RU2353578C1 - Method of quartz raw material enrichment - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used in chemical industry for quartz raw material enrichment. Initial raw material is preliminarily crushed and decrepitation with further thermocrushing in liquid medium is carried out. After final mechanic crushing with further crushing, magnetic separation and flotation are carried out. Chamber product of flotation after ultrasonic processing, filtration and drying is exposed to tempering at temperature 550-700°C with further processing with mixture of hydrochloric and hydrofluoric acids at temperature not higher than 20°C. Flotation and ultrasonic processing of chamber product are realised in pulp with PH=3.0-4.0. Preparation of pulp for flotation is carried out using mineral acid, for example sulfuric, and crushing of initial quartz raw material is carried out to coarseness not more than 0.4 mm.

EFFECT: claimed invention allows to extend raw material base for obtaining pure silicon dioxide.

4 cl, 1 dwg, 2 tbl

Description

The invention relates to the enrichment of quartz raw materials and can be used to obtain highly pure quartz product with an impurity content of not more than 1 × 10 ^-4 wt.%.

Alkaline, alkaline earth, heavy metals, iron, carbon, free and bound water have a detrimental effect on the quality of quartz glass products. There are various methods for the enrichment of quartz-containing minerals. Their diversity is due to both the physicochemical characteristics of the raw materials of a particular deposit, and the requirements for an enriched product.

So, there are known methods for the continuous purification of silica powder by thermochlorination: RU No. 2198138 "Method for cleaning particles of SiO ₂ , a device for implementing the method and grain obtained according to the method" (СВВ 33/12, 05/05/2000), EP-A1 No. 737653 "The method of continuous purification of quartz powder" (10.16.1996). These methods are characterized by a high degree of danger, and also require highly qualified service. For example, when the process is conducted at a temperature above the optimum, softening of quartz grains with the formation of agglomerates is possible, which complicates further gas access to the surface of individual grains and the degree of purification of quartz decreases. Another significant drawback of this group of methods is the need for very fine grinding, not higher than 0.25 mm.

In practice, in order to eliminate contamination from the open surfaces of quartz raw materials of natural origin, preliminary wet methods of chemical treatment are common. So, according to US patent No. 4983370 "Purified quartz and method for its purification" (СВВ 33/12, 02/06/1990), quartz sand is subjected to preliminary treatment by thermo-chlorination by two-stage flotation, magnetic separation, and then by etching in fluorine acid, resulting in a product with an impurity content of less than 1 × 10 ^-4 wt.%.

Known methods for producing crystalline quartz by recrystallization of a mixture of silica-containing raw materials, mainly representing amorphous silica, with inorganic additives: RU No. 2062253 "Method for producing crystalline quartz" (С01В 33/12, July 15, 1996).

The known "Method for the enrichment of quartz raw materials" according to patent RU 2131779 (B03B 7/00, 03/25/1998), in which the quartz raw material is additionally subjected to electroplasma treatment in a discharge chamber with flow-through washing of the products of processing with dielectric liquid.

Enriched silica is used in the production of quartz glass for the chemical and optical industries, as well as for the manufacture of optical fibers and semiconductors. The purity of quartz glass products is high. Correspondingly high are the purity requirements for the feedstock.

For high-quality feedstock, a "Method for processing quartz-containing raw materials" was developed according to patent No. 2182113 (СВВ 33/12, December 4, 2000). According to the technical nature, the presence of similar, essential features, including a set of redistributions in the technological scheme, this method is selected as the closest analogue (prototype).

The technical solution for the prototype proposed a method of enrichment of quartz raw materials, including preliminary mechanical crushing of the feedstock, decrypting, followed by processing in a liquid medium at a temperature of 6-20 ° C, final mechanical crushing to a particle size of not more than 2 mm, followed by grinding, magnetic separation, two-stage flotation, ultrasonic treatment and heat treatment of the final product. The attractiveness of this method lies in its high environmental friendliness, and a significant drawback is that the necessary degree of purity is achieved only when using high quality natural quartz raw materials. For raw materials of ordinary quartz-containing deposits, this method is not effective enough and does not allow to obtain an enriched product of the required quality for high-tech industries.

It is known that impurities in quartz raw materials are presented in the following forms:

- associated mineral impurities that do not have a chemical bond with quartz crystals;

- mineral impurities enclosed inside a quartz grain or inside a quartz aggregate;

- gas-liquid, liquid and gas inclusions;

- mineral impurities that have surface chemical and / or physical bonds with quartz crystals;

- impurities in the form of ions bound in the crystal lattice of quartz, such as aluminum and iron, having a trivalent form. As a rule, the accompanying impurities are lithium, potassium, sodium and hydrogen ions.

