Abstract:

The emission of trace elements in coal-fired power plant has caused widespread concern in the world. The experimental study on the distribution and co-removal through air pollutant control devices (APCDs) and emission of trace elements (Cr, Mn, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, Pb) was conducted on a 320 MW coal-fired power plant equipped with selective catalytic reduction (SCR), electrostatic precipitator (ESP) and wet desulfurization unit (WFGD) in this study. US EPA Method 29 was used for the sampling of trace elements in flue gas. The results showed that mass balance rate of trace elements across the boiler, SCR, ESP, WFGD and the whole system was in an acceptable range. The trace elements were mainly distributed in bottom ash and fly ash with the proportion of 1.90%-27.6% and 72.3%-98.0% accounting for the sum of trace elements in bottom ash, ESP ash, stack and that removed by WFGD, respectively. The trace elements in stack and removed by WFGD accounted for little with sum in the range of 0.11%-0.66%. Co-removal rate of trace elements in flue gas across ESP and WFGD was 99.39%-99.95% and 40.39%-78.98%, respectively. The overall removal rate through SCR + ESP + WFGD was 99.79%-99.99%. The great removal rate across ESP was the main reason for high synergistic removal efficiency of APCDs. The concentration of trace elements in the stack is 0.01-12.88 μg·m^-3, while the emission factor is (0.002-4.57)×10^-12 g·J^-1. More studies on the emission of trace elements in coal-fired power plant should be carried out, which was beneficial for the establishment of emission models of trace elements in China's coal-fired power plants and the development of relevant standards.

Key words: coal combustion, trace elements, distributions, co-removal, emission, environment

摘要：

燃煤电厂痕量元素的排放已经引起了世界的广泛关注。在一台配置选择性催化还原（SCR）+静电除尘器（ESP）+湿法脱硫装置（WFGD）的320MW燃煤电厂上进行了12种痕量元素（Cr、Mn、Co、Ni、Cu、Zn、As、Mo、Cd、Sb、Ba、Pb）排放特性的实验研究，使用了US EPA Method 29对4个测点烟气痕量元素进行同时取样，考察了痕量元素在电厂中的分布、协同脱除以及在烟囱中的排放。结果表明：锅炉、SCR、ESP、WFGD和整个系统的痕量元素质量平衡率均在可接受的范围内。这12种痕量元素主要分布在底渣和飞灰中，分别占据底渣、ESP灰、WFGD脱除及烟囱排放痕量元素总量的1.90%～27.6%和72.3%～98.0%，然而，它们在烟囱和被WFGD脱除的部分所占比例较少，两者之和仅占0.11%～0.66%。ESP和WFGD对烟气痕量元素的脱除率分别为99.39%～99.95%和40.39%～78.98%，SCR+ESP+WFGD对烟气痕量元素的总体脱除率为99.79%～99.99%。ESP对痕量元素较高的脱除效率是APCDs系统具有较高的协同脱除效率的主要原因。烟囱排放的痕量元素浓度及排放因子分别为0.01～12.88 μg·m^-3和（0.002～4.57）×10^-12 g·J^-1。应进行更多的燃煤电厂痕量元素排放的研究，以便为中国燃煤电厂痕量元素的排放预测模型的建立以及相关标准的制定提供参考。

关键词: 煤燃烧, 痕量元素, 分布, 协同脱除, 排放, 环境