GB2157587A - Liquid deaerating system - Google Patents

Abstract

A liquid deaerating system has a deaerating tank (1) housing an upper spray type deaerator (2) and at least one lower direct-contact packed deaerator (3,3A) with a seal arrangement (5) between each pair of adjacent vertically spaced deaerators and incorporating, or having downstream thereof in terms of liquid flow, liquid distribution means (14). A collection area (4) is disposed below the packed deaerator, or the lowest one if more than one is provided, for deaerated liquid, and a vacuum maintaining system (31) is provided for venting the extracted air, other gases and water vapour. The seal arrangement may be an imperforate barrier (5) with at least one down-comer (6) allowing downward flow of liquid between the vertically-spaced deaerators. <IMAGE>

Description

SPECIFICATION Liquid deaerating system This invention relates to a liquid deaerating system and it is an object of the present invention to provide a liquid deaerating system which is both compact and efficient.

According to the present invention there is provided a liquid deaerating system comprising a deaerating tank housing an upper spray type deaerator and at least one lower direct-contact packed deaerator with therebetween a seal arrangement incorporating, or having downstream thereof in terms of liquid flow, liquid distribution means, a collection area below the packed dearator, or the lowest thereof is more than one is provided, a collection area for deaerated liquid, and a vacuum maintaining system for venting the extracted air, other gases, and water vapour.

There are preferably no more than two directcontact packer deaerators, one below the other with between same a seal arrangement incorporating, or having downstream of the upper packed deaerator in terms of liquid flow, liquid distribution means.

Preferably, the seal arrangement is an imperforate barrier with at least one down-comer allowing downward flow of liquid between vertically spaced deaerators.

The purpose of the seal arrangements is to permit the various deaerating stages to be operated at different pressures, the operational pressure of each stage being different and usually lower than that immediately above.

Preferably, each down-comer has an associated seal pan into which the liquid flows before flowing over the edge of same downwards towards the next deaerator.

The liquid distribution means may comprise spaced orifices spread over the area of the seal barrier.

It may also consist of an arrangement of spaced perforated pipes extending over the area of the deaerator located below same.

Alternatively, the liquid distribution means comprises below the seal arrangement a sieve arrangement incorporating gas risers.

The sieve arrangement is preferably a series of spaced sieve plates, the spaces between the sieve plates constituting the gas risers. The gas risers may be of any convenient geometry. They may, for example, be constituted by a number of spaced cylinders.

If more than one packed deaerator is provided then it is preferred that the down-comer for the or each lower packed deaerator has an upper sieve.

A packed deaerator is, as is well known to those skilled in the art, filled, or substantially so, with rings, plastics components or equivalent to constrain the liquid to flow therethrough in a non-direct but random path.

It two or more packed deaerators are provided the or each lower packed deaerator may have its upper end closed by, a mesh grid or similar.

Means is, as is usual, provided for supplying liquid, such for example as sea water, to be deaerated to the tank, as is means for removing the deaerated liquid and means for venting the extracted air, other gases and water vapour.

According to a second aspect of the present invention there is provided a liquid deaerating system comprising a deaerating tank housing at least two deaerators with therebetween a combined seal and liquid distribution arrangement comprising an imperforate barrier traversed by at least one downcomer incorporating below the imperforate barrier an arrangement of spaced perforated liquid distributing pipes.

Preferably, the or each down-comer comprises inner and outer tubes with the inner tube being the inlet to the liquid distributing pipe arrangement.

With this combined seal and distribution arrangement if the lower deaerator is of the packed type then the top of this lower deaerator can be disposed much closer to the imperforate barrier than is usual. If the upper deaerator is of the packed type the down-comer of the lower deaerator can actually extend into the upper packed deaerator. The overall effect, however, irrespective of the deaerator types employed is to substantially reduce the height of the deaerator tank compared to htose employed in present deaerating systems.

An embodiment of the present invention will now be described, by way of example to the accompanying drawings, in which: Figure 1 is a diagrammatic view of a three stage spray,packed/packed, deaerating system; Figure 2 is a diagrammatic view showing the spray type deaerator with a preferred form of seal and liquid distribution arrangement; and Figure 3 is a diagrammatic perspective view of the arrangement shown in Figure 2.

The deaerating system for use especially but not exclusively in a water flood supply system comprises a cylindrical tank 1 housing in its upper region a conventional spray-type deaerator 2 and below same are located, in vertical array, two conventional direct-contact packed deaerators, 3, 3A.

A collection area for deaerated liquid below the bottom packed deaerator 3A is indicated at 4.

The construction and functioning of these deaerators 2 and 3, 3A are well known to those skilled in the art and will, therefore not be described.

