RU2182113C1 - Method for processing quartz-containing starting material - Google Patents

Abstract

FIELD: producing quartz for manufacturing quartz glass and optical fiber; chemical, electronic, and other industries. SUBSTANCE: method involves crushing, grinding, electromagnetic separation, rubbing, flotation, and thermal treatment of end product; in the process quartz-containing material of size 60+10 mm is subjected to decryption while being heated to 850-950 C followed by fast cooling down in liquid medium such as water having temperature of 6-20 C; then it is conveyed for grinding and milling to size 0.5+0.1 and subjected to electromagnetic separation; pulp having liquid-to-solid phase ratio of 1.8- 3 : 1 is prepared from nonmagnetic part of separation product and activated water of pH = 4.0-5.5; pulp is rubbed down in acid medium with pH = 4.0-5.5 in two stages with flotation in-between; action energy power at second stage is twice as low as at first stage and pulp temperature at both rubbing stages is maintained at value corresponding to maximal density of pulp for enhancing rubbing process encouraging factors ; after rubbing pulp is washed with water at liquid-to-solid phase ratio of 10 : 1, dehydrated, and calcined at temperature over 800 C. EFFECT: enlarged base of starting material for quartz and optical glass production; environmental friendliness of process. 2 cl, 2 dwg, 1 tbl, 1 ex

Description

 The alleged invention relates to the production of quartz, used in the glass industry for the manufacture of quartz and optical glass, as well as in the chemical, electronic and other industries.

 Currently, the main trend of scientific and technological progress is the creation of the latest technologies and devices of high reliability based on semiconductor technology and fiber optical fibers with low optical loss. In this regard, there is a shortage of conditioned silicon-containing raw materials for use in these industries.

 Therefore, technologies are needed to maximize the quality of raw materials to the needs of today.

 A number of methods are known for producing high-purity silicon dioxide from mineral raw materials.

 So, to the method of chemical treatment of rocks with silica content of 69-75%, which allows to increase its content to 98.0-98.5%, can be attributed to "Method for the production of silicon dioxide" by author. St. USSR 1791383 (С 01 В 33/12) from 06/19/90

In this method, the starting material with a silica content of 69-75% is crushed to a fraction of -0.1 mm and subjected to multi-stage chemical treatment:
- autoclave leaching to obtain liquid glass;
- filtration with the separation of solid sediment from liquid glass;
- magnetic processing of liquid glass;
- heat treatment with simultaneous mixing with calcium oxide and aluminum nitrate;
- filtration under pressure;
- treatment with mineral acids (Hcl, HNO ₃ ) of purified water glass;
- filtration with washing to obtain the final product.

This method allows raw materials with a low SiO ₂ content to be brought to the required condition, but the method is characterized by high technological complexity and low environmental friendliness.

 There are simpler and more environmentally friendly methods of enrichment of raw materials, including, mainly, crushing, grinding and removing impurities by magnetic separation or flotation and magnetic separation. But these methods are applicable, as a rule, to quartz sand with a silica content of at least 95%.

 For example, according to the method according to the Federal Republic of Germany patent PS 2633468 (С 01 В 33/12, 1975), natural silica-containing raw materials (silica sand), crushed to a fraction of -0.5 mm, are subjected to repeated treatment with mineral acid, filtration, washing and drying the precipitate .

The disadvantages of the method are the low purity of the obtained product containing coloring impurities (iron oxides) in an amount of more than 0.001%, and the use of a narrow and scarce range of raw materials - the use of quartz sand with a SiO ₂ content _of at least 95%.

 But the main disadvantage of this method, as well as the previous one, is the high environmental hazard due to the use of mineral acids in the main processes.

 Closest to the proposed method in terms of technical nature and the achieved result is a method for the enrichment of quartz glass sands, carried out at the factory of Ramensky mining and processing plant in Russia (Handbook of ore dressing ("Concentrating plants"), M .: Nedra, 1984, p. 346).

 The technological scheme of the prototype is shown in FIG. 1.

 This factory operates on the basis of the Eganovsky deposit of quartz glass sands and is intended to supply glass factories with high-quality raw materials.

