Desenvolvimento de briquetes autorredutores utilizando resíduos da indústria metalúrgica de ferrossílicio

Abstract

Aiming to contribute to the studies of the ferroalloys sector, this work aimed to evaluate the technical feasibility of using the residues generated from the production process - silica fume, iron ore and charcoal fines - and use them as raw material. Prime to develop self-reducing briquettes, in order to promote its insertion as a complementary charge in submerged arc electric furnaces (SAF), in the production of FeSi. After the characterization of the residues, 52 treatments of self-reducing briquettes were produced, considering four conditions, these being without and with binders. In the latter case, three types of binders were used (Portland cement, hydrated lime and sodium silicate), following the proportion (2.50%; 5.00%; 7.50% and 10.00%). Initially, the briquettes were tested for bulk density, porosity, shatter test and resistance to hot degradation. It should be noted that only two treatments – out of a total of 52 – met all the pre-established selection requirements. These treatments have in its composition the solid silicate binder (5.00 and 7.50%) and produced with 15.00% water. The treatment with 5.00% sodium silicate as binder, obtained the following characteristics, bulk density: 1165.39 kg/m3; porosity: 46.19%, shatter test: 99.64% at 0.30m and 99.32% at 1.50m; and resistance to hot thermal degradation: Rdr 81.24%. The treatment using 7.50% of sodium silicate, on the other hand, presented bulk density: 1246.85 kg/m3; porosity: 46.00%, shatter test: 99.66% at 0.30m and 98.82 at 1.50m; and resistance to hot thermal degradation: Rdr 82.54%. Through the identification of mineralogical phases in the 2 selected treatments, by X-Ray diffraction, the presence of predominant phases of quartz, hematite and calcite was observed in the samples. After this procedure, reduction tests were carried out to investigate the self-reducing character, under different heating temperatures (1750, 1800, 1850 and 2000ºC). The metallic and carbonaceous phases were identified by scanning electron microscopy (SEM) and their chemical composition determined by energy dispersion X-ray spectroscopy (EDS). Based on these tests, metallic phases of interest were identified, which were identified as metallic Si, FeSi, FeSi2 in percent Si mass of 85.77%; 30.72% and 47.17%, respectively, and carbon phase with Si content of 71.83% for SiC. From the results, one can see the potential of using the selfreducing briquettes elaborated in this dissertation as an alternative as an alternative complementary load in SAF to obtain FeSi.