IE46648B1 - Apparatus for gasification of liquids - Google Patents

Description

This invention relates generally to liquid treating apparatus and methodology, and more specifically relates to improved apparatus for gasification of liquids, including particularly for oxygenation of liquid wastes.

Biological waste water treatment plants or the like pro- vide environments wherein the natural processes of purification are accelerated by the mechanical introduction of an oxygen supply Either pure oxygen or oxygen provided via air can be so introduced Although approximately five times more air is required than oxygen to obtain the same degree of purification, the cost of industrial oxygen indeed favors the use of air in many such systems.

In order to provide sufficient oxygen from the air to enable the higher process rates it is necessary to introduce the air by means which function to increase the efficiency of gas transfer into the liquid. The devices thus utilized, whether, introducing either air or oxygen, also must include mechanisms to enable thorough mixing, so that the reactants may be brought into intimate contact.

Several typ© of apparatus have been employed over the years for introducing air into liquids for the aforementioned purposes. Among these are surface aeration devices, which mechanically whip the waste liquor surface, to thereby expose more liquid surface to the surrounding air. -2In a second type of aeration apparatus air is injected under pressure into the liquid body, to produce a mass of either small or large bubbles.

In another type of aeration apparatus, liquid under pressure is pumped from the bottom of a vessel and redistributed through a fine spray onto the liquid surface of the same vessel. This type of device in its mode of operation, is generally similair to surface aeration devices.

The present invention is particularly applicable to the aforementioned technology wherein air is injected into the body of the liquid to be treated, as by means of spargers, bubblers, or similar gas dispensers. In considering the mechanism of oxygen uptake or transfer in this environment, analysis indicates that the principal factors encouraging maximum oxygen uptake from air are: (1) The bubble diameter snould not be too large; (2) the bubbles injected from the dispenser should be encouraged to contact as much oxygen-starved liquid as possible immediately after emission from the dispenser; and (3) the oxygen-rich liquid immediately above the dispenser should be dispersed into the main body of liquid as rapidly as possible. In terms of these performance criteria, however, it is found that presently available commercial devices are inadequate in one or more such respects.

Summary of Invention Now in accordance with the present invention there is provided a device for gasification of a liquid in which the device is immersed, which comprises a hollow ring-like enclosure defining a generally annular chamber for receiving gas to be introduced into the liquid. Gas inlet means communicate with the -3chamber to enable gas flow thereto. The longitudinal axis passing through the plane of the ring is vertically oriented when the device is immersed in the liquid, with the central opening of the ring lying on this axis and defining a passageway for induced flow of liquid. An axially-extended constriction of substantially constant diameter is defined at the middle of this passageway, and is provided with apertures communicating with the annular chamber. As gas flows from the chamber into the constriction, the resultant ascending bubble stream, induces flow of liquid upwardly through the passageway. The enclosure surfaces bordering and defining the passageway form an extended converging cone from the flow input end of the passageway to the constriction, which acting in conjunction with the constriction, increases the flow velocity therethrough. This augments shearing of gas bubbles emerging from the apertures, and promotes small bubble formation - in turn producing a higher rate of gasification. The enclosure surfaces bordering and defining the passageway form an extended diverging cone above the constriction, which acts to distribute the gasified flow into the body of the liquid.

The apertures provided at the constricted portion of the central passageway may be a series of holes either randomly located on the axially-facing surfaces of the enclosure, or arranged in rows. The apertures can also be in the form of a slit, i.e. a contiuous aperture, or a plurality of slits either in continuous or discontinuous form. The apertures may also comprise any combination of slits or holes. Where the apertured surface Comprises rows of holes or slits it is possible that when the device is immersed in liquid with the centrally defined passageway substantially vertical, the holes or slits in the upper-446648 most row are smaller in size than those in the row immediately beneath the said row. This arrangement ensures that bubbles of gas are emitted from substantially all the apertures into the liquid thereby ensuring maximum gasification rate. If it were not made easier for gas bubbles to escape from the lower apertures by increasing the size thereof relative to the aperture size in the upper rows, gas bubbles would only escape from the uppermost rows of apertures that is, by following a route offering the least pressure resistance.