The sands of this deposit are unique both in terms of particle size distribution and chemical-mineralogical, namely:
Grading:
+0.5 mm - from 0 to 5.33%
-O, 5 + 0.1 mm - from 93 to 99.3%
-0.1 mm - from 0.35 to 5.4%
Mineralogical composition:
Quartz - from 99.5 to 99.84%
Clay component - from 0.07 to 1.52%
Feldspars - absent or found as single grains
Chemical composition:
SiO ₂ - 94.84-99.54%
Fe ₂ O ₃ - 0.03-0.57%
Al ₂ O ₃ - 0.22-1.53%
K ₂ O and Na ₂ O - up to 0.35%
MnO ₂ - 0.06%
TiO ₂ - 0.02-0.2%
MgO and CaO - 0.13-1.5%
p.p.p. - 0.08-0.2%
Humidity ranges from 2.5 to 5.5%.

 Naturally, the processing scheme of such sand is simple and the absence of environmentally harmful redistribution. So, fraction sand is directed to the scouring - (1.5-1.8) mm, because deeper opening is irrational due to the high purity of the source sand. The scouring is carried out in a 5% solution of sulfate soap by mechanical or acoustic means. Flotation occurs in a neutral environment without the addition of regulatory reagents; a reagent-collector is a 5% solution of sulfate soap. In the drying section of the factory in pipe dryers or in fluidized bed dryers, sand moisture is reduced to 0.5%.

 The disadvantage of this processing method is the use of a narrow and scarce nomenclature of raw materials, as well as the fact that when sand is enriched with a sufficiently large fraction - (1.5-1.8) mm, a significant part of the impurity films of quartz sand remain unopened, which means that the efficiency decreases purification from impurities.

 The objective of the invention is the expansion of the raw material base for the production of quartz and optical glass while maintaining environmental safety of the processing process.

 The technical result of the implementation of this method of processing quartz-containing raw materials is to obtain a final product of a high degree of purity that meets the needs of modern technologies and devices.

The problem is achieved in that in the method of processing quartz-containing raw materials for the production of quartz glass and fiber optics, including crushing, grinding, electromagnetic separation, scrubbing, flotation and heat treatment of the final product, quartz-containing raw materials with a grain size of -60 + 10 mm are subjected to decrypting with heating to a temperature of 850 -950 ^o C and followed by rapid cooling in a liquid medium with a temperature of 6-20 ^o C, and then fed to the crushing and grinding to a fineness of 0.1 + -0.5 mm, and is subjected to electromagnetic separation, act water is boiled and based on it, the pulp with W: T = 1.8-3: 1 is prepared from the non-magnetic part of the separation product, the pulp is rubbed in an acidic medium with a pH of 4.0-5.5 in two stages, between which flotation is performed, moreover, the energy impact power of the second stage of the rubbing is two times lower than in the first, and the temperature of the pulp at both stages of the rubbing corresponds to its maximum density to enhance the influencing factors of the rubbing process, while the pulp is neutralized with water at W: T = 10: 1 in the process pulp washing, and dehydrated received calcination product was subjected at a temperature above 800 ^o C.

 The technological scheme of processing quartz-containing raw materials by the proposed method is shown in FIG. 2 (this scheme is the most complete, but depending on the feedstock and quality requirements of the consumer, it can be simplified, re-arranged).

 Consider this flow chart from the point of view of its technical nature and distinctive features from the prototype.

1. The fundamental difference between the proposed method and the method according to the prototype is the introduction to the beginning of the scheme for processing quartz-containing raw materials of its heating to a temperature of 850-950 ^o C, which corresponds to the temperature interval for the completion of the decryptation of quartz, followed by cooling it in a liquid medium with a temperature of 6-20 ^o C. In this case, decryptitation is used for preliminary softening and selective disclosure of silica, based on the ability of quartzite to crack when heated, followed by rapid cooling REPRESENTATIONS, because at temperatures above 573 ^o C, α-quartz turns into β-quartz, while the ore volume instantly increases by 0.82%.

 When heated, preliminary softening (cracking) of quartz grains occurs with the separation of impurity films due to the difference in the thermal expansion coefficients of quartz and impurity films. Finally, impurity films are separated from quartz grains during magnetic separation and under the influence of friction between particles during ultrasonic cleaning.

 Practical experience with quartz-containing raw materials shows that the decryptation process is quite complete when processing raw materials with a particle size of -60 + 10 mm.

 2. The prototype method is carried out on quartz sand fractions - (1.5-1.8) mm. The grinding process in this method is not applied. This is due, firstly, to the processing of high purity starting sands. Secondly, it is known that pure quartz-bearing rocks belong to the I category on the scale of prof. M.M. Protodyakonova with a coefficient of strength close to the maximum. Therefore, to implement the grinding process in the prototype, powerful grinding equipment with a special coating is necessary to prevent ore contamination with structural materials (for example, Fe) due to abrasive wear of the working space. Thus, data are known that when grinding quartz raw materials of the III category of strength, the consumption of steel balls is 1.7-2.1 kg / t of ore.

