RU2799206C1 - Method for production of amorphous silicon dioxide in granule form - Google Patents

Abstract

FIELD: silicon production.

SUBSTANCE: invention relates to the production of amorphous silicon dioxide in the form of granules to obtain a product with improved properties. A method for obtaining amorphous silicon dioxide in the form of granules is proposed, which consists in preparing and purifying a sodium silicate solution with subsequent dissolution of settled flakes of undissolved sodium silicate at the first stage, at the second stage, the formation of the substrate (a), during which 18–20 m³ suspension of sodium silicate with a density of 1.130-1.200 g/cm³ and a temperature of 20-95°C and 5-6 m³ of sodium sulphate solution with a density of 1.03-1.06 g/cm³, the neutralization process (b), which consists in supplying dilute sulfuric acid to the substrate in the reactor at a feed rate of 14 to 20 m³/ h for 16-25 min, the temperature in the reactor at this stage is maintained at 80-88°C, then from 16-25 minutes to 47-87 minutes, sulfuric acid is fed into the reactor, the feed rate is 6-15 m³/h, and from 45-80 minutes to 79-110 minutes, a suspension of sodium silicate is fed into the reactor at a feed rate of 2 0-2.8 m³/h, at the same time, sulfuric acid is supplied simultaneously with sodium silicate, the feed rate is 2.0-2.8 m³/h, after 79-110 minutes the supply of sodium silicate stops, from 79- 110 to 96-130 minutes, the sulfuric acid supply rate is 2.2-3.0 m³/h, the suspension is averaged using the paddle mixer (c), at the third stage, the suspension is filtered, the sediment is washed and repulped, and at the fourth stage, suspension of silicon dioxide is dried and granulated, whereas the suspension is fed from the collection tank into the pressure tank of the dryer, from where it flows by gravity to the disk of the spraying mechanism, where due to its rotation at a speed of n = 4000-8000 rpm in the presence of a drying agent, the suspension is sprayed, whereas drying the suspension in the dryer occurs in the temperature zone 500-650°C by a short-term, within 5-8 seconds, stay of granules in it, then the amorphous silicon dioxide obtained in the form of microgranules settles in the cone of the dryer and is fed into the pneumatic transport system, from where it is fed to the cyclones by a fan, and the amorphous silicon dioxide that has settled inside the cyclones in the form of microgranules is supplied for packaging.

EFFECT: preservation of the original structure of the particles and the homogeneity of amorphous silicon dioxide, as well as the high purity of the resulting product.

1 cl, 4 dwg, 1 ex

Description

The invention relates to the field of technological processes in the chemical industry and can be used to obtain amorphous silicon dioxide, in particular, the invention relates to a new method for producing amorphous silicon dioxide in the form of granules to obtain a product with improved properties.

It is common practice to use precipitated silicas as a catalyst support, as an absorbent for active materials (particularly fluid carriers), as a viscosity enhancer, builder or anti-caking agent, as a separator element for batteries, and as an additive. for toothpaste or paper.

Precipitated silicas can also be used as reinforcing fillers in silicone matrices (e.g. for coating electrical cables) or in compositions based on natural or synthetic polymers, in particular elastomers, which are mainly based on dienes, e.g. for shoe soles, floor coverings, gas barriers, non-combustible materials, as well as technical parts such as funicular rollers, insulation for household appliances, insulation for pipelines for liquids or gases, seals for brake systems, sheaths, cables and drive belts.

Thus, it is common practice to obtain, by certain methods using a precipitation reaction between silicate and dilute acid, precipitated silicas which have sufficient dispersibility (degree of fineness) in polymer (elastomer) compositions and good reinforcing properties, making it possible to impart to said compositions , in which they are included, a very good ratio of properties.

At the moment, there are many developments in this area, however, the great demand and valuable properties of this product cause interest in the development of new technologies and methods for its production, as well as further improvement of its properties.

