GB2346816A - Apparatus for dissolving oxygen in a body of water with pivotable jet nozzles - Google Patents

Abstract

The apparatus includes jet nozzles 2 for returning water that has been oxygenated back into a body of water wherein the nozzles are pivotable about the axis X of a sparge bar perpendicular to the nozzle axis. The sparge bar can be pivotally-adjusted using link members 4 connected to sliders 6. The nozzles 2 can be directed vertically downwards in deep water or directed in a more horizontal direction 2' in shallow water to minimise sedimentary agitation. The nozzles may be provided with a baffle plate (30,Fig 4) to diffuse the water flow from the nozzles.

Description

GAS DISSOLUTION This invention relates to the dissolution of gas in a liquid, and in particular to the dissolution of oxygen in a body of water such as a lake, reservoir or estuary.

Mobile oxygenation systems for rivers are known, and are used to alleviate the oxygen depletion which occurs when polluted water enters a river, such as after heavy rainfall. These systems commonly comprise a barge having an air separation unit for the production of the required oxygen, a buffer vessel and a plurality of subatmospheric venturis through which water is pumped and into which the oxygen is injected. Oxygenated water is then passed to a sparge bar arrangement having a plurality of nozzles through which the water is retumed to the river. The water supply to the venturis is via submersible pumps mounted in a pool at the bow of the barge.

The above apparatus relies on the plurality of outlet nozzles for oxygenated water and also, more significantly, on the natural currents and eddies in the river water to effect thorough mixing of the oxygenated water with the river water. Because this thorough mixing and oxygenation of the river water can be effected largely by the flow of the river water, the velocity at which the oxygenated water is discharged from the outlet nozzles need not be high. This also has the advantage that the downwardly-facing nozzles do not disturb silt on the river bed. Also, oxygenation of the river water can be achieved with the barge largely static.

Such conventional apparatus is however not suited to applications in which there is insufficient or no natural flow-in a body of water such as a lake, reservoir, canal, slow-moving river or estuary, for example. In such applications there is generally an equivalent requirement to prevent disturbing silt as in a river (and the water depths in each instance are often similar), so that the downwardly-facing nozzles must not discharge oxygenated water at too great a velocity. However, the surface area of water to be oxygenated in this kind of application is normally very much greater than in a river. And the absence of any significant currents in the body of water means that the barge must be moved around in order to oxygenate the entire body of water.

Providing high velocity jets of oxygenated water in lateral directions has been tried, however this requires high pressure pumps which, when employed in combination with the low pressure pumps necessary for providing low velocity oxygenated water jets from the downwardly-facing nozzles, is both complicated and expensive.

The invention therefore provides apparatus for dissolving oxygen in a body of water comprising a vessel adapted to receive water extracted from the body of water, means to pass oxygen and/or air into the extracted water thereby at least partially to oxygenate the extracted water into the body of water, and means to retum the oxygenated water into the body of water, the retum means comprising at least one nozzle adapted to discharge the oxygenated water in a jet thereof, the nozzle being pivotable about an axis substantially perpendicular to the axis of jet discharge.

With such an arrangement, a high velocity jet of oxygenated water can be directed into the body of water so as to maximise its penetration into and mixing with the water whilst minimising the risk of disturbing silt, sediment and the like at the bottom of the body of water. Also, increasing the velocity of the jet of oxygenated water increases the amount of oxygenation possible; because there is a high degree of shear between the high velocity jet and the static water, bubbles of oxygen in the jet are broken up into smaller bubbles, which disperse and dissolve into the body of water. Accordingly, more oxygen can be introduced into the extracted water than can dissolve therein, since the shear effect when the jet is introduced into the body of water will ensure further, usually complete, dissolution.

The apparatus may be static or it may be mounted on a floating platform, or barge.

If mounted on a platform, the nozzle (s) (which are preferably immersed in the water) can advantageously be arranged so as to pivot about a horizontal axis. In such an arrangement the barge can either be moored around the body of water or, if the body of water is not too large, it can be moved and allowed to rotate (about a vertical axis) only. As the barge moves, the angle of pivot of the nozzle (s) can be varied so as to ensure that the jet (s) penetrate as far as possible into the water without disturbing the silt at the bottom of the water and without breaching the surface of the water. This variation can be effected automatically, in concert with means adapted to recognise the position of the barge and the direction of the jet (s) relative to the body of water, and the depth of the body of water and/or the contours of the bottom of the body of water. This variation in the pivot angle can be accompanied by control of the mass flow rate (hence velocity) of oxygenated water through each nozzle in order to optimise oxygen dissolution in the body of water, and this control may be automatic, in response to the pressure sensed in the jet at the nozzie outlet.

