Column Flotation of Subbituminous Coal Using the Blend of Trimethyl Pentanediol Derivatives and Pico-Nano Bubbles

Abstract

Subbituminous coal, a low rank of coal, is difficult-to-float using the conventional flotation process by a single frother such as MIBC and a single collector such as kerosene or fuel oil. The froth flotation of the fine coal separation process is based on the differences of wettability between coal and mineral particles. The formation of oxygenated functional groups on coal surface can reduce its hydrophobicity. This result makes the coal more difficult to float by oily collector alone. Previous work shows that the surfactant can be used to activate the oxygenated surface, by selecting the group of such as fatty acids, trimethyl pentanediol derivatives, hydroxylated ether amine, etc. In the present study, the blend of trimethyl pentanediol derivatives as frother and kerosene as collector are used in column flotation of subbituminous coal. The frother made of trimethyl pentanediol derivatives provides better spreading of oily collector, froth stability, and selectivity. The flotation column used is equipped with a static-mixer and a venturi cavitation tube for pico and nano bubble generation, and a double funnel tailings separator. Three stages of statistical design of experiment of column flotation are conducted to optimize operation conditions. The results show that 96.87% of combustible material recovery and 13.13% of clean coal ash content are obtained. The effect of pico and nano bubbles is to increase the recovery of low rank coal. Furthermore, clean coal with the combustible material recovery of 81.2% and ash content of 9.1%, by desliming minus 45 μm size fraction particles of feed coal before column flotation are also achieved.