DE1143790B - Method and device for separating and drying solid particles from liquid suspensions and slurries - Google Patents

Description

Method and device for separating and drying solid particles from liquid suspensions and slurries The invention relates to a method and devices for separating and drying solid particles from liquid suspensions and sludge.

The purpose of the invention is to immediately after filtering or Dewatering the liquid suspension the surfaces of the filter cake or Sludge cake-forming solid particles dry without removing the particles themselves to be heated substantially in their mass. This is intended to increase the thermal efficiency drying improves and cooling after drying, at least partially, can be saved.

For separating and drying solid particles from liquid suspensions it is known to first dewater the suspension or sludge on filters and then the filter cake after removal from the filter of a thermal dryer to feed. Attempts have also been made to perform thermal drying on the filter itself to achieve that hot air was sucked through the filter cake. Here but noticeable drying can only be achieved if the treated Well a porous filter cake forms, which is practically only possible with salt crystals and granular material is the case. With finer goods it is either not possible at all, to suck or form significant amounts of hot air through the filter cake drying cracks through which the hot air passes without a drying effect to evoke. After all, attempts have also been made to achieve drying by that the filter cake was allowed to run under radiant heaters.

Such attempts have essentially failed because because the surface irradiation forms a very hard surface crust, which makes a drying process inside the filter cake completely impossible. In addition, the hard crust is also noticeable in a disturbing way.

On the other hand, it has already been proposed to use a filter cake the filter surface of a rotary drum and belt filter after it has been drained Irradiation by means of radiators or heating gases to dry. Here is but the surface of the filter cake is always more heated than its underside, and the degree of drying of the filtered material is consequently very different.

Hard surface crusts can form during drying, which make a subsequent comminution necessary, in the case of temperature-sensitive Material but such a treatment make it impossible at all. That the final material delivered does not have the desired final properties in any case.

So far it was only possible in individual cases, suspensions or to filter sludge by means of a single device and simultaneously to dry, and it was seldom possible to obtain a filtration product, that already the desired, z. B. has a packable final shape. In many cases however, up to now, simultaneous filtration and drying was carried out on one device not possible at all, either because the drying path is too short or because the required drying temperature had to be set too high.

In most cases it has therefore hitherto been necessary to use the Remove material from the filter and dry it in a separate device. However, this represents a very considerable expense in terms of equipment construction, in particular when only a relatively minor drying of the filter cake is desirable. In addition, the material circulation is proportionate due to the separate apparatus long, which in many cases can be harmful to the treated goods.

The invention is now based on the object of a method and devices to create by means of its already on a filter immediately after the end of the dewatering, the treated material is effectively dried can be.

To solve this problem, the filter cake is according to the invention in a horizontal filter with a rotating filter surface immediately after completion the dewatering is circulated at the same time during the subsequent drying. Here not only are the difficulties of the known methods and devices overcome, but also achieved a number of significant advantages.

For example, the invention in any case avoids that the discharged material agglomerates at the filter outlet and blockages or Causes blockages in the flow of material.

A device for carrying out this method is accordingly characterized in that at least one point on the filter surface behind the Dewatering section of the filter means for circulating the filter cake and at the same time a drying device for the material forming the filter cake is attached are.

A filter surface should be placed under a horizontally guided filter surface be meant whose inclination to the real horizontal is smaller than that Angle of friction of the material lying on the filter surface, because it depends on that also the material loosened by the circulation during the loosening and Drying process taken without difficulty by the moving filter surface and is thereby moved on.

In individual cases, especially when working discontinuously Filter, it may be useful to use the facilities for drying and circulating the To make the filter cake temporarily switched off and removable from the filter cake.

