EP0198073B1 - Device for introducing a gas into a liquid - Google Patents

Abstract

A device is used to continuously introduce a gas into a liquid, in a flotation, deinking unit or the like. The liquid comes out of an endless ring passage (6) which is completly free of internal obstacles such as limiting walls or the like, and flows after absorbing the gas into a radial diffuser (14), wherefrom the gas bubble-enriched liquid comes out and flows into the treatment container of the plant. For this reason, a single gasification device centrally arranged close to the bottom of the container is sufficient for circular cross-section treatment bath. A swirling flow may be obtained by a deflection in the area of the diffuser or of the first chamber of liquid in the ring passage.

Description

The invention relates to a device for continuously introducing a gas, in particular air, into a liquid, in particular water, for water activation, water treatment, flotation, deink plants or the like, with a liquid-shaped distributor device designed as an essentially circular annular gap with a horizontally running central plane , at least one gas outlet opening including feed line and a diffuser with the same horizontally extending central plane downstream of the distributor device, the gas outlet openings opening above and below the annular gap each being annular openings of an air chamber.

DE-OS 3015788 discloses a gassing device in the course of a flotation device. The actual device consists of a cuboid housing with a flat nozzle, a series of air inlet openings and a flat diffuser with flat boundary surfaces. For each flotation device, several gassing devices are used, the swirl being imparted to the liquid of the flotation chamber, which is circular in cross section, by inclining the gassing devices. The flat nozzle shape was primarily chosen to counteract the blockage of fibers and the like previously observed in nozzles.

However, it has been shown in practice that the hoped-for improvement in the form of a reduced risk of constipation does not occur. If a blockage occurs near a lateral boundary wall, an impenetrable plug builds up very quickly up to this wall, which will not be washed away by itself in the further course of operation. Instead, the flat nozzle grows slowly and loses its favorable mode of operation, because z. B. the diffuser is too wide for the then still free passage in the area of the liquid nozzle. Another major disadvantage of the known gassing devices, however, is the relatively expensive production. The flat bodies required for the device must be produced in narrow tolerances on planing and grinding machines, which experience has shown to be less economical than e.g. B. the shape by turning, since each cutting stroke is connected to an idling return stroke.

FR-A-2 397870 teaches to feed a first fluid into a second by means of a jet device, one of the fluids entering the center of the device and drawing in the other fluid. The fluid mixture then flows towards the periphery of the device. The device itself has two plates arranged at a distance from one another, between which the fluid mixture moves. In the device, the risk of blockage is already reduced, but not to a sufficient extent, by using an annular nozzle formed from the two plates.

It is therefore an object of the invention to design the liquid nozzle in a simple and economical manner in a device of the type mentioned at the outset in such a way that a risk of clogging is largely avoided.

This object is achieved by a generic device with the features listed in the characterizing part of claim 1.

In the device according to the invention, the annular gap of the distributor device forms the outlet of a nozzle-like chamber, the cross section of which narrows monotonously on the way from a feed line to the annular gap. Furthermore, the diffuser has two opposing boundary surfaces on either side of the liquid emerging from the annular gap. the distance between them on a current path from the inside to the outside, taking into account the growing circumference of the current path with increasing diameter, is selected so that the circular diffuser with a conical cross section has an overall widening that that of a circular diffuser with an opening angle of 2 ° to Corresponds to 6 °.

The device according to the invention is therefore equipped with an endless ring nozzle in which there is no side boundary in the form of an end wall or the like. After an initially small blockage, a bridge to a fixed part cannot form at any point in the annular gap, which bridge can then no longer be removed by the current flow. Rather, in the device according to the invention, it can be expected that a blockage will dissolve immediately before it leads to a noticeable impairment of the flow conditions. The production is achieved by assembling turned parts, which can usually be manufactured particularly economically, even on machines. Finally, a single supply for the liquid and for the gas is required in order to supply the device, which is anyway to be installed in circular flotation plants, with operating materials.

