含铅渣(FeO/SiO_2=1.6,CaO/SiO_2=0.6)的挥发动力学分析

高温下含铅渣中易挥发组分的挥发对其物理化学性能测定的准确性和冶炼过程顺行都至关重要。为揭示FeO/SiO_2=1.6、CaO/SiO_2=0.6的PbO-FeO-CaO-SiO_2-ZnO含铅渣系的高温挥发特性及PbO含量变化对该体系铅渣挥发特性的影响规律,采用热重—差热分析,建立了不同PbO含量的含铅渣高温挥发动力学模型;并结合挥发后渣化学元素、XRD检测及热力学计算,揭示铅渣高温挥发规律。结果表明:高温下该铅渣体系剧烈失重主要是含铅物质挥发所致。该体系不同含铅量渣挥发趋势一致,在700～1 450℃高温段挥发最显著。含40%PbO渣的挥发率最高达33.59%,这与挥发后渣900～1 100℃水淬物相几乎检测不到Pb_2ZnSi_2O_7、Pb_2FeSi_2O_7含铅相是一致的;高铅渣挥发本征动力学分析可知,FeO/SiO_2=1.6、CaO/SiO_2=0.6的PbO-FeOCaO-SiO_2-ZnO系含铅渣的高温挥发机理函数符合Avrami-Erofeev方程,挥发过程受PbO随机成核和随后气泡生长控制,在实际冶炼过程中控制铅渣的形核长大过程可抑制高铅渣的挥发率。

Volatilization Kinetics Analysis of Lead-containing Slag with FeO/SiO_2=1.6 and CaO/SiO_2=0.6

The volatilization of volatile components in lead-containing slag at high temperature is very crucial for the determination of physicochemical properties and the smelting process. In order to reveal the effect law of high temperature volatilization characteristics of PbO-FeO-CaO-SiO 2-ZnO lead-containing slag system with quality ratio of FeO/SiO 2=1.6 and CaO/SiO 2=0.6,and PbO content on the volatilization characteristics of lead-containing slag,a high-temperature volatilization kinetics model of lead-containing slag was established by using DSC-TG technique with different PbO content. The volatile mechanism of lead-containing slag was uncovered through chemical composition analysis,X-ray diffraction (XRD) analysis,combined with the high-temperature volatilization kinetic mechanism and thermodynamics calculation. The results show that it is the volatilization of lead compounds at high temperature that causes severe weight loss of the lead-containing slag. The volatilization trend of different lead-containing slags in this system is consistent,and the volatilization is most significant in the high temperature of 700–1 450 ℃. The volatilization rate of slag containing 40% PbO is as high as 33.59%. Furthermore,lead-containing phase of Pb 2ZnSi 2O 7 ,Pb 2FeSi 2O 7 is almost undetectable in the volatile residue quenched at 900–1 100 ℃,which is consistent with the volatilization characteristics of the test slag. It can be seen that the high-temperature volatilization mechanism function of the lead-containing slag with quality ratio of FeO/SiO 2=1.6 and CaO/SiO 2=0.6 accords with Avrami-Erofeev equation,and the volatilization process is controlled by PbO random nucleation and subsequent growth of PbO bubbles. Therefore,in the practical smelting process of lead,the volatilization rate of high-lead slag could be suppressed by inhibiting the nucleation growth of the slag system.