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Production of iron ore pellets with enough strength to resist the transport and reduction on reactors requires an accurate adjustment of traveling grate furnace process parameters. The firing zone is the most energy intensive step to ensure quality and this study based on Lean Six Sigma methodology to evaluate and optimize the thermal profile through temperature fine-tuning. A pilot scale assessment aid to analyze physical, chemical, metallurgical and microstructure properties of pellets through different temperatures to accurate industrial implementation. The validation of lab-scale trials was concluded by industrial implementation to guarantee the quality, productivity and reduced costs. [ABSTRACT FROM AUTHOR]

Brazil is the second-largest producer of iron ore in the world. Brazilian richer superficial deposits are composed of brittle material with fine texture and significant amounts of fines are generated during mining and transport. Another type of ore found in this country is the itabirites that have lower iron contents. Beneficiation and concentration steps are required to prepare these materials for the pelletizing process. A general view of Brazilian types of iron ores, mines, and mining companies is given in this work. Special attention is given to pelletizing and the influence of mineralogical characteristics of different ores on the production and final properties of iron ore pellets. [ABSTRACT FROM AUTHOR]

Abstract Fly ash particles from the combustion of solid-fuels together with disintegrated particles arising from iron-ore pellets result in accumulation of deposits on the refractory linings of the grate-kiln induration machine during the iron-ore pelletizing process. The deposits amass in the high-temperature regions of the induration furnace thus disturbing the flow of gas and pellets. Therefore, to tackle the above-mentioned issues, an understanding of deposit formation mechanism is of crucial importance. This study was conducted with the objective of addressing the effect of disintegrated iron-ore pellet dust on deposit formation and the mechanisms behind deposition (slagging) in the grate-kiln process. A comprehensive set of experiments was conducted in a 0.4 MW pilot-scale pulverized-coal- fired furnace where three different scenarios were considered as follows; Case 1 (reference case): Coal was combusted without the presence of pellet dust. Case 2 : Natural gas was combusted together with simultaneous addition of pellet dust to the gas stream. Case 3 : Coal was combusted together with the addition of pellet dust simulating the situation in the large-scale setup. Fly ash particles and short-term deposits were characterized and deposition was addressed in Part I of this study. In light of the experimental observations (Part I) and the thermochemical equilibrium calculations (Part II), a scheme of ash transformation during the iron-ore pelletizing process was proposed. The dissolution of hematite particles into the Ca-rich-aluminosilicate melt (from the coal-ash constituents) decreased the viscosity and resulted in the formation of stronger (heavily sintered) deposits. Overall, this pilot-scale work forms part of a wider study which aims at deepening the understanding of ash transformation phenomena during the large-scale pelletizing process. Highlights • Addition of pellet dust reduces the liquidus temperature. • Interaction between coal ash and pellet dust at low temperatures is limited. • Addition of pellet dust increases the amount of liquid slag at high temperatures. • Pellet dust reduces the viscosity, hence formation of stronger deposits. • A sequential ash transformation scheme in iron-ore pelletizing was proposed. [ABSTRACT FROM AUTHOR]

A novel flash ironmaking technology (FIT) based on the direct reduction of iron ore concentrate with a reductant gas (such as hydrogen, natural gas, coal gas, or a combination thereof) in a flash furnace is being developed at the University of Utah. This technology which is undergoing large-scale laboratory testing aims at overcoming the limitations of blast furnace ironmaking by bypassing the problematic pelletization/sintering and cokemaking steps.[1-5] Refractory selection is expected to play an important step in the development of FIT and its proposed scale-up. For nominating an appropriate refractory for the FIT, understanding the interactions of candidate refractories with iron/iron oxide and slags under H2/CO/CO2/H2O environments is necessary. This work is undertaken to review the existing literature on the interactions of important refractories with iron melts and relevant slags with an emphasis on two of the most commonly used refractories in ironmaking and steelmaking applications: the alumina-based refractories (used widely in blast furnace operations) and the magnesia-based refractories (used extensively in primary as well as secondary steelmaking). First, a comprehensive review on the interactions of alumina-based refractories with iron melts and slags has been done. Next the existing literature on the interactions of magnesia-based refractories with iron melts and relevant slags has been reviewed. Summaries have been included after each section and sub-section along with comments and critical insights from the authors. Finally, in the concluding remarks the differences in operating conditions between existing iron and steelmaking practices and the novel FIT have been highlighted. On the basis of these differences, it has been argued that the results and conclusions available from previous studies on refractory-metal-slag interactions are of little significance to flash ironmaking. Thus, there exists a need to carry out laboratory experiments for evaluating refractory performance in flash ironmaking under conditions relevant to the current process (FIT). [ABSTRACT FROM AUTHOR]

Iron ore slime is generated from mines during processing and washing of iron ore, and it is not considered for pelletizing due to its excessive fineness and high gangue content, despite its good green bonding property. Mill scale is generated from steel rolling mills and reheating furnaces; it has almost nil gangue content, but is not individually considered for pelletizing due to its poor green bonding property. If both of these two wastes are blended in combined form with hematite ore, the high gangue of slime would be balanced by the gangue free mill scale. While mill scale provides exothermic heat of oxidation of FeO and Fe3O4 in it and enhance the diffusion bonding, slime provides good green bonding property to the pellet. Therefore, in this study a good quality pellet was developed by the combined mixing of these two wastes in hematite ore without much increase in gangue content. Up to 15% of mill scale and 15% of slime could be used successfully. The developed pellets provide improved cold compressive strength (366 kg/ pellet), reducibility index (82%), and reduction degradation index (8.5%). Induration temperature could be reduced by 75 °C, which indicates a considerable energy saving in induration furnace. [ABSTRACT FROM AUTHOR]

