Device and Method for Generating Gas Bubbles in a Liquid

Abstract

A device for generating gas bubbles in a liquid in a container includes a rotatable gas-permeable hollow shaft arranged in a container, gassing discs arranged on the hollow shaft and spacers arranged between the gassing discs, gassing discs and spacers being arranged alternately on the hollow shaft in gas-tight contact with one another, a feed line for a compressed gas into the interior of the shaft, having a centered opening (O) for receiving said shaft and at least two chambers, said chambers being equally spaced around said centered opening, where said centered opening and said chambers at least partially overlap, where the centered opening and the chambers are in communication with one another at least in the overlap region, so that the compressed gas can flow from shaft into in each case a chamber of the spacer and enter the gassing discs from the chamber of the spacer.

Claims

1. A device for generating gas bubbles in a liquid in a container, comprising: at least one rotatable gas-permeable hollow shaft arranged in at least one container, gassing discs arranged on the at least one hollow shaft and spacers arranged between the gassing discs, wherein gassing discs and spacers are arranged alternately on the hollow shaft in gas-tight contact with one another, at least one supply line for at least one compressed gas into the interior of the at least one rotatable hollow shaft, wherein each of the spacers has at least one centered opening for receiving the hollow shaft and at least two chambers, wherein the at least two chambers are equally spaced around the centered opening, wherein the centered opening and the at least two chambers at least partially overlap, wherein the centered opening and the at least two chambers are in open communication with one another at least in the overlap region, so that the compressed gas can flow from the hollow shaft into in each case at least one of the chambers of the spacer and can enter the gassing discs from the at least one chamber of the spacer.

2. The device according to claim 1, wherein the at least one hollow shaft is arranged horizontally in the at least one container.

3. The device according to claim 1, wherein the gassing discs are circular in shape and are arranged vertically to the hollow shaft on the at least one hollow shaft.

4. The device according to claim 1, wherein the spacers are circular in shape.

5. The device according to claim 1, wherein the spacer comprises at least three circular chambers, said at least three chambers being equally spaced around the centered opening.

6. The device according to claim 1, wherein the geometries, of the chambers of the spacer are the same in each case.

7. The device according to claim 1, wherein the at least one spacer with an external diameter dA.sub.outside has, on at least one of its circular sides, a shoulder with a diameter dA.sub.shoulder, where dA.sub.shoulder is smaller than dA.sub.outside.

8. The device according to claim 7, wherein the at least one shoulder of the spacer serves to receive the gassing disc.

9. The device according to claim 7, wherein the gassing disc is in the form of a ring with an inner circumference with an inner diameter dB.sub.inside and an outer circumference with an outer diameter dB.sub.outside, the inner diameter dB.sub.inside of the gassing disc corresponding to the diameter dA.sub.shoulder of the shoulder of the spacer with a tolerance.

10. The device according to claim 1, wherein the gassing disc has gas openings uniformly distributed along the inner circumference.

11. The device according to claim 1, wherein the gassing discs are ceramic gassing discs with an average pore size between 0.05 μm and 20 μm.

12. The device according to claim 1, wherein between 2 and 100 gassing discs and spacers are arranged on the at least one rotatable hollow shaft.

13. The device according to claim 1, wherein the at least one supply line for the compressed gas into the hollow shaft and at least one drive for rotating the hollow shaft are provided at one shaft end piece or at different shaft end pieces.

14. A method for generating gas bubbles in a liquid in a container using at least one device according to claim 1, said method comprising: introducing a compressed gas into at least one supply line, wherein the compressed gas is introduced directly into the supply line without liquid carrier; introducing the compressed gas into the interior of the at least one horizontally arranged rotatable hollow shaft, wherein the at least one hollow shaft rotates at a rotational speed between 50 and 400 rpm, and introducing the compressed gas into the liquid via the spacers and gassing discs arranged vertically on the horizontal rotating hollow shaft, producing gas bubbles.

15. The method according to claim 14, wherein the bubbles generated in the liquid have a bubble size between 1 μm and 200 μm.

16. The device according to claim 1, wherein the geometries of the diameters of the chambers of the spacer are the same in each case.

17. The device according to claim 1, wherein the gassing discs are ceramic gassing discs with an average pore size between 2 μm and 5 μm.

18. The device according to claim 1, wherein between 15 and 30 gassing discs and spacers are arranged on the at least one rotatable hollow shaft.

19. The method according to claim 14, wherein the at least one hollow shaft rotates at a rotational speed between 180 and 220 rpm.

20. The method according to claim 14, wherein the bubbles generated in the liquid have a bubble size between 45 μm and 50 μm.

