RU2740994C1 - Carbon reducing agent for production of technical silicon and method of its production - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to production of briquettes from carbon material used as reducing agent for production of technical silicon and other metallurgical processes. Invention relates to a briquetted carbon reducing agent based on carbon material and binder for producing technical silicon, in which the carbon material used is brown coal fines with a fractional composition of 0-10 mm, and binder used is 3-10% aqueous solution of alkali and molasses and / or pyrolysis liquid with coke residue of not less than 7 wt%, with the following ratio of components, wt%: coke breeze of brown coal of not less than 60, aqueous solution of alkali 10-20, molasses and / or pyrolysis liquid 10-20. Invention also relates to a method of producing said carbonaceous reducing agent, which involves mixing the binder with carbon material, molding the mixture and drying the formed briquette. First, brown coal coke is mixed with 3-10% aqueous solution of alkali, then molasses and / or pyrolysis liquid is added with coke residue of not less than 7 wt%, components are mixed for at least two minutes, after mixing all components briquette mass is pressed into briquettes under pressure of not less than 50 MPa with further drying at temperature of 120-170°C for 40-60 minutes and formation of briquettes of carbon reducing agent.EFFECT: technical result is higher mechanical and thermal strength of briquette.3 cl, 7 ex

Description

Technology area

The invention relates to the field of technology for producing briquettes from carbon material, used as a reductant to obtain technical silicon and other metallurgical processes.

State of the art

Known fuel briquettes and a method for its production (patent RU No. 2130047, C10L 5/02, C10L 5/44, C10L 5/12, C10L 5/14, publ. 05/10/1999), including mixing crushed solid fuels with a binder on the basis of oil refining waste - oil sludge and / or used machine oil, briquetting of the mixture and subsequent drying of the briquette. Additionally, components selected from the group including, wt% based on the briquetted mixture, are added to the binder: lignosulfonate or molasses - 2-7, and / or dehydrated activated sludge - 3-8, and / or clay - 3-10, and / or paraffin or paraffin gas 3-6% with the following ratio of components in the briquette, wt. %: binder - 10-23, crushed solid fuels, selected from the group: sawdust, peat, dehydrated bird droppings, dewatered manure, coke or coal fines, coal sludge, lignin or their mixtures - up to 100. Briquetting is carried out at a pressure of 1- 30 MPa, briquette drying - at a temperature of less than 300 ° C. Before mixing, the components of the binder are heated to 60-80 ° C or mixed with heating to 60-80 ° C. The solid fuel is premixed with half of the sludge or treated machine oil and then the remaining binder components are added.

The disadvantage is that the briquettes obtained using the described method have insufficient strength due to the inclusion in the raw material, for example, sawdust, manure, bird droppings, and the inclusion of clay in the binder composition can adversely change the composition of the mineral part of the briquette.

A known method of producing briquetted fuel (patent RU No. 2473672, C10L 5/02, C10L 5/14, C10L 10/02, publ. 27.01.2013), which consists in joint grinding of carbon-containing material and mineral binder to a particle size of no more than 5 mm, adding a hydrophobizing modifier and water to the resulting composition, followed by mixing with the addition of a strengthening modifier. The resulting mass is pressed into briquettes under a pressure of 20-200 MPa and the resulting briquettes are dried at 100-250 ° C. The components used are carbon-containing material - medium-temperature lignite coke of the original granulometric composition, mineral binder - subcoal siltstone, strengthening modifier - 3% aqueous solution of polyvinyl alcohol (PVA) or aqueous solution of 10% flour paste, hydrophobizing modifier - M100 fuel oil , water, with the following content of components, wt. %: mineral binder 1-10; hardening modifier 1-30; hydrophobizing modifier 1-10; water 3-30; carbonaceous material - the rest.

Briquettes obtained by the described method have insufficient strength and water resistance.