It is also within the province of the invention for the apertures to be located on that portion of the converging cone (i.e. at the flow input side of the device) which is immediately upstream from the constricted portion. These apertures can either replace the apertures at the central constriction, or pre15 ferably be provided in addition to the latter.

The body of the ring-like enclosure may be generally circular in cross-section or of any other suitable form, for example, generally elliptical, or of any regular or irregular cross-sectional shape. It should therefore be understood that 20 the term ring-like or ring-shaped, when used herein, is intended to encompass all of these forms.

In accordance with a further aspect of the invention, the aforementioned hollow ring-shaped enclosure or member may be adapted for containing a depth weighting medium in an amount in relation to the mass of the ring member as to enable the ring member in operation to be immersed in a liquid at a pre-determined depth. -5Brief Description of Drawings The invention is diagrammatically illustrated, by way of example, in the drawings appended hereto, in which: FIGURE 1 is a longitudinal sectional view of a pre5 ferred embodiment of a gasification device in accordance with the invention; FIGURE 2 is a top plan view of the device of Figure 1; and FIGURE 3 is longitudinal sectional view, similar to Figure 1, but rendered in a schematic fashion in order to illustrate certain relationships in the illustrated device.

Description of Preferred Embodiment In Figures 1 and 2 herein longitudinal cross-sectional and top plan views appear of a gasification device 20 in accord15 ance with the invention. Device 20 comprises a cylindrical wall member 21, top and bottom wall members 22 and 23, inwardly facing sloping wall members 24 and 25, central wall member 26 joining members 24 and 25, and an upwardly directed extension 19. All of the cited wall members may be integrally formed or can be se20 cured to one another by heat sealing, welding, etc. Because of their ease of fabrication, and especially their resistance to corrosion or chemical attack, certain plastics including especial! ,y polyethylene are preferred materials for the described portions of device 20.

The wall members 21, 22, 23, 24, 25 and 26 form a hollow generally ring-shaped body defining an annular chamber 29 space enclosing a gas/(J7). According to a further aspect of the -6present invention, there is contained in the chamber 29 a depth weighting medium 30 in an amount in relation to the mass of device 20, as to enable the device in operation to be immersed in the liquid at a pre-determined depth.

The depth weighting medium 30 in this preferred embodiment of the device may be of the same or similar materials as that of which the device 20 is comprised, and in which case the weight ing medium may comprise the lower part of chamber 29, below the level of the apertures 28 of the inwardly directing surface there of, and may be integral therewith. Where the weighting medium comprises a different material from that of which the ring-like device 20 is constituted, the weighting medium may be massive or discrete, i.e. granular, and may be located in the lower part of the chamber 29, below the level of the apertures 28. In granular form the weighting medium may preferably be lead shot, gravel, marble, chippings, or suitable dense materials.

The depth weighting, medium 30 may also comprise dense materials capable of flowing in one form, that is, in liquid or semi-liquid form, for introduction into the hollow chamber 29, which material subsequently changes, that is sets to a solid or semi-solid or rigid mass. Examples of such materials are cold dense materials, or material mixtures, for example, mineral cement, concrete, resins, plastics materials, hot setting, i.e. thermo-setting materials, e.g. resins, plastics, etc. Where the weighting medium 30 is in massive form it may comprise, for example, a ring of high density material of dimensions such that it can rest in the lower part of chamber 29, below the level of the apertures 28. -7A gas inlet 34 is formed at the top surface 22 of member 20 for admission of gas such as air or oxygen from an external gas supply (not shown) into the interior gas space 37 of device 20 The axially-facing surfaces of members 24,-25, and 26 define a central passageway 39 through which the liquid media in which device 20 is immersed may flow upwardly - such flow being induced by the gas flow introduced via inlet 34. Passageway 39 can be regarded as consisting of three successive portions, i.e. a lower converging cone-like portion 41 at the flow inlet side of device 20; a central axially-extended constriction 27 of substantially constant diameter; and an upper, diverging cone-like portion 43 at the upper or flow outlet side of device 20.

Apertures 28 are located at the constriction 27 (i.e. through wall 26), to permit gas to pass from space 37 into constriction 27. The resulting ascending bubble stream acts to induce an upward flow through passageway 39 of the liquid in which device 20 is immersed. It should be understood that this ascending bubble stream is indeed, the sole instrumentality effecting liquid flow through passageway 39 - no mechanical pumps or the for this purpose like are utilized/With the instant apparatus. Further aspects of this action will be discussed below in connection with Figure 3.

