PURPOSE: To apply rice hulls as a fattening nutrient of a concentrated feed, by heating and transferring dried rice hulls in a cylinder furnished with a tapered spiral groove at the inner surface, and crushing the carbonized and agglomerated rice hulls.

CONSTITUTION: A cylinder is furnished with a spirally threaded rod 11 which is revolved with a reduction unit. The inner wall of the cylinder has a spiral groove (e.g. the grooves 13, 14, and 15 having gradually narrowing pitch). The inner diameter of the cylinder 12 is properly designed, and the pitch of the spirally threaded rol 11 is set corresponding thereto. By the use of the above device, the rice hulls are slowly rotated and compressed to a cylindrical rice hull block which is as firm as rock. The outer wall of the cylinder 12 is heated with a burner 8 to promote the rotation and transfer of the rice hulls. The rice hull block having carbonized surface is discharged continuously through the nozzle tip 16.