Description

[0070] The invention is explained in more detail below with reference to the figures in the drawings by means of an example. Show it:

[0071] FIG. 1A a first schematic side view of a device for generating gas bubbles in a liquid according to an embodiment,

[0072] FIG. 1B a second schematic side view of a device for generating gas bubbles in a liquid according to an embodiment,

[0073] FIG. 2A a first schematic side view of a spacer used in the device for generating gas bubbles in a liquid;

[0074] FIG. 2B a second schematic view of a spacer used in the device for generating gas bubbles in a liquid;

[0075] FIG. 2C a third schematic view of a spacer used in the device for generating gas bubbles in a liquid;

[0076] FIG. 3A a schematic view of a shaft end piece of the hollow shaft with air supply and drive;

[0077] FIG. 3B a schematic view of a first variant of a drive arrangement for the device (slide-in version);

[0078] FIG. 3C a schematic view of a second variant of a drive arrangement for the device (drop-in version);

[0079] FIG. 4 a schematic side view of a plant for the purification of a liquid comprising a device for generating gas bubbles.

[0080] A general structure of a first embodiment of the device for generating gas bubbles according to the invention is shown in FIG. 1A.

[0081] The side view of FIG. 1A comprises a device 1 with a supply line 2 for the compressed gas, a hollow shaft 3 and with gassing discs 4 and spacers 5 alternately arranged on the hollow shaft 3. The compressed gas is fed through the hollow shaft 3 into the spacers 5 and further into the gassing discs 4.

[0082] In the embodiment shown in FIG. 1A, several circular gassing discs made of a ceramic material are arranged on the hollow shaft. The ceramic discs are made of aluminum oxide, have an outer diameter of 152 mm and an inner diameter of 25.5 mm. The membrane surface is between 0.036 m.sup.2 and the pore size of the gassing discs is in the range of 2 μm. The gas is introduced from the hollow shaft 3 into a cavity of the ceramic disk 4 and penetrates from the interior of the cavity through the pores of the ceramic material into the liquid to be cleaned, which is provided around and above the hollow shaft provided with the gassing disks, under formation of micro-bubbles with a bubble size of approx. 45 to 50 μm. The gassing discs 4 are arranged on the hollow shaft by means of stainless steel or plastic fastenings. The distance between the gassing discs corresponds to the thickness of the spacers 5.

[0083] Together with the gas supply line 2, a suitable device 6 for moving the hollow shaft is provided on the same shaft end piece. This device may be in the form of a motor which transmits the corresponding rotational movement to the hollow shaft via several gears.

[0084] The embodiment shown in FIG. 1B illustrates the construction of the hollow shaft 3 and the arrangement of the spacers 5 and the gassing discs 4 on the hollow shaft 3.

[0085] Gassing discs 4 and spacers 5 are arranged alternately in a gas-tight contact on the hollow shaft 3. The gas-tight contact is caused by the specific design of the spacer 5 (see also FIG. 2A-C). The gas enters the hollow shaft 3 via the supply line 2, is fed from there into the spacer 5 and from there into the gassing discs. In this way the ceramic gassing discs 4 are supplied with gas and an even bubble production in the medium to be gassed is achieved. The hollow shaft 3 can be made of metallic or non-metallic materials.

[0086] The spacers are shown in more detail in FIGS. 2A to 2C. Each of the spacers 5 has a centered opening (O) with a diameter dO for receiving the hollow shaft and at least two or three, in particular circular chambers (K1, K2, K3) each with a diameter dK1, dK2, dK3. In the case of the embodiment shown in FIGS. 2A-C, the diameters dK1, dK2, dK3 and dO are each 35 mm. However, these values are variable and depend on the overall size of the fixture.

[0087] The radii of the centered opening (O) and the radii of the two or three circular chambers (K1, K2, K3) overlap or intersect, so that the centered opening (O) and the two or three chambers (K1, K2, K3) are in open communication with each other at least in the overlap area 5b. The open communication of the centered opening and the chambers allows the compressed gas to flow from the hollow shaft into at least one of the chambers K1, K2, K3 of the spacer 5 in each case. The gas can then continue to enter the gassing discs 4 from one of the chambers K1, K2, K3 of the spacer 5.

[0088] In the embodiments of FIGS. 2A-2C, the one spacer 5 with an outer diameter dA.sub.outside has on its circular sides a (centering) shoulder 5a with a diameter dA.sub.shoulder, where dA.sub.shoulder is smaller than dA.sub.outside.

[0089] The centering shoulder 5a of the spacer is used to receive or make contact with the gassing disc 4. The gas-tight contact between the spacer 5 and the gassing disc 4 is achieved by placing the gassing disc 4 on the shoulder 5a of the spacer 5 and sealing between the gassing disc and the spacer (on the outer radius of the spacer).

