Simulation and Experiment Study on Carbonization Process of Calcified Slag with Different Ventilation Modes

To solve the problem of high alkali red mud stockpiling, a new method of “calcification and carbonization” to treat Bayer red mud was proposed. The carbonization process of calcified slag in the process was mainly studied in this paper, that is, the hydrogarnet in the calcified slag was decomposed by CO₂ at high temperature and high pressure. Firstly, the water model experiments were conducted under different ventilation modes to investigate the influence of pressure on the bubble disintegration and dispersion in the 1 L high pressure transparent autoclave. The results showed that the number of bubbles was less, and the mean diameter was smaller under the airtight conditions whereas the number of bubbles was more, and the effects of gas bubble disintegration and gas liquid mixing were better under the circulated condition, which was beneficial to the mass transfer and the chemical reaction rate between gas and liquid. Secondly, the influence of these factors on the carbonization process of calcified slag was verified in the 2 L high temperature and pressure reactor. The optimum experimental conditions were obtained by measuring the carbon content of the slag in the reaction process. The results showed that the reaction time under the circulated condition was reduced by 23% compared with airtight conditions.