燃煤锅炉颗粒物粒径分布和痕量元素富集特性实验研究

EXPERIMENTAL STUDY ON CHARACTERISTICS OF PARTICULATE MATTER SIZE DISTRIBUTION AND TRACE ELEMENTS ENRICHMENT IN EMISSIONS FROM A PULVERIZED COAL-FIRED BOILER

文中用基于空气动力学直径分级的8级Andersen撞击器对煤粉锅炉排放的飞灰进行了现场采样,给出了电除尘器入口和出口的气溶胶颗粒物粒径分布.使用电感耦合等离子体发射光谱仪(ICP-AES),测定了不同粒径颗粒物上8种痕量元素As、Pb、Cr、Cd、Ni、Co、Cu、Zn的含量.结果表明,电除尘器入口烟气中飞灰粒径在0.7～17.5μm范围内呈单峰分布,峰值在7.48～10.97μm,而除尘器出口排放的颗粒物在1～10μm之间分布则比较平缓,PM2.5的质量份额明显增加.上述痕量元素在小粒径的飞灰上有明显的富集,同一粒径上的富集程度正相关于它们的挥发性,Cu、Cr、Co、Ni的相对富集倍数为4～6倍,挥发性最强的As的相对富集倍数接近30倍.此外,痕量元素的质量粒径频度分布在1～10μm有细微的双峰.

Fly-ash particles of emissions from a pulverized coal-fired boiler were sampled by Andersen 8-stage Stack Impactor with aerodynamic diameter separation. Size distribution of aerosol particles from ESP（electrostatic precipitator） inlet and ESP outlet was shown. Enrichment quantities of eight trace elements（As, Pb, Cr, Cd, Ni, Co, Cu, Zn） in different size particles were analyzed by inductively coupled plasma atomic emission spectrometry （ICP-AES）. The results show that there is a peak in range of 0.7～17.5μm in ESP inlet fly-ash particulates＇ size distribution and that the peak value locates at about 7.48～10.97μm. However, size distribution of ESP outlet fly-ash particulates is flat in range of 1～10μm, and mass percentage of PM2.5 increases. The smaller the diameter of fly-ash is, the higher the relative enrichment of these trace elements is. Enrichment quantities of these trace elements in the same size fine particles are positively correlative to their volatilities. The relative enrichment times of Cu, Cr, Co, Ni is 4～6 and it of As with more volatility is about 30. In addition, there are two peaks from 1μm to 10μm in mass size distributions of trace elements.