RU2182140C1 - Magnesia-silica refractory - Google Patents

Abstract

FIELD: refractory industry; manufacture of magnesia-silica refractories used for linings of heating and roasting furnaces and other thermal units. SUBSTANCE: magnesia-silica refractory includes mineral phases at the following ratio, mass-%: forsterite, 43 to 62; aluminomagnesium spinal, 14 to 22; magnesia-pedalferic spinellide of the following composition: Mg (Cr, Al) Fe₂O₄, 12 to 20; periclase, 4 to 11 and monticellite, 1 to 4. proposed refractory is characterized by low ad abradability at temperature of from 300 to 1200 C including presence of scale. Technogenious raw material, that is slag of production of high- carbon ferrochromium is used for manufacture of proposed refractory. EFFECT: enhanced efficiency. 3 tbl

Description

 The invention relates to the refractory industry and can be used for the production of magnesia-silicate refractories used in the linings of heating, calcining furnaces and other thermal units.

Known magnesia-silicate refractory, including, wt.%: Forsterite 49-57, magnesia-chromium-iron spinel composition Mg (Cr, Al, Fe) ₂ O ₄ 21-26, periclase 20-25 (Pat. RF 2165396, M. Cl .7 C 04 B 35/20, 35/04, 35/66, publ. 04/20/2001).

Known refractory has a relatively high clinker resistance and is intended for intermediate repairs of the lining of the sintering zone of rotary kilns of the cement industry. However, this refractory has a high abrasion in the temperature range 300-1200 ^o C, which does not allow its use in the linings of the loading zone of shaft and rotary kilns, where the main cause of wear is the abrasion of the lining from the side of the calcined bulk material (magnesite, dolomite, etc.) .

 In heating metallurgical furnaces, attrition of the refractory occurs in the presence of scale. During the service, free periclase contained in the intergranular component of a known refractory reacts with scale to form magnesioferrite, which is accompanied by volumetric changes, loosening of the structure of the refractory, a decrease in its strength and, as a result, leads to more intense abrasion. In this regard, the well-known magnesia-silicate refractory is not recommended for use in such lining elements as the heels of heating metallurgical furnaces, the lower structure of open-hearth furnaces, where operation is carried out in the presence of iron-containing reagents.

 Closest to the invention is magnesia-silicate refractory, including, wt.%: Forsterite 51-73, aluminum-magnesium spinel 21-30, periclase 5-15, monticellite 1-4 (Aut. St. USSR 1266122, M. C. C. 04 In 35/20, published on November 30, 1987).

 Known refractory has a sufficiently high resistance to alkaline silicate melts and has low gas permeability. To obtain it, technogenic raw materials can be used - ferroalloy slag, which is not only economically feasible, but also solves environmental problems.

However, despite the content of aluminum-magnesium spinel in the structure, the known refractory is not sufficiently resistant to abrasion at service temperatures of 300-1200 ^o C, especially in the presence of scale or other iron-containing reagent. The reason for the increase in the abradability of the known refractory when exposed to scale is the presence of an increased amount of free periclase (up to 15 wt.%) Interacting with iron oxides.

 These disadvantages limit the scope of application of the known magnesia-silicate refractory, not allowing it to be used effectively in the hearths of heating metallurgical furnaces, loading zones of calcination furnaces, etc.

 The objective of the invention is to improve the quality of magnesia-silicate refractory based on industrial raw materials to expand its field of application.

 The technical result that can be achieved by using the invention is to reduce abrasion at high temperatures, including in the presence of scale.

The specified technical result is achieved in that the magnesia-silicate refractory, including forsterite, aluminum spinel, periclase and monticellite, according to the invention additionally contains magnesia-chromium-iron spinel composition Mg (Cr, Al, Fe) ₂ O ₄ in the following ratio of mineral phases, wt. %:
Forsterite - 43-62
Aluminum Magnesium Spinel - 14-22
The specified spinel - 12-20
Periclase - 4-11
Monticellit - 1-4
The proposed combination of mineral phases in the claimed ratio provides an increase in the quality of magnesia-silicate refractory. The reduction of abrasion at high temperatures (300-1200 ^o C), including in the presence of scale, was achieved due to the formation of a dense structure, which contains a significant amount of the most abrasive and chemically stable spinel phase, both in the form of an additional magnesia-chromium-iron spinel, and in the form of aluminomagnesian spinel. At the same time, free periclase is distributed in the lattice of the spinel phase and is thereby protected from active interaction with iron oxides. The content of periclase is reduced to 11%.

