EP1827665B1 - Device for adding a powdery or granulated liquid-soluble polymer flocculation aid to a liquid - Google Patents

Abstract

The invention relates to a device for adding a powdery or granulated flocculation aid to a liquid. The device includes a container for receiving the flocculation aid to be added, the flocculation aid being mixed with a liquid by a controllable dosing element. The device is provided with scales for determining the weight of the flocculation aid to be supplied by the dosing element, and the quantity of flocculation aid is adapted to the quantity of liquid flowing through by a control system. A rotor-stator arrangement has a plurality of perforated disks arranged downstream from each other in the axial direction, used for the final reliable dissolution of the flocculation aid in the liquid.

Description

The invention relates to a device for the metered addition of a powdery or granular liquid-soluble flocculation aid in a liquid according to the preamble of the main claim.

In sewage treatment sludge water, which still contains up to about 5% solids, is mixed with a dissolved flocculant-containing liquid (preferably water). These flocculants are in particular synthetic polymers based on acrylamide, acrylic acid and methacrylic acid and their esters. Rarely, however, natural polymers such as starch, guar or Moringa seeds are used. These polymers act as flocculants in combination with inorganic precipitants. The solids attach themselves to this flocculant and can then be precipitated more easily.

Such flocculation aids are offered as granules in which a polymer gel formed in an aqueous monomer solution after the polymerization is comminuted, dried, ground and classified, or else as a bead polymer which is formed by an inverse suspension polymerization. In this, an aqueous monomer solution is dispersed and polymerized in a non-miscible solvent (e.g., cyclohexane). The polymer is then separated as a finished bead from the solvent.

It is also known to market such flocculants as emulsion polymers. For these, the aqueous monomer solution is emulsified in an immiscible carrier, for example isoparaffin, and polymerized. The carrier and the emulsifiers remain in the product. The latter causes in particular disadvantages in the cost structure of these products. On the one hand, the carrier means are relatively expensive and, on the other hand, the carriers remaining in the product are negatively impacted on the transport costs due to their volumes and their weight.

In this aspect, it is particularly preferred to use dry, granular or pearl-shaped or powdery flocculation aids.

In order to produce a liquid added with such flocculation aids, it has heretofore been known to manually add the flocculation aids supplied in sacks and containers to a liquid which is present in a known amount in a tank and then to dissolve the flocculation aids in the liquid by means of a stirrer.

Alternatively, it is also known, such flocculation aids by means of a screw conveyor or the like. from above to give up a liquid and then dissolve the flocculants again by means of a stirrer. This stirrer can either be permanently mounted in the tank or used as an external agitator to dissolve the flocculant in the tank.

Here it is problematic that the dosages made in the ways described are relatively inaccurate. In particular, the former method is also relatively cumbersome because of the manual handling of the flocculant. Furthermore, the subsequent dissolution with the stirrer is relatively tedious and ineffective.

It has been found that in these types of dosing between 20% and 25% of the supplied flocculants in the liquid clump and then can not be resolved.

As a result, basically existing cost advantages of said dry traded flocculants are also consumed, since these flocculants are then usually metered higher to compensate for this poor resolution.

Object of the present invention is therefore to provide a device with which a more effective dosing of dry-traded flocculants is possible, in which a more precise dosage is to be achieved and with which the handling should be facilitated.

It is from the DE 26 27 367 and the WO 03/043723 It is known that a device for metered addition of the powdery or granular liquid-soluble flocculation aid has a compressed-air line with which the flocculation aid is transported to the liquid.

The invention is based on the finding that the powdery or granular flocculation aid can be dissolved more easily in the liquid when the particles are wetted individually with liquid. This is achieved by injecting the flocculation aid with compressed air into the liquid. This prevents the flocculant in the liquid from clumping and then dissolving completely.

Although it would be generally sufficient to inject the flocculant in the manner described in a liquid-filled tank, it is preferred that the compressed air line opens into a conduit which is flowed through as in the objects of the above-mentioned publications of the liquid in the the flocculant is to be mixed. As a result, a particularly accurate dosage can be achieved.

