CH619154A5 - Device for admixing a liquid with gas. - Google Patents

Description

The invention relates to a device for the gassing of liquid, with a completely immersed in the liquid, driven, double-sided bladed rotor, the gas on the side facing the liquid level via a dip tube, and on the opposite side of the rotor draws liquid from the vicinity of the rotor and both Media dispersed at the rotor outlet, and with a screen which is arranged in the area near the rotor and surrounds the immersion tube and runs at least approximately perpendicularly, the outside diameter of which is substantially larger than the outside diameter of the rotor.

Circulation aerators should circulate water, wastewater, sewage sludge, liquid manure and substrates with a high content of organic substances, i.e. liquid media with dissolved and suspended substances of various compositions, and enrich them with air or other gases in order to achieve physical, chemical and / or biochemical in the liquid flow Trigger and carry out reactions, e.g. Foaming colloidal and suspended substances, neutralizing alkalis by gassing with flue gas, decarbonising acidic water, oxidizing and thus degrading the organic substances present in the liquid media through exothermic biochemical reactions.

The circulation aerators previously carried out normally consist of a blunt-ended suction tube immersed in the liquid, below which the ventilation rotor is located with a gap to the end of the suction tube. This is connected to a drive motor mounted above the intake pipe by a shaft. The ventilation rotor normally consists of a plate with gas blades on the top and liquid blades on the bottom. The blades should on the one hand circulate the liquid medium and on the other hand should introduce gas of various compositions, often air.

Conventionally, the circulation aerators were conceived as water jet pumps with an annular suction gap formed between the end of the suction pipe and the wheel disc of the rotor. The water flow radially outwardly conveyed by the rotating rotor creates a negative pressure as it flows past the suction gap; as a result, the gas located in the intake pipe is drawn in and distributed in the liquid flow.

In contrast to the surface ventilation that is common in many designs and works in the area of the liquid level, a device of the type described at the outset is also known, the circulating elements of which work below the surface of the liquid body, vigorously circulate it without lifting and thereby introduce gas (DE-OS 1782485 ). Here, between the rotor hub and the spiral rotor blades, floating skin-like, perpendicularly arranged deflection webs are provided, which are limited to the area near the hub and are strongly curved in their free edge. These webs on the rear side of the respective leading blade in the radial direction are deliberately kept much longer than on the front of the trailing blade. The rotor parts, which extend perpendicular to the axis, are not arranged rotationally symmetrically, their projection5

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The surface is therefore approximately star-shaped with slender spikes curved against the direction of rotation, the roots of which extend radially inwards almost to the rotor hub. In comparison to the clear cross section of the air intake pipe, the content of such a projection surface is very small.

For this reason and because of their jagged contours, these star-shaped structures cannot function as wheel disk bodies. In the intake manifold, a vacuum is to be recorded on the gas side, the amount of which corresponds at least to the immersion depth of the intake tube and which is opposed by a hydraulic vacuum built up by the rotor through the liquid delivery. In the case of the radially deeply cut star of the deflection webs, the phase boundary between gas and liquid always flickers unstably in the area of the rotation plane. If the hydraulic negative pressure currently prevails, gas can be locally torn through and individual large gas bubbles enter the liquid. However, if the hydraulic vacuum drops below the required mean value, liquid strikes back locally or momentarily through the wheel spider into the intake manifold, which means that little gas is temporarily drawn in. This probably explains the very restless run observed in practice with the known device with coarse-bubble gas entry and accordingly poor gas transfer.

In another known device (FR-PS No. 1050396) there is neither a large screen arranged perpendicular to the axis nor a rotor which is bladed on both sides for gas and for liquid. Rather, the sucked-in gas is pressed into the liquid solely by the only gas-promoting blading, as a result of which much drive energy is lost, since the liquid pressure prevailing at the location of the rotor must be overcome by the gas-promoting impeller, which is associated with low throughput and the specific one Oxygen input greatly reduces. The agitator blades, which are arranged below the gas-conveying blading at a distance therefrom, furthermore do not produce a concentrated, rapid flow, as would be required for dispersing fine bubbles with turbulent circulation; they only provide a more or less even distribution of saturated liquid in the container.

The same applies to another known device (CH-PS No. 466818), in which a small collar or flange is arranged at the lower end of the immersion tube, which carries a bladed diffuser on its outer circumference. Collar and diffuser are part of the gas pump. The diffuser surrounding the rotor delays the flow. A cylinder is arranged at a short radial distance around the diffuser, which forces the flow into a vertical direction as a deflecting screen and prevents radial expansion of the gas bubbles. Low-energy gas entry cannot be achieved with such a structure.