A gassing device has become known from European patent application 35243, in which the liquid jet is directed onto an acute rotating body and is thereby deflected approximately horizontally. During the deflection or on the way from the exit of the liquid from the nozzle to the tip of the rotating body, the gas is mixed with the liquid, the rotating body together with the expanded air supply forming a curved diffuser in which the flow is slowed down and its internal pressure increases becomes. As a result, the gas transfer into the liquid is poor; there is also an unfavorable ratio at the liquid nozzle between the outer surface and thus the gas entry surface to the volume flow of the liquid, which also prevents an abundant gas transfer into the liquid. In this known device, the mixture of liquid and gas is abge radially give, but otherwise there are no similarities to the device according to the invention.

In the case of a radial diffuser, as used in the invention, there is a natural widening on the current path from the inside to the outside, irrespective of the upper and lower boundary surfaces, which results from the increase in diameter and the associated increase in the peripheral surface. It has been shown that a diffuser of this type only achieves the desired conversion of speed into pressure with the lowest possible losses if the overall expansion corresponds to that of a diffuser with a circular cross section and with an opening angle of 2 ° to 6 °. In view of this requirement, a wide variety of configurations for the upper and lower boundary surfaces can arise. In the case of small amounts of liquid per unit of time, that is to say with a small circumferential length of the annular gap, the clear width between the boundary surfaces narrows from the inside to the outside, although of course there is still an overall expansion of the size mentioned. In the case of annular gaps, the circumferential surface of which is considerably larger in order to cope with a larger quantity of liquid per unit of time, with a more or less the same running length of the diffuser, there may first be a tapering, then a constant and finally an expanding configuration between the two boundary surfaces.

A typical device according to the invention is designed so that the annular gap has a clear width of 5 mm, the exit velocity of the liquid from the annular gap is about 12-13 m / s and a sufficient outflow velocity at the outlet of the diffuser at a liquid height of about 1 , 5 to 2 m is present in the treatment pool. The latter parameter has proven to be favorable for flotations and treatment tanks of all kinds. With a clear width of 5 mm for the annular gap there is sufficient security against clogging of the annular gap.

The device according to the invention is usually arranged in the center of a basin with a circular cross-section near the bottom. If there is to be a slight swirl flow within the basin, low-resistance spacer webs can be arranged between the boundary surfaces of the diffuser, which are slightly curved and produce the swirl to a sufficient extent. With a correspondingly full design of the spacer webs, they can be used, with or without curvature, to supply the air chamber below with air from the air chamber above, a pipe leading to the air chamber above, the free end of which is located above the liquid level in the assigned treatment tank. In deviation from this, the lower air chamber can also be supplied from the upper air chamber by separate pipelines or by connecting lines outside the device.

The supply of one air chamber from the other air chamber provided with a supply line can also take place directly via the air outlet openings. To create these transition areas, the ring nozzle is then closed at predetermined points by spacers or fastening pieces, behind which a liquid-free area is formed in the flow shadow, which is used for the overflow of the gas from one chamber to the other. As a rule, three spacers or fasteners evenly distributed around the circumference are sufficient to create these overflow areas. If necessary, the width can be varied in the circumferential direction of the annular gap.

The supply of the liquid to the annular gap should be designed with particular care since, with the correct shape, considerable savings in running operating costs can be achieved. Particularly advantageous conditions result when the annular gap forms the outlet of a chamber, to the top of which the feed line for the liquid is connected, and whose cross section narrows monotonously on the way from the feed line to the annular gap. This is equivalent to the fact that the liquid is continuously accelerated, since the respective effective flow cross-section from the inlet to the annular gap becomes smaller without a jump and without widening to a previous level. The annular gap finally forms the narrowest point from which the liquid emerges at high speed.

