Sinter Blend Research Articles

Application of the Fuller–Thompson equation in sinter blend design to increase sinter productivity

Sintering is an important phase of the iron-making chain, as it allows the usage of finer iron ore particles in the blast furnace whilst still maintaining furnace performance. An on-going challenge for sinter plants is to obtain higher productivity from their sinter blends, or maintain sinter productivity whilst using more financially attractive iron ores. One of the most effective means to reduced blend cost is to use a higher proportion of concentrated iron ores in the blend. The key characteristic of concentrated ores is that they have a finer particle size distribution (PSD) than traditional sinter feeds and are widely known to negatively impact sinter bed permeability and sinter productivity. In this study, various iron ore blends were used to demonstrate the effect that the PSD of the sinter blend has on granulation and subsequent sintering process parameters during laboratory-scale sintering. Particular focus was applied to the impact of the PSD of the layering material in blend (−0.5 mm). Cold bed superficial gas velocity (SGV) was correlated to the spread of the PSD within the layers around granule nuclei. Widening the PSD spread within the layer increased cold SGV due to a narrowing in the spread of the granule size distribution (GSD) and increase in mean granule diameter. The Fuller–Thompson (FT) blend exhibited increased SGV during sintering (hot SGV) which led to shorter sintering times. This was a result of an enhanced ‘hot SGV efficiency’ (a measure for the ratio of hot SGV to cold SGV) over what was anticipated based on the trend with mean granule diameter. Complete industrial blends were compared with blends designed to the FT equation at varying proportions of layering particles in the blends (−0.5 mm). At equal proportions of layering particles in the blends, the FT blends exhibited increased cold and hot SGV by up to 20% and 25%, respectively, and led to a maximum 10% decrease in sintering time. Further, blends designed to the FT equation enabled the incorporation of 4 wt-% more layering particles and still exhibited similar cold SGV, hot SGV and sintering times to the industrial blends.

Effect of ore types on high temperature sintering characteristics of iron ore fines and concentrate

Sinter quality (strength and reducibility) plays an important role in reducing the GHG emissions from the blast furnace ironmaking process and is significantly influenced by the reactions occurring in the sintering bed. Formation and fluidity of the initial sinter melt from adhering fines and its interactions with coarse nucleus particles are the key sintering reactions. Hence understanding of these high temperature characteristics of iron ore is urgently needed in order to produce strong and reducible sinter and optimise resource utilisation. In the present study, laboratory scale sintering tests were carried out to examine the effect of adhering fines and nucleus particles from various ores on the characteristics of initial sinter melt formation, fluidity, as well as penetration and assimilation. The formation ability and fluidity of the initial melts from various adhering fines were quite different, and various iron ore fines required distinct CaO contents to form the melt and spread out. The ore type of adhering fines and substrates affected the penetration and assimilation ability of the initial melt, but a good formation ability and fluidity of initial melt was the basis of good penetration and assimilation ability. Based on the micro and macro sinter structure, the high temperature characteristics were further related to the sinter quality and sintering performance. This information is expected to provide excellent tools in formulating and optimising future low cost and low emission sinter blends.

Research on the Quality Improvement and Consumption Reduction of Iron Ore Agglomeration Based on Optimization

In order to increase agglomeration production and improve its quality while reducing energy consumption, a new intelligent blending method has been established at Ansteel to optimize its sinter blends. The statistical model of the ore blending results shows that (1) a blending ratio of 47.2% Ore A and 52.8% Ore C corresponded to the best sinter yield of 72.44%. (2) From the viewpoint of sinter reducibility, sinter basicity should not be less than 1.98 when the proportion of Ore A in the blend is more than 35%. Due to the low mixing efficiency of disc pelletizers, Ansteel has therefore gone through a massive technical transformation at Sinter Plant 3 to replace its 16 existing disc pelletizers with one drum granulator. Since the installation of the drum granulator, the standard deviation has decreased from 1.517 to 0.7332 for total Fe (T.Fe) and from 0.146 to 0.0956 for basicity. In the case of the drum granulator, the standard deviation for sinter T.Fe and basicity were 0.6926 and 0.05449, respectively, as compared to 0.8902 and 0.2033 for the disc pelletizers. In addition, a single lattice method is proposed to optimize the particle-size distribution of the coke breeze to further improve sinter quality and reduce fuel consumption. The lattice method indicated that the optimum coke breeze to achieve maximum sinter tumble strength should consist of approximately 57.20%: −1 mm, 25.63%: 1–3 mm, 11.17%: 3–5 mm, and 6.00%: >5 mm particles. Given the international trend of increasing bed depth, Ansteel has successfully achieved a bed height of 1050 mm or more under its blend conditions, which typically contain 75% concentrates. Finally, some new iron ore agglomerations research is discussed.