Of the listed types of impurities for the prototype method, mineral impurities, gas-liquid, liquid and gas inclusions located inside the quartz raw material or inside the quartz aggregate are of particular difficulty. Without opening them and etching with mineral acids, this type of impurity is practically impossible to remove.

Another significant disadvantage of the prototype, as applied to ordinary raw materials, is the instability of the liquid system based on activated water, which does not provide stable acidity of the pulp during flotation and ultrasonic scrubbing. On the other hand, using activated water, it is practically impossible to achieve significant pulp acidity, the most real acidity is pH = 4 ÷ 5.5, as in the prototype. For flotation of pulp based on ordinary raw materials, an increase in acidity of the order of pH = 3-4 is necessary.

In the prototype, the grinding of raw materials before its physico-chemical processing is carried out to a particle size of -0.5 mm, which is sufficient for high-quality raw materials, but does not provide a sufficient degree of opening of individual grains of quartz for ordinary raw materials.

The objective of the invention is the expansion of the raw material base for the production of quartz glass for the chemical and optical industries, as well as for the manufacture of optical fibers and semiconductors.

The technical result is the creation of an economical technology for producing a quartz product, the high quality of which will allow using the resulting product in the manufacture of semiconductor devices, optics and other high-tech industries.

The technical result is achieved in that in the method of enrichment of quartz raw materials, including preliminary crushing of the feedstock, decrypting followed by thermal crushing in a liquid medium, final mechanical crushing followed by grinding, magnetic separation, flotation, ultrasonic treatment of the flotation chamber product and its calcination to obtain the final product , the chamber flotation product after ultrasonic treatment, filtration and drying is calcined at a temperature of 550-700 ° C, followed by processing with a mixture of hydrochloric and hydrofluoric acids at a temperature not exceeding 20 ° C, while flotation and ultrasonic treatment of the chamber flotation product is carried out in a pulp with pH = 3.0-4.0, and the preparation of pulp for flotation is carried out using a mineral acid, for example sulfuric and grinding of the initial quartz raw material is carried out to a particle size of not more than 0.4 mm

Consider the proposed technological scheme in terms of its technical nature.

An important common feature of technological schemes both according to the prototype and according to the proposed solution is the introduction to the beginning of the scheme for processing quartz-containing raw materials of heating to a temperature of 850-950 ° C, which corresponds to the temperature interval for the completion of the decryptation of quartz, followed by its cooling in a liquid medium at a temperature of 6 -20 ° C. When heated, preliminary softening (cracking) of quartz grains occurs along the boundaries of impurity films due to the difference in the thermal expansion coefficients of quartz and impurity films. Thus prepared material is easily crushed and crushed, with maximum opening of the surfaces of grains containing impurity films.

The magnetic part of the opened impurity films is separated from the quartz grains during magnetic separation, and the rest during flotation and ultrasonic cleaning.

In the process of two-stage flotation followed by ultrasonic scrubbing, almost complete removal of mineral impurities that have surface chemical and / or physical bonds with quartz crystals, as well as impurities in the form of ions, is achieved.

Of the above types of impurities of quartz by the prototype method, it is not possible to completely remove gas-liquid, liquid and gas inclusions located inside the quartz grain or inside the quartz aggregate. In this regard, the proposed technological scheme includes an additional redistribution aimed at opening gas-liquid, liquid and gas inclusions and cleaning their chambers (vacuoles) from impurity elements. Such an additional redistribution is the treatment of the chamber flotation product after calcination at a temperature of 550-700 ° C with a mixture of hydrochloric and hydrofluoric acids, followed by decantation, washing, filtering and drying the final product.

Consider the technical nature of the proposed changes introduced into the technological scheme of the prototype. We analyze each change in terms of technological feasibility and economic efficiency.

- In the proposed solution, the second stage of high-temperature processing (the first stage is decryptation) is carried out in two successive stages: drying at 300-500 ° C, directly calcining at 550-700 ° C.

The choice of temperature ranges is due to the following:

the purpose of calcining the second stage of high-temperature processing is to prepare (open) the quartz grains for acid etching as much as possible. It is known that at temperatures above 700 ° C, the onset of fusion of pores and silica microcavities is possible, that is, the onset of sintering is possible, as evidenced by a sharp decrease in the specific surface area of the sample. As a result, the water desorbed from the walls of the cavities remains in the bulk of the grain, and the organic components remaining in the melted cavities also pyrolyze in the bulk of the silica matrix and form inclusions of the carbon phase inherited by the glass.