[0090] The gassing disc 4 is in the form of a ring with an inner circumference with an inner diameter dB.sub.inside and an outer circumference with an outer diameter dB.sub.outside, where the inner diameter dB.sub.inside of the gassing disc corresponds to the diameter dA.sub.shoulder of the (centering) shoulder of the spacer (see FIG. 2C).

[0091] Along the inner circumference of the gassing disc, evenly distributed gas openings 4a are provided (see FIG. 2C).

[0092] The introduction of gas from a chamber K1, K2, K3 of the spacer into a gassing disc 4 results from the fact that a gassing disc 4 is arranged between two spacers 5. The gas is conducted from the gas-filled chamber of the spacer into the intermediate space between two spacers, the intermediate space being filled by a gassing disc, and further from this intermediate space via suitable gas supply or gas access openings in the gassing disc into the gassing disc.

[0093] FIG. 3A shows a shaft end piece in which air supply 2 and drive 6 are combined. The drive 6 for the rotary movement of the shaft can be directly on the shaft, but can also be driven by various mechanical force redirections. For example: Bevel gear, 90° reduction gear. This means that the drive 6 of the shaft can find its position in the medium to be gassed on the one hand, but also outside the medium to be gassed on the other. The drive 6 can be positioned over all known types of drive (e.g.: electric/hydraulic/air pressure).

[0094] Shaft 3 is supported in at least two positions, different types of rolling bearings can be used, e.g: ball bearing, deep groove ball bearing, needle bearing, roller bearing, plain bearing.

[0095] Gas supply 2 into the rotating shaft must be via at least one seal. This can be positioned inside or outside the medium to be gassed.

[0096] An O-ring seals the shaft end piece to the first gassing disc or the first spacer. The O-ring groove can be recessed into the shaft end piece.

[0097] FIG. 3B shows a first variant (slide-in version) for the arrangement of the drive 6 (motor) of device 1. The drive 6 is located outside the tank or vessel in which fixture 1 is immersed and used. The transmission is effected via a rotary union on the wall of the tank.

[0098] FIG. 3C shows a second version (drop-in version) for the arrangement of drive 6 (motor) of device 1, where drive 6 is located inside the tank or vessel in which device 1 is immersed and used. This version allows an easy integration of the device into existing systems, as no holes have to be drilled through the tank wall.

[0099] FIG. 4, in turn, shows a schematic diagram of a plant 20 for the purification of a liquid, in particular water, which comprises at least one of the above-mentioned embodiments of a device for generating gas bubbles. The side view of the plant 20 in FIG. 4 shows a flocculation unit 10 into which the water to be purified and the flocculant are introduced. After mixing the water to be purified with the flocculant, for example by using a stirrer, the mixture from the flocculation unit 10 can be introduced via a partition into a further, separate section or container 20, in which at least one hollow shaft 20a with four gassing discs is provided in accordance with the embodiment of FIG. 1.

[0100] In the present experimental procedure, dirty water is used that has been mixed with humic substances. All organic substances in the wastewater are simulated by humic substances, which are also produced in nature by normal biological decomposition. To flocculate the humic substances contained in the water, trivalent ions containing iron- and aluminium-containing substances are particularly suitable as precipitants. In this case a FeCl.sub.3 solution is used as flocculant. After adding the flocculant using a static mixer, the humic acids contained in the waste water are flocculated in flocculation unit 10 by the flocculant FeCl.sub.3.

[0101] The dirty water mixed with FeCl.sub.3 is then introduced from the flocculation unit 10 into the container 20 containing the gassing device consisting of a hollow shaft with four gassing discs with a volume flow of 400-700 l/h.

[0102] Air is injected via the gassing device 20a according to the invention in container 20, whereby micro-bubbles are formed directly in the water mixed with flocculant. The gassing discs or gassing plates of the gassing device rotate in the same direction at a rotational speed of 180 rpm, resulting in a phase shift of 180°. The micro-bubbles formed combine with the flocs to form floc-air bubble agglomerates, which are then introduced into the downstream flotation cell 30. Due to the attachment of the microbubbles to the flocculated organic components, the correspondingly formed agglomerates rise in the flotation cell towards the surface of the liquid in flotation cell 30 and form a solid layer on the water surface, which is separated mechanically, for example by using scrapers. The water thus pre-cleaned is drawn off by a suitable pump through the filtration unit 40 in the flotation cell 30 and is available as cleaned water for further treatment, such as further desalination processes. In order to prevent fouling of the surface of the filtration unit 40, air can be directed directly onto the surface of the filtration unit 40 via hoses or pipes provided with holes, which causes a mechanical removal of deposits on the surface of the filtration unit 40.