Another known construction has a double arrangement of screens (DE-OS 2229833), whereby the flow ejected by the rotor is rigidly channeled. The two screens, which are arranged at a distance from one another, form a radial diffuser in which the flow cross section for a radially running flow increases from the inside outwards in proportion to the distance from the center. If the distance between the shields also increases from the inside to the outside, a strong radial deceleration of the flow is inevitable for reasons of continuity. The bladder coalescence is promoted by such a very damaging flow slowdown; a separation and mutual removal of the gas bubbles dispersed by the rotor cannot be achieved. As a result, the flow at the outer edge between the two screens emerges relatively slowly and in a coarse bubble, the buoyancy forces of the coarse bubbles outweighing the mass forces of the flowing liquid. The coarse bubbles rising steeply to the liquid 'level form a strong one

Veil that tugs the liquid. With short contact times and only relatively small contact areas, the achievable gas transfer is correspondingly poor.

The invention has for its object to eliminate all these shortcomings and to provide a device of the type described above, which ensures reliable, effective operation over long periods of time with a simple construction, inexpensive manufacture and convenient assembly and maintenance and enables a fine-bubble gas input.

The invention solves this problem in that the rotor, in the manner of a double-flow, radially flowed pump or blower wheel, has a closed wheel disc body carrying conveying blades on both opposite sides, the diameter of which is larger than the inside diameter of the dip tube, and that the radial inner area of the screen reaches axially and radially without interruption up to the top blades of the rotor without touching them.

It is an important finding that the type of contour and the area of the projection surface of the wheel disc body are also decisive for the bubble size of the gas that is introduced. This connection is realized constructively, in that, according to the invention, a closed wheel disc body is provided on the rotor, the projection surface of which completely covers the gas-producing cross section at the end of the intake manifold. In the entire gas-carrying diameter range of the rotor, the phase boundary is stabilized by a closed wall and at the same time moved closer to the edge of the intake manifold, because not only is there a radial separation of the phases, but the wall is radially constant so far that it lies out over the A continuously high hydraulic vacuum can build up over the entire circumference of the wheel disc body. The gas to be entered is therefore forced to pass through a narrow slot along a large circumferential distance into the liquid, so that fine gas bubbles are inevitable.

The screen should prevent the strong tendency of small bubbles to coalesce and rise to coarse bubbles. For this purpose, according to the invention, it is designed axially and radially in such a way that the dispersion ejected by the rotor flows under it in a relatively thin flow layer at high speed and with corresponding turbulence. The bubbles cannot coalesce due to the high turbulence, which on the contrary causes a further bubble breakdown with constant renewal of the phase boundary, which favors the gas transfer. Because the large screen extends uninterruptedly into the suction-effective rotor area, it also prevents the bubbles from rising. They are held down and forcibly distributed over a large circumferential distance, which increases their mutual distance. The extensive bubble dispersion and separation largely prevents the possibility of coalescing with neighboring bubbles. Therefore, the slowing flow can keep the fine bubbles in suspension, which would not be possible with larger bubbles. The fine bubble dispersion is now evenly distributed in the pelvic contents. The total drive power actually consumed per unit of quantity of gas is considerably lower than according to the prior art.

An important embodiment of the invention consists in that on the liquid inlet side all parts of the rotor are exposed to the liquid completely free, that is to say there are no internals such as guide surfaces, feed channels, auxiliary rotors or the like. They would only obstruct the flow and form attachment surfaces for the fixing of fiber material or the like in coarsely contaminated liquids, which would result in a further cross-sectional narrowing and a slowdown in flow. The flow must remain as low as possible, because rapid circulation with a rapid flow of liquid, especially at the rotor outlet, with the lowest possible rotor drive power is essential for achieving one

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optimal gas input per unit of drive energy of great importance. The faster the liquid emerges from the rotor, the more gas is drawn in through the injector effect; and the faster the container liquid is circulated, the greater the diffusion gradient for the gas or for a gas component, for example atmospheric oxygen, at the liquid volumes reaching the area of the gassing device, i.e. the more intense e.g. Oxygen absorbed from the air. Both internals on the suction side and unnecessary double baffles or the like on the rotor outlet side would only hinder the suction and circulating flow. It is therefore expedient to leave it to itself in its course. Accordingly, there can only be a single screen, which only limits the rotor outlet flow upwards, through the distributor action of which the free-flowing liquid / gas mixture is conveyed radially far into the container contents.