Device 20 when immersed in a liquid to be gasified, is connected to a compressed air (or other gas) supply by a flexible pipe or hose, which is connected to inlet 34. The bottom surface of wall member 23 carries a series of formed feet 31, which enables stabilization of the device if it is desired to emplace samb at the bottom of a tank or so forth, and also stabilize the device prior to use thereof, i.e. when outside the tank.

In the more usual mode of operation within the interior of the vessel or tank with which device 20 may be utilized, support means in the form either of rigid means such as rods, etc., -8or in the form of non-rigid means such as chain or nylon rope, are secured to device 20 by being passed through openings 32 with in a metallic support ring 33 which is secured about the top extension 19 of device 20. The rigid type of support structure will be utilized if device 20 is to be held down firmly in a buoyant or near buoyant operational position; the non-rigid type of structure, i.e. chain, rope, etc, will be utilized if device 20 is to be immersed to a floating or near floating position, i.e. at a relatively shallow depth in the vessel within which device 20 is used. any other Before air or^ gas under pressure is introduced into device 20, the liquid to be gasified will be present within the interior space 37, and upon application of air pressure to cause bubble formation, the liquid is ejected through apertures 28. The depth weighting medium 30 in the chamber 29, may when in granular form be disturbed on the application of air pressure to cause bubble formation, and may even be ejected with the liquid through the apertures, unless the granules are sufficiently dense and/or sufficiently large.

It must be appreciated that gasification devices comprising hollow ring-like members as disclosed in the present specification, are normally made from conventional materials which are relatively strong, easily fabricated and inexpensive, e.g. conventional plastic materials readily meet such requirements Devices made from such materials when submerged in a liquid and connected to a compressed air supply, are in effect small· buoyant vessels. Submersion of such devices at any depth in a liquid can necessitate a rigid locating support or suspension from which the -9is device/susPer,ded, said rigid support itself requiring to be fixedly located, either in or above the liquid to be gasified. Use of the depth weighting device 20 as set forth in Figures 1 and 2, avoids the need for such auxiliary structures, both in and above the liquid to be gasified, thereby increasing the simplicity and reducing the cost of a system incorporating such devices.

Xn accordance with an additional aspect of the present invention, the efficiency of the gasification or aeration proces may be augmented by raising the temperature of the gas bubbles above ambient. For such purposes, an electric resistance heatin element or elements may be embedded in the wall members 21 through 26 of the device 20, with the free ends from the element or element leaving the wall members at a suitable point, e.g. adjacent the gas inlet, for enabling connection with sources of electrical power in a manner known in the art. These electrical resistance elements may, for example, be embedded during the formative process for the plastics materials which may commonly comprise device 20. The resistance elements can be of conventional construction known in the art, such as, for example, the well-known Calrods or so forth.

Similarly within the scope of the present invention there may be a liquid treatment system comprising a vessel for containing liquid to be treated, and including one or more of the present gasification devices. In this instance the system will also be provided with one or more means for introducing gas into the device or devices.

It should also be mentioned that the gaseous composition required for the gasification may be initially provided to the said -10liquid form may or other gases in^be pumped to the said device under pressure, with, the change of state to gaseous form occurring some time prior to or during the dispensing of the composition into the body of liquid to be gasified.

In Figure 3 herein, a longitudinal sectional view appears, which depicts a device generally similar to that described in connection with Figures 1 and 2. In the present view the showing however, is schematic - in order to enable discussion of certain relationships which exist in the present apparatus, and which are instrumental in achieving the outstanding results enabled by such device.

As thus seen in Figure 3, the present device 50 may be regarded as consisting of a ring-like enclosure 51 defining a generally annular chamber 53 - to which air or oxygen is provided in accordance with previous discussion. The entire device SO may be regarded during use of same, as being positioned in a body of liquid such as waste.water - . which is generally designated at SS, and can be regarded as enveloping device 50, i.e. typically the apparatus (as already discussed) can either be suspended above the bottom of such liquid, or else rest on the bottom of the tank, river bed, or the like.