Liquid Formation in Sinters and Its Correlation with Softening Behaviour

Modern blast furnaces with extensive operational volume demand better-quality iron agglomerates as feed for stable operation. Sinter is the principal feed used in blast furnaces across Asia. Liquid generated during the sintering process plays an essential role in the coalescence of the sinter blend and in sinter quality. Therefore, an estimation of liquid properties at peak bed conditions during sintering helps manage sintering liquid behaviour, leading to better control of final sinter properties. In this study, three different iron sinters were reheated to sinter bed conditions, followed by quenching. Electron probe X-ray microanalysis (EPMA) was used to identify the resultant phases and quantify their chemical compositions. The impact of sinter bulk compositions was analysed, especially on sintering liquid properties. Furthermore, experiments were conducted to study the softening and melting behaviour of the sinters, and the cohesive range of the sinters was identified. Finally, the effect of the sinter bulk compositions on sintering liquid properties and softening behaviour is detailed.

Improving the sinter productivity with increased specular iron ore in sinter blend

Specular iron ores are medium grade iron ores suitable for the use in agglomeration process. However, due to their hard texture, undesirable particle size and shape, poor assimilation performance and low reactivity at high temperature, its uses in agglomeration is very limited and restricted to almost 3-10% at most of the plants. In the present study, the effect of specular iron ore on sintering performance and sinter qualities are examined. It was observed that an increased proportion of specular iron ore in sinter blend showed poor sintering performance in both laboratory scale studies and plant scale trials. In the present work, the effect of blending of specular iron ore with goethite iron ore in sinter mix on sintering performance was examined and an optimum iron ore blend ratio for sustainable performance and quality was proposed. To increase the specular iron ore usage in sintering, goethitic iron ore up to 30% was introduced in sinter blend to overcome the deteriorating nature of specular iron ore. The goethite iron ore contains chemically bonded water which gets removed at higher temperatures (300-500?C) during sintering. The evaporated water gets cooled at lower bed and condenses which retards the air flow during sintering process and thus the combustion zone stays for longer time allowing better melt assimilation and sinter qualities. The poor melt assimilation of specularite is thus countered in presence of goethite iron ore. Having better reactive and hydrophilic nature of goethite iron ore, nullifying or reducing the ill effect of poor reactive and hydrophobic characteristics of specular iron ore during granulation and sintering process. Therefore, the blended specular and goethite iron ore resulted in improved sintering rate and consequently improved sinter productivity. The present work proposed usage of up to 30% of specular iron ore when blended with goethite iron ore in sinter making.

Demir Cevheri Sinter RUL Test Sonuçlarının Analizi

The sintering process brings the powdered iron ores to the desired particle size, strength and gas permeability for the blast furnace. During sintering, important events such as bonding between particles, size change and coarsening of the microstructure take place. RUL (Reduction Under Load) test is performed to determine the metallurgical properties of the sintered sample. Statistical process control techniques are used for iron and steel plants in which data are measured for certain periods to increase physical, chemical and reducibility properties of sinter production. Thus, when some important advantages are provided in terms of control and applicability. In this study, static and dynamic test low-temperature reduction disintegration and reduction under the load of the samples taken out regularly from sinter samples were investigated to determine the capability of the process. For each parameter, X-R control charts using the moving range method were drawn. Thereby, deviations of lower and upper limit values were determined. It was concluded that the amount and grade of raw ore in the Sinter Blend should be fixed by using appropriate amounts.

Phase Development in the Sintering of a Hematite–Ilmenite Ore Blend

The use of low-grade iron ores has attracted a lot of interest where fines from these ores are sintered to improve their strength. Ti-containing ores are one of the abundantly available iron ores of low-grade. The sintering of the hematite–ilmenite ore blends has several challenges, which include the formation of perovskite. The sintering behavior of a hematite–ilmenite ore sinter blend was investigated in 75 vol% N2, 24 vol% CO2, and 1 vol% CO in the temperature range of 1373 to 1523 K. Phase development and distribution of metallic elements were investigated by x-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and electron probe microanalysis (EPMA). The addition of ilmenite ore to hematite ore increased the temperature of melt formation. More titanium (Ti) was distributed in the glass phase with increasing temperature. Morphological change showed that the amount of sinter-bonding phase generated was low, below 1473 K. Weak sinter bonding strength might be caused by the presence of Ti in the glass phase at high temperature. This might affect the fracture toughness of the glass phase.

