GB493971A - Improvements in flotation of fine refuse coal - Google Patents

Abstract

Fine refuse coal, e.g. anthracite culm, of 3/32 inch or less, is cleaned by subjecting it to froth flotation in froth flotation cells under conditions which will produce a concentrate having a high percentage recovery of the low ash coal but of relatively low grade, and subjecting the concentrate to classification, e.g. by screening, and rejecting the finer material. The concentrate may be classified into two or more sizes, the finest size being rejected and the intermediates, if desired, cleaned by flotation. In the preferred method of treatment the coal is floated in a series of cells with progressive addition of reagents, and only the concentrates from the later cells are classified. For example, anthracite culm after conditioning with sodium silicate is floated first with a frother consisting of a mixture of paraffin alcohols having 7-10 carbon atoms and hydrocarbons, as described in Specification 446,418, and then in later cells with additions of kerosene or kerosene and frother. The concentrates from the first three cells are not further treated and may be kept separate or mixed, that from the fourth cell is sized into two or three grades, the finest being rejected and the intermediate, in the case of three grades, cleaned by flotation, and the concentrate from the fifth cell is screened into two grades and the finer rejected. Specification 446,418 is referred to.