CZ298914B6 - Process for producing synthetic slag - Google Patents

Abstract

The manufacture of synthetic slag for e.g. steel desulfurizing comprises alumina raw material, limestone, alumina cement and water of 0.8:1 to 1.6:1 Al2O3:CaO ratio. With alumina cement 2-16 and water 2-30 per cent by weight contents agglomeration is followed by calcining at 1200-1340 degrees, yielding mainly 12Ca0.7Al2O3 (mayenite) phase.

Description

Process for producing synthetic slag

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a process for the production of synthetic slag intended primarily for the desulfurization of steel.

BACKGROUND OF THE INVENTION

The processes known to date for the production of synthetic slag generally consist in homogenizing the raw materials containing Al ₂ O ₃ and CaO, melting the mixture, cooling and milling the melt. Processes in which the mixture is agglomerated and the calcination of the agglomerates does not exceed the melting point of the mixture are also known. The advantage of these processes is low dustiness during agglomerate handling, lower energy consumption due to lower calcination temperature, elimination of melt crushing costs and especially the possibility to use for calcination even furnaces whose powder material cannot be calcined for technological reasons. In the case of agglomeration of the mixtures, it is desirable to achieve the best mechanical properties of the agglomerates, i.e. the greatest abrasion resistance.

Patent CN 1377977 discloses a process for the manufacture of synthetic slag containing 2 to 15% Al, 3 to 15% Ce, 5 to 8% Mg, 2 to 10% Ba, 20 to 50% CaO, 10 to 40% Al ₂ O ₃ , 2 to 10 10% MgO and 2 to 10% Na ₂ SiO ₂ . The slag is produced by melting the mixture of raw materials, grinding the melt into a powder, pelletizing with the addition of 3 to 8% cellulose and final firing at low temperature. The disadvantage of this production method is that the melting point of the mixture is exceeded.

JP 57207109 discloses a method for producing synthetic slag in which material is not fused to the furnace walls. The production consists of grinding and homogenization of raw materials, granulation of the mixture, consolidation of granules at a temperature below 900 ° C and final calcination of agglomerates in a rotary kiln. Synthetic slag produced according to the present invention contains 50 to 70% CaO, 10 to 40% CaF _2, and 10 to 40% CaO

30% A1 ₂ O ₃ and 3-5% of one or more of the following components: Fe ₂ O _3, SiO ₂ and Na ₂ O. A disadvantage of this process is technologically and energetically demanding process hardening agglomerates.

GB 1193391 discloses a process for producing synthetic slag containing 50 to 95 wt.

CaO and 5 to 50% FeO. The process consists in pelletizing a mixture of raw materials in which the mixture is moistened with water containing at least 7 wt. Ca (OH) ₂ , solidification of pellets by air or CO ₂ (lime carbonation) and calcination of pellets in a shaft furnace at a temperature higher than 1000 ° C. A disadvantage of this method is the low binding effect of calcium hydroxide.

No publications have been found which describe a process for the production of synthetic slag based on the calcination of aluminous cement-reinforced agglomerates.

SUMMARY OF THE INVENTION

The process for producing synthetic slag is characterized by first mixing the aluminate raw material, limestone, aluminous cement and water in an Al ₂ O ₃ : CaO weight ratio of 0.8: 1 to 1.6: 1, wherein the aluminous cement content of the mixture is 2 to 16 wt. and the water content of the mixture is 2 to 30 wt%, then the resulting mixture is agglomerated and then the agglomerates are calcined at a temperature of 1250 to 1340 ° C.

Agglomerates can be prepared from the composition prepared according to the invention, which have increased abrasion resistance due to hydration in the aluminate cement mixture present.

-1 CZ 298914 B6

DETAILED DESCRIPTION OF THE INVENTION

Example 1

By homogenizing the aluminate raw material containing Al ₂ O ₃ in the form of bayerite and corundum with limestone, aluminous cement and water, mixtures with different aluminous cement proportions were prepared. As a control mixture, a mixture was prepared without the addition of aluminous cement. The mixtures 10 were agglomerated by extrusion into the shape of noodles. The abrasion resistance of the extrudates was determined 24 hours after preparation. The abrasion resistance was quantified as a percentage of the weight of dust particles resulting from the standardized mechanical stress of the agglomerates to the total weight of the agglomerates tested. Synthetic slags were identified from the extrudates prepared from all blends by calcination at 1340 ° C and identified as the dominant 12CaO.7Al ₂ O ₃ phase by X-ray diffraction analysis. The weight ratio Al ₂ O ₃ : CaO was calculated from the composition and weight of raw materials. The composition of the mixtures and the properties of the agglomerates are given in Table 1.

