DD240147A1 - METHOD FOR THE COMPLEX AND PARTIAL PREPARATION OF QUARTZ SANDS - Google Patents

Abstract

The invention relates to a process for the effective and environmentally friendly treatment of quartz sands having SiO 2 contents of 97% occurring in natural reservoirs, huminities corresponding to absorbance values of 2.0, glow losses of 1%, Fe 2 O 3 contents of 0.5% and grain slivers of 90% between 0.1 -1 mm edge length used as glass, foundry and special sands. According to the invention, the u. a. It solves the fact that limed potable water is used in the circulation for the formation of quartz sand, the wet classification in underwater rotary screens and the hydraulic conveyance in special attrition water jet conveyors, the residual moisture is lowered into large-space filter basins equipped with vacuum pumps and the drying is carried out by incorporation of expansion chambers and fluidized bed separators. The dry sand is transported with special conveyor screws and classified on pushovers.

Description

For this 3 pages drawings

Field of application of the invention

The invention relates to a method for producing high-purity quartz sands from natural deposits with the greatest possible reduction of pollutants for use as glass, foundry and special sands.

Characteristic of the known technical solutions

The treatment of quartz sands is currently carried out using wet chemical methods, for example according to DD-PS 148305, by technological ranking of treatment steps such as classifying, slurrying, Attritieren, floating and application of gravity or centrifugal pumping and also by drying, screening and magnetic separation.

Due to the high hardness of quartz sand (Mohs hardness 7) and the resulting abrasive properties, gravitational clouding is mainly used because there are no suitable materials for economically viable pumping. The constructional consequence of such treatment plants are complex tower superstructures made of steel or reinforced concrete.

The wet classification is operated with stream classifying or with drum, arc or mechanically excited sieves with spray or rinse. It is usually used untreated water of the waters in mostly open water circuits.

The attrition is carried out in tube mills with or without grinding media, or attrition cells are used.

The desludging takes place in screw or spiral classifiers.

The final drainage is carried out exclusively by gravity up to the soil moisture.

The usually without energy recovery drying processes burden the environment due to the insufficient effect and reliability of Entstaubungsaggregate (eg cyclones, tissue or electrostatic precipitator) considerably.

The dry classification is carried out only on particle sizes> 0.5 mm on mechanically excited sieves. Alternatively operated air sifter systems work very smoothly.

Object of the invention

The aim is to create a process for the production of bulk and special sands by processing highly fluctuating, naturally occurring quartz sands, whereby the treatment enables savings in investment, energy and labor compared to the conventional methods and reduces the environmental impact.

Explanation of the essence of the invention

The invention is based on the object, an effective and environmentally friendly process for the complex and partial production of silica sand products as far as possible reduction of pollutants by treatment of highly qualitative fluctuating, occurring in natural deposits quartz sands with SiCVGehalten of> 97%, humin contents according to extinction values of <2 , 0, annealing losses of <1%, Fe ₂ O ₃ contents of <0.5% and grain bands of 90% between 0.1-1 mm edge length to create.

According to the invention the object is achieved in that the naturally occurring quartz sands are processed by replacing and reducing ineffective, conventional process steps as well as by coupling and complex interaction of newly developed techniques that

- In a mixed water the quartz sand turbidity with limed hot water, which is in a closed circuit, with pH values of 10 to 11 and Fe (OH) ₃ content of <100mg / l is carried out, the maintenance of pH and Fe (OH) ₃ content is ensured by an automatic control system via a constant dosage of quicklime with simultaneous addition of air and continuous removal of the resulting gypsum and Eisenhydroxidschlammes,

- In low-wear underwater rotary screens with mesh widths of 0.35 to 5.0 mm and an axial pitch of 1:60, the wet classification takes place,

- in attrition-water-jet conveyors with downstream flow-through slurry in tips, the hydraulic conveyance of the quartz-sand turbines takes place, the intensive attrition being achieved by the generated cavitation and the hydraulic conveying speeds being between 1-2 m / s,

