RU2699090C1 - Method of producing high-alumina cement - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to production of high-alumina cement, in particular to production thereof in complex use of products of combined wasteless dressing of low-quality bauxites. In the method of producing high-alumina cement, involving mixing bauxite, coke, scrap metal and limestone with obtaining a crude mixture, during melting of which there formed is cast iron and alumina slag – clinker of alumina cement, crude mixture contains high-alumina autoclave concentrate – a product of chemical enrichment in a autoclave of bauxite which is not burnt with content of pyrite and silica, alumina and anthracite AM at the following ratio of components, wt%: high-alumina autoclave concentrate – 40–65, alumina – 5–20, anthracite AM – 0.9, metal scrap – 4, lime is the rest, and the raw mixture is melted in an electric arc furnace at temperature of 1,450 °C.EFFECT: possibility of using bauxite with high content of harmful impurities, obtaining high-alumina cement with high early strength and stability during long-term hardening of cement stone.1 cl, 4 dwg

Description

The invention relates to the production of high-alumina cement, in particular to their production in the integrated use of products of combined waste-free enrichment of pyritized high-siliceous boehmite-kaolinite bauxite.

Known methods for producing high alumina cements by sintering a calcareous component with alumina [IV Kravchenko and others. Chemistry and technology of special cements. M .: Stroyizdat, 1979], which are based on high-temperature (above 1450 ° C) sintering of the starting materials and are characterized by low reactivity of the raw material mixture.

A known mixture for producing alumina cement, containing ferruginous bauxite, limestone, iron scrap and coke, during blast furnace smelting of which iron is formed, which accumulates in the lower part of the hearth, and the melt of alumina slag - clinker of alumina cement located above it [Volzhensky A.V., Burov Yu.S., Kolokolnikov BC Mineral binders. - M., 1973, p. 446-449].

Known mixture for producing alumina cement, including, by weight. %: bauxite 15-25, limestone 5-15, metal shavings 22-25, coke 28-30 and mine rock from the extraction of bauxite 10-25, during blast furnace smelting of which iron and alumina slag is formed - clinker of alumina cement [A.S. RU No. 1541265, publ. 02/07/1990].

The closest in technical essence and the achieved result to the proposed method for producing high alumina cement should be considered a mixture for producing alumina cement, including bauxite, limestone, a metal component, coke containing manganese limestone with a manganese content of 6-15 wt. % and a metal component in the form of scrap in the following ratio of the components of the charge, together crushed to a particle size of 1-3 mm, mass. %: bauxite 45-52, coke 0.7-0.8, scrap metal 5-10, limestone - the rest [AS.RU No. 2 473 478 The mixture to obtain alumina cement, publ. 01/27/2013. Bull. Number 3. C1. (prototype)], which is selected as a prototype.

A significant disadvantage of the known charges and the selected prototype is that a sufficiently high sulfur and silica content when using low-quality bauxite leads to significant losses of the basic physicochemical and physico-mechanical properties of the charge in the process of smelting high-alumina clinker.

Sulfur in a calcium-aluminum raw material mixture is a highly undesirable impurity. During heating in a furnace, sulfur contained in the mixture in the form of sulfides is oxidized to sulfur dioxide and eventually forms a number of sulfates. Even with low sulfur contents in the feed, the sulfate content in the aluminate compounds gradually accumulates until it reaches the maximum concentration. This is due to the fact that the formed metal sulfates do not decompose and do not react with the components of the charge.

The problem arises in the process of obtaining high-alumina cement from a raw mix, in the composition of which bauxite is substandard in terms of sulfur and silica content. During heating in the furnace from the sulfur, silica and iron compounds contained in the mixture, low-melting double and triple compounds are formed, which negatively affect the physicochemical and physicomechanical properties of calcium-aluminum clinker, after crushing and grinding of which the final product is obtained.

The problem in the method of producing high alumina cement is solved by the fact that in the process of melting the raw material mixture, high alumina autoclave concentrate, alumina and AM anthracite are used.

The technical result is achieved due to the effective removal of sulfur from pyritized high-silica bauxite, during firing in a vapor-air atmosphere, removal of silica from calcined bauxite, during chemical enrichment in an autoclave, [Patent RU No. 2611871, publ. 03/01/2017. Bull. Number 7. C2], removal of iron from high-alumina slag, in the process of electric arc smelting of autoclave concentrate and a non-deficient, relatively cheap reducing agent - anthracite of the AM brand, while cast iron is additionally smelted.

The removal of sulfur, silica and iron from the raw material mixture during the production of high alumina cement helps to increase the physicochemical and physicomechanical properties of the final product.

At the same time, with the removal of sulfur from bauxite into the gas phase during their firing in an atmosphere of water vapor, aluminum minerals are hydrated, which contributes to the chemical enrichment of calcined bauxite in an autoclave. In the process of autoclave leaching, we remove silica from the calcined bauxite, and due to the production of aluminum concentrate with a high content of alumina and an additional product - liquid glass, we significantly reduce the technical and economic indicators of raw material processing.

In a method for producing high-alumina cement, comprising mixing bauxite, coke, scrap metal and limestone, to produce a raw material mixture that, when smelted, produces cast iron and alumina slag — an alumina cement clinker, the raw material mixture contains a high-alumina autoclave concentrate — a product of non-refined chemical enrichment in an autoclave the content of pyrite and silica bauxite, alumina and anthracite grade AM, in the following ratio, wt. %: high-alumina autoclave concentrate - 40-65, alumina - 5-20, anthracite grade AM - 0.9, metal scrap - 4, the rest is lime, and the raw material mixture is melted in an electric arc furnace at a temperature of 1450 ° С.