The lower calcination limit is due to the fact that the product is dried to 550 ° C without changing the structure of the silica matrix, while not only physically sorbed molecular water and its associates are completely removed, but also residual organic components sorbed on the grain surface.

In this regard, it is rational to increase the drying time at 500 ° C and reduce the calcination time at 700 ° C, which, firstly, gives an energy gain for the process as a whole, and, secondly, reduces the risk of the start of fusion of quartz grains.

- Introduction to the technological scheme of redistribution related to the processing of the flotation chamber product immediately after calcination (without quartz cooling) with a mixture of hydrochloric and hydrofluoric acids with a temperature of no higher than 20 ° C, allows to achieve a deep degree of purification of quartz from impurities by opening gas-liquid, liquid and gas inclusions and cleaning of their chambers (vacuoles) from impurity elements.

Moreover, to ensure complete and effective contact of individual grains of quartz with acids, the quartz product is fed into the acid solution in a uniform flow.

In the practice of enrichment of quartz, the use of various acids is known, including the use of only hydrochloric or only hydrofluoric acids. The authors selected a mixture of these acids because of the lower aggressiveness of the mixture, and therefore less stringent requirements are imposed on the quality of the equipment.

The ratio of acids in the mixture is not indicated due to the fact that natural quartz raw materials are presented in a wide variety of qualitative and quantitative impurities. Therefore, taking into account the composition of impurities for each specific raw material, it is necessary to calculate the optimal ratio of acids in the mixture according to the results of the chemical and phase composition of the raw material.

It is not recommended to exceed the etching temperature above 20 ° C, as the unproductive loss of acids increases significantly due to the transition to the gas phase, which is economically and environmentally unfeasible.

- It is possible to increase the technological parameters of the flotation process by enhancing the flotation activity and selectivity of the collector in the conditions of the correct selection of pulp pH.

The optimal choice of pulp pH during flotation is one of the primary tasks. The optimal pH value provides the best dissociation of collectors, which, firstly, will provide an effective separation of primers, layers, etc. from quartz grains, and secondly, it strengthens the contact of impurities with collectors in turbulent flotation conditions, that is, the efficiency of collectors performing the kinetic function of fixing and flotation of impurities increases significantly.

At the same time, various mineral acids (sulfuric acid is more effective) inhibit the flotation of silicates, drastically reducing the sorption of the anionic collector. As a result, the yield of the target product is increased.

In the proposed technical solution, in contrast to the prototype for flotation, pulp is prepared with pH = 3-4, and the acidity is ensured by the introduction of a mineral acid, for example sulfuric, into the pulp. The refusal to use activated water with pH = 4-5.5 is due to the fact that, as mentioned above, activated water is a rather unstable system and does not provide stable acidity of the pulp during flotation and scrubbing.

The increase in the acidity of the pulp is caused by the need to activate the flotation process, especially for quartz raw materials with a high content of impurities. During flotation and subsequent washing, quartz is freed from impurities such as related mineral impurities that do not have a chemical bond with quartz crystals, mineral impurities that have surface chemical and / or physical bonds with quartz crystals, and impurities in the form of ions bound in a crystal lattice quartz, including hydroxyl group (OH).

- In the process of rubbing under the influence of ultrasound, quartz is freed from reagents and impurity inclusions.

If the prototype provides a double scrubbing before and after flotation, then in the proposed technological scheme, preflotation scrubbing is excluded for the following reasons:

- increasing the acidity of the pulp and the degree of its stability provides a more complete and efficient cleaning of quartz from impurities in the process of flotation and scrubbing;

- treating the solid flotation product with a mixture of hydrochloric and hydrofluoric acids is an effective process that allows you to extract both mineral impurities contained inside a quartz grain or inside a quartz aggregate, as well as other types of impurities that are not recovered during flotation and rubbing.

- The prototype method was developed for natural quartz raw materials with a reduced content of impurities. In this regard, the fineness of grinding is slightly lower (-0.5 mm) than in the proposed method (-0.4 mm) for ordinary raw materials. The presence in the technological scheme of redistributions of “decryptation” and “thermal crushing” allows grinding to be carried out quite effectively up to -0.4 mm.

