加速碳酸化技术对城市垃圾焚烧飞灰重金属稳定性影响研究

对南方某城市生活垃圾焚烧厂新鲜焚烧飞灰对CO₂的吸收及其碳酸化的过程进行了研究,实验从水分添加量、CO₂的分压等因素,考察了飞灰中重金属Pb的稳定化效果,并利用X射线衍射实验(XRD)、扫描电镜实验(SEM)对反应机理进行了分析.结果表明,不添加水分时,焚烧飞灰对CO₂的吸收效果较差;当水分添加量大于10％时,焚烧飞灰对CO₂的吸收效果较好.焚烧飞灰对纯CO₂的吸收效果较好,空气中的CO₂含量较低,在反应1 d后吸收效果不是十分明显.XRD实验结果表明,CO₂的吸收会使焚烧飞灰中大量的Ca(OH)₂与CO₂反应转化为CaCO₃,从而降低焚烧飞灰的碱性;部分重金属的氧化物会被碳酸化成生相应的碳酸盐.SEM实验结果表明,经过碳酸化处理后的飞灰颗粒表面生成了片状和圆柱状的晶体物质.

Investigation of the Sequestration of CO2 and Carbonation Process for the Stabilization of MSW Fly Ash

The sequestration of CO₂ and carbonation process for the stabilization of fresh fly ash from municipal solid waste (MSW) incinerator were investigated. The purpose of this paper is to evaluate the influence of fundamental parameters affecting the stabilization of heavy metal of Pb and diffusivity and reactivity of CO₂ (i.e. the water content and concentration of CO₂). In addition, the major physical and chemical changes in fly ash after carbonation were investigated using XRD and SEM. It shows that 10% or more water content added to fly ash could remarkably accelerate the sequestration of CO₂, compared with control samples without water. The sequestration of CO₂ is not remarkable within 1 day in the air atmosphere for low content of CO₂ (0.03%). The XRD analysis indicates that CO₂ could combine Ca(OH)₂ to form CaCO₃ and CO₂ could also combine heavy metal oxides to form heavy metal carbonate(i.e. from Pb₃O₄ to PbCO₃). Aggregates of crystals of sheet and cylinder can be observed by SEM.