Simulated Blast Furnace Research Articles

Evaluating the behavior of catalyst coated nut-coke in blast furnace conditions

For efficient blast furnace ironmaking, it is desired to have low reducing agent rate, primarily coke rate. Developing technology to improve reaction efficiency of the blast furnace is extremely important as it has the potential to allow a decrease in the reducing agent rate as well as CO2 emissions. The reaction efficiency of blast furnace can be improved by lowering the Thermal Reserve Zone (TRZ) temperature; which is also the starting temperature of coke gasification reaction. In present study, nut-coke has been coated with in-plant waste, consisting mainly of iron oxide and calcium oxide, as catalyst. There was a clear increase of 10 points in the reactivity of coated nut-coke. The coated nut-coke have been subjected to non-standard high temperature experiments simulating blast furnace conditions with reducing gas consisting of CO, CO2 and N2 to capture the effect of catalytic coating on the onset of gasification reaction. The high temperature experiments carried out advise the following: i) A drop of 100 °C in the reaction beginning temperature of catalyst coated nut-coke as compared to non-coated one ii) A typical calculation shows that the lowering of reaction beginning temperature corresponds to a potential carbon rate savings of about 2.5 kg/ton of hot metal (thm). Furthermore, in a trial conducted at blast furnace with charging catalyst coated nut-coke, it has been observed that the carbon rate during the trial period was 3 kg/thm lower than the base period. The findings of blast furnace trial agree with that of the experimental one.

Degradation behaviors of coke under complex solution loss conditions

Solution loss reaction of coke provides reducing agent for ironmaking, which is an important chemical reaction in blast furnace. The coke itself is also degraded by the loss of carbon. In this paper, the degradation behavior of coke under complex conditions including alkali metal enrichment, simulated blast furnace temperature and atmosphere was studied. The pore size and pore wall thickness distribution of coke were measured by a microscope to characterize the structure of coke. The gasification reaction rate of coke matrix was measured by a thermogravimetric analyzer to characterize the matrix reactivity of coke. The results show that a coke has high CRI and low CSR, but it has high matrix reactivity and thick pore wall, which may lead higher strength after solution loss under alkali metal enrichment and simulated blast furnace atmosphere and heating conditions.

Ferrous burden behaviour under nut coke mixed charge conditions

ABSTRACT Effect of nut coke addition with ferrous burden (pellet and sinter mixture) is experimentally investigated under simulated blast furnace conditions. Nut coke mixing degree was varied (0, 20 and 40 wt-%) as a replacement of the regular coke. During smelting, the ferrous bed evolves through three distinct stages of shrinkage due to indirect reduction, softening and melting, respectively. Nut coke increases the reduction kinetics, limits softening and enhances iron carburization in the ferrous bed to affect all three stages. Additionally, nut coke physically hinders the sintering among the ferrous burden to keep the interstitial voids open, which exponentially increases the gas permeability. A significant impact of nut coke mixing occurs in the cohesive zone temperature range, which is decreased by 77°C upon addition of 40 wt-% nut coke. Various experimental results give supports for the extensive utilization of nut coke as a replacement of regular coke in the blast furnace.

A comparative study of pellets, sinter and mixed ferrous burden behaviour under simulated blast furnace conditions

ABSTRACT Physicochemical behaviour of the pellets, sinters and its mixture (60% pellets: 40% sinter) is investigated by a series of smelting and quenching experiments. For all ferrous raw-material beds, three distinct stages of bed shrinkage occur due to indirect reduction, softening and melting. However, the characteristic nature (displacement, temperature and permeability) differ with the ferrous raw-material type. In mixed ferrous bed, the first and third stages are found to be controlled by the pellets (individual particle shrinkage) and sinter (slow melting rate), respectively. Second stage behaviour is initially observed to be close to the pellet and later to that of sinter. In mixed bed (upto 1505°C), the interaction between the pellet and sinter is limited to the interface only. The sinter slag is observed to control the melting and dripping properties of the mixed bed.These results gives an understanding of individual and mixed burden behaviour under blast furnace conditions.