The Ezhou pelletization plant of the BAOWU with production capacity of 5,000,000 ton oxide pellets per year has the biggest single production line of Grate-Kiln-Ring cooler, which was provided by Metso Company. The iron concentrate was mainly imported from Brazil and self-provided by Jinshandian. The iron concentrates were dried and ground by the high pressure roller. The ground iron concentrates were pelleted by drum and disc pelletizers. The qualified green pellets were subjected to grate, rotary kiln, and ring cooler successively. The innovation and creation of process and equipment of Ezhou pelletization plant of BAOWU plays an exemplary role for the application of large-scale grate-kiln-cooler in iron and steel industrial. The use of the high pressure roller grinding significantly improved the pelletization ability of the iron concentrate and the quality of the finished pellets. Compared with other same scale grinding equipment, it is more energy-saving. The combined technique of high pressure roller with wet ball mill grinding was used to treat some hard specularite with large particle size. The first successful application and design of electrostatic precipitator on the large-scale grate-kiln in China provides a good foundation for other large-scale pellets plants. [ABSTRACT FROM AUTHOR]

Process sampling is involved in grade control in all parts of the production value chain in mineral processing. Reliable sampling and assaying is essential to ensure final product quality, but the need for representative sampling is not always taken into account. By continuous control of the variability of sampling systems, a comprehensive understanding of the relationship between the sampling and process variability can lower the risk for overcorrections of process parameters due to sampling variability rather than process changes. Variographic characterization of process sampling makes it possible to assess all combined sampling and analytical errors from only 40–60 routine analytical values. The objective of this study is to evaluate total sampling variability in relation to process variability in the concentrating and pelletizing process sampling at LKAB. The results from the variographic analyses will form a basis for suggestions of possible improvements. The results show that variographic analysis is a powerful tool to evaluate both process variations and the variability of the sampling systems employed. The extensive access to time series data allow variographic characterization (quality control) of all critical measurement systems and locations. At the same time, periodicity and small changes in process variation can be detected and counteracted early, minimizing the risk for producing products out of specification. [ABSTRACT FROM AUTHOR]

The main unit operations of pelletizing process are grinding, filtering, pressing, pelletizing, and firing. Grinding, the first operation in the process, is a crucial step for the subsequent operations. Three iron ore mixtures with different grindability index (low, medium, and high) were used in order to verify the influence in the operational parameters such as production rate, discharge density, and pump pressure. Through Design of Experiments (DOE), nine experiments over each iron ore mixture were done, varying the minimum and maximum grinding operational parameters. Independent variables (responses) were the specific surface area or Blaine index (BI) and the particle size (PS), which were measured by the automatic PS analyzer system (PSI). The main objectives of this study are to know the behavior of iron ore mixtures with different grindability indexes in the industrial plant and develop a regression model that can be used for real-time measurement of PS and BI for different grindability indexes in the industrial operations. The results showed satisfactory correlations between the factors and responses. [ABSTRACT FROM AUTHOR]

Green pellets are spherical objects mainly made from crushed iron and water in rotating pelletizing disk. Pellets play an important role in the process of direct reduction steel manufacturing. For high quality steel production, pellets should be of an appropriate size. Oversized pellets cannot be properly cooked in furnace and undersized pellets may pass through metal grid of the furnace, which affects the performance of the process. In most of the steel manufacturing companies, operators use sequential sampling and traditional methods to measure size of pellets, however, limited number of tested pellets, low speed of the quality control and human errors are the most common drawbacks of this method. A solution to these shortcomings is continuous monitoring and accurate measurement through a fully-automatic approach. In this paper, a method using image processing technique is proposed and verified for estimating size distribution of iron-ore green pellets. For segmentation of single and multiple pellets in images captured from live video, we have utilized morphological methods, watershed algorithm, and linear searching. Then, a Support Vector Machine (SVM) is employed for classification of segmented pellets. The proposed method has already been implemented in Mobarakeh Steel Complex, where the method was tested on about 1000 sample pellets. Results show that the accuracy of method is 95.1% in detection of single pellet elements. [ABSTRACT FROM AUTHOR]

In this study, potassium chloride (KCl) containing matrix pellets were compressed into tablets using powder or pellet form of partially spray dried lactose as filler-binder excipient. The spatial distribution of potassium chloride pellets within the tablets was examined by non-destructive microfocus X-ray imaging (MFX) and image analysis technique. The KCl content of the tablets was determined by conductivity measurement and these values were compared to the average gray values of the MFX images calculated by image analysis software. A linear relationship has been shown between the KCl content predicted from average gray values of the MFX images and the actual KCl content measured by conductometry. The non-destructive MFX method was capable to characterize the pellet distribution as well as the pellet content of the multiparticulate dosage form. Based on the observed spatial distribution of KCl pellets within the tablets made using lactose pellets or powder for direct compression as filler excipients the difference in homogeneity was not remarkable besides the applied blending method. [ABSTRACT FROM AUTHOR]

