WO1996041669A1

WO1996041669A1 - Process and device for removing impurities from a liquid

Info

Publication number: WO1996041669A1
Application number: PCT/EP1996/002473
Authority: WO
Inventors: Thomas Prass; Jörg Friedrich GREBER
Original assignee: Parzival Beteiligungen Ag
Priority date: 1995-06-08
Filing date: 1996-06-07
Publication date: 1996-12-27
Also published as: DE19520975C2; DE19520975A1

Abstract

A process is disclosed for removing impurities from a liquid. The liquid is made to flow between the substantially parallel, inclined plates of a plate arrangement.

Description

"Method and device for removing impurities from a liquid"

DESCRIPTION

The invention relates to a method for removing contaminants from a liquid according to the preamble of claim 1. The invention further relates to a device for removing contaminants from a liquid, which is suitable for carrying out the method.

Liquids are obtained in many technical processes which contain a large number of different impurities. In order to be able to use these working fluids repeatedly, they have to be cleaned. The contaminated liquids are, for example, cooling lubricant suspensions, cooling and lubricating oils in metalworking or suspensions of soil-rich water in soil remediation. These liquids mostly consist of costly and environmentally harmful substances, so that efforts are made to clean these liquids as well as possible and to reuse them.

A large number of different methods are generally known for separating the impurities contained in a liquid. Various types of filtrations in which the suspension to be cleaned is applied to a belt filter are widespread. The impurities remain on the filter fleece and the cleaned suspension is collected below the filter fleece by means of suitable devices. Such belt filter devices have the disadvantage that they can essentially only reliably remove solid impurities from the suspension. Suspensions which, in addition to solid substances, also liquids, for example in the form of oil droplets, can not be satisfactorily prepared with band filters because the liquid contaminants can only be trapped to a very small extent by the filters. However, this is particularly important if, for example, cooling lubricant emulsions, which contain greasy and lubricating components, in particular metal soaps, are to be cleaned. The liquid contaminants lead, among other things, to a sticking together of the pores of the filter cloths, so that they have to be exchanged frequently in order to maintain a desired performance of the filter system.

Another method of removing contaminants from liquids is performed in a centrifuge. The centrifuge creates an artificially increased gravitational field in the liquid and thereby separates the suspension therein into heavy, medium and light components. In the outlet of the centrifuge, it is possible to remove the different fractions of the contaminants separately. A disadvantage of this method is that the heavy impurities in the liquid are very strongly compressed by the high centrifugal forces and their removal from the centrifuge is thereby made more difficult. The centrifuges used for this method also have a complex construction.

Finally, a method for removing impurities from a liquid is known which ^{• works} on the principle of gravity. Such a method is known from German Utility Model No. 93 08 282. According to this method, the liquid contaminated with impurities is passed through a package of obliquely arranged plates with a very low flow rate from bottom to top, the impurities being deposited on the plate surfaces and after agglomeration or connection, which is partly favored by surface effects ¬ the solid or liquid impurities migrate from this surface. The heavy solids are stored in the lower area of the plates and the lighter, liquid contaminants flow upwards. This cleaning process results in uneven deposits of the impurities on the plates and an unsatisfactory separation of fine dirt particles. If the plates are arranged closer together, the cleaning is improved, but this leads to increased deposits which can lead to a blockage of the spaces in the plate pack. Accordingly, according to the above-mentioned utility model, it was proposed to hang the plates on both sides on two frames arranged one above the other. For cleaning, the frames are aligned vertically one above the other in order to bring the panels into a vertical position that allows a maximum distance between the individual panels. The plates are then cleaned with compressed air.

The object of the invention is to provide a method and a device for removing impurities from a liquid, with which the removal of impurities can be carried out even more effectively and the cleaning of the plates after longer operating times and in a simple manner is made possible.

This object is achieved by the method and device defined in the independent patent claims. Advantageous developments of the invention are specified in the subclaims.

The invention is explained in more detail below on the basis of exemplary embodiments with reference to drawings:

Show it:

1 shows a front view of a plate device of the device for removing contaminants from a liquid; FIG. 2 shows a side view of the plate device shown in FIG. 1;

Fig. 3 is a partial sectional view of the front of the plate device shown in Fig. 1 in the tilted position;

4 shows a side view of a further embodiment of the device for removing contaminants from a liquid;

FIG. 5 shows a front view of the device shown in FIG. 4;

6 shows a schematic illustration of the plate arrangement shown in a plate device; and

7 shows a spatial representation of the plate arrangement according to a further embodiment of the device.