In a particularly preferred embodiment according to the invention, such a device for the metered admixture of a powdery or granular liquid-soluble flocculation aid into a liquid has a container for receiving the admixing flocculant, which is connected to the liquid-flowed conduit with the interposition of a controllable metering element. In this case, the liquid-flow line is associated with a flow measuring device. In addition, there is a weighing device which determines the weight of the flocculation aid dispensed by the metering element, this weighing device, as well as the aforesaid flow measuring device, delivering signals to a controller acting on the metering element in response to these signals this is functionally connected.

The development has the advantage that with her a particularly reliable and accurate dosing and admixture of a flocculant with mechanical means can be achieved, in particular, due to the provision of the weighing device here also ensures the required precision is because this can be compensated for by the flocculation aid possibly existing density differences.

It has proven to be advantageous in this case to couple the weighing device to the container which contains the flocculation aid to be admixed, so that it then delivers signals as a function of the weight loss of this container. By this constellation, a solution is achieved, which can be realized with structurally proven means.

The proposed metering device preferably has a controllably rotatably drivable cell wheel. This cellular wheel, which resembles a gear in its appearance, makes it possible to dose the flocculants very precisely.

It has proven to be advantageous to provide the cellular wheel at its periphery with teeth ending substantially in lines. As a result, only the lowest possible friction occurs between the cellular wheel and the wall of a chamber of the metering device which closely surrounds it.

As mentioned, the cell wheel is arranged in the metering device in a chamber which surrounds the cellular wheel at its flat sides and at its periphery with walls. In this case, a feed opening is provided in the cell wheel surrounding the circumference of its wall, which is connected to the container for receiving the admixing flocculant zuzumischenden. This feed opening is formed shorter than this in the axial direction of the cellular wheel and thereby arranged approximately symmetrically to a median plane of the vertically arranged cellular wheel above this. In this way, the flocculation aid conveyed through the feed opening to the cellular wheel is essentially placed centrally on the cellular wheel and thus does not lead to undesired frictional effects on the end faces of the cellular wheel.

Advantageously, the wall surrounding the cell wheel at its circumference is provided in the direction of rotation of the cell wheel downstream of the feed opening with a bulge widening in the radial direction. This leads in a certain way A way to loosen the flocculant so that it is easier to promote and dose.

It is provided that the metering device is flowed through in the region of the bulge of the compressed air to which the flocculant is added. The compressed air thus added with flocculant is then injected into a liquid as described above, wherein according to the invention, this liquid, (compressed) air and flocculants containing mixture to be supplied to a mixing chamber in which then the admixed flocculant is dissolved in the liquid.

In an embodiment according to the invention, a rotor-stator arrangement is provided in this mixing chamber, in which the stator has a multiplicity of perforated disks arranged parallel to one another and to be flowed through by the liquid in the axial direction. Between such perforated disks, a helical or propeller-shaped section of the rotor is then arranged, which ensures the continuous conveyance of the liquid-flocculant mixture.

In this constellation, it has proven to be very effective to make the diameter of the holes smaller in the flow direction of successive perforated discs smaller. This causes a particularly fast and effective dissolution of the flocculant in the liquid.

It should be mentioned here that in the device as described here, an air separator is still provided, through which the air with which the flocculant is introduced into the liquid is deposited.

Figur 1

eine erfindungsgemäße Vorrichtung in perspektivischer Gesamtdarstellung;

Figur 2

einen Schnitt durch einen Behälter zur Aufnahme des zuzumischenden Flockungshilfsmittels;

Figur 3

eine perspektivische Explosionsdarstellung einer in der Vorrichtung vorhandenen Wiegevorrichtung;

Figur 4

eine perspektivische Darstellung einer teilweise demontierten Dosiervorrichtung;

Figur 5

ein Teil der erfindungsgemäßen Dosiervorrichtung in perspektivi- scher Ansicht;

Figur 6

das Teil gemäß Figur 5 in einer Schnittansicht;

Figur 7

Schnitt durch ein Bauteil der Vorrichtung zur Injektion von Flockungshilfsmittel in eine Flüssigkeit;

Figur 8

einen Schnitt durch eine Rotor-Stator-Vorrichtung der erfindungsge- mäßen Vorrichtung;

Figur 9

eine perspektivische Ansicht einer Lochscheibe aus der Rotor- Stator-Vorrichtung gemäß Figur 8.

