Research On Reduction Roasting-magnetic Separation Process Of Silicon-magnesium Laterite Nickel Ore Under The Action Of Spent Cathode Carbo

Nickel is widely used in many fields because of its excellent physical and chemical properties.With the implementation of the ban on mining in Indonesia,the shortage of nickel resources in China is becoming more and more obvious.Therefore,the efficient use of low-grade laterite nickel ore in China has become the focus of follow-up research.A large amount of spent cathode carbon containing fluorine,cyanide and other toxic substances is produced in the aluminum electrolysis industry every year,but a large amount of spent cathode carbon cannot be effectively utilized.Because it contains 60%～70%carbon,it is a secondary resource with high utilization value,and there are few studies on the treatment of laterite nickel ore by spent cathode carbon in pyrometallurgical smelting.In this paper,the reduction characteristics of laterite nickel ore were studied by using Yunnan Yuanjiang laterite nickel ore with nickel content of0.82%as raw material,spent cathode carbon as reducing agent and CaO as additive.The conclusions are as follows:Through experiments and thermodynamic calculations,the feasibility of using spent cathode carbon as a reducing agent to reduce laterite nickel ore was verified.Due to the fluoride contained in the spent cathode carbon,the grade and recovery of nickel and iron in the reduced ferronickel concentrate increased significantly compared with anthracite.The effects of spent cathode carbon addition,reduction time,grinding time,reduction temperature and magnetic field strength on the grade and recovery of nickel and iron in ferronickel concentrate were studied by single factor test.The optimum experimental conditions were as follows:the addition of spent cathode carbon was 14%,the reduction temperature was 1250℃,the reduction time was 75 min,the grinding time was 12 min,and the magnetic field strength was 140 m T.The grade and recovery of nickel in ferronickel concentrate are 4.66%and 72.8%,respectively.The fluoride in the spent cathode carbon was fixed by adding CaO as a fluorine fixing agent.The F^-concentration in the leaching solution of roasted ore obtained during the reduction process was analyzed,and the effect of CaO addition on the fluorine fixation rate of spent cathode carbon and the toxicity of roasted ore was studied.XRD was used to analyze the roasted ore with or without CaO.It was found that the tremolite phase appeared in the roasted ore after adding CaO,indicating that the fluoride in the spent cathode carbon was transferred to the roasted ore in the form of Ca F₂.The optimum addition amount of CaO was 8%by single factor experiment.Under this condition,the fluorine fixation rate was 95.98%,and the average concentration of F-in the leaching solution was 31 mg·L^-1.The roasted ore and concentrate obtained under different CaO additions were analyzed by XRD,chemical analysis and SEM-EDS.The added CaO reacts with fluoride in spent cathode carbon to form Ca F₂,while some CaO reacts directly with olivine in laterite nickel ore to form pyroxene,which improves the reactivity of silicate minerals and promotes the reduction of iron and nickel oxides.The effects of different CaO additions on the grade and recovery of nickel and iron in ferronickel concentrate were studied.It is concluded that the optimum addition amount of CaO is 8%,the grade of nickel and iron in the concentrate is 5.59%and 69.28%respectively,and the recovery rate is 86.96% and 91.34% respectively.