DD240147B1 - METHOD FOR THE COMPLEX AND PARTIAL PREPARATION OF QUARTZ SANDS - Google Patents

Description

According to the invention, the object is surprisingly solved by, when

- for the basic treatment, the service water in the supply is operated with pH values of 10-11,

The quartz sand is attrited and the quartz sand slurry is conveyed in a process step using attrition water jet conveyors, wherein the cavitation is used for attritioning and thus conditioning,

- The dew point of the exiting gases after the dryer is exceeded by coupling with a Wirbelbelabscheider until the end of the gas outlet.

embodiment

With reference to the flow diagrams shown in FIGS. 1, 2 and 3, the complex and partial preparation of a quartz sand obtained in a dry section from a natural deposit with different pollutants in terms of absolute amount and type of binding such as sulfidic, oxidic and siliceous heavy minerals, humins and Tone for the production of quartz sands 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 the essential quality parameters (content of SiO ₂ , Fe ₂ O ₃ , АІ ₂ O, slurries, humins and loss on ignition) are determined analytically as the main characteristic values and are listed in Tables 1-4. The letters Abis Q in FIGS. 1 to 3 designate the sampling points or the quartz sand products and in Tables 1-4 the associated analytical results.

The earth-moist raw sand (including Fe ₂ 03 contents of 200ppm to 2000ppm) is continuously fed with the bucket wheel excavator 1 type SR 130 via the belt conveyor 2 with a capacity of 400t / h in the Rohsandtagesbunker 3 with a capacity of 1000t. 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 automatic pH control system ensures that the pH is between 10 and 11 and the Fe (OH) ₃ concentration is <100 mg / l by the addition of quicklime 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 6). 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 1-2m / 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%) 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 the clarifier 13 is fed.

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 10Ot / h either as a finished product ( Quartz sand, wet) to 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 energy savings for the drying process or when using the drainage under vacuum that when using the processed quartz sand in the humid state, the construction cost of the large-capacity filter basins by approx.

50% can be reduced.

Via the emptying device 19, the belt conveyor 21, the metering device 22 and the attrition water jet conveyor 23 with a capacity of 20 t / h (sampling point G), the quartz sand or quartz sand slurry enters the flotation treatment (FIG. 2).

First, the unflotable grain fraction of> 0.35 mm is separated with the underwater rotary screen 24 (0.35 mm mesh size) and conveyed as a coarse grain fraction via 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 supplied or further refined in the dry mechanical treatment (Figure 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 fed to the clarifier 13 and the quartz sand slurry (sampling point J) and a defined amount of fresh water the flotation 31.

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 tank), the flotation for the production of high-purity quartz sands with the greatest possible 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 treatment (Figure 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 treatment 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 is automatically fed via the belt conveyor 38 with a capacity of 100t / h or the raw sand with the belt conveyor 8 to the metering device 39 with a capacity of 45t / h 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. The energy used is city gas, which is heated to 600 ^° C. in the hot gas generator 41. 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.

The Schletiderwellentrockner 40, the flash chamber 43 is connected downstream of the thereby depositing quartz sand (sampling point N) is fed via the special screw conveyors 44 of the silo and loading plant 20 or can also be used for example for the blending of 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 ° C passes hot flue gas stream for the dedusting and desulfurization in the Wirbelnaßabscheider 45. In this case, the dust content of about 40g / m ³ to 500 mg / m ³ is lowered and desulfurization of 50% at a pH reached from 10 of the inlet water. A portion of the heat energy of the flue gas is discharged to the continuously flowing input water of the fluidized bed cutter 45 (about 4.2 - 10 ⁶ kJ / h) and the Rfluchgastemperatur lowered to 40-50 ⁰ 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 ° 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 0.5mm is supplied. The quartz sand of the underflow is transported with the special screw conveyor 49 and via the magnetic separator 50 (sampling point 0) and the upper run with the special screw conveyor 51 and the magnetic separator 52 (sampling point P) to the silo and loading plant 20. 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 may e.g. used as filter sand for gas filters, foundry sand for investment casting and special glass melts. 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 0.8mm and the underflow (sampling point Q) supplied as a salable product with the special screw conveyor 54 of the silo and loading plant 20. 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