Instead of one-sided supply of the liquid from below or from above, it is also possible to supply the liquid from both sides from below and from above. The annular gap then lies in the center of a channel which is formed by the two liquid inlets. The last section of each inlet up to the annular gap can again be designed as a monotonic narrowing, so that the liquid is accelerated uniformly and emerges from the annular gap at high speed. With this type of arrangement of the liquid supply, of course, the same pressure must prevail in both supply lines so that one liquid column can be “supported” on the other.

Before the liquid enters the diffuser, it absorbs extreme amounts of gas due to the drop in pressure at this point, which leads to an increase in the volume of the liquid-gas mixture. Accordingly, the inlet of the diffuser is designed to be significantly larger in cross section than the annular gap. As a rule, the suction force of the liquid emerging from the annular gap is sufficient to automatically suck up the air chambers that have filled up through the openings after the rest periods.

• Fig. 1 eine Querschnittsansicht durch eine Vorrichtung gemäß der Erfindung für kleinere und mittlere Flüssigkeitsdurchsatzmengen,
• Fig. 2 eine Ansicht gemäß Fig. 1 eines weiteren Ausführungsbeispiels der Erfindung für eine sehr große Durchsatzmenge;
• Fig. 3 den Ausschnitt einer Schnittansicht gemäß der Linie 111-111 in der Fig. 2,
• Fig. 4 eine Ansicht gemäß Fig. 1 eines weiteren Ausführungsbeispiels der Erfindung mit einer Flüssigkeitszuleitung auf der Oberseite und auf der Unterseite und
• Fig. 5 eine Querschnittsansicht entlang der Linie V-V in der Fig. 4 als Ausschnitt zur Verdeutlichung der Bildung von Gasübertrittsbereichen von einer Kammer in die andere.

Exemplary embodiments of the invention which are illustrated in the drawing are explained in more detail below; show in the drawing:

• 1 is a cross-sectional view through a device according to the invention for small and medium liquid throughputs,
• FIG. 2 shows a view according to FIG. 1 of a further exemplary embodiment of the invention for a very large throughput;
• 3 shows the detail of a sectional view along the line 111-111 in FIG. 2,
• Fig. 4 is a view of FIG. 1 of another embodiment of the invention with a liquid supply on the top and on the bottom and
• Fig. 5 is a cross-sectional view taken along line VV in Fig. 4 as a detail to illustrate the formation of gas transfer areas from one chamber to the other.

The device according to the invention shown in FIG. 1 essentially consists of a housing 1, formed from an upper housing part 2 and a lower housing part 3. In the center of the upper housing part 2 there is an inlet 4 for a liquid which is to be enriched with a gas, for example for a flotation plant. The inlet 4 opens into a chamber 5, the lower end of the inlet 4 already being part of the cross-sectional narrowing down the chamber 5. The end of the chamber 5 is formed by an annular gap 6, to which the liquid flows with a constant increase in speed. In this case, a tip 7 in the middle of a bottom 21 of the chamber 5, which is designed as an annular trough, is involved in the uniform distribution of the flow over the circumferential, endless annular gap 6.

The liquid emerging from the annular gap 6 flows past openings 8 into a diffuser 14, the openings 8 forming the outlet of air chambers 9 and 10, which are supplied with gas, in the present case with air, via supply lines 11 and 12, respectively. The liquid jet takes up gas in the area of the openings 8, and the resulting increase in volume of the mixture now present is taken into account by a correspondingly enlarged inlet of the diffuser 14.

The boundary surfaces 17 and 18 of the diffuser 14 formed by two disks 15 and 16 run towards each other slightly towards the outside, but overall there is an expansion for the medium flowing through the diffuser 14, namely due to the expansion in the circumferential direction with increasing distance from the annular gap 6. Evenly distributed around the circumference of the diffuser 14 are spacers 19, in the immediate vicinity of which a continuous screw bolt 20 connects the two housing parts 2 and 3 to one another. The screw bolt 20 and in its flow shadow the spacer 19 hinder the outlet of the diffuser at three points, but this impairment of the flow can be tolerated without any significant losses.