From patent document RU 93053018 A, published on March 27, 1996, a method is known for producing highly dispersed silicon dioxide, wherein an aqueous solution of sodium silicate is carbonized, silicon dioxide is separated from the soda solution by filtration, the wet silica precipitate is treated with acid, followed by washing with water containing a surfactant substance, while a solution of hydrochloric acid is used to treat (neutralize) the wet precipitate of silicon dioxide. To wash the precipitate, water is used, preferably containing 0.001% of a surfactant that is a wetting agent and detergent, for example, OP-10, sintanol, etc.

Patent document RU 2171781 C, published on 10.08.2001, discloses an amorphous silicon dioxide having a radioactive dentine abrasion index of 30-70, an oil absorption capacity of 100-155 cm ³ /100 g, a BET surface area of 50-200 m ² /g. Also disclosed is a method for its preparation, including: a) the step of adding a solution of sodium silicate with a concentration of 17.0-21.5% by weight to water at a molar ratio of SiO ₂ : Na ₂ O from 2.1 to 2.5; b) the step of adding to the resulting solution a 15-20% aqueous solution of sulfuric acid and a solution of sodium silicate with the same concentration and ratio of SiO ₂ : Na ₂ O for a period of more than 40 min and a pH of 8 to 9.0; c) the stage of aging the resulting mass up to 30 min at 90-100°C; d) the stage of the second addition of 15-20% aqueous solution of sulfuric acid to reduce the pH to 3-5; e) the stage of aging the mass up to 20 min at 90-100°C, adjusting the pH to 3.5-5.0, filtering, washing and drying the final liquid pasty mass. The essence of the invention also lies in the composition for the oral cavity, including the above-described amorphous silicon dioxide. The present invention makes it possible to achieve good cleaning properties of amorphous precipitated silicas with low abrasive characteristics.

As the closest analogue to the proposed invention, a method for producing highly dispersed amorphous silicon dioxide, disclosed in patent application RU 2018114269 A, published on 10/18/2019, can be adopted. The known method includes preparing water to a dry residue content of 0.1 to 0.05 g/l, sodium silicate solution to a density of 1.1-1.25 g/l and a silica content of 12-17%, preparation of a sulfuric acid solution to a density of 1.04-1.35 g/cm ³ , precipitation of silicon dioxide from a solution of sodium silicate with a solution of sulfuric acid under the control of the pH of the medium to a pH value of 5-6 units, grinding the resulting solution in a colloid mill to achieve a granulometric composition with a weighted average particle diameter d90 10-15 µm, isolation of silicon dioxide by filtration on a filter press to a dry residue content of 20%, washing of silicon dioxide by dissolving salts, grinding the resulting solution in a colloid mill to achieve a granulometric composition with a weighted average particle diameter d90 10-15 µm, isolation silicon dioxide by filtering on a filter press to a dry residue content of 20%, grinding silica sol on a roller crusher to a fraction of 0.1-2.0 mm, drying silica sol in a drying drum, micronization and classification of the finished product to obtain the specified quality characteristics in terms of granulometric composition.

The main disadvantage of this closest analogue is the formation of granules of amorphous silicon dioxide using shear deformations, which inevitably entail, to one degree or another, the destruction of the structure of the particles obtained during the deposition of amorphous silicon dioxide, which in turn can reduce its reinforcing properties in elastomers. and other properties.

The main purpose of the present invention is to overcome the shortcomings of the prior art and to propose a new method for obtaining precipitated amorphous silica in the form of granules with improved properties, which can be used as a reinforcing filler in polymer (elastomer) compositions and other applications, and the method is an alternative to these known methods for producing amorphous silicon dioxide.

In FIG. 1 shows the production scheme for cleaning liquid glass (sodium silicate solution) (1st stage of the method).

In FIG. 2 shows the production scheme for the production of precipitated silica (stage 2 of the process).

In FIG. 3 shows the production scheme for filtering a suspension of neutralized silica, washing and repulpation of the precipitate (stage 3 of the method).