Effects of Ilmenite Ore on Phase Development of Hematite Ore Sinter

The effects of adding 5 to 25 wt pct of ilmenite ore to hematite ore sinter were investigated employing a horizontal tube furnace to clarify the phase development. The temperature was raised nonisothermally at 10 °C/min to 1150 °C in an Ar atmosphere. When the target temperature was reached, 1 L/min of air was injected to allow combustion of the carbon in the pellets. The development of the phases in the sinters was studied using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and electron probe microanalysis (EPMA). The tumbler index (TI) decreased with the increase in ilmenite addition up to 20 wt pct, which increases TiO2 (s) and Fe3O4 (s) content in the sinter blends. Addition of more than 2 wt pct TiO2 (s) to the sinter blends resulted in the formation of perovskite (CaO·TiO2), which affected the development of bonding phases. These changes deteriorated the reduction degradation index (RDI). The estimated melt formation temperature of the sinter blends increased with ilmenite addition up to 15 wt pct and decreased thereafter. An attempt was made to predict the development of phases in the ternary phase diagram of CaO-Fe2O3-TiO2. The reduction behavior of the sinter blends was affected by the type of the bonding phase.

A STUDY ON THE EXAMINATION OF THE SINTER METALOGRAPHIC STRUCTURE

Sintering process is carried out domestic and imported iron ore powders, fluxes (limestone, dolomite etc.), coke dust, metallurgical recycling powders and slag forming agents. The purpose of the sintering process is to produce a charging material with suitable thermal, mechanical, physical and chemical properties that can be fed into the blast furnace. Nowadays, in order to obtain process and operating parameters that will work with the best sinter quality, extensive researches have been made by iron and steel industry. The sinter quality parameters followed by the sinter blend loaded on the sinter strand and then granulated were examined. In the sintering process, the temperature rises to 1450 oC, partially melting between the sinter grains and a series of reactions take place in the sinter matrix to be charged into the blast furnace to produce liquid crude iron. Many different approaches have been used to estimate sinter quality, to explain the effects of iron ore properties and process variables on sintering mechanisms, and to characterize sinter mineralogy of iron ore. We can obtain chemical analysis of the phases by scanning electron microscopy (SEM) technique, but full consistency with images is not always possible and especially SFCA (silico-ferrite of calcium and aluminium) and SFCA-I phases are difficult to distinguish from each other and future studies are required in this field. The mineralogy and microstructure of the sinter plays an important role in determining the physical and metallurgical properties of the iron ore sinter. Mineralogical characterization of sinter phases; it is a complementary tool to conventional physical and metallurgical tests applied to iron ore sinter to evaluate and estimate sinter quality. Measurement techniques used in this study; optical image analysis and X-ray diffraction (XRD), scanning electron microscopy (SEM), energy distribution spectroscopy (EDS), the results from raw data converted to autoquan format will be explained on the new studies on the interpretation of the Rietveld system. Depending on the measurement objectives of each technique, the quantification of the crystal phases, the relationship between the measurement results, the chemical composition of the phases and the relations between the minerals, as well as their advantages and disadvantages will be explained.

Manganese Sinter Production with Wood Biomass Application

A large amount of finely dispersed manganese ore left after benefication operations or blown out from the furnaces is unsuitable for direct use in electric furnaces and blast furnaces, therefore it is necessary to granulate it in order to have the efficient use of its fine ore particles in metallurgy. To make our research more of practical use, we found it is reasonable not only work over manganese fines sintering but also to attempt mitigating the negative effect on the environment produced by the further sintering and apply the biofuel within the total fuel mass. Under laboratory conditions, the studies have been carried out with the objective to obtain manganese sinter, in which wood biomass is applied, namely initial and pre-pyrolyzed, at temperatures of 673, 873, 1073 and 1273 K. The amount of biofuel in the sinter blend was 25 wt.%. It has been established that the biomass use causes the decrease in the specific capacity of the sintering plant. However, for the efficient manganese ores sintering process, the biofuel of high pyrolysis temperature of 1273 K is required. To achieve the specific capacity and the yield to be as high as those when coke breeze is only used, the amount of the biofuel for manganese ore sintering should be less than 25 wt.% of the solid fuel. Additionally, it has been revealed that the further increase in the biofuel ratio in the total fuel amount is possible on condition that its reactivity is decreased, or larger particles of the biofuel are used.

