Fine coal flotation has been a longstanding problem in industry. Coal particles below approximately 38 microns in diameter are difficult to float, and the process consumes large amounts of reagents. Hydrodynamic analyses have shown, however, that the use of air bubbles smaller than those that are generated in conventional flotation machines (0.2 to 3 mm diameter) can improve the flotation rate and, hence, the coal recovery. Theoretically, a tenfold reduction in average bubble size should result in a thousandfold increase in the flotation rate constant at a given gas flow rate. Therefore, work has been done to use microbubbles less than 100 microns in diameter for the flotation of fine coal particles. Seven different U.S. coal samples have been tested in the present work. The feed size varies from -100 mesh to -500 mesh. Flotation kinetics tests have been conducted on some of these coal samples as a function of bubble size at a constant gas flow rate. The results show a drastic improvement in flotation rate with the use of microbubbles, which may account for the improved recoveries obtained with the microbubble flotation technique. In addition, test results obtained with ultrafine coal samples (-20 microns) indicate that the microbubble …

A review of the US uranium mining industry has revealed a generally depressed industry situation. The 1982 U/sub 3/O/sub 8/ production from both open-pit and underground mines declined to 3800 and 6300 tons respectively with the underground portion representing 46% of total production. US exploration and development has continued downward in 1982. Employment in the mining and milling sectors has dropped 31% and 17% respectively in 1982. Representative forecasts were developed for reactor fuel demand and U/sub 3/O/sub 8/ production for the years 1983 and 1990. Reactor fuel demand is estimated to increase from 15,900 tons to 21,300 tons U/sub 3/O/sub 8/ respectively. U/sub 3/O/sub 8/ production, however, is estimated to decrease from 10,600 tons to 9600 tons respectively. A field examination was conducted of 29 selected underground uranium mines that represent 84% of the 1982 underground production. Data was gathered regarding population, land ownership and private property valuation. An analysis of the increased cost to production resulting from the installation of 20-meter high exhaust borehole vent stacks was conducted. An assessment was made of the current and future /sup 222/Rn emission levels for a group of 27 uranium mines. It is shown that /sup 222/Rn emission rates are increasing …