METHOD FOR RESOURCE RECOVERY FROM SILICON SLAG AND DEOXIDIZING AGENT FOR IRON AND STEELMAKING

Abstract

Silicon slags, which is a by-product of metallic silicon mill during producing metallurgical grade silicon, solar cell grade silicon and Ferro-silicon alloy. are processed according to the invention to small lumps and briquettes, being excellent deoxidizer for cast iron and steel in order to avoid either costly regeneration for the recovering of the valuable components or the total dumping of said silicon slags. The cost of iron and steelmaking can be reduced significantly. As an additional advantage, the particles of silicon slag in molten steel can absorb the tiny oxides from the deoxidizing reaction and purify the molten steel more quickly.

Claims

1) Deoxidizing agent for iron and steel-making makes of silicon slag: the silicon slags are processed to small lumps and briquettes, becoming excellent deoxiders for cast iron and steel

2) According to claim (1), the silicon slag is a by-product of metallic silicon mill during producing metallurgical grade silicon, solar cell grade silicon and Ferrosilicon alloys

3) According to claim (1), the silicon slag is crusted to small lumps with size of 10100 mm or as the customer demand and used as deoxidizing agent directly

4) According to claim (1), the briquette is made from the mixture of silicon slag and 340% by weight of binder. The silicon slags are are pulverized into fine particles, screened, mixed with binder, compacted into briquettes and dry in air.

5) According to claim (4), the silicon slags are pulverized into fine particles, screened so that the particle diameter is no more than 200 m, and the preferred diameter is no more than 50 m.

6) According to claim (4), the binder is water soluble silicate, and the preferred silicates are sodium silicate and potassium silicate. The weight content of silicate solution is 1040%.

Description

REFERENCE OF DRAWINGS

[0007] FIG. 1 The schematic of silicon slag processing flow

[0008] FIG. 2 The picture of small silicon slag lumps

[0009] FIG. 3 The picture of silicon slag briquettes

SUMMARY OF THE INVENTION

[0010] Compared with the actions of iron/steel slag and Ferrosilicon in molten steel, silicon slag can be treated as a composite of steel slag and deoxidizing agent, so a method for resource recovery of silicon slag and deoxidizing agent for iron and steelmaking is developed. To commercialize silicon slag economically, it is necessary to process it to small lumps with size of 10100 mm or specified by the customer first, since these small lumps can be used as deoxidizing agent directly. Therefore, the slag is adjusted to specified lump size through a process of crushing and classification. The normal size is 10100 mm or as the customer demand. It is a good substitute for FeSi alloy in steelmaking, which can reduce the steelmaking cost significantly. Then the screening residues are pulverized further to fine particles with size smaller than 200 m, mixed with water soluble silicate solution and compacted to briquettes on briquetting machine. During mixing the metallic silicon particles can react with silicate solution. It is very interesting that this reaction is an exothermic reaction, and the temperature of briquette can reach more than 70 centigrade degree, so the briquette no need further dry in furnace. The briquette is also a good substitute for FeSi alloy in steelmaking.

DETAILED DESCRIPTION OF THE INVENTION

[0011] In order to reuse silicon slags economically, it can be processed to the lump size of 10100 mm or as specified by the customer first and used as deoxidizing agent directly. Then the screened residues are pulverized further to fine particles with size smaller than 200 m, mixed with water soluble silicate solution and compacted to briquettes on briquetting machine. Of course all silicon slags can be crushed into fine particles and compacted to briquettes.

[0012] The compacted briquettes of silicon slag is prepared by first mixing together the silicon slags in fine powdered form with 3 to about 10% by weight of silicate solution. Then the obtained plastic homogeneous paste is fed to a briquetting machine, briquettes of the silicon slags are formed and subsequently dried in air. The preferred silicates are sodium silicate and potassium silicate and its weight concentration in water is from 1040%. The size of fine powders should be smaller than 200 m, and the preferred size is 150 m. It is very interesting that the metallic silicon particles can react with silicate solution during mixing and the reaction is an exothermic reaction, the temperature of briquette can reach more than 70 centigrade degree, so the briquette no need further dry in furnace.

EXAMPLE

[0013] The typical compositions of silicon slags from metallurgical silicon mill is shown in Table 1. The schematic of silicon slag processing flow is shown in FIG. 1. As illustrated in FIG. 1, the silicon slags are crushed by jaw crusher to small lumps with size of 10100 mm or as the the customer demand. After screening, the lumps are packaged and used as deoxidizing agent, the picture of these lupms is shown in FIG. 2. The residues are pulverized into fine particles by opposite roller mill, screened again so that the particle diameter is no more than 50 m. The fine particles are mixed with 5% by weight of sodium silicate solution (30% by weight) for 30 minutes and added into briquetting machine to get silicon slag briquettes with size of 1050 mm. The green briquettes are dried in air due to the exothermic reaction between metallic silicon and sodium silicate. The picture of Si slag briquettes is shown in FIG. 3.

TABLE-US-00001 TABLE 1 The typical compositions of silicon slags from metallurgical silicon mill Si (%) Fe (%) Al (%) Ca (%) C (%) S (%) P (%) others (%) 65 2 5 5 4 0.05 0.05 balance