heat source 80 from one end thereof 312 the other end thereof 311 is opened towards the pouring hopper 20 the hot air advances towards the mixing hopper 60 from the upper part of the pouring hopper 20 in order to provide this there is a vacuum under the pouring hopper 20 and the hot air is drawn by means of vacuum by means of this the hot air advances by passing through each point of the pouring hopper 20 and through inside upper side and lateral side of the drying boxes 22 inside the pouring hopper 20 there is a directing part 211 on the wall 21 of the pouring hopper 20 the directing part 211 directs the hot air towards the end part 311 of the air inlet pipe 31 there is a curved part 314 at the end part of the air inlet pipe 31 the hot air enters the pouring hopper 20 through said curved part 314 particles which are in powder form exit the rap heated inside the pouring hopper 20 there is a separator 40 for precipitating and accumulating said powder particles said separator 40 is positioned in a vertical manner at the lateral part of the pouring hopper 20 the separator 40 comprises an inlet part 41 which is opened to the pouring hopper 20 the hot air passes to the separator 40 through the pouring hopper 20 by means of said inlet part 41 the cross section of the separator 40 is wider than the cross section of the pouring hopper 20 by means of this when hot air enters into the separator 40 because of the cross section width the speed of the hot air decreases.