Table 1: Composition of mixtures and properties of agglomerates

sample no. hmoto ratio Al2O3: CaO aluminate content cement mixed [% wt.] water content in a mixture [% wt.] Tablet resistance against abrasion [% wt.] 1 1,2 0 25.8 90.0 2 1,2 2 25.7 90.9 3 1,2 4 25.5 90.4 4 1,2 7.7 28.1 84.3 5 1,2 11.5 27.8 46.5 6 1,2 15.4 27.5 40.3

Example 2

Homogenization of the alumina feedstock containing Al ₂ O ₃ in the form of bayerite and corundum with limestone, aluminous cement and water was prepared by agglomeration by compression into tablets. Synthetic slag was produced from the tablets by calcination at 1300 ° C and identified by X-ray diffraction phase analysis as the dominant phase 12CaO.7Al ₂ O ₃ . The weight ratio Al ₂ O ₃ : CaO was calculated from the composition and weight of raw materials. The composition of the mixture is shown in Table 2.

-2GB 298914 B6

Table 2: Composition of the mixture

sample no. % Al ₂ O ₃ : CaO aluminate content cement mixed [wt%] water content in a mixture [wt%] 7 0.8 9.4 10.6

Example 3

Homogenization of the alumina feedstock containing Al ₂ O ₃ in the form of bayerite and corundum with limestone, aluminous cement and water was prepared by agglomeration by compression into tablets. Synthetic slag was produced from the tablets by calcination at 1250 ° C and identified by X-ray diffraction phase analysis as the dominant phase 12CaO.7Al ₂ O ₃ . The weight ratio Al ₂ O ₃ : CaO was calculated from the composition and weight of raw materials. The composition of the mixture is shown in Table 3.

Table 3: Composition of the mixture

sample no. wt. ratio Al2O3: CaO aluminate content cement mixed [wt%] water content in a mixture [wt%] 8 1.0 9.4 12.4

Example 4

Homogenization of the alumina feedstock containing Al ₂ O ₃ in the form of bayerite and corundum with limestone, aluminous cement and water was prepared by agglomeration by compression into tablets. Synthetic slag was produced from the tablets by calcination at 1250 ° C and identified by X-ray diffraction phase analysis as the dominant phase 12CaO.7Al ₂ O ₃ . The weight ratio Al ₂ O ₃ : CaO was determined by X-ray fluorescence analysis. The composition of the mixture is shown in Table 4.

-3 CZ 298914 B6

Table 4: Composition of the mixture

sample no. wt. ratio Al ₂ O ₃ : CaO aluminate content cement mixed [wt%] water content in a mixture [wt%] 9 1.6 9.4 12.4

Example 5

Homogenization of the aluminate raw material containing Al ₂ O ₃ in the form of a Gibbsite with limestone, aluminous cement and water was prepared by agglomeration by compression into tablets. Synthetic slag was produced from the tablets by calcination at 1300 ° C and was identified by X-ray diffraction phase analysis as the dominant phase 12CaO.7Al ₂ O ₃ . The weight ratio Al ₂ O ₃ : CaO was calculated from the composition and weight of raw materials. The composition of the mixture is shown in Table 5.

Table 5: Composition of mixtures

sample no. wt. ratio AI2O3. ' CaO aluminate content cement mixed [wt%] water content in a mixture [wt%] 10 1.1 9.8 2,0

Industrial applicability

The invention is industrially applicable in the manufacture of synthetic slags intended primarily for the desulfurization of steel.

Claims (1)

Process for the production of synthetic slag, characterized in that the aluminate raw material, limestone, aluminous cement and water are first mixed in an Al ₂ O ₃ : CaO weight ratio of 0.8: 1 to 1.6: 1, wherein the aluminous cement content 2 to 16 wt. 35 and the water content of the mixture is 2 to 30% by weight, then the resulting mixture is agglomerated and then the agglomerates are calcined at a temperature of 1250 to 1340 ° C.