Influence of Magnesium Oxide Content on Kinetics of Lime Dissolution in Steelmaking Slags

Cheremisina, Elizaveta; Schenk, Johannes; Nocke, Ludwig; Paul, Alexander; Wimmer, Gerald

doi:10.2355/isijinternational.isijint-2016-341

Cited by 10 publications

(11 citation statements)

References 9 publications

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“…Lime dissolution in BOS slag has been studied by various researchers under static conditions, i.e., no convection in the limeslag system, and the experimental setups and conditions can be found from the original reports. [2][3][4][5] The lime-slag assemblies studied include mechanically mixing slag with lime particles, [2] placing a piece of lime in slag, [3] dipping a pressed and sintered lime rod (or cylinder) into stagnant slag, [2,4,5] and packing the slag into a dense lime crucible. [3] To increase the dynamics of the lime dissolution during experiments, a rotating disk/cylinder technique was used to study the dissolution rate of dense lime specimens in calcium-aluminosilicate-based melts at the temperatures of interest.…”

Section: Experimental Research On Lime Dissolution In Bos Slagmentioning

confidence: 99%

“…Physically mixing slag with lime particles; [2] placing a lime piece in slag; [3] dipping a lime rod/disc into stagnant slag; [4] packing slag in a dense lime crucible [5] (Ca, Fe)O solid solution next to lime particle and 2CaO•SiO 2 (or 3CaO•SiO 2 ) boundary layer next to slag at the lime particleslag interface are kinetic barriers for lime dissolution Rotating rod/disc Rotating a lime disc/cylinder in molten slag [6][7][8] Mass transfer in the slag phase is the limiting step of lime dissolution…”

Section: Static Conditionsmentioning

confidence: 99%

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Basic Oxygen Steelmaking Slag: Formation, Reaction, and Energy and Material Recovery

Spooner

et al. 2021

steel research int.

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The basic oxygen steelmaking (BOS) process produced over 70% of the global crude steel in 2018, [1] generating 100 to 150 kg of slag ("BOS slag") for every tonne of crude steel produced. BOS slag, a product of hot metal element (e.g., Si, Mn, Fe, P) oxidation and flux (e.g., lime, dolomite) dissolution, plays a critical role in the production of high-quality crude steel.All elements present in the hot metal charged in the BOS converter are thermodynamically very unstable with respect to their oxides when exposed to the oxygen jet at the BOS operating temperatures. Thus, carbon, silicon, manganese, phosphorus, and the iron itself all tend to oxidize very rapidly to form CO (or CO 2 ), SiO 2 , MnO, P 2 O 5 , and FeO (or Fe 2 O 3 ), respectively. In the BOS practice, large quantities of iron and silicon are initially oxidized to give a liquid, predominantly binary, FeO-SiO 2 slag, which floats on top of the metal pool. Usually lime (CaO) is rapidly added to "neutralize" this acid FeO-SiO 2 slag and produce a "basic" multicomponent FeO-SiO 2 -CaO-MnO-Al 2 O 3 -MgO-P 2 O 5 slag. This basic slag produces the correct partition of metalloids, particularly phosphorus, between the slag and metal and also protects the basic vessel lining (usually magnesite, MgO). Over the entire blowing period of the BOS process, this basic slag is emulsified with a large amount of gas bubbles and metal droplets, and the gas-slag-metal droplet reactions control the element transfer between the steel and slag (e.g., phosphorus removal and reversion) and subsequently the productivity and crude steel quality, which greatly attracts great interest from academics to understand the transient phenomena in the gas-BOS slag-metal droplet system. After completing its refining function in the BOS process, the hot BOS slag is poured into a slag pot. The BOS slag was considered a waste in old times but now as a secondary resource because it contains a large amount of thermal energy (temperature up to 1700 C), chemical energy (metallic and low-valence metallic oxides), and valuable materials (e.g., iron oxides).The behavior of BOS slag inside the BOS vessel, e.g., formation and reaction with gas and metal droplets, is still not clear and its recycling, including energy and material recovery, has always been challenging. This article introduces some BOS-slag-related research conducted by the present authors, in addition to a critical review of relevant research reported in the literature. It covers the topics of lime dissolution (slag formation), high-temperature-behavior interrogation through in situ observation, slag-metal droplet reaction mechanisms (spontaneous emulsification), and recovery of energy and materials from the molten BOS slag. This article aims to provide state-of-the-art understanding on relevant research topics and point out new research directions.

