| Three different weight grades of sludge granules(2.5, 5, 10 g) were dried at constant temperature of 100，200，300，400 and 500℃, respectively. Then characteristics of weight loss and change of apparent form during sludge drying were analyzed. Results showed that there were three stages during sludge drying at 100-200℃: acceleration phase, constant-rate phase, and falling-rate phase. At 300-500℃, there were no constant-rate phase, but due to lots of cracks generated at sludge surface, average drying rates were still high. There was a quadratic nonlinear relationship between average drying rate and drying temperature. At 100-200℃, drying processes of different weight grade sludge granules were similar. At 300-500℃, drying processes of same weight grade of sludge granules were similar. Little organic matter decomposed till sludge burning at 100-300℃, while some organic matter began to decompose at the beginning of sludge drying at 400-500℃. |
