Using an improved rotary indirect agitated drying laboratory rig operating with recirculation gas in a closed system

this study investigated the influence of drying temperature on drying efficiency

calorific heating value and volatile solid content(VS) of the dry solid and total organic carbon (TOC) content of the condensate.In the meantime

the relationship between water evaporation rate and water content was also investigated.Experimental results indicated that when the drying temperature was under 160℃

water evaporation rate was very low and about two hours were needed for water content decreasing from 80% to 60%.However

the water evaporation rate increased significantly when the temperature reached 180℃ because hydrolysis and cytolysis of microorganism cells in sewage sludge occurred and the form of water existence was changed.The calorific heating value of dried solid decreased and the TOC of the condensate increased as a result.The condensate belonged to highly concentrated organic wastewater and must be treated before discharging to meet the effluent COD standard.