温度与颗粒大小对污泥干燥特性的影响

4种不同质量等级的污泥颗粒在100～200 ℃下进行恒温干燥实验.结果表明,污泥干燥过程包括不稳定加热阶段、恒速干燥阶段、第一降速干燥阶段、第二降速干燥阶段4个阶段.在100～120 ℃时,污泥为弱强度干燥,临界含水质量分数受温度和颗粒大小影响不明显；在140～200℃时为高强度干燥,临界含水质量分数随温度升高或颗粒变大而增大.污泥干燥速率不仅取决于温度,还取决于污泥颗粒表面单位面积上实际用于蒸发水分的热量；减小污泥颗粒不仅可以增大比表面积,而且可以提高单位面积的干燥速率；而污泥的干燥时间与温度呈二次方关系,与污泥的表面积呈线性关系．

Effects of temperature and granule size on sludge drying characteristics

Four different weight grades of sludge granules were dried at constant temperature of 100～200 ℃. Results showed that sludge drying process included four periods: preheating period, constant rate drying period, the first falling rate drying period and the second falling rate drying period. Sludge drying process was a weak intensity drying process at 100～120 ℃, and critical moisture mass fraction was constant. It was a high intensity drying process at 140～200 ℃, and critical moisture mass fraction increased with the drying temperature or granule size increasing. The drying rate was affected with  drying temperature and the quantity of water evaporating heat in a unit surface area. Reduction of granule size can increase specific surface area and drying rate in a unit surface area. There were a quadratic nonlinear relationship between drying time and temperature, and a linear relationship between drying time and sludge surface area．