薄层微泡扩增污泥的高温和微波干燥特性研究

发布时间：2018-11-24 17:51

【摘要】：污泥中含有大量的重金属、病原菌和有机污染物,如果处理处置不当极易造成二次污染,危害生态安全和人类健康。城镇污水处理厂的脱水污泥含水率高、黏度大,水分难以进一步去除,成为污泥处理处置中的一大难题。污泥干燥技术因为能降低脱水污泥的含水率,减少其体积和质量,使其便于运输、填埋和焚烧等,成为了关注和研究的热点。研究污泥在新型干燥技术下的干燥特性,对开发高效低耗快速的污泥干燥技术,降低污泥干化的成本有重要意义。本课题将泡沫干燥法和泡沫辅助微波干燥法应用于脱水污泥的快速干化,对微泡扩增污泥的高温和微波干燥特性及其影响因素进行了研究,以期能为脱水污泥提供一种新的快速干燥方法。在脱水污泥中加入氧化钙后,污泥内部变为碱性环境,微生物的细胞壁被破坏,大量胞内生物表面活性剂溶于污泥中,使得污泥的表面张力降低,通过搅拌可以形成微泡扩增污泥。在搅拌速度为(62±5)r/min,搅拌时间为20min,微泡扩增污泥的密度为0.78g/m L时,污泥的高温干燥获得最好的干燥效果。污泥微泡扩增后持水性能改变,自由水含量增多,干燥过程中污泥内部的气泡破裂形成的孔隙加快了内部水分向外迁移的速度,微泡扩增后污泥与空气的接触面积增大,是微泡扩增污泥干燥速率加快的原因。微泡扩增污泥的微波干燥过程在变频微波炉中进行,考察了辐射时间、微波输出功率和污泥厚度对微泡扩增污泥干燥过程的影响。厚度为2mm、4mm和8mm的薄层微泡扩增污泥,在不同的真实输出功率条件下的干燥特性相似。微泡扩增过程和微波辐射都会使污泥的毛细水、吸附水、结合水释放为自由水,使恒速干燥阶段在干燥过程中所占的比例较大。通过Origin8数据处理软件对实验数据的模拟,发现薄层干燥的Page模型与微泡扩增污泥微波干燥过程的相关性系数R2最大,同时方差χ2和剩余误差总和SR最小,可以用于微波干燥过程中干基含湿量的预测。在微泡扩增污泥的高温干燥过程中,Logistic模型的拟合效果最好。
[Abstract]:Sludge contains a large number of heavy metals, pathogens and organic pollutants, if the treatment is not disposed of easily cause secondary pollution, harm to ecological security and human health. The high moisture content and high viscosity of dewatered sludge in urban sewage treatment plants make it difficult to remove water further, which has become a difficult problem in sludge treatment and disposal. Sludge drying technology, which can reduce the moisture content of dewatered sludge, reduce its volume and quality, and make it easy to transport, landfill and incineration, has become the focus of attention and research. It is of great significance to study the drying characteristics of sludge under the new drying technology in order to develop efficient and fast sludge drying technology and reduce the cost of sludge drying. In this paper, foam drying method and foam assisted microwave drying method were applied to the rapid drying of dewatered sludge. The characteristics of high temperature and microwave drying of microbubble expanded sludge and its influencing factors were studied. In order to provide a new rapid drying method for dewatering sludge. When calcium oxide is added to the dewatered sludge, the sludge becomes alkaline, the cell wall of the microorganism is destroyed, and a large number of intracellular biosurfactants dissolve in the sludge, which reduces the surface tension of the sludge. Microbubbles can be formed by stirring to amplify sludge. When the stirring speed was (62 卤5) r / min, the stirring time was 20 min and the density of microbubble expanded sludge was 0.78g/m L, the best drying effect was obtained when the sludge was dried at high temperature. The water holding capacity changed and the free water content increased after the sludge microbubble amplification. During the drying process, the pore formed by the bubble burst in the sludge accelerated the internal water migration, and the contact area between the sludge and the air increased after the microbubble amplification. It is the reason that the drying rate of microbubble expanded sludge is accelerated. The microwave drying process of microbubble expanded sludge was carried out in a frequency conversion microwave oven. The effects of radiation time microwave output power and sludge thickness on the drying process of microbubble expanded sludge were investigated. The drying characteristics of thin layer microbubble expanded sludge with thickness of 2 mm and 4 mm and 8mm were similar under different real output power conditions. Both microbubble amplification process and microwave radiation can make the sludge capillary water, adsorbed water, combined with water release into free water, so that the drying stage of constant speed in the drying process accounted for a large proportion. Through the simulation of experimental data by Origin8 data processing software, it was found that the correlation coefficient R2 of thin-layer drying Page model and microbubble sludge microwave drying process was the largest, and the variance 蠂 2 and the sum of residual error SR were the smallest. It can be used to predict the moisture content of dry base during microwave drying. In the high temperature drying process of microbubble expanded sludge, the fitting effect of Logistic model was the best.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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