GB1599647A

GB1599647A - Apparatus for gasification of liquids

Info

Publication number: GB1599647A
Application number: GB48512/77A
Authority: GB
Original assignee: VENTURATOR Ltd
Current assignee: VENTURATOR Ltd
Priority date: 1977-11-22
Filing date: 1977-11-22
Publication date: 1981-10-07
Also published as: DE2758923A1; ES465780A1; CH619200A5; IT1089255B; BE862466A; NO781958L; FR2409083A1

Description

(54) APPARATUS FOR GASIFICATION OF LIQUIDS (71) We, VENTURATOR LTD., a company organised and existing under the laws of England, of 62a High Street, Frimley, Camberley, Surrey, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for the gasification of liquids, for example the aeration or oxygenation of water.

British Patent No. 1,482,191 discloses a device for the gasification of liquids which comprises a hollow ring member having a gas inlet and an inwardly facing surface which bounds a central liquid passageway. A portion of the inwardly facing surface is apertured so that in operation gas passes from the hollow into liquid in the passageway. The cross-section of the liquid passageway progressively increases away from the apertured area.

In operation the device is immersed in a liquid preferably such that the liquid passageway has its longitudinal axis substantially vertical. The gas forms bubbles on passing through the apertures into the liquid in the passageway, the bubbles rising through the liquid to induce a flow of liquid upwardly through the passageway. The induced liquid flow passing the apertures exerts a shearing effect on the gas bubbles as they leave the ring member thereby producing smaller gas bubbles than in prior devices and in consequence increasing the overall gas/liquid interface area for a given volume of gas, and thus increasing the rate of gas-to-liquid transfer.

Such devices have been proven to be highly effective in practical use, particularly for aeration of waste water containing aerobically degradable organic matter, for example sewage. Particular devices that are in use measure approximately 500 mm. high by 470 mm. across and are suspended, e.g. by chains, about 300 mm. clear of the base of a treatment vessel containing waste water to a depth of about 1.9 metres or more. This is found to provide a good strong circulation pattern for effective aeration.

A requirement has arisen for effective gasification of liquid in more shallow treatment vessels, for example in smaller sewage or waste water treatment plants, and particularly in fish farming tanks. The prior devices are found to be not so effective when the water is much less than about 1.9 metres in depth. In addition more shallow treatment vessels or fish farming tanks tend to be laterally extensive and difficulties there arise in suspending fairly heavy devices within the water at a desired height above the base.

Relatively tall tubular devices, weighted with concrete bases, as suggested in No. 1,482,191, have been found ineffective in solving this problem and in addition can be unstable and topple over under certain water flow and circulation conditions.

According to the present invention there is provided a device for the gasification of liquids comprising a horizontal hollow ring member, said member having a gas inlet and an inwardly facing surface which bounds a vertical central liquid passageway, said surface including an apertured intermediate portion bounding a throat in said passageway, whereby in operation gas within the hollow is emitted through said apertures into said throat to form bubbles in the liquid, said ring member including at least two legs bounding liquid entry passageways therebetween, said entry passageways communicating with the lower end of said central liquid passageway, whereby said device in operation can stand on the base of a liquid treatment vessel.

The ring member including said legs is preferably of greater overall diameter than overall height.

The total cross-sectional area for liquid flow through said entry passageways is preferably substantially greater than the crosssectional area of said throat.

Preferably three said legs are provided, defining three said liquid entry passageways therebetween. The legs are disposed radially outwardly as far as possible for stability.

Since the ring member is hollow the device will normally require weighting in order to stay in a desired free-standing position on the base of the treatment vessel. The legs are preferably hollow and formed integrally with the ring member, thereby enabling the complete device to be made of a tough relatively rigid plastics material. The hollow legs are then filled with a dense material.

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a gasification device according to the invention; Figure 2 is an underneath plan view of the device; Figure 3 is a vertical section, on line A-A of Figure 2, through the device; and Figure 4 is a top plan view of the device.

Referring to the drawings, there is shown a gasification device comprising a generally horizontal hollow ring member 10 of greater overall diameter than overall height. The member has three entry blanks 11 at least one of which may be pierced to accommodate a gas inlet spigot for attachment of a gas supply pipe. The member has an inwardly facing surface in three portions 12, 13 and 14 defining a generally vertical central liquid passageway 15. The middle portion 13 is of least diameter to define a throat, and is apertured at 16 around the throat. The upper portion 12 flares generally conically away from the throat. The lower portion 14 also flares outwardly, downwardly away from the throat, the degree of flare increasing downwardly in bell-mouth fashion as shown in Figure 3.

The ring member includes three integrally formed hollow legs 17. 18 and 19, bounding liquid entry passageways 20, 21 and 22 therebetween. These passageways all communicate with the lower end of the central liquid passageway 15. The bell-mouth surface portion 14 continues in uninterrupted smooth curve down the inside of each leg 17, 18 and 19 as best shown in Figure 3. The legs are disposed radially outwardly as far as convenient, bearing in mind considerations of smooth liquid flow paths and manufacturing difficulties, in order to assist in stability of the device. The total cross-sectional area for liquid flow through the entry passageways 20. 21 and 22 is substantially greater than the throat area of passageway 15. This is best seen by a study of Figures 2 and 3.

The device is conveniently formed of a tough relatively rigid plastics material such as polyethylene. It may be convenient to form the device in two halves along the equatorial plane and subsequently joined together. After manufacture, the hollow legs are each substantially filled with a cheap, relatively dense material such as cast iron shot pellets or possibly concrete. The pellets are preferably introduced through the entry blanks 11 which are pierced for the purpose.

