Estudo da influência da sinterização de minérios de ferro na redução por hidrogênio.

Abstract

This work aimed to study the sinter reduction by hydrogen produced with charcoal and coke breeze. Three kinds of hematitic sinter feeds were used. The materials were characterized by particle size analysis, chemical analysis, X-ray diffraction optical and scanning electron microscopy. The inicial sintering tests aimed to produce return fines for subsequent sintering. Mixtures adding the sinter feed residue from the pellets process were sintered to evaluate the addition effect of this product in the process of sintering. A test was conducted to verify the effect of elimination of fines present in the sinter return sintering process. Six sintering tests were conducted replacing coke breeze by charcoal as process fuel. The replacements were 0%, 8%, 16%, 25%, 50% and 100%. The samples with substitutions of 0%, 50% e 100% were reduced in thermobalance for 6 hours at a temperature of 1000°C using a blend of gases containing Argon-10% Hydrogen. The samples which presented the best and the worst reducibility were studied through kinect calculations to determine the reaction mechanisms involved during the reduction of oxide. The step of microscopic characterization of reduced sinters was carried out in a way that made possible to compare the sinter sample before and after the process of reduction. The results showed the sinter made with charcoal decrease the sinter rates of production and resistance. However, the sinter made using only charcoal as fuel presented better reducibility. The kinect calculation denotes both for the sinter made with charcoal and sinter made with coke breeze the controlling mechanism in the initial stages (between 50 and 55 minutes) is the chemical reaction. For the sinter produced with charcoal the controlling mechanism switches for mixed control. The sinter produced with coke breeze, the mechanism switches for diffusion. Tests interrupting the reduction time for 40min, 80min e 120min (40min + 40min + 40min) were produced with sinter sample produced with 8% with charcoal. At this stage it was possible to identify the phenomena of nucleation and growth phase of metallic iron on the sinter structure.

Aplicação de resíduo de palma como fonte de carbono em briquetes autorredutores de minério de ferro.

“…O teste de tamboramento é feito visando a determinação da geração de finos causada por abrasão do briquete quando está em contato com as paredes do forno e com a carga (TELLES, 2015). Além disso, esse processo mede a friabilidade do material, tendência do mesmo a gerar pó quando passa por processos de manuseio ou durante o transporte e armazenamento (ZANELLA, 2018)…”