GB2526872A

GB2526872A - Apparatus for de-aerating a liquid

Info

Publication number: GB2526872A
Application number: GB1410051.5A
Authority: GB
Inventors: Sean Dobbs
Original assignee: CDE Global Ltd
Current assignee: CDE Global Ltd
Priority date: 2014-06-06
Filing date: 2014-06-06
Publication date: 2015-12-09
Anticipated expiration: 2034-06-06
Also published as: GB201410051D0; GB2526872B; GB2528753B; GB201508920D0; GB2528753A

Abstract

An apparatus for de-aerating a liquid comprises an elongate channel having at least one liquid inlet at a first end thereof and at least one liquid outlet at a second end, a weir being defined within the channel between the inlet(s) and the outlet(s) wherein liquid is constrained to flow over the weir between the inlet(s) and the outlet(s). Suitably, the channel is defined within an elongate housing 10 having a bottom wall 12, first and second end walls 14, 16 and first and second side walls 18, 20 extending between the end walls. The weir may be defined by an intermediate wall 30 extending from the first end wall to the second end wall such that the channel is divided into first and second sections 32, 34, wherein the first section communicates with a liquid inlet(s) and the second section communicates with the liquid outlet(s). Preferably, the intermediate wall has a convoluted profile in plan view, such as a zig-zag profile. A method of de-aerating a liquid is also claimed.

Description

Apparatus for De-aeratinq a liquid This invention relates to an apparatus for de-aerating a liquid and in particular to an apparatus for de-aerating water in a waste water treatment system.

Waste water streams containing entrained solid impurities and contaminants in suspension are produced from numerous quarrying, mining, chemical or industrial processes. It is often desirable to reuse such water, particularly in regions prone to water shortages.

Before the waste water can be re-used, the impurities and contaminants must be removed from the water. This is typically done by passing the water into a settling tank wherein the fines are able to settle out under the action of gravity, typically after adding a flocculating agent to which the fines bind to bring them out of suspension and/or by chemically treating the waste water.

However, waste water often contains a lot of entrained air, due to turbulence and other aeration effects of the washing or grading processes from which the waste water is produced. This entrained air inhibits the fast and effective settlement of flocculated solids in a settling tank.

Therefore an object of the present invention is to provide a cost effective and reliable means for de-aerating a liquid upstream of a treatment process, in particular a settling tank.

According to a first aspect of the present invention there is provided an apparatus for de-aerating a liquid comprising an elongate channel having at least one liquid inlet at a first end thereof and at least one liquid outlet at a second end, a weir being defined within the channel between the at least one liquid inlet and the at least one liquid outlet wherein liquid is constrained to flow over the weir between the at least one liquid inlet and the at least one liquid outlet.

In a preferred embodiment said channel may be defined within an elongate housing having a bottom wall, first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the first section communicating with said at least one liquid inlet and the second section communicating with said at least one liquid outlet.

Preferably said intermediate wall has a convoluted profile in plan view, maximising the length of the weir. The intermediate wall may have a zig-zag profile in plan view.

Preferably a first portion of the intermediate wall adjacent said at least one liquid inlet has a height greater than the remainder of the intermediate wall.

The housing may include a cover or upper wall, said first portion of the intermediate wall abutting or adjoining said cover or upper wall. Vent apertures may be provided in said cover or upper wall for venting air therefrom.

Preferably a liquid inlet is provided in the first side wall of the housing adjacent the first end wall, preferably adjacent an upper edge of the first side wall, a liquid outlet being provided in the second side wall of the housing adjacent the second end wall, preferably adjacent the bottom wall of the housing.

A further liquid inlet may be provided in the first end wall of the housing adjacent the first side wall, said further liquid inlet communicating with the first section of the channel.

In one embodiment a purge outlet is provided in the second end wall of the housing adjacent the first side wall, said purge outlet communicating with the first section of the channel and being associated with a valve to periodically bleed liquid from the first section of the channel adjacent the second end wall.

According to a further aspect of the present invention there is provided a method of de-aerating a liquid comprising passing the liquid through an elongate channel having a weir being defined therein such that the liquid is constrained to flow over the weir between at least one liquid inlet and at least one liquid outlet of the channel.

Preferably the height of the liquid within the channel is maintained to be just greater than the height of the weir.

In one embodiment, the method comprises passing the liquid through an elongate housing defining said channel, said housing having a bottom wall! first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the liquid being passed into said first section via at least one liquid inlet at or adjacent said first end wall and passing over the weir into said section to leave the channel via at least one liquid outlet at or adjacent said second end wall.

