PURPOSE: To make dust usable as it is as a substitute for ballast or for land reclamation without causing secondary pollution by mixing the dust to form lumps mixed with a binder in a specific high speed rotary mixer, and molding this with a molding machine.

CONSTITUTION: A high speed rotary mixer has a high speed revolving impeller provided with floating vanes 3 in the lower part and agitating vanes 3' above these, and fine-powderlike refuse (dust) discharged from various incineration furnaces is charged through a feed port 12 under the revolution thereof. On the other hand, when a binder is introduced through an inflow port 7, the vanes 3 float the contents and the vanes 3' shear and agitate these, thereby sticking and coating the binder uniformly on the dust in a short time. This powder is removed from the mixer, and while its temp. is high, it is compressively molded to arbitrary shapes with a molding machine. Tar, asphalt, water glass, and the like are used for the binder, and if heating is necessary, a heating jacket 14 is provided to the vessel.