Improvement of Desulfurization by Aluminum Addition into Hot Metal in Powdered Lime Injection Process

Shoji, Takeshi; Mitsuo, Toshiharu; Hatta, Yoshihiro; Ono, Hiroki; Mori, Hisashi; Kai, Tsuyoshi

doi:10.2355/tetsutohagane1955.68.6_609

Cited by 9 publications

(4 citation statements)

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“…Ueda et al observed that the desulfurization rate was influenced by the geometrical characteristics of the lime and concluded that the relatively large pores, which were approximately 20 μ m or more in diameter, played an important role in the reaction kinetics. Further to these findings, Shoji et al 3) clarified that the addition of Al to the Sicontaining hot metal improved the reaction rate. According to their investigation, the enhanced rate was due to the formation of a slag layer of the CaO-Al2O3-FeO system on the lime surface.…”

Section: Introductionmentioning

confidence: 95%

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Influence of Solid CaO and Liquid Slag on Hot Metal Desulfurization

et al. 2012

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Mechanical stirring is widely used for hot metal desulfurization in Japan. In this process, solid lime is added as flux and emulsified into molten iron using a vortex formed by the stirrer. However, in addition to the added solid lime, the liquid top slag on the ladle is emulsified and forms granules. To clarify the roles of the solid lime and liquid slag in hot metal desulfurization, the reaction rates of slag, solid lime, and slag with solid lime are determined and the interfacial layers are observed.The results are summarized as follows:(1) The desulfurization rate is very slow when a solid lime rod is immersed into hot metal without slag. The reason for the slow desulfurization is the formation of an interfacial layer, which inhibits the mass transfer of sulfur.(2) Because sulfur is not detected inside the solid CaO, the mass transfer of sulfur from the liquid slag to the solid CaO does not occur. Therefore, it is believed that solid CaO does not play a direct role in the desulfurization reaction, and thus, the reaction is solely due to the liquid slag. A good relationship between the desulfurization rates and the sulfide capacity of the liquid slag is found.(3) When tricalcium aluminate forms at the interface, the desulfurization rate is increased by the immersion of a CaO rod. This is due to the supply of CaO to the slag because this interfacial layer does not inhibit the mass transfer.

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Section: Introductionmentioning

confidence: 95%

“…This rod is also mounted on an alumina tube. The bulk density of the sintered CaO is 2.92 g/cm 3 , and that of metallurgical lime is 1.79 g/cm 3 , as measured by the Archimedean method using ethanol. For the experimental setup shown in Fig.…”

Section: Desulfurization By Slag Solid Lime and Slag Withmentioning

confidence: 99%

Influence of Solid CaO and Liquid Slag on Hot Metal Desulfurization

et al. 2012

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“…Shoji et al 2) indicated that desulfurization could be improved by addition of aluminum into hot metal in the powdered lime injection process. Instead of 2CaO · SiO 2 and 3CaO · SiO 2 layer formed on the lime surface, which retarded sulfur transferring to its interior, the molten CaOAl 2 O 3 -FeO layer was formed on the lime surface to enhance sulfur transfer.…”

