Effect of ultra-fine grinding on coal surface properties and ultra-clean coal separation

In order to understand the effect of ultra-fine grinding on the coal surface properties and super clean coal separation,Huainan gas coal (HN) and Taixi anthracite (TX) were investigated in this study. Fourier transform infra- red spectroscopy (FTIR),ζ potential meter,microcalorimeter and specific surface analyzer were used to analyze the variation of surface functional groups,electric potential and wettability after ultra-fine grinding. The effects of particle size,surface potential and wettability on the formation of floccules were studied. Also,combined with the separation re- sults of ultra-clean coal,the relationship between ultra-fine grinding,surface property change,floccules formation and the separation of ultra-clean coal was discussed synthetically. The results show that ultra-fine crushing changes the pro- portion of hydrophilic group and hydrophobic group on coal surface. With the decrease of particle size,the electric po- tential absolute value of TX coal decreases firstly,then increases. In the particle size of 8. 30 μm,the negative power is the weakest,the wetting heat is larger,more large scale floccules are formed in the process of mixing. When the usage of emulsified diesel oil is 67. 62 kg / t,the ash of ultra clean coal ash separated is 0. 68% and the yield is 97． 26% . Whereas,with the decrease of particle size,the electric potential absolute value of HN coal increases gradually,and the heat of wetting is monotonously decreasing. Under the same stirring intensity,the amount of floccules formed by fine particles is decreased,and the yield of ultra clean coal separated is reduced. The addition of dispersant effectively re- duces the ash of clean coal,and the difference of ash content is gradually increasing with the decrease of particle size.