Since the screen of the device according to the invention can be very large, gas-rich liquid can accumulate above it in a so-called dead water area, which liquid would be separated from the rest of the pool and would have no effect on fumigation. In order to run this so-called dead water roller with as little loss as possible, to guide it back into the main pool flow and to mix this part of the volume evenly with the entire contents of the container, flow-optimized, rotationally symmetrical deflection surfaces can be provided in the area of the liquid surface and in the transition area to the screen on the gassing device. The dead water roller is constantly driven by a bubble curtain that rises on the perimeter of the screen. The kinetic energy thus carried into the liquid is largely retained at the deflection points, so that a noticeable centrifugal flow with well-fumigated liquid forms above the screen. This flows relatively quickly to the edge of the screen and mixes with the main flow emerging below. The flow energy transferred to the liquid through the bubble curtain is thus used to a large extent for circulating the rest of the pool contents. At the same time you get the important advantage

that the immersion depth of the recirculation gasifier can be increased without increasing the power consumption compared to less flow-efficient guidance of the recirculation streams. Tests have shown that the specific gas input has a pronounced optimum if the outer diameter of the screen is dimensioned so that the speed of the flow velocity at the edge of the screen is less than the immersion depth.

Not only is the liquid roller formed directly around the recirculation gas generator above the screen with low losses, but also the main flow in the basin, to which a large number of measures can contribute. During the circulation by means of a submerged gassing device, two rotationally symmetrical liquid wafers flowing in opposite directions can be pushed one above the other from the rotor. Through special coordination of the dimensioning of the tank depth in relation to the basin shape - seen in vertical section - and immersion depth, there are significantly smaller losses than conventional.

The gassing rotor draws liquid from the deep layers of the container on its underside and guides it past the radial outer edge of the wheel disc body at high speed. There the gas-enriched liquid moved by the rotor radially escapes at high speed. The gas bubbles contained in the mixture have the tendency to force this initially plate-like radial flow upwards inside the rotor like a screen or bowl, which would shorten the contact time of the gas with the liquid and cause segregation (bubble coalescence). However, the aim is to achieve the longest possible contact time in order to stabilize the fine-bubble mixture, as well as a low position and a flat course of the plate flow, so that layers as deep as possible are captured by the circulation movement, stabilized in the radial direction and released with a large underwater throw. This can e.g. Realize that on the gas-side, axial end faces of the blades, at least in the region protruding radially beyond the wheel disc body, guide surfaces are provided which run perpendicular to the axis.

The underside of the rotor, designed for the largest possible volume, gives the outlet flow an undesirably steep direction without any other measures, which would accelerate the gas lift. This exit flow can e.g. are deflected into the horizontal by guide surfaces and stabilized in this direction. The change in direction of the plate flow causes additional vortices, which reduce the gas bubbles sucked in by the liquid flow and thus give them a size which is more favorable for transport and gas transfer. The extension of the common flow path of liquid and gas bubbles and the larger surface area of the gas volume increase the contact time and area between the two media. This also significantly increases the utilization of the active components in the sucked-in gas, such as oxygen in the air, carbon dioxide in the flue gas or ozone in the ozonized air and at the sea.

So that the blade channels do not become clogged in the case of coarsely contaminated liquids, such as liquid manure or sewage sludge, the guide surfaces in the circumferential direction can expediently be shorter than the distance between adjacent blades. In such regionally open blade channels with continuous longitudinal openings, coarse mechanical contaminants are also carried away. Since the main part of the outlet flow, which is already enriched with fine gas bubbles, is located on the front side of the blades in the direction of rotation, it is advantageous if the guide surfaces extend forward in the direction of rotation of the rotor. In order to prevent mechanically dense components such as straws, fibers, shredded paper and the like from accumulating on an edge of the guide surfaces which protrudes in the circumferential direction, their free contour, which is at the front in the direction of rotation, is advantageously designed in such a way that it is drawn at any contour point with a drawn there Center beam encloses an acute angle. Contaminants then always slide radially outwards.

The redirection of the flow initially rising obliquely within the rotor into the horizontal and the entrainment of the fine gas bubbles is promoted even more if the guide surfaces are preferably crescent-shaped and are extended radially outward beyond the blade tips. In addition to the plate flow already mentioned, these guide surface extensions produce a further, very thin, gas-bubble-free, umbrella-like or plate-like, faster flow, which overlies the basic flow enriched with gas bubbles mentioned above. This faster, upper, thin cover or screen flow can only break through the gas bubbles if their rising force is greater than the horizontal movement impulses of the bubble-free screen flow located above. The latter also sucks in liquid located above the rotor and thus extends the contact time between the two media.

Depending on the type of liquid, foam is inevitably generated in the case of fine-bubble gas entry. Suspended substances can be floated out, which can be embedded in foam ceilings of great thickness that extend beyond the drive motor. The foam moisture drawn into the interior of the drive motor by the cooling fan and the dirt particles carried along can cause mechanical and electrical damage in the motor. It can even happen that flotated substances accumulate on the floats carrying the aeration device, so that they drag the entire system down and cause mechanical or electrical consequential damage.