Section: Introductionmentioning

confidence: 99%

Effect of Lime Particle Size on Melting Behavior of Lime-containing Flux

et al. 2007

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By use of an infrared-ray vacuum furnace, effect of CaO particle size on melting behavior of lime-containing flux is studied in the present work. Two kinds of CaO particles of the average diameters of 10 mm and 75 mm are used. Four kinds of lime-containing fluxes are employed, which are CaO-SiO 2 , CaO-FeO, CaO-SiO 2 -Al 2 O 3 as ironmaking slag and CaO-SiO 2 -FeO as steelmaking slag.The relationships of reaction products, heating temperature and holding time are obtained for the fluxes of CaO-SiO 2 and CaO-FeO under the present experimental conditions. As for the flux melting, decreasing the lime particle size can shorten the holding time, but can not decrease the heating temperature. In the melting process of CaO-SiO 2 , a layer of 2CaO · SiO 2 is observed on the periphery of CaO particle, which tends to inhibit the melting of CaO particles. Decreasing the CaO particle size can also effectively promote the dissolution of CaO particles into both kinds of slag of CaO-SiO 2 -Al 2 O 3 and CaO-SiO 2 -FeO.KEY WORDS: lime-containing flux; melting; dissolution of lime; slag formation; particle size of lime.MnO x , FeO x , and TiO 2 into Al 2 O 3 -CaO-SiO 2 slag increased the dissolution rate of lime into slag, while addition of SiO 2 had an opposite effect. 15) In the present work, by use of infrared-ray vacuum furnace, effect of lime particle size on melting behavior of lime-containing flux is studied. Four kinds of fluxes are employed, which are CaO-SiO 2 , CaO-FeO, CaO-SiO 2 -Al 2 O 3 as ironmaking slag and CaO-SiO 2 -FeO as steelmaking slag. The used two different sizes of CaO particles have the average diameters of 10 and 75 mm. For the different kinds of fluxes, the relationships of reaction products, heating temperature and holding time are obtained from analysis results of XRD patterns. The status of flux melting is observed with a scanning electron microscope (SEM) and is analyzed with an energy dispersive spectrometer (EDS). Figure 1 shows the morphologies of all kinds of materials before formation of pellets. Calcium oxide particles of the small size, which were the commercial reagent packed with Ar gas, were relatively uniform in diameter, having the average diameter of 10 mm with the purity of 99.9 %. Calcium oxide particles of the large size were prepared as rapidly as possible by crushing the calcium oxide blocks of the commercial reagent and being sieved with sieve pores of 50 mm and 100 mm, having the average diameter of 75 mm and the purity of 99.9 %. Silicon oxide powders were very fine in size with the average diameter of only 2.0 mm. ahematite powders had greatly varied diameters and irregular shapes, having the average diameter of 15 mm and purity of 99.5 %. The diameters of aluminium oxide powders were varied, ranging from 20 to 80 mm. The aluminum oxide particles were usually in clusters formed by many fine aluminum oxide powders and the aluminum oxide powders had the purity of 99.9 %. Experimental Apparatus and ProceduresSlag 1 of CaO-SiO 2 -Al 2 O 3 was produced by melting the mixture of CaO,...

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“…Thermodynamically, a lower oxygen potential has the effect of enhancing the desulfurization reaction. Several studies [7][8][9][10][11] have reported the effect of aluminum as a reducing agent in hot metal desulfurization. However, only a few reports concerning the effects of reducing gases [12][13][14] have been published.…”

Section: Introductionmentioning

confidence: 99%

Effect of Propane Gas on Hot Metal Desulfurization by CaO Based Flux

Kikuchi¹,

Nabeshima²,

Kishimoto³

2012

ISIJ Int.

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The effect of propane gas blowing on hot metal desulfurization was investigated in laboratory-scale experiments and commercial plant tests. Desulfurization tests were carried out by two methods, flux injection and mechanical stirring. Flux injection:In the 4 ton-scale and commercial-scale tests, the flux efficiency for desulfurization increased by 1.2-1.7 times by mixing of propane gas with the nitrogen carrier gas at propane gas ratio of 10-58%. The effect of propane gas mixing on improving desulfurization efficiency is presumed to be caused by a decrease in the local oxygen potential, together with an increase in the interfacial area between hot metal and flux. Mechanical stirring:A top-blowing propane gas technique was examined in both 4 ton-scale tests and commercial hot metal desulfurization operation by mechanical stirring with an impeller. The flux efficiency for desulfurization increased by 1.25 times with top-blowing propane gas. The presumed effects of the top-blowing propane gas are enhancement of stirring energy in addition to reduction of the oxygen potential in hot metal and increase in the interfacial area between hot metal and flux. The sulfur partition ratio between slag and hot metal with mechanical stirring was higher than that with flux injection in a torpedo car at the same oxygen potential level with utilizing propane gas.

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Improvement of Desulfurization by Aluminum Addition into Hot Metal in Powdered Lime Injection Process

Cited by 9 publications

References 1 publication

Influence of Solid CaO and Liquid Slag on Hot Metal Desulfurization

Influence of Solid CaO and Liquid Slag on Hot Metal Desulfurization

Effect of Lime Particle Size on Melting Behavior of Lime-containing Flux

Effect of Propane Gas on Hot Metal Desulfurization by CaO Based Flux

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