RU2669940C1 - Method of briquetting carbon reducing agents - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention describes a method for briquetting carbon reducing agents, preferably brown coal or stone semi char (coke), comprising mixing binder materials with a semi char (coke), pressing and drying of briquettes, characterized in that, as binding materials, a combined binder comprising high-temperature and low-temperature components is used, the carbonaceous reductant is mixed with the high-temperature component, then a low-temperature component is added, at the same time, high-temperature components are used as bottoms of oil processing in the form of a pyrolysis resin or a catalytic gas oil in an amount of 25–30 wt. %, and as a low-temperature component, organic substances are used in the form of a solution of gluten or molasses in an amount of 70–75 wt. %.

EFFECT: technical result consists in increasing the mechanical and thermal strength of the briquette.

5 cl, 4 ex, 3 tbl

Description

The invention relates to the field of technology for the preparation and production of briquettes used as a reducing agent for the production of technical silicon and other metallurgical processes.

Known technical solution "Method for the preparation of molded material for the production of silicon" (patent RU 2151738, СВВ 33/025, publ. 06/27/2000), aimed at processing silicon, the essence of which lies in the method of producing one of the components of the charge. Moreover, the charge for the production of silicon includes quartzite, wood chips, petroleum coke, charcoal, fine silica and an alkaline binder, contains fine silica in the form of dust from gas purification electrostatic precipitators of silicon production in the following ratio of components, masses. %: quartzite 35-45; wood chips 19-26; petroleum coke 11-15; charcoal 7-10; dust electrostatic precipitators of silicon production 4.5-11; alkaline binder 0.5-1.3, and part of the silica-carbon-containing mixture is presented in the form of preformed material in the amount of 10-30% by weight of the mixture. The preparation of its component, the molded material, involves mixing finely dispersed silica-containing material with a carbon-containing reducing agent and an alkaline binder, molding and drying, dust of gas-purification electrostatic precipitators is used as a silica-containing material, the reducing agent is petroleum coke, a mixture of the following composition is fed to the molding, mass. %: petroleum coke 55-70, dust of gas purification electrostatic precipitators of silicon production 25-50, alkaline binder 3-5 and molded material with a particle size of 6-50 mm and dried to a moisture content of 6-8%, in addition, petecox containing no fraction is fed to the molding more than 8 mm, in an amount of at least 70 mass. %, and for mixing serves a 10-15% aqueous solution of sodium alkali. However, 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 materials in the form of a finely dispersed fraction is not involved in the process and is carried away from the mixture with flue gases, which reduces the reactivity of the carbon reducing agent and reduces the quality of the resulting silicon metal from ore raw materials.

The known composition of the briquette mixture containing, mass. %: coke breeze 34-36; sawdust 1.5-2.5; liquid glass 6.5-7.4; petroleum bitumen 2.5-3.5; anthracite trifle - the rest (a.s. SU 1546469, C10L 5/10, publ. 02.28.1990).

The disadvantage of this known composition is the presence of petroleum bitumen, which requires heating before mixing to a temperature of 220-250 ° C and steaming the cooked briquette mass with hot steam at a temperature of 210 ° 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.%), Which increases the cost of briquettes.

Known coal briquette with high strength, as well as a method for its manufacture (patent RU 2224007, C10L 5/02, publ. 12.12.2001). A briquette with increased initial strength and consisting of 100 weight. including coal fines, 1-5 weight. including quicklime and 7-15 weight. including molasses. The briquette has a crushing resistance of not less than 70% and a dust generation rate of not more than 20% and is suitable for use in the smelting reduction process of producing iron. The coal fines in the briquette contain from 6 to 15 weight. % 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 at least 50% by weight. A method of manufacturing such briquettes includes operations: mixing 1-5 weight. including quicklime with 100 weight. including coal fines and aging the mixture; mixing 7-15 weight. including molasses with the aged mixture and mixing them and the direct formation of the mixed mixture in order to obtain briquettes. The method in which the coal fines contains from 6 to 15 weight. % moisture. The method in which 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 aging is carried out from 2 minutes to 2 hours to convert quicklime to slaked lime. A method in which stirring is carried out for 2-50 minutes to increase the curing rate. A method in which, after direct formation, the heating and drying operation is not carried out.

The disadvantage of this invention is that to achieve increased strength, the bonding ability of calcium sugar, which is 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, helps to harden the ingredients, which prevents the uniform distribution of quicklime throughout the mixture, this reduces mechanical strength and makes storage and transportation difficult.

The closest in technical solution and the achieved result is a method for producing carbon-containing briquettes (patent RU 2376342, C10L 5/12, publ. 20.12.2009). The briquetting method for semi-coke, mainly brown coal, includes the steps of preparing the starting components, mixing, pressing, drying and impregnating, involves grinding the starting components at the preparation stage to a particle size distribution of 0-7 mm and adding slaked lime with a water-lime ratio of 3 / 1-5 / 1 s CaO content from 5 to 15%, and after mixing the components, pressing and drying, the briquettes are impregnated with a liquid glass solution.