In this study, the effects of process parameters, such as gas composition and reduction temperature, were investigated. X-ray diffraction and scanning electron microscope were used to identify the products in different atmospheres. Experimental results indicate that the three-dimensional diffusion controlled model is suited to the reduction process. The compressive strength of the produced pellets gradually decreased as the temperature increased from 700 °C to 900 °C in all atmospheres. The formation of the iron whiskers made the adjacent grains loose and eventually caused the decrease of the compressive strength. The presence of H 2 atmosphere had a strong effect on the pellets reduction due to the formation of porous and fibrous iron. [ABSTRACT FROM AUTHOR]

In this study, mass loss and direct reduction characteristics of red mud and iron ore pellets in different atmosphere and temperature was investigated. The reaction kinetics parameters were estimated based on the experiments and different model equations. In addition, the phase transformation and microstructure of the reduction process were studied by X-ray diffraction technique (XRD) and Scanning electron microscope (SEM). The results show that the reduction process is three-dimensional phase-boundary controlled in H 2 and CO atmosphere. The rate of reduction in the presence of H 2 is significantly higher than in the CO atmosphere above 900 °C. 1100 °C and hydrogen atmosphere is optimum for the reduction of both iron ore concentrate and red mud pellets in the experimental conditions. [ABSTRACT FROM AUTHOR]

Results are given for analysis of agglomerate and pellet physicochemical properties. It is shown that with transfer of blast furnace smelting into an operating regime with a high proportion unfluxed pellets in a charge requires changing the main slag regime parameters, and also the furnace charging regime. It is established that due to the difference in agglomerate and pellet physicomechanical properties, and also as a result the high corrosiveness of primary slag obtained using unfluxed pellets, it is necessary to change the regime for material charging into a furnace. With an increase in the proportion of Sokolovo-Sarbaiskii Ore Mining and Processing Combine pellets in Magnitogorsk Metallurgical Combine blast furnace charge, there is a reduction in amount of magnesium in final blast furnace slags. This is accompanied by an increase in molten slag viscosity, a reduction in its sulfur absorbing capacity, and also an increase in the temperature range for iron ore mix melting with an increase in bottom gas pressure drop and limiting melt blast force. [ABSTRACT FROM AUTHOR]

In the process of direct reduction of iron pellet and production of sponge iron, NiO/Al2O3 act as a catalyst for the generation of carbon monoxide and hydrogen by vapor and natural gas. As an expensive material used in MIDREX method for steel units, this type of catalyst has major environmental problems after accumulation. The steel industry in Iran hopes to employ the MIDREX technique for the 80 percent of the 50 million tons of steel. Thus, the problem of spent catalysts will become a serious environmental challenge. Through the hydrometallurgy method, the present study investigates a possible solution to the problem of catalyst depot (due to heavy metals such as nickel) via nickel recovery, which may increase the possibility of selling or re-using the precious and expensive metal. The present research studied the Nickel recovery from spent catalysts of NiO/Al2O3 used in reduction gas reliefs of the production of sponge iron unit. In this study, the parameters of temperature, concentration, time and Rpm were studied using pressurized dissolving method. 100% efficiency was achieved at 140 °C for 120 minutes, nitric acid concentration of 1.5 mm, Rpm of 600 and 40 s/l 40 grams per liter. [ABSTRACT FROM AUTHOR]

The objective of this research is to assess how much the improvement in the combustion reaction efficiency can reduce fuel consumption, maintaining the same thermal energy rate provided by the reaction in a pelletizing furnace. The furnace for pelletizing iron ore is a complex thermal machine, in terms of energy balance. It contains recirculation fan gases and constant variations in the process, and the variation of a single process variable can influence numerous changes in operating conditions. This study demonstrated how the main variables related to combustion in the burning zone influence fuel consumption (natural gas) from the furnace of the Usina de Pelotização de Fábrica (owned by VALE S/A), without changing process conditions that affect production quality. Variables were analyzed regarding the velocity and pressure of the fuel in the burners, the temperature of the combustion air and reactant gases, the conversion rate and the stoichiometric air/fuel ratio of the reaction. For the analysis, actual data of the furnace in operation was used, and for the simulation of chemical reactions, the software Gaseq® was used. The study showed that the adjustment of combustion reaction stoichiometry provides a reduction of 9.25% in fuel consumption, representing a savings of US$ 2.6 million per year for the company. [ABSTRACT FROM AUTHOR]

Iron ore having high-sulfur content causes problems in the concentrate production, pelletizing, and steel-making processes and environmental issues such as sulfur dioxide emission during the concentrate pelletizing process, and effect on steel quality. The current study was focused on the removal of sulfur from iron ore concentrate using chemical leaching technique. Magnetite iron ore concentrate was chosen for this purpose. The results obtained from the study showed that more than 90% of the total sulfur content was removed from the iron ore concentrate by the chemical leaching. Effects of several parameters, including temperature, stirring speed, particle size, and use of organic solvent on the sulfur removal was investigated by a series of experimental conditions. After optimizing the experimental conditions, it was demonstrated that in addition to sulfur, more than 80% of phosphorus, another important impurity, was also removed from the iron ore concentrate. In addition, one of the major advantages of our proposed method was the transformation of mineral pyrites to useful byproducts such as elemental sulfur. [ABSTRACT FROM AUTHOR]

