Ex-situ experimental simulation of hard coal underground gasification at elevated pressure

Abstract The experiment of ex-situ hard coal gasification under the 0.5 MPa pressure was carried out by using oxygen, air and oxygen enriched air as gasification reagents. The main process objectives were to investigate the influence of increased gasification pressure and type of gasification reagents on the gasification efficiency. The results of 168 h experiment demonstrated that the most advantageous gasification conditions were obtained with pure oxygen and then with oxygen enriched air. The increase in the content of combustible gas components was proportional to the oxygen content in the gasification medium. It was proved that for each gasification stage there is an optimal flow rate of gasification medium which allows producing gas with the highest energy efficiency. The comparison between the process gas composition at elevated pressure UCG with the literature data on atmospheric pressure UCG operations revealed that under pressurized conditions the methane and carbon dioxide contents were significantly higher contrary to lower concentration of hydrogen and carbon monoxide.