污泥低温干燥动力学特性及干燥参数优化  被引量:18

Drying kinetics and parameters optimization of sludge drying at low temperature

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作  者:张绪坤 刘胜平 吴青荣 曾恩 王高敏 Zhang Xukun Liu Shengping Wu Qingrong Zeng En Wang Gaomin(Mechanical and Electrical Equipment Institute of Nanchang Hangkong University, Nanchang 330063, Chin)

机构地区:[1]南昌航空大学机电设备研究所,南昌330063

出  处:《农业工程学报》2017年第17期216-223,共8页Transactions of the Chinese Society of Agricultural Engineering

基  金:江西省科技计划(重大)资助项目(2015ACG70012);国家自然科学基金资助项目(51168038)

摘  要:为了研究污泥的低温干燥动力学特性,以薄层污泥为研究对象进行了低温干燥试验,探讨了温度、薄层厚度以及风速对污泥水分比和干燥速率的影响,并对低温干燥参数进行了优化。结果表明:污泥低温干燥过程主要由升速和降速段组成,其中降速阶段存在第一、第二降速阶段;不同低温干燥条件下的第二临界含水率变化不大,大致在0.5 g/g(干基)附近。使用决定系数R2、卡方χ2及均方根误差RMSE对6种常用干燥模型进行评价,结果表明Midilli模型的平均R2最大、平均χ2及RMSE最小,分别为0.999 8、2.46×10-5、0.004 2,是描述污泥低温热风干燥的最优模型。根据Fick第二定律和Arrhenius方程,得到5、10和15 mm厚度污泥在50~90℃热风干燥的水分有效扩散系数和活化能。正交试验得到相对单位能耗最优干燥工艺为:温度90℃、风速0.8 m/s、厚度10 mm,平均干燥强度最优工艺为干燥温度90℃、风速0.8 m/s、厚度5 mm。试验结果可为后续研究污泥热泵干燥及太阳能-热泵联合干燥提供参考。The production of sewage sludge in China is increasing daily. Such a large amount of sewage sludge has a tremendous pressure on environment. The moisture content of sewage sludge is greatly high. Decreasing the moisture content of sludge is a critical step in harmlessness, bulkiness reduction, and resource utilization. Thermal drying has been proven to be an effective method to reduce solid volumes. The traditional sludge drying is often carried out by drum dryer, rotary dryer, fluidized dryer, and so on. The drying temperature is set higher (above 100 ℃, resulting in high energy consumption and producing secondary pollution. However, sludge drying at low temperature can not only save energy, but also reduce the emissions of malodorous gases and have a safer drying process. In order to study the drying kinetics of sludge drying at low temperature, the effects of drying temperature, thin-layer thickness and air speed on sludge moisture ratio and drying rate were examined. The optimization of the low temperature drying parameters was also studied. The results showed that the drying rate and drying time were influenced significantly by drying temperature, thickness and air speed. The low temperature drying process could be mainly divided into 2 periods: the acceleration period and falling rate period. The falling rate period could be also divided into 2 periods: the first falling rate period and the second falling rate period. The critical water contents under different drying conditions were about 0.5 g/g (dry basis) between the first falling rate period and the second falling rate period. According to statistical parameters, i.e. coefficient of determination (R2), chi-square (2,2), and root mean square error (RMSE), the Midilli model was the most suitable to describe the relationship between sewage sludge moisture and drying time among 6 common thin-layer drying models. The effective diffusion coefficients of sludge having thicknesses of 5, 10, and 15 mm were 8.72 × 10^-10-3.61 × 10^9, 1.

关 键 词:干燥 模型 优化 污泥 低温 干燥动力学 

分 类 号:X705[环境科学与工程—环境工程]

 

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