Technology News 460 - prototype borehole miner selectively extracts gold from permafrost.
Savanick GA; Miller AL
Pittsburgh, PA: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, TN 460, 1997 Jul; :1-2
Assess the technical feasbility of mining small and/or deeply buried frozenplacer deposits from the surface through boreholes. Placer deposits in permafrost often contain up to 15% cobbles and boulders. Because of erratic loading on the bit caused by elasticity and heterogeneity of the ice-and-gravel matrix, these deposits are extremely difficult to excavate. The approach taken in this research project was to mine only the ore-bearing portion of the deposit using a high-pressure water jet to thaw the gravels and a downhole hydraulic-lift-type pump to bring the ore to he surface as slurry. Full-scale jetting tests in frozen gravel were completed, and the data were used to design a jet excavator. The excavator will deliver a water flow of 890 L/min through a 15.7 mm diam nozzle at 6,900 kPa. The prototype slurry pump was designed to lift minus 15 cm gravels to the surface from a depth of 15 m.
Mining-industry; Jet-Pumps; Gravel; Slurry; Gold; Boreholes
National Institute for Occupational Safety and Health, Pittsburgh Research Laboratory, 626 Cochrans Mill Road, Pittsburgh, PA 15236
National Institute for Occupational Safety and Health