某硫酸渣中铅、锌的氯化焙烧动力学研究

Study on the Lead and Zinc Removal from Pyrite Cinder by Chloride Roasting and Its Kinetics

硫酸渣是一种大宗固体工业废弃物,铁含量较高,含量偏高的铅、锌往往是制约其作为铁资源利用的重要因素。氯化焙烧—磁化焙烧—磁选工艺则可成功脱除铅、锌,获得高铁低铅锌铁精矿。为揭示硫酸渣氯化焙烧过程中各主要相态的铅、锌发生氯化反应的限制环节,以及氯化反应的速率和氯化焙烧机理,以CaCl2为氯化剂,对某硫酸渣进行了氯化焙烧动力学研究。结果表明:①铁、铅、锌含量分别为49.90%、0.29%和1.23%,锌绝大部分为氧化态,铅主要为氧化态,其次是硫酸铅和其他形态铅,在CaCl2与硫酸渣的质量比为6%的情况下,延长氯化焙烧时间或提高焙烧温度,锌、铅的氯化挥发脱除率均上升,1 000℃时焙烧5 min,锌、铅的脱除率分别达86.99%和83.14%,为后续磁化焙烧—磁选制备高铁低杂铁精矿创造了良好的条件。②相比较而言,氯化焙烧脱锌比脱铅更容易。③900～1 050℃时锌氯化挥发的表观活化能为42.07×103J/mol,受化学反应控制;900～950℃时铅氯化挥发的表观活化能为43.88×103J/mol,受化学反应控制;1 000～1 050℃时铅氯化挥发的表观活化能为20.34×103J/mol,受扩散控制。④强化铅、锌的氯化挥发脱除,除了提高温度,还可通过增加固体氯化剂用量或提高硫酸渣固体颗粒的孔隙率和比表面积来实现。

Pyrite cinder is a large amount of solid industrial waste. The iron content is high,and high lead and zinc content often restrict its utilization as an important factor of iron resources. The process of chlorination roasting-magnetization roasting-magnetic separation can successfully remove lead and zinc and obtain high grade iron and low lead zinc content iron concentrate. The kinetics of chlorination roasting of pyrite cinder with CaCl2 as chlorinating agent was studied in order to reveal the limiting link of chlorination reaction of lead and zinc in the main phases in the process of chlorination roasting of pyrite cinder,the rate of chlorination reaction and the mechanism of chlorination roasting. The results showed that:① The contents of iron,lead and zinc were 49.90%,0.29% and 1.23% respectively. The majority of zinc was zinc oxide,and lead was mainly lead oxide,followed by lead sulfate and other forms of lead. When the mass ratio of CaCl2 to sulphuric acid residue was6%,the chlorination time or roasting temperature is prolonged,and the chlorination volatilization rate of zinc and lead increased. When roasted at 1 000 ℃ for 5 min,the zinc and lead removal rates were 86.99% and 83.14% respectively,which created good conditions for subsequent magnetization roasting and magnetic separation to prepare high grade iron and low impurity iron concentrate.② Comparatively speaking,it is easier to remove zinc by chlorination roasting than lead.③The apparent activation energy of zinc chlorination volatilization is 42.07×103 J/mol at 900~1 050 ℃,which is controlled by chemical reaction;the apparent activation energy of lead chlorination volatilization is 43.88×103 J/mol at 900~950 ℃,which is controlled by chemical reaction;and the apparent activation energy of lead chlorination volatilization is 20.34×103 J/mol at 1 000~1 050 ℃,which is controlled by diffusion.④To enhance the removal of chlorination volatilization of lead and zinc can be achieved not only by increasing the temperature,but also by increasing the amount of solid chlorinating agent or by increasing the porosity and specific surface area of solid particles of pyrite cinder.