污泥热干化和燃烧特性试验研究

分别在桨叶式干化机和热重仪上进行污泥干化和燃烧试验,研究了污泥干化特性和污染物排放特性,并对污泥的燃烧特性进行分析。结果表明,污泥干化过程分为黏稠区、粘滞区和颗粒区3个阶段。干化过程排放的污染气体有氨气、氯化氢、氟化氢、氰化氢、甲烷和挥发性有机酸等,其中氨气为主要污染气体。经冷凝吸收和活性炭吸附处理后,各种污染气体浓度均显著降低,其中氨气去除率最高,达97.04%。污泥干化冷凝液的BOD5和COD质量浓度分别为4 040、8 510mg/L,氨氮的质量浓度为1 025mg/L,pH为9.84,属于高浓度有机废水。污泥的燃烧过程可以分为3个失重阶段:水分析出阶段(50～150℃),挥发分燃烧阶段(150～450℃),固定碳燃烧阶段(450～650℃)。分别用Kissinger法和Ozawa法计算挥发分燃烧阶段和固定碳燃烧阶段的活化能和动力学方程,挥发分燃烧阶段的活化能低于固定碳燃烧阶段,表明挥发分燃烧阶段污泥更易燃烧。污泥的燃烧过程在650℃时基本完成,因此实际工程应用中,设计干化污泥的焚烧温度在750℃比较合理。

Experimental research on thermal drying and combustion characteristics of sludge

The drying process and emissions of sludge in the paddle dryer and the combustion characteristic in thermogravimetry is analyzed according to engineering practice.The drying process is divided into three stages,paste zone,sticky zone and particle phase.Emissions of drying process include polluting gases like ammonia,HCl,HF,HCN,CH4 and volatile organic acids;ammonia was the major polluting gas.Emission concentration of these polluting gas decreases after the condensation unit and adsorption device,and the removal rate of ammonia reach to 97.04%.Sludge drying condensate has higher organic content than that of the effluent standards,with BOD5 and COD concentration values of 4 040,8 510 mg/L,ammonia nitrogen of 1 025 mg/L,the pH of condensate was 9.84.Combustion process of sludge could divide into 3 parts of water volatilization stage(50-150 ℃),volatile combustion stage(150-450 ℃)and fixed carbon burning stage(450-650 ℃).The weight loss amount of volatile combustion stage is twice that of fixed carbon burning phase,and the activation energy of volatile stage is lower than that of fixed carbon phase according to Kissinger and Ozawa method,means the volatile combustion stage is much easier to get burn.Combustion process of sludge is basically completed at 650 ℃,so in the actual engineering application,the incineration temperature of sludge dryer should be designed at 750 ℃.