High-density kaolin refractories for the lining of a 5000 m3 blast furnace

Bakalkin, A. P.; Pitak, N. V.; Starshinov, B. N.; Fedoruk, R. M.; Shulyak, R. S.; Vasilchenko, V. S.; Zima, V. Kh.; Davydov, I. P.; Shcherbina, R. E.; Belokrys, G. A.

doi:10.1007/bf01287876

Cited by 6 publications

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“…4 4), and roasting losses A P (5, 6) of specimens of Novoselki kaolin vs roasting temperature t in air (1,3,5) and in a fine coke charge (2,4,6). Fig.…”

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confidence: 99%

“…4. Content G of A120~ (1,2) and SiC) z (3,4) in insoluble residues of ohamottes obtained by roasting at different temperatures t in air (1, 3) and a fine coke charge (2,4). Figure 1 gives the results of an investigation of the properties of chamotte obtained by roasting Novoselki kaolin with different amounts of added quartz sand of natural grain size and of hydrargillite.…”

Section: ~ 4 1 2omentioning

confidence: 99%

“…But the chemical composition of clays and kaolins cannot be the principal criterion for assessing the quality of the initial material. In a number of cases [1], chamotte and artifacts with different properties are obtained from kaolins of the same composition, roasted under the same conditions. This is due to the fact that certain kaolin varieties contain not only kaolinite but also admixtures of quartz sand and hydrargillite.…”

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Changes in the properties of aluminosilicate refractories during roasting and service

Pitak

1979

Refractories

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The properties of aluminosilicate refractories and their service life depend on the composition and content of crystalline, amorphous (liquid), and gaseous phases. The principal crystalline phase of aluminosilicate refractories (chamotte and high-alumina refractories) is mullite. Above the composition of mullite, the refractories contain corundum; below the muilite composition, cristobalite and quartz are present. A second phase in the cold refractory is a vitreous substance; in the hot refractory, it is a melt, a third phase is air or a mixture of gases of complex composition; the gas phase composition may differ significantly in the open and closed pores. During roasting and service, each phase exerts an influence on the properties of the refractories and must be taken into account when developing heat-resistant linings.Much attention has been paid to the formation and change in the crystalline phases of refractories, but somewhat less to the vitreous substance, and even less to the role of the gas phase.This communication gives results of investigations, obtained during roasting of kaolin and kaolin--alumina briquets and aluminosilicate refractories in various gaseous media, and the calculated changes in the Gibbs free energies (AZ) over a wide range of partial pressures of oxygen for the reactions of formation of silica, silicon monoxide, and mullite.The quality of aluminosilicate refractories largely depends on the properties of chamotte. The principal requirement for the preparation of high-grade chamotte is purity of the clays, kaolins, and other initial materials. But the chemical composition of clays and kaolins cannot be the principal criterion for assessing the quality of the initial material. In a number of cases [1], chamotte and artifacts with different properties are obtained from kaolins of the same composition, roasted under the same conditions. This is due to the fact that certain kaolin varieties contain not only kaolinite but also admixtures of quartz sand and hydrargillite. In such cases the compositions of the initial material are equivalent, but the properties of the artifacts obtained differ. ~, 4 1 2O ~2 762, O 1Z

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“…4 4), and roasting losses A P (5, 6) of specimens of Novoselki kaolin vs roasting temperature t in air (1,3,5) and in a fine coke charge (2,4,6). Fig.…”

Section: ~ 4 1 2omentioning

confidence: 99%

Section: ~ 4 1 2omentioning

confidence: 99%

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Changes in the properties of aluminosilicate refractories during roasting and service

Pitak

1979

Refractories

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“…The special-grade Novoselitsy kaolin is the best raw material of Soviet origin for the production of the high-quality refractories of porosity below 12% for the 5000-m ~ blast furnace at the Krivoi Rog Metallurgical Plant [3,4].The high nonhomogeneity of the grain size, mineral, and chemical compositions of the Novoselitsy kaolins are the main source of the technological difficulties encountered in the roasting of the kaolin to chamotte and the manufacture of high-performance refractory products. Even a small amount of quartz sand in the kaolin increases the water absorption and porosity of the chamotte [5, 6].…”

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Beneficiation of secondary Novoselitsy kaolin

