Fine coal flotation process intensification-part Ⅲ: interface intensification of low-rank and oxidized coal

The flotation of low-rank/oxidized coal is low in efficiency and high in consumption of collector because of the presence of a large quantity of well-developed voids and functional groups on surface of such coal. It is found that interface intensification is an important way for the improvement of flotation performance in this instance. Following an introduction to a new kind of polar complex collector developed based on analysis of interaction between the oxygen-containing functional groups and collector,a study is made in the paper of the effect on enhancement of flotation interface of low-rank/oxidized coal produced by polar compound collector and mechanical compression of surface voids. The work made covers: verification of test result through thermodynamic analysis; treatment of difficult-to-float coal through mechanical thermal compression using mechanical thermos compressor; detection of the change of surface property before and after mechanical thermos compression treatment using X-ray photoelectron spectroscopy（ XPS）,mercury intrusion porosimetry,specific surface area meter and Fourier transform infrared spectroscopy; and calculation of surface free energy of coal sample using Van Oss-Chaudhury Good theory. Through the studies made,the effect of mechanical thermos compression on surface physico-chemical structure of lignite has been brought to light. The research-derived achievements may serve as a reference for better understanding of the effect of mechanical thermos compression process on improvement of hydrophobicity and interface intensification of lignite.