城市生活垃圾焚烧底灰熔融处理实验研究

Study on melting treatment of bottom ashes from municipal solid waste incinerator

应用XRF对不同粒径的焚烧底灰组成进行了分析,并对底灰试样(用TCLP)以1100～1400℃的熔融温度进行熔融处理实验、物理特性、微观形貌分析(用SEM)、熔渣重金属分布(用ICPAES)、浸出毒性测定等研究.研究结果表明焚烧底灰中主要组成为SiO2,CaO,Al2O3,Fe2O3;颗粒尺寸在10～190mm范围内的占797%;熔融试样的密度、吸水率和孔隙率均随熔融温度的升高而减小,减容比和硬度均随着熔融温度的升高而升高;在熔融温度高于1300℃时,试样达到较好的熔融效果;熔融体物相发生变化对重金属浸出率影响显著,挥发性重金属Cd和Pb以气态形式被收集,Zn,Cr,Ni则固溶在熔渣中,而Zn,Cr,Pb,Cu,Cd等重金属浸出率均明显降低.

The chemical composition of different particle-size bottom ashes was obtained by X-ray fluorescence (XRF). The physical changes of microstructure of melted bottom ashes samples were investigated by scanning electron microanalysis (SEM) at 1100 to 1400°C. The metals distribution within the slag was measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Leaching toxicity was performed by toxicity characteristics leaching procedure (TCLP). Experimental results indicate that the chemical compositions are mainly SiO2, CaO, Al2O3, and Fe2O3. The sizes of 79.7% particles range between 1.0 mm and 19.0 mm. With the elevation of the melting temperature, the density and water absorption of melted samples decrease, the porosity and hardness increase. Good melting effects are achieved when the temperature is above 1300°C. Leaching tests indicate that the changes of mineralogical phases have a remarkable impact on the heavy metal concentrations in leachate. After melting, the volatile heavy metals, like Cd and Pb, can be found in the gas collected, while Zn, Cr, and Ni are fixed into the melted slag, and the concentrations of heavy metals Zn, Cr, Pb, Cu, and Cd decrease distinctly.