| The industrial wastewater containing N,N-dimethylacetamide(DMA)and acetic acid(HAc)produced during the production of DMA by the acetic acid method.HAc-DMA is maximum azeotrope point,and the relative volatility(α)of acetic acid and water is close at 1,high-purity separation cannot be accomplished by traditional distillation.Based on theoretical research,this paper proposes the extractive-pressure swing distillation scheme with tetramethylene sulfone(TMS)as the entrainer,the azeotropic-pressure swing distillation scheme with DMA as the entrainer,and the azeotropic-extractive distillation scheme with ionic liquids(ILs)as the entrainer.The specific research content is as follows:(1)Compare the vapor-liquid equilibrium(VLE)experimental data of the three-group binary system of water-HAc,water-DMA and HAc-DMA with the predicted data of the NRTL-HOC model;and the Redlich and Kister area test and Van Ness point test of thermodynamic consistency were carried out,the results showed that two tests passed.A 4E evaluation system including economic,energy,environmental and thermodynamic efficiency has been established to further analyze the energy saving,economic performance and environmental friendliness of the evaluation process.(2)The effects of TMS,N-methylpyrrolidone(NMP),adiponitrile andε-caprolactam on the relative volatility of HAc-water were compared;at the same time,LD50 data was used as the ecological toxicity of organic solvents,and TMS was selected as the entrainer.The extractive-pressure swing distillation scheme with s TMS as the entrainer was proposed,and the analysis of the exergy loss of the extractive distillation column(EDC)was further completed.Meanwhile,the vapor recompression technology and feed preheating technology were introduced to complete the heat integration enhancement design.Compared with the conventional scheme,the TAC,energy consumption and CO2 emissions of the heat integration enhancement process are reduced by 25.44%,41.45%and 42.95%,and the thermodynamic efficiency is increased by 20.04%.(3)An azeotropic-pressure swing distillation process with DMA as solvent was proposed for the first time.Taking the minimum TAC as the optimization goal,the sequential iterative procedure is used for optimization,and the optimal operating parameters are obtained.In order to further realize the reasonable allocation of energy and reduce TAC,a comprehensive energy utilization configuration of feed preheating and variable pressure heat exchange technology is proposed.Compared with the conventional scheme,the TAC and energy consumption of the heat integration scheme are reduced by 48.23%and 34.84%,respectively.The CO2 emission of the heat integration scheme is 1843.04 kg/h,which is only 51.56%of the conventional scheme.At the same time,the thermodynamic efficiency of the HIESPD scheme is 21.21%,which is much higher than the 16.57%of the conventional scheme.(4)An azeotropic-extractive distillation process with[BMIM][Tf2N]as solvent was proposed o separate the DMA-HAc-water ternary system.A two-stage flash system was used to replace the traditional solvent recovery column.A technology combining side line reboiler and steam recompression technology was further proposed to achieve the effect of energy saving and emission reduction.Compared with the conventional scheme,the TAC,energy consumption and CO2 emission of the heat integration scheme are reduced by 32.41%,41.01%and 52.48%respectively.The thermodynamic efficiency of heat integration scheme is 15.97%,which is much higher than that of AED scheme by 11.61%.(5)Complete single-factor and four-factor analysis of six separation processes.Both single-factor and four-factor comprehensive analysis,the HIAPSD program has obvious advantages.At the same time,it is proved that azeotropic distillation is better for HAc-water separation,and pressure-swing distillation is better for HAc-DMA separation. |
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