Simulation Study On Separation Of Hydrogen Chloride Gas By Choline Chloride Deep Eutctic Solvents

China is the largest producer and consumer of fluorine chemicals in the world.And,hydrofluorocarbons（HFCs）are important fluorine chemicals.At present,HCFC-22 is mainly produced by the reaction of chloroform with HF,resulting in a large amount of HCl and a small amount of trifluoromethane byproducts.Currently,the HCl absorption process with water is commonly used for tail gas treatment.The resulting dilute hydrochloric acid is of low quality,has limited applications,resulting in severe accumulation.However,high-purity hydrogen chloride gas is an indispensable and high-value bulk chemical that can be used for the production of PVC,chlorinated hydrocarbons,chlorine gas,and so on.In order to achieve high value and resource utilization of by-product hydrogen chloride,and reduce the production of low-grade hydrochloric acid,the absorption-desorption process can be used to produce high-purity hydrogen chloride gas.Such process has high energy consumption and severe equipment corrosion,so it is crucial to find an energy-saving and efficient green absorbent and separation process.Deep eutectic solvents（DESs）have good stability,nonvolatility,designability,low cost and easy availability,and have prospective application in gas capture,such as CO₂,H₂S,VOCs,etc.Currently,research on the absorption of HCl by DESs is still in the experimental stage.To study the performance and energy-saving effect of DESs for HCl and CHF₃ absorption separation,Aspen software was used to simulate and optimize the process.The separation performance and process energy consumption were analyzed and compared with conventional water absorption processes.The solubility of CHF₃ in three DESs,choline chloride-ethylene glycol ChCl-EG（1:2）,choline chloride-malonic acid ChCl-MA（1:1）,and choline chloride-urea ChCl-Urea（1:2）,was measured using a constant volume method.The absorption and separation performance,solvent stability,and regeneration performance of the DESs were analyzed.Finally,ChCl-EG（1:2）is determined as a suitable absorbent.The Aspen software was used to simulate the water absorption process of HCl and CHF₃,and the optimal operating conditions were analyzed and determined.Under the conditions of HCl capture rate of 99.5%and HCl gas purity of 99.9%,the heat consumption for processing 1 ton of HCl is 3.82 GJ,along with electrical energy of 0.24 k W·h,and solvent loss of 4.2 kg.Using ChCl-EG（1:2）as absorbent,a falling film absorber,an absorption tower,and a flash desorption unit is combined to separate and purify HCl gas.The separation process parameters were simulated and optimized using Aspen software.Under the conditions of HCl capture rate of 99.5%and HCl gas purity of 99.9%,the heat consumption for processing 1 ton of HCl is 2.90 GJ,along with electrical energy of 0.51 k W·h,and DES solvent loss of 0.36 kg.Both separation processes above can achieve a HCl capture rate of 99.5%,and HCl gas purity of 99.9%.Compared with the water absorption,the total heat consumption of the ChCl-EG（1:2）-based separation process is reduced by23.8%,the utility cost is reduced to 1212 yuan/t HCl,and the energy consumption cost is reduced by 53.85%.Therefore,the ChCl-EG（1:2）-based separation process for HCl and CHF₃ gas has abvious advantageous and energy-saving effects.