The supply line 12 to the lower air chamber 10 must of course project to a level which is above the liquid level in the treatment tank (not shown), in the center of which near the bottom the device according to FIG. 1 is inserted. Otherwise, the container would run empty in the rest periods via the opening 8, the lower air chamber 10 and the feed line 12. It can happen that the radial liquid jet emerging from the annular gap 6 does not completely empty the U-shaped section of the feed line 12. For this reason, a valve 22 is provided at the deepest point of the U-shaped section, which is opened briefly when the system is started up and, when the air has already been drawn in, discharges the remaining liquid accumulated here through the supply line 12. Thereafter, the valve 22 can be closed again and need not be taken into account for the rest of the operation.

The bottom 21 of the chamber 5 is interchangeably inserted into the lower housing part 3, whereby in particular the width of the annular gap 6 and the shape of the chamber bottom vary slightly and can be adapted to different tasks. If e.g. B. the tip 7 tends to accumulate fiber or other contaminants from the liquid and so there is a risk of clogging of the annular gap 6, the bottom of the chamber 5 can be slightly curved like a watch glass with the lowest point in the center. A variation of the annular gap 6 is possible by changing the thickness of the bottom 21. If the diffuser 14 is also to be changed, spacers 19 of different thicknesses can be used and the bolts 20 can be tightened to a different span length.

The exemplary embodiment shown in FIG. 2 is intended for a fairly large liquid throughput, that is to say for a larger system, while the exemplary embodiment according to FIG. 1 is reserved for a substantially smaller system with a much lower liquid throughput. Corresponding differences are also present in the outer dimensions, the exact dimensions being based on the liquid throughput quantity and on the selected outlet speed in the annular gap. Otherwise, both devices are very similar, although the higher throughput also results in deviations, which are described in particularly great detail below.

The upper housing part 30 and a lower housing part 31 cooperate so that an annular gap 33 is formed between them, which is fed from an annular chamber 32. The annular chamber 32 is approximately toroidal, with a continuously narrowing acceleration path radially outward, which has its narrowest point in the annular gap 33. The annular chamber 32 is fed by a plurality of feed lines, preferably located opposite one another in pairs, which are indicated by dashed lines in FIG. Deviating from this, there can of course be a central supply of the type of chamber 5 according to FIG.

The air chambers 34, in turn, are located above and below the diffuser 43 Exit in the form of openings 35 are located immediately above and below the exit of the annular gap 33. All of the air is supplied to the upper chamber 34 via a plurality of supply lines 36, of which only a single supply line 36 is shown in FIG. 2 for the sake of clarity. From here, a connecting line 37 leads to the lower air chamber 34. The connecting line 37 extends approximately to the wall of the treatment container in which the device according to FIG. 2 is accommodated. This is indicated by dashed lines within the connecting line 37. The connecting line 37 is also available in several copies in order to ensure an adequate supply of the lower air chamber 34 with gas.

The diffuser 43 is in turn formed from two rings 38 and 39, which are angled at their outer ends upwards or downwards. In this exemplary embodiment, a plurality of spacer webs 42, which are evenly distributed around the circumference, are provided between their boundary surfaces 40 and 41, which are designed to be particularly low-resistance and keep the housing halves 30 and 31 and the associated housing parts at a distance from one another.

In the case of a thicker-bellied embodiment, the spacer webs 42 can be hollow and, in addition to the connecting line 37 or in its place, can ensure the passage of air from the upper air chamber 34 into the lower air chamber 34. In addition or independently of this, with the aid of the spacer webs 42, a swirl of the flow leaving the diffuser 43 can be generated, namely by a slight curvature of all spacer webs 42 in the same direction in the same direction. A cross-sectional view through one of the spacer webs 42 producing a swirl is shown in FIG.