Reduction of Iron Ore Pellets, Sinter, and Lump Ore under Simulated Blast Furnace Conditions

A blast furnace (BF) is the dominant process for making iron in the world. The BF is charged with metallurgical coke and iron burden materials including iron ore pellets, sinter, and lump ore. While descending in the BF the charge materials reduce. The iron‐bearing materials should reduce fast and remain in the solid form until as high a temperature as possible to ensure reaction contact with reducing gas and iron oxides. Herein, the reducibility of the iron ore pellet, sinter, and lump ore in the BF shaft are focused on. The experiments are conducted isothermally with a blast furnace simulator (BFS) high‐temperature furnace at four different temperatures (700, 800, 900, and 1000 °C) for 300 min. The experimental atmosphere consists of CO, CO2, H2, H2O, and N2 simulating the conditions in the BF shaft. It is found that lump ore has lowest reduction rate in all test conditions, and at lower temperatures iron ore pellets reduce faster than sinter, and this is reversed at higher temperatures. Furthermore, the reduction rate of sinter and iron ore pellets begins to resemble each other at higher temperatures.

Experimental study on impact of iron coke hot briquette as an alternative fuel on isothermal reduction of pellets under simulated blast furnace conditions

Highly reactive iron coke hot briquette (ICHB) made by co-carbonizing the agglomerate of iron ore concentrate and blended coals is considered to be an alternative fuel to reduce carbon emission in a blast furnace through decreasing the temperature of the thermal reserve zone. The reduction process of iron-bearing burden is greatly significant for the smelting and smooth operation of blast furnace. In this study, the effects of ICHB on the reduction process of pellet were experimentally investigated under simulated conditions within a blast furnace, and the interaction mechanism between the gasification of ICHB and the reduction of pellet was revealed. The results showed that the reduction degree of pellet with mixing charging 10% ICHB is increased by 6.48% in comparison to that without adding ICHB and conventional coke. Furthermore, with increasing the temperature from 900 °C to 1100 °C, the reduction degree of pellet without adding ICHB is increased from 20.20% to 32.45%, while it is remarkably improved from 20.93% to 40.14% under the condition of mixed charging 10% ICHB. Moreover, with increasing the mixed ratio of ICHB from zero to 30%, the reduction degree of pellet evidently is accelerated from 23.69% to 33.72%, but the improvement in the reduction degree of pellet is levelled off as the charging ratio of ICHB is more than 20%, suggesting that the promotion has a limitation. The interaction mechanism is indicated that the gasification of ICHB and the reduction of pellet are mutually promoted through increasing the reducing potential in local region during the reaction process.

Self-Reduction Behavior of Bio-Coal Containing Iron Ore Composites

The utilization of CO2 neutral carbon instead of fossil carbon is one way to mitigate CO2 emissions in the steel industry. Using reactive reducing agent, e.g., bio-coal (pre-treated biomass) in iron ore composites for the blast furnace can also enhance the self-reduction. The current study aims at investigating the self-reduction behavior of bio-coal containing iron ore composites under inert conditions and simulated blast furnace thermal profile. Composites with and without 10% bio-coal and sufficient amount of coke breeze to keep the C/O molar ratio equal to one were mixed and Portland cement was used as a binder. The self-reduction of composites was investigated by thermogravimetric analyses under inert atmosphere. To explore the reduction progress in each type of composite vertical tube furnace tests were conducted in nitrogen atmosphere up to temperatures selected based on thermogravimetric results. Bio-coal properties as fixed carbon, volatile matter content and ash composition influence the reduction of iron oxide. The reduction of the bio-coal containing composites begins at about 500 °C, a lower temperature compared to that for the composite with coke as only carbon source. The hematite was successfully reduced to metallic iron at 850 °C by using bio-coal, whereas with coke as a reducing agent temperature up to 1100 °C was required.

