A two-stage process for fine coal flotation intensification

Abstract

Power input and flotation time are the two key factors influencing the efficiency of the fine coal flotation process. A new two-stage process is proposed in this investigation for intensifying fine coal flotation. The flotation process is divided into two parts: lowering energy input in the first stage and raising energy input in the second stage. Easily floated materials are recycled with low energy in the rapid floating section (first stage), and hard-to-float materials are compulsorily recycled using higher energy in the recycling section (second stage). A flotation energy consumption test system is established. Flotation tests were conducted in an XFD 0.75-L laboratory-scale flotation machine. The effects of energy input on the flotation rate constant in instantaneous flotation or flotation over a period of time were investigated. The results indicate that higher combustible matter recovery or lower concentrate ash content could be obtained using a two-stage process compared with a single-stage flotation process with the same energy consumption. Compared with energy input in the first stage of the flotation process, the energy added in the second stage of the flotation process would increase with flotation processing owing to the decreased rate of fine coal floatability in the first stage. The larger the floatability difference in the flotation process, the more energy must be used in the second stage of the flotation process. With the same energy input, the flotation tests indicate that lower ash content or higher combustible matter recovery could be obtained using the proposed two-stage flotation process.