DD287245A5 - METHOD FOR OBTAINING HIGH-PURITY FINE-CORK DUST-FREE QUARTZ SAND - Google Patents

Abstract

The invention relates to a method for obtaining high-purity feinkoerniger dust-free quartz sands, which are used in the glass industry as a raw material for the production of high-quality glasses. The process for obtaining high-purity fine-grained dust-free quartz sands from pretreated quartz sand by attrition, de-smelting and possibly flotation is characterized in that the pre-cleaned quartz sand is classified and the average grain fraction is partially dissolved in alkali hydroxide solutions under hydrothermal conditions or under normal pressure at elevated temperature and the leaching residue is multistage with water attritioned and de-aerated, washed and thickened, then gently milled, classified and thickened and subsequently subjected to treatment with mineral acid, followed by acid washing of the leaching residue and dewatering, with density sorting being carried out before or after the alkaline treatment. Method; Quartz sands, high purity; Foreign mineral separation; Removal of pollutants from an additional layer; Pre-cleaning, mechanical; Treatment, chemical; NaOH solution; Hydrothermal conditions; Normal pressure; Temperature, increases; grinding}

Description

Field of application of the invention

The invention relates to a method for obtaining high-purity fine-grained dust-free quartz sands, which are used in the glass industry to produce high-quality glasses.

Characterization of the known technical solutions In the processing technology it is known that in quartz sands the pollutants are present in substantially three forms, namely

bound to foreign minerals (ie non-quartz), as coatings on the quartz grains and enclosed in grains of quartz itself.

To separate the foreign minerals are methods of mechanical treatment, such as magnetic separation, density sorting

and flotation, used (Schubert, H .: preparation of solid mineral raw materials, Leipzig 1977;

Quarzrohstoffe, Leipzig 1977). The use of several of these sorting method successively is not common in general, since the

the quality of the sorting stage is so low that the expenses for this stage can not be compensated by higher revenues for the commercially available quartz sand varieties.

The coatings on quartz grains contain the pollutants in the form of oxides and hydroxides, in some cases also

bound to organic substances. Often the quartz grains also have clay coatings.

To separate these coatings, attrition techniques have long been used in conjunction with classifying processes. dbm Cleaning success of the Attritionverfahren, which is based on a mechanical stress of the coatings by rubbing the Quartz grains are based on each other, but limits are set because the quartz grains have a rough surface, so cracks, Have cracks and other depressions. The pollutants stored in these depressions can be released

do not remove it by mechanical means. For their partial separation, the use of mineral acids or basic

Active ingredients (Schulz, G .: Preprints International Conference FIA Freiberg 1984) in conjunction with a mechanical Treatment be useful. Good results have also been achieved when the pollutants are transferred to the gaseous hare, such as

for example, when using the thermochlorination (Müller, S .: Chemical Technology, Leipzig 32.1980.5).

Finally, attempts have also been made by hydrothermal treatment under the action of mineral acids or bases Diffuse pollutants from quartz grains (U.S. Patent 3,932,777; Sorg, A .: Sprechsaal, Vol. 116, 7, 1983). However, this was not about the removal of the outer layer of quartz grains, including those contained in it Pollutants, but to the diffusion of mobilized pollutants through this layer. Other attempts at resolution assume not only the pollutants from the recesses of the outer layer, but the

to remove pollutant-rich layer itself. That was tried with a mechanical stress, which to a

Abrasion or flaking of the outer layer, but should not lead to a crushing of the quartz grains. The problem

It consisted of removing the outer layer evenly. That should be through the electro-hydraulic effect or through

Ultrasound can be achieved, which cause a cavitation, from which one can see the chipping of pieces from the outer Layer of quartz grain hoped. With the above procedures, the pollutants contained in the core of quartz quartz grain were not detected. Attempts by crushing the quartz grain accessible to the pollutants contained in the core of a mineral acid treatment

did not produce sufficient results. In the previous procedure, the separation of the outer layer was not or only partially. Thus, the comminution before the mineral acid treatment and the high-pollutant outer layer was crushed with. The triggering of the pollutants from the fragments of the outer layer was very imperfect, so that even with very fine grinding no high-purity quartz products were reached (Schulz u.a., Silikattechnik 25.1974,2).

The disadvantage of the known technical solutions is that when using methods with strong emphasis

mechanical forces failed to make them act so targeted on the quartz grain, that the outer layer was removed evenly. The application of methods using chemical agents is based on a release of the pollutants in the wells of the quartz surface, with the use of diffusion methods also on the removal of pollutants from the outer layer, but in any case not known, but on the targeted removal of the outer layer of the

Quartz grains, which is to be regarded as a carrier of a large part of the pollutants. Another disadvantage is that in the efforts to detect the pollutants contained in the core of the quartz grain, in

the process sequence separation of the outer layer / grinding / treatment in mineral acid of the former process was not consistently completed, as a result, the overall cleaning effect was low.

