| Flue gas desulfuration by wet processes has been one of the most important techniques by now. Further researches have been made in this work to investigate the fluid dynamic performance of cocurrent gas-water desulfuration operation, the improved desulfuration process by limestone slurry and the absorption behavior of SO2 in ionic liquids. All the efforts are made to develop the potential in increasing the efficiency and stability of SO2 removal and to give a full summary on the wet flue gas desulfuration. The main contents are described as follows.Fluid dynamic properties of SO2 absorption by using upflow gas-water cocurrent in a packed column have been systematically studied, including the flow-regime and holdup of cocurrent desulfuration in a structured and random packed column, the effect of liquid spray density on the total pressure drop, the effect of gas phase loading factor on the pressure drop, the effects of liquid-gas ratio and gas phase loading factor on the efficiency of SO2 removal and the mass transfer coefficients for SO2 cocurrent absorption in the region of jet flow.The effects of velocity of inlet gas, liquid-gas ratio, SO2 concentration of inlet gas and pH value on the limestone slurry desulfuration were investigated to improve the mass transfer performance. In addition, the investigation of inorganic additives, organic additives and composite additives on enhancing the dissolution of limestone as well as the SO2 removal performance by the limestone with the addition of the additives were also carried out. It can be stated that a maximum value can be found for the relation between SO2 removal efficiency and gas velocity. The concentration of SO2 in inlet gas and the pH value of the limestone slurry are in inverse proportion to minimum liquid-gas ratio with the most suitable range of pH of 5-6. The effects of the additives on the efficiency of SO2 removal are in the order of adipate+NaCl > adipate > NaCl+adipate > NaCl, and a maximum value for the additive amount of the additives can be observed. Meanwhile, liquid phase mass transfer process has been described using film theory to further investigate the enhancing effect of limestone absorption SO2. It can be seen that a positive correlation exists between the dissolved Ca2+ concentration and the SO2 inlet partial pressure, while the effect of initial limestone concentration on the Ca2+ concentration can be neglected. SO2 absorption rate is basically linear with SO2 inlet partial pressure, whereas the effect of initial limestone concentration on SO2 absorption rate can be neglected. The enhancing factor increases with the increase of the dissolved Ca2+ concentration and the decrease of the limestone particle size and the total sulfite concentration. The enhancing effect is more obvious with the less concentration of sulfite.The results indicate that 1,1,3,3-tetramethylguanidium lactate, as a desulfurizing agent with an excellent performance, can be used as a substitute for the traditional absorbents, and this ionic liquid with a high recycling rate and a low loss rate can be used to carry out SO2 absorption-desorption experiment continuously. The vapor liquid equilibrium relationship of SO2-[C6MIm][Tf2N] system can be well described by the Flory-Huggins model, which can prove to certain degree that dissolving action of SO2-ILs systems is caused by entropy effect... |
