Effects of Energy Input on the Laboratory Column Flotation of Fine Coal

Abstract

This study explored the effects of energy input and different energy increase patterns on the separation performance of a laboratory cyclonic–static microbubble flotation column in fine coal flotation. The energy input was changed by adjusting the circulating pump power and pulp residence time. Continuous flotation tests were designed by using five feed rates (i.e., different pulp residence time), which were 53.33, 80.00, 106.40, 133.60, and 160.00 g/min, and various useful power of the circulating pump (22.44, 30.14, 38.50, 46.86, 56.10, and 64.46 W). Results show that concentrate combustible recovery initially increased before reaching saturation distribution with increasing energy input absolute value. An ash content of 10.90% and combustible matter recovery of 92.84% were obtained at the energy input of 10098.00 J which is called the flotation saturation energy Es. Es is the essential condition and guarantee for a complete flotation process. A low ash content of clean coal was obtained with low energy input. With the increase of energy consumption, the additional coals recovered were coarse particles with low ash content and fine particles with high ash content. However, the ash content did not exhibit a significant change with the increase of energy input in this investigation. During the flotation process, a minimum critical flotation time T and critical circulation pump useful power P are required. If the P and T of a variable are less than the critical value, high combustible matter recovery could not be obtained by adding another variable to increase energy input. A reasonable mode of energy input was proposed that the absolute value of the energy input reaches Es; meanwhile, it ensures that each value of the P and T is greater than the critical values.