In FIG. 4 shows a production scheme for drying a silica slurry (stage 4 of the process).

The proposed method is aimed at providing adhesive interactions of particles of amorphous silicon dioxide to the extent sufficient to maintain the form of granules obtained during the drying process. At the same time, the obtained degree of adhesive interaction ensures good dispersion of amorphous silicon dioxide during its use as a reinforcing filler in elastomers.

The technical result from the implementation of the proposed method is the formation of granules of amorphous silicon dioxide without the use of shear deformations, which inevitably entail, to one degree or another, the destruction of the structure of the particles obtained in the process of deposition of amorphous silicon dioxide.

Also, the result of the invention is to ensure the purity, preservation of the original structure of the particles, the uniformity of amorphous silicon dioxide.

An additional effect is to increase the reinforcing properties of the resulting silica in elastomers and other polymers.

This goal is achieved mainly through the use of four stages of purification of a solution of sodium silicate (liquid glass), as well as obtaining granules of amorphous silicon dioxide without applying deforming forces to the material while maintaining its original structure.

First, a purified sodium silicate slurry is obtained. The precipitated silica slurry is obtained by neutralizing the purified sodium silicate slurry with sulfuric acid (H ₂ SO ₄ ) at a temperature of 20-95°C. In the reactor, the sodium silicate solution reacts with sulfuric acid to form sodium sulfate and hydrated silicon dioxide.

The reaction proceeds according to the equation:

nNa ₂ O × mSiO ₂ + nH ₂ SO ₄ = nNa ₂ SO ₄ + mSiO ₂ × nH ₂ O

The end of the neutralization process is controlled by the pH of the suspension.

The neutralized suspension is filtered, the precipitate is washed from sodium sulfate Na ₂ SO ₄ with water. The washed precipitate of silica is diluted with water and dried in spray dryers.

Briefly, the proposed method can be characterized as follows:

The method for producing amorphous silicon dioxide in the form of granules includes essentially 4 stages:

Stage 1 - preparation of a solution of sodium silicate.

The essence of the first stage is that after dissolution in autoclaves, the resulting colloidal solution of sodium silicate (hereinafter referred to as liquid glass) enters the automatic dilution unit to a density of 1.130-1.200 g / cm ³ (density is measured at a solution temperature of 20 ° C).

Then the diluted liquid glass enters the sludge trap, where the first stage of purification of liquid glass from suspended particles takes place. Further, the diluted liquid glass by gravity, through a sieve (the second stage of cleaning the liquid stele), is sent to settling tanks, which also serve as capacitive equipment, where the third stage of cleaning liquid glass from suspended particles takes place.

From the settling tanks, liquid glass is pumped into the tanks of intermittent heaters equipped with steam jackets. In heaters, liquid glass is heated to a temperature of 80÷95°C, where coagulation occurs within 20-60 minutes (the fourth stage of liquid glass purification). The purified liquid glass is pumped into storage tanks, and the flakes of undissolved sodium silicate that have settled to the bottom of the heater tank as a result of coagulation are pumped into autoclaves for further dissolution.

The technical task of the first stage is to clean the sodium silicate solution from undissolved sodium silicate.

The uniqueness of this method of cleaning liquid glass lies in the absence of analogues, in simplicity, since it does not require additional equipment (filters) and cleaning speed.

A detailed process flow diagram of stage 1 is shown in Fig. 1.

Stage 2 - obtaining precipitated silicon dioxide.

The essence of the second stage is that the sodium silicate solution is neutralized with sulfuric acid (H ₂ SO ₄ ) at a temperature of 20-95°C. In the reactor, the sodium silicate solution reacts with sulfuric acid to form sodium sulfate and hydrated silicon dioxide.

The reaction proceeds according to the equation:

nNa ₂ O × mSiO ₂ + nH ₂ SO ₄ = nNa ₂ SO ₄ + mSiO ₂ × nH ₂ O

The end of the neutralization process is controlled by the pH of the suspension.

