燃煤电站砷、铅、镉、铬的迁移规律

发布时间：2017-12-27 13:16

本文关键词：燃煤电站砷、铅、镉、铬的迁移规律　出处：《华北电力大学》2015年硕士论文　论文类型：学位论文

【摘要】：燃煤电站是重金属污染的主要排放源之一,由于不同重金属的物理化学特性的差别,燃烧过程中重金属元素有些以气相形式排入大气,有些富集于飞灰和底渣中。砷、铅、镉、铬属于煤燃烧过程中易挥发的元素,燃煤电站先进的环保装置(SCR、 ESP、FGD)不能有效的捕获,任由重金属无控制的排放入自然环境中,会对环境产生巨大的危害。本论文选取四家典型燃煤电站,对燃烧过程中砷、铅、镉、铬四种重金属元素的分布、以及赋存形态进行了较为系统的研究。针对煤的复杂结构,重金属元素含量低,挥发性强等特点,本文采用先进的微波消解技术,建立了适用于批量检测且高效、准确分析各种原煤、飞灰、烟气等样品中砷、铅、镉、铬的测定方法,为深入研究重金属元素的迁移转化规律奠定了良好的基础。对三家典型燃煤电站燃烧过程中砷、铅、镉、铬四种重金属元素的分布、以及赋存形态进行了较为系统的研究。对煤燃烧产物飞灰、底渣,以及FGD过程中使用脱硫石灰石、脱硫石膏、废水进行了研究,并采用EPA方法29对2个燃煤电站ESP前后烟气、FGD后烟气排放特征进行分析。研究表明砷主要以飞灰形式释放,静电除尘器对砷有很强的捕获能力,FGD对砷也有一定的捕获能力,脱硫废水中砷的浓度不高,经处理后排放不会断环境造成影响,FGD后烟气中砷的含量很低；铅极大部分释放于飞灰中,在底渣中没有检测到铅；镉主要富集在飞灰和底渣中,约有30%存在于底渣中,70%存在于飞灰中,在ESP烟气中均没有检测到镉；铬主要富集在飞灰和底渣中,飞灰和底渣中铬的浓度近似相同,在除尘后烟气中只检测到微量的铬。对某燃煤电站飞灰进行筛分,探索砷在飞灰中的分布规律的因素。研究发现飞灰中砷含量随粒径增大显著下降,飞灰中砷的富集并不是由于飞灰中碳的物理吸附造成；砷在飞灰中的富集与飞灰中的钙、镁、铁含量的走势近似相同,推断飞灰中钙基物质的化学吸附是砷在飞灰中富集的原因。
[Abstract]:Coal fired power plant is one of the main sources of heavy metal pollution, due to the physical and chemical properties of different heavy metals, different heavy metal elements in the combustion process to form some gas into the atmosphere, some enriched in fly ash and slag in. Arsenic, lead, cadmium and chromium belong to volatile elements in coal combustion process. The advanced environmental protection devices (SCR, ESP and FGD) of coal-fired power plants can not be effectively captured. Allowing heavy metals to be discharged into the natural environment without any control will cause great harm to the environment. In this paper, four typical coal-fired power plants were selected, and the distribution and occurrence patterns of four heavy metals, including arsenic, lead, cadmium and chromium, were systematically studied. In view of the complex structure of coal, heavy metal content is low, and the characteristics of strong volatility, using advanced microwave digestion technology, set up suitable for batch testing and efficient and accurate analysis of various coal, fly ash, flue gas and other methods of determination of arsenic, lead, cadmium and chromium in the sample, and laid a good foundation for further migration study on the transformation of heavy metals. The distribution and occurrence of arsenic, lead, cadmium and chromium in the combustion process of three typical coal-fired power plants were systematically studied. For coal combustion fly ash, slag, and FGD in the process of using limestone and gypsum, desulfurization wastewater was studied by using EPA method, and 29 of the 2 coal-fired power plant flue gas before and after ESP and FGD characteristics of flue gas emission analysis. Research shows that the main arsenic in fly ash release, electrostatic precipitator has strong ability to capture the arsenic, FGD also has the ability to capture some of the arsenic concentration of arsenic in wastewater, desulfurization is not high, after treatment discharge will not break the environmental impact, the FGD content of arsenic in flue gas is very low; the great part of lead release in fly ash, slag not detected in the lead; cadmium mainly enriched in fly ash and bottom ash, about 30% in the bottom ash, 70% in fly ash, flue gas in the ESP were not detected cadmium; chromium mainly enriched in fly ash and slag, fly ash and bottom ash concentration chromium in approximately the same, after the dust in flue gas was only detected in trace amounts of chromium. The fly ash of a coal-fired power plant is screened and the factors of the distribution of arsenic in fly ash are explored. The study found that the arsenic content of fly ash increases with the particle size decreased significantly, and the enrichment of arsenic in fly ash is not caused by physical adsorption of carbon in fly ash; calcium, magnesium and iron content of arsenic in fly ash and fly ash concentration in the same trend, chemistry deduction of calcium based materials in fly ash the adsorption is arsenic enrichment in fly ash.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X773

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