The type and mode of operation of the circulation devices can be understood by a person skilled in the art can be used according to the respective purpose. For example, the circulation devices according to the invention from attached to standing parts of the filter, in the filter cake protruding mechanical devices, e.g. plowshares, rakes, Harrows, spiked rollers, augers, etc. exist. The mechanical circulation devices can also have hollow recirculating tools protruding into the good position, on their lower part outlet nozzles for drying and loosening gas supplied to them are appropriate. With such devices a particularly fast and effective one Drying achieved with a relatively simple operation.

In another advantageous embodiment of the invention, the mechanical circulation devices also from one in the path of the filter or sludge cake brought mesh sieve exist, which the filter or sludge cake from his Lifts the layer and divides it into individual particles.

In another embodiment of the invention, above the filter cake at least one gas jet that produces a sharp gas jet directed onto the filter cake Be attached to the nozzle. This nozzle can be practically vertical or in an inclined position Angle should be directed towards the filter cake.

For particularly intensive and quick drying of the filter cake material this can be circulated in the form of a fluidized bed. This can be done below a wind chamber must be attached to the filter base, which extends over part of the filter extends and designed to receive compressed air to generate a fluidized bed is. However, it is also possible to have distribution devices a short distance above the filter base for compressed air to create a fluidized bed. With the fluidized bed the drying effect can be increased significantly that above the filter surface Heating elements are attached at such a height that they are in the fluidized bed produced immerse.

In a particularly useful embodiment, which is particularly suitable for Plulter suitable, the filter can be divided into treatment sections, of which those following the drainage section with recirculation and drying facilities, possibly of different types, are occupied. With such a division into sections of the filter can, if it is a vacuum filter, the vacuum air evenly or distributed in any proportions between the filtration and drying. The vacuum air can, for example, also be concentrated on the filtration. at A corresponding distribution of the compressed gas can be provided for pressure filters.

The drying elements used for drying the goods can have any shape; for example, radiant heaters are for some purposes practical, while hot air nozzles are preferable for other purposes. For one In addition to hot gas flow, fluidized beds are particularly suitable for drying elements heated contact surfaces for the goods to be dried.

All these conceivable embodiments of the circulating and drying devices are for horizontal filters with a circumferential filter surface of various types and training applicable.

Some exemplary embodiments of the invention are shown in the drawing.

Fig. 1 shows a plan view of a for performing the method according to the plan filter set up according to the invention; Fig. 2 shows in perspective a section of a wandering filter cake, which is by hook-like devices is loosened and circulated; Fig. 3 shows a ploughshare-like in vertical section Loosening and circulation device with simultaneous introduction of air or Gas in the loosened filter cake; Fig. 4 shows a perspective partial representation a loosening and circulating device working with hard gas jets for the Filter cake; in Fig. 5 is a schematic section of the fluidized bed loosening and drying of the filter cake, Fig. 6 shows schematically a loosening, Circulation and drying device for the filter cake with a mesh screen is equipped; Fig. 7 shows in vertical section a mounted on a filter Discharge screw, which is also used to mix differently dried out Layers of the filter cake are used.

In the illustrated in Fig. 1 implementation of the method according to Invention on a filter with a horizontally guided filter surface, shown in the In the case of a rotating plane filter, the filter surface is divided into several sections divided. From the discharge device of the filter first runs over the section A. empty the filter medium in a known manner in order to be cleaned. Through the feed facility 1 then the suspension to be filtered or the sludge to be filtered becomes more uniform Layer applied to the filter medium. Then takes place over the area B in a known manner the first dewatering of the material to be filtered. It can this is followed by one or more washing sections C, which are carried out in a known manner can be provided with devices 2 for applying a washing liquid.

This per se known filtering process is followed by the Invention directly a loosening, circulating and drying process of the filter cake at. This process takes place in the illustrated embodiment of the invention in Area D of the filter surface. This section D is then followed by the discharge section E, in which by the mixing action of the usual discharge screw 3 from the Loosening, circulating and drying section D of the incoming goods thoroughly mixed again will.