A lithium–aluminosilicate zeolite membrane for separation of CO2 from simulated blast furnace gas

In this study, for the first time, the small pore size (0.28 × 0.37 nm) Li–aluminosilicate zeolite membrane was synthesized for separation of CO2 from H2–CO2 and H2–CO2–N2–CO (simulated blast furnace gas) gas mixtures. Li–aluminosilicate membranes were prepared on porous clay alumina tubes by sonication mediated hydrothermal method using pre synthesized zeolite powders as seeds. The zeolite formation was confirmed by X-ray diffraction pattern and FESEM analysis. The scanning electron micrograph of the membrane, suggested the uniformity of the dense structure of the membrane. Single-gas and mixed-gas permeation experiments through membranes were carried out at 25 °C using H2, CO2 and N2 single-component gases and mixture of H2–CO2, H2–CO2–N2–CO for simulated blast furnace gas composition. Synthesized Li–aluminosilicate zeolite shows appreciable CO2 adsorption capacity at liquid nitrogen temperature compared with other reported zeolites. In case of single gas permeation, membrane shows usual pattern of permeation. For mixture gas, separation efficiency of Li–zeolite membrane increased abruptly compared to the other zeolite membranes. The maximum CO2–H2, CO2–N2 and CO2–CO separation selectivities were found to be 78, 8.7 and 67.3 respectively, with permeance of H2, CO2 and N2 2.21 × 10−7, 1.01 × 10−7 and 0.8 × 10−7 mol m−2 s−1 Pa−1 at 25 °C respectively.

Effects of coal interactions during cokemaking on coke properties under simulated blast furnace conditions

The cokes produced from single coals and blends of these coals were investigated under the simulated blast furnace (BF) conditions. Comparison of the weighted average values of single coal cokes and the measured values of cokes from blends revealed the coal interactions during carbonisation and the effects of these interactions on coke properties under the simulated BF conditions. Blending coals together resulted in a significant fluidity reduction from the expected values. The large amount of volatile matter released from the low rank coal provided better conditions of crystallites growth for other coal components in the blends, thereby resulting in the pervasively higher measured graphitization degree. Raman spectroscopy analysis indicated that the higher measured graphitization degree was mainly contributed by the lenticular and ribbon microtextures. Although the caking properties of the blends were remarkably reduced from the expected values, the measured microstrength did not have a significant difference from the calculated values. However, the measured macrostrength were higher than the calculated values. The differences in the softening and resolidification temperatures of coals restricted the dilatation but promoted the contraction of the blends, which resulted in a reduced porosity development from the expected value, thereby improving the strength of the produced cokes.

High-Temperature Interactions Between Vanadium-Titanium Magnetite Carbon Composite Hot Briquettes and Pellets Under Simulated Blast Furnace Conditions

The high-temperature interactions between vanadium-titanium magnetite carbon composite hot briquettes (VTM-CCBs) and pellets were systematically investigated under simulated blast furnace conditions with respect to the reduction behavior, softening–melting–dripping characteristics, gas permeability, and Ti(C, N) precipitation mechanisms. The results showed that VTM-CCB charging can promote the reduction of the pellet in the packed bed and decrease the compressive strength of the pellet after reduction. The compressive strength of the VTM-CCB after reduction decreased with increasing temperature when the FC/O ratio (the ratio of the fixed carbon mol(C) in coal to the reducible oxygen mol(O) in iron oxides) was higher than 1.0. With an FC/O ratio lower than 1.0, the compressive strength of the VTM-CCB initially decreased and then increased. The FC/O ratio has a significant influence on the softening–melting interaction mechanism between the VTM-CCB and the pellet. With an FC/O ratio of 0.8, the bonding layer at the interface between the pellet and the VTM-CCB (consisting of molten fayalitic slag) can promote the softening process, thereby decreasing the softening start and end temperatures. By increasing the FC/O ratio to 1.4, a dense metallic iron shell with relatively high strength formed at the interface and restricted the collapse of the packed bed, thereby increasing the softening start and end temperatures and ensuring the transport of the reduction gas through the packed bed. The melting point of the primary slag phase increased with increasing FC/O ratio due to a decrease in the FeO content, which resulted in an increase in the melting start temperature from 1273 °C to 1294 °C (1546 K to 1567 K). The gas permeability in the cohesive zone increased with an increasing FC/O ratio of the VTM-CCB due to a combination of the skeletal role performed by the residual VTM-CCB and the decrease in the liquid slag proportion. In addition, as the FC/O ratio increased to 1.4, unconsumed carbon promoted the precipitation of Ti(C, N) at the slag–carbon and slag–metal interfaces, which resulted in a substantial increase in the dripping temperature and deterioration of the dripping behavior of the packed bed. Therefore, to suppress the precipitation of Ti(C, N) and improve the dripping behavior of the packed bed, the FC/O ratio of the charged VTM-CCB should be controlled within an appropriate range.

