1. Key Lab of In-situ Property-improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, P. R. China
2. The In-situ Steam Injection Branch of State Center for Research and Development of Oil Shale Exploitation, Taiyuan University of Technology, Taiyuan 030024, P. R. China
3. State Key Laboratory of Clean and Efficient Coal Utilization, Taiyuan University of Technology, Shanxi 030024, China