- in vacuum-equipped, open large-capacity filter tanks, the lowering of the residual moisture of the wet-processed quartz sand to values of soil moisture and below of <7%,

- in automatic flotation plants, the greatest possible reduction of pollutants (eg heavy minerals) takes place,

- In automatic systems with hot gas generators, spin dryers and downstream

"Drying chamber, the flue gas temperatures <100 ⁰ C and connect to the desulfurization and dedusting of the flue gas vortex precipitator, coupled with heat pumps,

- the pumping of the dry quartz sand takes place in closed special vacuum screw conveyors with external shaft bearings, the special screw conveyors operating with or without water cooling and the relative speeds between the quartz sand and the screw blade being <0.3 m / s,

- In Stößeischwingsieben with mesh sizes between 0.1 to 1 mm, the dry classification takes place and magnetic secondary contaminants are removed with subsequent magnetic separators.

With the method according to the invention, quartz sands which vary greatly in terms of quality and which occur in natural deposits can be treated effectively and inexpensively, or their preparation in the required qualities and quantities is made possible in the first place. The process is associated with lower environmental impact.

embodiment

With reference to the flow diagrams shown in FIGS. 1, 2 and 3, the complex and partial preparation of a quartz sand obtained relatively dry in a natural deposit with different pollutants in terms of absolute amount and type of binding such as sulphidic, oxidic and siliceous heavy minerals, humins and clays Production of quartz sand for various applications will be explained in more detail.

Fig. 1 represents the mechanical preparation, Fig. 2, the flotation treatment and Fig. 3, the dry mechanical treatment.

During reprocessing, the key characteristics and essential quality parameters (content of SiO ₂ , Fe ₂ O ₃ , Al ₂ O ₃ , slurries, humins and loss on ignition) are determined analytically as the main characteristic values and are listed in Tables 1-4. The letters A to Q in FIGS. 1 to 3 identify the sampling points or the quartz sand products, and in Tables 1-4 the associated analytical results.

The soil-wet raw sand (including Fe ₂ O ₃ contents from 200ppm to 2000ppm) is conveyed continuously with the bucket wheel excavator 1 type SR 130 via the belt conveyor 2 with a capacity of 400t / h in the Rohsandtagesbunker3 with a capacity of 1 000t. With a throughput of 50 t / h raw sand, the processing plant is continuously supplied with raw sand via bunker emptying trolley 4 and belt conveyor 5 via remote control.

The raw sand is first screened in a Kreiswuchtschwingsieb 6 with a mesh size of 10 mm, the components> 10 mm are driven to the dump 7. The incoming mass loss is about 1% (sampling point A).

About a belt conveyor 8, the raw sand is fed to the mixed flux 9, which is added to the turbidity of the raw sand with a quantity of 100m ³ / h gekalktem hot water, which is in a closed circuit. An automatically operating pH-value control system ensures that the pH is between 10 and 11 and the Fe (OH) ₃ content is <100 mg / l by the addition of quick lime and simultaneous addition of air. The settling gypsum and Eisenhydroxidschlamm is continuously discharged.

With this process step, the electrochemical corrosion of the water-wetted iron parts in the wet processing is mitigated and noticeable treatment effects are achieved with regard to the reduction of the humus content in the raw sand.

The quartz sand slurry passes from the mixing washer 9 in the underwater rotary screen 10 with a mesh size of 3 mm for the separation of coarse components (> 3 mm), which are driven onto the heap 7. The mass loss is <0.5% (sampling point B). The underwater rotary screen 10 has an axle pitch of 1:60 and is characterized by the absolute underwater operation of the screening and the use of Siebbeschegungen of plastic by its low wear, thus resulting in savings in operating costs. The quartz sand slurry is then hydraulically conveyed by the attrition water jet conveyor 11 in the downstream Entschlämmungsspitze 12, while the pollutant-rich grain fraction of <0.1 mm is greatly reduced, which is fed to the clarifier 13. The conveying speed is between 1-2 m / s.

