Reduction Degradation Index Research Articles

Effect of Al2O3 on the sintering process and the metallurgical performance of sinter

ABSTRACT The trend to process iron ore with increasing Al2O3 content has affected the performance of sinter and blast furnace operations. Formation of the primary melts and phase properties such as morphology and reducibility of the iron ore could be easily influenced by the Al2O3 content. In this paper, the effect of the Al2O3 content in the sinter samples, which range from 1.49 to 3.24 wt-% with a basicity of 2.0, MgO/Al2O3 ratio of 1.05, on the sintering process and the metallurgical performance were studied through a sinter pot experiment and a reduction experiment. The results show that an increase in the Al2O3 content deteriorated the sintering index, and the yield and tumble index decreased by 7.61% and 12.02%, respectively. The sintering index was relatively stable when the Al2O3 content was between 2.10 and 2.95 wt-%. Low-reduction columnar silico-ferrite of calcium and aluminum increased with the increasing Al2O3 content, hindered the reduction index of the sinter. The low-temperature reduction degradation index change was only around 2%, due to the higher MgO content of the sinter promoting magnetite formation.

Occurrence Form of Potassium Vapor in Sinter and Its Effect on Reduction Degradation Indexes

In this study, potassium vapor was prepared by using potassium carbonate (K2CO3) and activated carbon (C) reagents to simulate the actual situation of adsorbing potassium vapor from the sinter in the blast furnace. The potassium-rich sinter was characterized by X-ray diffraction (XRD), flame atomic absorption spectrometry (FAAS), and scanning electron microscopy (SEM-EDS). The effects of potassium vapor content on the enrichment ratio, adsorption rate, and low-temperature reduction degradation index (RDI+3.15mm) of sinter have been studied. The results show that with the increase of potassium vapor content, the enrichment ratio of potassium in the sinter increases, and the adsorption rate of potassium in the sinter increases first and then decreases, which was opposite to the trend of the low-temperature reductive degradation index of the sinter. When the potassium vapor content was increased by 50 times, the enrichment ratio and low-temperature reduction powder of the sinter are the highest, which were 2576% and 85.3%, respectively, and the adsorption rate of the sinter was the lowest, which is 51.5%. Meanwhile, potassium vapor changes from physical adsorption K2CO3 to chemical adsorption KFeO2 as the potassium vapor content increases. In addition, the transformation of the occurrence form of potassium vapor in the sinter during the rising process has also been clarified.

Utilization of micro-fines in sinter making and its implications on bed permeability and sinter quality

ABSTRACT Exploiting low-grade resources and raw material fines is a challenge for metallurgists developing new technologies. Iron-bearing and carbonaceous by-products are generated by ironmaking and steelmaking units and fed into the sinter plant. These by-products, which have varying proportions of ultra-fines, balling properties, moisture retention capacities, and so on, have a significant impact on sinter quality when used in sinter green mixtures. This study investigates the use of micro-fines and how it affects sinter quality while keeping operational factors such as moisture addition, balling index, and bed permeability in mind. In addition, the ideal moisture addition is investigated using higher micro-fines bearing dusts/sludges of various iron-bearing materials. The presence of columnar SFCA (Silico-ferrite of Calcium and Aluminium) is revealed by microscopic examination of the sinter produced with higher micro fines and good permeability, which improves the Reduction Degradation Index. It was also demonstrated that using more micro-fines in the blend and maintaining consistent moisture addition reduced the amount of return sinter produced.

Microindentation testing as a means of predicting lump iron ore physical properties

ABSTRACT This study utilised Vickers and Knoop microindentation testing to characterise the physical and chemical properties of a range of iron ore material types and lump ore samples. Lump ore composite microhardness (CH) and fracture toughness (CFT) correlated best with Tumble and Abrasion Indices and with Fe-total, Al2O3 and LOI contents. General trends were evident between CH/CFT and other common metallurgical indices, e.g. higher Reduction Degradation Index with lower CH. Correlations between ore group CH/CFT and the metallurgical data were generally similar, but relatively stronger, than those for the lump ores. The chemistry of mineralogical-textural sub-sets of ore groups correlated with lump ore CH/CFT. Calculating ore group CH/CFT using a textural method is therefore capable of capturing differences in ore group chemistry that relate in part to texture. A textural database of microhardness and fracture toughness can be utilised with automated optical image analysis to provide geometallurgical characterisation of iron ores.

