Coal-char/Slag Interactions during Pulverised Coal Injection in a Blast Furnace: Reaction Kinetics and Wetting Investigations

Mehta, A. S.; Sahajwalla, Veena

doi:10.2355/isijinternational.43.1512

Cited by 28 publications

(43 citation statements)

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“…2COϭ[C]ϩ CO 2 , is claimed to be the main reaction. On the other hand, some studies 14) insisted that the driving force for the carburization with CO gas decreases with increasing temperature and the carburization by the gaseous reaction becomes gradually minor. The shell part of the reduced iron formed in Samarco ore-graphite composite pellets melted even at 1 250°C 10) although the gasification rate of graphite is very slow.…”

Section: Carburization Mechanism Of Reduced Iron Parti-mentioning

confidence: 99%

“…4) Generally considering, the wettability of graphite with carbon saturated molten iron and various compositions of slag is well known to be poor. 14) That is, in the system of molten iron and graphite plate, the contact angle of slag drops on the plate is usually greater than 90°. Therefore, the particles of coal char, graphite and coke are expected to be very easy to be liberated from the contact state with the reduced iron particles into ethanol by ultrasonic vibration.…”

Section: Verification Of Removing Attached Particles Of Thementioning

confidence: 99%

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Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Iguchi

Endo

2004

ISIJ International

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Section: Carburization Mechanism Of Reduced Iron Parti-mentioning

confidence: 99%

Section: Verification Of Removing Attached Particles Of Thementioning

confidence: 99%

Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Iguchi

Endo

2004

ISIJ International

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“…14) Viscous slag is believed to impair the counter current flow of gas and liquid permeability in bosh regions in a blast furnace. The viscosities of CaO-SiO 2 -Al 2 O 3 -MgOFeO system were measured under a range of bosh slag composition (CaO/SiO 2 1.15-1.6 and 3.5-10 mass% MgO).1) The study indicated that slag viscosity was minimum in a basicity range of 1.3, and low amounts of MgO in the slag was suggested in order to improve liquid permeability of the bosh region.1) However, at temperatures exceeding 1 450°C, the slag chemistry had a little impact on the viscosity particularly in the narrow composition range of slag under study.2) All previous studies regarding slag liquid permeability have primarily focused on the slag viscosity, and none of the studies have considered the influence and implication of coke and slag interfacial reactions.Recently, char/slag interaction has been studied, 5,[15][16][17] but there is only limited work available on study of interfacial wetting behaviour and in coke/slag systems. In addition, the role of composition of slag and carbonaceous materials and its influence on the reduction reactions is not fully understood.…”

mentioning

confidence: 99%

“…A similar trend was also noted in during slag reactions with char and graphite. 5,9) Subsequent rapid changes of contact angles after one hour are dictated by progressive decrease in the interfacial energy, and are related to the of kinetics of reduction reactions, mass transfer and subsequent interfacial phase formation.4) Due to reactive and dynamic nature of slag/carbon system, at a given temperature, the chemical composition of the interface changes continuously with time. For the good wetting Slag 1, the interfacial basicity was found to be low, as indicated by the presence of high concentration of silica at the interface.…”

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Wetting and Interfacial Reaction Investigations of Coke/Slag Systems and Associated Liquid Permeability of Blast Furnaces

