RU2807317C1 - Method for producing nano-sized silicon dioxide powder and plasma installation for its implementation - Google Patents

Abstract

FIELD: plasma technologies.

SUBSTANCE: invention relates to the plasma technologies providing plasma exposure to materials and can be used to produce silicon dioxide nanopowders. The method for producing nanosized silicon dioxide powder is to place a briquette containing from 70% quartz sand and up to 30% carbon on a pusher and feed it into the reactor; water is supplied into the water-cooled cover and water-cooled body, then a flow of compressed electric arc plasma is initiated using a plasma torch, which is directed to the briquette, under the influence of a high temperature of 2000-5000°C the components of the briquette enter into a chemical reaction with the formation of silicon monoxide and carbon monoxide; water steam is supplied through the fitting to the pipe located on the water-cooled lid. Getting into the nozzle and mixing with water vapour, silicon monoxide is oxidized to silicon dioxide and quickly cools, forming a mixture of particles with a size of 10-200 nm, which are then agglomerated into a mixture of particles with a size of 0.1-100 mcm, which then follow to the trap. As the briquette in the reactor evaporates, it is replaced with the next briquette moved by a pusher. A plasma installation is also claimed for implementing a method for producing nanosized silicon dioxide powder.

EFFECT: simplification of the process, increasing the specific surface area of silicon dioxide powder.

2 cl, 3 dwg

Description

The claimed technical solution relates to the field of plasma technologies, ensuring the introduction of materials into plasma. Can be used to produce silicon dioxide nanopowders used in 3D printing and high-performance liquid chromatography, in the construction industry as additives in concrete and dry mixtures to improve various characteristics (thermal conductivity, viscosity, etc.), in the chemical industry, in the production of rubbers , rubber products, polymers as an active filler and additive to improve their physical and chemical properties, such as wear resistance.

The invention is known according to patent No. CN212356560 (U) “Equipment for the production of amorphous nanospherical silicon dioxide.” The essence is an installation for producing amorphous nanospherical silicon dioxide, characterized in that it contains: a silicon tetrachloride supply device, a high-frequency plasma generator, a synthesis chamber, a cooling chamber, a first collection chamber, a first separator, a second collection chamber, a second separator, a third collection chamber, a vacuum unit and a chlorine regeneration device. The silicon tetrachloride feeding device is used to produce silicon tetrachloride gas; a high-frequency plasma generator is connected to the synthesis chamber to form a high-temperature plasma torch in the synthesis chamber, and a silicon tetrachloride supply device. oxygen in the synthesis chamber to produce silicon dioxide under the action of a high-temperature plasma torch; a cooling chamber is connected to a synthesis chamber to cool the produced silica, and a first collection chamber is connected to a cooling chamber to obtain a portion of the silica; the first separator is connected to a cooling chamber for receiving and separating part of the silica by pipelines, and the second collection tank is connected to the first separator for receiving silica separated from the first separator; a second separator is connected to the first separator for receiving and separating a portion of the silica, and a third collection chamber is connected to the second separator device for receiving the silica separated by the second separator; a chlorine gas collecting device is connected to the second separator to separate and collect chlorine gas generated in the pipeline, a vacuum unit is connected to the second separator, and a pipeline between the chlorine gas collecting devices is used to vacuum the equipment for preparing amorphous nanospherical silica.

The disadvantage of the known technical solution in relation to the claimed technical solution is:

- use of silicon tetrochloride as a raw material, which is synthetic and therefore not economically feasible;

- a by-product of the use of silicon tetrochloride is chlorine, which necessitates the use of additional measures to protect personnel and equipment;

- multi-stage design and multi-stage production of the final product.