Another disadvantage is that not all with technical before the attempted removal of the pollutant-rich outer layer Means detectable foreign minerals were separated. In the case of previous flotation, this mainly concerns the rough ones Foreign minerals of higher density. Thus, according to the state of the art, no products of such high quality are obtained from quartz sands that are suitable for the Production of high-quality glasses is sufficient. Object of the invention

The aim of the invention is to develop a process for obtaining high-purity fine-grained dust-free quartz sands, from which high-quality glasses can be produced.

Explanation of the essence of the invention The invention has for its object to provide a method for obtaining high-purity fine-grained dust-free quartz sands

with which they are bound in quartz sands to foreign minerals and in the outer layer of the quartz grains themselves

Pollutants are removed by mechanical and chemical treatment processes to the extent that the resulting product

a quality sufficient for the production of very high quality glasses.

According to the invention, this object is achieved in that pre-purified quartz sand is classified by attrition, desludging and optionally flotation and the average grain fraction is partially dissolved in alkali hydroxide solutions under hydrothermal conditions or under normal pressure at elevated temperature and ddt leach residue is attritioned in several stages with water and deslimed, washed and thickened, thereafter gently milled, classified and thickened and subsequently subjected to treatment with mineral acid, which is an acid-free washing of the leaching residue and a

Connect drainage, whereby a density sorting takes place before or after the alkaline treatment. Essential to the invention is that from the quartz sand, a mean grain fraction preferably the bandwidth 0.2 to 0.3 mm Sieve classification is obtained, wherein a middle quartz fraction is obtained. It is further essential to the invention that the remaining quartz fraction either at normal pressure in a Alkalihydroxidlösung,

preferably sodium hydroxide solution, a concentration of 30 to 50% at temperatures up to boiling temperature or hydrothermally in a stirrer in alkali metal hydroxide solutions, preferably sodium hydroxide, with concentrations of 2 to 50%, preferably of 10%, at temperatures from boiling to 250%.

It is also essential to the invention that the leaching residues are attritioned with water in several stages and are dewatered and dewatered

pH <11, preferably using jet apparatuses in conjunction with towering classifiers and thickening the washed leach residue in a screw classifier.

It is essential to the invention that the moist leaching residue is milled gently, preferably one Ball mill with discharge chamber is used, and then classified the gently milled leaching residue

and thickened, preferably using a screw classifier and a grain sheath of 50 microns respected

It is also essential to the invention that the moist leaching residue is treated in a reactor with sulfuric acid, wherein

the concentration of mineral acid is 1 to 20%, preferably 3%, and in mineral acid treatment

Temperature from room temperature to 100 ⁰ C, preferably of 80 ° C, is maintained. It is furthermore essential to the invention to carry out the density sorting preferably with preparation stoves. With the orfordungsgemäßen method, the foreign minerals and in several mechanical treatment stages

virtually completely removed pollutant-rich grain fractions of pre-cleaned quartz sand and the quartz fraction subjected to several chemical treatment stages, the outer layer of quartz grains having high pollutant contents is removed and the freed from the outer high-pollutant layer quartz grains remain as a final product of high purity. The gentle grinding between the basic and the mineral acid treatment provides a digestion of the soluble pollutants contained in the interior of the quartz grain, which are thus a mineral acid treatment accessible.

The succession of several classification and Entschlämmprozesse ensures the separation of even a gentle Treatment resulting fine grain and thus the recovery of a fine-grained dust-free quartz sand. The invention will be explained in more detail with reference to an embodiment. Ausführungsbeispiei

An attrited, degummed and floated quartz sand of grain size 0.1 to 0.4 mm with 80 ppm Fe ₂ O ₃ was classified at wire cuts of 0.3 and 0.2 mm. The accumulating 0.2 to 0.3 mm fraction intended for further processing had Fe ₂ O ₃ contents of 70 to 75 ppm. The grain fraction 0.2 to 0.3 mm was sorted on a preparation hearth according to the separation factor density. Heavy mineral concentrates with> 300 ppm Fe ₂ O ₁ and quartz products with 50 to 60 ppm Fe ₂ O _{3 were} obtained. In the heavy mineral concentrates in particular coarse heavy minerals were found that had not been discharged in the upstream flotation process. The quartz products were treated either under hydrothermal conditions or under normal pressure at elevated temperature with NaOH solution

 The aim of this treatment was the dissolution of 15 to 20% of the quartz

 This was achieved under the following conditions:

Hydrothermal Treatment 1: 1 Solid / liquid ratio (mass) 10% NaOH concentration 16O ⁰ C temperature 1h hold time nevollstänc Under these conditions, ei Treatment under normal pressure 1: 1 Solid / liquid ratio 40% NaOH concentration 125 ^° C temperature 4h hold time

Under these conditions, the residual concentration of free sodium hydroxide was still 23%. The partially dissolved quartz sands were washed with water to a pH of <11. In the washed Laugor residues of both the hydrothermal treatment and the normal pressure treatment were 45 to 50 ppm Analyzed Fe ₂ O ₃ . The quartz sand treated in the basic medium was, after washing with water, wet ash with a water content

from 20% ago.