The height of the intermediate wall adjacent said at least one liquid inlet may be greater than the height of the remainder of the wall to prevent the liquid from passing over the weir in the region of the at least one liquid inlet.

The method may further include the step of periodically removing liquid from the first section of the channel adjacent the second end wall of the housing to prevent the formation of a dead zone in such region, avoiding the problem of solids collection in such region.

An apparatus for de-aerating a liquid in accordance with an embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a perspective view of a water treatment system incorporating a de-aerating apparatus in accordance with an embodiment of the present invention; Figure 2 is a perspective view of the de-aerating apparatus of Figure 1; Figure 3 is a further perspective view of the apparatus of Figure 2; Figure 4 is a side view of the apparatus of Figure 2; Figure 5 is a part sectional perspective view of the apparatus of Figure 2; Figure 6 is a further part sectional perspective view of the apparatus of Figure 2; and Figure 7 is a part sectional side view of the apparatus of Figure 2.

Figure 1 illustrates a water treatment system incorporating a de-aerating apparatus in accordance with an embodiment of the present invention. The water treatment system shown in Figure 1 comprises a dosing and mixing apparatus for adding a flocculent and/or other chemicals to a waste water stream upstream of a settling tank.

In particular, Figure 1 shows a first chemical dosing stage 2 wherein a coagulant may be mixed with the waste water before passing to a second dosing stage 3, wherein the waste water is dosed with a flocculent before passing to flow passage 4 incorporating adjustable angle paddles 5 for hydraulic mixing before being fed to a settling tank. One or both of the dosing stages 2,3 may incorporate mixing paddles.

The de-aerating apparatus is provided to remove entrained air from the waste water upstream of the dosing and mixing apparatus. There is typically a lot of air entrained in waste water discharged from sand and aggregate washing and grading processes and other washing processes and this entrained air inhibits the fast and effective settlement of flocculated solids.

By removing air from the waste water prior to any chemical treatment, the effectiveness of the flocculent is enhanced, potentially allowing the use of a smaller settlement tank.

The de-aerating apparatus comprises an elongate chamber 10 having a bottom wall 12, first and second end walls 14,16 and first and second side walls 18,20 extending between said end walls 14,16, the chamber 10 defining a flow passage through which waste water is constrained to flow. A cover or lid 22 is provided for closing an upper side of the chamber 10.

A waste water inlet port 24 is provided in the first side wall 18 of the chamber 10, adjacent the first end wall 14, preferably adjacent an upper edge of the first side wall 14. An outlet port 26 is provided in the second side wall 20 of the chamber adjacent the second end wall 16, preferably adjacent the bottom wall 12 of the chamber 10.

A further inlet port 28 may be provided in the first end wall 14 of the chamber 10, adjacent the first side wall 18. The further inlet port 28 may receive waste water from a separate source, for example the centrate from a centrifuge.

Preferably the chamber 10 is mounted with a slight downward slope between the first and second ends 14,16 thereof to encourage flow of waste water through the chamber 10 from the first end 14 to the second end 16.

An intermediate wall 30 extends from the first end wall 14 of the chamber 10 to the second end wall 16 of the chamber 10, the intermediate wall 30 being of a height less than the first and second side walls 18,20 and first and second end walls 14,16 of the chamber 10, such that the intermediate wall 30 defines a weir dividing the chamber into first and second sections 32,34, over which weir waste water must flow to pass from the first section 32 of the chamber into the second section 34 of the chamber 10 to reach the outlet port 26. The waste water inlet port 24 (and the further inlet port 28 where provided) communicates with the first section 32 of the chamber 10 while the outlet port 26 communicates with the second section 34 of the chamber 10.

As best seen from Figures 5 and 6, the intermediate wall 30 has a convoluted profile, more preferably a zig-zag profile, in plan view, maximising the effective length of the weir. As can be seen from Figure 7, the height of the intermediate wall may gradually increase from the first end 14 to the second end 16 of the chamber 10 to compensate for the slope of the chamber 10 so that the upper edge of the intermediate wall 30 is remains substantially horizontal.

As it passes over the weir, the waste water is reduced into a thin ribbon of water, with effectively laminar flow and low turbulence, promoting the release of entrapped air bubbles.