The clear width of the annular gap 33 can be adjusted with the aid of disks 45, which lie between the two housing parts 30 and 31 or between the lower housing part 31 and a further housing part 44, which forms the bottom of the lower air chamber 34. A change of the diffuser 43 with respect to its profile or with respect to the distance of its boundary surfaces 40 and 41 is also possible by changing the rings 38 and 39 or by changing the height of the spacer webs 42. In this way, adjustments to different uses can be made relatively quickly.

After a standstill period, both air chambers 34 and the feed line 36 are filled with liquid up to the level within the container in which the device according to FIG. 2 is used. As soon as liquid emerges from the annular gap 33 at high speed in the radial direction when a pump starts up, a suction effect occurs in the region of the openings 35, in which further liquid is initially mixed into the liquid jet. The liquid level in the feed line 36 and in all further feed lines gradually drops until the upper air chamber 34 is filled with gas. From this point in time, gas is already metered into the liquid from the upper air chamber 34 via the associated opening 35, while liquid still passes through the lower air chamber 34 into the liquid jet. If the connecting lines 37 are also completely emptied, a certain residual liquid remains on the bottom of the lower air chamber 34, which is no longer automatically removed, but does not further interfere with ongoing operation.

The exemplary embodiment shown in FIGS. 2 and 3 can also be produced almost exclusively from turned parts, which also applies to the exemplary embodiment according to FIG. 1. The manufacturing costs are correspondingly low, which indirectly decrease even further because there is a relatively central supply of the operating resources to the device, which makes the usual distribution along the circumference of a treatment basin unnecessary.

The actual device can be made of steel, plastic or an alloy, the choice of material primarily depending on the aggressiveness of the medium to be treated. The flow velocities are in any case chosen from the design in such a way that damage by cavitation or the like is virtually impossible.

The exit velocity of the liquid from the annular gap can be artificially increased by superimposing a swirl on the radial flow direction, which is generated within the chamber 5 or within the annular chamber 32. As a result, the pressure within the liquid jet drops further, so that even more gas passes into the liquid. The swirl flow is generated by guide bodies in the acceleration sections, which, with the appropriate design, have an almost loss-free effect.

FIG. 4 shows a further exemplary embodiment of a device according to the invention. The function is similar to the exemplary embodiment according to FIG. 1, only the supply of the liquid and the air supply to a lower air chamber 60 are designed differently. With regard to the diffuser, there are therefore no reference numerals in FIG. 4, since the description thereof would represent a repetition.

The upper part 52 and the lower part 53 of a housing 51 are each provided with an upper inlet 54 and a lower inlet 55, which together form a channel 50 in the vicinity of an annular gap 56. The channel 50 is monotonically decreasing in diameter towards the annular gap 56, so that the liquid flowing in with the same pressure in the inlets 54 and 55 is accelerated in this area. It then enters the diffuser at high speed from the annular gap 56 past the openings 58.

The upper housing part 52 is provided with a feed line 61 for the gas, in particular for air. Located at three points (FIG. 5) of the annular gap 56 spacers 57, which at these points hinder the free escape of the liquid from the annular gap 56. Liquid-free areas 62 form in the flow shadow of these spacers 57 and ensure the overflow of air from the upper air chamber 59 into the lower air chamber 60. In Figure 5, the flow is indicated schematically by dashed lines.

The exemplary embodiment according to FIG. 4 is used in cases in which a feed for the liquid from below to the device is possible without difficulty. Of course, the exemplary embodiment according to FIG. 1 can also be used in this case, which is then installed in an upside-down position. The appropriate routing or attachment of the supply lines 11 and 12 for the air can be selected accordingly by any person skilled in the art.

The principle of overflow from one air chamber to the other described in FIG. 5 with the aid of transition areas in the flow shadow of the liquid flow can of course also be combined with the exemplary embodiment according to FIG. 1 and according to FIG. 2; this type of air supply to the air chamber remote from the feed line is therefore not tied to the liquid supply on both sides.