In this study, sodium, calcium, and mixed bentonite samples were used as binders in the pelletizing fine iron ore concentrate obtained from the Divrigi Iron Ore Concentration Plant in Turkey. In the pelletizing tests, sodium bentonite sample was used as received and after upgrading process. Additionally, the calcium bentonite sample required activation by sodium bicarbonate while the mixed bentonites sample was used untreated and as well as activated. The pellets produced were tested for compressive strengths, drop number, and porosity in order to characterize the pellets. The results showed that untreated and upgraded sodium bentonite samples provided relatively stronger pellets compared to calcium and the mixed type bentonite samples needed activation with sodium bicarbonate to increase the strength of the pellets. Based on the results of the drop number, compressive strengths, and porosity, it is possible to make pellets which meet the standards by adequate addition of type and amount of bentonite. [ABSTRACT FROM AUTHOR]

Vertical Agitated Media Mill modeling has become subject of a research project due to its potential application as a secondary grinding mill as well as regrind and pellet feed preparation projects. A test campaign with a pilot scale vertical mill was carried out with five different ore samples to elaborate a simple and robust methodology to scale-up vertical mills and perform simulations. The methodology proposed considers breakage parameters determined from tests in a conventional batch ball mill and population balance model for simulations. The tests can be performed very quickly in any process laboratory with a small quantity of sample. Two different models can be used for scale-up purposes: the first is based on the specific grinding energy and the corresponding tests were carried out on samples with natural size distribution. The second is based on particle residence time distribution and the tests carried out with narrow sized particles. Breakage and selection function parameters were estimated from each test procedure. The results indicate that it is possible to perform vertical mill scale-up and simulations with acceptable accuracy using the results from laboratory ball mill tests. The data analysis showed that the ratio of grinding net powers between ball and vertical mills is approximately 1.35 for all samples tested. [ABSTRACT FROM AUTHOR]

Apart from tertiary and quaternary crushing applications in a wide variety of ore types, High Pressure Grinding Roll (“HPGR”) technology is also applied in regrinding of iron ore pellet feed concentrate. A relatively large number of units have been or are being installed in iron ore pellet feed over the last few years throughout the world, in various circuits of single pass or closed circuit in combination with ball milling or stand-alone arrangement, and a number in a set-up involving a closed circuit of partial product recycle. Whereas the HPGR function in comminution operations obviously is the size reduction, the main purpose in pellet feed applications is a combination of fines generation with a main emphasis of creating a high specific surface area increase. This publication discusses three aspects of the features and experiences for pellet feed applications; an approach on the effect of discharge recycle ratio on the product quality and HPGR operation, a description of the effects of material moisture, and a discussion on the use HPGR for final grinding in iron ore pellet feed preparation by use of air classification. [ABSTRACT FROM AUTHOR]

Humic acid (HA) was the predominant component of the MHA (modified humic acid) binder invented by the authors. This work aims to study the effect of the solution pH value on the HA adsorption onto natural magnetite/hematite/quartz particles and the strength of green pellets with the MHA binder. The SEM images for HA indicated that HA had distinct morphology at different pH values. The adsorption density of HA on the three oxide minerals was significantly pH-dependent and decreased with increasing pH value. The zeta potential values of the magnetite, hematite and quartz particles coated by HA became negative and the isoelectric point of the three natural oxide minerals disappeared in the tested pH value range. The electrostatic interaction and the ligand exchange were the two leading interactions for the HA sorption onto the magnetite/hematite particles, while the small adsorption amount of HA onto the quartz was attributed to the hydrogen-bond interaction. The pH value of the MHA binder solution affects markedly the strength of green pellets from magnetite and hematite concentrates. At pH ~ 7.0, the HA molecule was expanded and dispersed well and the relatively strong bonding bridges were formed among the iron ore particles. The optimal pH value was founded to be around 7.0 for preparing high-quality iron ore green pellets. [ABSTRACT FROM AUTHOR]

In this work, we report the development of a synthetic CO2 sorbent that possesses a high cyclic CO2 uptake capacity and, in addition, sufficient mechanical strength to allow it to be used in fluidized-bed reactors. To overcome the problem of elutriation of the original powdered material, the synthetic CO2 sorbent was pelletized. An important aspect of this work was to assess the effect of steam on the cyclic CO, capture capacity of the original, powdered CO2 sorbent and the pelletized material. After 30 cycles of repeated calcination and carbonation reactions conducted in a fluidized bed, the CO2 uptake of the pellets was 0.29 g of CO2/g of sorbent, a value that is 45% higher than mat measured for the reference limestone. For the case that carbonari on/calcination cycles were conducted in a thermogravimetric analyzer under steam-free carbonation conditions, the CO2 uptake of the best sorbent was 0.33 g of CO2/g of sorbent (after 10 cycles). Importantly, it should be noted that, after 10 cycles using wet carbonation conditions, the CO2 uptake of this material increased by 55% when compared to dry conditions. This observation was attributed to enhanced solid-state diffusion in the CaCO3 product layer under wet conditions. However, independent of the reaction conditions, the pelletized material showed a lower cyclic CO2 uptake when compared to the original powder. A detailed morphological characterization of the pellets indicated that the destruction of the primary, hollow micrometer-sized spheres during pelletization was responsible for the lower cyclic CO2 uptake of the pellets. [ABSTRACT FROM AUTHOR]