Process description:

1. Substrate preparation in the reactor:

- 18-20 m ³ of purified water glass with a density of 1.130-1.200 g/cm ³ and a temperature of 20-95°C is supplied from the accumulator tank by a pump to a batch reactor equipped with a steam jacket for heating.

- 5-6 m ³ of a sodium sulfate solution with a density of 1.03-1.06 g/cm ³ is pumped from the storage tank for the sodium sulfate solution into the reactor by a pump, then water is supplied to the resulting solution and brought to a density of 1.08-1, 12 g/ ^cm3 .

2. Technological process of neutralization:

- diluted to 6-11% sulfuric acid (hereinafter sulfuric acid) is supplied to the heated substrate using a pump from the storage tank at a feed rate of 14 to 20 m ³ /h for 16-25 minutes. The temperature in the reactor at this stage is maintained at 80-88°C;

- from 16-25 minutes to 47-87 minutes, sulfuric acid is fed into the reactor, the feed rate is 6-15 m ³ /h. By 47-87 minutes the pH of the solution is 7.2-6.5. Temperature up to 25-50 minutes is maintained at 80-88°C. From 25-50 minutes to 95-130 minutes (the end of the neutralization process), the temperature of the solution rises to 89-93°C ;

- from 45-80 minutes to 79-110 minutes liquid glass is fed into the reactor at a feed rate of 2.0-2.8 m ³ /h. At the same time, simultaneously with liquid glass, sulfuric acid is supplied, the feed rate is 2.0-2.8 m ³ /h, the pH of the solution at this stage is maintained constantly at 7.5-7.

- from 79-110 minutes, the supply of liquid glass stops. From 79-110 to 96-130 minutes the rate of supply of sulfuric acid is 2.2-3.0 m ³ /h, by 96-130 minutes the pH of the solution drops to 5-3.

From the reactor, the neutralized slurry is pumped into the neutralized slurry collection vessel, where the slurry is averaged due to the operation of the paddle mixer.

The technical task of the second stage is to obtain precipitated silicon dioxide.

The uniqueness of this method for obtaining precipitated silicon dioxide lies in the absence of a similar process, as well as temperature and time conditions.

A detailed process flow diagram of stage 2 is shown in Fig. 2.

Stage 3 - filtration of the suspension, washing and repulpation of the sediment.

The essence of the third stage is that the neutralized suspension is pumped from the collection tank to the filter press. The precipitate of silicon dioxide is filtered from the mother liquor at an excess pressure of not more than 0.4 MPa and washed with water at a temperature of 45-60°C at an excess pressure of not more than 0.6 MPa. The sediment washing time is determined by the minimum content of soluble salts in the washing water using a conductometer. The washed precipitate of silicon dioxide from filter presses is discharged through chutes into repulp mixers, where it is diluted with water to a density of at least 1.05 g/cm ³ . To ensure uniform mixing, a paddle mixer and a circulation system using a pump are used. After the sediment is diluted, a solution of sodium aluminate is fed into the repulpator. From the mixer-repulpators, the suspension is pumped to vibrating screens. The suspension that has passed through the vibrating screen is collected in a collection container.

The technical task of the third stage is to wash and purify the precipitated silica.

A detailed process flow diagram of stage 3 is shown in Fig. 3.

Stage 4 - drying the suspension of silicon dioxide and its granulation.

The essence of the fourth stage is as follows. From the collection tank, the suspension is pumped into the pressure tank of the dryer by a pump. From the pressure tank of the dryer, the suspension flows by gravity to the disk of the spraying mechanism, where due to its rotation (n=4000-8000 rpm), the suspension is sprayed. The drying agent is formed in the furnace during the combustion of natural gas and is fed into the drying chamber at a temperature of up to 750°C.