Forecast of sinter reduction degradation index and reducibility index and analysis of influencing factors using machine learning

Reduction degradation index (RDI) and reducibility index (RI) of sinter are considered as important metallurgical properties for assessing the quality of sintered ore for blast furnace iron-making. For the sake of promoting the permeability of a blast furnace burden and ensuring the smooth smelting process, mathematical models for the prediction of RDI and RI were constructed using machine learning respectively and the effects of factors such as sinter composition on the RDI and RI of sintered ore were analyzed in this article. From simulation results, the precision of the CatBoost model for predicting RDI can reach 98.32%, and the precision of the XGBoost model for predicting RI can reach 93.47%, meaning that the models are effective for the models to forecast the sinter RDI and RI. Moreover, the influence of 16 factors on RDI and RI was analyzed separately based on the SHapley Additive exPlanations (SHAP) method and the accurate predictive models built.

Effect of olivine as MgO-bearing flux on low- and high-alumina iron ore pellets

In the present study, the effect of MgO in the form of olivine flux on low- and high-alumina iron ore pellet mineralogy and pellet quality was studied. Green pellets were prepared by varying the MgO content from 0 to 1.5% with a basicity (CaO/SiO2) of 0.30. The pellets were tested for green pellet properties, cold crushing strength (CCS), and reduction degradation index (RDI) and fired at temperatures between 1300 and 1320 oC. An optical microscope with an image analyzer, SEM-EDS, was used to assess the mineralogical phases present in the pellets and the chemical analysis of the mineralogical phases, respectively. The laboratory tests showed that with increasing MgO addition in both low and high alumina pellets, magnesio-ferrite & silicate melt phases increased and the porosity and hematite phases decreased. The decrease in porosity was due to increase in silicate melt formation from the silica in the olivine. With increasing MgO addition, the CCS value of the pellets increased up to an MgO content of 0.9 to 1.1%. Thereafter, the CCS value of the pellets decreased with increasing MgO addition for both low and high alumina pellets. At an MgO content of 0.9 to 1.1%, the CCS value was higher due to the formation of a low melting point magnesio-ferrite phase, which imparted strength to the pellets. For pellets with an MgO level of >1.1, the RDI was within the control limit for both low- and high-alumina pellets. This may be due to a reduction in the porosity of the pellet and a better distribution of the silicate melt phase. Low-alumina pellets showed better physical and metallurgical properties compared to high-alumina iron ore pellets.

Preparation of sinter with low reduction degradation index for COREX reduction in a high proportion

Preparation of sinter with low reduction degradation index for COREX reduction in a high proportion

Production of pre-reduced sinter based on sensible heat updraft of sinter

Utilization of pre-reduction burden in the blast furnace ironmaking process is an important measure for realizing low-carbon operation. In this paper, a new process for the production of pre-reduced sinter based on sensible heat updraft of sinter was put forward. The effects of sinter temperature and reducing gas composition in the pre-reduction cooling section on metallization rate and sieve size distribution of pre-reduction sinter were studied. The results showed that the metallization rate and proportion of 10–12.5 mm particle size of pre-reduction sinter increase with the increase of sinter temperature. When the sintering temperature was 950 °C and the reducing gas was the mixture of H 2 and CO, the metallization rate of the pre-reduced sinter was up to 35.5%. When the sintering temperature was lower than 750 °C, the carbon deposition reaction between H 2 and CO reduces the proportion of 10–12.5 mm particle size of the pre-reduced sinter significantly. The metallurgical properties of pre-reduced sinter with different roasting systems under hydrogen-rich smelting in blast furnace were studied. The results showed that compared to the traditional sinter, the reduction degradation index, reducibility index, and softening-melting properties of pre-reduced sinter were improved, and the permeability and maximum differential pressure of the stock column were reduced, which was beneficial to the improvement of blast furnace production efficiency. Based on the comprehensive effects of sinter temperature and reducing gas composition on the metallization rate, sieve size distribution, and metallurgical properties of pre-reduced sinter, the quality of the pre-reduced sinter was better when the sintering temperature was higher than 750 °C and the reducing gas was a mixture of H 2 and CO. In addition, the new process could organically combine sinter sensible heat utilization, flue gas circulation, and denitrification to form a complete technological process, which had a good development prospect. • Production of pre-reduced sinter based on sensible heat of sinter was proposed. • Metallurgical properties of pre-reduction sinter were systematically studied. • The process can organically combine with flue gas circulation and denitrification. • Process route of production of pre-reduced sinter was schematically mapped.

