| Red mud is a solid waste residue in the production process of alumina, which a lot of stockpiling would cause serious environmental pollution. And long-term storage of red mud will lead to the decrease of content and activity of desulfurization effective componentsin(eg. Calcium-based group), thereby affecting the efficiency of flue gas desulfurization. In order to improve the efficiency of red mud flue gas desulfurization, this paper on thermal activation of red mud have been made to prepare an activated red mud desulfurizer(ARMD) under mixed conditions of activated carbon. And then investigated the relationship between ARMD physicochemical properties and desulfurization performance among the investigated conditions of thermal activation, and desulfurization mechanism ARMD was preliminary probed. On this basis, the desulfurization experiment of bubble absorption tower was carried out to determine the optimum operating parameters and then to investigate the desulfurization stability of ARMD. The main results of the paper were as follows:ARMD preparation conditions test results showed that: Tthe removal efficiency of ARMD could reach more than 85% under the conditions of activated carbon prepared. The effective components of ARMD could not be fully activated when the conditions temperature lower than 900℃ or the activation time less than 15 min. However, when the activation temperature over 1000℃ or the activation time more than 20 min would make ARMD sinter or melt, and generated melilite and inert material,Which led to the reduction of ARMD desulfurization efficiency. The optimal preparation conditions of ARMD were as follows: C/R=1:20, the thermal activation temperature of 900℃, thermal activation time of 15 min.ARMD Characterization Analysis results showed that: after thermal activation treatment, specific surface area of ARMD were increased, the proportion of middle / large pore was increased, the microscopic structure was more reasonable and was beneficial to the diffusion of reactive ion, prevented the blockage of the small hole by the product of the desulfurization reaction. After activation treatment, the CaSO4?1/2H2 O of ARMD was decomposed effectively, CaCO3 and other substances of ARMD occured a series of reaction in the activation process, in addition to part into CaO, the rest converted into 3CaO ? Al2O3? SiO2? 4H2O、CaO ? Al2O3? 2SiO2 and 2CaO ? Al2O3? SiO2.ARMD desulfurization mechanism was discussed using dual-mode theory, and the optimum conditions of desulfurization process and stability test of ARMD in bubbling absorption tower were investigated. The results indicated that: The pH value of desulfurization slurry was an important factor to determine the dissolution rate of SO2 and ARMD active components in the solution. When the concentration of H+ increased, the reaction was carried out reversely, which hindered the mass transfer of SO2 gas and ARMD effective components in solution. Under different pH conditions, the morphology of Fe(Ⅲ) / Fe(Ⅱ) in solution and the catalytic oxidation mechanism of SO2 were different, and the desulfurization efficiency was also changed.At the temperature of 25℃, SO2 concentration of 1500 ppm conditions, the optimum operating conditions showed blowed: pH value of about 4.5, solid-liquid ratio of 1:5, the gas flow rate of 3.0L/min. Under the conditions, ARMD desulfurization efficiency was up to 86.9%. The desulfurization efficiency remained stable and it had a certain adaptability to different concentrations of gas when inlet gas concentration of SO2 ranged from 400 to 2000 ppm and ARMD existed in a bubble absorber. Under continuous operating operation, the efficiency of desulfurization could reach a stable state, the desulfurization efficiency could be maintained at more than 87%. |
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