China Nonferrous Metallurgy

The spent cathode carbon is a large amount of solid waste produced in the industrial production process of aluminum electrolysis. At present, the main treatment method is stockpiling. The spent cathode carbon is mainly composed of carbon (60%~70%), and also contains some Na₃AlF₆, NaF, CaF₂ and NaCN. The cyanide and fluoride in the spent cathode carbon will cause serious harm to the environment and are hazardous wastes. At present, there are studies on the use of spent cathode carbon instead of carbonaceous reducing agent for ironmaking, and the related research on the reduction of laterite nickel ore has not been found. In this paper, Yunnan Yuanjiang laterite nickel ore was used as raw material, spent cathode carbon was used as reducing agent, and CaCO₃ was used as additive to study the reduction effect and fluorine fixation effect of spent cathode carbon reduction laterite nickel ore. The results show that under the optimum conditions of spent cathode carbon addition of 14%, reduction temperature of 1250℃, reduction time of 75min and CaCO₃ addition of 8%, the nickel and iron grades of the reduction roasting product are 5.82% and 66.23%, respectively, and the nickel recovery rate is 94.04%. The fluorine fixation rate was 94.9%, and the concentration of Fin the toxic leaching solution was 30mg·L-1, which was far less than the emission requirement of 100mg·L-1. Under the condition of reduction roasting, CN- in waste cathode carbon generates CO₂ and N₂, F- remains in the form of CaF₂ in the roasted ore, and can be used as a flux to reduce the melting point of ferronickel alloy, which is beneficial to the treatment of roasted ore in the later stage. This study provides a new idea for the harmless treatment of spent cathode carbon.