RU2713259C1 - Method of producing finely dispersed amorphous silica - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing finely dispersed amorphous silica. Method of producing fine-grained amorphous silica involves milling and drying opal-cristobalite rock. Preliminary crushing of opal-cristobalite rock to size of not more than 5 cm is made. Drying-crushing unit is made: after start-up, air-gas mixture is heated continuously in heat generator to 150–600 °C. After that prepared opal-cristobalite rock is supplied to inlet belt of drying-crushing unit through metering device, which is interconnected with rotor and burner of unit. Then rock is supplied to rotor section, where it is crushed at constant supply of heated air-gas mixture, as a result of which powder with particle size from 0.01 to 350 mcm and moisture content from 1 % to 5 % is obtained. Further, the obtained powder is fed into an air duct in which, as a result of heat exchange with the ambient air, the powder is cooled. Method then includes feeding into bag filter, passing through which fine powder with high content of amorphous silicon is deposited in screw section, and cleaned in filter air is taken to environment.

EFFECT: technical result is the creation of a method of producing fine-grained amorphous silica, which enables to manufacture a product with high content of amorphous silicon and characteristics.

1 cl, 1 tbl, 2 dwg

Description

Technical field

The invention relates to inorganic chemistry, in particular to an inorganic product used as active ingredients for building and filtering materials, as well as biologically active additives.

State of the art

Closest to the claimed composition is the RF patent for the invention No. 2387608 "METHOD FOR PRODUCING THIN DISPERSED AMORPHIC SILICA", IPC C04B 22/06, C04B 103/61. The invention relates to the construction materials industry and, in particular, to the production of modified additives for concrete, mortar and dry mortar. The technical result of the invention is the provision of a homogeneous firing product in composition, elimination of underburning and burning of raw materials, increasing the strength of concrete and mortars, increasing corrosion resistance. In the method for producing finely dispersed amorphous silica, including grinding siliceous rock with subsequent firing, an opal-cristobalite rock preliminarily dried to a moisture content of 1-5% is used as a siliceous rock, grinding to a particle size of 0-5 mm, firing with a gas temperature at the entrance to the furnace is 650-1000 ° C, then - the supply of calcined material with a temperature of 70-90 ° C to the mill-activator with grinding it to a specific surface of 200-4000 m ² / kg.

The disadvantage of this method is that during firing, amorphous silicon transforms to crystalline, this increases the strength of the product, but reduces its bioavailability and effectiveness in areas such as sorption purification of food and non-food liquids, cosmetology, animal husbandry, etc.

Disclosure of Invention

The objective of the invention is to provide a method for producing finely dispersed amorphous silica, which allows you to produce a product with a high content of amorphous silicon and characteristics that allow the use of this product in areas such as sorption purification of food and non-food liquids, cosmetology, animal husbandry and other areas in which material with high sorption characteristics and the maximum amount of bioavailable silicon.

The problem is solved due to the fact that the method of producing finely dispersed amorphous silica includes grinding and drying of opal-cristobalite rock. The opal-cristobalite rock is preliminarily crushed to a size of not more than 5 cm. A drying and crushing unit is prepared: after switching on, a constant supply of air-gas mixture heated in a heat generator to a temperature of 150-600 ° C is started. Then the prepared opal-cristobalite rock is fed to the input tape of the drying and crushing unit through a metering device, which is interconnected with the rotor and burner of the unit. Then the rock is fed into the rotor section, where it is crushed with a constant supply of heated air-gas mixture, resulting in a powder with a particle size of from 0.01 to 350 microns and a moisture content of 1% to 5%. Next, the resulting powder is fed into the chimney, in which the powder is cooled as a result of heat exchange with ambient air. Then it is fed into a bag filter, passing through which a fine powder with a high content of amorphous silicon is deposited in the screw section, and the air purified in the filter is taken into the environment.

Spread in nature. The content of free silicon dioxide in the earth's crust is 12%; it is also part of the rocks in the form of various silicates or mixtures with other minerals (granites). Quartz is one of the most common minerals; tridimite, cristobalite, finder (natural quartz glass), chalcedony, and opal are much less common. Small, differently oriented quartz crystals form vein quartz. When rocks are destroyed, quartz sands arise, the compaction of which leads to the formation of sandstones and quartzites. The purest quartz is rock crystal, whose crystals can reach several meters and weigh tens of tons. Single crystals of quartz are transparent, colorless (rock crystal) or colored with impurities in violet (amethyst), black (marion), yellow (citrine), smoky (raukh-topaz) color. Varieties of latent crystalline forms of quartz: pink-red carnelian, bluish sapphirin, apple-green chrysoprase, banded agates and onyx, finely colored jasper, flint and hornfelses. The amorphous “noble” opal is unique, consisting of homogeneous colloidal particles with a diameter of 0.1-0.3 microns, densely packed in ordered agglomerates; the water content in it is less than 1% by weight (for most ordinary opals 4-9%). Natural silica deposits also form tripoli, flask, diatomite, etc. Shells of diatoms, skeletons of some sponges are built from silica; it strengthens the stems of plants: horsetail, bamboo, reed; contained in straw. Silicon dioxide is responsible for the silicification of forms of living organisms and plants. In the blood and plasma of a person, the concentration of silica is 0.001% by weight.

