Sludge drying in a paddle dryer (India)

This research is making use of a paddle dryer – a machine that consists of a trough with jacket and two drive shafts with hollow wedge-shaped paddles. Thermal shafts are made of pipes and are provided with hollow cuneiform paddles on shafts along its length. These paddles and the jacketed trough provide the required heat transfer surface. Thermal shafts are provided with the rotary joints at one end for steam entry and condensate removal. The revolving hollow paddles alternately and sectionally compress and expand the material, which offers high degree of agitation on heat transfer surface. This results in high heat transfer rates to the material to be dried. The materials along its path through the paddle dryer get dried. Wet sludge feed is fed to the sludge dryer at a controlled feed rate of 125 kg/hr. Dry saturated steam at pressure of 12 kg/cm² is considered as a heating media. The fine materials separated in the cyclone will be collected in a rotary valve located at the bottom of cyclone. The remaining fines carried along with the exhaust air is scrubbed in a dip type scrubber with the help of water. Saturated exhaust air from scrubber was vented to atmosphere. The technology has shown promising results in the removal of moisture in wet sludge resulting in a dry sludge powder.