The loosening, circulating and drying of the filter cake forming In the embodiment shown, good results are achieved by the simultaneous attachment of loosening and circulation devices 4, as shown in more detail, for example, in FIG are shown, and of drying devices 5, which in the illustrated embodiment can for example consist of infrared radiators.

As can be seen from Fig. 2, the device 4 can loosen up and circulating the filter cake 6 consist of a series of hooks 7, optionally are sharpened downwards and up to a short distance above the Filter medium, for example the filter cloth, extend.

The hooks 7 are at a small distance above the filter cake 6 lying common rod 9 attached. The rod 9 can be rotatably mounted, Pivot the hook 7 out of engagement with the filter cake 6 if necessary to be able to.

As can be seen from Fig. 1, several such rods 9 with Hook 7 to a harrow-like device for loosening and circulating the filter cake be united.

As can be seen from Fig. 3, instead of the hooks 7 on the rods 9 ploughshare-like loosening and circulating elements 10 may also be attached.

These ploughshare-like circulating elements are particularly suitable when the filter cake is made up of very fine particles. According to Fig. 3 is the Another possibility given, the support rod 9 for the loosening and circulating elements as a tube 11 and to attach to this support tube nozzle tubes 12, which are shown in protrude the loosened by the loosening elements 7 and 10 and Gutlage Blow drying or loosening gas from the carrier tube 11 into the material layer. These nozzle pipes 12 can with the loosening and circulation elements 10 from one Pieces exist or be attached to these. In the case of hook-like loosening elements, As shown in Fig. 2, these elements 7 themselves can be used as nozzle pipes be trained. But it is also possible to alternate the nozzle pipes 12 at a distance to be arranged between the loosening and circulating elements 7 and 10, respectively. When through the nozzle pipes 12 hot air is blown in, can optionally from further drying elements be disregarded.

Another embodiment of the invention is illustrated in FIG. In the embodiment of the invention shown there is above the filter, d. H. at a distance above the filter medium 8 and the filter cake 6, a pressurized gas pipe 13 arranged, which has pressure gas nozzles 14 directed at the filter cake 6. These Pressurized gas nozzles 14 can be arranged laterally in a row or by means of branch pipes 15 be offset. Sharp gas jets emerge from the compressed gas nozzles 14, which penetrate in the migrating in the direction of arrow 16 filter cake 6 and this Throw up and circulate like a crater. The circulation effect can be increased by this, that the nozzles 14 are mounted so that the gas jets at an angle of inclination penetrate the surface of the filter cake 6. If the facility described is charged with heated gas, can optionally be used on further drying facilities be waived.

In Fig. 5, an embodiment of the invention is shown schematically, in which the loosening and circulation and possibly also the drying thereby be achieved that the filter cake 6 after leaving the drainage section the filter is brought into fluidized bed condition. This is illustrated in the Embodiment achieved in that above or below the filter medium 8 or as an intermediate layer in the filter medium distribution devices for feed from below Pressurized gas are attached.

In the embodiment shown, there is a lower filter cloth 8 'applied a bulk material layer 17 and this bulk material layer 17 with a second Filter cloth 8 "covered. This second filter cloth 8" then carries the filter cake 6, in the direction of arrow 16 together with the filter cloths 8 'and 8 "and the Schüttgutlagel7 moves. While in the area of drainage gas from top to bottom is passed through the filter cake 6, as indicated by the arrows 18, is when Exceeding the chamber partition 19 between the drainage section and loosening, The circulation and drying section reverses the direction of flow of the gas, d. H., If necessary, heated gas is fed into the filter from below, as indicated by the arrows 20 indicate, supplied in such an amount and with such pressure that it is capable of 17 distributed gas loosens the filter cake 6 to form a fluidized bed 21. In the Fluidized bed 21 is whirled through once the entire material and intimately with one another mixed and constantly circulated. In addition, and due to the loosening air, a crop layer that has not yet been crushed subject to constant abrasion and thereby distributed. If that's to maintain the fluidized bed 21 be used gas is not preheated or its heat content is not sufficient to dry the filtered material sufficiently, additional drying devices can be used be attached above or within the fluidized bed 21. In the example of the Fig. 5, a coil 22 is provided within the fluidized bed 21, which through suitable means is heated from the inside. By touching the whirled up Particles with the pipe coil 22 are heated on their surface, so that the liquid adhering to its surface evaporates and is carried away by the pressurized gas will.

