Preparation of renewable collector from waste engine oil for clean flotation of fine coal with different oxidation degree

Abstract

High precision flotation of fine oxidized coal is difficult to achieve because of very low floatability. In this study, the influence of oxidation degree on floatability and functional group composition of coal was studied. In addition, the feasibility of renewable collector prepared from waste engine oil for fine coal flotation was also analyzed. FTIR analysis results showed that the oxidation degree had no significant effect on the types of functional groups. However, XPS analysis results illustrated that with the deepening of oxidation degree, the content of CC/CH groups decreased significantly, which caused notable decrease in floatability. For the unoxidized coal, the clean coal yield and recovery rate were 62.51 % and 73.77 % respectively, which provided evidence support that renewable collector could be used for the flotation of fine coal. Moreover, with the deepening of oxidation, the yield and combustible recovery were finally reduced to 12.39 % and 14.09 % respectively due to oxidation of the particle surface. Thus, grinding pretreatment was proved to improve floatability of oxidized coal significantly. The yield of clean coal and combustible recovery reached 47.78 % and 52.93 %, which was mainly due to the fact that the oxide layer on the particle surface was stripped off by grinding. The research also proved that the flotation temperature should not be lower than 20 °C. The flotation of fine oxidized coal was realized by using waste engine oil, which brought an alternative collector for flotation on the premise of eliminating environmental threat of waste engine oil.