The intensive attrition is achieved in the specially developed attrition water jet conveyors by deliberately generated cavitation. The advantages of this solution are the high processing effects, the low operating costs due to cheap, commercially available and easily replaceable wear parts, high operational reliability and low investment costs. This solution eliminates the need for complex tower towers made of steel or reinforced concrete in processing plants (for example, in flotation plants) by using building lines.

The quartz sand slurry (grain fraction 0.1-3 mm) is fed to the underwater rotary screen 14 with a mesh size of 0.8 mm, the screen residue with a grain fraction of 0.8-3 mm is obtained as a filter stand or construction gravel (sampling point C).

The quartz sand slurry (sampling point D) with a grain fraction of 0.1-0.8 mm is conveyed with the attrition water jet conveyor 15 in the downstream Entschlämmungsspitze 16, wherein the pollutant-rich grain fraction of <0.1 mm is fed to the clarifier 13.

The quartz sand slurry (sampling point E) is rinsed by the attrition water jet conveyor 17 into eight large-capacity filter basins 18 with a capacity of 150 t each for dewatering.

After a dehydration time of 10 hours with gravity drainage or after 5 hours with the use of vacuum pumps is a drip-free quartz sand with a water content of 4-6% before (sampling point F), by means of automatically operating emptying device 19 with a capacity of 100t / h either as a finished product (Quartz sand, moist) reaches the silo and loading plant 20 or further processing (see Fig. 2 and Fig. 3) is supplied.

The advantage of the large-capacity filter basins is in the subsequent treatment for dried quartz sand in the considerable saving of energy for the drying process or when using the drainage under vacuum that when using the processed quartz sand in humid conditions, the construction costs for the large-capacity filter basins by approx.

50% can be reduced.

About the emptying device 19, the belt conveyor 21, the metering device 22 and the Attritionswasserstrahlförderer 23 with a capacity of 20t / h (sampling point G) passes the quartz sand or silica sand slurry in the Flotationsaufbereitung (Figure 2).

First, the unflotable grain fraction of> 0.35 mm with the underwater rotary screen 24 (0.35 mm mesh size) separated and conveyed as a coarse grain fraction through the attrition water jet conveyor 25 in the large-capacity filter tank 26, subjected to a drying process (sampling point I), by means of automatically operating emptying device 27 of SiIo and loading system 20 fed or refined in the dry mechanical treatment (Fig. 3).

The underflow fraction is conveyed through the attrition water jet conveyor 28 in the downstream Entschlämmungsspitze 29, wherein the grain fraction of <0.1 mm is fed to the clarifier 13.

For stable turbidity, the quartz sand slurry (sampling point H) is thickened with the screw classifier 30 for the purpose of stable turbidity formation. The grain fraction of <0.1 mm and water are the clarifier 13 and the Quarzsandtrübe (sampling point J) and a defined amount of fresh water 'the flotation 31 supplied.

The quartz sand slurry, which is isolated from heavy minerals, passes through the atmospheric water jet conveyor 32 for dewatering into the large-capacity filter basin 33 (sampling point L) and via the emptying device 34 to the silo and loading plant 20 or into the dry-mechanical preparation (FIG. 3).

With the application of the techniques already described (underwater screening, Attritionsförderung with Entschlämmungsspitze and drying in large-capacity filter basins) the flotation for the production of high-purity quartz sands mitweitestgehem reduction of pollutants is optimized or made possible in the first place. It is also possible to bypass the flotation apparatus 31 via the attrition water-jet conveyor 35 and to feed the quartz sand slurry for drying to the large-capacity filter basin 36 (sampling point K). The quartz sand product can be supplied via the emptying device 37 of the SiIo and loading system 20 or further refined in the dry mechanical preparation (FIG. 3).

