DE2104048A1 - Inorganic, man-made filter sand and process for its manufacture - Google Patents

Description

Inorganic, artificially produced filter sand and process for its production,

The invention relates to an inorganic, artificially produced Filter sand for filtering suspended matter from liquids, in particular Water and a process for its production.

In the treatment of surface and groundwater into useful, industrial and drinking water, the removal of mechanical suspended contaminants by filtration is a common process step, in particular if flocculation with metal salts is carried out in the course of water purification will"

Filtration is easiest with layers of sand and gravel through ·· out, whereby large filter basins with coarse gravel, fine gravel and sand are layered in such a way that the grain size is finer from bottom to top.

Apart from the fact that the filter performance per m filter area because of the low Filter speed is low, the service life of the filter is short because practically only the filter surface is effective and one lower-level filtering is omitted. The filter speed can be increased considerably when closed Pressure filter used instead of the simple gravity filter will. In this case, too, only the surface of the filter filling becomes effective, the filter service life is also short. These can be extended considerably if the direction of filtration is opposite to Gravity, i.e. from bottom to top or from coarse to fine Granulation takes place because the precipitate is then retained in the filter material at a lower level. The filtration speed must be

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but to be lowered to a few m / h to whirl up the on the Fine grain layer on the pure water side - and thus secondary turbidity - to be avoided.

Optimal filtration conditions would exist if the filter layer were constructed in such a way that the lower layer had a grain size of approx. 0.2 l mm, above it a grain size of 1-1.5 now, then one of 1.5-2 mm and finally the top layer in one A grain size of approx. 2 - 4 mm would be arranged · Such a filter would allow with high filtration speeds in the direction of gravity operate, would have a deeply graduated filter effect and thus very much long service life with very low pressure loss. The breakthrough security would be great because the fine-grained filter layer at the water outlet acts as a safety zone in every load condition. A structured like this However, filters have not yet been used in practice because they cannot be regenerated by backwashing. When sedimenting after a possible rinsing was the coarse particles first and drop the fine ones last; thus the stratification would be reversed and all advantages initially achieved no longer apply.

Try to adjust the sedimentation order in the desired way Achieving the selection and use of products whose grain density is lower with a larger diameter than with a smaller one was only a partial success decided. The grain density of the substances usable for filtration could only vary between 1.8 and 2.5 kp / l will. Only the combination of hydroanthracite / quartz sand has found its way into practice, with the high price of hydroanthracite being one of them wide range of use sets limits.

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21040A8

The present invention aims to provide a new filter material to create that with the same material properties in terms of density can be varied between 1.0 and 2.2, can be produced at any density in this range in a grain size of 0.3-10 mm and in which the grain surface is made smooth or rough within wide limits can be.

Accordingly, the filter sand according to the invention consists of amorphous and / or crystalline powdery substances with a binder and / or an intermediate product produced in accordance with DBP 1.154.752 and / or DBP 1.182.577 and / or patent application P 16 71 266.6-45 to form beads are shaped and melted at temperatures above 700 C, and has different grain densities between approx. 1.0 to 2.2 g / cm as well as different grain diameters between 0.3 and 10 mm, with the proviso that the grain density with increasing grain diameter decreases. Furthermore, the filter sand is characterized by a grain with a smooth surface or a grain with a rough surface.

The amorphous and / or crystalline powdery substances together with the intermediate product in proportion 2 to 6: 1 finely ground, granulated with the addition of water, dried and optionally using release agents for Creating a rough melted surface, being in an ar « In the process, grain densities between 1.0 and 2.2 g / cm are formed. the If necessary, fine grinding is carried out together in a ball mill, Grind tube mill or similar equipment. The mix will with the addition of water, in which, according to a further feature of the invention, inorganic binders, such as water glass and / or organic binders such as polyvinyl alcohol, etc., be dissolved in amounts up to 5 ^ can, granulated, dried and then in a rotary kiln, fluidized bed furnace ο the like. Appaiatu-cea melted above 700 C. Under

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Is melting into this? Also in connection with melting or sintering to understand.

Instead of the specified preliminary product, a correspondingly fine product can also be used Glass powder of a sufficiently water-resistant and physiologically harmless composition mixed with blast furnace slag powder and, if necessary, ground together and then with dilute water glass solution or water, which may contain inorganic or organic binders, can be granulated. After the rock there is also here afterwards Melting at temperatures above 700 C to take place.

The formation of grain densities between 1.0 and 2.2 g / cm occurs through Expanding at temperatures between approx. 400 and approx. 700 C and a compacting melting at temperatures above approx. 700 C with partial Loss of bubble structure.

The grain density can be increased by the mixing ratio of slag powder Pre-product and / or glass powder are determined, depending on the quality and properties of slag powder and / or glass powder in general 4-40: 1, preferably 4-20: 1. Dwell time and / or temperature during the melting process offer further possibilities for variation the grain density, j

The addition is recommended for melting, especially in a rotary kiln a separating agent or powder (limestone powder, chalk, dolciaite powder, Kieselguhr, Schlackeniuehl etc.), to caking or sintering together to avoid the single grains. A possible excess of separating agents can easily be removed from the finished product by sieving, pneumatic classifying, soaking, etc. separated and, if desired, used again for powdering.