González, S.A.; Stotz, W., and Lancellotti, D., 2014. Effects of the discharge of iron ore tailings on subtidal rocky-bottom communities in northern Chile. Some of the many mining operations that exist in northern Chile dispose their mine tailings directly into the sea. Little is known about the effects of these tailings on shallow rocky subtidal communities. This study reports these effects for an iron ore pelletization plant that has discharged for ca. 23 years in the intertidal of a cove on the exposed rocky coast of northern Chile, generating high turbidity in the water column and deposit of sediments on the bottom. A nonparametric multidimensional scaling (nMDS) ordination analysis for the species of the rocky subtidal communities, based on the Bray-Curtis dissimilarity index, showed great differences, the affected communities being dominated by incrusting invertebrates, whereas the unaffected areas at the same depth had kelp beds. The effects were observed only close to the discharge and were not observed in the more shallow water communities, which in affected and unaffected areas consisted of barren grounds dominated by calcareous algae and sea urchins. The effect on the vertical zonation pattern of communities did not produce differences in the effective diversity, which turned out to be similar among affected and control sites. This occurred because of the replacement, more than the elimination, of species on affected sites. This type of study, in which information is generally maintained in reports only seen by industry and governments, needs to be published to contribute to a more comprehensive database for the improvement of decision-making processes regarding coastal subtidal rocky communities and the effects of human activities on these environments. En el norte de Chile se concentran numerosas operaciones mineras, las que en algunos casos depositan las colas de sus procesos directamente al mar, habiéndose reportado mortalidades masivas de peces, algas e invertebrados. Si bien se han realizado diferentes estudios para describir el impacto de estas descargas sobre las comunidades intermareales y de fondos blandos, los efectos sobre las comunidades submareales de fondos rocosos son escasamente conocidos. El presente estudio reporta los efectos sobre las comunidades de fondos rocosos producto de la descarga de sólidos inertes vertidos como colas de un proceso de pelletización de hierro por más de 23 años en Ensenada Chapaco, próxima a la ciudad de Huasco en el norte de Chile. La descarga del proceso minero generó alta turbidez en la columna de agua y un alto grado de sedimentación de material particulado fino sobre el fondo. El estudio incluyó un examen cuantitativo de las comunidades de organismos marinos presentes en los fondos rocosos al interior de Ensenada Chapaco. El análisis de ordenación nMDS, en base a las disimilitudes entre la flora y fauna bentónica de distintos sectores de estudio, usando el indice Bray-Curtis, mostró que las comunidades más profundas de Ensenada Chapaco presentan una estructura única, distinta a las comunidades de similares profundidades, pero ajenas al area de influencia de la descarga. Los resultados del análisis nMDS fueron consistentes para la comunidad completa, organísmos móviles, sesiles y organismos suspensívoros. Las comunidades afectadas estuvieron dominadas por organismos sésiles, como el caso de poliquetos tubícolas, cirripedios, mitílidos y briozoos mayormente de hábitos crípticos, siendo esta condición distinta a áreas no impactadas, donde se desarrollan bosques de algas pardas laminariales dominadas por Lessonia trabeculata. No obstante, estos efectos fueron evidentes sólo en puntos cercanos al area de descarga, no siendo afectadas, aparentemente, las comunidades de aguas someras. Estas comunidades, como también las de áreas ajenas a la decarga, presentan típicos 'fondos blanqueados' del submareal somero de la costa del norte de Chile, los que son dominados por algas calcareas incrustantes y erizos de mar. Si bien la composición y abundancia de los organismos es afectada, no ocurre así con la diversidad que se mantiene y hasta se incrementa el interior del area impactada. Esto se debe a que mas que una eliminación de especies, ocurrieron reemplazos. La modificación del patrón de zonación y de la estructura comunitaria producto de la descarga de las colas del proceso minero, produce un quiebre en la uniformidad del submareal de fondos rocosos de la costa del norte de Chile. Estos resultados resaltan la importancia de disponer de data científica detallada y actualizada sobre los patrones generales de las comunidades naturales de costa rocosa, así como la necesidad de definir metodologías estandarizadas e indicadores que permitan detectar los impactos producidos por la intervención humana sobre comunidades submareales de costa rocosa en el Pacífico Sur. Es necesario que este tipo de información, que generalmente es conocida solo por las empresas y el estado, sea publicada para ir enriqueciendo la necesaria base de datos para poder evaluar en su real dimension este tipo de impactos a lo largo de las costas. [ABSTRACT FROM AUTHOR]

Pelletizing iron ore fines is an agglomeration process that through a thermal treatment converts the ultra-fines fraction thereof into small balls ranging in size from 8mm (0.31 in.) to 18mm (0.71 in.), with adequate characteristics for feeding steel reduction works. The binder more used to make pellets is bentonite, which is an item of significant cost in the process. The present paper aims at evaluating the use of serpentinite instead of bentonite. The results obtained show that the full substitution of bentonite for serpentinite is unfeasible. However a potential does exist for using serpentinite and bentonite together in the iron ore palletizing process in the proportion of 1:1. [ABSTRACT FROM AUTHOR]