The entry blanks are situated directly above the legs, as shown in Figure 1. Pierced blanks not required for gas entry are subsequently closed.

One practical form of the device measures 457 mm. overall in diameter, stands 279 mm.

overall in height, and the throat diameter is 101 mm. The other dimensions are in proportion as shown in the drawings. The device is completely hollow, the wall thickness being approximately 5 mm. The overall volume is approximately 0.031 cubic metres and the weight of water displaced therefor approximately 20 Kg. Each leg therefore requires at least 7 to 8 Kg. of weight therein in order to provide a reasonable net weight for the device when standing free on the base of a filled liquid treatment vessel.

In use, one or more such devices stand on the base of a vessel containing liquid to be gasified, for example for aeration of waste water containing aerobically degradable organic matter such as sewage, or for aeration or oxygenation of fresh water in a fish farm tank. Gas is supplied by pipe to the inlet or inlets 11, for emission from the aperture 16 into liquid in passageway 15. The gas forms bubbles on passing through the apertures and the bubbles rise through the liquid to induce a flow of liquid in through each of the entry passageways 20, 21 and 22 and then up through the central passageway 15. The induced liquid flow passing through the apertures exerts a shearing effect on the gas bubbles as they leave the apertures thereby producing smaller gas bubbles for more effective gasification.

For the illustrated 101 mm. throat the free air delivered through the apertures should lie in the range of from 25 cubic metres/hour to 50 cubic metres/hour. Lesser or greater air flow rates can lead to ineffective operation.

In an alternative embodiment with a 151 mm. throat, the free air delivered should be in the range 42 to 77 cubic metres/hour.

In a modification, the apertures 16 around the throat may be provided by the pores of porous material. For example, a collar insert of a suitable porous plastics material may be located in position around the throat covering apertures such as aperture 16 in the illustrated device.

The device is found in use to be reasonably simple to manufacture, robust, stable in varying liquid currents and circulation patterns and, of prime importance, to be highly effective at setting up and maintaining a good strong circulation pattern in the liquid to be treated. Moreover the device is found to be effective in water having a depth of 1.2 metres or even somewhat less, which is the order of depth favoured for fish farming tanks. The device is found to give a good Cs depth model, Cs being the saturation concen tration of the gas phase in the liquid phase for a particular depth. The rate of gas transfer depends on the dissolved gas (e.g.

oxygen) deficit and, since Cs is proportional to pressure and thus to depth, the gas transfer increases for higher effective values of Cs.

The device is also found to give a synergistic effect when used in conjunction with a top or surface aerator device, the combined rate of gas transfer being greater than would be expected from tests on the two devices used separately.

WHAT WE CLAIM IS: 1. A device for the gasification of liquid comprising a horizontal hollow ring member, said member having a gas inlet into said hollow and an inwardly facing surface of said ring which bounds a vertical central liquid passageway, said surface including an apertured intermediate portion bounding a throat in said passageway, whereby in operation gas within the hollow is emitted through said apertures into said throat to form bubbles in the liquid, wherein said ring member includes at least two legs bounding liquid entry passageways therebetween, said entry passageways communicating with the lower end of said central liquid passageway, whereby said device in operation can stand on the base of a liquid treatment vessel containing relatively shallow liquid to be gasified.

2. A device as claimed in claim 1 wherein the height of said ring member including said legs is less than its diameter.

3. A device as claimed in claim 1 or claim 2 wherein the total cross-sectional area for liquid flow through said entry passageways is substantially greater than the crosssectional area of said throat.

4. A device as claimed in any one of claims I to 3 wherein three said legs are provided. defining three said liquid entry passageways therebetween.

5. A device as claimed in any one of claims I to 4 wherein said legs are equally spaced circumferentially of the ring member.

6. A device as claimed in any one of claims I to 5 wherein both the outer surface of the ring member and said inwardly facing surface diverge away from one another downwardly from the top of the ring member to an equatorial region including said throat, and then converge towards one another from said equatorial region down to the top of said legs.

7. A device as claimed in claim 6 wherein said convergence continues uninterruptedly as a smooth curve down both the outward and inward facing surfaces of said legs.

8. A device as claimed in claim 6 or claim 7 wherein said ring member is formed in two moulded parts seamed around said equatorial region.

9. A device as claimed in any one of claims 1 to 8 wherein said legs are hollow.

10. A device as claimed in claim 9 wherein said legs are filled with a dense material to an extent sufficient to provide an average density for the whole ring member device greater than that of water.

11. A device as claimed in any one of claims 1 to 10 wherein said gas inlet is in the top surface of said ring member.

12. A device for the gasification of liquids substantially as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. tration of the gas phase in the liquid phase for a particular depth. The rate of gas transfer depends on the dissolved gas (e.g. oxygen) deficit and, since Cs is proportional to pressure and thus to depth, the gas transfer increases for higher effective values of Cs. The device is also found to give a synergistic effect when used in conjunction with a top or surface aerator device, the combined rate of gas transfer being greater than would be expected from tests on the two devices used separately. WHAT WE CLAIM IS:

1. A device for the gasification of liquid comprising a horizontal hollow ring member, said member having a gas inlet into said hollow and an inwardly facing surface of said ring which bounds a vertical central liquid passageway, said surface including an apertured intermediate portion bounding a throat in said passageway, whereby in operation gas within the hollow is emitted through said apertures into said throat to form bubbles in the liquid, wherein said ring member includes at least two legs bounding liquid entry passageways therebetween, said entry passageways communicating with the lower end of said central liquid passageway, whereby said device in operation can stand on the base of a liquid treatment vessel containing relatively shallow liquid to be gasified.