An attempt has already been made to place the foam in the pool together with the air to be drawn in, which is sucked into the dip tube

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stop attributed. Sooner or later this leads to a blockage of the intake cross section. Otherwise, this method fails anyway from the outset in cases where a gas, e.g. Carbon dioxide or other exhaust air into which liquid is to be introduced and the dip tube must be closed to the outside at all points. In contrast, in a preferred embodiment of the invention, a foam downpipe is arranged around the immersion tube, which forms a return duct for foam and / or floating substances that is separate from the gas suction channel of the immersion tube.

The most favorable height of the foam falling edge is to be determined empirically on a case-by-case basis. In any case, it will be above the liquid level, preferably about 10 to 25 cm above it. The foam blanket can grow about the same amount beyond the height of the foam falling edge; if you want to limit them to a thickness of about 25 to 50 cm depending on the type of foam, an axially adjustable ring can be provided for this purpose at the upper end of the foam downpipe. can be adjusted axially by at least three radially fixed fastening and guide screws and a corresponding number of helically extending elongated holes in the ring by a rotary movement in the manner of a nut.

In some applications, the foaming behavior of the liquid fluctuates; then it is important to be able to adjust the height of the foam falling edge to the respective foam development. The foam blanket must not grow too high beyond the foam trap edge, because otherwise bridging can easily occur within the annular cross section of the foam trap. The displaceability of the foam falling edge by means of an axially movable ring can only be used in those cases in which the liquid does not form excessively dirt and crusts. If the liquid to be fumigated is more prone to deposits and crust formation on the walls, it is better to keep the excess of the foam about the same order of magnitude as the radial dimension of the annular foam fall cross-section, by moving the entire ventilation device according to the increase or decrease the foam layer raises or lowers. For this purpose, a rope pulley and a rope winch can be arranged on the float, with which the device suspended on a rope can be moved up and down.

The channel enclosed by the foam downpipe advantageously opens out into an annular slot at the top of the rotor surrounding the suction opening of the immersion tube within its suction area. If the annular gap remaining between the ring slot and the suction opening has a sufficient radial width, a considerable suction power of the rotor can be built up.

A configuration is also advantageous, according to which the outer diameter of the ring slot is approximately as large as or smaller than the rotor outer diameter.

So that no blockages can form in this cross-sectional constriction and a pre-twist of the air flow can form here, the channel is expediently kept free of spacers, built-in parts and the like in its last section up to the opening ring slot. Keeping the ring slot clean and the formation of a pre-twist is e.g. favored by clearing fingers extending axially upward into the ring slot on the upper side of the wheel disc body of the rotor.

The spacing components in the foam downpipe can be designed in such a way that they promote a swirling of the air. In order to avoid the conventionally necessary hanging of sheets to catch coarser dirt parts or swimming pool parts in the foam downpipe, it can be provided that the spacers are each designed as sheets that extend uninterruptedly over the axial length of the support.

In the case of a ventilation device with a foam downpipe, a radially standing bubble distribution screen is arranged around the suction opening and the ring slot. If it is held by the foam downpipe, the ring slot can be kept free of built-in parts. The transition from the dip tube or from the foam downpipe to the screen can also be provided with deflection surfaces which are aerodynamically favorable in axial section.

The deflection surface near the surface is advantageously arranged below the liquid surface in such a way that its height does not change when the height of the foam falling edge is adjusted. If the entire ventilation device is intended to be raised or lowered in order to adapt the height of the foam falling edge to the foam layer thickness, these deflection surfaces near the surface are best attached directly to the float.

To facilitate manufacturing, transport, assembly and maintenance, e.g. in the event of severe contamination, it is expedient if the foam downpipe holding the screen is designed as a separate part which can be displaced axially over the immersion tube and is thus easy to disassemble.

Exemplary embodiments of the invention are shown in the drawing, namely:

1 shows an overview cross section through a liquid container with a gassing device according to the invention,

2 shows an enlarged cross section through a gassing device similar to FIG. 1,

3 shows a further enlarged, vertical longitudinal section through the lower part of a gassing device according to the invention,

4 is an axial plan view of the top of the rotor of the device of FIG. 3,

5 is a vertical sectional view of a further embodiment of a gassing device according to the invention,

6 shows a gas-side axial view of a rotor for a gassing device according to the invention,