The proposed method is easily integrated into the technological scheme of the prototype, in other words, it is possible to create an industrial production with a flexible technological scheme that can be easily reconstructed from one method (according to the prototype) to another (according to the proposed scheme), depending on the raw materials that are sent for processing.

The proposed method of enrichment of quartz is presented in the drawing in the form of a technological scheme indicating the sequence of production conversions.

Comparison of the proposed technological scheme and the scheme of the prototype allows you to identify common features that characterize both methods:

- preliminary crushing of the initial quartz-containing raw material to a particle size of -60 mm;

- heating the material to a temperature of 850-950 ° C followed by thermal crushing in a liquid medium with a temperature of 6-20 ° C;

- final mechanical crushing up to -2 mm followed by grinding;

- dry electromagnetic separation with separation of magnetic tails;

- two-stage flotation by cationic and anionic collectors with the output of the foam product into the tails and obtaining a chamber quartz product;

- ultrasonic chipping of the chamber product;

- washing the chamber product with subsequent thickening, filtration and drying;

- calcination of a dry chamber product.

In the presented claims the following distinctive features from the prototype are claimed:

- if in the prototype the final product was the product after calcination at a temperature of more than 800 ° C, then in the proposed solution, the calcined chamber flotation product is sent to an additional redistribution - etching with a mixture of hydrochloric and hydrofluoric acids at a temperature not exceeding 20 ° C, followed by decantation, washing, filtering and drying the final product;

- calcination of the flotation chamber product is carried out at a lower temperature of 550-700 ° C;

- for flotation, a more acidic pulp is prepared with pH = 3.0-4.0;

- in the preparation of pulp using mineral acid, for example sulfuric;

- ultrasonic scrubbing is carried out only after two-stage flotation using cationic and anionic collectors at pH = 3.0-4.0;

- to increase the degree of opening of impurities, it is proposed to grind quartz raw materials to a fraction of -0.4-0.1 mm;

- the temperature interval for drying the chamber flotation product before calcination is expanded to increase the upper drying boundary to 500 ° C;

- the same drying mode is proposed to obtain the final product after etching with acids.

The presence in the proposed technical solution of the above signs that are different from the signs of the closest analogue allows us to conclude that it meets the condition of patentability “novelty”.

In order to determine the “prior art”, a search was conducted on patent and scientific and technical literature. In the process of analysis carried out on the selected array, partially given in the description section - “analogues”, it was revealed that fundamentally separate signs of the object of protection are known:

- There is a method of complex processing of biotite ores in order to obtain layered silica, described in the book Chelischeva N.F. and others. "Development of non-waste technology for the enrichment of ores of rare and non-ferrous metals" (M., VIEMS, 1977, p.70-71). The method consists of flotation enrichment of biotite raw materials and subsequent acid leaching of the concentrate.

The well-known "Method for producing layered silica" by A.S. USSR No. 1134542 (СВВ 33/12, 02.02.1983), according to which the acid processing of quartz raw materials is carried out before flotation enrichment.

In the above solutions, there is no heat treatment of quartz concentrate before etching with acids.

The use of heat treatment of the chamber product of flotation with subsequent chemical treatment in a mixture of hydrofluoric and hydrochloric acids in the technological scheme of the enrichment of quartz raw materials is known from the materials of the article “Cleaning quartz grains using an electric drum separator” by V. I. Revnivtsev et al. (J. “Ore dressing” No. 4, 1989, pp. 28-30). In this case, the heat treatment is carried out in an oxidizing environment, the so-called oxidative firing. In the proposed enrichment scheme, before treatment with an acid mixture, calcination is used, the main difference from oxidative calcination is the absence of an oxidizing atmosphere, which contributes to the formation of thermally and chemically stable compounds of impurities in the form of nitrides or oxides at elevated temperatures, which complicate further purification of the concentrate and can directly or indirectly lead in quartz glass to undesirable effects of pollution, to harmful coloring or transmission changes . Moreover, the calcination is carried out at a sufficiently low temperature - up to 700 ° C, which guarantees almost complete opening of vacuoles while maintaining the physical stability of the quartz grain. In the proposed method, the calcination is at the end of the technological scheme and is the second high-temperature processing of quartz raw materials: in the head of the enrichment process there is a first heat treatment at a decrypting temperature.

The presence in the proposed method of two high-temperature treatments allows you to open almost all micropores and microcavities and achieve a high degree of purification of quartz.

