Abstract
The influence of binders on the mechanical properties of chromite, self-reducing pellets, after subjecting to high temperatures, is analyzed in this paper. Bentonite, sodium silicate, and a combination of bentonite with carboxymethyl cellulose (CMC) were tested with different contents. All of the raw materials were characterized by chemical analysis and particle size distribution. The materials were pelletized (P1 to P7). All of the bounded green and dried pellets (P2 to P7) achieved the desired mechanical strengths, and none presented decrepitation. The best performance was obtained by the pellet P7 (4% sodium silicate as binder), with the green strength of 34 N/pellet, the dried strength of 50 N/pellet, and the strength was higher than 110 N/pellet after heat treatment at critical temperatures between 1173 and 1373 K. The unitary reduction reaction fraction was achieved after 10 minutes, at 1773 K.
Highlights
According to Mantovani[1], Marcheze[2] and Zambrano[3,4,5,6], the production of high-carbon ferrochrome using carbon composite pellets by the self-reduction process at the laboratory level is a process that presents technological advantages
Some features are the usage of fine chromite ore and reducing agents and high efficiency and high productivity resulting from a high reaction rate, reaching almost unit reduction reaction fraction in 5-10 minutes at 1773K
The conclusions of the chromite ore-coke composite pellets bound with bentonite and sodium silicate are:
Summary
According to Mantovani[1], Marcheze[2] and Zambrano[3,4,5,6], the production of high-carbon ferrochrome using carbon composite pellets by the self-reduction process at the laboratory level is a process that presents technological advantages. Energy should be supplied to the agglomerate for a highly endothermic reduction reaction, and, more importantly, the cold-bonded agglomerate should have enough strength without degradation throughout the entire process. The self-reducing chromite pellets using Portland cement as a binder require more than 10% Portland cement to achieve cold strength for handling and loading into electrical furnaces. The hydration reaction of cement confers good cold strength at temperatures up to approximately 973 K, when the dehydration starts. Mainly above 1173 K, the degradation is higher due to more intense dehydration coupled with reduction reactions. This phenomenon is critical for iron ore pellets because the strength decreases in the temperature range of 973-1223 K.
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