调制碳酸钙对燃煤重金属As,Cd,Zn的排放控制

Controlling effect of the modified calcium carbonate on the capture of As,Cd and Zn during coal combustion

煤燃烧所造成的大气污染给人类健康带来了极大的危害,特别是亚微米飞灰颗粒中的重金属。以燃煤易挥发元素As,Cd,Zn为研究对象,试验煤样为松藻无烟煤。由煤中重金属的全量分析确定其基本特性,在此基础上,对燃煤添加剂碳酸钙进行调制改性,并设计正交试验研究了燃烧温度、金属盐种类和调制离子比对调制碳酸钙控制燃煤重金属As,Cd,Zn排放的影响。结果表明,最优的参数组合为燃烧温度1 000℃,金属盐种类为Al2(SO4)3,调制离子比(γ)为15,该条件下As,Cd,Zn的挥发率分别由82.67%,73.09%,82.50%依次降为26.13%,28.22%,18.81%。借助孔径分析仪、SEM及X射线能谱仪对调制前后碳酸钙的微观结构进行对比,发现其比表面积、孔径和孔隙率都有所提高,增加了钙离子利用率,从而提高了燃煤重金属的固化率,达到电厂燃煤经济与环境效益兼顾。

Air pollution caused by the coal combustion brings great harm on human health, especially the heavy metals (HMs) concentrated in the submicron particles. In the paper, the volatile elements in the raw coal sample (i.e. Songzao anthracite) including As, Cd, Zn were selected as research objects. The basic characteristics of the HMs in coal were studied using the total content analysis and X-ray diffraction in combination. Compared with the experimental results of CaCO3, the capture efficiencies of the modified CaCO3for As, Cd, Zn were studied. Based on the analysis of the orthogonal experiments, the factors affecting the capture efficacy of the HMs were analyzed. The optimal combination of the parameters follow as: the burning temperature of 1000 , the modifying agent of Al2(SO4)3and the modulation ratio of 15. The volatilization rates of As, Cd, Zn decrease from 82.67%, 73.09%, 82.50% to 26.13%, 28.22%, 18.81% respectively at the optimum conditions. ASAP2010 and SEM-energy spectrum scanning were used to explore the microstructures of CaCO3and the modified one, which reveales the significant increase of the surface area, the pore diameter and the porosity of the modified calcium carbonate. In conclusion, enhancing the use efficiency of the calcium during coal combustion can markedly increase heavy metals capture rate, which is beneficial to the achievement of the economic and ecological effects. © 2015, China Coal Society. All right reserved.