Effect of pre-briquetting on the granulation of sinter mixture containing high proportion of specularite concentrate

Specularite concentrate assays high iron grade and little impurities, but has been blended in sinter mixtures only with lower ratio because of its poor granulating performance. Nearly all of existing methods for improving granulation of sinter mixtures comprising specularite concentrate all need finely grinding of it, which means higher energy consumption and production cost. In this paper, granulating characteristics of specularite concentrate were investigated and the pre-briquetting process was employed to improve granulation of sintering mixture containing specularite concentrate. The experimental results show that granulating efficiency was debased obviously when the ratio of specularite fines in sinter blends exceeded 24%. Most specularite particles distributed in the fine granules of −1 mm and adversely affected the permeability of sinter bed. In granulation with specularite concentrate pre-briquetted, the average granule size and permeability of sinter bed increased by 11.17% and 12.69% respectively when the sinter blend contained 36% of specularite concentrate, compared with that in traditional granulation. The pre-briquetting process made the specularite concentrate into independent quasi particles preliminarily, thus changed granulation model and distribution of specularite particles in sinter bed and improved the granulation of sinter mixture containing high ratio of specularite concentrate.

Mineralogical quantification of iron ore sinter

The mineralogy and microstructure of sinter play an important role in determining the physical and metallurgical properties of iron ore sinter. Characterisation of sinter phases is, therefore, a cost-effective and complementary tool to conventional physical and metallurgical testing of iron ore sinter in evaluating and predicting sinter quality. Over the years, CSIRO (Commonwealth Scientific and Industrial Research Organisation) has developed a scheme for characterising iron ore sinter which classifies primary sinter phases, such as un-reacted and partially reacted haematite, magnetite and remnant fluxes, and secondary phases including silico-ferrite of calcium and aluminium (SFCA), secondary haematite and magnetite, glass and larnite. Quantification of these phases has traditionally been carried out by manual point counting under a petrographic microscope. However, new technologies based on automated optical image analysis, quantitative X-ray diffraction and scanning electron microscopy are now available for evaluation. In this study, two sinter samples of varying chemistry were prepared and characterised using both point counting and automated optical image analysis. Quantification of sinter phases is a complementary tool for comparing the physical properties of sinter obtained from various sinter blends, and sinter phase quantification results can be used for comparing pot-grate sinter with different metallurgical properties.

Fundamental nucleus assimilation behaviour of haematite and goethite containing ores in iron ore sintering

The CSIRO laboratory-scale assimilation test is carried out by embedding ore particles into a fluxed matrix of known sinter blend composition. Samples are fired in a tube furnace under controlled conditions simulating the actual sintering process. The aim is to isolate and evaluate the nucleus behaviour of an individual blend component. Measured cross-sections of the resulting fired samples provide a semi-quantitative measure of reactivity, while accompanying photomicrographs allow a qualitative assessment of assimilation properties. Nucleus particles were selected from haematite, haematite-goethite and goethite ores and embedded in a simulated plant sinter matrix. Drilled core particles of two sizes were tested at fixed temperatures simulating low temperature (<1300°C) and high temperature (>1300°C) sintering conditions. The resulting assimilation properties are compared and discussed as a function of particle size, temperature and ore/sinter mineralogy. The implications for the contribution of each component in the prediction of blend sinter quality are also discussed.

Effect of Addition of Mill Scale on Sintering of Iron Ores

Iron-rich (65 to 70 pct total Fe) mill scale generated during processing by steel mills can be recycled by using it as a ferrous raw material in the sintering process. The effect of mill scale addition on the phase formation of sintered specimens from an industrial sinter blend containing 0 to 15 wt pct mill scale was examined, and the mineral phases formed during sintering under various conditions (T = 1523 K to 1598 K [1250 °C to 1325 °C] and gas compositions of pO2 = 0.5, 5 and 21 kPa) were quantitatively measured. For samples sintered in air (pO2 = 21 kPa), there was negligible effect of mill scale addition on the phases formed. The oxidation of the mill scale was complete, and phases such as Silico-Ferrite of Calcium and Aluminum (SFCA), SFCA-I, and hematite dominated. Under lower oxygen partial pressures (pO2 = 0.5 or 5 kPa), and throughout the temperature range examined, the mill scale was converted to magnetite, with the extent of reaction controlled by the hematite-magnetite conversion kinetics. When sintered in the gas mixture with pO2 = 5 kPa, an increase in the mill scale content from 0 to 15 wt pct resulted in a decrease of hematite and total SFCA phases and a corresponding increase in the amount of magnetite which formed. The oxidation of wustite in mill scale to magnetite decreased the local partial pressure of O2 and increased sintering temperature, which promoted the decomposition of hematite.

