Influence of Key Factors on the Characteristics of Flue Gas Desulfurization of Basic Aluminum Sulfate by Bubbles.

Abstract

Temperature, reactant concentration, bubble flow field characteristics, and mass-transfer characteristics play an important role in flue gas desulfurization of basic aluminum sulfate (aluminum base). The influence of various factors on desulfurization efficiency (ηabs) was determined from the macroscopic and microscopic levels through experiments and numerical simulations. The temperature of absorption solution had a significant effect on ηabs, and low temperature was advantageous for SO2 absorption performance of aluminum base. The value of ηabs increased with increasing reactant concentration. When the aluminum base concentration was higher than 50%, ηabs remained above 90%. The low aluminum base shortened the beginning time of the rapid decline of ηabs. This outcome was related to the low concentration of active Al2O3. At a low concentration range of 2000–5000 ppm of inlet SO2, the reaction rate determined the ηabs level, and gas-phase mass-transfer resistance was the main factor restricting the increase in ηabs. However, reaction rate and gas-phase mass-transfer resistance determined the ηabs level when the inlet SO2 concentration was as high as 50 000 ppm. The aeration rate affected the bubble size, number, and diffusion state. In addition, a higher aeration rate reduced the gas–liquid contact time and speeded up the consumption of aluminum base. As a result, bubbles along the absorber height showed different desulfurization characteristics, that is, 0–0.1 m was the initial stage of bubble formation and desulfurization (the ηabs was lower than 15%), 0.1–0.34 m was the main stage of bubble diffusion and desulfurization (the ηabs rapidly increased to 86.4%), and 0.34–0.4 m was the stable stage of desulfurization (the ηabs slowly increased to 92.5%).