RU2643534C1 - Briquet for producing silicon with restorative melting - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: briquet contains microsilica, carbon-containing raw materials, woodworking industry waste and binder. As a carbonaceous raw material, the briquette contains shale dust, wood waste is wood dust, and molasses - as a binder.

EFFECT: producing a briquette with a high content of microsilica in the briquette, increasing its reactivity, reducing waste in the production process.

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Description

The invention relates to the field of silicon production, in particular to the production of silicon by reductive melting from quartzite-containing materials.

The known composition of the charge for the production of pure silicon (RF patent No. 2333889, publ. September 20, 2008), comprising a two-component molded charge, the first component is a quartz-containing briquettes having a main particle size of 10 to 90 mm, the second component is carbon-containing briquettes having the main particle size is from 10 to 70 mm.

The disadvantages of the composition is the lack of a binder in the composition of the carbon-containing briquette, as well as the use of a quartz-containing mixture of various particle size distribution.

The known composition of the charge for the production of silicon and the method of preparing the molded material for the production of silicon (RF patent No. 2151738, publ. 06/27/2000), including siliceous material in the form of dust from gas filters during the production of silicon, the reducing agent is petroleum coke. On the formation of briquettes before pressing serves the mixture of the following composition, wt. %: petroleum coke 55-70, dust of gas purification electrostatic precipitators of silicon production 25-50, alkaline binder 3-5 (10-15% aqueous solution of sodium alkali) and form material with a particle size of 6 to 50 mm.

The disadvantages of this composition is the low reactivity of the charge mixture and the low content of dust in the briquette dust of electrostatic precipitators of silicon production. The use of a 10-15% aqueous solution of sodium alkali as a binder does not give the briquettes the necessary strength.

The known composition of the briquetted mixture to obtain technical silicon (RF patent No. 2036144, publ. 05.27.1995), including silica-containing raw materials, quartz sand, lignin and petroleum coke in the following ratio of components, wt. %: silica sand 30-50; hydrolysis lignin 45-60; petroleum coke 5-10.

The disadvantages of the known composition are the low reactivity of the mixture due to the low content of petroleum coke in the briquette.

Known briquetted mixture for silicon and the method of its preparation (RF patent No. 2528666, publ. 05.27.2014), adopted as a prototype, including: microsilica not more than 20% and waste from the grain and / or wood processing industry as carbon-containing raw materials of plant origin , lignin is used as a binder.

The disadvantages of the composition is the low content of microsilica in the mixture, which reduces the reactivity of the briquette due to the content of a large amount of uncompensated carbon. Also, the low reactivity of the mixture is explained by the use of oat husks as a reducing agent; the use of lignin as a binder does not give briquettes the necessary strength.

The technical result of the invention is to obtain the composition of the briquetted mixture to obtain silicon with a high content of microsilica in the briquette and an increase in its reactivity, as well as a decrease in the waste content in the production process.

The technical result is achieved in that the briquette contains shale dust as a carbon-containing raw material, wood dust as waste from the woodworking industry, and molasses as a binder in the following ratio of components, wt. %:

shale dust 20-25 wood dust twenty molasses 10 microsilica rest

The inventive composition of the briquetted mixture for silicon includes the following components, wt. %:

shale dust 20-25 wood dust twenty molasses 10 microsilica rest

When the content in the briquette microsilica up to 50 wt. % there is an increase in the activity of the mixture, since the value approaches the optimum ratio between the mineral and carbon components of the mixture. With a higher content of microsilica - depletion of the charge with carbon begins and the efficiency of the recovery processes decreases. With a mass fraction of microsilica equal to from 20 to 35%, briquettes have high strength, but significantly less activity, since they contain a lot of uncompensated carbon.

Application of 20 wt. % of wood processing industry waste, such as wood dust, is necessary for faster chemical interaction of microsilica with carbon. In addition, the proportionality of dust particles and microsilica provides the maximum contact number and provides the possibility of rational mixing with a uniform distribution of components in the briquette. The content of wood dust in the mixture is less than 10 wt. % does not allow to dispose of it in sufficient quantities, the content of more than 20 wt. % reduces the strength and regenerative ability of briquettes.