 A change in the proposed ratio of mineral phases degrades the properties of magnesia-silicate refractory. A decrease in the content of magnesia-chromium-iron spinel less than 12 wt.% Leads to an increase in the abrasion of the refractory at high temperature, especially in the presence of scale. With an increase in the proportion of spinel more than 20 wt.%, The properties of the refractory deteriorate due to the loose structure due to insufficient sintering of the refractory and a corresponding decrease in strength and abrasion.

For the manufacture of magnesia-silicate refractories used:
- fused forsterite-spinel material (slag from the production of high-carbon ferrochrome). The chemical composition of the slag, wt.%: SiO ₂ 32.5; MgO 45.0; Al ₂ O ₃ 17.1; Cr ₂ O ₃ 3.8; CaO 1.1; Fe ₂ O ₃ 0.4;
- sintered periclase powder with a content, wt.%: MgO 92.2; CaO 2.6; SiO ₂ 3.3; Fe ₂ O ₃ 1.9;
- chromite with a content, wt.%: Cr ₂ O ₃ 38.4; Fe ₂ O ₃ 18.7; SiO ₂ 6.1; Al ₂ O ₃ 14.1; MgO 14.1;
- scrap periclase-spinel refractories with a content, wt.%: MgO 61.2; Cr ₂ O ₃ 16.4; SiO ₂ 5.9; Fe ₂ O ₃ 7.6; Al ₂ O ₃ 5.8; CaO 2.9.

The fused forsterite-spinel material of the fraction of 2-0 mm was mixed with a finely ground component of the fraction of less than 0.063 mm in the form of a mixture of chromite and sintered periclase powder in the ratios, wt.%: 40:60; 50:50 and 60:40 or finely ground crowbar of periclase-spinel products. The ratio of components in the mixture are presented in table. 1. The mixture was moistened with a solution of lignosulfonate with a technical density of 1.22 g / cm ³ in an amount of 5-6 wt.% (In excess of 100%). From the resulting mixture was pressed products under a pressure of 80 N / mm ² , which were then dried and calcined at a temperature of 1380 ^o C.

 The phase composition of the obtained magnesia-silicate refractories, determined by petrographic analysis, is presented in table. 2, which also shows the properties of refractories.

 The open porosity, compressive strength, and temperature of the onset of deformation under load were determined by standard methods.

 Abrasion of magnesia-silicate refractories at high temperature was determined by the method described in Art. V.N. Boricheva et al. "Installation for determining the abrasion and friction coefficient of refractories at high temperatures" (J. "Refractories", 1987, 1, p. 44-46).

Tests of cylindrical samples of compositions 1-5 with a diameter of 25 and a height of 50 mm were carried out at a temperature of 1200 ^o C. Abrasion of the samples was evaluated by the relative coefficient of abrasion To _source. at a temperature of 1200 ^o C. In this case, K _East. = 1.0 was adopted indicator of the most resistant to abrasion of the refractory composition 2.

To determine the effect of scale on the abrasion of magnesia-silicate refractories at high temperature, cylinders 12 mm of the same diameter, pressed from finely ground scale, were placed on samples of refractories of compositions 2 and 5 with a diameter of 25 and a height of 50 mm. Samples prepared in this way were subjected to heat treatment at a temperature of 1100 ^o With exposure at a final temperature for 180 hours

As a result of the petrographic analysis of the samples after heat treatment, a significantly more intense (up to 25 mm deep) saturation of the known refractory with iron oxide was established compared with the proposed one. In this case, an increase in porosity and a decrease in the strength of the changed zone are observed (Table 3). The degree of abrasion at a temperature of 1200 ^o C for samples of refractories after interaction with scale was determined by the above method. Values of K ^app _. are specified in tab. 2 and 3.

 According to the table. 2, the proposed refractory (compositions 1-4) at higher rates of strength and the temperature of the onset of deformation under load is characterized by a significantly (45-73%) lower abrasion at high temperature compared to the known refractory composition 5, and in the presence of scale more than 2 times.

 Thus, the magnesia-silicate refractory according to the invention can be successfully applied in the hearths of heating metallurgical furnaces, the lower structure of open-hearth furnaces, and the lining of the loading zones of rotary and shaft kilns.

 Along with expanding the scope of refractories based on industrial raw materials, the use of the invention will also improve the ecology of the environment.

Claims (1)

Magnesia-silicate refractory, including forsterite, aluminum-magnesium spinel, periclase and monicellite, characterized in that it additionally contains magnesia-chromium-iron spinel with the composition Mg (Cr, Al, Fe) ₂ O ₄ in the following ratio of mineral phases, wt. %:
Forsterite - 43-62
Aluminum Magnesium Spinel - 14-22
The specified spinel - 12-20
Periclase - 4-11
Monticellit - 1-4

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