Figures 1 to 3 show a device for performing the method according to the invention for removing contaminants from a liquid. The device has a plate device with a lower frame 1 and an upper frame 2, which are displaceable relative to one another. A plate pack 3 is held between the frames with a plurality of plates 4 which are parallel to one another and are pivotably mounted on the frames 1, 2 on the underside and on the top.

Fig. 1 shows the plate device in a position in which the frames 1, 2 are aligned perpendicular to each other and Fig. 3 shows the position of the frame in its operating position in which the plates are aligned inclined to the vertical.

The respective outer plates 4 of the plate pack 3 are movably connected on both sides to the lower frame 1 and the upper frame 2 by means of articulated arrangements 5, so that the frames 1, 2 are movable allelogram-like to each other. The inner and outer plates 4 of the plate pack 3 are pivotably mounted with their lower and upper edges in associated grooves 6 of the frames 1 and 2, respectively. In the illustrated embodiment, the grooves 6 have a triangular cross section. By moving the frames 1, 2 towards each other, the inclination of the plates 4 can be changed depending on the desired operating conditions. The plates 4 are at a predetermined angle to the vertical, which results from the cleaning task to be solved. When separating specifically heavy contaminants from liquids, smaller angles are advantageous. Specifically lighter impurities are separated with plate packs in which the plates 4 have a larger angle to the vertical.

2 shows a side view of the plate device consisting of a plate pack, through which a flow F _{0 of} the liquid to be cleaned flows. The device according to the invention also has a device (not shown in FIG. 2) for introducing the liquid to be cleaned, essentially horizontally and along the plate surfaces of the plate pack, as can be seen from the illustration in FIG. 2. In the plate pack 3, the plates 4 are preferably at a distance of 0.5 to 10 mm apart.

Because the liquid to be cleaned flows horizontally through the gaps formed by the plates, solid particles or liquid bubbles which have a different density are deposited at different points along the surface of the plate as a result of their different sinking or rising speeds that the processes of their agglomeration or connection and their subsequent sinking or rising in the liquid do not interfere with each other.

In the conventional method, the rising and falling movements of the light and heavy contamination particles overlap with the movement of the rising liquid flow. This creates agglomerations of heavy impurities with the Upstream is shipped and its desired sinking is hindered. As a result, the cleaning performance of the plate pack decreases. At the same time, the system becomes sensitive to fluctuations in throughput, which are common in normal operations. Fluctuating ascending flow velocities lead to the fact that the contamination agglomerates on the plate packs are destroyed and the contaminants are discharged with the liquid flow and thus the cleaning performance is reduced. With the horizontal flow against the plates, the damaging effects of the conventional methods are effectively avoided. Accordingly, it is possible to arrange the plates even closer together, thus increasing the intensity of the cleaning. This advantage is particularly evident in the case of liquids which, in addition to coarse solid particles, also have fine sticky solids with a slight difference in density from the liquid medium. If such liquids are cleaned by the generic device described above, in which the liquid rises from bottom to top in the interstices of the plate pack, there is a more intensive mixing of these two types of solids than in the invention and a resultant one rapid growth of deposits adhering to the plate surfaces takes place, which considerably hinders the removal of the contaminants which have grown together.

FIGS. 4 and 5 show a further exemplary embodiment of the invention, in which the plate device consists of a plurality of plate packs arranged one behind the other in the direction of flow of the liquid and having different angles of inclination. As a result, the separation space in the plate device is divided into different areas which are matched to the different properties, in particular the rate of climb or descent, of the lighter and heavier impurities. Corresponding studies have shown that a smaller angle of incidence oti to the vertical is advantageous for the preferred separation of speci ﬁ c heavier particles from a liquid than for the Separation of specifically lighter impurities which require a larger setting angle α ₂ (FIG. 6). The latter applies both to the impurities which have a higher specific density than the liquid, and to the impurities which are much lighter than the liquid. In FIG. 6, arrows are used to compare the distances that a particle located in the middle between two plates 4 has to store in order to reach one of the plate surfaces. Accordingly, the particles, ie, decrease at a considerably in comparison to the liquid ^'greater density particularly heavy particles quickly. However, in the first, only a small angle with the perpendicular plate pack, these have to cover a longer distance to the lower plate surface. The particles behave similarly, which have a significantly lower density compared to the liquid, ie are particularly light. These particles will rise quickly, but have to travel a longer distance to the upper plate surface. In contrast, the particles with a lower density difference to the liquid rise or fall more slowly, but in the second plate pack, which closes a larger angle with the vertical, they are closer to the corresponding plate surface. This peculiarity of particle separation according to the method according to the invention thus leads to the fact that the particles separate at the plate surfaces of different inclinations essentially simultaneously regardless of their specific density. This allows the device to be made even more compact.

