Modeling Study On BFVRC Integrated With Side Heat Pump For Distillation Of Close Boiling Mixture

The separation of close boiling point mixture is common in the process industry.Suffering from its low relative volatility leading to high energy consumption and investment,heat pump distillation is an effective method which upgrade the top of the tower gas by compression so that it can be transferred as the heat source of reboiler instead ofliquefied by cold utility.One type of heat pump distillation called BFVRC is rather effective so it should to be studied.Aided by thermodynamic analysis,we discovered that although BFVRC has the advantage in energy conservation than CDiC,temperature magnitude that need to be conquered between top tower gas and reboileris high causing a low COP.Therefore,three new modifications of BFVRC including SHP-BFVRC(Side heat pump-BFVRC),IC-BFVRC(Intermediate condenser-BFVRC),IR-BFVRC(Intermediate reboiler-BFVRC)are proposed to transform redundant heat of rectifying section to stripping section which lower the temperature magnitude of heat pump as well as improve reversibility.An elaborate SHP-BFVRC model including tower,compressor,throttle valve,exchanger was built aim at separating closing pointing mixture.The model is based on SRK equation of state whose.Thermodynamic parameters are calculated by bubble and dew point method.Triangle Matrix is used to deal with material balance.Enthalpy balance equations are employed to calculated tray liquid and vapor rate and duty of intermediate exchanger.Sequential modular approach are used to solve the whole model.An application of the model separating propene and propane is used to compare with Aspen Plus showing litter differences verifying its validity.Finally,GA aiming at TAC minimum is employed to optimizenew process with five variables(configuration of intermediate heat pump,pressure of the top of the tower,feed tray position,configuration of intermediate exchanger,heat duty of intermediate exchanger).An example of 20×104 tons per year gas separation plant shows that compared with BFVRC,SHP-BFVRC can lower TAC of 8.6% and process exergy of 9.1%.