Drying the suspension in a dryer in a relatively high temperature zone of 500-650 ° C, but with a short stay of granules in it within 5-8 seconds, allows to a large extent to preserve the original physico-chemical properties and structure of the particles laid down by the technological process, without applying deforming forces to the material. The amorphous silicon dioxide obtained in the form of microgranules settles in the cone of the dryer and is supplied by a sluice gate to the pneumatic transport system, from where it is supplied to the cyclones by a fan. Amorphous silicon dioxide settled inside the cyclones in the form of microgranules through a sluice gate enters the bunker and further for packing.

The soot-air mixture that has not settled in the cyclones is fed by a fan through the dryer gas duct to the suspension spray zone for further growth of powdered dry amorphous silicon dioxide on sprayed wet amorphous silicon dioxide in the dryer during its drying.

Dried particles of silicon dioxide that have not settled in the dryer cone with a mass fraction of moisture up to 8% in the form of a fine powder due to the rarefaction created by the smoke exhauster from the spray dryer, along with the drying agent, enter through the gas duct:

- to the input of bag filters. The soot-air mixture has a temperature not exceeding 140°C. As a result of a decrease in the flow rate and a change in the direction of movement, part of the silicon dioxide settles in the lower part of the bag filter hopper, and the rest enters the bags, where it settles on the inner walls of the bag filters. After shaking with the help of a shaking mechanism, silicon dioxide from the inner surface of the bags enters the intersectional hopper of bag filters, then through the auger and sluice gate enters the pneumatic transport, from where it is fed into the cyclones by the fan, where it is deposited and then enters the hopper and further for packing;

- at the entrance to the centrifugal chamber for cleaning gas and dust mixtures (hereinafter CCP). The soot-air mixture has a temperature of 100-300°C. Silicon dioxide settled inside the CCU enters the dust collector bunker and then enters the pneumatic transport through the sluice gate, from where it is fed into the cyclones by a fan, where it is deposited and then enters the bunker and further for packing.

Silicon dioxide that has not settled in the cyclones is fed by a fan into the gas duct of the dryer, for further growth of powdered dry amorphous silicon dioxide on sprayed wet amorphous silicon dioxide in the dryer during its drying.

The technical task is to obtain amorphous silicon dioxide in the form of granules.

The uniqueness of this method for obtaining amorphous silicon dioxide in the form of granules lies in the absence of a similar process of growing powdered dry amorphous silicon dioxide on sprayed wet amorphous silicon dioxide in a dryer during its drying.

A detailed process flow diagram of stage 4 is shown in Fig. 4.

As a result of the implementation of the method, the formation of granules of amorphous silicon dioxide occurs without the use of shear deformations, which entail, to one degree or another, the destruction of the structure of the particles obtained in the process of deposition of amorphous silicon dioxide, which leads to the preservation of the original structure of the particles, the homogeneity of amorphous silicon dioxide.

Due to the use of four stages of purification of the sodium silicate solution and stage 3, the purity of the resulting product and its high quality are ensured.

Distinctive features of the proposed method from the known methods of granulation of silicon dioxide are the following:

- granules formed by spraying a suspension of amorphous silicon dioxide with simultaneous supply of dry powdered amorphous silicon dioxide to the surface of the formed wet granules;

- in the process of formation and drying of the granules, the excess of powdered amorphous silicon dioxide is removed;

- weight ratio of the sprayed dispersion of amorphous silicon dioxide to dry powdered amorphous silicon dioxide, as well as the particle size of the dispersion, which is determined by the rate of removal of vapors of the dispersion medium;

- the formation of granules is combined in time and space with the removal of the dispersion medium;

- obtaining granules occurs without the application of deforming forces to the material;

- the formation and growth of granules takes place in a relatively high temperature zone of 500-650 ° C, but with a short-term, within 5-8 seconds, stay of granules in it, which makes it possible to largely preserve the original physico-chemical properties laid down by the technological process, and structure of particles of amorphous silicon dioxide.

All equipment used in the method, their design, processes and operations, as well as substances and materials, are widely known in the art and in the prior art and do not require special disclosure.

Implementation of the invention

We have carried out experimental studies on the implementation of the proposed method on the existing production line. Studies have shown the possibility of carrying out the invention and achieving a technical result.