Known charge for the production of silicon and a method of preparing a molded material for the production of silicon (patent RU No. 2151738, C01B 33/025, publ. 06/27/2000), aimed at processing silicon, the essence of which is a method of obtaining one of the components of the charge. The charge for silicon production includes quartzite, wood chips, petroleum coke, charcoal, finely dispersed silica and an alkaline binder, contains fine silica in the form of dust from electrostatic precipitators for gas cleaning of silicon production with the following ratio of components, wt%: quartzite 35-45; wood chips 19-26; petroleum coke 11-15; charcoal 7-10; dust from electrostatic precipitators for gas cleaning of silicon production 4,5-11; alkaline binder 0.5-1.3, and part of the silica-carbon-containing charge is presented in the form of a preformed material in an amount of 10-30% by weight of the charge. The preparation of its component, a molded material, includes mixing a finely dispersed silica-containing material with a carbon-containing reductant and an alkaline binder, molding and drying, as a silica-containing material, the dust of electrostatic precipitators for gas cleaning of silicon production is used, the reductant is petroleum coke, a charge of the following composition is used for molding, wt%: coke 55-70, dust from electrostatic precipitators for gas cleaning of silicon production 25-50, alkaline binder 3-5 and molded material with a size of 6-50 mm and dried to a moisture content of 6-8%, in addition, petcoke containing a fraction of not more than 8 mm is fed for molding , in an amount of at least 70 wt.%, and a 10-15% aqueous solution of sodium alkali is fed for mixing.

In this technical solution, due to the high content of volatile components in the briquettes obtained from the briquetted mixture, part of the silicon-containing raw material in the form of a finely dispersed fraction does not participate in the technological process and is carried away from the charge with flue gases, which reduces the reactivity of the carbon reducing agent and reduces the quality of the resulting metal silicon from ore raw materials.

A known method of obtaining fuel briquettes (AS No. 1546469, C10L 5/10, publ. 28.02.1990), containing, wt.%: Coke breeze 34 - 36; sawdust 1.5 - 2.5; liquid glass 6.5 - 7.4; petroleum bitumen 2.5 - 3.5; anthracite fines - the rest.

The disadvantage of such a known composition is the presence of petroleum bitumen, which requires heating before mixing to a temperature of 220 - 250 ^o C and steaming the prepared briquette mass with live steam at a temperature of 210 ^o C, which greatly complicates the briquetting process, making it energy-intensive. All this, taking into account the use of expensive liquid glass (up to 7.4 wt.%), Increases the cost of briquettes.

Known coal briquette with increased strength, as well as a method for its manufacture (patent RU No. 2224007, С10L 5/02, С10L 5/06, publ. 12.12.2001). Briquette with increased initial strength and consisting of 100 wt.h. coal fines, 1-5 parts by weight quicklime and 7-15 wt.h. molasses. The briquette has a crushing resistance of at least 70% and a dust formation rate of not more than 20% and is suitable for use in the smelting-reduction process of iron production. In the briquette, coal fines contains from 6 to 15 wt% moisture. In the briquette, quicklime contains particles with a size of not more than 1 mm, and the proportion of particles with a size of not more than 0.3 mm is not less than 50% by weight. The method of making such briquettes includes the operations: mixing 1-5 weight.h. quicklime with 100 wt.h. coal fines and mixture holding; mixing 7-15 parts by weight molasses with a matured mixture and their mixing and direct formation of the mixed mixture in order to obtain briquettes. A method in which fine coal contains from 6 to 15 wt% moisture. A method in which the quicklime contains particles with a size of not more than 1 mm, and the proportion of particles with a size of not more than 0.3 mm is not less than 50% by weight. A method in which the aging is carried out from 2 minutes to 2 hours to convert the quicklime into slaked lime. A method in which mixing is carried out for 2-50 minutes to increase the speed of hardening. A method in which no heating and drying operation is performed after direct forming.

The disadvantage of this invention is that to achieve increased strength, the binding capacity of calcium saccharate, formed as a result of a chemical reaction between quicklime and molasses, is used. However, the chemical reaction between quicklime and molasses is limited by the short residence time in the system. Quicklime quickly reacts with moisture and molasses, promotes the hardening of the ingredients, which prevents the quicklime from evenly spreading through the mixture, this reduces mechanical strength and makes storage and transportation difficult.

The closest technical solution and the achieved result is a method for producing a metallurgical briquette (patent RU No. 2638260, C10L 5/00, C10L 5/10, C10L 5/14, C10L 5/22, publ. 12/15/2017), which describes a method for producing a briquette, including mixing the initial components - a carbon-containing material, a binder and water, pressing the briquette mixture and drying the formed briquette, while a two-component binder containing resin and flour in a ratio from 0.5: 1 to 2: 1 is used as a binder, where the initial components are taken in the following ratio, wt. %: carbon-containing material - not less than 50; two-component binder - 8–40; water with a temperature of 1 to 99 ° C - the rest.

