Characteristics of dehydrated sludge based on chemical modification: low temperature hot-air drying

doi:10.11949/j.issn.0438-1157.20171634

Abstract

Abstract:

In China, the sludge production is gradually increasing recently, while most of disposal processes require a reduction in the water content of sludge to a certain extent. Low-temperature drying with heat pumps is an economical and efficient sludge drying technology, which is also free from geographical restrictions. Owing to the unclear characteristics of sludge drying at low temperature, influences of temperature and particle size on sludge drying rate were studied by controlling these two variables separately in constant temperature and humidity chamber. And visualized relationships among drying rate and two factors were obtained by applying curve fitting method. Moreover, moisture release characteristics of iron-calcium-carbon-based conditioning sludge in low-temperature drying and traditional drying cases were comparatively explored by using a self-designed vertical sludge drying system. The results indicated that even at 60-80℃, drying rate still significantly accelerated with temperature increasing. A decreasing quadratic fitting polynomial satisfied the relation between drying time reduction and temperature increment. An incremental cubic fitting polynomial is awfully appropriate for the connection between drying time and sludge particle mass in the cases of various kinds of sludge. It is remarkable that iron-calciumcarbon-based conditioner can dramatically improve the sludge drying performance, because CaO and rice husk can increase the porosity and thermal conductivity of sludge, and the latter has a more obvious effect on low-temperature drying in the early stage.

Key words: sludge, heat pump drying, temperature, particle size, numerical analysis, iron-calcium-carbon-based conditioner, waste treatment

摘要：

我国每年污泥总产量逐渐增加，在其处理过程中普遍对含水率要求较高。采用热泵技术进行污泥低温干化，是一种既节能高效又不受地域限制的方法。但由于污泥的低温热干化特性尚不清楚，本文将通过在恒温恒湿箱中分别控制温度和污泥粒径两个单一变量，探究低温下二者对干化速率的影响，用曲线拟合得到直观的变化规律；并使用自主设计的立式污泥干化台架，对比探究铁-钙-碳基调理污泥在低温干化和传统干化下的水分释放特性。结果表明即使在60～80℃下，干化速率随温度升高仍然明显加快，干化时间缩短量与温度升高量满足递减的2次拟合多项式；而干化时间随污泥颗粒质量的变化满足递增的3次拟合多项式，所得拟合关系式适用于多种污泥；铁-钙-碳基调理剂可以显著提高污泥干化性能，稻壳和CaO会增加污泥孔隙和热导率，且稻壳在低温干化前期效果更明显。

关键词: 污泥, 热泵干燥, 温度, 粒径, 数值分析, 铁-钙-碳基调理剂, 废物处理

CLC Number:

LI Haiyan, LIU Huan, WANG Jiaxing, JIN Minghao, DENG Hongping, LU Geng, ZHANG Xiuju, YAO Hong. Characteristics of dehydrated sludge based on chemical modification: low temperature hot-air drying[J]. CIESC Journal, 2018, 69(7): 3257-3262.

李海燕, 刘欢, 汪家兴, 金明灏, 邓红苹, 卢更, 张秀菊, 姚洪. 基于化学改性的脱水污泥低温热风干化特性[J]. 化工学报, 2018, 69(7): 3257-3262.

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