Service of refractories in a blast furnace shaft

Pitak, N. V.; Gin'yar, E. A.; Levitanskii, V. I.; Rutkovskii, G. Ya.

doi:10.1007/bf01284497

Cited by 6 publications

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“…Let the apparent density of the original chamotte be Tch and that of the ehamotte after the second firing ? 'ch o The degree C c of compaction will then equal c a =~]'ch/.~eh o (2) After the change in the volume of the chamotte grains as a result of firing, the volume of the free space will equal yf'=vf/Cc. (3) In real conditions the volume of the free space is smaller owing to the multifraction composition of the granual chamotte and depends on the proportion of the fractions.…”

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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

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“…This means that an increase in the period between stack repairs is an urgent problem which requires a tLmely solution.The durability of the stack lining depends on the composition of the primary slags, the amount of alkalies and zincite in the blast-furnace charge, the composition of the gaseous medium, the abrasive wear by the charge, the thermal stresses, and the conditions under which the furnace is operated, its design, and other factors [2].The specific influence exerted by each of these factors on the durability of the lining differs from one factory to another. This complicates the creation of a universal refractory with all the necessary properties and makes it difficult to establish the most important characteristics governing the stability of artifacts during service.…”

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“…In recent years, refractories made from fused oxides have become more extensively used in the dosing equipment for continuous casting of steel [1,2] and as the sliding gates in steel-casting buckets [3,4]. The most stringent specifications in relation to thermal shock resistance, strength, and metal and slag resistance are set for such products.…”

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Influence of synthetic primary slag on fracture of kaolin refractories for blast-furnace stacks

et al. 1980

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The service life of refractories in a blast-furnace stack is 3.5-4 years, whereas in the hearth and hearth bottom it is from 10 to 12 years [1]. This means that an increase in the period between stack repairs is an urgent problem which requires a tLmely solution.The durability of the stack lining depends on the composition of the primary slags, the amount of alkalies and zincite in the blast-furnace charge, the composition of the gaseous medium, the abrasive wear by the charge, the thermal stresses, and the conditions under which the furnace is operated, its design, and other factors [2].The specific influence exerted by each of these factors on the durability of the lining differs from one factory to another. This complicates the creation of a universal refractory with all the necessary properties and makes it difficult to establish the most important characteristics governing the stability of artifacts during service. For this reason, there is no agreement concerning the selection of refractories for blastfurnace stacks; however, laboratory and factory investigations have shown that compact kaolin refractories with an A1203 content of 42-45% are promising materials for the lining of the cooled part of the stack.Compact kaolin artifacts with a porosity of less than 12% are being manufactured at the Zaporozhe Refractory Works and the Chasov Yar Refractory Artifact Works, and chamotte artifacts with a porosity of

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“…It is known [3,4,12,13] that the slag and alkali resistances of blast-furnace refractories are important service qualities. Slag resistance tests* were performed by the dynamic method on specimens of special configuration, sawn off from the commercial refractories.…”

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Quality enhancement of refractories the bosh and lower stack of blast furnaces

et al. 1979

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A number of reports [1][2][3][4] have indicated the need to enhance the quality of refractories for blast furnaces, particularly for the bosh and lower stack. One method of improving the properties of aluminosilicate refractories is impregnation with coal tar, coal-tar pitch, and other carbon-containing materials. This method is used in the manufacture of carbon-based artifacts of enhanced density [5][6][7]; Smirnov and Sobolev [8] recommend impregnation of refractories for lining oxygen steelmaking converters, and Simonov and Shubin [9] impregnation of the plates of sliding gates of steel-teeming ladles. It is noted that the higher is the coke residue, the greater will the extent to which the pores are filled with carbon, and the lower will be the wettability, particularly that of oxide refractories, by the metal; this increases their service life.On the basis of literature data [1,[5][6][7][8][9] and investigations, the Ukrainian Scientific-Research Institute of Refractories (UkrNIIO) has developed a procedure for impregnating chamotte refractories* to lengthen their service life in blast furnaces.The change in the macro-and microstructure of the refractories before and after impregnation with carbon-containing substance was investigated macroseopically and under a microscope, using transparent and polished sections and immersion preparations; furthermore, the structure was investigated with a U~MV-100A electron microscope, using a two-stage replica with a cleavage face. Contrast was bestowed on the replicas by oblique shadowing with metallic chromium.The initial refractories were found to have numerous pores (rounded, oval, or irregular) penetrating the refractory uniformly. The pores were generally confined to the binder and to the contact of the chamotte grains with it; we sometimes observed discontinuous (occasionally, continuous) cracks round the quartz and chamotte grains. The size of the pores ranged from 0.05 to 0.7 ram, but sometimes reached 1 ram.During impregnation of refractories, the carbon-containing substance penetrates mainly into the binder, which becomes dark gray (almost black), regardless of the number of impregnations; the chamotte grains in it are made conspicuous by their lighter color.The petrographic analysis data agree closely with the results of an investigation of replicas of chamotte grains of specimens subjected to impregnation and then to heat treatment. Under the microscope we see that the carbon-containing substance first penetrates into the cracks formed at the contact of the chamotte grains with the binder, and then enters the large open cracks and pores. Filling of the pores begins at the walls and progresses to the center. When filling is incomplete, the pore centers do not display carbon-containing substance. After impregnation and heat treatment, on replicas of the refractory we see that the pore surface is covered with a layer of carbon-containing substance, 0.15-0.35 pm thick (Fig. 1), which blocks and reduces the contact surface of the chamotte refractories.As shown by ...

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Service of refractories in a blast furnace shaft

Cited by 6 publications

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High-density kaolin refractories

High-density kaolin refractories

Influence of synthetic primary slag on fracture of kaolin refractories for blast-furnace stacks

Quality enhancement of refractories the bosh and lower stack of blast furnaces

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