Evaluation of gasification cavity growth and gas energyrecovery in underground coal gasification

In order to realize the accurate detection and control of underground coal gasification (UCG) process，the monitoring on the development of gasification cavity and the evaluation on the energy recovery are important to realize an efficient UCG.In this paper，two different gasification channel models were constructed by artificial coal seam for the UCG simulation experiment.Through layering stratified temperature detection method，this study investigated the development of gasification cavity and combustion cavity，the effect of different gasification agent composition(O2，CO2，H2O，etc.)，ratio，flow rate and other experimental operating parameters on gas composition and calorific value.At the same time，an evaluation method of energy recovery based on stoichiometry theory was established，and the gasification efficiency，coal consumption and coal gas production of the whole underground gasification process were evaluated.The results show that the layering stratified temperature detection method can reflect the development of combustion zone and combustion cavity.The evolution range and rate of gasification region are related to the type of gasification channel，the range and rate of evolution in two experiments with the link hole model are more than 2 times of that with the shaft hole model.The high temperature environment of UCG is conducive to the continuous gasification process，under the condition of high temperature，the proportion of combustible gas in the generated gas increases.The coal consumption and energy recovery are closely related to the gasification channel model.Comparing two models，with the link hole model，the calorific values of gas is higher and the energy recovery is also higher than that with the shaft hole model.