Comparison and selection of flotation processes for the separation of fine and difficult-to-float coal particles

Abstract

ABSTRACT This work compares the performance of two coal preparation plants (CPPs) with similar flotation feeds to study the compatibility between flotation process and coal slime properties and to guide the design of flotation process and equipment selection. The two plants process coal slimes using “flotation column + flotation machine” and “flotation machine + flotation machine” flowsheet, respectively. The migration rules of different size and density fractions in the flotation were experimentally studied. The operation performance between the two flotation processes was comprehensively compared. The results show that, for feedstocks with high concentration of high-ash fine slimes and intergrown particles, the dual flotation processes can effectively reject intergrown particles and high-ash fine slimes, thereby reducing the ash of flotation concentrate to meet quality requirements. In the rougher flotation column, the flotation perfection index of < 0.045 mm size fraction is 55.67%, which is 4.74% higher than that of the rougher flotation machine. In the sorting of cleaner flotation machine, the particles with low density of < 1.3 g/cm3 are collected preferentially. With the extension of the flotation process, the intergrown particles and high-ash fine slimes gradually report to the clean coal products. The flotation recovery of > 0.25 mm size fraction is relatively poorer compared to other fractions. When the feed has high content of high-ash fine slimes, the process of “flotation column + flotation machine” is preferred. When the feed has high content of middle density fraction, the process of “flotation machine + flotation machine” is preferred for dual flotation. The upper limit of feed size should be strictly controlled in flotation.