Results of the tracer tests during the El Tremedal underground coal gasification at great depth

During the underground coal gasification (UCG) experiments at Alcorisa, Spain, a series of helium tracer tests were carried out to follow the underground cavity growth. The volume of the cavity increases progressively with the cumulated quantity of oxygen injected. Models based on exchange of matter between the flowing fluid and a transverse dead zone were used. Results indicate that the gasifier behaves almost like a small number of stirred tanks in series with a high level of back mixing.