A continuous gravity flow apparatus for heating and/or drying of particulate material is vertically disposed and is provided with an inlet at the top and an outlet at the bottom. The apparatus includes a flow passage for the particulate material which is defined between an outer housing and an inner housing. Each of the outer and inner housing defines perforated wall sections allowing for the flow of hot gas through the wall of one housing, into contact with the particulate material, and then out through the wall of the other housing. Manifolds are associated with the outer and inner housings to provide for uniform flow of the gas through the material. The perforated wall sections are positioned and designed to enhance particle-to-particle movement of the material to thereby avoid particle sticking and bridging problems.