燃料煤重金属元素在飞灰及炉渣中的分布与富集研究

Study on distribution and enrichment of heavy metal elements in fly ash and slag from fuel coal

为研究燃料煤重金属元素在飞灰及炉渣中的分布与富集规律,采集了上海市火电厂、热电厂及化工企业燃煤锅炉的入炉煤、飞灰及炉渣样品,检测了样品中汞、砷、铬、镉、铅等重金属元素含量,研究了飞灰、炉渣中重金属含量与入炉煤中含量的关系,探讨了其分布机制。结果表明:飞灰中的汞含量比入炉煤中的提高了2~5倍,炉渣中汞含量较低,燃烧过程中煤中汞在飞灰中发生富集;飞灰中砷含量最高可达入炉煤中的10倍,燃烧过程中煤中砷在飞灰中具有明显的富集作用,炉渣与入炉煤中砷含量相当,说明入炉煤中的砷未在炉渣中富集;飞灰中铬含量最高可达入炉煤中的8倍,炉渣中铬含量高于飞灰中,燃烧过程中煤中铬元素在飞灰和炉渣中均有明显的富集作用;飞灰中镉含量最高可达入炉煤中的8倍,炉渣中镉含量可达入炉煤中的10倍以上;飞灰与炉渣中的铅含量显著高于入炉煤,铅在飞灰与炉渣中具有明显的富集作用。同时,测算了上海用煤企业入炉煤、飞灰及炉渣中重金属年产生量与比例,结果表明,汞、砷元素在煤燃烧后,分别有50.0%、61.7%富集到飞灰中,而在炉渣中的含量较低;铬、镉、铅元素在飞灰和炉渣中均有较大程度的富集,入炉煤中的铬、镉、铅元素主要随飞灰排出,随飞灰排出的铬、镉、铅元素分别占入炉煤中总量的76.7%、74.4%、75.1%。飞灰、炉渣是入炉煤中重金属排放的主要途径。

In order to study the distribution and enrichment of heavy metal elements in fly ash and slag from fuel coal,the coal,fly ash and slag samples from coal-fired boilers of thermal power plants,heat and power plants and chemical enterprises in Shanghai were collected. The mercury,arsenic,chromium,cadmium and lead content in the samples were tested. The study on the relationship between the content of heavy metals in the coal,fly ash and slag was carried out,and their distribution mechanism was discussed. The results show that mercury content in fly ash is 2 ~ 5 times higher than that in the coal. The mercury content in the slag is low. The mercury in coal is enriched in the fly ash during combustion. The arsenic content in the fly ash can reach about 10 times to that in the coal. Arsenic has a significant enrichment in fly ash during combustion. The arsenic content in slag is equivalent to that in coal,indicating that the arsenic has not been enriched in slag. The chromium content in fly ash can reach up to about 8 times of that in coal. The chromium content in the slag is higher than that in the fly ash. During the combustion process,the chromium element in the coal has a significant enrichment in both fly ash and slag. The cadmium content in fly ash can reach up to about 8 times to that in the coal,and the cadmium content in the slag can reach more than 10 times of that in the coal. The lead content in fly ash and slag is significantly higher than that in coal,indicating the obvious enrichment. In addition,the annual amount and proportion of heavy metals in coal,fly ash and slag from coal-fired enterprises in Shanghai were also calculated. The results show that there are 50.0% and 61.7% of the mercury and arsenic from the coal presented in the fly ash after combustion,respectively. There are obvious enrichments of mercury and arsenic in the fly ash,but rare distributions in the slag. The enrichments of chromium,cadmium and lead are observed in both fly ash and slag. The chromium,cadmium and lead in coal are mainly discharged with fly ash. There are 76.7%,74.4% and 75.1% of the chromium,cadmium and lead in coal discharged with fly ash,respectively. Fly ash and slag are the major ways to discharge heavy metals in the coal.