The process of pelletizing iron ore on disc pelletizers is mathematically modeled. Different methods of regression analysis are used to describe the pelletizing operation, and the equations that are obtained are compared with one another. The objective function is optimized based on the yield of green pellets of the class (-14+5) mm. [ABSTRACT FROM AUTHOR]

Bentonite is a predominant binder used in iron ore pelletization. However, the presence of a high content of silica and alumina in bentonite is considered undesirable for ironmaking operations. The objective of this study was to identify the alternatives of bentonite for iron ore pelletization. To achieve this goal, different types of organic and inorganic binders were utilized to produce iron oxide pellets. The quality of these iron oxide pellets was compared with pellets made using bentonite. All pellets were tested for physical strength at different stages of pelletization to determine their ability to survive during shipping and handling. The results show that organic binders such as lactose monohydrate, hemicellulose, and sodium lignosulfonate can provide sufficient strength to indurated pellets. [ABSTRACT FROM AUTHOR]

Abstract: The production of ferrochrome is an energy intensive process. At present, the pelletised chromite pre-reduction process is most likely the ferrochrome production process with the lowest specific energy consumption, i.e. MWh/t ferrochrome produced. Higher chromite pre-reduction levels correspond to lower specific energy consumptions. It was previously proven that various compounds could enhance the level of chromite pre-reduction. In this paper the effect of CaCO3 addition on pelletised chromite pre-reduction is presented. CaCO3 (as limestone) is already used as a flux in some FeCr production processes, hence its use does not constitute the addition of an extra raw material. Results indicated that CaCO3 addition enhance the level of chromite pre-reduction achieved significantly, which could results in substantial specific energy consumption improvements. However, CaCO3 addition caused severe decreases in both compressive and abrasion strengths of pre-reduced pellets, which is unlikely to be negated by mitigation measures. The addition of CaCO3 in the pelletised chromite pre-reduction process is therefore likely to result in the formation of excessively fine feed materials. In practise, this reduces the usefulness of this technique for submerged arc furnace ferrochrome production significantly, since excessive fines in the feed material are likely to result in increased operational instabilities, equipment damage and safety risks. TGA and thermochemical calculations also indicated that CO2 released from the CaCO3 will result in in situ carbon and energy consumption, which is an additional negative associated with its use as an additive during pre-reduction of composite chromite pellets. Although this paper was not specifically aimed at obtaining mechanistic information, thermo-mechanical analysis indicated that especially iron pre-reduction rates were enhanced by CaCO3 addition. [Copyright &y& Elsevier]

Abstract: Quality of pellets is influenced by the nature of ore or concentrate, associated gangue, type and amount of fluxes added and their subsequent treatment to produce pellets. These factors in turn result in the variation of physicochemical properties of the coexisting phases and their distribution during pellet induration. In the present study, effect of pellet basicity and MgO content on the melt formation and microstructure during the induration was examined. Fired pellets with varying basicity (0 to 0.8) and MgO (0 and 1.5%) content were tested for cold strength, reduction degradation index, reducibility, swelling and softening–melting characteristics. Optical microscope studies with image analysis software were carried out to estimate the amount of different phases. SEM-EDS analysis was done to record the chemical analysis of oxide and slag phases. X-ray mapping was also carried out to understand the distribution of CaO, MgO, SiO2 and Al2O3 in different phases. From the results, it was observed that with increasing basicity, RDI and softening–melting characteristics of pellets found to be improved. Addition of MgO to both acid and limestone fluxed pellets considerably reduced their swelling tendency. Improved pellet quality could be attributed to the formation of sufficient amount of silicate melt in basic pellets and high melting point slag in MgO pellets. Limestone fluxed pellets at 0.8 basicity, pyroxenite fluxed pellets at 1.5% MgO and dolomite fluxed pellets at 0.4 basicity & 1.5% MgO exhibited optimum metallurgical properties among all the pellets studied. [Copyright &y& Elsevier]

Abstract: An industrial taconite facility, ‘Plant F’, processed both magnetite and hematite ores during the year. The concentrates were pelletized with a binder, bentonite. Plant personnel believed less bentonite was required to make hematite pellets. Thus, the authors intended to quantify in-plant observations through bench-scale pelletization tests. As-received magnetite and as-received hematite were pelletized and tested for wet-drop number and dry-crush strength. Hematite pellets exceeded industrial minimum wet-drop and dry-crush values of 5 drops and 22N/pellet without bentonite addition, while magnetite pellets exceeded industrial minimum values at a bentonite dose of 6.6kg/t (0.66%). It is known that finer particles increase pellet strength, so additional magnetite was ground to a similar particle size distribution as the as-received hematite. The ground magnetite was pelletized and tested for wet-drop number and dry-crush strength. Wet drop and dry crush values increased after grinding the magnetite concentrate. However, they were significantly less than hematite pellets at similar bentonite doses. Consequently, particle size effects were not the dominant cause for higher strengths in the hematite concentrate. [Copyright &y& Elsevier]

