Patent ID: 6892471

Claim:
A material drying apparatus for continuous operation to substantially evaporate the liquid content of a sludge, the apparatus comprising: a first stage operating at ambient pressure for heating the sludge; a second stage operating with partial vacuum for receiving heated sludge from the first stage for further heating and for drying the sludge by evaporation of substantially all liquid therefrom to leave a dry particulate material; a cyclonic stage operating with a partial vacuum for applying sufficient centrifugal force to the dry particulate material to render this material benign; a cylindrical housing in the first stage defining a longitudinal axis, a hollow shaft coaxial with the housing and extending entirely through the housing, and conveyor paddles mounted on the hollow shaft and helically inclined relative to the axis to convey, upon rotation of the hollow shaft, sludge from an input end of the cylindrical housing to an outlet end thereof while being heated; and wherein the paddles are mounted on the hollow shaft by tubes the interiors of which are open to the interior of the hollow shaft whereby steam introduced into the hollow shaft will enter the tubes to provide a heat source for the sludge.