垃圾焚烧过程中二噁英低温热处理及紫外光解试验研究

【作者】 黄蕾；

【导师】 岑可法； 李晓东；

【作者基本信息】 浙江大学 ， 工程热物理， 2005， 硕士

【摘要】 城市生活垃圾焚烧技术在我国逐步兴起,如何控制垃圾焚烧过程中产生的二恶英污染问题,已经成为当今环境污染研究的热点。本文主要对垃圾焚烧过程飞灰中的二噁英分布特性、二噁英前驱物生成机理、飞灰中二噁英的低温热处理控制技术、以及烟气中前驱物生成的二噁英的紫外光解控制技术展开研究,为今后垃圾焚烧过程中二噁英控制技术奠定基础。 固态五氯酚作为前驱物,测定了五氯酚中所含的二噁英含量,研究了五氯酚在飞灰表面上低温催化反应生成物中二噁英的分布特性,并对影响二噁英生成的因素进行了分析。 研究了五氯酚生成烟气中二噁英的光化学降解机理。采用中压汞灯对烟气直接光照,进行光降解试验,结果表明烟气中高氯代PCDD/Fs可以在一定条件下接受通过紫外光的照射,发生光致氧化到光致降解的一系列复杂的脱氯、降解及生成反应,形成多种低氯代同系物。降解率最高可达99.5%,I-TEQ值的脱除率可达88%。烟气中通入臭氧气体能催化二噁英光解。臭氧光催化氧化分解二噁英主要是在于产生了具有强氧化能力的羟基基团,由于羟基基团的攻击使二噁英发生亲电子加成反应最终使二噁英得到分解。 对飞灰热处理试验结果证实在缺氧条件下,飞灰中的二噁英通过脱氯/加氢反应得以降解,降解率在42%—100%之间;确定了最经济有效的低温脱除飞灰中二噁英的试验条件是:氮气气氛下,温度在400℃,加热60min。 文中还对下一步二噁英的控制技术研究工作提出了设想。更多还原

【Abstract】 Municipal solid waste （MSW） Incineration technology has been a rising technology in China gradually. Controlling technologies of dioxins in MSW incinerator have been pop topics in environmental pollution research all over the world. This study gives synthesis mechanism of precursors, low temperature thermal-treatment of fly ash produced from MSW incinerator, and Ultra-violet photolysis of dioxins in flue gas produced from heating PCP, which are the foundation of controlling technologies of dioxins from MSW incineration for the future.Model studies were performed to determine the content and homologue profile of dioxins which produced from PCP as precursor of PCDD/Fs. The effects have been discussed. The pathways of dioxins formation were found.The photochemical decomposition of PCDD/Fs was investigated in flue gas produced from PCP. Photodegradation experiments were performed in the gaseous phase by direct irradiation with medium pressure mercury lamps. The dechloration, degradation and synthesis of the dioxins occurred under different conditions. A maximum degradation rate was about 99.5%, and maximun reduction rate of I-TEQ was about 88%. The addition of O₃ catalyzed photolysis of dioxins. O3 produced OH radical which has powerful oxidable ability. Dioxins were attacked by OH radical initially and then occurred electrophilic addition reaction. As a result, dioxins were decomposed by photocatalytic degradation. The photolysis rate of dioxins in solutions were higher than those in fule gas.The thermal treatment of fly ash from waste incinerator in low temperature showed that under oxygen deficient conditions a dechlorination/hydrogenation reaction was observed. The degradation rates were from 42% to 100%. The optimum condition was in nitrogen atmosphere, 400℃, and two hours.Some suggestions were proposed for the farther research of controlling technologies of dioxins in the end of this paper.更多还原