The disadvantage of the invention is the complexity of the technological process for the production of briquettes and a high content of ash and undesirable impurities.

The problem of the invention is the creation of effective carbon briquettes of reducing agents based on brown coal semi-coke, used for the production of crystalline silicon and improving the technical and economic performance of the smelting process.

In this case, 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 method of briquetting carbon reducing agents, mainly brown coal or stone semi-coke (coke), comprising mixing binder materials with semi-coke (coke), pressing and drying the briquettes according to the claimed invention, a combined binder is used as binding materials, containing high temperature and low temperature components, wherein the carbon reducing agent is first mixed with the high temperature component, then n zkotemperaturny component, wherein the high-temperature component as used bottoms of petroleum refining or catalytic pyrolysis tar gas oil in an amount of 25-30 wt. %, and as a low-temperature component use organic substances in the form of a solution of gluten or molasses, in the amount of 70-75 mass. %

The claimed invention is supplemented by the following clarifying features. The ratio of the mixture of the combined binder and semicoke (coke) is 1: 2.

Before mixing it with a binder, a carbon reducing agent can be ground to a particle size distribution of up to 3 mm.

Briquetting of carbon reducing agents is carried out under a pressure of 50-100 MPa.

The briquettes are dried at a temperature of 150-170 ° C for 40-60 minutes.

A distinctive feature of the present invention is: use as a binder for carbon reducing agents, a combined binder consisting of organic components in the form of solutions of gluten, starch or molasses responsible for mechanical strength and bottoms from oil refining in the form of pyrolysis resin or catalytic gas oil, providing briquettes strength at high temperatures, followed by briquetting on a roller or extruder press and drying.

Combined binder is a combination of low-temperature and high-temperature components, providing high strength briquettes in the entire temperature range of use of this reducing agent. First of all, a binder is added to the reducing agent (for example, brown coal semi-coke), which provides briquette strength at high temperature (high-temperature component). Particles of a carbon reducing agent, for example, based on brown coal, have a high specific surface and are first impregnated with high-temperature distillation residues from oil refining, then a low-temperature component is added to the carbon reducing agent - an organic binder that concentrates on the surface of the particles of the carbon reducing agent. During the drying of the obtained briquettes, the organic binder sets, forming a strong frame, which ensures the structural strength of the briquette during transportation and transfer of material through technological stages. When a briquette hits the top of an ore-thermal furnace, for example, during silicon production, at high temperatures, the organic binder starts to burn out, and the mechanical strength of the briquette begins to decrease. Simultaneously with this process, the high-temperature component of the binder inside the coal particles of the semicoke begins to heat up. At high temperatures, the bottoms from oil refining begin to coke, forming bridges between the particles, preventing the briquette from falling apart in the ore-thermal furnace, which ensures the completeness of the carbothermal reduction of silicon and prevents the transfer of small particles of the reducing agent to the furnace duct and its excessive consumption when producing technical silicon.

Organic substances are used as the low-temperature component and the total mass of the briquetted coal reducing agent is used, dry soluble substances, such as gluten (flour), 15-20 mass. % in an aqueous solution (50-60 wt.%), or liquid binders, such as molasses (molasses), 70-75 mass. % This is necessary to ensure sufficient mechanical strength of the briquette during the course of the melting process, which excludes re-grinding of the reducing agent during transportation to the electric furnace, which contributes to its combustion on the furnace top and removal with gases. As a high-temperature component, ensuring the strength of briquettes at high temperatures, forming a coke residue, bottoms products of oil processing (catalytic gas oil or pyrolysis resin) are used 25-30 mass. % The necessary heat resistance is manifested in the resistance to crushing and attrition of the reducing agent at high temperatures on the furnace top.

The method involves mixing a carbon reducing agent, for example, based on brown coal, which can be ground before mixing to a fractional composition of up to 3 mm, first with bottoms from oil refining (catalytic gas oil, oil pyrolysis resin), then the organic components of the binder (gluten, flour) are added , molasses, molasses), after which the mixture is again mixed for 5 minutes, briquetting is carried out under a pressure of 50-100 MPa on a roller or extruder press, drying is carried out at a temperature of 150-170 ° C for 40-60 minutes.

In the technology for the production of briquettes used as a carbon reducing agent for the production of industrial silicon and in other metallurgical processes, the properties of a carbon reducing agent play an important role:

Reactivity not less than 2.0 cm ³ / g × s Electrical resistivity not less than 1.37 × 10 ³ Ohm × cm Specific area 120-500 m ² / g Mechanical compressive strength not less than 5.0 MPa Thermal strength not less than 2.0 MPa

Examples of the proposed method.

