Simulated Blast Furnace Conditions Research Articles

Non-isothermal kinetics of coke and iron ore melting reduction with variable activation energy model

Due to the significant consumption of coke in blast furnace ironmaking, a large amount of carbon emissions is generated. Thus, addressing the issues of energy conservation and carbon emission reduction in blast furnace ironmaking is imperative. The melting reduction reaction constitutes the predominant portion of carbon consumption during the ironmaking process. However, its kinetic behavior remains unclear to date, impeding energy-saving and carbon reduction efforts in blast furnaces. Consequently, this study conducted melting reduction experiments on two types of sinters and coke under simulated blast furnace conditions. A variable activation energy model (VAEM) was established for kinetic analysis of melting reduction. The conclusion is as follows: the variable activation energies of two types of sinters were determined to vary between 110 and 50 kJ/mol and 115–60 kJ/mol, the pre-exponential factors were 1.36 and 2.57. The deviation analysis showed that the predicted values using VAEM deviated from the experimental values by 1.17 % and 0.95 %. The reliability of VAEM was demonstrated. In turn, the kinetic behavior of coke and iron ore melting reduction was declared. It offers a theoretical basis for promoting the rational use of coke resources in blast furnace ironmaking and reducing carbon emissions.

A novel ironmaking decarbonisation technology — co-injection of hydrogen and biochar (CoHB): A CFD study of combustion in the raceway under simulated blast furnace conditions

In this paper, a novel ironmaking decarbonisation technology — co-injection of hydrogen and biochar (CoHB) in blast furnaces (BFs) is proposed for a feasible and sustainable carbon-neutral ironmaking. As the first study, to understand the fundamentals of internal combustion behaviour in the raceway related to CoHB, a three-dimensional (3D) computational fluid dynamics (CFD) model is developed to describe the multiphase reacting flow under simulated BF conditions. Particularly, the present model features a new treatment of volatile matter (VM) and an improved sub-model for hydrogen combustion. The model is successfully validated by the measurements of biochar injection and co-injection of hydrogen and coal, respectively. The typical in-furnace phenomena as well as the interaction between the hydrogen and biochar are analysed comprehensively. The results indicate that the proper injection of hydrogen through the annulus of the fuel lance is beneficial as the high local gas temperatures (1500 K to 1800 K) from the hydrogen combustion provide a biochar burnout enhancement of 6% during the biochar devolatilisation process. However, char reactions are hindered due to the oxygen competition with hydrogen combustion, resulting in a slightly reduced final biochar burnout. This study provides a quantitative insight into the combustion details related to this novel technology and serves as a reference to strive towards the net-carbon ironmaking initiative.

Microalgae blending for sustainable metallurgical coke production – Impacts on coking behaviour and coke quality

The steel industry is responsible for approximately 7% of global greenhouse gas emissions, mainly in the form of CO2 from the blast furnace ironmaking process. Among several strategies proposed to reduce CO2 emission, the partial replacement of coal with biomass during the cokemaking process has gained increasing interest. However, such replacement with lignocellulosic biomass species demonstrates a detrimental effect on coke quality. In this work, as an alternative to lignocellulosic biomass, the use of microalgae biomass (Chlorella vulgaris) is discussed for coal blending and bio-coke production. Three Australian metallurgical coal samples, varying in rank and fluidity, were blended with microalgae at up to 10 wt% to evaluate the impact of biomass addition rate on coking behaviour and coke quality. The work evaluates the impact of microalgae on coal blend properties, coking performance, and coke quality and strength (CSR/CRI, microtexture, and coke reactivity). The results demonstrated that microalgae blending with high-rank premium metallurgical coals did not adversely affect thermoplastic properties during coking or resultant bio-coke quality. Furthermore, the reactivity under simulated blast furnace conditions showed that microalgae addition led to a slight increase of up to 4.4% in coke gasification reactivity, which was attributed to the higher alkali content and isotropic textures in coke. Unlike lignocellulosic biomass, in bio-cokes produced by blending microalgae no porous and fibrous structures related to the biochar structure were identified. It was postulated that this non-fibrous nature of microalgae allows cokes to maintain their strength even for blending up to 10 wt%.

