高铁锌焙砂还原焙烧-酸性浸出选择性分离铁锌研究

Splitting of zinc from iron in the high-iron zinc calcine by reducing the roast and acid leaching

传统湿法炼锌中的氧化焙烧阶段产生大量铁酸锌,在常规条件下铁酸锌难以溶出,不利于铁锌的分离和回收。铁酸锌的生成导致后续沉铁工序复杂,渣量大,既浪费了锌铁资源又污染环境。提出了一种新的还原焙烧方法,使高铁锌焙砂中的铁酸锌选择性分解为氧化锌和磁性氧化铁。以北京某锌冶炼厂的锌焙砂为研究对象,研究铁酸锌选择性分解为氧化锌和磁性氧化铁过程中的变化规律,寻找最佳还原焙烧条件。采用化学分析法和XRD检测技术研究了锌焙砂还原焙烧过程中焙烧温度、焙烧时间、CO体积分数和CO/CO2配比等因素对亚铁生成量、可溶锌率及锌浸出率的影响。结果表明,在750℃、CO体积分数为4%、CO/(CO+CO2)体积比为20%、焙烧60 min的焙烧条件,以及浸出酸度为150 g/L H2SO4、液固比为15∶1、转速为500 r/min、30℃的浸出条件下,锌的浸出率为93.24%,实现了铁锌的有效分离。

The present paper is engaged in a study of how to split Zinc from iron in the high-iron zinc calcine by reducing the roast and acid leaching. As is often the case,large amounts of zinc ferrite has been produced during the roasting stage by using the traditional hydrometallurgy method. Since zinc ferrite is insoluble in the mild conditions and difficult to be separated subsequently from each other,the residue of zinc ferrite used to be piled up is not only left over to threaten the surroundings but also result in the waste of valuable metal resources. It is starting from this need that we have proposed a selective reduction roasting process to transform ZnF e2O4 into ZnO and Fe3O4 under the atmosphere of CO,CO2 and N2at the temperature of 650-800 ℃ for 15-120 min. In doing so,we have managed to apply the high-iron zinc calcines we have obtained from a zinc plant in Beijing to our research work and made chemical analysis to detect the content of ferrous oxide and zinc oxide in the roasted calcines. In our work,we have analyzed XRD in the phase of transformation during the reduction roast,whose conditions include the roasting temperature,the duration time,the CO concentration and the CO /（ CO ＋CO2） ratio,all of which are of great significance for us to study for how to transform zinc ferrite into zinc oxide and magnetic iron selectively. And,then,acid leaching method has been used to separate zinc and iron subsequently. The results show that all the following factors, such as the roasting temperature, duration time,and roasting atmosphere may all exert strong impact on the decomposition of zinc ferrite. Under the optimal operation conditions（ roasting at the temperature of 750 ℃ for 60 min,with 4%CO concentration and CO /（ CO ＋ CO2） ratio at 20%; acid leaching at 30 ℃ with 150 g / L sulfuric acid,rotate speed at 500 r /min and liquid to solid ratio at 15： 1）,we have managed to make the zinc leaching rate as high as up to 93. 24%. Based on the above results,it can be concluded that it is possible to realize the reduction roasting and selectively separate zinc from iron,which proves to have a significant influence on the conservation of energy and resources in an environment-friendly way.