Analysis of iron ore pellets properties concerning raw material mineralogy for effective utilization of mining waste

The value addition in iron ore mining waste generated from washing or beneficiation plants is a challenging task. The iron ore slimes, which contain low iron content with high gangue minerals like kaolinite, gibbsite, and quartzite, cannot be used directly for iron production. The present study focuses on utilization of iron ore slimes without beneficiation by blending with high-grade fines for making iron ore pellets. The pellets were prepared by adding slimes in different weight proportions (0, 10, 20, 30, 40, and 50%) with high-grade iron ore fines. The high-grade iron ore fines contain 64% Fe, 2.25% LOI, and Blaine number 2975 cm2/g, whereas iron ore slimes contain 52.45% Fe, 5.60% LOI, and Blaine number 7046 cm2/g. Pellets were produced without using bentonite as the binder. The pellet properties, such as drop number, green and dry compressive strength and moisture content of green pellet, cold compressive strength, porosity, swelling index, reduction degradation index, and reducibility index of fired pellet, have been investigated. The pellet mineralogy was analyzed using x-ray diffraction and optical microscope. The empirical correlation has been developed incorporating feed mineralogical data based on kaolinite and goethite to predict the physical and metallurgical properties of pellet.

Quantifying the composite microhardness and fracture toughness of iron ore sinter – a phase-based approach

ABSTRACT Microindentation testing was undertaken on sinter phases in iron ore sinter to determine the range and mean of phase/morphology microhardness. The mean fracture toughness of each sinter phase/texture was calculated from indent-associated radial cracks. A value for the composite microhardness (CH) and composite fracture toughness (CFT) was calculated for each sinter sample, based upon the modal proportion of constituent sinter phases. The CH and CFT of sinter phases and each sinter sample was compared to a range of metallurgical indices and major element chemistry to determine the extent of any correlation. Moderate to strong negative correlations were observed between sinter CH and sinter Tumble Index, Reduction Degradation Index and Reducibility Index and between sinter CFT and Tumble Index, Reduction Degradation Index and Reducibility Index. The microindentation technique has the potential to be further developed to routinely characterise and predict the metallurgical performance of sinter.

Influence of Fuel Level on Properties, Productivity, and Mineralogy of Russian Vanadiferous Titanomagnetite Sinter.

The influence of fuel level on Russian vanadiferous titanomagnetite sinter properties, productivity, and mineralogy are researched by sintering pot testing, metallographic microscopy, scanning electron microscopy analysis, and energy dispersive spectrometer (SEM-EDS) analysis. A comprehensive index is evaluated in conjunction with the same indexes and significance coefficient as that in the Panzhihua Iron and Steel Group. Results show that with the increasing fuel level from 3.5% to 6.0%, flame front speed, yield, tumbling test index (TI), and productivity, all first increase and then decrease. The low temperature reduction degradation index (RDI+3.15) and softening zone (ΔT) gradually increase while the RI and starting temperature of softening (T10), and ending temperature of softening (T40) decrease with increasing fuel levels from 3.5% to 6.0%. With the increase of fuel level from 3.5% to 6.0%, the content of FeO, SiO2, and MgO increase, while TiO2 shows a decrease. For the same increase in fuel level, the number of pores and calcium ferrite and hematite decrease but the silicate increases. In addition, in the fuel level range of 3.5% to 5.5%, magnetite correspondingly increases but then shows a drop after 5.5%. Moreover, when the fuel level increases to greater than 5.0%, FeOx and fayalite quickly increase and a small amount of metallic iron appears under the fuel level of 6.0%. Overall, the optimal fuel level under current production conditions and indicator selection is 4.0%.

Pelletization of hematite and synthesized magnetite concentrate from a banded hematite quartzite ore: A comparison study

A compressive pelletization study, for the utilization of an Indian Banded Hematite Quartzite ore, is presented in this communication. Iron ore concentrates have been generated utilizing the conventional beneficiation process and also by the approach of reduction roasting-magnetic separation. The Fe contents of the hematite and the synthesized magnetite concentrate were found to be 64.22 and 63.80%, respectively. The influence of different factors on the respective physical, chemical, and metallurgical properties of the fired pellets, generated through both the routes, have been compared. The pellets prepared from the synthesized magnetite attain the threshold Cold Crushing Strength (CCS) of 50 kg/pellet at a lower temperature of 1050 °C in comparison to hematite pellets (1100 °C). Also, the threshold CCS of 250 kg/pellet is attained by synthesized magnetite pellets at a lower temperature of 1250 °C compared to hematite pellets (1360 °C). The fired synthesized magnetite pellets also achieve the desired metallurgical properties i.e., Reduction Degradation Index (RDI), Reducibility Index (RI), and Swelling Index (SI) at par with the hematite pellets. Moreover, unlike the hematite pellets, the synthesized magnetite pellets do not need the addition of external carbon during the pellet making.