Fig. 7 is a schematic cut-out side view of a floating gassing device according to the invention with lowering and raising gassing unit and Fig. 8 is a plan view of the arrangement of Fig. 7. A liquid substrate 1, e.g. Liquid manure is filled in the example of FIG. 1 in the aerodynamically designed, preferably round container 2. An approximately square container with chamfered or rounded corners would also be suitable. A ventilation device 4 with dip tube 5, rotor 6 and drive motor 7 is arranged in the center of the container 2 via a bridge 3 formed from steel girders. The container 2 can be approximately semi-square in cross-section, so that the diameter D is approximately twice as large as the filling height H during operation. Depending on the type of substrate 1, a foam blanket or a floating blanket 9 (FIG. 2) can be formed on the liquid level 8. The immersion depth t of the aeration device 4 in the liquid is approximately a quarter of the filling height H. This arrangement - H ~ D / 2 and t «H / 4 - results in particularly favorable flow conditions, so that it is possible to circulate with the least amount of energy optimally maintained. In addition, displacement bodies 10 and 11 are arranged in the corner areas on the floor and near the game gel, which cause a low-loss flow deflection. Furthermore, a rotationally symmetrical displacement body 12 of conical or hyperboloidal shape is arranged on the floor below the rotor 6 in the middle of the basin in order to promote a deflection of a centripetal, horizontal liquid movement into an upward flow with as little loss as possible. In the basin 2 of the cross section shown, therefore, essentially two rotationally symmetrical liquid rollers form, which are pushed by the rotor 6, namely a base roller (flow arrows 13), which is constantly combined with an oxygen-rich, near-surface, centrifugal liquid flow (flow arrows 13a), and a smaller top roller (flow arrows 14), which is excited by rising bubbles of introduced gas.

With the arrangement shown, a particularly high input performance of air and thus of oxygen into the s is achieved

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Substrate 1 by circulating and mixing the entire pool contents with as little loss as possible in such a way that the liquid regions which are particularly easily accessible with gas bubbles are constantly brought into contact with zones which are less easily accessible. During the aeration time, the local oxygen gradient within the substrate 1 is kept very low, so that partial saturation does not occur locally and another strong deficit of oxygen elsewhere. The saturation time for the entire pool content is shortened by circulating, mixing and equalizing the oxygen content, i.e. the required drive power per unit of quantity of oxygen introduced and dissolved is lower in comparison with a less good, less lossy mixture and circulation of the pool contents according to the prior art. The basin design and the arrangement of the ventilation device 4 within the container 2 is therefore crucial for the technological performance.

The ventilation device 4 shown enlarged in FIGS. 2 to 4 is attached to a platform 15 via spacers 16, which in turn can be part of a bridge or floating structure similar to FIGS. 7 and 8. The device 4 is immersed under the mirror 8 of a liquid in a container (not shown here). The aerator 4 consists essentially of the immersion tube 5, which is fastened to the platform 15 by means of a flange 5a, the drive motor 7 with a drive shaft 17 passing through the immersion tube 5 and the rotor 6 attached at its end and lying below the immersion tube 5 Dip tube 5 communicates at the top with the air above the platform 15 and ends at the bottom with as little axial play as possible on an air-side blading of the rotor 6. The end of the dip tube 5 facing the latter therefore forms a suction opening 18.

The shaft 17 can be mounted in the motor 7 largely free of vibrations. Optionally or additionally, a support bearing 17a can be provided near the lower end of the shaft 17, which makes lateral deflections of the shaft 17 impossible.

The rotor 6 consists of a wheel disc body 19 with aerodynamically curved top and bottom and from both sides of the wheel disc body 19 attached blades, of which the blades 20 on the top of the wheel disc body 19, the air sucked in above the platform 15 and the blades 21 on the underside of the Pump the wheel disc body 19 liquid (substrate 1). The number of blades 20 on the top is greater than that of blades 21 on the bottom. As far as possible, the top and bottom blades 20, 21 are arranged congruently. The liquid blades 21 and those air or gas blades 20, which are congruent with the former, extend beyond the outer diameter dr of the wheel disc body 19 to a diameter da, whereby the outer boundary of the rotor 6 is formed (FIG. 3).

The rotor 6, which is rotated by the drive motor 7, sucks in air from the atmosphere through the suction opening 18 and the immersion tube 5 (flow arrows 22); at the same time, the rotor 6 sucks in liquid 1 axially from the depth of the basin 2 (flow arrows 23). Both media, air and liquid, are dispersed at the rotor outlet and ejected radially outwards (flow arrows 24). A broad screen 26 is arranged around the rotor 6, on the underside of which the turbulent flow 24 initially flows, the air / liquid mixture being dispersed in fine bubbles and an intensive phase boundary exchange taking place due to the turbulence.

The screen 26 initially prevents the dispersed air bubbles from rising and keeps them in turbulent contact with the centrifugally ejected liquid over a long distance. In the radial area of the screen 26, the liquid ejected by the rotor 6 still has a high flow velocity and turbulence, which prevents bubble coalescence. The air entered remains in fine bubbles and with little thickness in the flow liquid; the gas lift is therefore very low.