A utility model is known under patent RU No. 169047 “Plasma installation for processing refractory silicate-containing materials.” The essence is a plasma installation for processing refractory silicate-containing materials, containing a melting furnace with a metal body, which is made hollow to form a water-cooling channel, a plasma torch installed through an insulator in the furnace lid, a drain chute for the melt exit, made in the side part of the melting furnace, a feeding device powdered raw materials, mounted on the side surface of the melting furnace body opposite the drain chute and made in the form of a screw feeder connected directly to the melting zone of the melting furnace, a loading hopper and an electric drive, a graphite anode mounted on the bottom of the melting furnace, characterized in that it additionally contains a protective a screen made in the form of a metal washer fixed perpendicularly to the plasmatron body under the lid of the melting furnace, while the diameter of the metal washer exceeds the diameter of the insulator in the furnace lid by at least 1.5 times; in addition, the protective screen is installed with the possibility of continuous air cooling, for the supply of which an additional channel is made in the plasmatron insulator; in addition, a drain chute for the melt outlet is located in the middle part of the melting furnace, and in the upper part of the melting furnace above the melting zone there is an additional pipe for removing nanoparticles.

The disadvantage of the known technical solution in relation to the claimed technical solution is:

- the impossibility of obtaining nanodispersed powders, since a melt is obtained,

- screw feed of raw materials with a lower temperature than the melt, which cools the melt and reduces evaporation and ionization of the melt,

- impossibility of quenching the output product due to the absence of a water vapor supply unit in the gas outlet pipe,

- insufficient specific surface area.

From the level of technology studied, the applicant did not identify the supply of raw materials in the form of briquettes made in a certain ratio of quartz and carbon.

From the researched level of technology, the applicant has not identified an analogue of the design of the claimed installation.

The technical result of the claimed technical solution is the development of a method for producing nano-sized silicon dioxide powder and a plasma installation for its implementation, allowing to achieve:

- use of natural raw materials (quartz sand);

- the possibility of obtaining nanodispersed powders rather than melt;

- single-stage process;

- supply of briquetted raw materials using a pusher with a higher temperature than the melt, which allows you to immediately transfer the raw materials to the state of ionized gas,

- the possibility of hardening the output product due to the presence of a water vapor supply unit in the gas outlet pipe,

- increased specific surface area compared to the known analogue RU No. 169047.

The essence of the claimed technical solution is a method for producing nano-sized silicon dioxide powder, which consists in installing a briquette containing from 70% quartz sand and up to 30% carbon on a pusher and feeding it into the reactor; Water is supplied into the water-cooled cover and water-cooled body, then a flow of compressed electric arc plasma is initiated using a plasma torch, which is directed to the briquette, while under the influence of a high temperature of 2000-5000 ° C, the components of the briquette enter into a chemical reaction with the formation of silicon monoxide and carbon monoxide into the nozzle , located on the water-cooled cover, water steam is supplied through the fitting; entering the nozzle and mixing with water vapor, silicon monoxide is oxidized to silicon dioxide and quickly cooled, forming a mixture of particles with a size of 10-200 nm, which are then agglomerated into a mixture of particles with a size of 0.1-100 microns, which then follow to the trap, while the design of the pusher allows you to keep the distance from the plasmatron to the briquette unchanged, which ensures a stable arc; As the briquette in the reactor evaporates, it is replaced with the next briquette moved by the pusher, while the replacement of one spent briquette with another is carried out in a continuous mode and does not allow the plasmatron arc to go out. Plasma installation for implementing a method for producing nano-sized silicon dioxide powder according to claim 1, containing a reactor, which is a metal box with a hollow body containing a water-cooled space between its walls, with a graphite lining 40 mm thick on the inside of the water-cooled body, and a water-cooled lid, insulated from the water-cooled reactor vessel to the insulator of the water-cooled reactor cover; in this case, a plasmatron is installed in the water-cooled reactor lid through a plasmatron insulator, which is a cathode, with the ability to initiate a flow of compressed electric arc plasma; in this case, in the water-cooled reactor lid there is a pipe with a fitting with the ability to remove gaseous reaction products and supply water vapor for their oxidation and hardening; in this case, in the nozzle there is a nozzle with the ability to supply water vapor towards the exiting hot gas; in the bottom of the reactor there is a hole with the ability to supply raw materials in the form of compressed briquettes from silicon-containing raw materials with an admixture of carbon, while graphite inserts are pressed into the briquettes from silicon-containing raw materials with an admixture of carbon, while graphite in the form of a graphite lining and graphite inserts in the briquettes is the anode, with in this case, the dimensions of the briquette made of silicon-containing raw materials with an admixture of carbon are made corresponding to the size of the hole in the bottom of the reactor; A pusher is installed under the reactor with the ability to supply briquettes from silicon-containing raw materials with an admixture of carbon into the reaction zone.