Bieser wet sand was milled gently in a column ball mill with iron balls. The upper grain size was reduced from about 300 μm to about 150 μm (passage 95%). 30% of the ground sand was in the grain area υδΟμπι ago.

The ground water suspended millbase was decanted in several stages, with a particle size of 50μιη was maintained. By decantation over 90% of the fraction <50μιη were separated in the fines. This wet sand was heated in a tubular reactor at 80 to 90 ⁰ C and treated with preheated 48% sulfuric acid. The addition of the sulfuric acid was carried out in such an amount that with the liquid contained in the wet sands a Concentration of 3% sulfuric acid adjusted. The mean residence time of the sand in the tubular reactor was 1 h. After treatment with mineral acid, the sand became

Washed out with water in several stages, with very high purity water being used in the last wash stages. The product thus obtained had a Fe ₂ O ₃ content of 15 to 25 ppm. It was completely free of micro-grain <50 pm.

Overall, the method described led to the following gradual decrease of the FejOj content in the quartz sand:

Mass output /% / Fe ₂ Oj-GOhIiT / ppm / FlotierterSand 100 80 Grain fraction 0.2 to 0.3 mm 80 70 to 75 Quartz product density sorting 72 55 to 65 Residue NaOH treatment 60 45 to 50 after washing Ground product after decantation 49 2,000 to 2,500 Ground product after mineral acid 48 15 to 25 Treatment and decantation

The advantage of the method is that with him virtually all foreign minerals and high-polluted grain fractions

are separated, which were not detected in the Vorreinigungsstufen, including those that are not vulnerable by the chemical agents used. The achievable qualities according to the method described depend crucially on the result of the density sorting, but also on the correct choice of Klassierschnitte.

The mean grain fraction is controlled by drug concentration, temperature, pressure and hold time Dissolving process subjected to a partial dissolution of the quartz grain by uniform degradation of the outer layer

causes.

This dissolution process can be controlled with an accuracy of a few micrometers surface removal. That means one

decisive advantage over all previously used mechanical and chemical types of stress for

Removing the high-pollutant outer layer. Another advantage is the leaching in mineral acid. Midt of this, such pollutants are removed, although by the Dissolve the outer layer are released, but do not go in the basic medium in solution and not through Washing process, even under strong mechanical stress, of the after the partial solution of the quartz grain

present new surfaces can be removed.

A particular advantage of the method is that the digestion of the quartz grain by grinding only after removal of the

high-pollutant outer layer takes place, whereby for the first time products of very high purity can be produced from quartz sand.

Claims (10)

1. A process for obtaining high-purity fine-grained dust-free quartz sands from pretreated quartz sand by attrition, de-slurry and optionally flotation, characterized in that the pre-cleaned quartz sand classified and the average grain fraction in alkali hydroxide under hydrothermal conditions or under normal pressure at elevated temperature is partially dissolved and the leach residue with several levels Water is attritiert and dehumidified, washed and thickened, then gently milled, classified and thickened and then subjected to a treatment with mineral acid, followed by acid leaching of the leaching residue and drainage, with a density sorting before or after the alkaline treatment. 2. The method according to claim 1, characterized in that from the pre-cleaned quartz sand a mean grain fraction preferably of the band width 0.2 to 0.3 mm is obtained by Siebklassierung. 3. The method according to claim 1, characterized in that the remaining prepurified quartz fraction is treated at atmospheric pressure with an alkali metal hydroxide solution, preferably sodium hydroxide solution, a concentration of 30 to 50% at temperatures up to boiling temperature. 4. The method according to claim 1, characterized in that the quartz fraction hydrothermally in a stirring machine in alkali metal hydroxide solutions, preferably sodium hydroxide, with concentrations of 2 to 50%, preferably of 10%, at temperatures of boiling to 250 ⁰ C been treated. 5. The method according to claim 1, characterized in that the resulting leaching residues are attritioned in several stages with water and desludged and washed to a pH of <11, preferably jet apparatuses and upflow classifiers are used. 6. The method according to claim 1, characterized in that are used to thicken the washed leaching residue screw classifiers. 7. The method according to claim 1, characterized in that the moist leaching residue is gently milled, wherein preferably a ball mill is used with discharge chamber. 8. The method according to claim 1, characterized in that the gently milled leaching residue is classified and thickened, wherein preferably a screw classifier used and a corneal sheath of 50pm is maintained. 9. The method according to claim 1, characterized in that the moist leaching residue in a reactor with sulfuric acid at a concentration of 1 to 20%, preferably of 3%, at a temperature of room temperature to 100 ⁰ C, preferably from 8O ⁰ C, is treated. 10. The method according to claim 1, characterized in that the density sorting is preferably carried out on treatment herds.