A first portion 36 of the intermediate wall 30 directly adjacent the inlet pod 24 has a height greater than the remainder of the intermediate wall 30, preferably substantially equal to the height of the first and second side walls 18,20 and first and second end walls 14,16, to prevent waste water from passing over the weir immediately adjacent the inlet port 24. This is because water entering the chamber from the inlet port 24 will initially have relatively high turbulence. The first portion 26 of the wall 30 may include an upper wall 37 extending from an upper edge of said first portion 26 of the wall to extend to abut the first end wall 14 and first side wall 18 of the chamber 10 to effectively enclose an inlet region of the chamber 10.

Vent apertures 38,40 may be provided in the cover 22 of the chamber 10 for venting air therefrom. As shown in Figure 2. the vent apertures 38,40 may be provided adjacent corner regions of the chamber 10, preferably adjacent the second end wall 16 of the chamber 10 in the first section 32 of the chamber 10 and adjacent the first end wall 14 of the chamber 10 in the second section 34, such regions comprising effective dead spaces. These positions reduce the possibility of waste water escaping from the vent apertures 38,40.

The provision of a long weir over which the waste water must flow massively reduces the cross sectional area of the water as it passes over the weir and hence makes it much easier for the air bubbles to escape by reducing the hydraulic retention effect. The water flows up over the weir and drops down the other side.

This change in directions encourages the bubbles to carry on in the upward direction. The weir also reduces the flow rate of the waste water. Moving at a slower velocity gives the air a longer time frame to escape from the water. More laminar (less turbulent) flow, due to the reduced flow and the flow conditioning' caused by the weir also makes it easier for air to escape.

A shown in Figures 5 and 6, a purge outlet 42 is provided in the second end wall 16 of the chamber 10 adjacent the first side wall 18, said purge outlet 42 communicating with the first section 32 of the chamber. The purge outlet 42 may communicate with a drain or bypass controlled by a valve to periodically bleed liquid from the first section 32 of the chamber adjacent the second end wall 16 into said drain or bypass. Such region of the chamber comprises a dead space where waste water can stagnate, possibly resulting in the deposition of solids in such region, unless this region is frequently purged via said purge outlet 42.

The invention is not limited to the embodiment(s) described herein but can be amended or modified without departing from the scope of the present invention.

