烟气循环式燃煤耦合污泥焚烧系统中污泥燃烧及重金属迁移特性

Characteristics of combustion and heavy metal migration of sludge in a coal power plant coupled with sludge incineration system based on circulating flue gas

由于近年来污泥排放量增长迅速,对环境造成了严重污染,提高污泥的利用水平和无害化处理能力成为了研究热点,煤与污泥耦合燃烧是污泥减量化、无害化和资源化处理的有效手段之一。为此提出了一种基于烟气循环的燃煤耦合污泥焚烧系统,该系统中污泥通过单独的焚烧炉焚烧而非向煤粉炉内投加,同时采用煤粉炉高温烟气再循环促进污泥焚烧。采用管式炉、热重分析仪和X射线荧光光谱分析仪,研究了该系统中污泥燃烧特性及重金属迁移特性。分析了污泥含水率对燃烧特性的影响以及炉温、气体成分对重金属迁移特性的影响。结果表明,含水率的增加不利于污泥燃烧;炉温的增加有利于强挥发性重金属转化成气态从而降低残留率。升高O_(2)体积分数对不同重金属的残留率产生不同影响。CO_(2)体积分数升高会增加重金属的残留率,这是因为高体积分数的CO_(2)会降低燃烧温度,将重金属转变为稳定的金属氧化物并降低残留焦炭的孔隙率。相反,H_(2)O体积分数的升高会降低重金属的残留率,这是因为H_(2)O的存在提升了燃烧温度和焦炭的孔隙率。

Due to the rapid growth of sludge discharge in recent years and serious pollution to the environment,improving the utilization level and harmless treatment capacity of sludge has become a research hotspot.The coupling combustion of coal and sludge has become an effective measure on reduction,harmless and resource disposal of sludge.A coal power plant coupled with sludge incineration system based on circulating flue gas was proposed,sludge was incinerated in an incinerator instead of being added to the pulverized coal boiler,and the high-temperature circulating flue gas of the pulverized coal boiler was used to promote sludge incineration.The combustion characteristics and heavy metal migration characteristics of sludge in the system were studied by tube furnace,thermogravimetric analyzer and X-ray fluo⁃rescence spectrum analyzer.The effects of moisture content on combustion characteristics and the effects of furnace temperature and gas composition on the heavy metal migration characteristics of sludge were analyzed.The results show that the increase of moisture content brings negative effects on sludge combustion and the increase of furnace temperature is conducive to the conversion of strongly volatile heavy metals into gaseous state,thereby reducing the residual rate.The increase of O_(2) volume fraction brings different effects on the residu⁃al rate of different heavy metal.The increase of volume fraction of CO_(2) will increase the residual rate of heavy metal because high concen⁃tration of CO_(2) would decrease the combustion temperature,and the heavy metal is converted to stable metal oxides and decrease the porosi⁃ty of residual chars.On the contrary,the increase of H_(2)O volume fraction decreases the residual rate of heavy metal because the presence of H_(2)O improves the combustion temperature and porosity of chars.