Study On Gas-Liquid Mass Transfer And Reaction Characteristic Of Absorption Process In Sodium Alkali FGD

Due to the high capital cost and the lack of technology support, the study of desulfurization in China is left behind. A novel wet FGD (Flue Gas Desulfurization) process is presented on the base of study of sodium alkali FGD and membrane electrolysis, which utilizing traditional ion-exchange membrane electrolysis and ultrasonic to regenerate sodium alkali fertile liquor and to reclaim sulfur dioxide as sulfuric acid. The absorption of SO₂ into sodium alkali solutioh is one of the key technics in the FGD technology. So in the thesis gas-giquid mass transfer and reaction characteristic of SO₂ absorption process in sodium alkali FGD was systematically investigated by both simulation and experiment.Based on the chemical equilibrium theory in liquid, the relationship between saturated pH of sodium alkaline solution, desulfurization capacity and partial pressure of SO₂ was obtained,which definitudes the ultimate parameters of absorption. Further the sodium alkali(Na₂SO₃) FGD process in a packing column was studied experimentally. Main parameters affecting SO₂ removal efficiency were studied for this process. These parameters include pH value of the absorption solution, liquid-gas ratio, superficial gas speed, inlet SO₂ concentration, temperature of absorption solution and initial Na₂SO₃ molar concentration. The experimental results show that SO₂ removal efficiency may be improved with the increase of pH,liquid-gas ratio and Na₂SO₃ molar concentration.And it may be dropped with the increase of other operating conditions. The effect of pH on the desulfurization efficiency is more obvious and the influence of L/G is not significant while L/G is more than 3L/m³.Based on the two-film mass transfer theory, a model for SO₂ absorption into Na₂SO₃ solution was put forward and established. The model was validated using experimental conditions in packed column. The equations in the model could be solved using MATLAB with boundary conditions obtained by rational estimation of the parameters involved. Then the solution of the model was used to calculate concentration profiles in the liquid film, SO₂ partial pressure, mass transfer rate, pH profiles, enhancement factor and individual resistances along the column. The calculated results were compared to experimental data and a good agreement was achieved.The formula to caculate the tower height of packed column in sodium alkali FGD was advanced based on the rate of chemical absorption. Making use of the method the optimized design of packed column in industrial FGD process was stated. Thus an integrated design process to the industrial chemical absorber in FGD was summarized in the paper.The results described the mass transfer-reaction mechanism and operating parameters characteristic of SO₂ absorption into Na₂SO₃ solution in packed column. The study in this paper provide a basic study for theoretical analysis and engineering design of the process of SO₂ absorption into sodium alkali solution and other wet FGD process, which is very inportant to the practical application of desulfuriation equipments.