Claims

Claims 1. An apparatus for de-aerating a liquid comprising an elongate channel having at least one liquid inlet at a first end thereof and at least one liquid outlet at a second end, a weir being defined within the channel between the at least one liquid inlet and the at least one liquid outlet wherein liquid is constrained to flow over the weir between the at least one liquid inlet and the at least one liquid outlet.
2. An apparatus as claimed in claim 1, wherein said channel is defined within an elongate housing having a bottom wall, first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the first section communicating with said at least one liquid inlet and the second section communicating with said at least one liquid outlet.
3. An apparatus as claimed in claim 2, wherein said intermediate wall has a convoluted profile in plan view, maximising the length of the weir.
4. An apparatus as claimed in claim 3, wherein said intermediate wall has a zig-zag profile in plan view.
5. An apparatus as claimed in any of claims 2 to 5, wherein a first portion of the intermediate wall adjacent said at least one liquid inlet has a height greater than the remainder of the intermediate wall.
6. An apparatus as claimed in claim 5, wherein the housing includes a cover or upper wall, said first portion of the intermediate wall abutting or adjoining said cover or upper wall.
7. An apparatus as claimed in claim 6, wherein vent apertures are provided in said cover or upper wall for venting air therefrom.
8. An apparatus as claimed in any of claims 2 to 7, wherein a liquid inlet is provided in the first side wall of the housing adjacent the first end wall, a liquid outlet being provided in the second side wall of the housing adjacent the second end wall.
9. An apparatus as claimed in claim 8, wherein a further liquid inlet is provided in the first end wall of the housing adjacent the first side wall, said further liquid inlet communicating with the first section of the channel.
10. An apparatus as claimed in any of claims 2 to 9, wherein a purge outlet is provided in the second end wall of the housing adjacent the first side wall, said purge outlet communicating with the first section of the channel and being associated with a valve to periodically bleed liquid from the first section of the channel adjacent the second end wall.
11. An apparatus as claimed in any preceding claim, wherein the weir increases in height from the first end of the channel to the second end of the channel to allow the channel to slope downwardly from the first end to the second end while the upper edge of the weir remains substantially horizontal.
12. A method of de-aerating a liquid comprising passing the liquid through an elongate channel having a weir being defined therein such that the liquid is constrained to flow over the weir between at least one liquid inlet and at least one liquid outlet of the channel.
13. A method as claimed in claim 12, wherein the height of the liquid within the channel is maintained to be just greater than the height of the weir.
14. A method as claimed in claim 12 or claim 13, wherein the method comprises passing the liquid through an elongate housing defining said channel, said housing having a bottom wall] first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the liquid being passed into said first section via at least one liquid inlet at or adjacent said first end wall and passing over the weir into said section to leave the channel via at least one liquid outlet at or adjacent said second end wall.
15. A method as claimed in claim 14, wherein the height of the intermediate wall adjacent said at least one liquid inlet is greater than the height of the remainder of the wall to prevent the liquid from passing over the weir in the region of the at least one liquid inlet.
16. A method as claimed in claim 14 or claim 15, including the step of periodically removing liquid from the first section of the channel adjacent the second end wall of the housing to prevent the formation of a dead zone in such region, avoiding the problem of solids collection in such region.
17. An apparatus for de-aerating a liquid substantially as described herein with reference to the accompanying drawings.
18. A method of de-aerating a liquid substantially as described herein with reference to the accompanying drawings.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS: Claims 1. An apparatus for de-aerating a liquid comprising an elongate channel having at least one liquid inlet at a first end thereof and at least one liquid outlet at a second end, a weir being defined within the channel between the at least one liquid inlet and the at least one liquid outlet wherein liquid is constrained to flow over the weir between the at least one liquid inlet and the at least one liquid outlet, said channel being defined within an elongate housing having a bottom wall, first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the first section communicating with said at least one liquid inlet and the second section is communicating with said at least one liquid outlet, wherein said intermediate wall has a convoluted profile in plan view, maximising the length oftheweir. (00 2. An apparatus as claimed in claim 1, wherein said intermediate wall has a zig-zag profile in plan view.3. An apparatus as claimed in any preceding claim, wherein a first portion of the intermediate wall adjacent said at least one liquid inlet has a height greater than the remainder of the intermediate wall.4. An apparatus as claimed in claim 3, wherein the housing includes a cover or upper wall, said first portion of the intermediate wall abutting or adjoining said cover or upper wall.5. An apparatus as claimed in claim 4, wherein vent apertures are provided in said cover or upper wall for venting air therefrom.6. An apparatus as claimed in any preceding claim, wherein a liquid inlet is provided in the first side wall of the housing adjacent the first end wall, a liquid outlet being provided in the second side wall of the housing adjacent the second end wall.7. An apparatus as claimed in claim 6, wherein a further liquid inlet is provided in the first end wall of the housing adjacent the first side wall, said further liquid inlet communicating with the first section of the channel.8. An apparatus as claimed in any preceding claim, wherein a purge outlet is provided in the second end wall of the housing adjacent the first side wall, said purge outlet communicating with the first section of the channel and being associated with a valve to periodically bleed liquid from the first section of the channel adjacent the second end wall.9. An apparatus as claimed in any preceding claim, wherein the weir increases in height from the first end of the channel to the second end of the channel to allow the channel to slope downwardly from the first end to the second end while the upper is edge of the weir remains substantially horizontal.10. A method of de-aerating a liquid comprising passing the liquid through an 0 elongate channel having a weir being defined therein such that the liquid is constrained to flow over the weir between at least one liquid inlet and at least one O 20 liquid outlet of the channel, wherein the method comprises passing the liquid through an elongate housing defining said channel, said housing having a bottom wall, first and second end walls and first and second side walls extending between said end walls, said weir being defined by an intermediate wall having a convoluted profile in plan view extending from the first end wall of the elongate housing adjacent said first end of the channel to the second end wall of the elongate housing adjacent said second end of the channel such that the weir divides said channel defined within the housing into first and second sections, the liquid being passed into said first section via at least one liquid inlet at or adjacent said first end wall and passing over the weir into said section to leave the channel via at least one liquid outlet at or adjacent said second end wall..11. A method as claimed in claim 10, wherein the height of the liquid within the channel is maintained to be just greater than the height of the weir.12. A method as claimed in claim 10 or claim 11, wherein the height of the intermediate wall adjacent said at least one liquid inlet is greater than the height of the remainder of the wall to prevent the liquid from passing over the weir in the region of the at least one liquid inlet.13. A method as claimed in any of claims 10 to 12, including the step of periodically removing liquid from the first section of the channel adjacent the second end wall of the housing to prevent the formation of a dead zone in such region, avoiding the problem of solids collection in such region.14. An apparatus for de-aerating a liquid substantially as described herein with reference to the accompanying drawings.15. A method of de-aerating a liquid substantially as described herein with reference to the accompanying drawings.