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Section: Experimental Research On Lime Dissolution In Bos Slagmentioning

confidence: 99%

Section: Static Conditionsmentioning

confidence: 99%

Basic Oxygen Steelmaking Slag: Formation, Reaction, and Energy and Material Recovery

Spooner

et al. 2021

steel research int.

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“…The detailed procedure including mass balance of slag was reported previously. [4] After reaching the desired process temperature 1300 -1600°C slag was held in the furnace for 30 min to ensure complete melting. CaO/lime sample was heated up as well to minimize thermal bouncy.…”

Section: Methodsmentioning

confidence: 99%

“…Solid compounds such as dicalcium silicate formed between industrial slag and calcium oxide inhibit the dissolution process. [4,5] This is the reason for lower values of CaO mass transfer coefficients in the industrial slag compared to model slag. The value of the apparent activation energy of the dissolution process of calcium oxide in the industrial slag is 70.6  8.1 kJ/mol.…”

Section: Dissolution Behavior Of Pure Caomentioning

confidence: 99%

DISSOLUTION RATE OF PURE CaO AND INDUSTRIAL LIME IN CONVERTER SLAGS

Cheremisina¹,

Schenk²,

Nocke³

et al. 2017

ABM Proceedings

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In steelmaking process lime serves as flux. Rapid lime assimilation and slag formation of the desired composition have a significant effect on the refining reactions. It is important to know the rate limiting step of lime dissolution to control and improve the converter process. Kinetics of pure CaO and industrial lime dissolution in model slag has been studied in the range of temperatures 1300-1600°C. Lime samples were prepared in cylinder form and immersed in the melt for predetermined time. Considering the total mass balance of CaO in the slag and linear dimensions of lime samples, mass transfer coefficients were derived. Diffusion coefficients were calculated under conditions of non-stationary diffusion. The derived activation energy of less than 200 kJ/mol indicates that diffusion is the limiting step in the process of lime-dissolution in slag.

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“…[10][11][12][13][14][15][16][17] Matsushima et al determined the dissolution rate of lime in the molten slag by recording the decrease in diameter of an immersed and rotating sintered lime rod. 10) They reported that the dissolution rates increased with the increases in each, the relative velocity between lime and the molten slag, the difference of the CaO content between the slag and the interfacial phase, and in the experimental temperature.…”

Section: Introductionmentioning

confidence: 99%

Effect of CO<sub>2</sub> Content in Quicklime on Dissolution Rate of Quicklime in Steelmaking Slags

et al. 2017

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The dissolution rate of lime in the molten slag is important for the efficient of steelmaking reactions. The dissolution rates of quicklime were conventionally measured by a rotating cylinder method, and they were quite lower compared with the estimated rates from actual steelmaking operations. Previously, the authors reported that the quicklime used in the actual operation had a much faster dissolution rate than completely calcined lime. During the dissolution of quicklime used in the actual operation, quicklime emits CO 2 gas twice, and the second gas formation effectively enhances the dissolution rate. Though the dissolution rates of quicklime with a CO 2 content of 0, 2, 4, and 9 mass% had been analyzed, the dissolution rates were scattered. The reason for this scattering of the data was that the CO 2 content of individual quicklime samples varied significantly within the same grade of quicklime, because the samples used in the previous study were produced by a rotary kiln process. Consequently, the dissolution rates were inconclusive, and the effect of the CO 2 content in quicklime on the dissolution rate of quicklime could not be fully clarified. In this study, the CO 2 content was controlled through the laboratory-based preparation of spherical quicklime samples and thus, the effect of the CO 2 content on the dissolution rate of quicklime in the molten slag could be precisely analyzed. Eventually, this approach allowed to propose the dissolution rate of quicklime with gas formation due to the thermal decomposition of the CaCO 3 core existing in the center of quicklime samples.

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Influence of Magnesium Oxide Content on Kinetics of Lime Dissolution in Steelmaking Slags

Cited by 10 publications

References 9 publications

Basic Oxygen Steelmaking Slag: Formation, Reaction, and Energy and Material Recovery

Basic Oxygen Steelmaking Slag: Formation, Reaction, and Energy and Material Recovery

DISSOLUTION RATE OF PURE CaO AND INDUSTRIAL LIME IN CONVERTER SLAGS

Effect of CO<sub>2</sub> Content in Quicklime on Dissolution Rate of Quicklime in Steelmaking Slags

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