The liquid emerging from the respective annular gap 6, 33 or 56 normally emerges in a uniformly flowing manner without strong turbulence. With particularly wide annular gaps, however, turbulence can increasingly occur, which apparently promotes the absorption of gas immediately thereafter. If necessary, the diffuser inlet must then be slightly widened, that is to say converted into a type of catch constellation. Excellent gassing results have also been achieved with such devices according to the invention.

Claims (14)

1. A device for continuously introducing a gas, in particular air, into a liquid, in particular water, for water activation and purification, flotation, deinking units or the like, comprising a liquid distribution device substantially in the form of an annular gap (6; 33; 56) having horizontally extending centre planes, at least one gas discharge opening (8; 35; 58) including respective feed conduits, and a diffuser (14, 43) having the same horizontally extending centre planes disposed downstream the distribution device, said gas discharge openings being circular ports (8; 35; 58) of an air chamber (9, 10; 34; 59, 60) opening upstream and downstream of the annular gap, characterized in that the annular gap (6, 33; 56) of the distribution device forms the discharge opening of a nozzle- type chamber (5, 32; 50) the cross-section of which is continuously reduced between a feed conduit and an annular gap (6; 33; 56), and that the diffuser (14,43) comprises two mutually oppositely disposed boundary surfaces (17; 18; 40,41) at respective sides of the liquid which issues from the annular gap (6,33,56), and the mutual spacing of which, over a flow path from the interior outwardly, having regard to the enlargement due to the increasing peripheral area with increasing diameter, is so selected that the overall enlargement corresponds to that of a diffuser which is circular at the base and conical in cross-section, with an aperture angle of from 2° to 6°.

2. A device according to claim 1, characterized in that low-resistance spacer arms (42) are disposed between the boundary surfaces (40, 41) of the diffuser (43).

3. A device according to either of claims 1 or 2, characterized in that each air chamber (9, 10; 34; 59, 60) covers at least a part of the back side of the associated boundary surface (17, 18; 40, 41), and that the spacer arms are hollow for connecting the two air chambers.

4. A device according to either of claims 2 or 3, characterized in that the spacer arms (42) are slightly curved to produce a swirl effect.

5. A device according to either of claims 1 to 4, characterized in that there is provided a feed conduit (36) to the upper air chamber (34) and that the two air chambers (34) are in interchange relationship by way of a connecting conduit (37).

6. A device according to either of claims 1 to 5, characterized in that the annular gap (33) is a component of an annular chamber (32) having a plurality of uniformly peripherally distributed feed flows.

7. A device according to either of claims 1 to 5, characterized in that to the top or underside of chamber (5) is connected the liquid feed conduit (4).

8. A device according to claim 7, characterized in that the bottom (21) of the chamber (25) is shaped to provide an annular trough.

9. A device according to either of claims 7 or 8, characterized in that the bottom (21) of the chamber (5), including the lower portion defining the annular gap (6), is releasably fixed in place.

10. A device according to either of claims 7 to 9, characterized in that disposed within the chamber (5) are guide bodies which impart a swirl to the flow along the centre line.

11. A device according to claim 1, characterized in that the boundary surfaces of the diffuser are held at a spacing relative to each other by means of a plurality of connecting conduits between the upper and lower air chambers.

12. A device according to either of claims 1 to 5, characterized in that the annular gap (56) of the distribution device forms the discharge of a passage (54) consisting of two chambers, to which respective feed conduits (54, 55) for the liquid are connected at the top side and at the underside.

13. A device according to claim 12, characterized in that the passage (50) reduces uniformly on each feed flow side to the annular gap (56).

14. A device according to either of claims 1, 6,7 7 or 12, characterized in that the annular gap (56) of chamber (50) is closed at predetermined locations by spacer portions (57) or fixing portions, that an air feed conduit (61) goes only to the one air chamber (59), and that the regions of the annular openings (58), which are disposed in the flow shadow of the portions (57), serve as flow transfer locations for the air to flow into the other chamber (60).

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