Effect of Nut Coke Addition on Physicochemical Behaviour of Pellet Bed in Ironmaking Blast Furnace

One of the primary causes that limit the blast furnace productivity is the resistance exerted to the gas flow in the cohesive zone by the ferrous burden. Use of nut coke (10–40 mm) together with ferrous burden proves beneficial for decreasing this resistance. In present study, effect of nut coke addition on the olivine fluxed iron ore pellet bed is investigated under simulated blast furnace conditions. Nut coke mixing degree (replacement ratio of regular coke) was varied from 0 to 40 wt% to investigate the physicochemical characteristics of the pellet bed. Three distinct stages of bed contraction are observed and the principal phenomena governing these stages are indirect reduction, softening and melting. It is observed that nut coke mixing enhances the reduction kinetics, lowers softening, limits sintering and promotes iron carburisation to affects all three stages. In the second stage, the temperature and displacement range is reduced by 60°C and 24%, respectively upon 40 wt% nut coke mixing. Addition of nut coke exponentially increases the gas permeability (represented by pressure drop and S-value). A higher degree of carburisation achieved on the pellet shell (iron) is suggested to be the principal reason for decrease in the pellet melting temperature. The pellets softening temperature increases by approximately 4°C, melting and dripping temperature drops by 11°C and 12°C, respectively, for every 10 wt% nut coke addition. Consequently, the nut coke addition shortens the softening, melting and dripping temperature ranges, which shows improved properties of the cohesive zone.

High-Temperature Reduction and Melting Mechanism of Sinter with Different MgO Content

Adding MgO to sinter is considered to be a popular counter measure to cope with the use of high Al2O3 ores. The purpose of this paper is to investigate the effect of the MgO content on the reduction melting behavior in order to clarify the main mechanism of melting and dripping under simulated blast furnace (BF) conditions. It was found that reduction behavior was inhibited with an increased MgO content; the reduction mechanism was further investigated by means of XRD, SEM, and kinetic analysis. The influence of MgO on the melting mechanism of high basicity sinter was also studied. The softening start temperature and softening temperature increased, and the softening zone increased as a whole with the increased MgO contents from 1.3 to 2.0 wt%. The melting temperature was similar, because the MgO remained in an unslagged state and existed in wustite as FeO-MgO solid solution. The dripping temperature was increased; the main reason for this was that high melting-point slags appeared, and that it was more difficult for carburization to occur with increased MgO content. The most appropriate MgO content in the sinter was 1.3 wt% according to principal component analysis (PCA).

Petrographic Analysis of Cokes Reacted under Simulated Blast Furnace Conditions

Two cokes prepared from coals of different ranks were subjected to gasification and annealing under the simulated blast furnace (BF) conditions. The changes in coke petrography were studied using techniques and algorithms developed by Pearson Coal Petrography, Inc.; the coke microstrength was measured using ultramicro indentation. Gasification under the simulated BF conditions consumed both reactive maceral-derived components (RMDCs) and inert maceral-derived components (IMDCs) at the lump periphery; however, the degradation did not penetrate to the core of the coke lump during gasification. The annealing at 2000 °C after gasification further promoted the degradation of IMDCs and RMDCs located at the lump surface; the degradation penetrated toward the center of the coke lump during annealing. The consumption of the coke matrix in the lump core mainly concentrated on the IMDC microtexture, but the RMDC microtexture generally remained. Under the simulated BF gasification conditions, both bireflectance and m...