Reduction of Acid Iron Ore Pellets under Simulated Wall and Center Conditions in a Blast Furnace Shaft

The operational conditions, including temperature and gas composition, vary along the radial position in a blast furnace. Nevertheless, very few studies can be found in the literature that discuss how the reduction behavior of the ferrous burden varies along the radial position. In this study, the effect of the radial charging position on the reducibility of acid iron ore pellets was investigated using a laboratory-scale, high-temperature furnace in CO-CO2-N2 and CO-CO2-H2-H2O-N2 atmospheres up to 1100 °C. The experimental conditions were accumulated based on earlier measurements from a multi-point vertical probing campaign that was performed for a center-working European blast furnace. The main finding of this study is that the pellet reduction proceeded faster under simulated blast furnace conditions resembling those in the center area, compared to the wall area, because of a higher share of CO and H2 in the gas. Therefore, the pellet charging position affects its reduction path in a blast furnace. Additionally, it was shown that the presence of H2 and H2O in the reducing gas enhanced the progress of reduction reactions significantly and enhanced the formation of cracks slightly, both of which are desirable in blast furnace operation. The reducibility data attained in this study are important in understanding how temperature and gas composition is connected to the reduction degree under realistic process conditions.

A Simple Method of Evaluating the Thermal Properties of Metallurgical Cokes under High Temperature.

The reactivity index of weight loss (RI) and tumbling strength after the reaction (I10600) of manufacturing coke were first tested at a temperature series of 1100, 1200, and 1300 °C under CO2 atmosphere with different compositions and duration times to study the effects of temperature, time, and gas composition on coke hot strength. Then the RI/I10600, carbon structure, and optical texture of the cokes prepared from different single coals were mainly studied after a solution reaction with CO2 under a high temperature of 1300 °C and a standard temperature of 1100 °C. It was found that temperature greatly affects the RI/I10600 of coke, especially at high temperatures up to 1300 °C. Compared with standard tests under 1100 °C, the changes of RI/I10600 for different cokes are very different at 1300 °C, and the changes are greatly related to coke optical texture. Under a high temperature in the testing method, the tumbling strength of cokes with more isotropy increased, whereas it decreased for those with less isotropy. This simple method of using high temperature could yield the same results when compared with complicated simulated blast furnace conditions.

Non-isothermal reduction process analysis of iron-bearing burden with charging iron coke hot briquette under simulated blast furnace conditions

Non-isothermal reduction process analysis of iron-bearing burden with charging iron coke hot briquette under simulated blast furnace conditions

Preparation of high-strength biochar composite briquette for blast furnace ironmaking

In this research, using iron-oxide fines (average size: 2.5 μm) and biochar fines (average size: 50.0 μm), the biochar composite briquette (BCB) for blast furnace (BF) application was prepared by cold briquetting followed by heat treatment. The preparing conditions were optimized regarding its cold crushing strength. Anti-pulverization capability, reaction development, and structure evolution of the optimally-designed BCB under simulated BF conditions were then examined. Results of optimizing BCB preparation conditions showed that a heating temperature of 1073 K was optimal for preparing the BCB. The optimally-designed BCB contained 11.10 wt.% carbon, 72.21 wt.% Fe3O4, 11.25 wt.% FeO, and 0.77 wt.% Fe, 6.44 wt.% gangue, and had a cold crushing strength of 1800 N/briquette. Results of BCB behavior under simulated BF conditions showed that the cold crushing strength after partial reaction of the BCB ranged from 1500 N/briquette to 5500 N/briquette and its maximum volume shrinkage degree was 0.45. The high anti-pulverization capability of the BCB was supported by the slag matrix or the iron network. Under the simulated BF conditions, the BCB underwent five stages of reduction by atmosphere, partial self-reduction and reduction by atmosphere, full self-reduction, partial self-reduction and gasification by atmosphere, and gasification by atmosphere. It is inferred from the experimental findings that, by charging the BCB in BF, an increase of top gas utilization efficiency could be realized, and a favorable influence on lowering the temperature level of the thermal reserve zone could be obtained.

Coke Gasification in Blast Furnace Shaft Conditions with H2 and H2O Containing Atmospheres

Most of world steel in 2018 has been produced from virgin iron ore via the blast furnace (BF)—basic oxygen furnace route. Therewith the BF is one of the most important unit processes in worldwide steel making. Among others, energy efficiency of the BF is dependent on coke reactivity. Coke gasification occurs via solution‐loss reactions either with CO2 or H2O. Herein, the gasification of coke is studied in CO–CO2–H2–H2O–N2 atmosphere simulating the BF conditions. The simulated atmospheres are based on the measurements from an actual BF. This research studies the effect of the composition of the BF atmosphere representing conditions near the wall as well as at the center and influence of the H2O content on coke gasification under simulated BF conditions. It is found that the location plays a role in coke gasification: wall atmosphere yields higher coke gasification compared with center. Dynamic tests show that introduction of H2 and H2O in gas atmosphere fastens coke gasification by +119% at temperature range between 800 and 1200 °C in wall conditions. When H2O is present in gas atmosphere, the mass loss of coke is also greater in both wall and center 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.

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...

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.

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 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.