Abstract：Contact angle measurement EasyDrop DSA20 was used to study the wettability of three different coal samples after wet ultra-fine grinding. The surface tension of coal particles and coal-water interface,the adhesion work of coal-water system were calculated. The results show that the hydrophobicity of two kinds of low rank coals including Shenmu non-caking coal and Huainan gas coal is enhanced after wet ultra-fine grinding. For a long time of wet super fine crushing, the hydrophobicity of Taixi anthracite coal weakens. After ultra-fine grinding, the variation tendency of coal surface tension and adhesion work of coal-water system is in contrast with the contact angle.

Keywords: ultra-fine grinding; wettability; surface tension; adhesion work