Lignin from Bioethanol Production as a Part of a Raw Material Blend of a Metallurgical Coke

Replacement of part of the coal in the coking blend with lignin would be an attractive solution to reduce greenhouse gas emissions from blast furnace (BF) iron making and for obtaining additional value for lignin utilization. In this research, both non-pyrolyzed and pyrolyzed lignin was used in a powdered form in a coking blend for replacing 5-, 10- and 15 m-% of coal in the raw material bulk. Graphite powder was used as a comparative replacement material for lignin with corresponding replacement ratios. Thermogravimetric analysis was performed for all the raw materials to obtaining valuable data about the raw material behavior in the coking process. In addition, chemical analysis was performed for dried lignin, pyrolyzed lignin and coal that were used in the experiments. Produced bio cokes were tested in a compression strength experiment, in reactivity tests in a simulating blast furnace shaft gas profile and temperature. Also, an image analysis of the porosity and pore shapes was performed with a custom made MatLab-based image analysis software. The tests revealed that the pyrolysis of lignin before the coking process has an increasing impact on the bio coke strength, while the reactivity of the bio-cokes did not significantly change. However, after certain level of lignin addition the effect of lignin pyrolysis before the coking lost its significance. According to results of this research, the structure of bio cokes changes significantly when replacement of coal with lignin in the raw material bulk is at a level of 10 m-% or more, causing less uniform structure thus leading to a less strong structure for bio cokes.

Coke texture, reactivity and tumbler strength after reaction under simulated blast furnace conditions

The reactivity and tumbler strength after reaction of cokes made from coals of different ranks and different regions of the world were tested under standard and simulated blast furnace (BF) conditions. The composition of coke optical textures and reactivity of different textures were investigated. It was found that reactivity and tumbler strength (I10600) after reaction of cokes are strongly related to the optical texture. For most cokes containing large amounts of isotropic textures, the reactivity index (RI) tested under simulated BF conditions is lower than CRI tested under standard conditions, and the I10600 under simulated BF conditions is higher than CSR under standard conditions. The reactivity of isotropic textures in most cokes is appreciably higher than that of anisotropic textures under standard conditions. Under simulated BF conditions, however, the reactivity of isotropic textures decreases significantly and the reactivity of anisotropic textures increases for the most part. This leads to narrowing the reactivity gap between isotropic and anisotropic textures.

CFD study of charcoal combustion in a simulated ironmaking blast furnace

Biomass is a carbon-neutral solid fuel and has the potential to replace coal in pulverised coal injection (PCI) operation of ironmaking blast furnaces (BFs). In this study, a three-dimensional (3D) computational fluid dynamics (CFD) model is used to evaluate the charcoal combustion behaviours under a range of PCI conditions. The key PCI variables include blast temperature, O2 concentration in the blast, mean particle size of charcoal, and charcoal injection rate. In particular, the combustion behaviours are investigated and compared at two locations, namely, along the centreline and over the entire chamber. The simulation results indicate that the final burnout along the centreline is more sensitive to the changes of operational conditions compared to the burnout over the entire chamber under the BF conditions. Furthermore, the effects of key operational variables on the two burnout calculations are identified quantitatively. For example, the increased blast temperature or the reduced mean particle size can improve the two burnouts both, due to the extra energy provided and large surface area, respectively. However, the increased O2 concentration in the blast from 21% to 23% can improve the final burnout only from 64% to 72%, but the further increase of O2 concentration in the blast cannot lead to a further increase for both two burnouts. High blast temperature, high oxygen concentration and fine particle size will allow for a higher burnout. This study provides an effective method of understanding and optimising biomass injection in BF practice.

Pore Structure and Integrity of a Bio-Coke under Simulated Blast Furnace Conditions

Coke produced with 7.5 wt % charcoal addition and its base blend coke were subjected to gasification and annealing simulating the conditions within an iron-making blast furnace (BF). The changes in...