However, the screen 26 must not be too large and must not extend into areas in which the liquid flow slows down below certain minimum speed values; otherwise there would be coarse bubble formation and a backflow of liquid on the edge of the screen 26, which would not only have an unfavorable effect on the entire circulating movement in the basin 2, but would also severely impair the transition of the bubbles into the liquid. In addition, in the event of a backflow and the formation of coarse bubbles, the gas introduced by the rotor 6 would be present under the screen 26 with such great thickness that a lift would arise which could raise the floating ventilation devices 4 and impair their positional stability.

In order to counter these deficiencies, such a design is provided that the speed level of the screen outlet flow is somewhat less than the immersion depth t of the rotor 6. As a result, the input drive energy is used in a particularly favorable manner, and the liquid within the area of the screen 26 certainly flows sufficiently quickly to prevent the formation of coarse bubbles. In combination with the flow turbulence within the substrate 1, the correctly dimensioned screen offers the further advantage of an intensive exchange of phase boundaries with the fine-bubble dispersed air. The rapid renewal of the phase boundary favors an oxygen transition by preventing rapid gas saturation in the immediately adjacent boundary layer of the liquid, which would otherwise slow down further oxygen absorption. This turbulence is still promoted or at least maintained despite the flow slowing if discontinuities 27 (FIG. 3), e.g. are arranged in the form of small bolts, knobs or the like, the height of which is determined by the bubble diameter.

An ascending bubble curtain (flow arrows 28) is formed on the outer circumference of the bladder screen 26 due to the gas lift. This upward flow 28 causes above the screen 26 a flow roller surrounding the ventilation device 4 in a ring (arrows 14). By installing flow-promoting deflection surfaces 29 (FIGS. 2 and 3) below the water surface 8 and at the transition area in the screen 26, the flow losses of this liquid roller 14 are kept particularly low, the kinetic energy carried through the bubble curtain 28 into the substrate 1 largely preserved.

Depending on the type of liquid 1 to be gassed, the rising bubble curtain 28 forms more or less foam. To limit the thickness of such a foam blanket 9 (FIG. 2), a foam downpipe 30 can be arranged concentrically around the immersion tube 5 for reliable return of the foam into the substrate 1, which foam tube together with the immersion tube 5 forms an annular foam downpipe 31 and which via a the annular slot 32 surrounding the suction opening 18 opens in the immediately effective area on the upper side of the rotor 6. An annular gap 33 with a certain minimum radial width bf located between the annular slot 32 and the suction opening 18 ensures a sufficient suction height for the air sucked in through the immersion tube. The outer diameter ds of the ring slot 32 is dimensioned such that it extends only into areas in which a suction effect of the rotor 6 is still present. The opening 18 is also dimensioned in such a way

that in its area the negative pressure generated by the aerator 4 is greater than the counter pressure, which corresponds to the immersion depth t of the rotor 6.

The arrangement shown prevents a liquid level from developing in the foam downpipe 30, since any water and foam that may be transferred immediately through the rotor 6

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be dissipated. The radial width bs of the ring slot 32 is designed for unimpeded passage of the foam. The annular slot 32 extends between the suction opening 18 or the annular gap 33 at the lower end of the immersion tube 5 and the screen 26 at the lower end of the foam downpipe 30, which therefore forms the holder for the bladder screen 26.

The upper end of the immersion tube 5 extends beyond the water level 8 and forms a foam trap edge 34 for the foam 9. The head height Hk of the foam trap edge 34 is so adaptable to the thickness Hs of the foam cover that a certain protrusion Hü of the foam 9 over the edge 34 prevents the formation of foam bridges in the annular foam fall channel 31. In the exemplary embodiment according to FIG. 2, a foam fall ring 35 is provided for this operational adjustment of the height Hk of the foam fall edge 34, which is axially movable by rotational movement relative to the foam fall pipe 30, for example by means of stud bolts 35a of one part in oblique or helical elongated holes 35b of the other part intervention.

In the case of liquids and foam blankets which are very heavily contaminated by suspended substances and which introduce a heavy amount of dirt into the foam downpipe 30 (arrows 36), the ring 35 and thus the overhang Hü of the foam downflow edge 34 could no longer be easily adjusted after a certain period of operation and contamination, if the sliding surfaces have become clogged with dirt and make an adjustment movement difficult. For these cases, the construction shown in FIGS. 7 and 8 is provided, which will be explained further below.

For maintenance, only an axial fastening of the foam downpipe 30 has to be removed and the rotor 6 has to be removed. Thereafter, the foam downpipe 30 can be removed axially from the dip tube 5 if necessary.

On the inside of the foam downpipe 30 are radially spaced sheets 37 welded, which end radially inward in front of the dip tube 5. Only at their upper and lower ends are the spacer plates 37 stabilized against one another by stiffening rings 38, 38a. The upper stiffening ring 38 can be provided with clamping screws, by means of which the foam downpipe 30 and the screen 26 can be fixed axially and in the circumferential direction in the correct axial position relative to the immersion tube 5 and the annular gap 33.