As a result of the application of this method, finely dispersed amorphous silica is obtained having the following properties:

1. a larger specific surface, in contrast to crystalline silica, so it is used in winemaking technology. Fine-dispersed amorphous silica forms a dense filtering mesh that perfectly precipitates particles suspended in wine and even colloids;

2. the presence of aluminosilicate sites with sorption activity;

3. the presence of opal forms of silicon (amorphous non-crystalline silica), allowing the finely dispersed amorphous silica obtained by this method to give new properties to various compositions, materials and products, for example, when mixing finely divided amorphous silica with air lime, the mixture acquires the property of a hydraulic binder, and when mixed finely dispersed amorphous silica with Portland cement its sulfate resistance increases;

4. the ability as an active mineral additive to bind lime into low-basic calcium hydrosilicates according to the scheme: SiO ₂ + Ca (OH) ₂ + n (H ₂ O) = CaOSiO ₂ H ₂ O;

5. the ability to bind calcium hydroxide in the presence of water at ordinary temperature (due to the presence of a high amount of silicon in a reactive form);

6. high exchange capacity and sorption activity, which allows it to be used for the preparation of highly active bleaching earths, effectively clarifying vegetable and mineral oils due to the complete binding of dyes and phosphates;

7. a special structure that can serve as a matrix for the formation of the structure of polymer compositions, and as a result, thicken (increase viscosity) fluid compositions, increase the strength characteristics and wear resistance of materials such as plastic, rubber, rubber, etc. This property is also used in production paints, varnishes, glues, sealants, pastes, ointments, lubricants, plastics, etc .;

8. the presence of multifunctional centers, which, in combination with a large specific surface area, bind and remove various toxins, salts of heavy metals, radionuclides from animals and humans.

The implementation of the invention

FIG. 1 The dependence of the main parameters of the equipment on the feed rate of the feed material with a humidity of 48% upon receipt of finely dispersed amorphous silica with a particle size of less than 50 microns.

FIG. 2 The graph of the dependence of the main parameters of the equipment on the feed rate of the raw material with a humidity of 50% upon receipt of amorphous silica with a particle size of less than 50 microns.

A method of obtaining a finely divided amorphous silica, comprising the following steps:

1. the opal-cristobalite rock is crushed to a size of not more than 5 cm, and its input relative humidity is determined, on which the setting mode of the drying-crushing unit will subsequently depend;

2. start the drying and crushing unit;

3. heat the air-gas mixture in the heat generator with a burner, while the temperature regime in the heat generator is maintained within the range of 150-600 ° C;

4. serves a heated air-gas mixture with a smoke exhauster in the rotor section;

5. prepared opal-cristobalite rock is fed to the input tape of the drying and crushing unit through a metering device;

6. the rock enters the rotor section, where it is crushed with a constant supply of heated air-gas mixture;

7. get a powder with a particle size of from 0.01 to 350 microns and a moisture content of 1-5%, while the material, while retaining natural amorphous silicon, acquires the necessary fine dispersion, humidity and uniformity;

8. In the process of air transportation through the air ducts, heat exchange occurs with the surrounding air and the powder cools down;

9. the cooled powder, falling into the bag filter, is deposited on the surface of the filter bags, and the cooled purified air leaves through the outlet pipe into the atmosphere;

10. When excess powder is formed on the surface of the filter cloth, air permeability drops and the sleeves are automatically shaken;

11. The powder, under the action of gravity, falls into the lower part of the filter, from where it enters the packaging with the help of a screw.

The exact parameters and operating modes of the drying and crushing unit depend on the required fraction of the finished product, the volume of supplied prepared opal-cristobalite rock, the volume of supplied heated air-gas mixture and the required capacity (see Fig. 1, Fig. 2).

