不同炉型燃煤电厂砷的行为特征及大气排放水平

BEHAVIOR AND ATMOSPHERIC EMISSION LEVELS OF ARSENIC IN COAL-FIRED POWER PLANTS WITH DIFFERENT BOILER TYPES

为了解贵州省燃煤电厂中砷元素(As)的行为特征及大气排放水平,采集了该省4座不同炉型燃煤电厂的输入和输出样品,分析了不同物料中的As含量,并结合不同物料的输入、输出信息。结果表明:4座电厂入炉煤的As含量为2.19~8.35 mg/kg,大部分电厂的入炉煤As含量低于全国平均值,入炉煤是电厂As的主要输入来源,占比达到93%~99%,石灰石贡献较小(<7%)。As在循环流化床锅炉与煤粉炉锅炉内的行为特征明显不同,循环流化床电厂的底灰和飞灰As含量相当,As表现出难挥发的特性,而煤粉炉在燃烧过程表现出As的易挥发性,飞灰As含量明显高于底灰。尽管输出模式有一定差异,2种锅炉的As输出途径主要为飞灰,其次为底灰和脱硫石膏,大气排放的比例较低,仅为0.01%~0.08%,且循环流化床锅炉的大气排放浓度和排放因子均明显低于煤粉炉。

In order to understand the behavior characteristics and atmospheric emission level of arsenic in coal-fired power plants in Guizhou Province,the input and output samples of four coal-fired power plants with different boiler types in Guizhou Province were collected,the arsenic content in different materials was analyzed.Combined with the input and output information of different materials,the following results were obtained.The arsenic content of feed coal in four power plants ranged from 2.19 mg/kg to 8.35 mg/kg,and the arsenic content of coal fired in most power plants was lower than the national average,feed coal is the main source of arsenic input in the power plant,accounting for 93%~99%,and the contribution of limestone is small(<7%).The behavior characteristics of arsenic in circulating fluidized bed boiler and pulverized coal boiler are obviously different.The arsenic content in bottom ash and fly ash of circulating fluidized bed power plant is similar,indicating arsenic is difficult to volatilize;while that in pulverized coal boiler is easy to volatilize,with the arsenic content in fly ash is significantly higher than that in bottom ash.Although there are some differences in the output modes,the arsenic output pathways of the two boilers are mainly fly ash,followed by bottom ash and desulfurization gypsum.The proportion of atmospheric emissions is low,only 0.01%-0.08%,and the atmospheric emission concentration and emission factor of circulating fluidized bed boilers are significantly lower than those of pulverized coal boilers.