Interactive effects of CO2 mineralization in fly ash based on surface coverage model: mineralization time, liquid–solid ratio, and gas flow rate

• The interactive effects of three parameters on the mineralization mechanism was discussed. • Surface coverage model is suitable for reflecting the mineralization reaction of fly ash. • The application of mineralized product in the goaf area of coal mine has been proven feasible. In order to rapidly achieve the goal of global carbon reduction, the alkaline fly ash generated by coal-fired power plants can mineralize and sequester CO 2 from fossil fuel combustion, addressing both environmental pollution and global warming. This work investigates the ball-milled fly ash (BFA) mineralization under ambient condition, and optimizes the reaction time, CO 2 flow rate, and liquid–solid ratio via surface coverage model. As the CO 2 flow rate increases from 100 mL/min to 500 mL/min, the maximum CO 2 mineralization amount of the mineralized product increases from 90.9 g/kg to 92.54 g/kg. And the maximum CO 2 mineralization (98.6 g/kg) and amount reacted (11.16 mmol) are achieved at the liquid–solid ratio of 6:1 and the CO 2 flow rate of 300 mL/min. Moreover, the kinetic results show that the surface coverage model demonstrates excellent predictive capability for the mineralization process of BFA (correlation coefficient > 0.96). The best working conditions are that the CO 2 flow rate is 250–400 mL/min and the liquid–solid ratio is 5:1–6:1. When the mineralized product of BFA is used to treat coal samples, with the increase in the addition amount of the mineralized product, the maximum heat flow of the coal samples decreases from 112.7 mW to 74.4 mW, and the total heat release of the coal samples decreases from 1979.97 J/g to 1311.39 J/g. Therefore, the application of mineralized product in the goaf of coal mine has broad application prospects, which can not only properly solve the storage problem of mineralized product, but also effectively prevent spontaneous coal combustion.