Quantitative Evaluation of Underground Coal Gasification Based on a CO₂ Gasification Agent

Using carbon dioxide as a gasification agent for underground coal gasification (UCG) can not only reduce carbon dioxide emissions but is also expected to lead to a new natural gas technology revolution and ensure national energy security. To explore the effect of the oxygen content in oxygen-enriched carbon dioxide gasification agents on the results of gasification experiments, underground gasification experiments under different oxygen-enrichment conditions were designed, and quantitative parameters were used to analyze and evaluate the gas produced in the gasification experiments. The results showed that as the oxygen content in the oxygen-enriched carbon dioxide gasification agent increased, the CO and H2 in the combustible gas gradually increased, and the calorific value of the combustible gas also slowly increased, reaching a peak value under the gasification condition of 60% oxygen concentration, and then decreased slightly; the product formation rate and the gas production per unit mass of coal fluctuated. The coal consumption rate increased with time and was relatively stable. According to theoretical calculations for the gasification energy recovery evaluation system, the overall energy recovery rate was 56.34%, and the energy utilization rate was relatively high. Research on quantitative indicators based on gas production data has good practical significance for evaluating the gasification efficiency of UCG, which can be used to better evaluate and control the reaction process of UCG.