,feed location,and reflux ratio,on the minimum total annual cost?TAC?was examined and the appropriate process was determined.The economy of the different feed composition of different heat-integrated optimal pressure-swing distillation processeswere analyzed,and the operating parameters for the separation of the benzene and tert-butyl alcohol azeotrope were determined.Partial heat-integrated process owned optimal economy in the process with feed composition of 20.0 mol%benzene and 80.0mol%tert-butyl alcohol;fully heat-integrated process owned optimal economy,saving approximately 19%of the TAC in the pressure-swing distillation with feed composition of 50.0 mol%benzene and 50.0 mol%;TAC of partial heat integration is minimum and reduced by 9%compared with no heat-integrated pressure-swing distillation with composition of 80.0 mol%benzene and 20.0 mol%tert-butyl alcohol.?3?The control characteristic for the different composition of different heat-integrated pressure-swing distillation was examined using Aspen Plus Dynamics.For the process with 20.0 mol%benzene,Q_R1/F ratio control structure improved the control effect of no heat-integrated pressure-swing distillation process;the composition/temperature cascade control structure has stronger anti-disturbance ability for the partial heat-integrated process;for fully heat-integrated process,the composition/temperature cascade improved control structure that can be overcome the high voltage of uncontrollable defects in high pressure column was explored.With feed composition of50.0 mol%benzene and 50.0 mol%tert-butyl alcohol,the dynamic control of the composition controller of no heat-integrated process could realize robust control;for the partial heat-integrated control structure,dual composition/temperature cascade control structure made product purity and sensitive stage temperature stable.For the fully heat-integrated process,the composition and temperature controller controlled the purity to 99.9 mol%.With composition of 80.0 mol%benzene,the combination of temperature control structures and composition control structure improved the control effect of no heat-integrated pressure-swing distillation process;in partial heat-integrated process,the method to use the composition control structure has strong anti-disturbance ability;in fully heat-integrated process,composition/temperature cascade improved control structure was explored when added±20%feed composition and feed flow rate disturbances.