RU2637011C1 - Method for producing amorphous silicon dioxide and amorphized product obtained according to method - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method for producing amorphous silicon dioxide from rice husk ash is described, which is processing the feedstock natural moisture in the reactor of the oxygen or air-water mixture with obtaining of furnace gasificate and with excepting diffraction peaks of crystalline silica in the diffraction pattern from RHA (rice husk ash) and separating the impurities and dimensional agglomerates in the air-jet separator, downloading the product automatically in the acid cleaning station, which is further washed with purified water. After washing to a neutral wash water pH, the product is sent to an alkaline treatment module where a KOH solution of the optimum concentration is added and heat treated until the silicon-containing portion of the RHA is completely dissolved. Mineral acid is added to its resulting alkaline solution, the reaction mixture is warmed up with a gradual lowering of pH to neutral values, at which there is a drop of white flaky or a gelatinous precipitate that weathered, centrifuged, separated from the solution and washed with distilled water until a neutral wash water pH. The amorphized product obtained according to the method, is an amorphous silica of snow-white colour in the form of the single face plates of a nanometer size, articulated in different ways, the size of this type of grain is 2-12 microns with a possible further electrostatic conglomeration characterized by loss of moisture at 105°C 2-8 wt %, the mass loss up to 1000°C 4-14%, pH of the slurry to 5.5-8 and the content of SiO₂ in the calcined product of more than 99.99 wt % and heavy metals and chloride - lower limits of detection on the surface area of 180-360 m²/g.

EFFECT: method is developed that allows to obtain a product with an active surface demonstrating different particle sizes, their morphology and density.

3 cl

Description

The invention relates to methods for processing rice wastes in automatic plants to produce a high-purity amorphized product, which is a raw material for use in rubber products and the tire industry.

Environmentally friendly renewable natural materials are currently attracting increasing attention with the aim of further processing and obtaining products important for industrial applications.

Rice husk itself (RH), as well as the product of its oxidative heat treatment - ash (RH) - are actively demanded by the industry because their composition, to a greater extent, corresponds to silicon dioxide in an amorphous form. This is what determines the demand of the metallurgical and construction industries for these products. Potentially they are suitable as sources for the production of metallurgical silicon and a number of important organic substances: furfural, xylitol, rice oil, phytin, etc.

By itself, high-purity amorphous silicon dioxide (DC), which is a product of the processing of ZRSh, is actively used as a component of rubber masses (RTI), an effective sorbent for pharmaceuticals and a filler for paints, chemicals, water treatment, or as an additive in the cosmetics industry.

The prior art method for producing amorphous silicon dioxide from rice husk, comprising carbonization of rice husk and oxidative firing, and before the stage of carbonization, the rice husk is washed with water and / or mineral acid, then carbonization is carried out at 120-500 ° C, after which the resulting ash is ground and subjected to oxidative calcination in a fluidized bed at 500-800 ° C (see patent RU 2061656, class C01B 33/12, publ. 06/10/1996). The disadvantages of this method are the insufficient degree of purification of the resulting silica and the lack of a single automatic installation that implements the method, which limits the possibility of its effective use in industry.

Closest to the invention, the technical solution is a method for producing amorphous silicon dioxide from rice husk ash (see patent RU 2592533, class C01B 33/12, published July 20, 2016), which consists in processing raw materials of natural humidity in an oxygen or air reactor -aqueous mixture to obtain a furnace gasifier and excluding from diffraction maxima the diffraction maxima of crystalline silica in the diffraction pattern and separation from mechanical impurities and dimensional agglomerates in an air-jet separator, loading the product in an automatic normal mode to the acid treatment station, where it is additionally washed with purified water. This method is not a universal low-waste technology for separating mechanical impurities, the carbon component, mineral salts of metals, their oxides and hydroxides, which does not allow to vary the surface properties of the product.

The technical problem to which the invention is directed is to eliminate the noted drawback and expand the arsenal of technical means. The technical result consists in ensuring the versatility of the method and the exclusion of its dependence on the area of rice growth and the method of obtaining RH. The method was tested on RS obtained from rice from the cultivation areas of the Krasnodar Territory, Adygea, India, China.

The problem is solved, and the technical result is achieved due to the fact that in the method of producing amorphous silicon dioxide from rice husk ash, which consists in processing the feedstock of natural moisture in an oxygen-or air-water mixture reactor to produce a combustion gasifier and excluding crystalline diffraction maxima from the ZRS silica on a diffractogram and separation from mechanical impurities and overall agglomerates in an air-jet separator, loading the product in an automatic mode into an acid station cleaning, where it is additionally washed with purified water, the acid treatment station is equipped with mechanical activators and operates in it in a semi-automatic mode, implementing several washing of the dry product, while after washing to neutral pH of the washing water at the same station, the product is sent to the alkaline treatment module where the optimal concentration of KOH solution is added to the wetted purified RPS and heat treated with mechanical and ultrasonic activation until the silicon soda is completely dissolved of the remaining part of RHC, the carbon remaining after this is activated and adsorb residual amounts of metals, and mineral acid is added to the resulting alkaline solution in the hydrolysis unit at room temperature and intensive activation, the reaction mixture is heated with a gradual decrease in pH to a neutral value, at which white precipitation occurs flocculent or jelly-like precipitate, which is aged at a controlled humidity and temperature for at least 10 hours, after which it is centrifuged, separated from the solution and washed with distilled water to a neutral pH of the wash water, the residue is suspended and dried at 130 ° C for 10-15 hours. The residue may be suspended in ethanol. The amorphized product obtained according to the method is a white-white amorphous silica in the form of nanometer-sized plates articulated in different ways with one face, with a grain size of 2-12 μm with possible further electrostatic conglomeration, characterized by moisture loss at 105 ° C - 2-8 wt.%, Weight loss up to 1000 ° C - 4-14%, suspension pH - 5.5-8 and SiO ₂ content in the calcined product - more than 99.99 wt.% And heavy metals and chlorides - below the detection limits on the surface area 180-360 m ² / g.

