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J4  2009, Vol. 43 Issue (09): 1661-1667    DOI: 10.3785/j.issn.1008-973X.2009.
    
Effects of temperature and granule size on sludge drying characteristics
 MA Hua-Wen, WENG Huan-Xin
(Institute of Environment and Biogeochemistry, Zhejiang University, Hangzhou 310027, China)
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Abstract  

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.



CLC:  X 705  
Cite this article:

MA Hua-Wen, WENG Huan-Xin. Effects of temperature and granule size on sludge drying characteristics. J4, 2009, 43(09): 1661-1667.

URL:

http://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2009.     OR     http://www.zjujournals.com/eng/Y2009/V43/I09/1661


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.

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