China Nonferrous Metallurgy

In view of the high cost of iron powder in rare earth metallurgy and the low utilization rate of iron in NdFeB waste recovery process， this paper proposes a co-processing of rare earth concentrate with NdFeB waste sulfuric acid roasting-magnesium sulfate wastewater leaching. The purpose is to use the iron in NdFeB waste instead of iron powder in rare earth metallurgy process. The parameters of sulfuric acid roasting-magnesium sulfate wastewater leaching process were optimized by single factor test. Thermogravimetric analysis was carried out to further verify the reaction mechanism， and the following main conclusions were obtained. The optimal parameters of the co-processing are the acid-to-ore ratio of 1. 7∶1， the acidification time of 0. 5 h， and the 2 # roasting temperature curve. Under this condition， the decomposition rate of the roasted ore reaches more than 94. 0%， and the REO content in the discharged slag is less than 4. 0%. Thermogravimetric analysis shows that the roasting process is an endothermic reaction， and the heat absorbed by the reactants in the ideal state is about 589 kJ. When the temperature reaches 350℃， the decomposition activation energy of rare earth concentrate and NdFeB is greater than other side reactions， and the chemical reaction rate reaches a maximum of 1. 7 g/min. The verification test shows that the key indicators of the process， the content of REO in the discharge slag and the yield of REO， meet the requirements of the company's internal control， and the iron element in the waste is reused， which effectively reduces the discharge of solid waste and reduces the production cost. The results of this paper can provide reference for rare earth smelting enterprises and the treatment of NdFeB waste.