1978

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The secondary kaolins of the Novoselitsy deposits are used mainly for the production of dense chamotte brick for the high-temperature part of blast-furnace stacks [I, 2]. The special-grade Novoselitsy kaolin is the best raw material of Soviet origin for the production of the high-quality refractories of porosity below 12% for the 5000-m ~ blast furnace at the Krivoi Rog Metallurgical Plant [3,4].The high nonhomogeneity of the grain size, mineral, and chemical compositions of the Novoselitsy kaolins are the main source of the technological difficulties encountered in the roasting of the kaolin to chamotte and the manufacture of high-performance refractory products. Even a small amount of quartz sand in the kaolin increases the water absorption and porosity of the chamotte [5, 6]. Among the other impurities which produce an adverse affect on the quality of the chamotte are sulfur compounds of iron which during roasting in a rotary kiln do not dissociate completely, the result being that the refractory product undergoes bloating during firing; and titanium compounds which form a significant proportion of the melt and reduce the service durability of the product [7, p. 210].The most critical refractories are produced from the special grade KN--O of Novoselitsy kaolin. The yield of this grade in the extraction operations is falling constantly so that the Ural Institute of Beneficiation and the Mechanical Processing of Minerals initiated research in a benefieiation technology for low-grade Novoselitsy kaolin with a view to obtaining a concentrate finer than 0.056 mm containing at least 43% A1203 and not over 1.3% Fe203 (on the calcined substance).The sample of kaolin of grade KN-2 conformed to TU 14-8-160--75 and contained 34.48% A1203 (in terms of the dry substance), 49.18% SiO2, 1.30% Fe20~, 1.46% TiO2, 0.12% K~O + Na20, 0.20% CaO, and 0.06% MgO; calcination loss 12.97%. The mineral composition of the sample was as follows: 76.5% kaolinite, 9.5% quartz, and 11% hydromica with the accessory minerals marcasite (0.7%), rutile (0.8%), iron hydroxides (0.2%), and a carbonlike substance (0.7%).A fractlonwise chemical analysis of the Novoselitsy kaolin (Table i) showed that in terms of the clay content the fractions finer than 2 ~ are the purest:. The fractions coarser than 2 ~ contain more Fe20~ and free quartz; the high iron oxide content is attributable to the presence of marcasite.An analysis of the separation curves (Fig. i) suggested that Novoselltsy kaolin can be beneficiated by separating it into grain sizes. For a beneficiated kaolin of grade KN-O conraining at least 43% Ala03 for the limiting grain size is 100-200 ~. A smaller grain size of separation offers no advantages because it gives a significantly lower yield of concentrate and less extracted A1203 although the AI~03 content is then slightly higher and the Fe20~ content lower.An investigation was carried out of the wet gravitational beneficia~ion of the kaolin in high-density suspensions [8]. The separation of high-concentration clay suspensions into graln-...

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“…In the USSR, the stacks of more than 40 blast furnaces including one of 5000 m 3 have been lined with dense kaolin brick of porosity below 12% [5,6]. The stacks of blast furnaces Nos.…”

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High-density kaolin refractories

et al. 1978

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Experimental investigations and Industrial experience have shown that dense and high-density kaolin refractories produced from the pure grades of the kaolin starting material are efficient products for the lining of the stack of blast furnaces [1][2][3][4][5][6].In the USSR, the stacks of more than 40 blast furnaces including one of 5000 m 3 have been lined with dense kaolin brick of porosity below 12% [5,6]. The stacks of blast furnaces Nos. 4 and 5 of the Zaporozhstal' Plant are lined with dense kaolin refractories and their useful life is 10-11 years.A further increase in the density of the refractories by using a fine-grained composition for the semidry molding on toggle presses is difficult to achieve owing to the development of overpressure cracks even at relatively low specific molding pressures.An increase in the specific molding pressure is effective only at medium pressures. A further increase in the pressure does not result in a decrease In the porosity of the green product [7].An increase in the firing temperature does not always produce the desired effect either because the highfired coarse-grained part of the composition is compacted only slightly during sintering [8] and sometimes increases in volume by 5% [9] while the bonding part of the composition shrinks in volume by about 18%. Such a large difference in the volumetric changes of the grains and bond results in an increase in the number and size of the pores including the closed kind.In this article the results are described of development work on a new technology which permits the industrial production of refractories of a maximum porosity of 1@/o on toggle presses from relatively coarsegrained kaolin batches.The experiments were carried out with chamotte with a water absorption of 3% from Novoselitsy and Polozhsk kaolins. To begin with, an investigation was carried out of the changes in the properties of thetwo types of chamotte of fractions 1-5 mm after firing for 5 h at 1550~It was found that the apparent density of the Novoselitsy kaolin ShKN1 decreased during firing from 2.49 to 2.40 g/cm 3, while that of the Polozhsk chamotte ShKP increased from 2.44 to 2.52 g/cm 3, a finding which shows that the volumes of these chamottes change in opposite directions during firing, i.e., that of the Novoselitsy chamotte increases while that of the Polozhsk chamotte decreases. These volumetric changes of the chamottes are reflected In the physicotechnical properties of the finished products.In ideal presentation the model of a porous solid consists of eight spheres of diameter d confined in a cubic space and in direct contact with each other. The volume Vf of the free space in such a solid equals

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High-density kaolin refractories for the lining of a 5000 m3 blast furnace

Cited by 6 publications

References 0 publications

Changes in the properties of aluminosilicate refractories during roasting and service

Changes in the properties of aluminosilicate refractories during roasting and service

Beneficiation of secondary Novoselitsy kaolin

High-density kaolin refractories

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