| 摘要 |
Fine refuse coal, e.g. anthracite culm, is cleaned by first subjecting it to froth flotation with flotation reagents in amount insufficient to float the fine particles having a high ash content so that the concentrate obtained contains a major portion of the fine low ash coal, and then classifying the tailings from the flotation operation, e.g. by screening, rejecting the fine sizes, and floating the coarse sizes with an amount of reagent sufficient to float the coarse low ash coal. The first flotation is preferably carried out with a frother consisting of a mixture of paraffin alcohols having from 7-10 carbon atoms stabilized with a hydrocarbon, as described in Specification 446,418, and for the second flotation a hydrocarbon collector, e.g. kerosene, is added. One or both of the concentrates may be cleaned by re-floating and the concentrates may be kept separate or mixed. In an example, after flotation of the finest coal with the alcohol-hydrocarbon frother, the tailings are classified in the presence of sodium silicate, and the coarser coal floated with kerosene.
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