Otimização do processo de pelotização visando o incremento da resistência mecânica das pelotas

Abstract

The excessive fine particles in the calcined ore is one of the main aspects that limit the increase of production, result in energy inefficiency and instabilities in the processes. The pelletizing plant is responsible for treating, in closed circuit, the dust generated in electric furnaces and rotary kilns, guaranteeing the metallic recovery, because the kiln dust contains on average 2.4% of nickel. The survival of the pellets to the rotary kiln is essential for stability, productivity and metal recovery. This work had as main objective the determination of the optimum point of operation of the pelletizing disks, aiming to increase the mechanical resistance (kgf) of the pellets using the statistical design and analysis of experiments. Through a factorial experiment with two factors: with a disc speed levels in% RPM (factor A), b feed rate levels in t/h (factor B), n replicates and each replica containing all combinations of factors A (velocity of the disk) and B (feed rate), the ANOVA was performed for factor A, factor B and interaction between them. After the ANOVA, it was possible to infer, through the Tukey multiple comparison methods, the best point of operation. The best operating condition was the replicated to all four pelletizing discs. After three months of operation in the optimized condition, it was possible to verify the reduction of around 3% in the recirculation of kiln dust. The reduction of the circulating kiln dust load due to the increase in pellet resistance allowed the production to increase by 114 t nickel/year, net adds of USD 365,545/year, a reduction of 3.200 m3 of water/year, 11.7 thousand GJ/year and a reduction of 1,5 thousand tons of CO2eq/year.