Coal Properties and System Operating Parameters for Underground Coal Gasification

Abstract

Through the model experiment for underground coal gasification, the influence of the properties for gasification agent and gasification methods on underground coal gasifier performance were studied. The results showed that pulsating gasification, to some extent, could improve gas quality, whereas steam gasification led to the production of high heating value gas. Oxygen-enriched air and backflow gasification failed to improve the quality of the outlet gas remarkably, but they could heighten the temperature of the gasifier quickly. According to the experiment data, the longitudinal average gasification rate along the direction of the channel in the gasifying seams was 1.212 m/d, with transverse average gasification rate 0.069 m/d. Experiment indicated that, for the oxygen-enriched steam gasification, when the steam/oxygen ratio was 2:1, gas compositions remained stable, with H₂ + CO content virtually standing between 60% and 70% and O₂ content below 0.5%. The general regularities of the development of the temperature field within the underground gasifier and the reasons for the changes of gas quality were also analyzed. The “autopneumatolysis” and methanization reaction existing in the underground gasification process were first proposed.

Keywords:

• autopneumatolysis
• gasification rate
• oxygen-enriched steam gasification
• steam gasification
• underground coal gasification

Acknowledgments

This work was supported by the National Natural Science Foundations of China (Ratification Nos.: 59906014, 50276066, 20207014, 50674084). The technical contributions of Dr. Liu Shuqin and Professor Yu Li are gratefully acknowledged by the author.