Coal washing apparatus

An apparatus for separating particles of intermediate specific gravity from an aggregate containing said particles as well as fine and coarse particles of a higher specific gravity by use of a liquid of lesser specific gravity than any of said particles, which comprises:

• a first axially rotatably inclined cylindrical housing having an open upper end and a closed lower end;
• a first helical ribbon flight secured to the inner periphery of the first housing for transporting fine higher specific gravity particles to the upper end of the first housing;
• a second cylindrical housing of substantially uniform cross-section throughout its length concentrically disposed within the first housing for receiving the aggregate therein, and being secured to said first housing within said first ribbon flight, said second housing having an open upper end and a centrally disposed open partially restricted lower end at the closed end of the first housing and extending through the central portion of the closed lower end of the first housing for discharging the intermediate specific gravity particles and liquid of lesser specific gravity, the lower portion of said second housing enclosed within the first housing having a plurality of perforation means in the sidewalls thereof for admitting the fine higher specific gravity particles therethrough;
• a second helical ribbon flight secured to the inner periphery of the second housing and open in the center portion thereof for transporting coarse higher specific gravity particles to the upper end of the second housing;
• means for introducing said liquid of lesser specific gravity into said second housing;
• means for introducing said particles into said second housing;
• and
• means operably connected to the first housing for rotating said first housing.