et al. 2005

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An interfacial study between metallurgical coke and synthetic slags representing typical slag chemistry of bosh regions of an operating blast furnace was conducted at 1 500°C using a horizontal laboratory furnace. The wetting characteristics of coke with slag was studied by measuring dynamic contact angle of sessile droplet of slag on coke substrate, while reaction kinetics of interface was monitored by measuring the amount of CO and CO 2 gases with the help of infrared analyzer. The interface chemistry was also examined by SEM/EDS/EPMA. The study demonstrated that coke wettability was strongly dependent both on the slag composition as well as coke chemistry such that low basicity (CaO/SiO 2 ) of slag, that is high amounts of oxides of silicon enhanced the wetting propensity of slag. The study further showed that the wettability of coke with slag was found to improve with increased extent of gasification, and was attributed to higher ash content of partially gasified cokes. The CO/CO 2 measurements of off gases from the reacting chamber were used to demonstrate that slag wettability with coke was primarily controlled by the kinetics of reduction of metal oxides at the slag/coke interface particularly that of silica. The study demonstrates that in addition to slag composition, coke properties could also influence the liquid permeability of lower zone of the blast furnace, and hence needs attention while optimizing the bosh slag composition for high productivity blast furnace operation.KEY WORDS: blast furnace; coke; slag composition; reactivity; wetting; slag-coke interaction; interfacial reaction. Where g SG , g LS and g LG are the surface and interfacial tensions at solid-gas, solid-liquid and liquid-gas interfaces, respectively. For a reactive system, the solid phase actively participates in the reaction at the interface, then the driving force (g SG Ϫg LS ) for wetting could increase due to the contribution of Gibbs free energy, which could be through mass transfer across the interface or formation of new phases at the interface. 8) As the slag/coke/gas is a reactive system, the contact angle and consequently the wetting behaviour will be influenced by the reaction of slag/coke carbon as well as in-situ reaction of coke ash/coke carbon. Consequently, slag and carbon compositions of interface will change continuously over the reaction duration, and hence wetting will be function of time often referred as dynamic wetting.In slag/carbonaceous systems, reduction of iron oxide and silica are known to be the main reactions affecting wettability. 4,5,9) On the other hand, the same oxides of silicon and iron are the main reducible oxides present in the bosh slag in lower part of the blast furnace. In addition, coke also contains oxides of iron and silicon which could also participate in reduction reactions. Therefore, it is imperative to look at the some of blast furnace reactions relating to silica and iron reduction phenomena. For example, direct reduction of molten iron oxide by solid carbon is known to occur acco...

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The wetting process and crystallisation of Al₂O₃ substrate with molten slags: Addition of CaO‐Fe₂O₃

Baoliang

Jiao

et al. 2022

Asia-Pacific J Chem Eng

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As fluxes, CaO and Fe2O3 are widely applied to effectively improve the melting characteristics of coal ash. However, there are few studies on the effects of CaO and Fe2O3 contents in coal ash on the wetting of refractories used in entrained‐flow slagging gasifiers. This paper investigates the melting properties of ash slag and the wetting process in corundum‐based refractories in relation to the total amount of CaO and Fe2O3 and their proportions in coal ash. The rates of change of the apparent contact angle (ACA) and differential contact angle (DCA) as a function of temperature are employed to evaluate the wetting behaviour of the coal ash during the heating process. The results demonstrate that changes in the ACA result from the expansion or shrinkage of the slag. In particular, two abrupt changes in the ACA are observed at an Fe2O3/CaO ratio of .25. The wettability deteriorates after quenching at ratios ranging from .13 to .67. Differences in the crystal structure and elemental distribution along with the spreading direction are observed. X‐ray diffraction and FactSage calculations show that temperature changes the crystal composition and solid–liquid phase content, supporting the slag wetting process from the perspective of ash fusibility. A fraction of the liquid phase increases twice with increases in temperature, explaining the abrupt change in the ACAs. Overall, the wetting process of the slag can be explained by the surface tension and DCA. The wetting begins at 430 mN m−1 and becomes the most prominent at 435 mN m−1. Finally, an Fe2O3/CaO ratio of .25 is found to be more suitable for the long‐term operation of corundum‐based refractories.

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Coal-char/Slag Interactions during Pulverised Coal Injection in a Blast Furnace: Reaction Kinetics and Wetting Investigations

Cited by 28 publications

References 11 publications

Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Wetting and Interfacial Reaction Investigations of Coke/Slag Systems and Associated Liquid Permeability of Blast Furnaces

The wetting process and crystallisation of Al₂O₃ substrate with molten slags: Addition of CaO‐Fe₂O₃

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Coal-char/Slag Interactions during Pulverised Coal Injection in a Blast Furnace: Reaction Kinetics and Wetting Investigations

Cited by 28 publications

References 11 publications

Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Carburized Carbon Content of Reduced Iron and Direct Carburization in Carbon Composite Iron Ore Pellets Heated at Elevated Temperature

Wetting and Interfacial Reaction Investigations of Coke/Slag Systems and Associated Liquid Permeability of Blast Furnaces

The wetting process and crystallisation of Al2O3 substrate with molten slags: Addition of CaO‐Fe2O3

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The wetting process and crystallisation of Al₂O₃ substrate with molten slags: Addition of CaO‐Fe₂O₃