Improvement of sintering characteristics by selective granulation of high Al2O3 iron ores and ultrafine iron ores

The worldwide steel companies are expected to use low grade iron ores such as pisolitic iron ores, high Al2O3 iron ores and ultrafine iron ores etc. in their sinter blends due to the depletion of high grade iron ores or for the economic reason. This study investigated the methods for improving sintering characteristics without deteriorating sintering productivity and sinter quality by blending mini-pellets comprising high Al2O3 pisolitic iron ores and ultrafine iron ores containing low alumina. The results showed that the blending of iron ore mini-pellets produced by selective granulation is an effective way to improve sintering productivity and sinter quality without increasing the Al2O3 content in sinter as well as to effectively utilise high Al2O3 iron ores and ultrafine iron ores in the sintering process.

Behavior of New Zealand Ironsand During Iron Ore Sintering

A New Zealand ironsand sample was characterized by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy, qualitative and quantitative X-ray diffraction, and electron probe microanalysis. The titanomagnetite-rich ironsand was added into an industrial sinter blend in the proportion of 5 wt pct, and the mixture was uniaxially pressed into cylindrical tablets and sintered in a tube furnace under flowing gas with various oxygen potentials and temperatures to develop knowledge and understanding of the behavior of titanium during sintering. An industrial sinter with the addition of 3 wt pct ironsand was also examined. Both the laboratory and industrial sinters were characterized by optical and SEM. Various morphologies of relict ironsand particles were present in the industrial sinter due to the heterogeneity of sintering conditions, which could be well simulated by the bench-scale sintering experiments. The assimilation of ironsand during sintering in a reducing atmosphere started with the diffusion of calcium into the lattice of the ironsand matrix, and a reaction zone was formed near the boundary within individual ironsand particles where a perovskite phase was generated. With increasing sintering temperature, in a reducing atmosphere, ironsand particles underwent further assimilation and most of the titanium moved from the ironsand particles into a glass phase. In comparison, more titanium remained in the original ironsand particles when sintered in air. Ironsand particles are more resistant to assimilation in an oxidizing atmosphere.

Steelmaking slag beneficiation by magnetic separator and impacts on sinter quality

Basic oxygen furnaces (BOF) slag is the main problem at all iron and steel factories. About more than 6 million tons/year of BOF slag has been accumulated from the waste stockyards in Turkey. Dumps slags can be revaluated by a processing technology which makes it possible to obtain products that meet the requirements of sintering and blast furnace production. The slags with particle size of -10 mm were enriched by the magnetic separator resulting and increase in Fe grade from 18% to 33%. The use of BOF slag in sinter blend provided additional Mn, CaO, MgO and introduced a good solution to environmental problems.

Study of Sintering Blending Based on Swarm Intelligence Optimization Algorithm

The sintering blending is a complex nonlinear optimization problem. The traditional single algorithm can not meet the requirement of good quality of sinter and lowest costs well. So, a hybrid optimization method of particle swarm and ant colony algorithm was proposed. The method gives full play to the global convergence of particle swarm optimization algorithm, takes it as a preliminary search, then use the positive feedback mechanism of ant colony algorithm for the exact solution, to make these two algorithms to reach a complementary, in order to get a rapid exact solution. The simulation results show that the proposed hybrid algorithm has fast convergence and high accuracy, which can effectively reduce the sintering cost.

Application of Intelligent Integrated Optimization System for Raw Material Proportioning in Lead–Zinc Sintering Blending Process

The blending process as the first working procedure in lead–zinc sintering processes (LZSP) is a key step to guarantee the quality of products in the lead–zinc sintering production. This paper pres...

Qualitative and Quantitative Synthetic Methodology for Blending Optimization in Lead-zinc Sintering

To deal with the problem of high cost and low accuracy existed in conventional methods for the lead-zinc sintering blending, a qualitative and quantitative synthetic methodology for sintering blending optimization is presented in this paper. First, two prediction models are built based on a process neural network and the improved grey system theory. Next, these two models are integrated into one prediction model by using the concept of entropy. It guarantees the prediction precision of the Pb and Zn components in the agglomerate. Then, a blending optimization model is established to minimize the costs. Finally, the component ratios are optimized by using the expert reasoning strategy and an integrated synthesis methodology.