The apparatus may comprise a pivotable sparge bar to which two or more nozzles are mounted. The sparge bar acts to distribute oxygenated water to the nozzles, and the nozzles can be disposed so as to reduce stresses on the sparge bar mounting/pivoting arrangement caused in reaction to the high velocity discharge of oxygenated water through the nozzles.

In addition to the pivotal motion around a single, preferably horizontal axis, the nozzles may be arranged so as to pivot about a vertical axis, in a substantially horizontal plane. Such an arrangement enables a considerable volume of the body of water to be oxygenated without requiring the body or platform to which the nozzles are mounted to be moved, and is particularly useful where the body of water is generally shallow but has a heavily contoured bottom surface.

The nozzle (s) are preferably of the type referred to in our European Patent No.

602762 B1.

In order to dissipate rapidly the energy in the jet of oxygenated water, which is advisable in applications where agitation of sediment (likely where the body of water is shallow, for example) is to be avoided, means are preferably mounted adjacent the or each nozzle outlet in order to interrupt the flow of the jet. These means are preferably configured so as simultaneously to create turbulence, which in turn increases the oxygen dissolution efficiency of the apparatus. A suitable means might comprise one or more perforated baffle plates which are selectively and progressively movable into and out of the jet flow so as respectively increasingly or decreasingly to interrupt the flow and create turbulence. The skilled person will, however, appreciate that there are many altemative means and baffle plate configurations which will serve progressively to interrupt the jet ffow and to create turbulence, such as an ajustable aperture iris mechanism, for example.

In addition to the pivotable nozzle (s), further nozzies for discharging a proportion of the oxygenated water may be provided, which nozzles are fixed in relation to platform. These further nozzles are preferably directed downwardly and have a low outlet velocity, so as to effect thorough oxygenation of the water beneath the platform without disturbing silt or sediment.

The invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a mechanism for pivoting an oxygenation nozzle about a horizontal axis in accordance with the invention; Figure 2 is an elevation view of a first embodiment of an apparatus in accordance with the invention; Figure 3 is a schematic view of a mechanism for pivoting an oxygenation nozzle about horizontal and vertical ones in accordance with the invention, and Figure 4 is a schematic view of a nozzle arrangement forming part of an apparatus in accordance with the invention, each nozzle shown comprising a perforated baffle plate progressively movable into and out of the jet flow from the nozzle.

Figure 1 shows a pivotable nozzle 2 attached by a link member 4 to a reciprocal slider 6. Linear movement of the slider 6 to its lower position 6'serves to pivot the nozzle 2 about axis X to position 2'. As shown, the nozzle 2 has an arc of movement between horizontal and 10 from the vertical, ie an arc of about 80 Referring now to Figure 2, a plurality of nozzles 2 is mounted to a pivotable sparge bar 8, which has a fixed central portion 10. Link members 4 are pivotably attached to the sparge bar 8 and to elongate slider 6. Slider 6 is slidably mounted to slides 12 and is moved therealong by the operation (by hand or motor) of screw 14. As described in connection with Figure 1, movement of slider 6 causes the sparge bar 8 to pivot. Nozzles 2, which are preferably of the type described in our European Patent No. 602762 B1, are supplie with aeration water via main 14 which is fixed.

Connection between fixed main 14 and pivotable sparge bar 8 is through semi-rigid stainless steel hose flanges 16. Additional fixed flanges 18 may be employed both to extend the length of the sparge bar and also to enable nozzles to be set at different angles to each other, relative to the axis of the sparge bar 8.

In use, oxygenated water is pumped under pressure along fixed main 14, through flanges 18 to nozzles 2, and hence into the body of water to be oxygenated (at least the sparge bar 8 and the nozzles 2 being immersed in said water). Oxygenated water (the process whereby the water is oxygenated before emerging from the nozzle forming no part of this invention, and being amply described in our European Patent Nos: 389230 B1 and 602762 B1, for example) is discharged from the nozzles at high velocity, this velocity creating shear forces which aid dissolution of the oxygen in the body of water. When appropriate (such as when the body of water is sufficiently deep) the slider 6 is located such that the nozzles 2 discharge downwardly, thereby oxygenating the water beneath without disturbing sediments which would negate the benefits of oxygenation. When the body of water is shallow, and the risk of sedimentary agitation much greater, screw 14 is operated so as to raise slider 6 on slides 12, and to rotate sparge bar 8 relative to fixed portion 14, thus moving nozzles 2 to a more horizontal position. in this position, jets of oxygenated water are discharged from nozzles 2 into the body of water, oxygenating it without disturbing the sediment at its bottom.

