A New Route for Treating Neutral Leaching Residue

摘要

In the zinc smelter process, more specifically in the acid leaching step, sulfuric acid is added to the neutral leach residue until 45-60 g/L free acidity is reached, usually retrieving 92% of the zinc contained in the residue. However, it also makes iron and other impurities soluble. Because of that, the solution must go to some iron removal step (jarosite, for example). In this work, we compared this method to the sulfatation process. By simulating a roaster gas outlet (8% of SO2), at 650 °C, in a fiuidized bed reactor (2 kg/h), we were able to solubilize 96.6% of the zinc and only 2.9% of the iron. That means, no excess acid was required in order to obtain the zinc, and less acid was spent with iron (less residue was obtained as well because hematite occupies 67% less mass than jarosite). With these results, we may improve acid balance, residue reduction, and raw materials consumption in a zinc plant.