The raw sand (sampling point A) or the quartz sand products corresponding to the sampling points F, I, K and L after the basic mechanical preparation and flotation preparation are then further refined in the separate dry-mechanical preparation (FIG. 3).

About the emptying devices 19, 27, 34 or 37, the corresponding quartz sand product via the belt conveyor 38 with a capacity of 100t / h or the raw sand with the belt conveyor 8 the metering device 39 with an output of 45t / h automatically fed to the drying process. The metering device 39 ensures a continuous quartz sand task as a function of the dryer outlet temperature of the flue gas. The dry mechanical treatment of the quartz sand product F is considered below.

The quartz sand entering the spin dryer 40 (type ASS, SKET Magdeburg) is dried to 0% moisture within about 20 minutes. City gas, which is heated in the hot gas generator 41 to 600 ^c C serves as an energy carrier. The consumption is about 20 m ³ idN / t sand. The dryer air outlet temperature of 80-100 ⁰ C, which corresponds to the sand outlet temperature, is ensured by the wet sand dosing. The quartz sand (sampling point M) with a temperature of 80-100 ⁰ C is in closed, working with vacuum and water-cooled special screw conveyors 42 with outboard shaft bearings and a relative speed between the quartz sand and the screw flights of <0.3 m / s to the silo and loading system 20 promoted. These special screw conveyors are characterized by low wear, long service life and low dedusting effort.

-4- ^ fU It /

The spin drying drier 40 is followed by the discharge chamber 43, the quartz sand (sampling point N) which separates out is fed via the special screw conveyors 44 to the silo and loading plant 20 or can also be used, for example, to mix the finished product M. Since with the flue gas stream about 20% of the dried quartz sand amount is constantly discharged, the expansion chamber 43 ensures a problem-free increase of the yield up to 93% of the faulty, it is characterized by high durability and reliability. After the expansion chamber 43 of 80-100 ⁰ C hot flue gas stream passes to the dedusting and desulfurization in the Wirbelnaßabscheider 45. Here, the dust content of about 40g / m ³ to 500 mg / m ³ and a lowered desulfurization of 50% at a pH Value of 10 of the inlet water reached. A portion of the heat energy of the flue gas is removed to the continuously flowing inlet water of the fluidized bed cutter 45 (about 4.2 x 10 ⁶ kJ / h) and the flue gas temperature is lowered to 40-50 ° C. The proportions <0.1 mm are fed to the heap 7.

The water in the fluidized bed separator 45 heats up from about 10 ° C to 22 ⁰ C and serves as a refrigerant flow in a downstream heat pump 46 type KWS 560, where a heat transfer (heating water) generated and the heating system 47 is supplied. The heat pump 46 is automatically controlled in response to the settable temperature of the brine stream. In this way, about 30% of the drying input energy can be recovered.

For the production of further special quartz sands, a sharp dry sand classification takes place in the form that the quartz sand with the special screw conveyors 42 of the ram vibrating sifter 48 with mesh sizes of 0.2; 0.25; 0.315; 0.4 and 0.5 mm is supplied. The quartz sand of the underflow is transported to the silo and loading plant 20 with the special screw conveyor 49 and via the magnetic separator 50 (sampling parts 0) and the upper run with the special conveyor screw 51 and via the magnetic separator 52 (sampling parts P). The magnetic separators 50 and 52 serve to remove secondary magnetic contaminants, e.g. As rust and abrasion.

With this dry sand classification, sharply classified grain bands can be achieved at low operating costs. Such quartz sands can z. As filter sand for gas filters, foundry sand for investment casting and special glass melts are used. When using a suitable earth-moist raw sand in the dry mechanical treatment of the raw sand is introduced with the belt conveyor 5 and the metering device 39 in the spin dryer 40, transported with the special screw conveyor 42 to the ram vibrating screens 53 with a mesh size of 0.8 mm and the lower reaches (sampling point Q) as salable product with the special screw conveyor 54 of the silo and loading system 20 supplied. According to the invention, in this processing technology there is also a whole series of possible combinations of mechanical ground, flotation and dry mechanical preparation, which make it possible to produce the most varied quartz sand products with very narrow or specific grain bands and quality parameters. In this case, the inventive method is characterized in particular by the fact that the investment and operating costs are low and that it is environmentally friendly.