The disadvantage of the invention is the high content of phosphorus in the briquette, which affects the grade of silicon due to the use of a binder based on flour, as well as the use of resins containing toxic and phenol-containing substances.

Disclosure of the essence of the invention

The objective of the invention is to create effective carbon briquettes-reducing agents based on brown coal coke breeze, used for the production of technical silicon, and improving the technical and economic performance of the smelting process.

The technical result is to increase the mechanical and thermal strength of the briquette.

The technical result is achieved due to the fact that in the briquetted carbon reductant, coke breeze of brown coal with a fractional composition of 0-10 mm is used as a carbon material, and a 3-10% aqueous solution of alkali and molasses and / or pyrolysis liquid is used as a binder with coke residue of at least 7 wt.% with the following ratio of components, wt. %:

brown coal coke breeze not less than 60,

aqueous solution of alkali 10-20,

molasses and / or pyrolysis liquid 10-20.

The technical result is also achieved due to the fact that in the method of producing a carbon reducing agent, including mixing a binder with a carbon material, pressing the mixture and drying the formed briquette, it is new that brown coal breeze is first mixed with a 3-10% aqueous solution of alkali , then add molasses and / or pyrolysis liquid with a coke residue of at least 7 wt.%, the mixing of the components is carried out for at least two minutes, after mixing all the components, the briquette mass is pressed into briquettes under a pressure of at least 50 MPa with further drying at a temperature of 120 -170 ⁰ С for 40-60 minutes and the formation of a briquette of a carbon reducing agent.

The method is complemented by special cases of its execution.

Potassium or sodium alkali is used as an aqueous solution of alkalis.

Implementation of the invention

A distinctive feature of the present invention is the use of carbon briquettes based on coke breeze of brown coal as reducing agents, with the addition in a certain order of binding components consisting of an aqueous solution of alkali, molasses (a product of sugar beet or cane processing) and / or pyrolysis liquid (heavy pyrolysis resin oil, resin of ablative pyrolysis of wood, sediment resin of charcoal) with a coke residue of at least 7 wt. % responsible for mechanical and thermal strength.

The method involves mixing primarily brown coal coke breeze with a fractional composition of 0-10 mm with a 3-10% aqueous solution of alkali (potassium or sodium alkali), then adding molasses and / or pyrolysis liquid with coke residue of at least 7 wt. % with stirring for at least 2 minutes, then briquetted under a pressure of at least 50 MPa, drying is carried out at a temperature of 120-170 ⁰ С for 40-60 minutes.

When molasses and / or pyrolysis liquid interacts with an aqueous alkali solution, an acid neutralization reaction occurs, while the viscosity of the binding components decreases, which increases their adhesive properties. At an alkali concentration of less than 3%, the structural strength of briquettes decreases, at a solution concentration of more than 10%, the structural strength of briquettes does not increase significantly.

When adding a pyrolysis liquid with a coke residue of less than 7 wt%, the thermal strength of the briquette decreases.

When briquetting under a pressure of less than 50 MPa, the mechanical strength of the briquette decreases.

At a drying temperature below 120 ⁰ С, it is necessary to increase the duration of the drying process, which affects productivity, and at temperatures above 170 ⁰ С, the briquette ignites in an oxidizing atmosphere.

In practice, the use of binding components in the form of molasses and pyrolysis liquid when briquetting carbon-containing materials requires their preheating before mixing, this is necessary to reduce the viscosity of materials, improving the rheological properties of the charge for briquetting. The use of weak alkali solutions does not require preliminary heating of the binding components.

During drying, the organic binder is seized, forming a strong framework, which ensures the mechanical strength of the briquette during transportation and transfer of material along technological processing. When a briquette hits, for example, on the top of an ore-thermal furnace, at high temperatures, the pyrolysis liquid begins to coke, forming bridges between particles, preventing the briquette from falling apart in the ore-thermal furnace, which ensures the completeness of the process of carbothermal reduction of silicon and prevents the removal of small particles of the reducing agent into the gas duct furnaces and its overconsumption in the production of technical silicon.

Examples of implementation of the method

Example 1 . 75 wt.% Of brown coal coke breeze of fraction 0-10 mm is first mixed with 10 wt.% Of 5% potassium alkali solution and stirred for at least two minutes, then molasses is added in an amount of 15 wt% and stirred for two minutes, then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ⁰ C for 60 minutes.

