Advances in Sintering of Iron Ores and Concentrates

Chapter “Sintering of iron ores and concentrates” is focusing on the study of theoretical, thermodynamic and experimental results in the production of sinters from iron ores and concentrates. The authors of the chapter have long been interested with the production of sinter from iron ores and have recently also focused on the use of biomass as a substitute for a part of coke breeze in the production of iron sinter. Important characteristics of the chapter include the characteristics of iron ores and concentrates used to produce sinter including physico-chemical, mineralogical and metallurgical properties. Predicting the influence of the properties of iron ores and concentrates on the final quality of the sinter and on the production of pig iron is another part of the study. These properties are a key factor in achieving the highest possible agglomerate quality for pig iron production. The sintering process requires mathematical and physical modeling. For this reason, the authors created thermodynamic models of sintering including material-heat balance of sinter production. In the final part of chapter is the use of traditional and alternative carbonaceous fuels in the production of sinters, mainly in the context of replacement of coke breeze with biomass

New Approach in Research of Quartzes and Quartzites for Ferroalloys and Silicon Production

This article deals with material research of selected types of quartz and quartzites in order to determine the priority of their use in the production of ferrosilicon and pure silicon, respectively. The highest quality quartzes and quartzites are commonly used in metallurgy, but not all types of these silicon raw materials are suitable for the production of ferrosilicon and pure silicon, despite their similar chemical composition. Behavior differences can be observed in the process conditions of heating and carbothermic production of ferrosilicon and silicon. These differences depend, in particular, on the nature and content of impurities, and the granularity (lumpiness) and microstructure of individual grains. The research focused primarily on determining the physicochemical and metallurgical properties of silicon raw materials. An integral part of the research was also the creation of a new methodology for determining the reducibility of quartzes (or quartzites), which could be used for real industrial processes and should be very reliable. The results of the laboratory experiments and evaluation of the physicochemical and metallurgical properties of the individual quartzes (or quartzites) are presented in the discussion. Based on comparison of the tested samples’ properties, their priority of use was determined. This research revealed the highest quality in quartzite from Sweden (Dalbo deposit) and Ukraine (Ovruč deposit) and quartz from Slovakia (Švedlár deposit). The use of these raw materials in industrial conditions is expected to result in the achievement of better production parameters, such as higher yield and product quality and lower electricity consumption

Ore Assimilation and Secondary Phases by Sintering of Rich and High-Gangue Iron Ores

During the iron ore sintering process, two types of particles are present in the sinter bed: (1) fines, which are actively taking part in melting and the formation of secondary phases, and (2) coarse ores, which are partially interacting with the surrounding melt. The quality of the final sinter is particularly determined by the secondary phases and their bonding ability. Due to chemical differences between the fines and coarse particles, knowing the overall chemical composition of the sintering blend is not sufficient to estimate the final sinter microstructure. In this study, different ore types were used to prepare iron-rich, high-alumina, and high-silica blends, which were sintered in a laboratory sinter pot to investigate the behavior of fine as well as coarse particles. As a result, very different sinter matrices formed depending on the useful basicity in each sinter. The density, mineral nature, and the gangue of the ore affected coarse ore assimilation

New Utilization of Specific Biomass: Lignin in the Iron Ore Sintering Process

The use of lignin can be one of the methods of coke powder substitution in the agglomeration process. This article specifies the material research of lignin and the technological and ecological parameters of the agglomeration process in laboratory conditions using biomass lignin. The methodology of the Raman and infrared spectroscopy, representing a new approach in the analysis and assessment for the purposes of material characteristics for the agglomeration process, was applied to study the structure of carbonaceous matter. The material research of lignin has determined that its calorific value corresponds to ca. 80% of the calorific value of coke powder, while its reactivity is higher than that of the coke. Although the substitution of coke powder using different types of waste biomass (e.g., wood sawdust) in the production of the agglomerate is limited to the maximum of 8–15%, in case of lignin, more than 20% can be substituted, while the standard properties of the produced agglomerate are maintained. The lower emissions of sulfur and nitrogen oxides as well as the reduction of carbon footprint in the agglomeration process as a result of the so-called zero CO2 balance in the formation and processing of the biomass represent its positive aspects. Based on the laboratory research of lignin, up to a 50% substitution of coke powder with this type of biomass can be predicted for the technology of agglomerate production in real operation

The Effect of Concentrate/Iron Ore Ratio Change on Agglomerate Phase Composition

The work is focused on studying the influence of the ratio of concentrate to iron ore on the phase composition of the iron ore agglomerate. The concentrate has significantly higher iron content than used iron ore, and is a determining factor, which influences the richness of the batch and consequently, the richness of the agglomerate. The increased iron content in the agglomerate can be achieved by adjusting the raw material ratio in which iron ore materials are added to the agglomeration mixture. If the ratio is in favor of iron ore this reflects in lower iron content in the resulting agglomeration mixture. If the ratio is in favor of a concentrate, which is finer, the fraction share of less than 0.5 mm will be increased, the permeability of the batch will be reduced, the performance of the sintering belt will decrease and the presence of solid pollutants will increase. The possibility of concentrate replacement by iron-rich iron ore with granulometry similar to that of concentrate was experimentally verified. The effect of the concentrate replacement by the finer iron-rich ore was tested in a laboratory sintering pan. There were performed six sinterings, with gradually changing ratio concentrate/iron ore (C/O). The change in the ratio of concentrate to iron ore, does not cause the occurrence of new phases, only the change in their prevalence, which does not bring a significant change of the qualitative indicators of the compared agglomerates. Concentrate replacement by iron ore up to 50% was optimal from technological, quality, and environmental aspects

A Comprehensive View of the Optimization of Chromium (VI) Processing through the Application of Electrocoagulation Using a Pair of Steel Electrodes

In the presented article, an electrocoagulation method using a steel cathode and a steel anode was used to obtain chromium from laboratory-prepared model solutions with known compositions. The study aimed to analyze the effect of solution conductivity, pH, and 100% efficiency of chromium removal from the solution, as well as the highest possible Cr/Fe ratio in the final solid product throughout the process of electrocoagulation. Different concentrations of chromium (VI) (100, 1000, and 2500 mg/L) and different pH values (4.5, 6, and 8) were investigated. Various solution conductivities were provided by the addition of 1000, 2000, and 3000 mg/L of NaCl to the studied solutions. Chromium removal efficiency equal to 100% was achieved for all studied model solutions for different experiment times, depending on the selected current intensity. The final solid product contained up to 15% chromium in the form of mixed FeCr hydroxides obtained under optimal experimental conditions: pH = 6, I = 0.1 A, and c (NaCl) = 3000 mg/L. The experiment indicated the advisability of using a pulsed change of electrode polarity, which led to a reduction in the time of the electrocoagulation process. The results may help in the rapid adjustment of the conditions for further electrocoagulation experiments, and they can be used as the optimization experimental matrix