Pursuant to the present invention it is seen that the central axis 57 which passes through the plane of the ring, is thus aligned with the central passageway 59 of device 50. This passageway 59, in turn, can be deemed to consist of three contiguous portions: Firstly a central, axially-extended constriction 61, which is preferably provided with apertures 63 as previously discussed. This constriction 61 is of substantially constant diameter- by extending for a substantial axial distance -11apertures of any reasonable number may be provided, so that the gas flow from same can be subjected to the high shearing effect in accordance with the flow rate increases provided by the device of the invention.

In addition to the central constriction 61, it will be seen that axially-facing surfaces of enclosure 51 define a converging cone-like portion 65, which extends from the flow input side 67 of device 51 to constricted portion 61. This portion 65 extends for a substantial axial length, as will be further discussed hereinbelow, and serves in conjunction with constriction 61 to increase the flow velocity through such constriction once the flow is induced by the ascending bubble stream created by gas streaming through the apertures 63 from chamber 53 of enclosure 51. (The general fiow pattern thus induced is suggested in the Figure by arrows 54) The constriction 61 thus acts in conjunction with converging portion 65 to throttle the flow and increase the velocity of same. This, in turn, introduces a high shearing at apertures 63, for the purposes aforementioned, i.e. to produce small bubble size as the individual gas bubbles emerge from such apertures. As has also been previously mentioned, apertures (as suggested at reference numeral 66) can also be provided at portion 65- preferably toward the end thereof adjacent constriction 61. Such further apertures 66 can augment; or in some instances replace, apertures 63.

In addition to the two passageway portions thus far described, a third portion is present in accordance with the invention. In particular it is seen that the axially-facing surfaces of the enclosure 51 above constriction 61 form a diverging conelike portion 69 of (again) axially-extended dimensions. This portion 69 serves to disperse the oxygenated or aerated liquid into the general' body of liquid in the tank or natural reservoir, of liquidAn which device SO is immersed. -12Pursuant to the principles of the present invention, it has been found that certain relationships are preferred as between the converging and diverging cone-like portions 65 and 69, and the constriction 61 - in order to provide appropriate increase in flow rates through the constriction, and appropriate divergence of flow to achieve the required rapid distribution and dissipation of the aerated stream into the general body of liquid Referring to Figure 3, it is thus found that the ratio R of the axial lengths L of portions 65 and 69 to the length Z of constric10 tion 61, i.e. the ratio L/Z should be between 1:1 and 2:1. Preferably this ratio R should be in the range of from 1.25:1 to 2:1, and relatively optimally at about 1.5:1.

In the presence of the above relationships the angle of convergence or divergence A of the cone-like portions 65 and 69 (A is the angle which the walls of portions 65 and 69 make with axis 57) should be from between 15° to 45°, preferably from 25° to 35°, and optimally about 30°. Preferably the diameter D of constriction 61 is approximately equal to its axial length Z.

In a typical apparatus design pursuant to the foregoing criteria, constriction 61 may have a diameter of 4 to 6, a corresponding axial length Z, and be provided with a plurality of apertures 63 of about S/16 diameter.

While the present invention has been particularly set forth in terms of specific embodiments thereof, it will be under stood in view of the instant disclosure, that numerous variation upon the invention are now enabled to those skilled in the art, which variations yet reside within the scope of the instant teaching. Accordingly the invention is to be broadly construed, and limited only by the scope of the claims now appended hereto.

Claims (17)

1. A device for the gasification of a liquid in which the device is immersible, comprising: a hollow ring-like enclosure defining a generally annu5 lar chamber for receiving gas to be introduced into sai-d liquid; gas inlet means communicating with said chamber for enabling flow of gas thereto; the longitudinal axis passing through the plane of said ring being vertically oriented when said device is immersed in . 10 said liquid, and the central opening of said ring defined by the axially-facing surfaces of said enclosure defining a passageway for induced flow of said liquid; an axially-extended constriction of substantially constant diameter being defined at the middle of said passageway, 15 said constriction being provided with apertures communicating with said annular chamber to enable gas flow into said restriction, the said gas flow and resulting ascending bubble stream inducing flow of liquid upwardly through said passageway, said gas flow and bubble stream comprising the sole means effecting 20 said liquid flow; the said surfaces of said enclosure bordering and defin ing said passageway forming a cone-like portion converging from the flow input end of said passageway to said constriction, to thereby define an axially-extended zone of flow convergence, 25 whereby in conjunction with said constriction to increase the flow velocity through said constriction, thereby to augment shear ing of gas bubbles emerging from said apertures and promote small bubble formation; and -14the said surfaces of said enclosure bordering and defin, ing said passageway forming a second cone-like portion diverging axially for an extended length above said constriction, whereby to define an extended zone of flow divergence for distributing 5 the gasified flow into the body of said liquid.