Example

This example is intended to illustrate the proposed method and does not limit it. Commercially available sodium silicate was dissolved in an autoclave. After dissolution in an autoclave, the resulting liquid glass is fed to the automatic dilution unit and diluted to a density of about 1.170 g/cm ³ (density measurement is carried out at a temperature of about 20°C). Then the liquid glass sequentially passes through the sludge trap, by gravity through a sieve, settling tanks, and then pumped into batch heaters equipped with steam jackets by a pump. In heaters, liquid glass was heated to a temperature of 95°C, where it was subjected to coagulation for about 40 minutes. Further, the purified liquid glass is pumped into storage tanks.

Then, 19 m ³ of purified water glass with a density of about 1.170 g/cm ³ and a temperature of about 95°C is pumped from the accumulator tank into a batch reactor equipped with a steam jacket for heating, and from the accumulator tank for sodium sulfate solution, 5 m ³ sodium sulfate solution and water is supplied to the resulting solution to obtain a solution density of approximately 1.1 g/cm ³ . Thus, a substrate is formed.

Dilute sulfuric acid and liquid glass are supplied to the heated substrate according to the technology described above in the "disclosure of the invention" section to carry out neutralization. The end of the neutralization process is controlled by the pH of the suspension (3-5). From the reactor, the neutralized slurry is pumped into the neutralized slurry collection vessel, where the slurry is averaged due to the operation of the paddle mixer.

Further, the neutralized suspension is pumped from the collection tank to the filter press. The precipitate of silicon dioxide is filtered off from the mother liquor at an overpressure of about 0.3 MPa and washed with heated water at an overpressure of about 0.3 MPa. The sediment washing time is controlled by a conductometer. The washed precipitate of silicon dioxide from the filter presses is discharged into repulp mixers, where it is diluted with water to a density of at least 1.05 g/cm ³ . To ensure uniform mixing, a paddle mixer and a circulation system using a pump are used. After the sediment is diluted, a solution of sodium aluminate is fed into the repulpator. From the mixer-repulpators, the suspension is pumped to vibrating screens. The suspension that has passed through the vibrating screen is collected in a collection container.

From the collection tank, the suspension is pumped into the pressure tank of the dryer by a pump. From the pressure tank of the dryer, the suspension flows by gravity to the disc of the spraying mechanism, where, due to its rotation (n=4000 rpm), the suspension is sprayed. The drying agent has a temperature of about 550°C. The residence time of the pellets in the dryer was about 7 seconds.

The amorphous silicon dioxide obtained in the form of microgranules settles in the cone of the dryer and is supplied by a sluice gate to the pneumatic transport system, from where it is supplied to the cyclones by a fan. Amorphous silicon dioxide settled inside the cyclones in the form of microgranules through a sluice gate enters the bunker and further for packing.

The soot-air mixture that has not settled in the cyclones is fed by a fan through the dryer gas duct to the suspension spray zone for further growth of powdered dry amorphous silicon dioxide on sprayed wet amorphous silicon dioxide in the dryer during its drying.

Silicon dioxide that has not settled in the cyclones is fed by a fan into the gas duct of the dryer, for further growth of powdered dry amorphous silicon dioxide on sprayed wet amorphous silicon dioxide in the dryer during its drying.

As can be seen, as a result of the implementation of the method, the formation of granules of amorphous silicon dioxide occurs without the use of shear deformations, the stages of grinding or crushing, which entail, to one degree or another, the destruction of the structure of the particles obtained in the process of deposition of amorphous silicon dioxide, which leads to the preservation of the original structure particles and homogeneity of amorphous silicon dioxide.

Due to the use of four stages of purification of the sodium silicate solution and the stage of washing and filtration, a high purity and high quality of the resulting product is ensured.

All of these improvements, in turn, will obviously increase the reinforcing properties of the resulting silica in elastomers, as well as the properties of silica in other applications.

