Effect Of Additives On The Carbothermic Reduction Of Nickel-slag To Extraction Iron

The nickel slag produced by smelting nickel in flash furnace has high iron content and contains nickel,chromium,cobalt,copper and other precious metal elements.It is an important secondary resource.Reasonable development and utilization can not only meet the requirements of comprehensive utilization of secondary resources,but also protect the environment and create certain economic benefits.In view of the difficulty in reducing iron in the form of ferroaluminate in nickel slag,calcium carbonate,sodium carbonate and calcium oxide are added to the slag to promote the carbothermal reduction of nickel slag.The effects of reduction temperature,reduction time and additive content on the recovery index of iron in reduction products were studied.The weight loss of the reduction process was determined by thermogravimetry,and the reduction degree of iron in the reduction product was calculated.The reduction experiments were carried out in a vertical reduction furnace,and the reduction products were analyzed chemically and separated magnetically to determine the metallization rate and recovery rate of iron in the reduction products.XRD and SEM-EDS were used to detect the phase composition and micro morphology of the reduction products.Through thermodynamic calculation and experimental verification,the mechanism of strengthening reduction by various additives was clarified,which can provide theoretical basis for resource utilization.N ickel slag,in order to achieve the effective recycling of nickel slag.The results show that:In the range of 1373 K-1473 K,the increase of the reduction temperature has a positive effect on the indicators of iron in nickel slag,and when the iron indicators of nickel slag reductio n product sittin gradually decreases to 1523 K.In addition,the reduction time has a catalytic effect on the reduction of nickel slag,and when the three products containing different additives continue to rise,and continue to keep warm to 60 times The indicators of iron in the nickel slag reduction product of CaO continued to rise,but the upward trend slowed significantly,the metalization rate curve of iron decreased slightly in the reduction product of the added Na₂CO₃,and the reduction and recovery rate curve of iron increased slightly.All three additives can increase the reduction reaction rate of ferrotise in nickel slag and reduce the temperature required for the reduction reaction of nickel slag.When the nickel slag does not contain additives,the initial temperature of the reduction reaction of fayalite is 987.90 K,and the initial temperature of the reduction of ferrotise olivine reduction reaction after CaCO₃,Na₂CO₃ and CaO is reduced to 648.64 K,904.64 K and 702.45 K,respectively.All three additives can improve the reduction and recovery index of iron in nickel slag to varying degrees.Under the condition of 1473 K insulation 45min,the reduction,metallization and recovery rate of iron in the reduced products of non-additive nickel slag were 58.17%,72.57%respectively.and 77.43%,while nickel slag added 6%CaCO₃ and increased to 85.03%,95.37%and 94.31%,and 6%Na₂CO₃ It was increased to 79.13%,92.56%and 91.73%,respectively,and 6%CaO was increased to 74.75%,93.27%and 92.39%,respectively.Among the three additives,the best is CaCO₃,followed by CaO,and finally Na₂CO₃.The use of additives to promote the carbothermal reduction of nickel slag is mainly achieved by the reaction of the additive with the fayalite in the nickel slag.Due to the strong attraction of Ca²⁺or Na²⁺with SiO₄^2-,the binding of SiO₄^2-to FeO in fayalite is weakened,making it easier to react with reducing agent carbon to generate metallic iron.