Phase Composition of Iron Ore Sinters Produced with Biomass as a Substitute for the Coke Fuel / Skład Fazowy Spieków Żelaza Wytworzonych Z Dodatkiem Biomasy Jako Zamiennika Dla Koksu

Abstract

The effort to minimize CO2 emissions leads the existing integrated steel plants to implement alternative biomass-based fuels that dispose of equilibrium carbon balance. The fuel is a key factor in the iron ore sinter production, so it is essential to know its impact not just on mechanical properties of the finished sintered ore but also on the mineral composition as the mineral phases together determine all observed sinter properties. For this purpose the samples prepared by replacing a part of coke breeze with charcoal or walnut shell substitute were subjected to the observation under the light microscope, also using etching, to the phase identification by chemical EDX analysis on the scanning electron microscope and to the phase composition quantification by X-Ray diffraction analysis. The studied microstructure areas in the vicinity of the pores left by fuel grains were neither characterized by different phases nor by changed chemical composition of these phases even thought mineral matter of the used fuels were substantially different in terms of the chemical composition. The only feature of the burned substitute fuels were ash particles arranged in characteristic shapes. The main reason of variation in ratios of respective mineral phases of samples appeared to be thermal conditions that were reflected in the content of unreacted non-ferrous phases. Coke substitution in the sinter mixture has no negative impact on the phase composition of the produced sinters, which confirms the prospective use of biofuels in the sintering process.

Comparison of Iron Ore Sinter Mineralogy Quantification

“…Then, diffraction patterns for SFCA and SFCA-I replaced calcium ferrites from the set A -this set of evaluations is denoted as "set B". In all cases, the final XRD results were supported by microscopic examinations, as reported earlier [12].…”

“…The five sinter samples for this study were chosen from previous work [12]. Powder X-Ray diffraction analyses of iron ore sinter samples were performed using diffractometer SEIFERT XRD 3003/PTS.…”

“…Of course, this applies to older studies as well. In the current literature [11][12][13][14][15][16], it is common to substitute SFCA and/or SFCA-I [17]. The main aim of the article is not to propose the replacement of diffraction patterns of mineral phases in sinters by others, but show the changes in phase quantification, which can occur when diffraction patterns of SFCA/SFCA-I are used instead of other calcium ferrites.…”

Silico-ferrite of Calcium and Aluminum Characterization by Crystal Morphology in Iron Ore Sinter Microstructure

“…6) If the proposal is right, that SFCA-I cannot crystallize from melt, there must be some SFCA-I preserved in a solid state during the melting period. After the melting period and the following cooling period, unmelted SFCA-I crystals act as contact areas for heterogeneous nucleation of newly crystallized SFCA.…”

“…6) The second group are the quaternary calcium ferrites, commonly named complex, because they also contain some other elements, such as Mg, Fe 2 + , Na etc.. Usual name of these ferrites is silico-ferrites of calcium and aluminum with the acronym SFCA. 7) After researches in the field of mineral's structure the SFCA-s were divided into low-Fe type, designed as simple SFCA with the basic formula Ca 2 (Ca,Fe,Mg,Al) 6 7,8) They are both very common in iron ore sinters and make a majority not only among the bonding phases but sometimes also in the whole sinter. By contrast to mentioned binary ferrites, SFCA has another structure quite different from calcium diferrite CaFe 4 O 7 , which is triclinic or monoclinic, respectively.…”