In the device according to the invention, tapping devices can be installed at the points at which the partially cleaned streams Fl and F2 (FIG. 4) emerge from one plate pack and flow into the next, in order to extract partial quantities of the liquid with a certain cleaning quality ¬ men. According to the exemplary embodiment shown in FIG. 7, the device according to the invention consists of a plate device with only one plate package of the type shown in FIGS. 1 to 3, the frames 1, 2 and only one plate 4 being shown schematically in FIG. 7 are shown. The twisted position of the plates 4 is achieved according to this embodiment in that the upper frame 2 is rotated parallel to the lower frame 1 by a certain angle. The connection of the plates 4 ensures that the angle of inclination of the plates with respect to the perpendicular increases continuously in the direction of extension of the plate and in the direction of flow of the liquid. A further increase in the compactness of the device according to the invention can be achieved by this construction.

In a further exemplary embodiment, the plates of the plate device are made of elastomeric materials, for example of rubber, which are installed in the frame 1, 2 under a certain pretension. It has been found that such plates have an effect, partly due to their specific surface tension, which promotes the agglomeration of the particles. On the other hand, this particular embodiment of the invention allows the plates 4 to be tensioned and / or relaxed at suitable time intervals, in order to thereby advantageously remove particle deposits or incrustations from the plate surfaces. For this purpose, a device for applying a cyclical stress curve to the elastic plates can be built into the device according to the invention, which device makes it possible to clean the plates in the installed state. This type of cleaning of the plates can be carried out not only during short breaks in operation of the device, but also during the cleaning operation of the liquid.

The invention is not limited to the advantageous embodiments described above, but extends to various combinations of the techniques shown above. Depending on the type and amount of the contaminants contained in the liquid to be cleaned, various combinations of plate packs can be used. For example, in the embodiment of the device shown in FIG. 4, the second plate pack 4b and the third plate pack 4c can be designed in the manner of the embodiment shown in FIG. 7.

The invention also includes such an embodiment, in which the device comprises only a single plate pack, in which each plate initially extends in the direction of flow at a constant angle of inclination to the perpendicular and only at its rear end in the direction of flow according to the position shown in FIG. 7 shown is rotated so as to increase the inclination of the plates in the discharge area of the liquid.

Claims

PATENT TO SPEECH

1. A method for removing impurities from a liquid, in which the liquid is guided between plates (4; 4a, 4b, 4c) arranged essentially parallel to one another and inclined to the vertical, a plate device, characterized in that the liquid is guided essentially horizontally and along the surface of the plate.

2. The method according to claim 1, characterized in that the plate device consists of several plate packs (4a, 4b, 4c) arranged one behind the other in the direction of flow of the liquid and having different angles of inclination.

3. The method according to claim 2, characterized in that the angle of inclination of the plate packs (4a, 4b, 4c) increases in the direction of flow of the liquid.

4. The method according to claim 2 or 3, characterized in that Parts of the cleaned liquid are removed at various points between the plate packs in the direction of flow.

5. The method according to any one of claims 1 to 4, characterized in that the plates (4, 4a, 4b, 4c) consist of elastomeric materials and are tensioned and / or relaxed in certain working cycles.

6. The method according to any one of claims 1 to 5, characterized in that the plates (4, 4a, 4b, 4c) are arranged at a distance of 0.5 to 10 mm from each other.

7. Device for removing impurities from a liquid with a plate device which has a plurality of plates (4, 4a, 4b, 4c) arranged essentially parallel to one another and inclined to the vertical, and with an inlet device for introducing the ones to be cleaned Liquid between the plates, characterized in that the inlet device is a device for introducing the liquid to be cleaned substantially horizontally and along the plate surfaces.

8. The device according to claim 7, characterized in that the plates (4) have a variable inclination in the direction of flow of the liquid.

9. The device according to claim 8, characterized in that the plate device consists of a plurality of plate packs (4a, 4b, 4b) arranged one behind the other in the flow direction of the liquid, with mutually different inclination angles.

10. Apparatus according to claim 8 or 9, characterized in that the plates (4) are rotated so that each plate has a variable inclination angle in the flow direction of the liquid.

11. Device according to one of claims 8 to 10, characterized in that the angle of inclination of the plates (4) increases in the direction of flow of the liquid.

12. The device according to one of claims 7 to 11, characterized in that the plates (4) consist of elastomeric materials.

13. The apparatus according to claim 12, characterized in that the plates (4) between two superposed and mutually rotatable frames (1, 2) are stretched.

14. Device according to one of claims 7 to 13, characterized in that the plates (4) are arranged at a distance of 0.5 to 10 mm from each other.