Simulation And Experimental Research Of SO₂ Absorption In The H₂S Splitting Cycle For Hydrogen Production

The H₂S splitting cycle can use sulfur-containing pollutants to produce H₂ and H₂SO₄.When coupling the clean energy,such as the solar and nuclear energy,the H₂S splitting cycle can achieve carbon-free.The Bunsen reaction is the bottleneck for realizing both the H₂S splitting cycle and I-S cycle for hydrogen production because its technical difficulties including the high reaction temperature,the excessive use of reactants,the separation of products,the side reactions,the iodine vapor volatilization and redeposition,and the severe corrosion.Dissolving I₂ in toluene to conduct the Bunsen reaction can lower the reaction temperature and achieve favorable effects such as inhibiting side reactions,avoiding iodine vapor volatilization and easing corrosion issues.The dissolution of SO₂ from gas phase into liquid phase（H₂O or toluene）is the rate-determine step of the gas-liquid-liquid（SO₂-H₂O-toluene）ternary Bunsen reaction.This paper used Aspen Plus software to simulate the absorption characteristics of SO₂in the SO₂-H₂O and SO₂-toluene binary system.Then,with the help of which can increase the mass transfer rate and avoid strong corrosion.The absorption characteristics of SO₂ in the SO₂-H₂O-toluene ternary system were experimentally studied using the Corning AFR-G1microchannel reactor which has high mass transfer rate and excellent corrosion resistance and simulated using Aspen Plus.The research content and main conclusions are shown as follows:（1）ELECNRTL method and Flash2 unit operation module were used to simulate the SO₂-H₂O binary system.Physical property parameters were modified by the analysis and regression of physical property in Aspen Plus to simulate the influence of operation conditions on SO₂absorption characteristics of SO₂-H₂O binary system.The results showed that increasing the pressure,the SO₂ volume fraction in gas and the gas flow rate significantly increased the outlet SO₂ concentration.Increasing the liquid flow rate and the pressure can increase the SO₂absorptivity.Under the condition of 323.15～343.15 K for the temperature,30～50%for the SO₂ volume fraction in gas,500 m L min^-1 for the gas flow rate,and 45～65 m L min^-1 for the liquid phase flow,the simulated results were in good agreement with the experimental results.（2）The physical property analysis function of Aspen Plus was used to verify the reliability of RK-SOAVE physical property method and original parameters of SO₂-toluene system.Flash2 reaction module was selected to study the influence of operating conditions on SO₂absorption characteristics in SO₂-toluene binary system.The simulation results showed that increasing the SO₂ volume fraction and gas flow rate increased the outlet SO₂ concentration.Increasing the liquid flow rate can improve the SO₂ absorptivity.Under the conditions of 10～20%for the SO₂ volume fraction,500 m L min^-1 for the gas flow rate,and 35～65 m L min^-1 for the liquid flow rate,the simulated results were in good agreement with the experimental results.（3）The SO₂ absorption characteristics of SO₂-H₂O-toluene ternary system were experimentally studied using the microchannel reactor.The results showed that the SO₂concentration and absorptivity in both water phase and toluene phase reduced when increasing the temperature;Increasing the water volume fraction increased the SO₂ concentration and absorptivity in water phase and decreased the SO₂ absorptivity in toluene phase.The SO₂concentration in toluene phase increased first and then decreased as the increase in water volume fraction;Increasing the gas flow rate led to the increase in the SO₂ concentration in both water phase and toluene phase but the decrease in SO₂ absorptivity.The SO₂concentration in two phases decreased and the SO₂ absorptivity increased when increasing the liquid flow rate.The UNIQUAC method and the Flash3 unit operation module were selected to simulate the SO₂ absorption characteristics of SO₂-H₂O-toluene ternary system.The results indicated that the selected physical property method was only applicable to investigate the effects of temperature and water volume fraction on the SO₂ absorption characteristics in water phase.（4）Increasing the water volume fraction and the gas flow rate or decreasing the temperature and the liquid flow rate can improve the average absorption rate of SO₂ in SO₂-H₂O-toluene ternary system.The absorption of SO₂ can be promoted at the temperature from293.15 to 303.15 K,the liquid flow rate from 20 to 40 m L min^-1,the water volume fraction from 50%to 75%,and the gas flow rate from 800 to 1000 m L min^-1.