Another way to carry out the procedure after The invention is illustrated in FIG.

There, too, the filter cake 6 migrates with the filter medium 8 in the direction of the arrow 16. In doing so, he reaches a mounted above the filter medium 8 Mesh sieve that he has to enforce. Has in the illustrated embodiment the mesh screen is in the form of a rotating drum 23. Expediently, the Sieve drum 23 in the same direction as filter cake 6, as indicated by arrow 24 is indicated, revolve at increased speed. Is expedient In addition, the height of the sieve drum 23 can be adjusted in relation to the filter medium 8. During operation, the filter cake 6 is when it reaches the drum 23 in the Meshes pressed in or peeled off by the drum. By rotating the Drum 23 is cut through its mesh of filter cake 6 into small pieces. These pieces 25 are subjected to constant movement inside the drum 23, d. that is, they are taken at the rear end of the drum with the wall facing up and roll down the slope 26. This continues until the bits 25 have worn themselves so far that they can pass through the sieve mesh of the Drum 23 can step outside again and thereby result in the loose layer 27. In order to allow drying during the constant movement of the pieces 25 through one another to achieve on the surface of the filtered particles and thereby the disintegration to accelerate the pieces 25, a fixed inside the sieve drum 23 Radiation heaters 28 may be arranged.

This radiant heater is expediently attached so that he the Embankment 26 irradiated.

A further drying effect can then be achieved, albeit directly behind the sieve drum 23, a further radiant heater is attached.

As a result, those that are still in motion get out of the sieve drum 23 escaping pieces and solid particles in the area of the radiant heater 29 and are thereby dried on their surface.

By suitable setting of the loosening and circulation devices, As shown in Figs. 1, 2, 3, 4 and 6, the loosening, circulating and drying process can be limited to an upper layer of the filter cake. It is also possible, by connecting several such devices in series, As shown, for example, in FIG. 1, several layers of different degrees of dryness of the filter cake.

This possibility can be used expediently in particular, if partial drying of the filtered material is desired. That way you can namely, the state of drying of the discharged goods is relatively accurate and simply regulated by the height adjustment mechanism of the loosening and circulation devices will. The filter cake resulting from such a multi-layered filter cake But then well must be intimately mixed when or after leaving the filter. This happens, for example, as shown in Fig. 7, in a conventional discharge screw, for example with plane filters. In the illustration of FIG. 7, this moves again Filter medium 8 with the treated filter cake w in the direction of arrow 31 the discharge screw 32 to, which in the direction of arrow 33 to runs. In the illustrated For example, the filter cake 30 consists of the two layers 34 and 35.

While the upper layer 35 in the manner described above largely has been dried, the layer 34 has not been subjected to any treatment, but is in the usual state of a filter cake to be discharged. In the discharge screw 32, the lower layer 34 is first cut into individual pieces 36 torn, while the largely dried material of the layer 35 as trickling material the spaces between the filter cake pieces 36 fills. This occurs first moisture exchange between the dried particles of layer 35 and the pieces 36 of the layer 34, whereby these pieces 36 are dried and better disintegrate in the following. In addition, through the movement of the screw 32 a constant movement takes place within the accumulation of material37 which is forming, whereby the pieces 36 are ground very quickly and thus the material of the layer 34 in the material of the layer 35 is mixed in. The smaller the pieces 36 during this The faster a moisture exchange takes place between the treatment Good of the layer 35 and the good of the layer 34 instead, so that the leaving the filter End product has a uniform, controlled level of moisture.

