The device comprises an alkali feeding pipe, an acid feeding pipe, a mixing chamber, a rotation mixing chamber, and a nozzle.

The slag is sent into the hopper by the belt conveyor or bucket elevator and sent into feed end through feeding pipe of feeder hopper.

The multistage powder selecting machine comprises a shell, a motor, a rotor, wind guide blades, cyclone cylinders, a feeding pipe and a wind converging pipe;