Further advantages and features of the invention will become apparent from the following description of an embodiment. It shows

FIG. 1

an apparatus according to the invention in an overall perspective view;

FIG. 2

a section through a container for receiving the zukumischenden flocculant aid;

FIG. 3

an exploded perspective view of a present in the device weighing device;

FIG. 4

a perspective view of a partially dismantled metering device;

FIG. 5

a part of the metering device according to the invention in a perspective view;

FIG. 6

the part according to FIG. 5 in a sectional view;

FIG. 7

Section through a component of the device for injecting flocculant in a liquid;

FIG. 8

a section through a rotor-stator device of the inventive device;

FIG. 9

a perspective view of a perforated disc from the rotor-stator device according to FIG. 8 ,

FIG. 1 shows the structure of a device according to the invention in a compact, movable embodiment.

On a base platform 1, which is provided with a plurality of wheels 2, the device according to the invention is mounted and also in a separate cabinet 3, the control provided for this purpose.

The device according to the invention is supplied via a pipe extension 4 or a corresponding funnel, a liquid-soluble flocculation aid, which is received in a container 5.

From this container 5, this flocculant, which is powdery or granular and which is in particular a polymer, then taken down via a metering element 6 and mixed with a liquid. This flocculant added liquid is passed through a rotor-stator device 7 in which the flocculant is dissolved in the liquid. The liquid with the dissolved flocculant is then discharged through a nozzle 8 and a line, not shown, from the device and added in a sewage treatment plant with up to about 5% solids added sludge water. The dissolved flocculants associate with these solids, resulting in their precipitation.

The container 5 is in the FIG. 2 shown in section. One recognizes a cylindrical wall 9, which is closed at its upper end by a cover 10. In this cover 10, a chute 11 is integrated, through which the powdery or granular liquid-soluble flocculation aid can reach the interior 12 of the container 5. The chute 11 is closed at its lower end by a pivot cover 13 which is actuated via a Kipphebelmechanik 14 by a pneumatic cylinder 15.

In the interior 12 of the container 5 is the lid 10 with the chute 11 against a funnel-shaped bottom 16, which ends in a central outlet opening 17.

Furthermore, in the wall 9 of the container 5 is still a compressed air valve 18 is provided, whose function will be explained below.

The Indian FIG. 2 shown container 5 is mounted on a weighing platform, as shown in the FIG. 3 is shown by way of example. The bottom 19 of the container 5 sits on a support plate 20 which has an opening 21 in the middle, over which the failure opening 17 comes to rest. The support plate 20 is supported by stand 22 spaced from a weighing plate 23 which rests on a balance base 24. In this case, the weighing plate 23 is guided by guide brackets 25. The path of the weighing pan 23 is received by a weighing element 26 and transmitted to the controller in the control cabinet 3.

Again, the function is explained below.

In the space which is created between the support plate 20 and the weighing plate 23 by the stator 22, a metering element 6 is arranged, which in the FIG. 4 shown in more detail in partial exploded view.

In this metering element, a substantially horizontally arranged shaft 28 is driven via a controllable via the controller 3 motor 27, on which a vertically driven cellular wheel 29 sits rotationally. This cellular wheel 29 has over its circumference a plurality of axially parallel extending cells 30 which are open to the end faces 31 of the cellular wheel 29. In this case, the cells form teeth between each other, which end in lines 32 on the cellular wheel outer circumference.

The bucket 29 rotates in a chamber 33, which is designed in the present example as a replaceable element and in the FIGS. 5 and 6 shown in more detail. This chamber 33 is closed by a cover 34, which has a connection 35 through which compressed air can emerge from the chamber 33, which, as described below, flows through the chamber 33 parallel to the axis of the cell wheel 29.

The chamber 33 is, as I said, in the FIGS. 5 and 6 shown in more detail. One recognizes in the FIG. 5 the chamber 33 in its usual operating position, in which the axis of the rotating in their cellular wheel 29 is oriented substantially horizontally.