The resulting briquette has an abrasion strength of 90%, a drop strength of 95%, and a hot strength of 1.8 MPa.

Example 2 . 75 wt% coke breeze of brown coal fraction 0-10 mm is first mixed with 10 wt% 10% potassium alkali solution and stirred for at least two minutes, then pyrolysis liquid is added in the amount of 15 wt% and stirred for two minutes , then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ⁰ C for 60 minutes.

The resulting briquette has an abrasion strength of 95%, a drop strength of 98%, and a hot strength of 3.7 MPa.

Example 3 . 72 wt% of brown coal coke breeze of fraction 0-10 mm is first mixed with 10 wt% 3% sodium alkali solution and stirred for at least two minutes, then molasses is added in the amount of 10 wt% and pyrolysis liquid in the amount of 8 wt% and stirred for two minutes, then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ⁰ C for 60 minutes.

The resulting briquette has an abrasion strength of 96%, a drop strength of 99%, and a hot strength of 5.2 MPa.

Example 4 .

A briquette is made in accordance with example 1, 60 wt.% Of brown coal coke breeze of fraction 0-10 mm is first mixed with 20 wt.% 5% potassium alkali solution and stirred for at least two minutes, after which molasses is added in an amount of 20 wt. % and stirred for two minutes, then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ^° C for 60 minutes.

The resulting briquette has an abrasion strength of 98%, a drop strength of 99%, and a hot strength of 2.1 MPa.

Example 5 .

60 wt.% Of brown coal coke breeze of fraction 0-10 mm is first mixed with 20 wt.% 10% potassium alkali solution and stirred for at least two minutes, then pyrolysis liquid is added in an amount of 20 wt% and stirred for two minutes , then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ⁰ C for 60 minutes.

The resulting briquette has an abrasion strength of 97%, a drop strength of 98%, and a hot strength of 6.7 MPa.

Example 6 .

A briquette is made in accordance with example 1, 70 wt.% Of brown coal coke breeze of fraction 0-10 mm is first mixed with 20 wt.% 5% potassium alkali solution and stirred for at least two minutes, after which molasses is added in an amount of 10 wt % and stirred for two minutes, then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ^° C for 60 minutes.

The resulting briquette has an abrasion strength of 95%, a drop strength of 98%, and a hot strength of 1.4 MPa.

Example 7 .

70 wt.% Of brown coal coke breeze of fraction 0-10 mm is first mixed with 20 wt.% 10% potassium alkali solution and stirred for at least two minutes, then pyrolysis liquid is added in an amount of 10 wt% and stirred for two minutes , then briquetted under a pressure of 50 MPa, dried at a temperature of 150 ⁰ C for 60 minutes.

The resulting briquette has an abrasion strength of 94%, a drop strength of 98%, and a hot strength of 3.2 MPa.

The analysis of the results obtained shows that according to the proposed method, briquettes with increased mechanical and thermal strength were obtained. With an increase in the content of alkali with molasses, the structural strength of the briquette increases, with an increase in the alkali with pyrolysis liquid, the thermal strength of the briquette increases.

When combining binders in the form of a weak alkali solution, molasses and pyrolysis liquid, maximum results in terms of strength characteristics are obtained.

Claims (4)

1. Briquetted carbon reductant based on carbon material and a binder for the production of technical silicon, characterized in that as a carbon material used coke breeze of brown coal with a fractional composition of 0-10 mm, and as a binder used 3-10% aqueous solution alkali and molasses and / or pyrolysis liquid with a coke residue of at least 7 wt.% with the following ratio of components, wt. %: brown coal coke breeze not less than 60 aqueous alkali 10-20 molasses and / or pyrolysis liquid 10-20 2. A method for producing a carbon reductant according to claim 1, including mixing a binder with a carbon material, pressing the mixture and drying the formed briquette, characterized in that first coke breeze of brown coal is mixed with a 3-10% aqueous solution of alkali, then molasses is added and / or a pyrolysis liquid with a coke residue of at least 7 wt%, mixing of the components is carried out for at least two minutes, after mixing all the components, the briquette mass is pressed into briquettes under a pressure of at least 50 MPa with further drying at a temperature of 120-170 ° C in for 40-60 minutes and the formation of a briquette of a carbon reducing agent. 3. A method according to claim 2, characterized in that potassium or sodium alkali is used as an aqueous solution of alkalis.