The air flow enter the washer lateral between the water level and the perforated steel plate. The air passes through the holes of the perforated steel plate to the upper part of the washer. Through the washer pump the washing water is pumped over the perforated plate and sprayed out through nuzzles. The up coming air stream and the down going washer water are building an intensive foam bed. In that bed the air and the particles are brought to the water droplets. The air flow with the water droplets are leaded further up to the droplet separating zone. Here the droplets are separated from the air stream and the air stream leaves the washer above the separation zone through the washer hoot.