Nanostructures based on carbon and silicon dioxide to improve the properties of building and structural materials

The article presents hardware and technological solutions for obtaining a product containing silicon dioxide from nanodispersed dust of gas cleaning of silicon production, intended to improve the properties of building and structural materials. To obtain nanostructures of carbon and silicon dioxide of the required quality, allowing to improve the properties of building and structural materials, a complex resource-saving technology of their high-tech production was developed. The necessary characteristics of nanodispersed modifying additives have been determined. A technological scheme has been developed; technological operations of thermal vortex enrichment are described. The material balance of thermal vortex enrichment is given.


Introduction
Development of technologies at present are energy and resource conservation [1-3], green technologies [4]. Development of technologies allowing to improve the quality of associated mineral raw materials without prejudice to the main technological process of silicon production [5][6][7][8] makes it possible to obtain nanodispersed dust (ND) containing carbon in the form of carbon nanotubes (CNTs), fullerene and silicon dioxide. The modifying effect of CNTs [9-10] and silicon dioxide [11][12][13][14] is becoming increasingly popular in various industries, including construction. One of the promising directions for the development of the use of these nanoparticles is road construction.

Developed product
This product was developed as part of a project to create a high-tech production of nanostructures based on carbon and silicon dioxide.

Characteristic of output product
The output product described in this article is a powdery concentrate of nanostructures containing silicon dioxide. Bulk density, kg/m 3 to 360 GOST R 54246-2010 Granulometric composition of the packaged product (after long-term storage and self-coagulation processes), % Individual nanoparticles: Agglomerates: -small, more than 1 micron; -medium, more than 10 microns; -large, more than 45 microns not less than 63.5 no more than 30.0 no more than 5.0 no more than 1.5 GOST R 8.755-2011

Technological scheme of thermal vortex enrichment
The general process flow diagram is shown in Figure 1.

Characteristic of raw materials
Nanodispersed dust for performing thermal vortex enrichment is a product of collection in the gas cleaning system of silicon production. Table 2. Quantitative composition of nanodispersed dust.
Parameter Content, % Dust chemical composition -SiO2, not less than -Fe2O3, no more than -Al2O3, no more than -CaO, no more than -С, no more than 84.3 0.6 1.0 2.1 11.5 To perform thermal vortex enrichment, materials with the characteristics presented in Table 3 are used.

Description of the thermal vortex enrichment
The process is a thermal vortex enrichment of nanodispersed dust. The dust is fed tangentially to the bottom of the furnace. Burning gas is also tangentially fed through the second inlet pipe. Due to tangential input and natural convection, an upward vortex with a temperature of 700-850 °C is formed in the working chamber of the furnace. At a given temperature, the carbon contained in the initial nanodispersed dust is oxidized to carbon dioxide. Decarbonized nanodispersed dust together with carbon dioxide is taken from the upper part of the furnace. Decarburized nanodispersed dust is a product of MD 1. A description of the implementation of thermal vortex enrichment is given in Table  4.  Table 5. Control of parameters is carried out using the measuring equipment of the experimental stand. The layout of the technological equipment is shown in Figure 2.

Material balance
The material balance of thermal vortex enrichment is shown in Table 6. The technological process, which is the implementation of thermal vortex enrichment, does not produce waste that requires neutralization.

Conclusion
The developed technology of thermal vortex enrichment of dust from gas cleaning of silicon production allows not only to improve the ecological situation, to increase the profitability of the main production, but also to obtain innovative nanostructures for modifying road materials, concrete and asphalt concrete. The requirements for the quality of the produced modifying nanoparticles and the IOP Publishing doi:10.1088/1757-899X/1159/1/012046 5 quality of the feedstock and materials used for their production from the waste gases of an ore-thermal furnace for silicon production have been established.