Improved refractories for the lining of blast furnaces

Pitak, N. V.; Fedoruk, R. M.; Shulyak, R. S.; Khmelenko, T. P.; Starshinov, B. N.; Zhukova, Z. D.

doi:10.1007/bf01282340

Refractories

1976

DOI: 10.1007/bf01282340

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Improved refractories for the lining of blast furnaces

N. V. Pitak

R. M. Fedoruk

R. S. Shulyak

et al.

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1978

1993

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“…For the purpose of increasing the life of this portion of the lining, especially in high-capacity blast furnaces, new forms of refractories based on kaolin raw materials have been developed and introduced [3]. In recent years the technology of dense refractories based on chamotte from Pologi and Novoselitsa kaolins has been introduced in the industry [4][5][6].The parts were characterized by high properties including 42.7 wt.% AlzO3, 1.4 wt.% FeaOs, refractoriness 1760~ open porosity 10-12%, compressive strength of 75-mm-thick parts 70-80 MPa and of 150-mm-thick ones 40-50 MPa, and temperature of the start of deformation under a load of 0.2 MPa 1520~The upper portion of the hearth and the apertures of the iron notches of a 5000-m ~ blast furnace were lined with these dense refractories [7]. For the lining ShT-I mortar was used~ Basic pig irons were melted in the furnace.…”

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Kaolin refractories after service in a blast-furnace hearth

et al. 1984

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Under conditions of acceleration of iron melting the lining of a blast-furnace hearth is subjected to the aggressive action of metal and slag. The upper portion of the hearth is made of chamotte refractories [i, 2]. For the purpose of increasing the life of this portion of the lining, especially in high-capacity blast furnaces, new forms of refractories based on kaolin raw materials have been developed and introduced [3]. In recent years the technology of dense refractories based on chamotte from Pologi and Novoselitsa kaolins has been introduced in the industry [4][5][6].The parts were characterized by high properties including 42.7 wt.% AlzO3, 1.4 wt.% FeaOs, refractoriness 1760~ open porosity 10-12%, compressive strength of 75-mm-thick parts 70-80 MPa and of 150-mm-thick ones 40-50 MPa, and temperature of the start of deformation under a load of 0.2 MPa 1520~The upper portion of the hearth and the apertures of the iron notches of a 5000-m ~ blast furnace were lined with these dense refractories [7]. For the lining ShT-I mortar was used~ Basic pig irons were melted in the furnace.After shutting down the furnace for major repairs, samples of the refractories were taken from the remaining lining for investigation.Samples No. 1-3 were cut from 230 • 150 • 150 mm blocks taken from the apertures of the iron notch at the level of its horizontal axis (Fig. i). Samples No. 4-8 were cut from 345 x 150 x 75 mm brick taken from the upper portion of the hearth in the third row above the carbon blocks at a distance of 2 m from the axis of the slag notch (between the iron and slag notches).Sample NOo 9 was taken from the working zone of the lining in the ninth row above the carbon block lining in the area under the slag notch.Sample No. i0 was also taken from the working zone in the ninth row above the carbon block lining but in an area located in the diametrically opposite portion of the hearth.The remaining thickness of the lining of blocks at the point of taking the samples was 350-400 mm and in the area on the level 700 mm from the axis of the notch 600-700 mm~ The wear of the lining in the upper portion of the hearth from the level of the tuyeres to the upper layer of carbon blocks was insignificant, about 150-200 mm. Here the wear of the lining was uniform starting from the face of the tuyeres and ending at the layer of chamotte brick located on the carbon block lining.Failure of the lining at the joints was not observed. The lining at the apertures and in the upper portion of the hearth was distinguished by its solidness and the mortar provided good burning together of the bricks.Slag and metal were not observed in the joints between the remaining parts and the mortar in the joints was saturated with carbon.

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“…The upper portion of the hearth and the apertures of the iron notches of a 5000-m ~ blast furnace were lined with these dense refractories [7]. For the lining ShT-I mortar was used~ Basic pig irons were melted in the furnace.…”

mentioning

confidence: 99%

Kaolin refractories after service in a blast-furnace hearth

et al. 1984

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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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Formation of kaolin refractories heated in different gaseous atmospheres

Pitak

Fedoruk

1993

Refractories

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Refractories made from raw materials that contain 41-42% AI203 are used in linings of blast-furnace shafts and the critical parts of other furnaces. They provide higb_ly resistant linings in heating units compared with firebrick [1][2][3]. The heating and cooling cycles and the body and gaseous-media compositions are important in the formation of the structure and phase composition of the refractories.The raw material for our investigation consisted of Polozhe and Novoselits kaolins (see Table 1). Analysis of the grain-size composition shows that with a rise in the amount of coarse fractions from 0.02 to 0.06 ram, the SiO 2 content increases sharply, while the proportion of A1203 diminishes (Fig. 1). In the Novoselits kaolin, besides the main materialkaolinite and quartz --there is some hydrargillite, marcasite, pyrites, futile, epidote, leucoxene, biotite, muscovite, microcline, and iron hydrated micas. The total refractive index of the kaolinite is 1.562 +__ 0.003. The marcasite and pyrite bond the main mass of iron impurities. The iron in both kaolins is distributed as oxides, hydroxides, low-solubility silicates, and hydrated micas; and it is bonded with the kaolinite in the form of isomorphous impurities.Thermal analysis of the Novoselits kaolin shows that at 310-315~ there is an endothermic effect, indicating the decomposition of the hydrargillite, at 410~ an exothermic effect for the oxidation of pyrite (FeS 2) and pyrrhotine (FeS 1 -x). Oxidation of the sulfides commences at 380~ with heat evolution according to the reaction FeS 2 + 1.50 2 = leO + SO 2, 2SO 2 + 0 2 ~ 2SO 3.The oxidation process occurs in two stages: adsorption of molecular oxygen and dissociation into atomic oxygen; then diffusion of the oxygen atoms deep into the lattice of the sulfide, and reverse diffusion of SO 3. With enlargement of the grains of FeS 2 we note an extension of the exothermic effects towards the higher temperatures. The magnitude of the exothermic effect for the decomposition of hydrargiUite at 430~ is affected by the exothermic effect for the oxidation of FeO, which is noted at 250-375~ its rate also depends on the particle sizes. The thermogram for pyrite shows an endothermic effect at 700-715~ with a high peak in reducing conditions, which is due to the polymorphic inversion of the pyrrhotine from the monoclinic to hexagonal modification. This indicates the preservation of sulfur compounds of iron at temperatures above 700~The two kaolins were used to press specimens, and these were then fired at 1600~ in oxidizing (air) and reducing (coke filling) conditions. The fired specimens were treated with a water solution of HF, and we then measured the amount of HF-insoluble residues (IR). It is shown that in reducing conditions the mullite-forming reaction in the kaolin begins earlier than in the specimens fired in oxidizing media, and the reaction shifts toward the lower temperatures by 100-200~ This is connected with the earlier formation of the liquid phase in reducing conditions (Fig. 2). A more marked influence is ex...

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Improved refractories for the lining of blast furnaces

Cited by 3 publications

References 0 publications

Kaolin refractories after service in a blast-furnace hearth

Kaolin refractories after service in a blast-furnace hearth

High-density kaolin refractories

Formation of kaolin refractories heated in different gaseous atmospheres

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