When flotation machine works, slurry is inhaled from the bottom of the trough to the space between impellers. Meanwhile, the low_pressure air send by fan is sent to this area through the air distributor in the hollow shaft. After sufficient mixing, the slurry is pushed out by the impeller, and then goes to the whole trough. When the froth rises to the stable level, after the enrichment processing, froth overflows to the froth trough from the overflow weir. Another part of ore slurry flows to lower part of impeller for the re_mis with air. The remained slurry flows to the next trough until becomes residue.