Effect of MgO addition on the metallurgical properties of the vanadium-titanium pellet with simulating blast furnace conditions

ABSTRACTMgO addition plays a vital role in improving the quality of pellets. In this study, the effects of MgO addition on the compressive strength, reducibility, reduction swelling characteristics and softening-melting performance of V-Ti pellets were explored systematically with simulating BF conditions. From the results, it can be observed that the compressive strength decreased with increasing MgO due to the formation of magnesioferrite, the restriction of recrystallization-agglomeration of haematite and the decreasing of molten slag. The reducibility of V-Ti pellets improved substantially due to the increase of the porosity. The decreasing of RSI is mainly caused by the decreasing of lattice volume swelling during the transition from MgO·Fe2O3 to (Mg,Fe)O. In addition, the softening-melting behavior and permeability of V-Ti pellets packed bed was found to be improved with increasing MgO content. In sum, the V-Ti pellets with a MgO content higher than 2.4% exhibits optimum metallurgical properties.

Effect of coal properties on the strength of coke under simulated blast furnace conditions

Eight cokes made from coals/blend with different properties (vitrinite mean maximum reflectance = 0.90–1.66, logarithm Gieseler maximum fluidity = 4.16–1.30) were subjected to gasification and annealing simulating the conditions within an ironmaking blast furnace (BF). The specific methodology utilised included gasification of coke with BF gas-temperature profile from 900 to 1400 °C (corresponding from the thermal reserve zone to the cohesive zone) and annealing of coke up to 2000 °C (corresponding to the raceway region). The coke microstrength and macrostrength were determined using ultra-micro indentation and tensile test to understand the effect of coal precursor properties on the strength of the resulting coke and the changes when processed under the simulated BF conditions. Under the high temperatures in the simulated BF processes, the cokes from different coals showed significant differences in their properties, even though most of them had similar Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) values. Coke microtextures experienced significant reflectance loss and structure change upon simulated BF gasification and annealing conditions. The decreases in mean maximum reflectance and bireflectance were more severe for the coke produced from the high rank coal. The cokes made from coals with higher rank and lower Gieseler maximum fluidity exhibited greater change in their microstructure upon high temperatures. As a result, microstrength of cokes produced from these coals decreased more than that of coke made from the parent coals with a lower rank and higher Gieseler maximum fluidity; this tendency was more significant in the Reactive Maceral Derived Components (RMDC) than Inert Maceral Derived Components (IMDC) microtextural type. Degradation of macrostrength of cokes produced from coals with higher rank and lower maximum fluidity was also more severe due to the greater decrease in their microstrength.

Reduction behavior of vanadium-titanium magnetite carbon composite hot briquette in blast furnace process

The reduction behavior of a new type of blast furnace burden named vanadium‑titanium magnetite carbon composite hot briquette (hereinafter abbreviated as VTM-CCB), including fraction of reaction (f), reduction shrinking, crushing strength after reduction, phase transformation of valuable elements, and softening-melting-dripping behavior, were investigated with simulating blast furnace conditions in laboratory in this article. The reduction process of VTM-CCB could be divided into four stages. The devolatilization of the coal and the reduction of magnetite to wustite mainly occur successively in the first two stages. In the third stage, the reduction rate is much higher than that in the second stage due to the high carbon gasification rate. The reduction of Ti-bearing iron oxides occurs in the final stage. The shrinking of VTM-CCB samples is caused by the removal of carbon and oxygen and the suppression of the growth of iron whiskers during the reduction of wustite to metallic iron. The crushing strength of VTM-CCB after reduction is found to decrease from 1800 N to 600 N correspondingly with increasing temperature from 600 °C to 1100 °C. The loss of the crushing strength correlates to the pyrolysis of the coal, the carbon gasification, and the reduction of iron oxides. The phase transformation of valuable elements during reduction could be described as follows: Fe3O4 → FeO → Fe; Fe2.75Ti0.25O4 → Fe2.5Ti0.5O4 → (Fe2TiO4) → FeTiO3 → (FeTi2O5) → TiO2. The softening-melting-dripping behavior and permeability of mixed burden is improved obviously with charging a certain amount of VTM-CCB. However, the precipitation of Ti(C,N) would deteriorate the dripping behavior of packed bed when VTM-CCB charging ratio exceeds 20%.