Figure 3 illustrates a mechanism for pivoting a nozzle 2 in both a vertical and a horizontal plane. Raising or lowering handle 20 causes nozzle 2 to be depressed or elevated, respectively, via pivoting linkage 22. Because nozzle 2 is also pivotally mounted at 24, movement of handle 20 in the horizontal plane causes nozzle 2 also to move in that place. Adjustment of handle 20 can be manual or by motor, and nozzle 2 can be held in any position by locking handle 20 by means of locking handles 26. Oxygenated water is pumped to nozzle 2 through flexible pipe 28.

The nozzles 2 shown in Figure 4 are each provided with a baffle plate 30. Baffle plates 30 are progressively moveable by means of link rod 34 to occlude the outlets 32 of the nozzles 2 and effectively to throttle the flow therefrom. The baffle plates 30 are also perforated so as to diffuse the flow of oxygenated water. Oxygenated water is discharged in the direction of the large arrows shown from nozzle outlets 32 and is deflected and its energy dissipated by the perforated baffle plates 30, increasingly so as the baffle plates are moved across the outlets 32 so as to interrupt the flow of the jets of oxygenated water. This not only dissipates the energy in the jets, helping prevent undesirable sedimentary agitation, but also creates considerable turbulence and shear in the jet flow, thereby enhancing oxygen dissolution.

Those skilled in the art will appreciate that there are many straightforward modifications that may be made to the apparatus illustrated in the Figures. For example the numbers and dispositions of nozzles could be other than shown, as could the angles through which they pivot. The number and configurations of the baffle plates can also be varied, and the apparatus could easily be mounted to a fioating platform and controlled by a suitably programmed computer linked to means for determining the depth of water beneath the platform and the mass flow rate of water through the nozzles, so as entirely automatically to vary the nozzle pivot angles, the mass flow rate of oxygenated water discharged from the nozzles and/or the amount of interruption/turbulence created by the baffle means in order to optimise oxygenation of the body of water whiist minimising sedimentary disturbance. Finally, although described in connection with treating a body of water, it will be recognised that this invention is equally applicable in other fluid treatment fields, such as sewage, industrial effluent or chemical treatment.

Claims (12)

1. CLAIMS 1. Apparatus for dissolving oxygen in a body of water comprising a vessel adapted to receive water extracted from the body of water, means to pass oxygen and/or air into the extracted water thereby at least partially to oxygenate the extracted water into the body of water, and means to return the oxygenated water into the body of water, the retum means comprising at least one nozzle adapted to discharge the oxygenated water in a jet thereof, the nozzle being pivotable about an axis substantially perpendicular to the axis of jet discharge.
2. 2. Apparatus as claimed in Claim 1 in which the apparatus is mounted on a floating platform, each nozzle in use being immersed in the body of water.
3. 3. Apparatus as claimed in Claim 1 or 2 wherein the perpendicular axis is, in use, substantially horizontal.
4. 4. Apparatus as claimed in Claim 1,2 or 3 wherein the or each nozzle is, in use, pivotable about a substantially vertical axis.
5. 5. Apparatus as claimed in any preceding Claim comprising means for varying the angle of pivot of each nozzle.
6. 6. Apparatus as claimed in Claim 5 when mounted on a floating platform on a body of water comprising means adapted to vary the angle of pivot in accordance with the depth of the body of water beneath the floating platform.
7. 7. Apparatus as claimed in Claim 6 comprising means for varying the mass flow rate of oxygenated water discharged from each nozzle.
8. 8. Apparatus as claimed in Claim 7 comprising means for sensing the pressure in a jet of oxygenated water at or adjacent the outlet of the nozzle from which the jet is discharged.
9. 9. Apparatus as claimed in any preceding Claim comprising means adjacent the or each nozzle outlet adapted selectively to interrupt and to create turbulence in the jet of oxygenated water discharged therefrom.
10. 10. Apparatus according to any preceding Claim comprising a pivotable sparge bar for the distribution of oxygenated water to two or more nozzles mounted thereto.
11. 11. Apparatus according to any preceding Claim comprising one or more further nozzles adapted to discharge in jet (s) a proportion of the oxygenated water into the body of water, each of which further nozzles being fixed relative to the vessel.
12. 12. Apparatus for dissolving oxygen in a body of water substantially as hereinbefore described and with reference to the accompanying drawings.