Rämä Minna, Klemettinen Lassi, Rinne Marja, Taskinen Pekka, Michallik Radosław Markus, Salminen Justin, Jokilaakso Ari
School of Chemical Engineering, Department of Chemical and Metallurgical Engineering, Aalto University, 02150 Espoo, Finland.
Geological Survey of Finland, 02150 Espoo, Finland.
ACS Omega. 2023 Jun 5;8(24):21450-21463. doi: 10.1021/acsomega.3c00250. eCollection 2023 Jun 20.
The suitability of a non-fossil reductant in high-temperature treatment of a zinc leach residue was studied in laboratory-scale experiments. The pyrometallurgical experiments carried out at temperatures of 1200-1350 °C consisted of melting the residue under an oxidizing atmosphere to produce an intermediate, desulfurized slag, which was further cleaned of metals such as Zn, Pb, Cu, and Ag, using renewable biochar as a reductant. The aim was to recover valuable metals and produce a clean, stable slag for use as construction material, for example. The first experiments indicated that biochar is a viable alternative to fossil-based metallurgical coke. The capabilities of biochar as a reductant were studied in more detail after optimizing the processing temperature at 1300 °C and modifying the experimental arrangement by adding rapid quenching of the sample (to a solid state in less than 5 s) to the procedure. Modifying the slag viscosity by adding 5-10 wt % MgO was found to enhance the slag cleaning significantly. With an addition of 10 wt % MgO, the target Zn concentration in slag (Zn < 1 wt %) was reached after as little as 10 min of reduction, and the Pb concentration was also decreased relatively close to the target value (Pb < 0.03 wt %). With an addition of 0-5 wt % MgO, the target Zn and Pb levels were not reached within 10 min, but with longer treatment times of 30-60 min, 5 wt % of MgO was enough to decrease the Zn content in slag sufficiently. The lowest Pb concentration achieved with an addition of 5 wt % MgO was 0.09 wt % after a 60 min reduction time.
在实验室规模的实验中研究了非化石还原剂在锌浸出渣高温处理中的适用性。在1200 - 1350°C的温度下进行的火法冶金实验包括在氧化气氛下熔化残渣以产生中间脱硫渣，然后使用可再生生物炭作为还原剂进一步去除渣中的锌、铅、铜和银等金属。目的是回收有价金属并生产清洁、稳定的炉渣用作建筑材料等。初步实验表明生物炭是基于化石的冶金焦炭的可行替代品。在将处理温度优化至1300°C并通过在实验流程中增加对样品的快速淬火（在不到5秒内变为固态）来修改实验设置后，对生物炭作为还原剂的性能进行了更详细的研究。发现添加5 - 10 wt%的氧化镁来改变炉渣粘度可显著提高炉渣净化效果。添加10 wt%的氧化镁后，还原仅10分钟炉渣中的目标锌浓度（锌<1 wt%）就达到了，铅浓度也相对降低至接近目标值（铅<0.03 wt%）。添加0 - 5 wt%的氧化镁时，10分钟内未达到目标锌和铅水平，但处理时间延长至30 - 60分钟时，5 wt%的氧化镁足以充分降低炉渣中的锌含量。添加5 wt%的氧化镁在还原60分钟后达到的最低铅浓度为0.09 wt%。