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The density of rubble or packing in the case of bulk or tripe can with a given product not only through the grain spectrum, but also through the grain shape can be influenced. As far as possible round grain shows, for example, with a narrow grain fraction a space filling of 55 · -58 / 6, with a broader range of grains 6Ο-65 J & the rounding is easily accessible, has a space filling of only 45-50 ^.

The surface roughness of the granules can be determined by the use well-known, physiologically sound release agent in a wide range Limits vary. The smoother the surface, the finer it is Release agent and the lower the applied ^ tight. The lighter the The bulk density of the release agent and the more bizarre its grain shape, the rougher the surface of the granulate will be · For example, the roughest one will be Structure preserved when using diatomaceous earth.

It has also been found that it is not necessary to adjust the grain size and to produce grain densities of differing filter materials for the different filter layers separately. Namely becomes a If mixed-grain granules of the same composition are subjected to the heat treatment, the small particles are warmed through faster and melted more bubble-free than the large ones. With suitable coordination of residence time and temperature, for example, a granulate mixture can be obtained in one operation in which the fines 0.3-1 mm higher grain density by about 0.5-0.8 g / cm than the particles with a diameter of 4-5 mm. will this Mixture of grains whirled up in water and allowed to sediment, shows

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themselves

that the fine grain settles first, while the coarse grain preferably settled last.

According to the invention, the use of the inorganic filter sand is in Intended for gravity and pressure filters.

The following exemplary embodiment serves to explain the invention.

example

100 kg of the preliminary product according to DP 1.154.752 are mixed with 300 kg of lacquer sand finely ground in a ball mill for 90 minutes Mixture is taken in the usual way on a granulating plate

from

Adding water to a grain size of 0.2 to 2 mm and then granulated dried in a rotary kiln at temperatures of up to 200 ° C. The pre-granulate obtained is treated with approx Grains mixed and brought to temperatures above 700 C (measured in the furnace outlet) in a rotary kiln heated directly in a direct flow. In the inlet zone of the rotary kiln up to about 400, the grain expands. With increasing warming to the outlet of the pipe towards the end the grain is condensed by advancing from the outside to the inside Sintering and / or melting.

By simultaneous melting treatment of the grains with different The diameter is a mixed granulate of the different according to the invention Grain density formed, with larger grains having a lower grain density than smaller ones, the bubble structure of which was largely lost. This mixed granulate is used as filter sand.

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Containers for filtering suspended matter from water have one on the bottom Water drain, above a coarse pebble filling, pebble diameter> 10 l \ tfm, above a sieve bottom with fine perforations, above the filter sand in Grain sizes from 0.3-2 mm. Gravity filters are located above the container the water inlet. So far, washed river sand with a uniform grain density has been used after rewinding and whirling up of the dirty filter sand was deposited in such a way that the larger grains were at the bottom and the finer ones at the top. The filter life quickly deteriorated due to soiling of the upper layer of fine sand, while the lower layer of coarse sand was not or only little used.

The filter sand according to the invention is stored due to its larger Grain diameter lower grain density after swirling up the filter sand backwashing was done completely differently. The heavier fine grains settle first and on top are the lighter, larger grains, so the filter service life is doubled and tripled, since almost the entire filter thickness can be used.

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Claims (1)

WASAGCHEMIE .. ^: " ^: .. ^: 'Munich, January 13, 1971 Gesellschaft mbH ^ 2104048 Claims / l _f Inorganic, artificially produced filter sand for filtering suspended matter from liquids, especially water, characterized, that it is made of amorphous and / or crystalline powdery substances, the intermediate product produced with a binding agent and / or according to DBP 1.154.752 and / or DBP 1.182.577 and / or patent application P 16 71 266.6-45 formed into spheres and at temperatures above 700 C, consists and different grain densities between approx. 1.0 to 2.2 g / cm as well as different Has grain diameter between 0.3 to 10 mm, with the proviso that the grain density decreases with increasing grain diameter. 2. Inorganic, artificially produced filter sand according to claim 1, characterized by a grain with a smooth surface, 3. Inorganic, artificially produced filter sand according to claim 1, characterized by a grain with a rough surface. 4. A method for producing the filter sandee according to claims 1 to 3, characterized, that the amorphous and / or crystalline powdery substances together finely ground with the preliminary product in a ratio of 2 to 6: 1, granulated with the addition of water, dried and, if necessary, with the use of release agents to create a rough surface 209832/0504 is melted, with grain densities between 1.0 and 2.2 g / cm are formed. 5 method according to claim 4, characterized, that the water used for granulation has inorganic binders, such as water glass and / or organic binders such as polyvinyl alcohol, etc., can be added in amounts of up to $ 5. ' 6 «Method according to claims 4 and 5» characterized, that the formation of grain densities between 1.0 and 2.2 g / cm by Expansion takes place at temperatures between approx. 400 and approx «700 C and a compacting melting at temperatures above approx. 700 ° C with partial loss of the bubble structure, 7. The method according to claims 4 to 6, characterized, that known, physiologically sound release agents such as chalk, kieselguhr, slag powder and the like are used to create a rough surface, S, use of the inorganic filter sand according to claims 1 to in gravity filters. 9 · Use of the inorganic filter sand according to claims 1 to 3 in pressure filters · 209832/0504