Application of bentopolymer composition as a binder to improve metallurgical properties of iron ore pellets

Effect of adding limestone on the metallurgical properties of iron ore pellets

Currently, the most common fluxing additive to pellets is dolomite CaCO3 · MgCO3, in which the magnesium oxide content can form from 17 to 22%. If the magnesium oxide in pellets increases, then it is necessary to increase the dolomite dosage. Thus, the iron content decreases, which entails a decrease in yield ratio at subsequent processing. One of the fluxes containing magnesium is brucite. Compared with dolomite, magnesium oxide content in pure brucite is more than 3 times higher. The basis of Flumag M flux is brucite. The magnesium oxide content in it is not less than 55%. The paper presents a series of laboratory studies on the Flumag M flux dosage effects on the pelletizing ability of the charge and such properties of iron ore pellets as compressive, impact and abrasion strength. We have made the tests on raw and fired pellets with Flumag M flux. The comparative analysis of strength properties of the pellets obtained with the use of Flumag M and limestone was performed. The binder content, bentonite and magnetite concentrate, for all experiments remained unchanged. The experiment results indicate that Flumag M does not interfere with charge pelletizing ability. The strength of raw pellets for discharge and compression with Flumag M flux has small deviations from the pellets with the addition of limestone. Roasted pellets with the addition of Flumag M flux have higher strength than ones with limestone. The higher difference in strength properties is observed at the flux content of 2%.

Currently, the most common fluxing additive to pellets is d mite CaCO 3 ·MgCO 3 , in which the content of magnesium oxide can be from 17 to 22 %. But if it is necessary to increase magnesium oxide in pellets, it is necessary to increase the dosage of dolomite, and thus the iron content decreases, which entails a decrease in yield ratio at subsequent processing. One of the fluxes containing magnesium is brucite. Compared with dolomite, magnesium oxide content in pure brucite is more than 3 times higher. The basis of FLUMAG M flux is brucite. The content of magnesium oxide in it is not less than 55 %. The paper presents series of laboratory studies on the effect of FLUMAG M flux dosage on pelletizing ability of the charge and such properties of iron ore pellets as compressive, impact and abrasion strength. We have made the tests on raw and fired pellets with FLUMAG M flux. The comparative analysis of strength properties of the pellets obtained with the use of FLUMAG M and limestone was performed. Content of the binder – bentonite and magnetite concentrate for all experiments remained unchanged. The results of these experiments indicate that FLUMAG M does not interfere with charge pelletizing ability. The strength of raw pellets for discharge and compression with FLUMAG M flux has small deviations from the pellets with the addition of limestone. Roasted pellets with the addition of FLUMAG M flux have higher strength than ones with limestone. The higher difference in strength properties is observed at the flux content of 2 %.

Objective: to analyze and determine the influence of bentonite clays of different deposits and exchange ionic complexes on the metallurgical properties of iron ore pellets. Methods: performing rheological studies of bentonite clay samples and their chemical analysis, electron microscopic studies of samples. To assess the metallurgical characteristics of the pellets obtained, the moisture of the pellets, the compressive strength of the wet and dry pellets, the number of dumpings without destroying the wet pellets, and the temperature of the «shock» have been determined. Results: laboratory tests were conducted to determine the suitability of bentonite clays of different mineralogical composition and exchange ion complex for the production of pellets. Tests have shown that the impact resistance and compression resistance of raw pellets at a slightly increased specific consumption of bentonite Cherkasy alkaline-earth bentonite does not concede to the same properties of pellets with the use as a binder alkaline Saryugyhsky bentonite. It is demonstrated that to ensure good quality of raw pellets, an auspicious variety of clays of the Cherkasy deposit are clays of the IV layer, which are a natural mixture of alkaline-earth bentonite of the II layer and palygorskite (III layer). Tests of composite mixtures of clays IV with II and II with III layers showed that the quality of raw pellets with Cherkassky bentonite is slightly worse than with Sarygyuhsky, however, the absolute values of their indicators satisfy the industry requirements. Comparative tests of pelletizing of charges with different humidity and with the addition of 0.5% alkaline bentonite and a mixture of clays of the IV and II layers of the Cherkassky deposit have been carried out. It is shown that with increasing humidity in granules with both types of binders, the dynamic strength, porosity and temperature of the “impact” of granules increase with a minimum difference in the absolute values of indicators with different binders. To objectively confirm the possibility of using alkaline-earth bentonite of the Cherkassky deposit (II-III-IV layers) in the production of pellets, it is necessary to conduct comparative industrial tests at a pelletizing plant (for example, SevGOK), using a concentrate with the in-creased hardness of industrial water. Scientific novelty: the influence of alkaline bentonite replacement in charge for pellet production with alkaline earth, paligorskite clays and mixtures of their forms has been studied. The comparative influence of moisture content of raw pellets on their porosity and strength characteristics with alkaline and alkaline earth bentonites in the charge was studied. Practical significance: using the properties of raw, dry and calcined pellets as an example, the possibility of using less scarce and expensive local bentonite clays instead of expensive exported alkaline clays without impairing the production technology and characteristics of the pellets is shown.

