Prevention of contamination of a dried product, deformation of particles, and a change of particle size distribution. The system includes: a solid-liquid separator in which a processing material is supplied between a pair of endless separation filter cloths wound around an outer periphery of a separation roll, and is dehydrated by being squeezed therebetween and also by ventilation gas passing from a ventilation port formed in an outer peripheral surface of the separation roll; and a horizontal rotary dryer provided on a subsequent stage of the solid-liquid separator, wherein carrier gas is made to flow in a rotating shell of the dryer in a cocurrent manner in the same direction as a conveyance direction of the processing material.