Drying characteristics of deep dewatered sludge

doi:10.11949/j.issn.0438-1157.20170069

Abstract

Abstract:

Composite conditioners in deep-dewatered sludge have an important influence on its drying characteristics. In order to obtain deep-dewatered sludge, the raw sludge was pretreated by four kinds of typical composite conditioners and then dewatered. At the N₂ atmosphere and 473 K, the effects of the composite conditioners on the emission characteristics of moisture and pollutants, as well as the drying products properties of gas, liquid and solid phase, were investigated. The results showed that the composite conditioner could effectively reduce the water content of dewatered sludge and accelerate the water release, shorting the drying time as well. Conditioning process in the acid, alkali and strong oxidizing environment destroyed the organic structure of sludge so that the aromatic-or thiophene-S in sludge could transfer into more stable sulfonic acid-or sulfone-S. Also, the alkaline environment allowed the dissolved acidic sulfur-containing gas to be fixed, thereby reducing the amount of sulfur-containing gas released during drying. But the releasing rate of ammonia was accelerated. Because of the high concentration of sulfur-containing gases, nitrogen-containing gases and volatile organic compounds in the drying exhaust gas, the condensate had a high pH and COD accompanied by malodor, and thus needed to be disposed before it can be discharged. The lower heating value of sludge can be 6.79—13.18 kJ·g^-1 of dry sludge and efficiently maintained under the drying temperature of 473 K so that the dried sludge can provide a kind of renewable energy.

Key words: sewage sludge, deep dewatering, drying, polluting gas, condensate, heating value

摘要：

深度脱水污泥中调理剂对其干化特性有着重要影响。实验采用4种典型复合调理剂对污泥进行预处理，制得脱水污泥，在N₂气氛、473 K条件下，探究调理剂对污泥干化过程中水分和污染物释放以及干化气、液、固产物特性的影响。结果表明，所用复合调理剂均可以有效降低脱水污泥含水率，加快干化阶段水分释放速率；调理过程中的酸碱及强氧化环境能破坏污泥中的有机结构，使污泥中的芳香族或噻吩S转化为更加稳定的磺酸或砜类S，且调理后的碱性环境让溶解的酸性含硫气体固定，从而使得干化时含硫气体释放量减少，但会加速氨气的释放。干化时复杂的气相产物溶解于冷凝液使其具有较高的pH以及COD并伴有恶臭，需进行进一步处理；污泥热干化后样品热值降低量在3.63%以内，不影响其能源化利用。

关键词: 污泥, 深度脱水, 干化, 污染性气体, 冷凝液, 热值

CLC Number:

WANG Jiaxing, LIU Huan, LIU Peng, ZHANG Qiang, LU Geng, HU Hongyun, YAO Hong. Drying characteristics of deep dewatered sludge[J]. CIESC Journal, 2017, 68(6): 2491-2500.

汪家兴, 刘欢, 刘鹏, 张强, 卢更, 胡红云, 姚洪. 深度脱水污泥的热干化特性[J]. 化工学报, 2017, 68(6): 2491-2500.

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