The Study Of High Purity Carbon Dioxide Production Process By Distillation

Carbon dioxide is a major greenhouse gas.It is very important for environmental protection to reduce carbon dioxide emissions in industrial processes through carbon dioxide recycling.Existing carbon dioxide recovery technologies are most focus on carbon dioxide capture rate,and less attention is paid to the purity of carbon dioxide products.In this paper,the process of preparing high-purity carbon dioxide by distillation is carried out.The sources of carbon dioxide feed gas are flue gas,lime kiln gas,fermentation tail gas,hydrogen production tail gas and so on.On the basis of the vapor-liquid equilibrium data between the impurity close to the boiling point of carbon dioxide and carbon dioxide in different feed gases,a suitable thermodynamic calculation model is selected.Finally,the impurities that need special treatment in the separation and purification process and the targeted methods are proposed.Based on the analysis of the characteristics of impurities,the corresponding distillation process is proposed for different types of carbon dioxide recovery processes.The Rectisol tail gas from coal to hydrogen is used as feed gas,in which the main impurities are hydrogen sulfide,carbonyl sulfur,ethylene,ethane and propane.Analyse the vapor-liquid equilibrium of the main impurities in the Rectisol tail gas with carbon dioxide at different pressures.It is found that lower pressure conditions are beneficial to the separation of carbonyl sulfide,ethane and propane.But hydrogen sulfide and carbon dioxide cannot be separated through distillation.So using zinc oxide as an adsorbent to remove hydrogen sulfide.According to the experimental data of the above components,PR-BM equation is selected to simulate and optimize the process of high purity carbon dioxide by distillation.The product recovery rate is greater than 95%,the purity of carbon dioxide is more than 99.999%,the total hydrocarbon content in the product is less than 5PPM and the sulfide content is less than 5×10^-8 are used as constraint variables.Taking the total annual investment cost as the objective function,R507,R1270 and R134a as refrigerants.The improved genetic algorithm was used to optimize the carbon dioxide distillation process globally.The optimized process conditions and equipment parameters are obtained.The minimum TAC with R507,R1270,and R134a as refrigerants are 4710.4×10³$/y,4681.6×10³$/y,4605.9×10³$/y.In order to production unit mass of carbon dioxide,the energy consumption of cooling water is 26.3 t/t,27.4 t/t,27.4 t/t,and the power consumption is all 150 k W/t,which has certain guiding significance for the industrial application of producing high-purity carbon dioxide.Finally,the exergy loss calculations for the different processes of the three refrigerants are carried out to provide a reference for further energy-saving optimization.