1. Chinese National Engineering Research Center of Coal Preparation and Purification, China University of Mining and Technology, Xuzhou 221116, China
2. School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China
3. National Energy Group Ningxia Coal Industry Co., Ltd., Yinchuan 750411, China
4. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China