Study on Generating Acoustic Emission with Heating Coal for Application as Monitoring System for Underground Coal Gasification

Abstract

Underground Coal Gasification (UCG) is a technology to recover combustible gases by drilling holes and in-situ gasification. The establishment of a safe UCG system requires monitoring of the gasification reaction area because the gasification process that occurs in the underground is an invisible event. It is considered that Acoustic Emission (AE) monitoring is an effective technique for monitoring the underground gasification area since many fracturing activities occur in the coal seam due to coal heating. Therefore, the temperature condition of AE generations is investigated using the coal heating experiments and examines the applicability of AE measurement as a monitoring method for UCG. Measurements of temperature change and AE events with the thermocouples and the acceleration transducers during the coal specimen were heated. As a result, many AE events are found when the temperature of coal is changed and detected in the sensor where its location was near the heat source. Additionally, AE sources are expanded widely with the expansion of the high-temperature region based on the analysis results of the AE source location. It is possible to monitor the temperature change of coal and the expansion of the high-temperature region by applying AE measurement monitoring during UCG.