垃圾焚烧炉二恶英排放的控制策略及催化塔的记忆效应

Dioxin emission control of waste incinerator and memory effect of catalytic tower

针对某生活垃圾焚烧炉在稳定燃烧工况下,在燃后区及烟气净化系统不同点位采样并分析了烟气及飞灰中二恶英的排放浓度,分析全过程二恶英生成与控制机理,并针对催化塔的记忆效应进行了研究。结果表明:烟气中的不完全燃烧组分在过热器、省煤器发生异相催化合成反应,省煤器出口烟气中二恶英毒性当量质量浓度为1.227 ng·m^(-3),省煤器飞灰中二恶英毒性当量质量分数为0.756 ng·g^(-1),其中2,3,4,7,8-P5CDF对毒性当量贡献最大。焚烧炉布袋除尘器对烟气中二恶英具有较高的脱除效率,达到98.0%。SCR催化塔存在吸附型记忆效应,导致烟囱排放的二恶英质量浓度升高,通过系统吹扫后,催化塔恢复正常,对烟气二恶英催化降解效率达到64.7%。本研究通过对不同位点烟气及飞灰中二恶英的分析,以掌握二恶英在焚烧炉中的变化特征,可为垃圾焚烧烟气的控制与管理提供参考。

The formation and control mechanism of dioxins in the whole combustion process and the memory effect of the catalytic tower were studied by sampling and analyzing the emission concentration of dioxins in the flue gas and fly ash at different points in the post-combustion zone and the air pollution control system of a municipal solid waste incinerator under stable burning condition.The results showed that the incomplete combustion components in the flue gas had heterogeneous catalytic synthesis reactions in the superheater and economizer.The dioxin concentration in the flue gas and the fly ash at the outlet of the economizer reached 1.227 ng·m^(-3)and 0.756 ng·g^(-1),respectively.In addition,2,3,4,7,8-P5CDF contributed the most to the toxicity equivalent.The bag filter had a high removal efficiency of dioxins in the flue gas,which reached 98.0%.The SCR catalytic tower had an adsorption-type memory effect,which led to the increase of the mass concentration of dioxins emitted by the chimney.After the system purge,the catalytic tower returned to nomal,and the catalytic degradation efficiency of dioxins in the flue gas reached 64.7%.In this study,the variation characteristics of dioxins in incinerators were analyzed by the study of dioxins in flue gas and fly ash at different locations,which can provide reference for the control and management of waste incineration flue gas.