In view of the axial displaceability of the foam case construction on the immersion tube 5, the outer diameter ds of the ring slot 32, which is equal to the inner diameter of the bladder shield 36, is also somewhat larger than the outer diameter of the immersion tube 5. The spacers 37 are continuous sheets that pass through to the incident Foam does not offer any unnecessary contact surfaces on which dirt that has been carried along could adhere. The sheets 37 can be connected in a helical manner so that they impart a pre-twist to the air sucked through the foam downpipe 30 in the sense of the direction of rotation of the rotor 6.

The last section 39, located in front of the ring slot 32, of the foam downpipe 30, in which the annular cross section of the foam drop channel 31 tapers to the cross section of the ring slot 32, is kept free of internals. Due to this narrowing of the cross-section and the associated acceleration of flow (arrows 36a), a swirl that has already been initiated is amplified without any installations in this swirl anteroom 39 impairing it.

The formation of such an advance is further favored by clearing fingers 40 which extend axially from the rotor 6 into the annular slot 32 and keep it clear at all times. These are arranged on the outer circumference of the wheel disc body 19 of the rotor 6 such that they are on the rear side in the direction of rotation 41 a blade 20 sit, so that they offer a very low flow resistance.

5 and 6 another embodiment of the invention is explained. This embodiment is simpler than the construction described above, since the foam downpipe can be omitted. Essentially horizontal guide surfaces 53 and 54 on the air blades 20 'advantageously support the function of the bladder shield 26 on the ventilation device 4'.

It can be seen in FIG. 6 that axially extending guide surfaces are arranged on the gas blades 20 '. In the upper half of FIG. 6, short guide surfaces 53 and — as an embodiment variant — elongated guide surfaces 54 are drawn in the lower half of FIG. 6, each of which is located in the region of the gas blades 20 ′ projecting beyond the wheel disc body 19 of the rotor. The guide surfaces 53 and 54 extend only on one side from the blades 20 'in the direction of rotation 41 and do not extend to the respectively adjacent blade. A continuous opening (distance A) ensures that even coarse mechanical impurities are torn through the blade channel formed in this way, so that it always remains free of impurities. The free edge 55 of the guide surfaces 53, 54 is designed such that each center ray 58 drawn to any point 56 of the contour includes an acute angle a with the tangent 57 at this point. The edge 55 is repellent to easily fixing material, so it always remains free and fully effective.

The purpose of the short. Guide surfaces 53 consist in not letting the gas entrained by the liquid flow in the direction of arrow 24 or 41 immediately escape through buoyancy forces, but rather forcing the dispersed gas bubbles in the direction of the radial flow 24 at least for a somewhat longer distance. This increases the contact time, especially of very fine gas bubbles, with the liquid and, with the same drive power, achieves a better transition of the active components in the sucked-in gas, such as O2 in the air, CO2 in the flue gas or O3 in ozonized air. In addition, the radial flow 24 is not pushed up so strongly that it can more easily reach layers that are less near the surface.

The contact time of the gaseous and liquid media is further increased by means of guiding surfaces 54 which are elongated in the manner of a sickle, in that the stream 24 enriched with gas bubbles is covered by a thin, bubble-free stream 25 in a plate-like or umbrella-like manner. Its large horizontal pulse prevents the gas bubbles from being released from the dispersion stream 24 moving underneath. The covering stream 25, which is spreading at high speed, can only be broken by the gas bubbles if their rising force is greater than the horizontal pulse of the thin covering stream.

For heavily soiling liquids with strongly changing foam formation, it is advisable to design and mount the gassing unit 4 ″ according to the exemplary embodiment of FIGS. 7 and 8. On a float construction 42, the drive motor 7, rotor 6, immersion tube 5, foam downpipe 30 and screen 26 are provided Fumigation unit 4 "suspended in a height-adjustable manner via a variable cable 49, 50, 51. The float construction 42 can have three cantilevers 43 arranged at an angle of approximately 120 ° to one another, which are mutually supported and stiffened by struts or tubes 44. The arms 43 are arranged on standpipes 45, which can extend down to below the rotor 6 in its highest position, so that the entire device can be parked on the dry without damaging the rotor 6 on the standpipes 45. Three floats 46 are fastened to the latter with tires 47. The floats 46 can be well-sealed plastic drums, such as those used to transport liquids or the like. Large float volumes are important, in particular when used for heavily soiling liquids 1 or heavily soiling foam blankets 9, because the floats 46 are loaded with a high amount of dirt during operation.