The claimed technical solution is illustrated in Fig. 1 - Fig. 3.

In FIG. 1 a general view of the claimed plasma installation is presented, where:

1 - plasmatron;

2 - water-cooled reactor cover;

3 - plasmatron insulator;

4 - water-cooled housing;

5 - graphite lining 40 mm;

6 - briquette made of silicon-containing raw materials with an admixture of carbon;

7 - pusher;

8 - insulator of the water-cooled reactor cover;

+ - cathode (plasma torch);

- anode (graphite lining plus graphite inserts into a briquette made of silicon-containing raw materials with an admixture of carbon).

In FIG. 2 The results of granulometric analysis of the powder are given:

2a - photo of the resulting powder from an electron microscope;

2b - granulometric composition of the resulting powder, obtained from a Mastersize laser particle size analyzer.

In FIG. 3 shows a table that presents the results of measuring the specific surface area of the resulting silicon dioxide powder in comparison with the analogue RU No. 169047.

Next, the applicant provides a description of the claimed technical solution.

The declared technical result is achieved by the development of a plasma installation for producing nano-sized silicon dioxide powders (hereinafter referred to as the claimed installation) and a method for its use.

The claimed installation relates to the field of plasma technologies and can be used to produce silicon dioxide nanopowders with increased specific surface area and improved rheological properties, as well as nanopowders of other volatile oxides used in various industries.

Next, the applicant shows the design of the claimed installation (Fig. 1).

The claimed installation contains a reactor (not indicated by a position in Fig. 1), which is a metal box with a hollow body 4 containing (body 4) a water-cooled space between its walls, with a graphite lining 5 40 mm thick on the inside of the water-cooled body 4, and a water-cooled cover 2, isolated from the metal reactor body 4 by an insulator 8 of the water-cooled reactor cover, for example, ceramic.

In this case, in the water-cooled lid of the reactor 2, through a plasmatron 3 insulator, for example, a ceramic one, a plasmatron 1 is installed, which is the cathode, with the ability to initiate a flow of compressed electric arc plasma.

In this case, a pipe with a fitting (not marked in Fig. 1) with the ability to remove gaseous reaction products and supply water steam for their oxidation and hardening is mounted in the water-cooled lid of the reactor 2. A nozzle is mounted in the nozzle (not indicated by a position in Fig. 1) with the ability to supply water vapor towards the exiting hot gas.

There is a hole in the bottom of the reactor (not indicated by a position in Fig. 1) with the possibility of supplying raw materials in the form of compressed briquettes of silicon-containing raw materials with an admixture of carbon (hereinafter referred to as briquettes) 6, into which graphite inserts are pressed (briquettes 6). In this case, graphite (graphite lining 5 and graphite inserts in briquettes 6) is the anode. In this case, the dimensions of the briquette 6 are made corresponding to the size of the hole in the bottom of the reactor. Under the reactor there is a pusher 7, for example a jack, with the ability to supply briquettes 6 into the reaction zone. The jack can be, for example, mechanical, hydraulic, automatic, etc.

The developed design of the water-cooled rector cover 2 protects the plasmatron 1 from high temperatures, thereby preventing its destruction, and also eliminates breakdown between the cathode and anode. As a result, the reliability and service life of the stated installation are increased.