Use as a reducing agent from 20 to 25 wt. % shale dust provides an increase in the reducing ability of the briquette due to the increase in the calorific value of the mixture. The content of shale dust in the mixture is less than 20 wt. % reduces the regenerative ability of briquettes. Also, the use of shale dust is explained by the fact that during pressing, a mineral component is released from the surface of the shale, which provides a cohesion effect between the particles, so the briquettes acquire the necessary mechanical strength.

Using 10 wt. % molasses as a binder provides satisfactory mixing of the powders, and also gives the pressed briquettes the necessary mechanical strength.

The specified composition of the mixture covers those mass fractions of the components at which the necessary strength of the briquettes is achieved and a high activity of the mixture is ensured.

Preparation of the mixture is as follows. At the first stage, microsilica, shale and wood dust powders are mixed to a homogeneous mass, and molasses is added to the mixer with mixing.

After mixing, briquettes of a cylindrical shape are pressed. The density of the briquettes is ensured by pressing pressure, which increases the surface contact area between the particles of microsilicon and shale, as well as wood dust. After pressing, the obtained silicon briquettes are loaded into the furnace and subjected to annealing. The obtained briquettes are introduced as a raw material additive to the main charge during the reduction smelting of silica-containing materials in arc or electrothermal furnaces.

As the main component of the briquette mixture, microsilica was used - silicon production waste provided by CJSC “Group of Companies“ Titan ”.

Example 1. 60 g of shale dust is mixed with 60 g of wood dust and 150 g of microsilica and stirred for 10 minutes, then 0.05 L of molasses is added and stirring is continued for 30 minutes until a homogeneous composition is obtained, the resulting mixture is pressed and annealed at at a temperature of 200 ° C for 45 minutes The obtained briquettes are introduced as a raw material additive to the main charge during the reduction smelting of silica-containing materials in arc or electrothermal furnaces.

Example 2. 75 g of shale dust is mixed with 60 g of wood dust and 135 g of microsilica and mixed for 15 minutes, then 0.06 L of molasses is added and stirring is continued for 25 minutes until a homogeneous composition is obtained, the resulting mixture is pressed and annealed at temperature of 225 ° C for 45 minutes The obtained briquettes are introduced as a raw material additive to the main charge during the reduction smelting of silica-containing materials in arc or electrothermal furnaces.

Example 3. 65 g of shale dust is mixed with 60 g of wood dust and 145 g of microsilica and mixed for 15 minutes, then 0.04 L of molasses is added and stirring is continued for 35 minutes until a homogeneous composition is obtained, the resulting mixture is pressed and annealed at temperature of 250 ° C for 45 minutes The obtained briquettes are introduced as a raw material additive to the main charge during the reduction smelting of silica-containing materials in arc or electrothermal furnaces.

It was found that a briquetted mixture for silicon production, containing microsilica as the base, shale dust as a carbon reducing agent, wood dust as a waste from the woodworking industry, and molasses as a binder, increases the reactivity of the charge and improves the quality of the resulting silicon, and also reduces the cost of metallurgical silicon due to the involvement of waste in the production process while reducing environmental stress.

The composition of the briquetted mixture to obtain silicon has a high reducing ability, and the resulting briquettes have the necessary strength due to the optimally selected composition of the mixture. The use of briquettes of the proposed composition can improve the technical and economic indicators of the process in connection with an increase in the involvement of waste (microsilica, shale and wood dust) in production, as well as improve the environmental situation while reducing the amount of waste sent to sludge fields.

Claims (2)

A briquette for producing silicon containing microsilica, carbon-containing raw materials, wood processing industry waste and a binder, characterized in that it contains shale dust as a carbon-containing raw material, wood dust as wood processing waste, and molasses as a binder in the following ratio components, wt. %: shale dust 20-25 wood dust twenty molasses 10 microsilica rest