TECHNO-COMMERCIAL FEASIBILITY OF SLUDGE DRYING USING SCREW CONVEYOR DRYER

摘要

Thermal drying of sludge is gaining popularity to reduce the numerous problems associated with its handling and disposal.Despite being many types of dryers available for sludge drying,market demands innovative drying technologies that can be cost-effective as well.With this in mind a novel Screw Conveyor Dryer has been designed for the drying of viscous industrial sludge with moisture content as high as 85 wt ％.Screw conveyor dryer consist of a jacketed cylinder which houses hollow shaft and piping arrangement to transport the drying medium from jacket and hollow shaft into the main dryer body.The dryer can utilize both modes of heat transfer,i.e.conductive and convective modes of heat transfer thus making design thermally more efficient.An arrangement of radial mixers and lifters on screw shaft at regular intervals minimizes the agglomeration of sludge.This extremely important feature increases agitation and heat transfer to deal with stickiness of sludge.A procedure for the design of Screw Conveyor Dryer is given with an example for drying of 100 kg/hr sludge using different heating media such as flue gas and condensing steam.Thermal drying of sludge is a very energy intensive process and hence it need to be justified economically.Hence an attempt has been made to work out the economics of sludge drying for Indian scenario.It can be concluded from the results obtained through calculations that sludge drying using novel Screw conveyor Dryer is technically as well as commercially feasible.