The Effect of Gas Atmosphere on the Grinding Efficiency of Limestone in Vibration Ball Mill

Abstract

In this report, the effect of gas atmosphere on the efficiency of size reduction of limestone powder is investigated experimentally by using a laboratory-scale vibration ball mill with ceramic balls (18mmφ). Air in the mill was evacuated and then replaced by other gases such as vapour phase of water, ethylether, methyl alcohol and acetone. The grinding experiment with a fine solid additive (aid) and that in a vacuum mill were also tried for comparison.The experimental results, shown in Figs. 3 and 4, reveal that the gas atmosphere of the above material increases the efficiency of limestone grinding distinctly, as same as the grinding with a solid state additive.These results can be represented by the following equations, which were proposed originally in the previous paper by one of the authors and have been modified here;SW>SWR; dSW/dE=ηr0 or (SW-SW0)=ηr0(E-Ei)SW>SWR; dSW/dE=ηr0-a(SW-SWR)n}(2)The improvement of grinding efficiency is found to be due to the increase of incipient efficiency of grinding, ηr0, the decrease of hindrance effect of grinding by fine powder produced in the mill, n, and the increase of the upper limit of Rittinger's range (SWR). The effect of these factors are summarized in Table I.From these, it can be estimated that the mechanism of the aiding effect of gas atmosphere is different from that of fine solid additive. And also there is no clear evidence that the dipole moment of gaseous material is an important factor of this aiding effect.