 In the proposed method, the process of purification from impurities is carried out at the optimum size of the raw materials -0.5 + 0.1 mm with a maximum, almost complete opening of the impurities.

 Grinding of raw materials to such an extent on standard equipment was made possible thanks to preliminary softening of quartz (decryptation).

 3. In the proposed method, the crushed raw materials are screened in order to screen out a fraction of -0.1 mm containing the maximum amount of impurities hidden in previous stages. On the other hand, the removal of the dust fraction allows the further use of more efficient dry electromagnetic separation.

The originality (novelty) of the preparation of raw materials at preliminary stages, namely, thermal preparation for the crushing and grinding process with dust screening (fractions -0.1 mm), made it possible to abandon wet separation and switch to a more efficient dry separation, because It is known that wet electromagnetic separation has a number of significant drawbacks:
- the rotation speed of the drums and rolls should be limited to prevent excessive turbulence of the pulp flow in the working area, as a result of which it is possible to partially tear the upset magnetic part of the ore from the surface of the drum;
- in the aquatic environment there is resistance exerted by the medium on the magnetic particles during their movement to the surface of the drum, this especially affects the fine material;
- pulp density significantly reduces the completeness of the deposition of magnetic particles.

 All these disadvantages are absent in dry electromagnetic separation, which allows to remove the magnetic component of the raw material with a maximum degree of completeness with high process productivity.

 4. It is known that the process of ultrasonic scrubbing and subsequent ion flotation are more intense in a mildly acidic environment.

 In the prototype, the processes of scrubbing and flotation are carried out in a neutral environment in order to avoid the introduction of environmentally harmful additives - mineral acids.

 In the inventive method, the authors propose to create an acidic environment in the pulp not by adding mineral acids, but by pre-activating the water used to prepare the pulp.

 There are various methods for regulating the acid-base and redox properties of water and translating it into a dynamically nonequilibrium (activated) state, for example, the method of electrochemical activation according to ed. St. USSR 1679746 (C 02 F 1/46) "Device for electrochemical processing of liquids."

 The authors propose activating water to a pH of 4.0-5.5 by passing it through a special turbine, the principle of operation of which and design features are the subject of know-how.

 5. In the proposed method, based on activated water from the non-magnetic part of the raw material, a pulp is prepared with W: T = 1.8-3: 1, that is, 25-35% solid.

 Practice shows that it is at a given pulp density with a pH of 4.0-5.5 that the process of cleaning impurities during scrubbing and flotation occurs most fully under conditions of a low content of impurities in the pulp.

 Silica enters the ultrasonic etching, characterized by the presence of particles of the useful component coated with films and greases. During ultrasonic treatment, such destructive forces are selected for their removal that the developed stresses (breaking or shear) act only in the surface zone of the pieces. As a result, the films and "cement" are destroyed, and the greases are separated, the particle size of the useful component does not change significantly.

During ultrasonic treatment of pulp by energy exposure, a shock wave is excited in it, thereby causing powerful hydrodynamic disturbances in the pulp in the form of strong compression pulses (shock waves) and hydraulic flows. The magnitude of the amplitude and steepness of the shock wave front, as well as its propagation velocity, depends primarily on the pulp density, the maximum value of which, ceteris paribus, is reached at 4 ^o C. Thus, the rubbing process more efficiently takes place at low temperatures.

 Secondary pulping is carried out after flotation. The energy impact in this case is reduced by half, because the task of the secondary scouring is the removal of flotation reagents remaining on the surface of the quartz after flotation and weakly associated with the useful component.

 The effectiveness of scrubbing in both stages increases under conditions of acidic pulp.

 6. It is known that quartz-containing rocks do not have natural floatability, since during the destruction of such minerals strong bonds are exposed on their surface (ionic, metallic and uncompensated covalent), which leads to their complete wettability by water.

 Therefore, only impurities float from the pulp. Sequential cationic and anionic flotations can almost completely remove impurities from raw materials, while there is a slight saturation of ion collectors due to the small amount of impurities that have reached the flotation. Therefore, ion collectors, in principle, can be returned to flotation and operate in a closed cycle until they are saturated.