The feedstock is natural moisture condensate, obtained by treating the oil in the reactor in an oxygen or air-water mixture in order to obtain flue gas. The criterion for the suitability of ZRS for the production of DC is the absence of pronounced diffraction maxima of crystalline silica in the diffraction pattern of ZRS.

To obtain a recreation center ZRSh, it is processed into a commercial product in a modular installation consisting of a loading hopper, an air separator, an acid cleaning-washing station, an alkaline treatment unit, a hydrolyzer, a centrifuge, a dehumidifier, and a receiving hopper.

In the first stage, the ZRSh is subjected to separation from mechanical impurities and overall agglomerates in a standard commercially available air-jet separator.

At the next stage, the product is automatically loaded into an acid treatment station, which is a collection of containers made of a material inert to mineral acid, at least two pairs of which are used for filling and overflowing acid and drinking-water quality, respectively. The remaining tanks play the role of closed reactors for processing RRS. The tanks are connected by tubes hermetically inert to acid, the pumping of the liquid phase is carried out by chemically resistant pumps. Pump performance, liquid lifting height, tube diameter, bulk product volume, tank size and the station as a whole - are correlated. The station is equipped with mechanical activators and operates in a semi-automatic mode, realizing at least three times washing of the dry product.

After washing to a neutral pH of the wash water at the same station, the product enters the alkaline treatment module, similar in design to the acid treatment station, but made of alkali-resistant materials and having several ultrasonic activators in the tank volume. At the same time, an optimal concentration of KOH solution is added to the moistened purified RRS and subjected to heat treatment with mechanical and ultrasonic activation for the calculated time. In this case, the silicon-containing part of the ZRSh is completely dissolved, and the carbon remaining after this is activated and adsorbs the residual amounts of metals. Washed with water and subsequently heat-treated, it is itself a commercially valuable product. To plant DC with variable surface properties, mineral acid is added to the resulting alkaline solution in the same hydrolysis unit at room temperature and intensive activation of various types. There is a strong heating of the reaction mixture with a gradual decrease in the pH value, which requires continuous monitoring with varying process speeds. At a pH close to neutral, a white flocculent or jelly-like precipitate forms. Variation in the surface properties of DC is carried out by changing the pH of hydrolysis and the aging time of the gel. Depending on the required surface area and the number of surface silanol / siloxane groups, the addition of acid is stopped when the desired pH value is reached, and the reaction mixture is continued to be heated with ultrasonic activation in the bulk or by a submersible waveguide (depending on the required properties) until the process is completed. The precipitate formed is aged at controlled humidity and temperature with the possible application of ultrasound for at least 10 hours, after which it is centrifuged, separated from the solution and washed with distilled water until the pH of the wash water is neutral. The residue is suspended, for example, in ethanol and dried at 130 ° C for 10-15 hours, packaged in a sealed foil container.

The color of the product is snow-white, the morphology of particles is variously articulated by one face of a nanometer-sized plate with a grain size of 2-12 microns with possible further electrostatic conglomeration. Moisture loss at 105 ° C - 2-8 wt.%, Weight loss up to 1000 ° C - 4-14%, suspension pH - 5.5-8, SiO ₂ content in the calcined product - more than 99.99 wt.%, Heavy metals and chlorides - below the detection limits, surface area 180-360 m ² / g

Thus, depending on the operating mode of the alkaline treatment station, it is possible to obtain a product with an active surface that demonstrates various particle sizes, their morphology and density. It is these parameters that determine the chemical activity, dispersion, dispersibility, water and oil absorption, as well as frictional properties of DC.

Claims (3)

1. A method of producing amorphous silicon dioxide from rice husk ash (RRS), which consists in processing the feedstock of natural moisture in a reactor of an oxygen or air-water mixture to obtain a combustion gasifier and eliminating from the RRS the diffraction maxima of crystalline silica in the diffraction pattern and separation from mechanical impurities and overall agglomerates in an air-jet separator, loading the product automatically into an acid treatment station, where it is additionally washed with purified water, which distinguishes The fact that the acid treatment station is equipped with mechanical activators and operates in it in a semi-automatic mode, realizing several washing of the dry product, and after washing to neutral pH of the washing water at the same station, the product is sent to the alkaline treatment module, where ZRSh add a KOH solution of optimal concentration and heat treated with mechanical and ultrasonic activation until the silicon-containing part of ZRSH is completely dissolved, and the remaining after that carbon is activated and adsorbs residual amounts of metals, and mineral acid is added to the resulting alkaline solution in the hydrolysis unit at room temperature and intensive activation, the reaction mixture is heated with a gradual decrease in pH to a neutral value, at which a white flocculent or jelly-like precipitate precipitates, which age with controlled humidity and temperature for at least 10 hours, after which it is centrifuged, separated from the solution and washed with distilled water for a neutral pH of the washing water, the residue slurried and dried at 130 ° C for 10-15 hours. 2. The method according to p. 1, characterized in that the residue is suspended in ethanol. 3. An amorphized product obtained according to the method according to claim 1, which is amorphous silica of a white-white color in the form of nanometer-sized plates articulated in various ways with one face, with a grain size of 2-12 μm with a possible further electrostatic conglomeration, characterized by moisture loss at 105 ° C 2-8 wt.%, weight loss up to 1000 ° C 4-14%, suspension pH 5.5-8 and SiO ₂ content in the calcined product of more than 99.99 wt.% and heavy metals and chlorides - below the detection limits on the area surface of 180-360 m ² / .