Examples of the use of finely divided amorphous silica

Example 1

For the production of diatomite heat-insulating molded products by the method of fading additives, finely dispersed amorphous silica produced by the proposed method was taken and mixed with organic dispersed additives, after which the mixture was moistened. Extrusion method of the resulting mass formed products subjected to further firing. During the firing process, organic additives burned out with the formation of pores, and diatomite particles sintered until the product acquired the necessary strength. Masses based on finely dispersed amorphous silica are able to retain a large amount of water, while possessing the high plastic strength necessary to maintain the shape of the raw material after forming by extrusion. For example, raw clay with a moisture content of 22-25% can be obtained from brick clays on a tape process, and 60-80% (by weight) from sawdust-diatomaceous matter.

Example 2

In the production of varnishes at St. Petersburg Paints LLC, St. Petersburg, finely dispersed amorphous silica from 0.01 to 50 μm was used to increase film strength, resistance to abrasion, low temperatures, and to add varnish to dullness. Particles of finely dispersed amorphous silica are distributed in the varnish layer over the entire area, while: increasing strength, durability, hiding power; forming additional bonds that improve the adhesion of subsequent layers. It is the finely dispersed porous structure of finely dispersed amorphous silica that gives the varnish elasticity, resistance to cracking under atmospheric influences. Chemical inertness combined with the hardness of the diatom structure makes the materials obtained almost ideal for long-term operation, even in aggressive environments. Thanks to the various forms of microscopic particles, any degree of necessary gloss can be created when they are exposed to and scattered light.

Example 3

On the premises of Bogatyrskaya Sloboda LLC, Togliatti, Samara Region in the production of growing mirror carp was used feed with mineral additives. Fine dispersed amorphous silica was taken as one of the components of the mineral component. The daily feed dose, taking into account the temperature of dissolved oxygen and the weight of the fish, was 3 g / kg. Two groups of fish were formed, in one of which they used ordinary food, and in the other, food containing finely divided amorphous silica. The results of the experiment conducted over 6 weeks are presented in table 1.

According to the data presented in the table, the live weight of carp at the beginning of feeding varied with slight deviations in both groups ranging from 18.15 to 18.2. Throughout the feeding, the fish in the experimental group more actively gained weight and height. Upon further observation of behavioral reactions, it was noted that carps in the experimental group adapted more quickly to changes in the diet than the control group.

Table 1

Experience period, weeks Group 1 (control) 2 (experimental) 1 18.15 18.2 2 27.6 27.9 3 36.56 37,2 4 47.5 48,4 5 54,2 56.1 6 56.8 68,2 Control / experimental,% 2.05 5.85 Growth per experience, g. 48.64 49.9 Control / experimental, g. 1.26 4.29

The advantages of the method of obtaining finely divided amorphous silica:

- Due to the gentle treatment under conditions of simultaneous drying and grinding of diatomite, the material breaks along the boundaries of the diatom valves, allowing you to save nanoscale pores and increase the specific surface.

- Due to gentle drying, the opal form of silica (amorphous form) is preserved in the air flow, which determines the special properties of the obtained product, while firing leads to the transition of amorphous silicon to cristobalite and tridymite, which are not able to participate in sorption processes.

- The claimed method allows to obtain a product with different particle size distribution and various humidity while maintaining amorphous silicon due to the mobility of technological parameters.

All of the above confirms the fulfillment of the task, namely, the creation of a method for producing finely dispersed amorphous silica, which allows you to obtain a product with a high content of amorphous silicon and with characteristics that allow it to be used in areas such as sorption purification of food and non-food liquids, cosmetology, animal husbandry and others areas in which a material with high sorption characteristics and a maximum amount of bioavailable silicon is required.

Industrial applicability is proved by examples 1, 2, 3.

Claims (1)

A method of producing finely dispersed amorphous silica, including grinding and drying of an opal-cristobalite rock, characterized in that the previously opal-cristobalite rock is crushed to a size of not more than 5 cm, then a drying and crushing aggregate is prepared: after switching on, a constant supply of heated in the heat generator to a temperature of 150 begins -600 ° C air-gas mixture; after which the prepared opal-cristobalite rock is fed to the input belt of the drying and crushing unit through a metering device, which is interconnected with the rotor and the burner of the unit, then the rock is fed to the rotor section, where it is crushed with a constant supply of heated air-gas mixture, as a result of which a powder with a particle size of from 0.01 to 350 microns and a moisture content of 1% to 5%, then the resulting powder is fed through an air duct, in which, as a result of heat exchange with ambient air, the powder is cooled into a bag filter, passage through which a fine powder with a high content of amorphous silicon is precipitated in the screw section, and the air purified in the filter is taken into the environment.

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