Air stream cotaining dust will enter along with the tangent direction of airin port.part of dust powder will fall into the bottom of cone because of the action of centrifugal force.the others will flow into the filtering bag along withair stream.air passes through filtering bag and enters into box body and is exhausted from the pipe of air port.powder dust is resisted by filtering bag at outside and cannot be discharged along with air stream.the effect of air and dust separation can be got.with prolong of time,the accumulated dust at the surface of filtering bag will be increased.so the resistance that passes through the filtering bag.according to certain order,pulse spraying and blowing system will carry out dust clean to each filtering bag in turn.spray the compressed air into the filtering bag and make the filtering bag expand quickly.a short counter air stream will be produced in fiber texture(opposite to the flow direction of filtering air).therefore the accumulated dust at outside surface of filtering bag is removed.