Next, the applicant provides a description of the assembly of the claimed installation.

First, a water-cooled housing 4 is made, for example, from steel grade steel 3, for example, by welding.

Then the water-cooled reactor cover 2 is made, for example, from steel grade steel 3, for example, by welding.

Then the inner walls of the water-cooled housing 4 are lined with graphite to a thickness of 40 mm in order to protect the walls of the water-cooled housing 4 from high temperatures and for electrical insulation.

Then the water-cooled reactor cover 2 and the water-cooled body 4 are welded.

Then, an insulator of the water-cooled reactor cover 8 is installed between the water-cooled reactor cover 2 and the water-cooled body 4, for example, with a bolted connection, for the purpose of electrical insulation and sealing.

Then an insulator 3, for example ceramic, is installed in the water-cooled reactor cover 2 and secured, for example, with refractory cement. Insulator 3 is installed for the purpose of electrical insulation and sealing. Then the plasma torch 1 is installed in the insulator 3, for example, with a joint.

A pusher 7 is installed under the water-cooled housing 4, onto which a briquette 6 is installed.

Next, the applicant provides the claimed method of operation of the claimed installation.

A briquette 6 containing from 70% quartz sand and up to 30% carbon is installed on the pusher 7 and fed into the reactor. At the same time, the applicant explains that the ratio of 70% quartz sand and up to 30% carbon in the briquette was determined from a stereochemical calculation. The calculation was made based on the need to form silicon monoxide in the reactor, the formation temperature of which is lower than that of silicon dioxide. This allows you to increase the rate of evaporation of the briquette.

Water is supplied to the water-cooled cover 2 and the water-cooled housing 4.

Then, using a plasma torch 1, a flow of compressed electric arc plasma is initiated, which is directed to the briquette 6. At the same time, under the influence of a high temperature of 2000-5000 ° C, the components of the briquette 6 enter into a chemical reaction with the formation of silicon monoxide and carbon monoxide. At the same time, the applicant explains that at temperatures below 2000-5000 ° C, the evaporation of the briquette does not occur intensively enough.

Water steam is supplied to the nozzle located on the water-cooled cover 2 through a fitting. Entering the nozzle and mixing with water vapor, silicon monoxide is oxidized to silicon dioxide and quickly cooled, forming a mixture of particles with a size of 10-200 nm, which further agglomerate into a mixture of particles with a size of 0.1-100 microns, which then travel to a trap that is not element of the stated installation.

The design of the pusher, for example, a jack, allows you to keep the distance from the plasmatron 1 to the briquette 6 unchanged, which ensures a stable arc.

As the briquette 6 in the reactor evaporates, it is replaced with the next briquette moved by the pusher 7. The replacement of one spent briquette 6 with another is carried out in a continuous mode and does not allow the arc of the plasma torch 1 to go out.

Further, the applicant provided examples of implementation of the claimed technical solution.

Example 1. Preparation of nano-sized silicon dioxide powders at a temperature of 3000 °C.

We took the claimed device with walls lined with graphite 40 mm thick.

A briquette 6 containing, for example, 70% quartz sand and 30% carbon is installed on the pusher 7 and fed into the reactor.

Water is supplied to the water-cooled cover 2 and the water-cooled housing 4. Water vapor is supplied to the nozzle located on the water-cooled cover 2 through a fitting.

