污水污泥动态间壁热干燥特性及工艺

Process and mechanism of indirect thermal drying of sewage sludge

建立了序批式动态污泥间壁热干燥实验平台,并借此研究了干燥温度对干燥效率、干污泥热值、干污泥有机物含量(VS)、干燥冷凝水有机物含量(TOC)的影响;研究了水分蒸发速率与含水率的关系。结果表明:干燥温度低于160℃,水分蒸发速率较慢,干燥效率较低;干燥温度高于180℃,污泥絮体和微生物细胞发生破坏,水分存在形态发生改变,干燥效率提高较大,干污泥热值降低以及干燥冷凝水TOC浓度增加。干燥冷凝水属高浓度有机废水,须处理达标后才能排放。

Using an improved rotary indirect agitated drying laboratory rig operating with recirculation gas in a closed system, this study investigated the influence of drying temperature on drying efficiency, calorific heating value and volatile solid content （VS） of the dry solid and total organic carbon （TOC） content of the condensate. In the meantime, the relationship between water evaporation rate and water content was also investigated. Experimental results indicated that when the drying temperature was under 160℃, water evaporation rate was very low and about two hours were needed for water content decreasing from 80% to 60%. However, the water evaporation rate increased significantly when the temperature reached 180~C because hydrolysis and cytolysis of microorganism cells in sewage sludge occurred and the form of water existence was changed. The calorific heating value of dried solid decreased and the TOC of the condensate increased as a result. The condensate belonged to highly concentrated organic wastewater and must be treated before discharging to meet the effluent COD standard.