Relationship between the breakage and wetting characteristics of lignite

Abstract

This paper reports the findings of an investigation of the breakage values of lignite to relate the wettability properties. The breakage values, obtained from grinding, are the specific rates of breakage (S-i) and the gamma of value the primary breakage function (B-ij), and the wettability parameter, which is also easily obtained from contact angle measurements and flotation tests, is the critical surface tension of wetting value of solid (gamma(c)). The grindings were carried out as dry, wet and wet with kerosene aided tests in a laboratory size porcelain ball mill. The products (-212 mum) of the feed sizes of -600+425, -425+300 and -300+212 mum of lignite ground in the mill have been tested to obtain the gammac values by contact angle goniometer and our new designed micro-flotation column cell. It is proposed that a relationship exists between the S-i and gamma(c) value of the lignite sample studied, i.e., higher the Si value from the breakage process, lower the gammac value in wetting processes, indicating less wettability in the physical-chemistry based separation methods. There is also another relationship found between the gamma value of B-ij (the fineness factor) and the gammac value, where gamma value increases with increasing gamma(c), value, except in the kerosene aided grindings. This means, coarser particles produced by grinding will behave more hydrophilic (i.e.. water wets the solid completely) in the wetting operations.