 Flotation according to the prototype is carried out in a neutral environment, and in the claimed method, the authors propose to carry out it in an acidic environment, since it is known that pure quartz absorbs fatty acids from solutions and although the strength of this collector is fixed on the surface of the mineral is small and flotation is absent in this case, This is not desirable due to clogging of the finished product. To deactivate the surface of quartz, the authors recommend a weakly acidic pulp.

 7. In the proposed method, after the secondary grinding of the pulp with a pH of 4.0-5.5, the authors propose an original solution - neutralizing the pulp with water during the elutriation (washing) of the pulp.

 When providing W: T = 10: 1 due to the introduction of fresh water into the pulp, the pulp is completely neutralized. Thus, the wastewater of the proposed method is absolutely environmentally friendly and does not carry any harmful substances.

 8. According to the prototype, the finished product is dried in pipe dryers and fluidized bed dryers. The humidity of the finished product reaches 0.5% - this is usually crystallization moisture, which significantly narrows the scope of this product, for example, in fiber optics.

In the inventive method, the authors propose, after drying, to direct the finished product to high-temperature calcination, which guarantees obtaining quartz of maximum purity (up to 99.999% in SiO ₂ ).

 However, a comparison of the proposed method with similar solutions in this area revealed a number of similar features.

 1. The decryptation process is widely used in various technologies, for example, in the production of carbon-containing materials: German patent 1170365 (class 10a 33/02, 1964); Zhitov B.N. and others. "Coking of thermally prepared coals" M .: Metallurgy, 1970, p. 86-94. In this production, the softening process is used to increase the efficiency of the crushing and grinding department. In the inventive method, the ultimate goal of decryptation is the maximum (almost complete) separation of impurities, and the impurities are separated sequentially at each redistribution: in the crushing and grinding compartment with a fraction of -0.1 mm, in the form of magnetic separation tails, with a foam flotation product, when the pulp is unwound . That is, in the inventive method for processing quartz-containing raw materials, softening (decryptation) is a preparation for opening and separating impurities.

 2. It is known that enrichment processes (scrubbing, flotation) occur more efficiently in an acidic environment.

 Traditionally, the pulp is acidified with mineral acids (ed. St. 1545484, C 01 B 33/12 “Method for producing a highly dispersed silica filler”), which leads to the formation of a large amount of effluents containing toxic compounds. The authors acidify the pulp by activating the water when it is treated with a special turbine, and neutralize the pulp so acidified in this way during its elutriation by adding fresh water in the ratio W: T = 10: 1.

3. High-temperature processing of enriched silica is known from a number of technical sources, for example auth. USSR 1085187 (C 01 B 33/12) "Method for drying synthetic silicon dioxide", which allows you to get rid of physically sorbed molecular water and its associates. Heat treatment in this method is characterized by high energy and labor intensity with stepwise heating of the material, which is not very suitable under production conditions. In the proposed method, the dried material is subjected to high-temperature processing in a continuous mode, for example in tubular rotary kilns, at a temperature of more than 800 ^o C.

 A new set of signs of both known and unknown (claimed) in their close relationship allows us to obtain a technical result of a higher level, namely, to obtain silica suitable for the manufacture of quartz products with high heat-resistance, crystallization stability, and optical characteristics in terms of the amount of impurities and dissolved gases. homogeneity, as well as reflection coefficient and light fastness.

 The proposed technology for processing quartz-containing raw materials was tested at the Saransk concentrator, where pilot tests were conducted.

 Example.

The feedstock was crushed to a particle size of -60 mm and the -60 + 10 mm fraction was heated at 850 ^° C for 3 minutes, and then abruptly cooled in water at a temperature of 6 ^° C. The decrypted material was subjected to mechanical crushing on jaw and roller crushers and grinding in a mill with subsequent sieving to obtain a working grain size of -0.5 + 0.1 mm

 The working grain was subjected to successively weak and strong magnetic separation at a magnetic field of each operation, respectively 0.2 T and 1.7 T.

 For subsequent enrichment operations (scrubbing and flotation), a pulp was prepared with a ratio of Ж: Т = 3: 1 from a non-magnetic fraction of working grains and water with a pH of 4.0-5.5, and water was activated using a water pump equipped with a special turbine and mining equipment manufactured by the Ufa plant (electric pump unit with a special turbine P-12.5 / 12.5-SP).

