Energy-saving Research On Distillation Separation Process Of N-Butanol-Isopropanol-Ethanol-Water System

As a renewable biomass energy source,bio-butanol has received widespread attention due to its good fuel properties.Bio-butanol can be separated from fermentation product butanol-isopropanol-ethanol-water mixture through rectification.However,due to the low concentration of bio-alcohol in the fermentation product and the existence of homogeneous azeotropes and heterogeneous azeotropes in the system,it is difficult to obtain fuel-grade high-purity butanol products by simple distillation.In order to obtain a biobutanol product with a mole fraction of 0.9999 as an alternative biofuel and a mixture of isopropanol-ethanol with a mole fraction of 0.9993(the mole fraction of ethanol is 0.1292 and the mole fraction of isopropanol is 0.8701)as a gasoline additive.This paper designs a conventional distillation process flow composed of "conventional distillation-azeotropic distillation-extractive distillation" and a reactive distillation process flow composed of "conventional distillation-reactive distillation".With the total annual cost as the objective function,the conventional distillation process flow and the reactive distillation process flow are optimized,and the best operating parameters of the process flow are obtained.Based on the optimized conventional distillation process,the conventional distillation process heat integration double-effect distillation,conventional distillation process heat integration double column variable pressure distillation and conventional distillation process heat integration heat pump assisted distillation were designed respectively.Three intensified processes are designed.Based on the optimized reactive distillation process,the thermal integration process of reactive distillation process is designed.Finally,the six proposed processes are compared in terms of total annual cost(TAC),annual energy consumption(TEC)and gas emissions.The results show that for the conventional distillation process consisting of "conventional distillation-azeotropic distillationextractive distillation",compared with the conventional distillation process,the conventional distillation process heat integration double-effect distillation saves 11.87 % of the TAC,reduced TEC by 22.24% and reduced gas emissions by 20.16 %.Compared with the conventional rectification process,the conventional rectification process heat integration-two-tower pressure swing rectification saves 17.59 % of TAC,23.05 % of TEC,and32.48 % of gas emissions.Compared with the conventional rectification process,the conventional rectification process heat integration-heat pump assisted rectification saves 26.96 % of TAC,46.72 % of TEC,and 29.19 %of gas emissions.For the reactive distillation process composed of "conventional distillation-reactive distillation",compared with the conventional distillation process,the reactive distillation process saves29.58 % of TAC,35.78 % of TEC,and 36.79 % of gas emissions.the amount.Compared with the reactive distillation process,the thermal integration of the reactive distillation process saves 53.15 % of TAC,76.06 %of TEC,and 76.06 % of gas emissions.The research results show that the reactive distillation process performs better in the three aspects of TAC,TEC and gas emissions.