- Multi-stage heat treatment of silicon dioxide is known from A.S. USSR No. 1085187 "Method for drying synthetic silicon dioxide" (СВВ 33/12, 11/18/82). This solution describes three successive stages of heat treatment at different temperatures, the purpose of which is to reduce the carbon content in the target product. Quartz is heated in the same apparatus with a gradual increase in temperature.

- The use of a mixture of hydrochloric and hydrofluoric acids for etching a quartz concentrate is known from US patent No. 4983370 and British patent No. 1519369 "Method for the production of SiO ₂ " (C01B 33/12, 08/22/75,).

- Purification of impurities by flotation in the presence of sulfuric acid is known according to US patent No. 3914385 "Enrichment of siderite" (С01В 33/12, 06/11/73).

The above analysis showed that in the proposed method for the enrichment of quartz, there are both signs known from the prior art and unknown.

Known and unknown features of the proposed method form a new set and sequence of features of the method. It is this combination and sequence of known and unknown features that is necessary and sufficient to obtain a cleaner target product (SiO ₂ = 99.9998%) compared with the prototype. The claimed new combination and sequence of features allows us to conclude that the criterion of "inventive step".

Tables 1 and 2 show the results of testing the proposed technology. Testing was carried out according to the technological scheme presented in the drawing, on samples of crystalline and granular quartz taken from ordinary veins of the Malo-Kulindinsky deposit. The tables show that the total content of impurities in quartz concentrates obtained using the proposed method is significantly lower than in concentrates obtained by the prototype, and reached an indicator of 0.33-0.34 × 10 ^-4 %. The tables also show that the prototype method is much more sensitive to the quality of the feedstock than the proposed method. Regardless of the quality of the feedstock, the proposed method allowed to obtain final concentrates of almost the same purity: 0.33-0.34 × 10 ^-4 % of impurities.

Table 1
The content of impurities in the feedstock and in quartz concentrates obtained by the prototype and the proposed method (feedstock with an impurity content of 119.3 × 10 ^-4 %) Name of impurities The content of impurities in the feedstock, 1 × 10 ^-4 % The impurity content in the concentrate obtained by the prototype, 1 × 10 ^-4 % The impurity content in the concentrate obtained by the proposed solution, 1 × 10 ^-4 % one 2 3 four Fe 29th 0.1 0.05 Al 21 0.15 0,07 Sa 27 0.15 0.08 TO eleven 0.2 0.05 Na twenty 0.15 0.01 Mn one 0.01 0.01 Mg 6.3 0.05 0.01 Ti 2 0.4 0,03 Cu 2 0.02 0.02 Σ impurities 119.3 1.23 0.33 Light transmission coefficient, KSP 69.0 75-80 80-85

table 2
The content of impurities in the feedstock and in quartz concentrates obtained by the prototype and the proposed method (feedstock with an impurity content of 174.8 × 10 ^-4 %) Name of impurities The content of impurities in the feedstock, 1 × 10 ^-4 % The impurity content in the concentrate obtained by the prototype, 1 × 10 ^-4 % The impurity content in the concentrate obtained by the proposed solution, 1 × 10 ^-4 % one 2 3 four Fe 29.0 0.1 0.05 Al 30,0 0.16 0.08 Sa 19.0 0.10 0,07 TO 22.0 0.5 0.05 Na 30.9 0.7 0.01 Mn 19.0 0.1 0.01 Mg 11.7 0.1 0.01 Ti 11,2 0.3 0.04 Cu 2.0 0.02 0.02 Σ impurities 174.8 2.08 0.34 Light transmission coefficient, KSP 65.0 75.0-78.5 80.0-85.0

Claims (4)

1. The method of enrichment of quartz raw materials, including pre-crushing of the feedstock, decrypting followed by thermal crushing in a liquid medium, final mechanical crushing followed by grinding, magnetic separation, flotation, ultrasonic treatment of the chamber flotation product and its calcination to obtain the final product, characterized in that chamber flotation product after ultrasonic treatment, filtration and drying is subjected to calcination at a temperature of 550-700 ° C, followed by treatment with a mixture of hydrochloric and pla Ikov acid at a temperature not higher than 20 ° C, wherein the flotation is carried out in a pulp having a pH 3.0-4.0. 2. The method according to claim 1, characterized in that the preparation of pulp for flotation is carried out using a mineral acid, for example sulfuric. 3. The method according to claim 1, characterized in that the ultrasonic treatment of the chamber flotation product is carried out at a pH of 3.0-4.0. 4. The method according to claim 1, characterized in that the grinding of raw materials is carried out to a particle size of not more than 0.4 mm

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