Table 1: Main characteristics of the preparation - sieving characteristics

Sampling point - designation 1 0.63 0.5 0.4 Mesh size / mm 0.315 0.25 0.2 0.1 0.063 0.063 A - raw sand; Residual moisture.6% B - quartz sand slurry; Dirt density 500 g / l 3,1 2,5 0.9 0.9 1.6 1.7 5.0 5.6 Residue /% 19.7 22.4 19.3 22.3 28.6 28.9 17.0 17.1 1,2 1,2 0,5 0,5 3 2 1.5 1 Mesh size / mm 0.8 0.63 • 0.5 0.4 0.315 0.315 C - quartz sand slurry; Gravel moisture 12% 0.1 3.7 5.6 6.3 Residue /% 40.0 20.9 9.9 7.6 2.1 3.7 1 = 0.63 0.5 0.4 Mesh size / mm 0.315 0.25 0.2 0.1 0.063 0.063

D - quartz sand slurry;

Cloud density 500 g / l E - quartz sand slurry;

Cloud density 500 g / l F - quartz sand, wet;

Residual moisture 5% G - quartz sand slurry;

Cloud density 500 g / l H - silica sand slurry;

Dirt density 500 g / l

1.7 5.8 Residue/% 22.8 29.5 19.5 0.9 0.4 0.9 1.9 5.9 19.5 22.8 28.6 20.7 0.7 , 0.2 1.0 1.9 5.8 19.5 23.0 28.9 20.5 0.5 0.2 0.9 1.7 5.9 19.6 23.1 28.6 20.9 0.5 0.1 0.8 0.8 19.7 35.0 25.7 22.0 0.4 0.1 16.0

Table 2: Main characteristics of the preparation - sieving characteristics

Sampling point designation

Mesh / mm

0.63 0.5 0.4 0.315 0.25 0.2

Residue/%

0.1

0.063

I - quartz sand, damp;

Residual moisture 5% - 0.2 3.0

J - quartz sand, damp;

Residual moisture 18% - -

K - quartz sand, damp;

Residual moisture 5% - - -

L - quartz sand, damp;

Residual moisture 5% - - -

M-quartz sand, dried - 0.9 2.1

N - quartz sand, dried;

Relaxation chamber - - -

O - quartz sand, dried,

classified; Underflow - - -

P - quartz sand, dried,

classified; Headwaters - 1.6 4.4

Q - quartz sand, dried, unwashed,

sieved; Underflow - 1,2 3,1

16.0 26.8 38.0 10.0 5.5 0.4 0.1 0.8 16.1 35.2 26.6 21.0 0.3 - 0.8 16.0 35.3 26.6 21.1 0.2 - 0.9 16.1 35.5 26.9 20.3 0.1 8.4 23.3 36.1 20.4 10.3 0.4 0.1 0.3 7.9 12.2 30.8 40.2 7.4 1.2 0.6 1.8 24.8 34.5 36.3 1.8 0.2 31.2 37.0 15.7 7.2 2.8 0.1 - 5.8 24.0 23.5 26.5 15.2 0.4 0.3