Abstract: Pellet properties are largely governed by the type and amount of oxide and bonding phases formed during induration and their stability during the reduction. In the present study, effect of MgO in the form of pyroxenite on melt formation and microstructure during the induration of hematite pellets was examined. Optical and electron microscope studies with EDS and X-ray mapping were carried to understand the amount and chemistry of different phases formed at different levels of MgO by varying the pyroxenite addition. These pellets were characterized for their strength and swelling index under blast furnace reduction conditions. Based on silicate slag chemistry formed in the fired pellets, microstructure and pellet quality, 5% pyroxenite addition to get 1.5% MgO in pellets found to be optimum flux dosage. Pellets with this optimized chemistry were also found superior to acid pellets in terms of reduction degradation index, reducibility and softening melting characteristics. Formation of magnesioferrite and high melting point slag with low FeO content in the fired pellets could be attributed to the improved performance of pyroxenite pellets. [ABSTRACT FROM AUTHOR]

The article presents a study on the impact of iron ore pellet size on its properties and microstructure. It cites that pellets properties and microstructure depend on raw material mix proportion. Also, reduction and oxidation process occur under various conditions due to pellet size differences. Pellets size from +eight to -12 mm have good strength with lower reduction degradation index (RDI) which are significantly affected by hematite, magnetite, porosity, pore density and size and slag phase.

Abstract: During the re-configuration of their grate-kiln induration system for the firing of iron ore pellets at the Whyalla Steelworks, caused by a change from an earthy hematite to a magnetite ore with considerably less flux, OneSteel commissioned a detailed thermal flow analysis of the design options on the existing cooler in support of the process change. A key objective of this investigation was to decide if and where one might locate baffle walls within the cooler to improve the process and to control the off-gas flows to earlier stages within the process. The thermo-fluid analysis comprised the development of comprehensive three dimensional computational models of gas flow through the cooler coupled with the heat transport and exchange with the cooling pellet bed. The models were implemented within the context of an open source – object based computational fluid dynamics (CFD) simulation software framework. This paper describes the development of the CFD model, its verification and application to evaluating design options to improve the flow control within the cooler. In particular, the analysis considers the role and potential location of above bed baffle walls, cooler stack butterfly lid opening and its exhaust pressure on the flow distribution to the exit flow ducts from the cooler. [Copyright &y& Elsevier]

Abstract: LKAB has started a new pelletizing plant at Malmberget, where the raw material will be a mix of ores from Kiruna and Malmberget. The new plant necessitated an investment in a new grinding section in the concentrator. As usual, the new section has larger mills. It also lacks the wet cobbing stage present in the old sections. Comparing the analysis data from the new grinding section with the old grinding sections it shows that they give similar results. There are slight variations; the older mills produce a steeper final particle size distribution. Also, it appears that the new mills are more efficient, since they have higher calculated grindability indices. To better understand the differences between the sections, and the process implications of the new grinding section, a combination of Particle Texture Analysis (PTA) and the statistical method multivariate data analysis (MVDA) is used. It shows that it is possible to identify and follow systematic changes in the particle morphology of the mill products. Also, that there are differences in process mineralogical aspect between the old and new grinding sections. [Copyright &y& Elsevier]

The rheological aspect of pelletizing fine materials is considered. The elasticity modulus, yield strength and plastic viscosity of the capillary-porous bodies formed are determined. The defining effect of the viscosity of a porous dispersed medium of palletized fine materials on the structural and mechanical parameters of the granules formed is demonstrated. [ABSTRACT FROM AUTHOR]

Pellet plant (4·2 MPta capacity) of JSW Steel Ltd imports iron ore fines from different mines to produce pellets for its Corex and Blast Furnace plants. The pelletisation process involves drying the ore fines to reduce the moisture content to less than 1%, grinding in open circuit ball mills to get required fineness. To produce good quality of pellets certain additives are important and limestone is employed for modifying the pellet basicity. Iron ore fines of -10 mm size and limestone are ground together in a ball mill to get sufficient fineness for the balling process. However, as limestone is harder than iron ore fines the + 100 mesh size limestone particles is higher than required and not all the limestone is fully consumed in the reaction for melt formation. Microstructural studies were conducted under a Leica DMRX polarized microscope at different level fineness (-325# - 56, 58 and 60%) to investigate its effect on the pellet quality. The cold crushing strength of the pellet improved from 203 to 220 kg p-1 with increase in fineness. With increase in percentage of -325# particle size in the ground product RDI of the pellet decreased from 13·8 to 11·9% with increased melt formation from 5 to 9%. With increase in fineness -325# from 56 to 60% the 150 to 500 μm size pores decreased from 51·8 to 13·6%. [ABSTRACT FROM AUTHOR]

Abstract: Chrome ore properties play a critical role in various pelletisation subprocesses (grinding, filtering, pelletisation and sintering) and slight variation in ore properties significantly affect the whole pelletisation process. Three ore samples (sample-A, B and C) were collected from different working faces of a chromite ore mine. Experiments were carried out to find out the difference in grinding (Inherent ore granulometry, ore hardness, ore grindability and friability), pelletisation (green pellet strength, balling time and pellet size) and sintering (pellet strength and porosity) characteristics of these ore samples. Chemical analysis and microscopic studies of the ore samples and pellets were also carried out to identify the cause of difference in pelletisation characteristics of ore samples. These differences were mainly caused by ore genesis process, degree of weathering and mining method. Results of the study show that the ores collected from different working faces of a mine show the significant difference to unstabilize the process with degraded product quality. It was found that blending could be a suitable option to tailor the desired grade feed for steady process efficiency and product quality with proper natural resource utilization. [Copyright &y& Elsevier]

