除尘灰水洗对烟气颗粒物组成和二噁英的影响

Impact of water washing precipitator dust on the particulate composition and dioxins in sintering flue gas

为研究除尘灰配入烧结对烟气颗粒物组成和二噁英的影响,利用水洗方式对烧结除尘灰进行除杂改性,然后采用烧结杯测定改性前后配入对烧结矿性能的影响,并通过撞击式颗粒物采样器和二噁英采样器对烟气污染物进行采样分析,研究改性前后配入烧结对颗粒物组成碱金属和重金属含量以及烟气二噁英和前驱体物质排放量的影响.结果表明：烧结除尘灰中的K和Cl在水洗除杂改性过程中被有效去除,除杂后的除尘灰配加烧结有助于改善烧结矿粒度组成、减少烟气颗粒物和二噁英排放浓度;K组成在烧结颗粒物排放中占有较高比例,远高于金属Na、Pb和Zn的含量,且在粒度较细的细颗粒物中占比更高,水洗除杂后配入烧结可显著降低烧结配料中的K组成,使得烟气排放的K组成显著降低,进一步降低颗粒物的排放浓度,其中又以1.10~2.10μm粒度范围的颗粒物和K组成的减排比例最高;烧结原料Cl组成和烧结过程中的有机前驱体氯苯、多氯联苯是烟气二噁英生成的重要诱因,除尘灰水洗在降低Cl组成的同时也显著降低烟气前驱体多氯联苯排放量达40%,有利于降低烟气中二噁英的排放浓度.

Sintering is an important process for the smelting of iron and steel for ironmaking in a blast furnace. However,the sintering process emits air pollutants in the sintering flue gas,especially fine particles and dioxins. In order to study the effects of sintering with precipitator dust on the composition of particulate matter and dioxins in the sintering flue gas,the precipitator dust was purified by a water washing method. The influence of sintering with the precipitator dust before and after the purifying modification was determined by a sintering cup experiment. The flue gas pollutants were then collected by the impact particle sampler and dioxin sampler and the alkali content,heavy metal content and dioxin precursor emissions were determined. The experimental results indicate that potassium（K） and chlorine（Cl） in the precipitator dust are effectively removed by the water washing method. The sintering with the purifying modification and precipitator dust improve the particle size distribution of the sinter and reduce the concentration of particulates and dioxins that are emitted in the flue gas. The K content is higher in the sintered particles,especially the smaller ones,compared to sodium（Na）,lead（Pb）,and zinc（Zn）. Sintering with the precipitator dust after washing significantly reduces the K content of the sinter burden proportion and causes the notable reduction of K in the flue gas particles,particularly in the particle size range of 1. 10-2. 10 μm. The Cl in the sintering raw material,along with the chlorobenzene and polychlorinated biphenyls that are generated in thesintering process,cause the generation of the dioxins. The sintering with the precipitator dust after washing effectively reduces the content of Cl. The emission of polychlorinated biphenyls is also reduced to 40%,which is beneficial in reducing the concentration of dioxins.