In the example shown here, the cell wheel will rotate in one direction of rotation in a clockwise direction.

In the direction of rotation, shortly after the uppermost vertex of the chamber, a feed opening 37 is introduced into the wall 36, which essentially passes through the wall 36 in a vertical direction and ends in the interior of the chamber 33. The axial extent 38 of this feed opening 37 is, as in the FIG. 6 can be seen, shorter than the distance 39 between the side walls 40 of the chamber 33, which are parallel to the end faces 31 of the cellular wheel 29. This causes matter falling through the supply port 37 to not fall between the side walls 40 of the chamber 33 and the End faces 31 of the cellular wheel 29 sets, which would lead to a blockage or deceleration of the rotating cellular wheel.

In the FIG. 5 Furthermore, it can be seen that the wall 36 of the chamber 33 surrounding the cell wheel at the circumference of the chamber 33 of the feed opening 37 has a bulge 41 extending in the radial direction downstream in the direction of rotation of the cell wheel. This bulge results in gravity falling out of the cells 30 of the cell wheel 29 and can not clamp between the lines 32 on the circumference of the cell wheel 29 and the wall 36.

Rather, in this bulge 41 supplied through the terminal 42 compressed air is passed axially parallel through the cells 30 of the cellular wheel 29 and led out through the terminal 35 from the chamber 33. This compressed air takes with the metering supplied with powder or granular flocculant and carries it to a in the FIG. 7 illustrated component.

In this device, the enriched with the flocculant auxiliary compressed air is injected through an injector 43 in a liquid flowing through a conduit 44 (in the FIG. 7 to the right). The angle of inclination between the injector 43 and the liquid-flowed line 44 is preferably on the order of 45 ° or smaller in order to achieve a good mixing.

In particular, in this injection, the powdery or granular flocculation aid is introduced into the conduit 44 so that each individual particle is individually surrounded by liquid and moistened therewith. Clumping of the flocculant is effectively prevented in this way.

With the conduit 44, the liquid flocculation aid-air mixture is fed to the mixing device 7, which contains a rotor-stator device and in the FIG. 8 is shown.

The in the FIG. 8 illustrated rotor-stator device is traversed by a right there in the tangential direction of the inflow opening 44 substantially in the axial direction to an outlet opening lying in the axial direction 46 at the axially opposite end.

The liquid flowing through the rotor-stator device alternately passes through fixed perforated disks 47 and through spaces in which it is conveyed by propellers or screw sections 48 in the axial direction. The propeller or screw sections sit on a common drive shaft 49 by a in the FIG. 1 shown motor 50 is set in rotation.

The individual perforated disks 47, one of which in the FIG. 9 is shown, in its radially central region on a plurality of axially parallel aligned holes. These holes become increasingly narrower in subsequent perforated discs, so that in this way a resolution of flocculants in the fluid flowing through is achieved.

The device described so far is now operated as follows:

The container 5 is filled after opening the pivot cover 13 through the chute 11 with a predetermined amount of powdered or granular flocculant. Thereafter, the pivot cover 13 is closed again via the pneumatic cylinder 15 and in the interior 12 of the container 5, a pressure of about 5 bar is built up via the compressed air valve 18.

The present in the container 5 flocculant now trickles through the opening 17 through the opening 21 in the support plate 20 through into the opening 37 of the mixing chamber 33 and falls there on the feeder 29. This rotates and doses the flocculant, which discharged by the compressed air which is passed through the port 42 and the port 35 through the chamber 33 in the axial direction. The mixture exiting the chamber 33 thus consists of flocculants and air.

The compressed air has about a pressure of 5 bar, as it is also applied in the container 5. Within the mixing chamber 33 so no pressure differences must be overcome.

This enriched with flocculant auxiliary air is then as described to the device according to FIG. 7 passed and injected there into the liquid flowing through the conduit 44.

This inflowing liquid is detected in the amount before injecting the compressed air / flocculant auxiliary mixture by a (not shown) flow meter and this amount is reported to the controller, which is present in the control box 3.