Then, a flow of compressed electric arc plasma is initiated through plasmatron 1. At the same time, under the influence of a high temperature of 3000 °C, the components of the briquette 6 enter into a chemical reaction with the formation of silicon monoxide and carbon monoxide. The temperature was determined by an indirect method based on the power of the plasmatron in accordance with the source [Kosmachev P.V. “Production of silicon dioxide nanomaterials by plasma-arc method from high-silica natural raw materials” p. 72, table. 3.3]:

Modes and thermophysical parameters of the plasmatron

No. Plasmatron power, kW Specific heat flow, MW/m² Arc temperature, K 1 24 0.5 1.0±5⋅10 ^- ⁴ 2800±30 2 37±0.6 1.5±6⋅10 ^- ⁴ 3400±32 3 56±0.8 2.5±8⋅10 ^- ⁴ 4600±40 4 59±0.7 3.0±5⋅10 ^- ⁴ 4900±45

The power of the plasmatron in Example 1 was 35 kW, which corresponds to a temperature of 3000 °C.

Getting into the nozzle and mixing with water vapor, silicon monoxide is oxidized to silicon dioxide and quickly cools, forming a mixture of particles with a size of 10-200 nm, which agglomerate into particles with a size of 0.1-100 microns and then travel to the trap.

The particle size was measured using an electron scanning microscope and a Mastersize laser particle size analyzer, the results are shown in Fig. 2.

In FIG. 2a (photo of the resulting powder from an electron microscope) it can be seen that a mixture of particles with a size of 10-200 nm is first formed, which then agglomerate into a mixture of particles with a size of 0.1-100 microns.

In FIG. Figure 2b shows the granulometric composition of the resulting powder, obtained from a Mastersize laser particle size analyzer, from which it can be seen that agglomeration is 0.1-100 microns.

The presented results prove the achievement of the stated technical result.

The design of the pusher, for example, a jack, allows you to keep the distance from the plasma torch 1 to the briquette 6 unchanged, which ensures a stable arc.

As briquette 6 in the reactor evaporates, it is replaced by the next one, moved by pusher 7. Replacing one spent briquette 6 with another is carried out in a continuous mode and does not allow the arc to go out.

The applicant measured the specific surface area of the resulting silicon dioxide powder in comparison with the analogue RU No. 169047. The measurement was carried out using the BET method for absorption of liquid nitrogen - a method of mathematical description of physical adsorption [https://ru.wikipedia.org/wiki/BET_Method].

The results are shown in the Table in Figure 3. It is shown that according to Example 1, an improved specific surface area was achieved - 85.3 m²/g compared to 41.0 m²/g for the analogue RU No. 169047. Moreover, the results for the analogue RU No. 169047 are taken from the source [Kosmachev P.V. “Preparation of silicon dioxide nanomaterials by the plasma-arc method from high-silica natural raw materials,” table. 4.2., page 98 and table. 4.3., p. 99] - author of the analogue patent RU No. 169047.

Example 2. Preparation of nano-sized silicon dioxide powders at a temperature of 2000 °C.

The sequence of actions was carried out according to Example 1, characterized in that the power of the plasmatron was 16 kW, which corresponds to a temperature of 2000 °C.

A briquette 6 containing, for example, 75% quartz sand and 25% carbon is installed on the pusher 7 and fed into the reactor.

The applicant measured the specific surface area of the resulting silicon dioxide powder in comparison with the analogue RU No. 169047. The measurement was carried out using the BET method for absorption of liquid nitrogen - a method of mathematical description of physical adsorption [https://ru.wikipedia.org/wiki/BET_Method].

The results are shown in the Table in Figure 3. It was shown that in Example 2 an improved specific surface area was achieved - 77.5 m²/g compared to 41.0 m²/g for the analogue RU No. 169047.

Example 3. Preparation of nano-sized silicon dioxide powders at a temperature of 5000 °C.

The sequence of actions was carried out according to Example 1, characterized in that the power of the plasmatron was 60 kW, which corresponds to a temperature of 5000 °C.

A briquette 6 containing, for example, 95% quartz sand and 5% carbon is installed on the pusher 7 and fed into the reactor.

The applicant measured the specific surface area of the resulting silicon dioxide powder in comparison with the analogue RU No. 169047. The measurement was carried out using the BET method for absorption of liquid nitrogen - a method of mathematical description of physical adsorption [https://ru.wikipedia.org/wiki/BET_Method].