Claims (15)

A method for producing amorphous silicon dioxide in the form of granules, characterized in that it includes the following steps: (1) the stage of preparation and purification of the sodium silicate solution, at which the colloidal solution of sodium silicate dissolved in the autoclave enters the automatic dilution unit to a predetermined density, and then sequentially enters the sludge trap, then by gravity, through a sieve, is sent to the settling tanks and then pumped into intermittent heaters equipped with steam jackets, where coagulation takes place, then the purified sodium silicate solution is pumped into storage tanks, and the undissolved sodium silicate flakes settled on the bottom of the heater after coagulation are pumped into the autoclave for further dissolution; (2) the stage of obtaining precipitated silicon dioxide, which carry out the following operations: a) preparation of a substrate on which: - 18–20 m ³ of a suspension of sodium silicate with a density of 1.130–1.200 g/cm ³ and a temperature of 20–95°C are supplied from the storage tank by a pump to a batch reactor equipped with a steam jacket for heating; - 5-6 m ³ of a sodium sulfate solution with a density of 1.03-1.06 g / cm ³ is pumped from the storage tank for the sodium sulfate solution into the reactor by a pump, then water is supplied to the resulting solution and brought to a density of 1.08-1, 12 g/cm ³ ; b) the implementation of the neutralization process, in which: - diluted sulfuric acid is supplied to the heated substrate by means of a pump from the storage tank at a feed rate of 14 to 20 m ³ /h for 16-25 min, the temperature in the reactor at this stage is maintained at 80-88°C; - from 16-25 minutes to 47-87 minutes, sulfuric acid is supplied to the reactor, the feed rate is 6-15 m ³ / h, by 47-87 minutes the pH of the solution is 7.2-6.5, the temperature is maintained up to 25-50 minutes 80-88°C, from 25-50 minutes to 95-130 minutes, i.e. before the end of the neutralization process, the temperature of the solution rises to 89-93°C; - from 45-80 minutes to 79-110 minutes, a suspension of sodium silicate is fed into the reactor at a feed rate of 2.0-2.8 m ³ / h, at the same time sulfuric acid is fed simultaneously with sodium silicate, a feed rate of 2.0- 2.8 m ³ /h, the pH of the solution at this stage is maintained constantly at 7.5-7; - from 79-110 minutes the supply of sodium silicate stops, from 79-110 to 96-130 minutes the supply rate of sulfuric acid is 2.2-3.0 m ³ /h, by 96-130 minutes the pH of the solution drops to 5-3; c) further from the reactor, the neutralized suspension is pumped into the neutralized suspension collection tank, where the suspension is averaged due to the operation of the paddle mixer; (3) the stage of suspension filtration, washing and repulpation of the sediment, at which the neutralized suspension is fed from the collection tank to the filter press, the silica precipitate is filtered from the mother liquor and washed, the washed silica precipitate from the filter presses is discharged into repulp mixers, where it is diluted with water, after which a solution of sodium aluminate is fed into the repulpator, and from the mixer-repulpators the suspension is fed to vibrating screens and collected in a collection container; (4) the stage of drying the suspension of silicon dioxide and its granulation, at which the suspension is fed from the collection tank to the pressure tank of the dryer, from where it flows by gravity to the disk of the spraying mechanism, where due to its rotation at a speed of n=4000-8000 rpm in the presence of drying agent, the suspension is sprayed, while the suspension is dried in the dryer in a temperature zone of 500-650 ° C with a short stay of granules in it, within 5-8 seconds, then the amorphous silicon dioxide obtained in the form of microgranules settles in the cone of the dryer and is fed into the pneumatic transport system, from where it is fed into the cyclones by a fan, and the amorphous silicon dioxide that has settled inside the cyclones in the form of microgranules enters the packaging, at the same time, the soot-air mixture and silicon dioxide that have not settled in the cyclones are fed into the suspension spray zone for further growth of powdered dry amorphous silicon dioxide on the sprayed wet amorphous silicon dioxide in the dryer during its drying.

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