The amount of flocculation aid admixed by the metering element 6 of the liquid flowing through is detected by the weight loss which the filled container 5 experiences over time and which is detected by the weighing element 26 in the carriage base 24. - It can be assumed that the weight of the elements detected by the weighing element 26 remains constant except for the flocculation aid present in the interior 12 of the container 5.

Depending on the weight loss and the determined flow rate, the controller 3 then determines, in particular, the speed of the motor 27 so as to effect a proportional decrease of the flocculation aid, so that it can be assumed that the liquid which reaches the mixing device 7 always is added with a predetermined amount of flocculants.

The dissolution of this flocculant in the liquid then takes place as described in the rotor-stator device 7, wherein this parallel connected and an air separator is provided to the originating from the interior 12 of the container 3 and the air used for the injection of compressed air from the Flocculants added to separate liquid.

This flocculant added liquid is then added as described above in a sewage treatment plant with sludge water added to solids for further purification.

It should also be mentioned that in the rotor-stator device 7 it is also possible to additionally supply a flocculation aid present in liquid form. It should be noted that powdery or granular flocculants in conjunction with such liquid flocculants have particularly favorable, since "diversified" flocculation.

The admixing of such liquid traded flocculants with the rotor-stator device described can be carried out both in a first passage for the dissolution of powdery and granular flocculant in liquid, as well as in a subsequent once again circulating the existing liquid through the rotor stator Device 7.

The advantage of the device described here lies in particular in the possibility of a quasi-continuous production of fluid mixed with flocculants and in their particular operational safety.

Claims (11)

1. Apparatus for metered admixture of a powdered or granular liquid-soluble flocculating agent in a liquid, wherein this device has a compressed air pipe (43) which transports the flocculating agent to the liquid and opens into a conduit (44) through which the liquid flows, characterised in that a mixing device (7) with a rotor-stator arrangement is disposed downstream of the conduit in the flow direction thereof.
2. Apparatus as claimed in Claim 1, characterised in that the stator of the rotor-stator arrangement has a plurality of perforated discs for a through flow in the axial direction.
3. Apparatus as claimed in Claim 2, characterised in that the diameter of the holes of in the flow direction successive perforated discs (45) decreases.
4. Apparatus as claimed in Claim 1, characterised in that an air separator is provided on the mixing device (7).
5. Apparatus as claimed in Claim 1, characterised in that the compressed air pipe is connected by way of a controllable metering element (6) to a container (5) for receiving the flocculating agent to be added, and that the conduit through which the liquid flows has a flow meter, wherein a weighing device (26) is provided which determines the weight of the flocculating agent dispensed by the metering element (6) and wherein the flow meter and the weighing device (6) supply signals and are connected to a control unit (3) which acts as a function of these signals on the metering element to which it is functionally connected.
6. Apparatus as claimed in Claim 5, characterised in that the weighing device (26) is coupled to the container (5) and supplies signals as a function of the decrease in weight thereof.
7. Apparatus as claimed in Claim 5, characterised in that the metering element (6) has a compartmentalised wheel (29) which can be driven controllably in rotation.
8. Apparatus as claimed in Claim 7, characterised in that the compartmentalised wheel (29) has a plurality of compartments (30) substantially ending in lines on the circumference.
9. Apparatus as claimed in Claim 7, characterised in that the compartmentalised wheel (29) is disposed in the metering element (6) in a chamber (33) which surrounds the compartmentalised wheel (29) on its flat faces (31) and its circumference with walls (40, 36), wherein in the wall (36) surrounding the compartmentalised wheel (29) on the circumference thereof a feed opening (37) is provided which is shorter in the axial direction of the compartmentalised wheel (29).
10. Apparatus as claimed in Claim 9, characterised in that the wall (36) surrounding the compartmentalised wheel (29) on the circumference thereof has a convexity expanded in the radial direction which is disposed downstream of the feed opening (37) in the direction of rotation of the compartmentalised wheel (29).
11. Apparatus as claimed in Claim 10, characterised in that compressed air flows through the metering element (6) in the axial direction in the region of the convexity (41).

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