This article focuses on the control of granulation of polydisperse charges and powders by methods of compaction and pelletizing based on rheologic models. Use of disperse media in powder form in the chemical and allied branches of industry frequently fails to conform to technological and ecological requirements. Products with improved properties are formed during granulation of these materials. The products undergoing granulation are polydisperse, and consist of a large number of materials with dissimilar physicochemical properties, which are characterized by a different content of elastic, brittle, plastic, and hygroscopic components, as well as the existence of various special additives. The introduction of additives or binders lowers interparticle friction, and alters the plasticity and cohesiveness of the system, as a result of which a more complete wetting of surface particles by the liquid phase and a reduction in their hardness is ensured, while structural changes occur during solid-phase or other reactions, and new phases are formed.

Depending upon their chemical composition and, to a lesser extent, on their physical properties, iron oxide pellets exhibit varying degrees of sticking tendency during direct reduction at elevated temperatures. For an efficient shaft fumace operation in direct reduction (DR), it is imperative to prevent pellets from sticking to each other and, hence, forming clusters. Coating of pellets with a suitable inorganic material has increasingly been gaining recognition amongst the pellet producers and DR plant operators as an effective method of preventing sticking. In this study, the effect of coating on the sticking of DR-grade pellets with low and high basicity (Midrex and HyL quality pellets, respectively) was investigated. The results show that bauxite and serpentine alone, anal limestone and bentonite in combination are suitable materiais for the prevention of sticking of both types of pellets. [ABSTRACT FROM AUTHOR]

During the last decade the world's iron ore map has been experiencing significant changes; the increasing importance of iron ore pellet production with its associated mining and processing activities exemplifies one of the most important of these changes. Increased demands of the steel industry for iron ore pellets have helped stimulate the development of large and expensive concentrating and pelletizing establishments. Capital requirements and the need for technical cooperation have tended to create a greater symbiotic relationship between the iron ore mining and steel producing industries; steel companies have become increasingly committed financially to pellet producing projects. Competition from pellets is placing a growing strain upon mining regions dependent on direct-shipping ores, especially those regions forced to use underground mining methods. Development of low-grade ores capable of beneficiation has helped in some mining regions to reverse a long-standing trend of decreasing employment and has improved the general economic conditions of those regions. During the coming decades, world iron ore pellet production will continue to increase, and its impact upon the iron mining and steel producing industries will become even more significant, especially in Canada and the United States. [ABSTRACT FROM AUTHOR]

The purpose of this study is to assess the effects that pelletization has had on the iron ore production patterns in the United States between 1950 and 1965. To achieve this, the output of usable tons of iron ore, on a county basis, was mapped in order to describe and analyze the pattern of iron mining over the fifteen-year-period. It was found that pelletization engendered significant geographic and economic change in the domestic iron mining industry. The Lake Superior Region continued as the major domestic producer, followed in order by the Western Region, the Northeastern Region, the Central and Gulf Region, and the Southeastern Region. The importance of many mining districts either decreased (Southeastern Region) or increased (Western, Central, and Gulf regions) subsequent to the development of pelletization. Imports of foreign ore continued to affect some districts, but where pelletization was fully operative, imports had little effect. A major finding of the study was that in regions where pelletization was employed, the average increase in value-per-ton of iron ore over the fifteen-year-period increased proportionately more than for areas where ore was not pelletized. In 1965, areas where pelletization occurred recorded the highest values per ton of iron ore. [ABSTRACT FROM AUTHOR]

The roasting in air of pellets consisting of copper–iron sulphides and limestone and activated limestone has been investigated to explore the possibility of developing a metal production process that eliminates sulphur dioxide gas emissions. The effects of pellet porosity, sulphide: limestone ratio, pellet sizes and temperature on reaction kinetics were investigated. Thermogravimetry was carried out under air atmosphere. The weight gain of pelletized samples was used to identify and study the phases present in the reaction products.The experimental results indicated that at 500 °C using activated limestone, a completely reacted pellet can be produced in about 50 min with very low emissions of sulphur dioxide (more than 95% of sulphur capture). [Copyright &y& Elsevier]

The contents of Fe and SiO2 in ferric bauxite are much higher than that in regular bauxite, and the leaching yield of Al2O3 from ferric bauxite cannot reach the general level of ordinary ores, even under optimal conditions. This paper introduces a pretreatment method to enhance sintering before leaching. First, mixing followed by grinding was found to be more efficient than grinding followed by mixing as a pretreatment method by forming a directional coating structure of CaCO3 on the SiO2 surface. Second, leaching yields increased grinding fineness because CaCO3 grain uniformity could be improved with the latter method. Finally, the leaching yields were increased by pulp consistency under certain conditions, as evidenced by improvements in CaCO3 uniformity, bulk density, and Al2O3 grain size, which parameters were beneficial to enhance leaching. The leaching yield of Al2O3 was increased from 75.2% to 87.15% by using the proposed mixing–grinding method with the leaching agent of water. [ABSTRACT FROM AUTHOR]