For the preparation of raw mixes 1, 2 and 3, lime and anthracite grade AM are used, for the raw mix 4 (according to the prototype) limestone and coke. The chemical composition of lime, wt.%: (Per calcined substance) CaO _act. -86.40; CaO is _connected. - 2.60; SiO ₂ - 3.60; CO ₂ - 2.00; others - 5.40; The chemical composition of limestone, wt. %: (per calcined substance) CaO -54.2; CO ₂ 42.6; SiO ₂ - 1.3; others - 1.9;

The chemical composition of coke, wt. %: Al ₂ O ₃ - 30; CaO-15; SiO ₂ - 45; Fe ₂ O ₃ - 10;

The chemical composition of anthracite grade AM, wt. %: C - 88.0; Ash - 8.0; Volatile - 2.5; Moisture - 1.5. Anthracite ash: Al ₂ O ₃ - 20.0; SiO ₂ 45.0; FeO -35.0.

In FIG. 1 shows the composition of the raw mix, and in FIG. 2. - chemical compositions of the components of the raw mixes.

All constituent components of the raw material mixture are crushed to a fraction of 5 mm, then milled to a particle size of 1-3 mm, after which each component is weighed in accordance with the composition of the mixture and mixed in a mixer until a homogeneous mass is obtained. Melting of raw mixes is carried out in an electrode furnace at a temperature of 1450 ° C, then the melt - high alumina slag is poured into the molds, after cooling, its clinker is crushed and milled to 3500 cm / g, and the properties of the obtained high alumina cement are determined.

From the bottom of the furnace, the molten iron is poured into sand forms.

The chemical composition of cast iron melted from a mixture of 1-4,%:

1. 3.57 - Si; 93.07 - Fe; 1.84 - C; 1.52 - Other.

2. 3.80 - Si; 93.09 - Fe; 1.84 - C; 1.27 - Other.

3. 3.98 - Si; 93.11 - Fe; 1.84 - C; 1.07 - Other.

4. 15.68 - Si; 81.82 - Fe; 1.62 - C; 0.88 - Other.

Tests of the obtained high alumina cement are carried out according to GOST No. 969-91 on samples - beams 4 × 4 × 16 cm.

The above chemical compositions are preferred, but fluctuations in compositions of up to 10% are allowed both in the direction of decreasing and increasing, depending on the feedstock used at a particular enterprise.

In FIG. 3. shows the brand of cement and the chemical composition of clinker obtained from the raw mix 1, 2, 3 and 4, and in FIG. 4. - physical and mechanical properties of cements.

An analysis of the experiments shows that the use, in the process of producing high-alumina cements, of products of combined waste-free enrichment of sub-high sulfur and silica content of high-alumina bauxite, improves the physicochemical and physicomechanical properties of the resulting products

- high alumina cements and pig iron. Short-term hardening and a set of high strength VHC II and VHC I, as well as increased refractoriness are observed.

An analysis of the experiments carried out on the prototype shows that the use of high-alumina bauxite in sub-sulfur and silica in the preparation of cement results in a decrease in the content of monoaluminate and dialuminate (CA + CA ₂ ) in the clinker, the compressive strength after three days and the cement fire resistance. The chemical composition of such cement corresponds to the brand of HC I.

The technical result of the invention:

- the resulting clinkers are characterized by the complete formation of the final phases CaO * Al ₂ O ₃ and CaO * 2Al ₂ O ₃ , meet 100% completion of the clinker formation processes and satisfy the requirements for the physicomechanical and physicochemical parameters of cement grade VHC II and VHC I.

- the clinkers obtained according to the prototype are characterized by incomplete formation of the final phases CaO * Al ₂ O ₃ and CaO * 2Al ₂ O ₃ , have a high content of silica and do not meet the requirements for physico-mechanical and physico-chemical parameters of the VHC.

Industrial applicability lies in the possibility of involving pyritized high-siliceous boehmite-kaolinite bauxite in the production of high-alumina cement and the production of cements of the VHC II and VHC brands I.

The proposed method for producing high-alumina cement allows us to solve the problem of increasing physicochemical and physicomechanical properties, which are directly dependent on the high content of pyrite, silica and iron in the final product - high-alumina clinker and increase the efficiency of the integrated use of enrichment products of substandard bauxite.

Claims (1)

A method of producing high alumina cement, comprising mixing an alumina component, scrap metal and a calcium component to produce a raw material mixture, the smelting of which produces cast iron and clinker of high alumina cement, characterized in that the raw material mixture as a high alumina component contains a high alumina autoclave autoclave calcined bauxite and alumina, as a calcium-containing component, lime and ratsit mark AM in the following ratio, wt. %: high-alumina autoclave concentrate - 40-65, alumina - 5-20, anthracite grade AM - 0.9, metal scrap - 4, the rest is lime, and the raw material mixture is melted in an electric arc furnace at a temperature of 1450 ° C, then poured into molds the melt of high alumina clinker, after its cooling, the clinker is crushed and subjected to grinding to 3500 cm ² / g to obtain high alumina cement.

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