Power Development Co., Ltd.

煤燃烧排放的砷(As)、铅(Pb)、硒(Se)、铬(Cr)等重金属污染物已受到广泛关注。为探究超低排放燃煤机组烟气重金属的排放特征及分布规律，采用美国环境保护署(EPA) 29法和总颗粒物(TSP)采样系统对某350 MW超低排放机组(配置选择性催化还原(SCR)脱硝+低低温静电除尘(LLT-ESP)+湿法烟气脱硫(WFGD)+湿式静电除尘(WESP))不同点位烟气中气态和颗粒态重金属(As、Pb、Se、Cr)进行同步等速采样分析，考察了分形态重金属在燃煤电厂中的富集、迁移、分布、协同控制特性。结果表明：重金属(As、Pb、Se、Cr)在燃烧产物飞灰中的相对富集因子明显高于炉渣，飞灰/炉渣中不同重金属的富集程度与其挥发性具有较为明显的正/负相关关系；不同区域重金属质量平衡系数均在可接受范围内，燃煤过程中重金属(As、Pb、Se、Cr)主要分布在ESP飞灰和炉渣中，分别占总输出量的92.12%～95.33%和2.31%～6.70%，而在脱硫石膏和排放烟气中的合计占比仅为0.47%～2.98%；ESP、WFGD、WESP对4种重金属的脱除效率分别为98.70%～99.52%、13.03%～41.63%、23.67%～53.18%，ESP+WFGD+WESP组合对气态和颗粒态重金属的脱除效率分别为62.96%～92.99%和99.72%～99.96%，促进烟气中重金属向飞灰中富集和可溶性化合物中转化可成为燃煤电厂重金属污染物高效脱除的有效技术手段；排放到大气中的气态和颗粒态重金属(As、Pb、Se、Cr)质量浓度分别为0.11～1.89 、0.06～3.83 μg/m3，4种重金属的排放因子为0.15～1.72 g/TJ，不同分形态重金属排放的差异主要取决于其在煤中含量和挥发特性。

Heavy metals pollutants (As, Pb, Se and Cr) emitted from coal combustion has caused widespread concern. In order to study the emission and distribution characteristics of heavy metals from ultra-low emission coal-fired power plant, the Method 29 of the United States Environmental Protection Agency (EPA) and total suspended particulate (TSP) sampling system were used to conduct parallel isokinetic sampling analysis for the gaseous and particulate heavy metals at multiple points on a 350 MW coal-fired power unit equipped with selective catalytic reduction (SCR), low-temperature economizer-electrostatic precipitator (LLT-ESP), wet flue gas desulfurization (WFGD), and wet electrostatic precipitator (WESP). The enrichment, migration, distribution, and synergistic control characteristics of heavy metals in different forms in flue gas were investigated. The results show that the relative enrichment factors of four heavy metals (As, Pb, Se and Cr) in fly ash were obviously higher than that of bottom ash, in which the enrichment degree of different heavy metals in fly ash/bottom ash has positive/negative correlation with its volatility. The mass balance rates of four heavy metals across different zones were all in acceptable ranges. And four heavy metals (As, Pb, Se and Cr) were mainly distributed in fly ash and bottom ash during coal combustion with the ratios of 92.12%−95.33% and 2.31%−6.70%, respectively. However, a small amount of them existed in the WFGD and the stack, with sum in the range of 0.47%−2.98%. The ESP had high removal efficiency of 98.70%−99.52% for heavy metals. Both WFGD and WESP could further capture heavy metals, which resulted in the overall removal efficiencies of gaseous and particulate heavy metals across ESP+WFGD+WESP of 62.96%−92.99% and 99.72%−99.96%, respectively. Thus, the promotion on the enrichment of heavy metals into fly ash and the conversion of heavy metals into soluble compounds could be effective technical means for an efficient removal of heavy metals pollutants in coal-fired power plant. Finally, the concentrations of gaseous and particulate heavy metals (As, Pb, Se and Cr) emitted to atmosphere were extremely low with the range of 0.11−1.89 and 0.06−3.83 μg/m3, respectively, and the emission factors were 0.15−1.72 g/TJ, in which the emission differences of different heavy metals in different forms mainly depended on their contents in coal and volatility.

中国科协青年人才托举工程资助项目(2021QNRC001)

顾永正，魏书洲. 超低排放燃煤机组重金属协同减排和分布特性[J]. 煤炭学报，2023，48(8)：3252−3262.

GU Yongzheng，WEI Shuzhou. Synergistic emission reduction and distribution characteristics of heavy metals for ultra-low emission coal-fired power plants[J]. Journal of China Coal Society，2023，48(8)：3252−3262.