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1 2020

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Understanding the difficult selective separation characteristics of high-ash fine coal

Yang Zili, Liu Min, Chang Guohui, Xia Yangchao, Li Ming, Xing Yaowen, Gui Xiahui

Physicochemical Problems of Mineral Processing

2020

Vol. 56, iss. 5

874--883

As the supply of high-quality coals decreases and mechanical coal mining becomes more widespread, the high selective recovery of high-ash fine coal has become a prominent problem in the flotation process. Herein, we discuss the main reasons why the selective separation of high-ash fine coal is difficult. The analysis of high-ash fine coal properties shows that coarse particles (0.25-0.5 mm) account for 22.53% of the total size fraction and that 57.90% of the coal is moderate- or high-density (+1.4 g/cm3) intergrowth. Grinding experiments show that the traditional rod mill has little impact on the liberation of the intergrowth. Instead, its main function is to adjust the particle size composition to ensure that the particle sizes of high-ash fine coal are within the particle size range suitable for flotation. The flotation results show that a clean coal yield of 30.42%, with a 12.46% ash content, is obtained with the optimal flotation parameters through the roughing and cleaning flotation process. However, the flotation results also show that in the separation of high-ash fine coal, it is difficult to obtain clean coal with a high yield and low ash content at the same time. This is mainly due to the similar floatability of moderate-density and low-density coal particles, which allows a large number of moderate-density coal particles to be recovered, and a significant slime coating of clay on the coal’s surface that is generated during the flotation process. The results of this work provide valuable guidance for high-ash fine coal industrial flotation applications.