Effect of TiO2 on the Sintering Behavior of Low-Grade Vanadiferous Titanomagnetite Ore.

Low-grade vanadiferous titanomagnetite ore (LVTM) is as an important mineral resource for sintering ore manufacturing. Furthermore, TiO2 has a significant effect on the sintering process of iron ore fines. The effects of TiO2 on the metallurgical properties, microstructure, and mineral composition of LVTM sinter were investigated by sintering pot tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and mineral phase microanalysis. The results were as follows: as the TiO2 content increased from 1.75% to 4.55%, the flame front speed and productivity decreased, while the reduction degradation index (RDI) and softening properties deteriorated. In addition, the tumbler index (TI) values reached a maximum at TiO2 = 1.75%. In addition, with increasing TiO2 content, an increase in the magnetite and perovskite phase, and a decrease in calcium ferrite and hematite were found with an increase in TiO2 content. Thus, the lower the TiO2 content, the better the quality of the sinter.

Development and application of a novel fluxing compound for improving sintering performance of high alumina iron ore

ABSTRACT Blast furnaces (BF) ferrous burden consist of sinter (>50%) with rest being pellets and lump ore. Good sinter quality is necessary for efficient BF operation which depends on iron ore quality and its gangue. In gangue, alumina has a strong influence that adversely affects product quality and productivity. To address those effects this study presents a two-stage method. It involves the development of a novel low temperature melting synthetic flux i.e. Iron Rich Calcium Ferrite (IRCF) at Stage-1 and its addition in high alumina sinter feed at stage-II. Microstructural and dilatometry studies show that IRCF encourages the formation of silico-ferrite of calcium and aluminum (SFCA-1). The IRCF addition (6% max) in the high alumina (3.1%) sinter feed improves the Tumble index by 4.7 points, lowers the Abrasion index by 2.7 points, and decreases the return fines by 4.4%. Moreover, the Reduction degradation index (RDI) was also improved by 7.9 points.

Influence of Sea Sand on Sintering of V–Ti–Fe Concentrate—A Case Study from Indonesia

This study explores the feasibility of Indonesian sea sand in replacing V–Ti–Fe concentrate for sintering. The influence of different additive proportions of Indonesian sea sand on sintering index and sinter properties is examined in a laboratory by adjusting the substitution proportion from 5% to 40%. Results imply that vertical sintering speed and utility factor show an apparent decreasing trend, but drum strength, finished product rate and returned fine rate are not significantly affected with the increase in the proportion of Indonesian sea sand and with the decrease in the proportion of V–Ti–Fe concentrate. With the increase in the proportion of sea sand, the reduction degradation index of sinter at low temperatures declines sharply from 65% to 31%, the grade of sinter and content of TiO2 changes slightly, and the reduction degradation and degree decline. Unlike V–Ti–Fe concentrate, Indonesian sea sand does not perform well in sintering, and the substitution proportion should not exceed 35%.

Softening—melting behavior of mixed burden based on low-magnesium sinter and fluxed pellets

A low MgO content in sinter is conducive to reduce the MgO content in blast furnace slag. This study investigated the effect of MgO content in sinter on the softening—melting behavior of the mixed burden based on fluxed pellets. When the MgO content increased from 1.31wt% to 1.55wt%, the melting temperature of sinter increased to 1521°C. Such an increase was due to the formation of the high-melting-point slag phase. The reduction degradation index of sinter with 1.31wt% MgO content was better than that of others. The initial softening temperature of the mixed burden increased from 1104 to 1126°C as MgO content in sinter increased from 1.31wt% to 1.55wt%, and the melting temperature decreased from 1494 to 1460°C. The permeability index (S-value) of mixed burden decreased to 594.46 kPa·°C under a high MgO content with 1.55wt%, indicating that the permeability was improved. The slag phase composition of burden was mainly akermarite (Ca2MgSiO7) when the MgO content in sinter was 1.55wt%. The melting point of akermarite is 1450°C, which is lower than other phases.

