Substantiation intoparameters for the technology of co₂ utilization in underground coal gasification

Purpose. To justify the parameters of the CO₂ utilization technology as part of the blown mixture during underground coal gasification and subsequently determine the energy characteristics of the producer gas. Methods. The investigation of the CO₂ utilization process within the blown mixture was conducted under laboratory conditions using a specially designed test setting. The research was carried out in three sequential stages: the supply of an air mixture (O₂ – 21%), an oxygen-enriched mixture (O₂ – 35%), and an air with carbon dioxide mixture (CO₂ ≤ 30%). The calorific value of the producer gas was determined according to the “adaptivity” rule. Results. The study substantiated the feasibility of utilizing CO₂ within the blown mixture during underground coal gasification. Energy characteristics of the producer gas were determined based on the different methods of feeding the blown mixture. It was established that when CO₂ is supplied as part of the blown mixture, its maximum concentration reaches 22.3%, at which the calorific value of the producer gas is 6.32 MJ/m³. Originality. The dependencies of CO₂ output and the calorific value of the producer gas on the parameters of the blown mixture feeding were established with a focus on CO₂ utilization technology. A CO₂ utilization coefficientwas proposed to assess the efficiency of the gasification process; this coefficient is evaluated based on the CO₂ concentrations in the blown mixture and in the producer gas, with the latter varying linearly at the limiting CO₂ concentration in the blown mixture of no more than 22.3%. Practical implication. The study established the limiting parameters for CO₂ concentration in the blown mixture during underground coal gasification, which enable the prediction of the lower heating value (LHV) of the produced gas and the overall process efficiency.