0.63 0.5 0.4

Sampling point designation

Mesh size / mm 0.315 0.25

0.2

0.1

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

0.063

A - B - raw sand; Residual moisture6% quartz sand cloud; 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

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

0.63 0.5

0.4 Mesh size / mm 0.315 0.25 residue /% 38.0 0.2 0.1 0.063 0.063 16.0 26.8 35.2 10.0 5.5 0.4 0.1 0.8 16.1 35.3 26.6 21.0 0.3 - 0.8 16.0 35.5 36.1 26.6 21.1 0.2 - 0.9 8.4 16.1 23.3 12.2 26.9 20 4 20.3 10.3 0.1 0.4 0.1 0.3 7.9 24.8 30.8 40.2 7.4 ^, Г 0.6 1.8 15.7 34.5 36.3 1.8 0.2 31.2 37.0 23.5 7.2 2.8 0.1 - 5.8 24.0 26.5 15.2 0.4 0.3

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

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

Probenahmestelle- 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 /% 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, damp;

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 (1)

1. Method for the complex and partial preparation of quartz sand for the production of quartz sand products with the greatest possible reduction of pollutants from quartz sands which vary greatly in quality and occur in natural deposits by means of groundwater treatment and service water, wet classification, quartz sand attritioning and conveying the quartz sand slurry and drying of the quartz sand. characterized in that - for the basic treatment, the process water is run in the flow with pH values of 10-11, The attrition of the quartz sand and the transport of the quartz sand slurry take place in a process step with attrition water jet conveyors and the cavitation is used for attrition, - The dew point of the exiting gases after the dryer is exceeded by coupling with a Wirbelbelabscheider until the end of the gas outlet. 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 processing of quartz sands is currently carried out depending on the location of the deposit by means of technological series of treatment steps such as classifying, attrition, sludge, flooding (for example according to DD-PS 148305), dewatering, drying and magnetic separation. For the basic treatment, process water with a pH value of 7 is used in the pre-run or untreated water in the water in mostly open circuits with a low treatment effect. The wet classification is operated with stream classifiers or with drum, sheet or mechanically excited screens with spray or rinse for producing the grain belts. Rotary screens are considered ineffective due to the low self-cleaning effect and are used only for minor special cases. Separated grain belts can only be achieved with power classifiers by multiple series connection. The attrition of the quartz sands as the most intensive treatment step to reduce pollutants is carried out in tube mills with or without grinding media, or attrition cells are used. This process step is very energy consuming, and the devices are subject to high wear. The promotion of Quarzsandtrübe for the production of a technological flow is preferably carried out by the gravity principle. The constructional consequence of such treatment plants are complex tower superstructures made of steel or reinforced concrete. Debris pumps are generally not used due to the high hardness of the quartz sand (Mohs hardness 7) and the resulting abrasive properties, which cause high pump wear. The drying of quartz sands is carried out in drying systems with high operating temperatures of 840 ⁰ C to 1000 ⁰ C, the exiting gases are after drying to the end of the steam path above the dew point. Heat recovery from drying systems is not common. Object of the invention It is to be created by eliminating the shortcomings of individual process steps, a process for the production of bulk and special sands by treatment of highly qualitative fluctuating, in naturally occurring quartz sands, the treatment savings on investment, energy and manpower compared to conventional methods and reduces the environmental impact , Explanation of the essence of the invention The invention is based on the object, an effective, environmentally friendly, automated and energy-saving process for the complex and partial production of quartz sand products with the greatest possible reduction of pollutants by treatment of highly qualitative fluctuating occurring in natural deposits quartz sands with SiO ₂ content of> 97%, Humin levels according to absorbance values of <2.0, annealing losses of <1%, Fe2O3 contents of <0.5%, and grain bands of 90% between 0.1-1 mm edge length by effecting and coupling individual conventional process steps.