Abstract: In order to enhance the CO₂ sequestration efficiency of fly ash and promote its resource utilization in CO₂ mineralization sequestration and fire prevention and extinguishing projects, an optimization study was conducted on the reaction conditions and additive ratios of the fly ash mineralization process. A direct wet mineralization technique was employed to establish a gas-liquid-solid three-phase reaction system. The effects of water-to-ash ratio, reaction time, and gas flow rate on mineralization efficiency were systematically examined through an orthogonal experimental design. Range analysis and variance analysis were used to determine the primary and secondary influencing factors as well as the optimal parameter combination, thereby evaluating the impact of different conditions on mineralization performance. Additives including Na₂CO₃, NaCl, NaOH, and NaHCO₃ (at a concentration of 0.5 mol/L) were introduced, and a single-factor experiment was conducted to screen for the optimal formulation. The mineralization products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), while thermo gravimetric analysis (TGA) was used to quantitatively assess the CO₂ sequestration capacity. Fire suppression performance was evaluated through simulated coal pile spontaneous combustion experiments by monitoring temperature and CO volume fraction variations to verify the practical fire extinguishing effect. The results indicate that: in terms of mineralization condition optimization, a water-to-ash ratio of 4∶1, reaction time of 45 minutes, and gas flow rate of 150 mL/min yielded a CO₂ sequestration capacity of 57.75 kg/t, significantly surpassing other parameter combinations; among the additive selection experiments, 0.5 mol/L Na₂CO₃ exhibited the best performance by increasing the \mathrmCO_3^2- concentration in the liquid phase and maintaining an alkaline environment to promote CaCO₃ formation. Conversely, NaCl reduced mineralization efficiency by enhancing CaCO₃ solubility, while NaOH, due to its strong alkalinity, decreased calcite grain size, thereby inhibiting precipitation; XRD and SEM characterization confirmed the disappearance of portlandite (Ca(OH)₂) and quicklime (CaO) diffraction peaks in mineralized fly ash, with a significant enhancement of calcite (CaCO₃) peaks. The microstructural analysis revealed the transformation of the originally porous surface into a dense layer of spherical CaCO₃ particles, verifying the feasibility of the CO₂ mineralization pathway; in fire extinguishing experiments, the fly ash-based material effectively reduced coal pile temperatures below 120 ℃ within 600 seconds through oxygen barrier coverage, heat absorption via moisture evaporation, and penetration cooling mechanisms. The CO volume fraction stabilized below 30×10⁻⁶ after 180 seconds.