The results are shown in the Table in Figure 3. It was shown that according to Example 3, an improved specific surface area was achieved - 80 m²/g compared to 41.0 m²/g for the analogue RU No. 169047.

Thus, from the above we can conclude that the applicant has achieved the stated technical result, namely: a method for producing nano-sized silicon dioxide powder and a plasma installation for its implementation have been developed, which made it possible to achieve, in comparison with the prototype:

- the possibility of obtaining nanodispersed powders rather than a melt,

- briquette mechanical supply of raw materials with a higher temperature than the melt, which makes it possible to obtain gaseous silicon dioxide in large volumes.

- the possibility of hardening the output product due to the presence of water vapor supply units in the gas outlet pipe,

- increased specific surface area (see Table in Fig. 3).

The claimed technical solution complies with the “novelty” patentability condition imposed on inventions, since as of the date of submission of the application materials by the applicant, no sources were identified from the researched level of technology that have a set of features identical to the set of features of the claimed technical solution.

The claimed technical solution complies with the patentability condition “inventive step” applied to inventions, because the totality of the declared features ensures obtaining technical results that are not obvious to a specialist and exceed the technical result of the prototype.

The claimed technical solution meets the patentability condition of “industrial applicability” applied to inventions, because the claimed technical solution can be implemented using standard equipment and known techniques.

Claims (11)

1. A method for producing nano-sized silicon dioxide powder, which consists in the following: a briquette containing from 70% quartz sand and up to 30% carbon is placed on the pusher and fed into the reactor; water is supplied to the water-cooled cover and the water-cooled body, then, using a plasma torch, a stream of compressed electric arc plasma is initiated, which is directed to the briquette, while under the influence of a high temperature of 2000-5000 ° C, the components of the briquette enter into a chemical reaction with the formation of silicon monoxide and carbon monoxide, water vapor is supplied to the pipe located on the water-cooled cover through a fitting; entering the nozzle and mixing with water vapor, silicon monoxide is oxidized to silicon dioxide and quickly cooled, forming a mixture of particles with a size of 10-200 nm, which are then agglomerated into a mixture of particles with a size of 0.1-100 microns, which then follow to the trap, while the design of the pusher allows you to keep the distance from the plasmatron to the briquette unchanged, which ensures a stable arc; As the briquette in the reactor evaporates, it is replaced with the next briquette moved by a pusher, while the replacement of one spent briquette with another is carried out in a continuous mode and does not allow the plasmatron arc to go out. 2. Plasma installation for implementing a method for producing nano-sized silicon dioxide powder according to claim 1, containing a reactor, which is a metal box with a hollow body containing a water-cooled space between its walls, with a graphite lining 40 mm thick on the inside of the water-cooled body, and a water-cooled cover, isolated from the water-cooled reactor body by a water-cooled reactor cover insulator; in this case, a plasmatron is installed in the water-cooled reactor lid through a plasmatron insulator, which is a cathode, with the ability to initiate a flow of compressed electric arc plasma; in this case, in the water-cooled reactor lid there is a pipe with a fitting with the ability to remove gaseous reaction products and supply water vapor for their oxidation and hardening; in this case, in the nozzle there is a nozzle with the ability to supply water vapor towards the exiting hot gas; in the bottom of the reactor there is a hole with the ability to supply raw materials in the form of compressed briquettes from silicon-containing raw materials with an admixture of carbon, while graphite inserts are pressed into the briquettes from silicon-containing raw materials with an admixture of carbon, while graphite in the form of a graphite lining and graphite inserts in the briquettes is the anode, with in this case, the dimensions of the briquette made of silicon-containing raw materials with an admixture of carbon are made corresponding to the size of the hole in the bottom of the reactor; A pusher is installed under the reactor with the ability to supply briquettes from silicon-containing raw materials with an admixture of carbon into the reaction zone.