Physical cleaning of waste coal by dissolved-CO(sub 2) flotation. Final technical report, September 1, 1992--August 31, 1993

摘要

The coal wastes generated from coal mining operations and coal cleaning processes contain fine and ultrafine coals. Recovery of the fine/ultrafine coal from the coal wastes reduces the loss of useable fuels and the environmental impact. The objective of this project was to use dissolved-CO(sub 2) technology to generate ultrafine bubbles to separate fine/ultrafine coal from pyrite and other mineral matter in the coal wastes. The Illinois No. 6 coal waste used in the project was the underflow from a refuse thickener. The concentrations of the major trace metals are much higher than those found in Illinois Basin Coal database for Illinois No. 6 coals. Bench-scale conventional flotation tests of the waste coal were performed under various conditions using a 4-liter Wemco flotation cell. The tests were performed to determine the chemical dosages and flotation conditions used in dissolved-CO(sub 2) column flotation. The waste coal samples were subjected to dissolved-CO(sub 2) flotation in a 2-inch diameter microbubble column under various test conditions. The flotation performance as affected by each test variable was compared. For most of the tests, the Btu recovery was above 80%, the pyrite rejection was about 60%, and the ash rejection varied from about 45% to 76%. Dissolved air was used in one test for comparison. The waste coal samples were also subjected to typical microbubble flotation. As compared to microbubble flotation, the dissolved-CO(sub 2) had higher yield, higher Btu recovery, less pyrite rejection, and less ash rejection. Almost all of the major trace metals had a substantial reduction in concentration by dissolved-CO(sub 2) flotation, particularly for cadmium, chromium, nickel, and lead. (ERA citation 19:011457)