Influência da adição da lama fina de aciaria a oxigênio nas características físicas e microestruturais de pelotas queimadas de minério de ferro

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

At the Brazilian steelmaking industry, the estimated annual production of steelmaking BOF sludge is about 230 thousand tons. The BOF sludge is a residue typical of oxygen steel mills. The main chemical and granulometric characteristics of the steelmaking BOF sludge are the following: about 30% of BOF thick sludge, with high metallic content and granulometry above 325# (45m), and 70% of fine sludge, rich in iron oxide, FeO, presenting a granulometry lower than 325# (45m), with a total iron content of about 60% of its weight. Some recent studies in China, performed in pilot scale, investigated the use of fine sludge in the process of iron ore pellet production. In Brazil, studies about the applications of the steelmaking BOF sludge are still scarce, despite of its huge industrial production of iron ore pellets and a considerable annual generation of BOF sludge. This work presents a study of the influence on the intrinsic characteristics of the iron ore oxide pellets, by the addition of the BOF sludge in small proportions. The chemical analysis employed the spectrometry by atomic emission and titration techniques. The mineralogical characterization was performed by X-ray diffraction and optical microscopy. In addition, the porosity analysis is displayed. After the characterization, the samples were submitted to agglomeration tests in pelletizing disks, fall resistance test, thermal processing and compression test. The influence of the addition of fine sludge was analyzed on the resistance to compression and the chemical, porosity and microstructural characteristics of the iron ore oxide pellets. The sludge is composed of wustite, iron, magnetite, calcite, hematite and cristoballite (quartz ß). It also presents some interesting chemical characteristics regarding the CaO (18.68%) and MgO (5.63%) contents, that can contribute to the reduction in usage of the flux agents that carry those oxides at the pelletizing process. The addition of fine sludge at 0.5% to 2.0% does not affect the fall resistance of green pellets. In conformity with the thermal profile adopted (thermal processing total time of 4 hours), high values of compression resistance were obtained, at the temperatures of 1.2000 C, 1.2600 C and 1.3200 C. Adding the sludge at 0.5% to 2.0%, there is a significant increase in porosity (varying from 18% to 29%), however the compression resistance obtained during the thermal processing is not affected. The microstructural characteristics of the iron ore oxide pellets are little affected by the addition of the steelmaking BOF sludge. In all of the studied conditions, and for the thermal cycle employed, the presence of cracks on the oxide pellets was not observed. The employment of a long processing period and slow cooling allowed for the hardening of oxide pellets without the appearance of cracks, therefore increasing the resistance despite the increase in porosity.

ASSUNTO(S)

steelmaking sludge bof, pelletizing, iron ore lama de aciaria, pelotização, minério de ferro engenharia de materiais e metalurgica

ACESSO AO ARTIGO

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