 The resulting pulp was subjected to ultrasonic treatment for 30 s with processing parameters (frequency, power) selected by the authors for each specific raw material taking into account the temperature of preliminary decrypting. The optimal parameters of ultrasonic treatment are selected based on the task of maximum removal from the surface of the grains of hydroxides of heavy metals and slurry coatings.

 The authors consider the absolute values of the ultrasonic processing parameters to be inappropriate from the point of view of preserving the technological features of the proposed technology.

 After sonication, the pulp was treated with ANP-14 cation collectors at a flow rate of 250 g per 1 ton of pulp. The treatment of the pulp was carried out for 3 min at a pH of 4.0-5.5.

 The cationic flotation chamber product was subjected to treatment with an anion collector - tall oil (DTM) for 15 min at a flow rate of 300 g per 1 ton of pulp. As a result, polyvalent metal minerals, including aluminosilicate impurities, were removed.

 The anionic flotation chamber product was subjected to a second stage of ultrasonic treatment at a lower intensity to remove reagents from the previous enrichment stages from the surface of quartz particles.

 After this, the operation of elutriation was performed, that is, the pulp was thickened, and after thickening, pure deionized water was added to it in the ratio W: T = 10: 1.

After this, the pulp was again thickened, filtered and dried at a temperature of 300-400 ^o C.

The dried quartz was subjected to "thermal shock", that is, a sharp heating at a temperature of 900 ^o With the aim of opening gas-liquid inclusions.

As a result of this treatment, the content of impurities in the feedstock decreased to the values shown in the table, and a quartz concentrate with a SiO ₂ content _of 99.999% was obtained.

The authors set the following tasks:
- firstly, to confirm in industrial conditions the possibility of obtaining silica with a content of SiO ₂ not less than 99.9%;
- secondly, taking into account the rather high saturation of the technological scheme with various redistributions, it can be experimentally proved with minimal costs that the decryptation process, the implementation of the decryptation process at the beginning of the technological scheme, the implementation of pulp flotation based on activated water, and high-temperature concentrate calcination are crucial.

 For comparison, two samples of feedstock of 150 kg each were prepared.

The first test scheme differed from the second in the above three characteristics, namely:
- according to the first processing scheme, raw materials were tested without preliminary high-temperature processing, but of the same size (-0.5 + 0.1 mm);
- the flotation process was carried out in an acidic environment (pH 2-4) using mineral acids;
- at the end of the technological scheme there was no high-temperature processing.

Some technical indicators of the second test scheme corresponding to the proposed technology are given below:
- the temperature of decryptation 950 ^o C,
- cooling after decrypting with technical water with a temperature of 12 ^o C,
- the size of the working fraction of the raw material (-0.5 + 0.1) mm,
- dry magnetic separation with induction of 1.7 T,
- preparation of slightly acidic pulp with a pH of 4.0-5.5 based on activated water with W: T = (1.8-3): 1,
- elutriation of pulp in industrial water W: T = 10: 1,
- drying of the concentrate at a temperature of 300 ^o C,
- calcination at a temperature of 1320 ^o C.

 The test results for the first and second schemes are shown in the table.

From the above data, it can be concluded that the application of the proposed technology allows to obtain a quartz concentrate with a SiO ₂ content _of 99.999%, and further development and industrial improvement of this scheme will improve this indicator.

Claims (2)

1. A method of processing quartz-containing raw materials for the production of, for example, quartz glass and fiber optics, including crushing, grinding, electromagnetic separation, scrubbing, flotation and heat treatment of the final product, characterized in that the quartz-containing raw materials with a particle size of -60 + 10 mm are subjected to decryptation when heated to temperature of 850-950 ^o C, followed by rapid cooling in a liquid medium with a temperature of 6-20 ^o C, and then fed to the crushing and grinding to a fineness of 0.1 + -0.5 mm, and is subjected to electromagnetic separation of more muggles of the total part of the separation product and activated water with a pH of 4.0-5.5, a pulp is prepared with W: T = 1.8-3: 1, the pulp is subjected to grinding in a medium with a pH of 4.0-5.5 in two stages, between which carry out flotation, while the power of the energy impact in the second stage of the scrubbing is maintained two times lower than in the first, and the temperature in both stages is maintained at the corresponding maximum pulp density to enhance the influential factors of the scrubbing process, after scrubbing the pulp is washed with water at W: T = 10: 1, dehydrated and calcined at temperature e 800 ^o C.  2. The method according to p. 1, characterized in that as a liquid medium with rapid cooling of the raw materials use water.

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