2. A device in accordance with claim 1, wherein the angle A made by the walls of said converging and diverging cone-like portions with respect to said axis, is between 15° and 45°; and wherein the ratio R of the axial dimension L of said cone-like portions 10 to the axial dimension Z of said constriction,is in the range of from 1:1 to 2:1.

3. A device in accordance with claim 2, wherein A is in the range of from 25° to 35° and R in the range of from 1.25:1 to 2:1. 15

4. A device in accordance with claim 3, wherein A is 30° and R is 1.5:1.

5. , A device in accordance with claim 1, wherein the apertured surface of the ring member comprises a surface having one or more continuous apertures therein, the or. each aperture being substant20 ially in the form of a slit.

6. A device in accordance with claim 1, wherein the apertured surface of the ring member comprises a surface having one or more holes therein. -15466 43

7. A device in accordance with claim 6, wherein said holes are located at intervals on one or more circumferential lines along said surface.

8. A device in accordance with claim 7, wherein said apertured 5 surface comprises holes located at intervals on each of a plurality of circumferential lines on said surface and wherein the average size of holes in any one line is less than that of the holes in the line immediately below said line.

9. A device in accordance with claim 6, wherein said apertured 10. Surface comprises at least one row of circumferentially disposed holes and at least one continuous slit aperture.

10. A device in accordance with claim 9, wherein said apertured surface comprises more than one row of circumferentially disposed holes with at least one continuous slit aperture located between 15 each row.

11. A device in accordance with claim 8, wherein said apertured surface comprises more than one continuous slit aperture, with at least one row of circumferentially disposed holes located between each slit. 20

12. A device in accordance with claim 1, further including depth weighting means deposited within at least a portion of the said hollow body of said ring-like enclosure, to enable said device in operation to be immersed in said liquid at a pre-determined depth. -16i 8

13. A device in accordance with claim 12, further including means for securing overhead support means to said device, for enabling positioning of said device within said liquid.

14. A device in accordance with claim 1, wherein said ring-like enclosure includes electrical heating means within the walls defining said enclosure, for enabling heating of said gas to increase the rate of gasification of said liquid.

15. A device in accordance with claim 1, further including a plurality of apertures at the end of said cone-like converging portion adjacent said constriction, said further apertures communicating with said chamber for enabling further gas flow into said passageway toward the upstream end of said passageway.

16. A device for the gasification of a liquid in which the device is immersible, comprising: a hollow ring-like enclosure defining a generally annular chamber for receiving gas to be introduced into said liquid; gas inlet means communicating with said chamber for enabling flow of gas thereto; the longitudinal axis passing through the plane of said ring being vertically oriented when said device is immersed in said liquid, and the central opening of said ring defined hy the axially-facing surfaces of said enclosure defining a passageway for induced flow of said liquid; an axially-extended constriction of substantially constant diameter being defined at the middle of said passageway; the said surfaces of said enclosure bordering and defining said passageway forming a first cone-like portion converging from the flow input end of said passageway to said constriction, -174 6 ϋ 48 to thereby define an axially-extended zone of flow convergence, whereby in conjunction with said constriction to increase the flow velocity into and through said constriction; the said surfaces of said enclosure bordering and defining said passageway forming a second cone-like portion diverging axially for an extended length above said constriction, whereby to define an· extended zone of flow divergence for distributing the gasified flow into the body of said liquid.; and said second cone-like portion being provided toward its end adjoining said constriction with apertures communicating with said annular chamber to enable gas flow into said first cone-like portion, the said gas flow and resulting ascending bubble stream inducing flow of liquid upwardly through said passageway, thereby to augment shearing of gas bubbles emerging from said apertures and promote small bubble formation; and said gas flow and bubble stream comprising the sole means effecting said liquid flow.

17. A device for the gasification of a liquid substantially as described herein with reference to the accompanying drawings.