Iron ore pellets are used as an intermediate product in the production of steel. Their size of approximately 10 mm diameter combines ease of handling with the ability to control air flow and heat distribution in a blast furnace. Previous studies have investigated the thermal properties of iron ore pellets over from 30 to 800°C, i.e. over a temperature range relevant for blast furnaces.1) It was found that the thermal conductivity and diffusivity decreases with increasing temperature, and that the specific heat peaks at around 680°C due to a phase transition. Heat and mass transfer of individual pellets exposed to a stream of air has been subject to computational fluid dynamics simulations.2) In earlier energy transfer measurements, the diffusivity of individual iron ore pellets was found to range between 2.9 and 3.6×10–7 m2 s–1 over a temperature range from room temperature to 680°C.3) This study focuses on heat transfer over a temperature range commonly observed during transport of iron ore pellets. Specifically, KPBO pellets of Luossavaara Kiirunavaara Aktiebolag (LKAB) are commonly shipped shortly after production, i.e. while warm (30°C). However, some batches may have been stored outside at sub-freezing temperatures commonly observed to be as low as –30°C. Here, heat transfer between a cold layer of pellets underlying a warm layer is measured and compared with heat transfer simulations. Such layering may be observed in storage silos. Previous measurements of thermal properties of individual pellets are not directly applicable to heat transport though a bed of pellets. At atmospheric pressure, effective thermal conduction through granular media combines the effects of conduction through solid particles, conduction through gas, advective heat transfer through the gas, and radiative heat transfer between solid particles.4,5) The significance of individual contributions depends on pore size, absolute temperature and material properties, and varies with air pressure and temperature.5) This work focuses on the question whether vertical heat transfer through a bed of KPBO pellets can be described as a homogenous material with temperature-independent thermal properties. Laboratory experiments were performed and compared with one-dimensional heat transfer simulations.

The paper investigates the effect of high-temperature roasting and cooling modes of roasted iron ore pellets on their strength and porosity. These characteristics depend on the initial iron ore raw materials properties, the parameters of the raw pellets, the firing temperature, the holding time at this temperature, the heating and cooling rate, and take into account the change in these indicators in connection with the chemical and mineralogical compositions of the pellets. It has been established that the strength of iron ore pellets obtained at the optimum firing temperature depends on the characteristics of the initial finely dispersed iron ore raw material. The relationship between the content of draw rock and the strength of calcined pellets has been revealed. A significant influence of the raw pellets porosity on the strength of the calcined pellets was found. It is shown that the crushing strength of pellets cooled in air is higher than the strength of pellets cooled with water, and a decrease in the final cooling temperature leads to an increase in the strength of the pellets. It is substantiated that the heating rate should not exceed the rate of gas diffusion, and with a decrease in the size of finely dispersed iron ore raw materials, the shrinkage of the pellet layer increases during heating. It is shown that shrinkage appears at temperatures lower than the optimal calcining temperature and insignificantly affects the strength of the pellets. The results obtained can be used to substantiate resource-and-energy efficient operating modes of horizontal-grate machines in ferrous metallurgy.

Iron ore pellets are largely characterized by inherent physical and chemical properties of ore as well as pelletizing conditions including induration time, induration temperature, etc. These parameters essentially vary with types of ores. The production of high-quality pellets from hematite ore is challenging because of high level of fineness (Blaine number) and induration temperature requirement, ensuring severe degradation property during reduction, etc. In this work, the effect of Blaine number (Blaine fineness: expressed as the specific surface area of fines) on the pellets’ properties was studied. The paper presents the effect of Blaine number on green and dry strength, cold crushing strength, reducibility index, reduction degradation index, swelling index, apparent porosity, optical micro structure, etc. of the high alumina hematite ore pellets. The results showed improved properties of iron ore pellets at an optimum Blaine number (2150 cm2/g) but, reduction degradation index was found to be very poor for the given ore. Further investigation showed that when MgO containing flux viz. pyroxenite was added, the reduction degradation index and swelling index of the pellets were improved for identical Blaine number and other optimized process parameters.

As an important raw material in ferrous metallurgy, the chemical indexes and metallurgical properties of iron ore pellets play a decisive role in ensuring the quality of iron and steel products. This article expounds the significance of burden process for pellet quality control from the perspectives of pellet production process as well as application of automation system.

The production of magnesia pellets is developing in mining enterprises, especially in the context of tightening environmental standards and a decrease in sinter production. In the course of the work, it was determined that from the peculiarities of pellet structure formation, the dolomite influence is manifested in a change in both the thermal conditions of firing (the endothermic effect increases with the decomposition of carbonates) and the mineral composition of the fired product. From the point of view of metallurgical properties, MgO contributes to an increase in the strength upon reduction, as well as an increase in carbonates content in the charge leads to an increase in porosity and reducibility. In general, the use of dolomite makes it possible to improve the quality of iron ore pellets by increasing their metallurgical properties.

Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties exerted the major effect on pellet behavior and final pellet quality. The absorbed moisture content of pellets prepared without binder, bentonite-added pellets, and molasses-added pellets were in the range of 7.72%–9.95%, 9.62%–10.84%, and 6.14%−6.69%, respectively. The wet pellet compressive strength of molasses-added pellets (43–230 N/pellet) was superior to that of bentonite-added pellets (9.47–11.92 N/pellet). The compressive strength of dried molasses-modified pellets increased to 222–394 N/pellet, which is currently the highest value achieved for dried pellets.

ABSTRACTBrazil 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.

Monitor and Control Concept of Metallurgical Properties of Iron Ore Pellets in Existing Process

Analysis of the Firing Effect on the Metallurgical Properties of Iron Ore Pellets

This paper is based on project work carried out in partial fulfillment of a BEng (Metallurgical Engineering) degree at the University of Pretoria.

Effect of Blaine Number on the Physical and Mechanical Properties of Iron Ore Pellets