Example 1. A carbon reducing agent (brown coal semi-coke with a fractional composition of up to 3 mm (67-72 wt.%) Was first mixed with catalytic gas oil (8-10 wt.%), Then water (15-20 wt.%) Was added and again mixed for at least 2 minutes, then added dry gluten (flour 5-8 wt.%) and mixed for 5 minutes.

With a decrease in gluten content of less than 5 mass. % decreases the mechanical strength of the briquette to a critical value. With an increase in gluten more than 8 mass. % strength does not increase significantly, while increasing the content of volatile components and the cost of acquiring this binder.

When the water content in the composition of the briquetted mixture is less than 15 mass. %, a mixture consisting of finely divided semi-coke is poorly briquetted, while the strength of the briquette is significantly reduced. When the water content in the coal charge is more than 20 mass. % during briquetting excess moisture is released and the time for drying the briquette increases.

With a decrease in the content of catalytic gas oil less than 8 mass. % decreases the thermal strength of the briquette to a critical value. With an increase in gas oil more than 10 mass. % thermal strength does not significantly increase, while increasing the content of volatile components and the cost of acquiring this binder. The experimental results are presented in table. one.

Example 2. Carbon reducing agent-semi-coke of brown coal was ground to a fractional composition of up to 3 mm (70-77 wt.%), Mixed with a pyrolysis resin (8-10 wt.%), Then molasses (15-20 wt.%) Was added, preheated to 70 ° C and stirred for 5 minutes.

With a decrease in molasses content of less than 15 mass. % decreases the mechanical strength of the briquette to a critical value. With an increase in molasses more than 20 mass. % strength does not increase significantly, while increasing the content of volatile components and the cost of acquiring this binder.

With a decrease in the content of pyrolysis resin less than 8 mass. % decreases the thermal strength of the briquette to a critical value. With an increase in pyrolysis resin more than 10 mass. % thermal strength does not significantly increase, while increasing the content of volatile components and the cost of acquiring this binder. The experimental results are presented in table. 2.

Example 3. Brown coal semi-coke with a fractional composition of up to 3 mm (65-72 wt.%)) Was mixed with a pyrolysis resin (8-10 wt.%), Then flour paste was added (20-25 wt.%) And mixed for 5 minutes. The concentration of dry flour in the paste was 18%).

With a decrease in the content of flour paste less than 20 mass. % decreases the mechanical strength of the briquette to a critical value. With an increase in flour paste more than 25 mass. % strength does not increase significantly, while increasing the content of volatile components and the cost of acquiring this binder. With a decrease in the content of pyrolysis resin less than 8 mass. % decreases the thermal strength of the briquette to a critical value. With an increase in pyrolysis resin more than 10 mass. % thermal strength does not significantly increase, while increasing the content of volatile components and the cost of acquiring this binder. The experimental results are presented in table. 3.

Example 4. Prepared according to examples 1-3 carbon reducing agents were briquetted under a pressure of 50-100 MPa. When the briquetting pressure is less than 50 MPa, the briquette strength decreases during the compression test, and at a pressure of more than 100 MPa, the briquette strength does not increase significantly. The briquettes were dried at a temperature of 150 ° C-170 ° C for 40-60 minutes.

When the drying temperature is less than 150 ° C, the duration of the drying process of the briquette increases. An increase in the drying temperature over 170 ° C leads to the ignition of the briquette.

If the time is less than 40 minutes, the drying process of the briquette at the given temperatures decreases the mechanical strength of the briquette. With an increase in the drying time of more than 60 minutes, the mechanical strength of the briquette does not increase significantly.

Claims (5)

1. The method of briquetting carbonaceous reducing agents, mainly brown coal or stone semi-coke (coke), comprising mixing binder materials with semi-coke (coke), pressing and drying the briquettes, characterized in that as the binder materials use a combined binder containing high temperature and low temperature components, and first, the carbon reducing agent is mixed with the high temperature component, then the low temperature component is added, while as a high temperature component of the component used are bottled products of oil refining in the form of a pyrolysis resin or catalytic gas oil in an amount of 25-30 mass. %, and as a low-temperature component using organic substances in the form of a solution of gluten or molasses in the amount of 70-75 mass. % 2. The method according to p. 1, characterized in that the ratio of the mixture of the combined binder and semi-coke (coke) is 1: 2. 3. The method according to p. 1, characterized in that the carbon reducing agent before being mixed with a binder is crushed to a particle size distribution of up to 3 mm 4. The method according to p. 1, characterized in that the briquetting is carried out under a pressure of 50-100 MPa. 5. The method according to p. 1 characterized in that the drying of the briquettes is carried out at a temperature of 150-170 ° C for 40-60 minutes