TY - JOUR
T1 - Evaluation of coal combustion zone and gas energy recovery for underground coal gasification (UCG) process
AU - Su, Fa Qiang
AU - Hamanaka, Akihiro
AU - Itakura, Ken Ichi
AU - Deguchi, Gota
AU - Sato, Kohki
AU - Kodama, Jun Ichi
N1 - Funding Information:
This work was supported by the Japanese Society on UCG, Mikasa City, Center of Environmental Science and Disaster Mitigation for Advanced Research of Muroran Institute of Technology and a Grant-in-Aid for Scientific Research (b), 21360441, from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. The authors gratefully acknowledge their support.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2017/1/19
Y1 - 2017/1/19
N2 - During underground coal gasification (UCG) operations, evaluation of coal gasification cavity evolution and precise control of the underground reactor are important for efficient gasification. It is also essential to estimate the energy recovery of a UCG system and the whole gasification process to ensure an effective combustion and gasification rate. An experimental simulation of UCG using an artificial coal seam comprising a compacted broken coal block was conducted using ex situ UCG models. The main goal of the experiments was the establishment of evaluation methods for the gasification zone and energy recovery during UCG. To investigate the distribution and extent of fracture activity, and to evaluate the propagation of the combustion area in the UCG reactor, we used acoustic emissions (AE) monitoring. This was combined with traditional measurements of temperature variation and product gas content. This paper presents the results of AE analysis of the fracturing activities and damage mechanisms of the coal seam with respect to the UCG operations. From the results of AE source location, we found that the position and area of the crack concentration area, i.e., the gasification zone, can be inferred with comparative accuracy. This is important for in situ practical application of underground coal gasification. In addition, use of the distribution characteristics of AE information over time can also provide advanced warning, and help in timely adjustment of the operational parameters. The results of gas energy recovery were estimated with a proposed stoichiometric method based on measured product gas composition. Quantitative evaluation results include the gas quantities, coal consumption, and heating value yield of the produced synthesis gas. The coal consumption of the obtained energy recovery results also meets the estimated results when calculating the gasification volume with AE source locations (in an error range of about 10%). Therefore, the applied AE monitoring and gas energy recovery approaches may be considered attractive options for evaluating the coal gasification process and developing a safe and efficient UCG system.
AB - During underground coal gasification (UCG) operations, evaluation of coal gasification cavity evolution and precise control of the underground reactor are important for efficient gasification. It is also essential to estimate the energy recovery of a UCG system and the whole gasification process to ensure an effective combustion and gasification rate. An experimental simulation of UCG using an artificial coal seam comprising a compacted broken coal block was conducted using ex situ UCG models. The main goal of the experiments was the establishment of evaluation methods for the gasification zone and energy recovery during UCG. To investigate the distribution and extent of fracture activity, and to evaluate the propagation of the combustion area in the UCG reactor, we used acoustic emissions (AE) monitoring. This was combined with traditional measurements of temperature variation and product gas content. This paper presents the results of AE analysis of the fracturing activities and damage mechanisms of the coal seam with respect to the UCG operations. From the results of AE source location, we found that the position and area of the crack concentration area, i.e., the gasification zone, can be inferred with comparative accuracy. This is important for in situ practical application of underground coal gasification. In addition, use of the distribution characteristics of AE information over time can also provide advanced warning, and help in timely adjustment of the operational parameters. The results of gas energy recovery were estimated with a proposed stoichiometric method based on measured product gas composition. Quantitative evaluation results include the gas quantities, coal consumption, and heating value yield of the produced synthesis gas. The coal consumption of the obtained energy recovery results also meets the estimated results when calculating the gasification volume with AE source locations (in an error range of about 10%). Therefore, the applied AE monitoring and gas energy recovery approaches may be considered attractive options for evaluating the coal gasification process and developing a safe and efficient UCG system.
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U2 - 10.1021/acs.energyfuels.6b01922
DO - 10.1021/acs.energyfuels.6b01922
M3 - Article
AN - SCOPUS:85018522604
SN - 0887-0624
VL - 31
SP - 154
EP - 169
JO - Energy & Fuels
JF - Energy & Fuels
IS - 1
ER -