The standpipe 45 of one of the arms 43 is upward

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extended. On this extension 45a is a console with a base 48 and a e.g. attached by a hand crank 49a to be operated winch 49. In the middle of the arrangement, where the three jib tips meet, a roller 50 directed towards the winch 49 is arranged, via which a cable pull 51 is guided by the winch. The gassing unit 4 ″ hangs from this via a suitably sturdy rain protection housing 52. By raising or lowering the gassing unit 4 ″ by means of the cable winch 49, the height Hk of the foam falling edge 34 can in each case be adapted to the thickness Hs of the foam blanket 9 and thus the optimal projection Hü can be set will. In the case of pivoting mirror heights, this overhang Hü is retained thanks to the float construction 42. Only when the foaming behavior of the liquid to be gassed changes and therefore the thickness of the foam thickness Hs fluctuates accordingly, must the height of the housing 52 be varied with respect to the mirror height 8. The invention also takes into account means with which a simultaneous change in the immersion depth t of the gassing unit 4 "can be compensated in a simple manner, for example by adjusting the height of the gassing unit 4" relative to the housing 52.

The tube and rotor construction of the exemplary embodiment io from FIGS. 5 and 6 can in principle also be used in the arrangements according to FIGS. 1 to 4 or FIGS. 7 and 8. Conversely, the latter arrangement is also suitable for vertically movable mounting with the simplified gassing device 4 '.

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4 sheets of drawings

Claims (10)

619 154 1.Device for the gassing of liquid, with a completely submerged, driven, double-sided bladed rotor, which draws gas on the side facing the liquid level via a dip tube, and on the opposite side of the rotor draws liquid from the surroundings of the rotor and both media on Dispersed rotor outlet, and with a screen arranged in the area close to the rotor and surrounding the immersion tube and running at least approximately perpendicularly, the outside diameter of which is considerably larger than the outside diameter of the rotor, characterized in that the rotor (6) is in the manner of a double-flow, radially flowing pump or impeller has a closed wheel disc body (19) carrying on both opposite sides of the conveyor blades (20, 21), which is larger in diameter (dr) than the inside diameter (di) of the dip tube (5), and that the radially inner area of the Screen (26) axially and radially interrupted s free up to the top blades (20) of the rotor (6) without touching them. 2. Device according to claim 1, characterized in that the liquid inlet side of the rotor (6) is kept free of internals and only a single screen (26) which limits the rotor outlet flow (24) is present. 2nd PATENT CLAIMS 3. Device according to claim 2, characterized in that a plurality of discontinuities (27) is arranged on the underside of the screen (26) in the area lying radially outside of the rotor (6), the annular webs being arranged concentrically to the rotor (6) and preferably projecting outwards Steps or as projections, e.g. Knobs or bolts (27) are formed. 4. Device according to claim 2, characterized in that on the gas-side, axial end faces of the blades (20 '), at least in the area projecting radially beyond the wheel disc body (19), there are guide surfaces (53, 54) which are perpendicular and which are shorter in the circumferential direction than the distance between adjacent blades (20') which extend forward in the direction of rotation (41) of the rotor (6 ') and whose free edge (55) encloses an acute angle (a) with a center beam (58) drawn to the respective contour point (56). 5. Device according to claim 1, characterized in that the wheel disc body (19) has an unshoved, rotationally symmetrical displacement body on the underside. 6. Device according to claim 1, characterized in that a foam downpipe (30) is arranged around the immersion tube (5), the height of which can be adjusted with its upper end, which forms an overflow edge (34), and which is to extend beyond the liquid surface (8) and which is opposite the gas suction channel of the immersion tube ( 5) forms a separate return duct (31) for foam (9) and / or for floating materials, which opens into an annular slot (32) surrounding the suction opening (18) of the immersion tube (5) and on the top of the rotor (6) within its suction area and tapers towards the rotor (6) at least in the area near the mouth. 7. Device according to claim 6, characterized in that there is an at least approximately axially perpendicular annular gap (33) between the outer edge of the suction opening (18) and the inner edge of the annular slot (32). 8. Device according to claim 6, characterized in that spacers (37) are provided in the upper part of the return duct (31) between the immersion tube (5) and the foam downpipe (30) for supporting the foam downpipe, which are each designed as uninterrupted sheets, for example in the form of swirl surfaces. 9. Device according to claim 1, with a float that floats on the liquid to be gassed and has a platform or a frame, characterized in that one of Drive motor (7), rotor (6), immersion tube (5), foam downpipe (30) and screen (26) existing unit as a whole can be raised and lowered relative to the float (42). 10. Device according to claim 9, characterized in that on the float (42) a cable winch (49) and at a higher point a cable deflection roller (50) is arranged, via which a cable winch (49) leading to the structural unit (51) 7, 6, 5, 30, 26).