Table 3: Main characteristic values of the preparation - quality parameters

Sampling point - SiO ₂ / Fe ₂ O ₃ / AI ₂ O ₃ / grout Glühver- Humine ' designation Wt .-% Wt .-% Wt .-% material / wt .-% loss / wt .-% A - raw sand; Residual moisture 6% 98.2 0.048 0.12 3.8 0,254 1.2 B - quartz sand slurry; Dirt density 500 g / l 98.2 0.046 0.112 3.2 0.231 1.0 C - quartz sand slurry; Gravel moisture 12% 96.3 0.46 0,128 3.0 0.3 0.8 D - quartz sand slurry; Dirt density 500 g / l 98.9 0.037 0,076 2.9 0.19 0.8 E - quartz sand slurry; Dirt density 500 g / l 99.0 0.028 0,069 1.2 0.15 0.5 F - quartz sand, wet; Residual moisture 5% 99.2 0,025 0,061 1.1 0.13 0.4 G - quartz sand slurry; Dirt density 500 g / l 99.2 0.023 0,060 1.0 0.13 0.35 H - quartz sand slurry; Dirt density 500 g / l 99.4 0.019 0.057 0.6 0.12 0.30

¹¹ Determination of extinction according to TGL 14317/12

Table 4: Main characteristic values of the preparation - quality parameters

Sampling point - designation

SiO ₂ / Ma .-%

Fe ₂ O ₃ / Ma .-%

Al ₂ O ₃ / sludge incinerators ¹¹

% By mass, substance /% by mass lust /% by mass

I - quartz sand, damp; 99.3 0.021 0.58 0.6

Residual moisture 5% J - quartz sand, moist;

Residual moisture 18% K - quartz sand, damp;

Residual moisture 5% L - quartz sand, wet;

Residual moisture 5% M - quartz sand, dried N - quartz sand, dried;

Relaxation chamber O - quartz sand, dried, classified;

Underflow P - quartz sand, dried, classified;

Overflow Q - quartz sand, dried, unwashed, sieved;

Underflow 98.8 0.036 0.072 2.7

^II Determination of extinction according to TGL 14317/12

0.13

0.17

0.20

99.4 0,018 0.054 0.5 0.12 0.28 99.4 0.016 0,052 0.4 0.11 0.27 99.7 0,008 0.047 0.3 0.10 0.10 99.3 0.024 0,060 1.0 0.12 0.35 98.9 0.52 0.073 4.2 0.38 0.80 99.2 0.026 0.058 0.9 0.12 0.35 99.3 0,022 0.058 0.8 0.11 0.30

0.6

Claims (4)

claims: 1. A process for the complex and partial treatment of quartz sand for the production of quartz sand products with the greatest possible reduction of pollutants from high-quality fluctuating, occurring in natural deposits quartz sands, characterized in that in a mixed water the Quarzsandtrübebungung with limed hot water, which is in a closed circuit , with pH values of 10 to 11 and Fe (OH) ₃ contents of <100 mg / l carried out in low-wear underwater rotary screens with mesh widths of 0.35 to 5mm and an axial pitch of 1:60, the wet classification, in attrition water jet conveyors with downstream Aufstromentämmpfung in tips the hydraulic promotion of quartz sand turbulence takes place, the hydraulic conveying speeds are between 1-2 m / s, in vacuum-equipped, open large-capacity filter tank lowering the residual moisture content of the wet-treated quartz sand Erdfeu In automatic flotation plants, the greatest possible reduction of pollutants takes place, in automatically operating systems with hot gas generator, spin dryer and downstream expansion chamber, the drying takes place, the flue gas temperatures <100 ° C and for desulfurization and dedusting of Flue gas vortex separator, coupled with heat pumps, connect, in closed and operated with vacuum special screw with external shaft bearings, the promotion of dry quartz sand, the relative velocities between the quartz sand and the screw wing are <0.3m / s, in ram vibrating screens with mesh sizes between 0 , 1 to 1 mm dry classification takes place and with magnetic separators magnetic secondary contaminants are removed. 2. The method according to claim 1, characterized in that compliance with the pH values and the Fe (OH) ₃ levels of the process water by an automatic control system via a constant dosage of quicklime with simultaneous addition of air and continuous removal of the resulting gypsum and Eisenhydroxidschlammes is ensured. 3. The method according to claim 1, characterized in that the Siebbelege the underwater rotary screens are made of plastics. 4. The method according to claim 1, characterized in that the special screw conveyors work with or without water cooling.