Reducing process of sinter in COREX shaft furnace and influence of sinter proportion on reduction properties of composite burden

In order to reduce the materials cost of COREX ironmaking process, sinter has been introduced into the composite burden in China. This work explored the reducing process of sinter in COREX shaft furnace to clarify its reduction properties change and then the effect of sinter proportion on metallurgical performance of composite burden was investigated. The results show that the reducing process of sinter in COREX shaft furnace was basically same with that in blast furnace but sinter seems like breaking faster. Under reducing condition simulated COREX shaft furnace, sinter possessed the worst reduction degradation index (RDI) and undifferentiated reduction index (RI) compared with pellet and iron ore lumps. Macroscopic and microscopic mineralogy changes indicated that sinter presents integral cracking while pellet and lump ore present surface cracking, and no simple congruent relationship exists between cracks of the burden and its ultimate reduction degradation performance. The existence of partial metallurgical performance superposition between composite and single ferrous burden was confirmed. RDI+6.3≥70% and RDI+3.15≥80% were speculated as essential requirements for the composite burden containing sinter in COREX shaft furnace.

Study the reduction of mill scale with lean grade coal through RI-RDI

In the present study, efforts have been made to assess and study the reduction of mill scale in the presence of single gaseous reductant (i.e. CO gas) in RI-RDI (reducibility index (RI) and reduction degradation index) equipment. While conducting this study optimal process parameters like reduction temperature, mill scale size, reduction time and mill scale to coal ratio were analysed. An exceptional experimental profile is maintained inside the furnace to attain the optimum metallization. The mill scales are reduced inside the furnace and the extent of reduction is evaluated from the weight loss. Post conducting reduction in the RI-RDI test apparatus, the reduced mill scale is characterized for the microstructural and morphological studies using SEM, EDS, XRD. The most optimum results of the reduction were attained in RI-RDI apparatus giving iron content of (metallization) 89.15 % at the reduction temperature of 1050°C for 240 mins holding time. During the entire study on RI-RDI apparatus, flow rate of CO is maintained at 4.5 LPM (litres per minute) and N2 at 10.5 LPM. Finally, the degree of metallisation in the sample as well as the product material is calculated by using the chemical analysis process (dichromate and ferric chloride method). The characterization of produced iron powder was done by chemical analysis, XRD, and FE-SEM. The FE-SEM results confirm the presence of resultant pore characteristics. It is observed that mill scale can be significantly reduced to metallic iron by utilizing lean grade coal.

Thermodynamic Analysis of Iron Ore Sintering Process Based on Biomass Carbon

The sinter process of iron ore with biomass carbon instead of coke breeze as fuel was investigated via thermodynamic analysis in this paper through a comparison of sinter composition indexes, metallurgical properties, and pollutant emissions. Straw charcoal was used in this paper, and its replacement does not adversely affect the composition index of iron ore, namely Fe, FeO, basicity, S, nor the metallurgical properties, namely reduction degradation index and reduction index. However, the replacement has a great effect on the emissions of pollutant gases, including SO2, NOx, CO, and CO2. The thermodynamic analysis result shows that emissions of pollutant gases produced in the sinter process significantly decrease by using straw charcoal instead of coke breeze in sinter. The sintering maximum temperature has a great influence on sintering technical indicators. The best sintering maximum temperature is between 1300 and 1400 °C, where sinter ore with high quality can be obtained.

CFD Modeling and Analysis of Particle Size Reduction and Its Effect on Blast Furnace Ironmaking

Particle size reduction inevitably occurs inside ironmaking blast furnaces (BFs) but is not studied under BF conditions due to the lack of an effective tool. This paper simulates this phenomenon inside a 5000-m3 commercial BF using a recently developed three-dimensional computational fluid dynamics (CFD) process model. In particular, the sinter reduction degradation and coke gasification are modeled for considering the size reduction. By incorporating this information in the BF model, the in-furnace states and global performance are evaluated with respect to sinter reduction degradation index (RDI) under different conditions, e.g., keeping a constant blast rate or gas pressure drop. The results show that with increasing RDI, the bed permeability deteriorates, and there exists a critical value of RDI beyond which the decreased bed permeability leads to a significant drop in productivity for a given gas pressure drop. However, this problem can be mitigated substantially by charging more coke particles at the furnace periphery under the conditions considered. The proposed approach offers an extended capability to model and control BF operations.