Screening Of Amine-based Absorbents And Matching Of Absorbents And Process Flowsheet In Sulfur Dioxide Capture

Flue gas SO₂ emission is the root cause of air pollution and overcapacity of desulfurized gypsum.As an important sulfur carrier,if SO₂ in flue gas can be utilized as a resource,it can provide a way to solve the problem of sulfur shortage in my country.Amine-based absorbent SO₂ capture technology can efficiently capture low-concentration SO₂ in flue gas and realize efficient recycling of sulfur resources.However,the high energy consumption of absorbent regeneration is one of the main factors restricting its industrial application.In this study,N-methyldiethanolamine（MDEA）was used as absorbent to build process moldel of SO₂capture from flue gas.It was found that the latent heat consumption of solvent vaporization accounted for 77.12%of the total energy consumption,which was the main reason for the high energy consumption of SO₂capture system.The matching between MDEA solution and process flowsheet in SO₂capture was carried out based on process integration method,and energy recovery and utilization were used to reduce the energy consumption of regeneration.The results show that the overhead steam direct compression heat pump process has the most energy saving potential,reducing the regeneration energy consumption from 11.57GJ·t^-1SO₂ to 4.28 GJ·t^-1SO₂.In the energy consumption distribution of the SO₂ capture process of MDEA after process optimization,the desorption reaction heat consumption is the largest,accounting for 42.03%of the total energy consumption.In order to screen amine-based absorbents with high SO₂ absorption capacity and low desorption reaction heat,a screening method for amine-based absorbents in flue gas SO₂ capture process was proposed in this study.First,the acidity coefficient（pK_a）values of five organic diamines were predicted by quantum chemistry method.Then,the mathematical model of SO₂ absorption capacity and desorption reaction heat of organic diamine-acid-water ternary system absorbent in SO₂ capture process was established based on pK_a value.The results show that the SO₂ absorption capacity and the deprotonation reaction enthalpy of organic amines have a multi-objective"trade off"relationship,so it is not possible to simply pursue a high SO₂ absorption capacity and ignore the change of the reaction enthalpy.Finally,the numerical relationship between SO₂ absorption capacity and desorption reaction heat of organic diamines was quantified.Under the same SO₂ absorption capacity,the order of desorption reaction heat of each organic diamine was EDA>PZ>HEHPP>DIHEP>HEP.Taking EDA,PZ and HEP amine-based absorbents as examples,the process model of organic diamine-sulfuric acid-water ternary system absorbent for flue gas SO₂capture was biult,and the energy consumption distribution and process matching performance of the absorbent regeneration process were analyzed.The feasibility and energy saving of the overhead vapor direct compression heat pump process in the process of capturing SO₂ with three absorbents,EDA-H₂SO₄-H₂O,PZ-H₂SO₄-H₂O and HEP-H₂SO₄-H₂O,were discussed.The results show that the optimized process of overhead vapor direct compression heat pump under the PZ-H₂SO₄-H₂O absorbent system is the best choice for the flue gas SO₂capture process,and its regeneration energy consumption is 3.13 GJ/t SO₂.The regeneration energy consumption of the SO₂ capture process was reduced from the perspectives of absorbent screening and process flowsheet matching.This study has an important significance for the industrial application of amine-based absorbents in the flue gas SO₂ capture.