Estimation of Gasification Area of Underground Coal Gasification by Using Acoustic Emission Monitoring
- Akihiro Hamanaka (Kyushu University) | Ken-ichi Itakura (Muroran Institute of Technology) | Fa-qiang Su (Henan Polytechnic University) | Gota Deguchi (Underground Resources Innovation Network) | Jun-ichi Kodama (Hokkaido University)
- Document ID
- International Society for Rock Mechanics and Rock Engineering
- ISRM International Symposium - 10th Asian Rock Mechanics Symposium, 29 October - 3 November, Singapore
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society for Rock Mechanics and Rock Engineering / Society for Rock Mechanics and Engineering Geology
- Underground Coal Gasification, Fracturing Activity, Acoustic Emission
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- 12 since 2007
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Underground coal gasification (UCG) is a process of producing combustible gases by the in-situ conversion of coal into gaseous products. Coal resources abandoned under the ground for either technical or economic reasons can be recovered with economically and less environmental impacts by UCG; therefore, this technology is regarded as a clean coal technology. UCG has several advantages of low investments, high efficiency, and high benefits compared to conventional coal gasification. However, some environmental risks such as gas leakage, surface subsidence, and underground water pollution are difficult to control because the process is invisible. The reactor in UCG is unstable and expands continuously due to fracturing activity caused by coal combustion. It is, therefore, considered that acoustic emission (AE) is an effective tool to monitor the fracturing activities and visualize the inner part of coal. For this study, UCG model experiments were conducted using coal blocks of 0.55 × 0.60 × 2.74 m to discuss the applicability of AE monitoring for the estimation of the crack generations during UCG process and the extent of the gasification area. Temperatures were also monitored because the crack generations were strongly related to thermal stress occurred by coal combustion and heat transfer. The monitoring results of AE agreed with the measured data of temperatures and the gasification area; the source location of AE was detected around the region temperature increased and the gasification area. Additionally, the gasified coal amount can be predicted by using the data of product gas. Therefore, AE monitoring combined with the prediction of reacted coal amount are expected to be a useful tool as monitoring system of the gasifier in the underground.
Underground coal gasification (UCG) is a technique to extract energy from coal in the form of heat energy and combustible gases through the chemical reactions in the underground gasifier. This technique enables to utilize coal resources that remain unrecoverable in underground due to either technological or economic reasons. Most coal mining in Japan was closed by 2001 because of complicated geological conditions for mining development and high prices of domestic coal. However, abundant unused coal resources remain underground, but they are not recoverable because of technical and economic reasons. Such coal resources are estimated to be 30 billion tons. For that reason, UCG has a great potential to recover vast amounts of energy from these coal resources.
|File Size||4 MB||Number of Pages||10|