All working methods and facilities as described above, described in particular with regard to filters with horizontal filter surface feed can also be used for filters with only parts of the horizontal filter surface guidance to be used.

In addition to the examples given, the invention can also be used anywhere can be used with advantage where a good location drains and with a certain Degree of dryness should be obtained without the material being significantly heated should experience.

Claims (17)

PATENT CLAIMS: 1. Process for separating and drying solid particles on liquid suspensions and sludges on horizontal filters with rotating Filter surface, both of which are followed by a drying of the filter cake after the filtration takes place on the filter, characterized in that the filter cake directly after completion of the dewatering during the subsequent drying at the same time is circulated. 2. Horizontal filter with a circumferential filter surface for implementation of the method according to claim 1, characterized in that at least one Place a device on the filter surface after the drainage section (C) of the filter for circulating (4) the filter cake (6) and at the same time a drying device (5) are appropriate for the material forming the filter cake. 3. Horizontal filter according to claim 2, characterized in that the devices for drying (5) and circulating (4) the filter cake can be temporarily switched off and can be lifted off the filter cake. 4. Horizontal filter according to one of claims 2 and 3, characterized in that that the circulation device (7, 10) from standing parts (9, 11) mechanical circulation devices attached to the filter and protruding into the filter cake consists. 5. Horizontal filter according to claim 4, characterized in that the mechanical circulating device is hollow circulating tools protruding into the good position (12), on the lower part of which there are outlet nozzles for drying and loosening gas are attached. 6. Horizontal filter according to one of claims 2 and 3, characterized in that that the mechanical circulation device, for example, is in the form of a worm (32) and is attached above the filter base (8). 7. Horizontal filter according to one of claims 2 and 3, characterized in that that above the filter cake at least one sharp on the filter cake directed gas jet generating nozzle is attached. 8. Horizontal filter according to one of claims 2 and 3, characterized in that that a wind chamber (19,20) is attached below the filter bottom, which Extends over part of the filter and for receiving pressurized gas for generating a fluidized bed (21) is formed. 9. Horizontal filter according to one of claims 2 and 3, characterized in that that immediately above or below the filter base distribution devices for compressed gas, e.g. B. bulk material layers (17) for the solid production of a fluidized bed, are appropriate. 10. Horizontal filter according to claim 9, characterized in that immediately above or below the filter base distribution devices for Pressurized gas, e.g. B. a layer of granular material (17) attached to the their upper side (8 ") and their underside (8 ') with an air-permeable medium, for example the filter medium is covered. 11. Horizontal filter according to one of claims 8 to 10, characterized in that that heating elements (22) are attached at such a height above the filter surface, that they are immersed in the fluidized bed (21) produced. 12. Horizontal filter according to one of claims 2 and 3, characterized in that that above the filter medium in the path of the filter cake a mesh sieve in such a way it is appropriate that the filter cake penetrates the mesh of this sieve. 13. Horizontal filter according to claim 12, characterized in that the mesh screen in the same direction as the filter cake (6), but with a higher Peripheral speed is designed as this revolving screen drum (23). 14. Horizontal filter according to one of claims 2 to 13, characterized in that that the filter is divided into treatment sections, which on the dewatering section (C) following with circulation and drying devices, possibly different ones Kind, are busy. 15. Honzontal filter according to one of claims 2 to 14, characterized in that that the drying elements consist of radiant heaters (29). 16. Horizontal filter according to one of claims 2 to 14, characterized in that that the drying elements consist of hot air nozzles. 17. Horizontal filter according to one of claims 2 to 14, characterized in that that the drying elements from heated contact surfaces (22) for the to be dried Pass well. Considered publications: German Patent Specifications No. 886 592, 927 265, 1015412; German patent application C 4639 V / 82a (made known on July 9, 1953); Swiss Patent No. 213 776.