Research On SO₂ Desorption Method From Sodium Alkali Fuel Gas Desulphurization Rich Solution By Ultrasound

Flue gas desulfurization (FGD) is one of the most effective technologies to control sulfur dioxide pollution. Currently, FGD technology commonly used have some problems of abandonment or low utilization of most desulfurization by-product and secondary pollution for environment, which hinder the development of these existing FGD technologies. Therefore, the development of new FGD technology with small waste production and SO2 resources recovery is particularly important, in which, SO2 enrichment and FGD solution regeneration is a key point. In this thesis, a new ultrasonic desorption regeneration method of desulfurization rich solution was explored, by using"cavitation"and"fountain"of ultrasound to promote SO2 removal, thus SO2 gas was enriched and at the same time desulfurization rich solution was regenerated.Based on the chemical equilibrium and gas-liquid mass transfer equation, the relationship between desorption capacity with pH value, sodium ion concentration and temperature was deduced, and the mass transfer rate equation of SO2 gas was also obtained in the desorption process. These could provide the theoretical basis for future desorption research.According to the contrast of ultrasound desorption with conventional heating desorption experiments, the results showed that ultrasound could significantly promote the SO2 desorption from sodium alkali desulfurization rich solution in the pH value range of 2.0 to 4.0, and the promotion of ultrasound desorption increased with decrease of pH value. When the pH value of desulfurization rich solution was 2.0, the ultrasound desorption rate increased by 1.38 times than that of heating desorption. The effect of ultrasonic desorption weakened with the pH value increased, and when the pH value was higher than 4.0, the promotion was ignored. Furthermore, by analyzing the composition of desulfurization rich solution with different pH value, the results indicated that the use of ultrasound accelerated mainly the decomposition from H₂SO₃ to SO2, thus total volume mass transfer coefficient K L?a was enhanced in the desorption process.The experiments of ultrasonic desorption of sodium alkali desulfurization rich solution were carried out in the self-designed ultrasonic reactor. The influence of various parameters, including the depth of desulfurization rich solution, the initial pH value, temperature, sodium ion concentration and ultrasonic electric power, on SO₂ desorption amount and desorption rate were researched. Moreover, through the comprehensive analysis of above parameters, a economical and efficient operating condition was obtained, which was depth of desulfurization rich solution of 7.9 cm; initial pH value of 2.0, temperature of 60℃, NaHSO3 concentration of 1.0 mol/L and ultrasonic electric power of 30 W. Under this optimal condition, 0.267 mol/L of desorption amount and 85 % of desorption efficiency were yielded after 180 min ultrasonic vibration.In the desorption process, the water evaporation amount per minute under ultrasound desorption was slightly higher than that with pure heating desorption. Conversely, the total water evaporation amount was lower than that heating desorption at the same SO₂ desorption amount. Therefore, the energy consumption was saved owing to the higher SO₂ desorption rate under ultrasound. In addition, the study on sulfate radical content in desulfurization rich liquid showed that it remained stable level generally, thus it could be considered that ultrasound could restrain the conversion from sulfite radical to sulfate radical, and avoid deterioration of desulfurization solution in the regeneration process.This thesis mainly focused on the method and mechanism explorations of ultrasound desorption from sodium alkali desulfurization rich solution, and it could provide new ideas for the regeneration technology of FGD rich solution.