Between the spray type deaerator and the upper packed deaerator 3 a combined seal arrangement and liquid distribution arrangement comprising a dished imperforate plate 5 which may, of course, be flat. Centrally of this plate 5 is a down-comer 6 comprising an outer tube 7 open at the bottom 8 and closed at the top 9 and spaced above the imperforate plate 5 as indicated at 10, and an inner tube 11 open at the top 12 and space downwardly from the closed top 9 of the outer tube 7. The inner tube 11 extends through the imperforate plate 5 and is spaced radially inwardly of the outer tube 7 to define an annular liquid flow passage 13 up which liquid flows to then flow down the inner tube 11.The bottom of the latter communicates with a main distribution pipe 14 under the imper forate plate 5 and from which extends from both sides an array of parallel branch pipes 15 spatially perforated or orificed along their lengths for controlled outflow of liquid over the whole area of packed deaerator 3.

A pressure balance pipe 6A extends from the top of the down-comer 6, i.e. just under the closed top 9 to below the main distribution pipe 14 and serves to prevent air-locking and/or siphoning.

With this arrangement, as can be seen from Figure 2, the spray pipes or manifolds 2A of the spray type deaerator 2 can be disposed alongside the down-comer 6 thus reducing the overall height occupied by these components.

Between the packed deaerators 3 and 3A is a seal arrangement comprising, in this instance, an imperforate plate 16 having a central cylindrical down-comer or communication tube 17 to permit downward flow of liquid.

Surrounding the down-comer 17 is a seal pan 18 into the bottom of which liquid flows before passing up over the top edge and out of the seal pan 18 in its downward flow.

Here is should be noted that the lower the deaerating stage, usually the lower the operational pressure whereby there is no lower impediment to downward liquid flow resulting from a lower deaerating stage operating at a higher pressure than that immediately above.

To ensure that the liquid is spread over the whole area of the packed deaerator 3A their is provided below the seal arrangement a series of spaced sieve plates 19, the spaced 20 therebetween acting as air or gas risers.

The down-comer 17 of the seal arrangement between packed deaerators 3 and 3A has at its upper end a grid 21.

The upper ends of the packed deaerators 3 and 3A may be closed by mesh grids and the lower end of the packed deaerator 3A is closed by a perforated packing support plate 22.

The down-comer 17 may extend slightly above the barrier or seal plate 16 so that there is always a layer of water on the top surface of the plate 5.

This also occurs with the combined arrangement as can be seen in Figure 2.

The sieve plates 19, as can be seen, are dished and operate with a layer of water therein.

The collection area 4 is connected by piping 12 via a pump 24 to a boiler or water flood supply 25.

In the embodiment shown of a boiler feed system a recirculatory branch pipe 26 is included to permit recirculation of the deaerated liquid should boiler demand decrease. With, for example, a water flood system the supply of water to the spray type deaerator 2 can be controlled, if wellhead demand varies, by a control valve 27 positioned in the supply line 28 from the water supply 29.

Valving 30 is provided in pipelines 23 and 26 to control the level of deaerated liquid in the collection area 4 and also to control recirculation and deaerated liquid demand.

A vacuum maintaining system 31 is connected to the tank 1 at each deaerating stage as indicated at 32, 32A and 32B and to the air, other gas and water vapour extraction or venting equipment 33 via piping 34.

In use of the aforesaid deaerating system liquid to be deaerated is fed from the supply 29 into the tank 1 where it is subjected to a first and major deaerating action by the spray type deaerator 2.

The partially deaerated liquid then flows downward through packed deaerators 3 and 3A where subsequent deaeration actions take place the liquid arriving at the collection area in a deaerated condition predetermined by the operational parameters set by the plant operator.

The downward flow and spread of the liquid is controlled by the combined seal and liquid distribution pipework between deaerators 2 and 3 and the seal arrangement and sieve plates between deaerators 3 and 3A as described above.

Claims (17)

1. A liquid deaerating system comprising a deaerating tank housing an upper spray type deaerator and at least one lower direct-contact packed deaerator with therebetween a seal arrangement incorporating, or having downstream thereof in terms of liquid flow, liquid distribution means, a collection area below the packed deaerator, or the lower thereof if more than one is provided, for deaerated liquid, and a vacuum maintaining system for venting the extracted air, other gases and water vapour.

2. A deaerating system as claimed in claim 1 comprising two direct-contact packed deaerators, one below the other with between same a seal arrangement incorporating, or having downstream of the upper packed deaerator in terms of liquid flow, liquid distibution means.

3. A deaerating system as claimed in claim 1 or 2 in which the seal arrangement is an imperforate barrier with at least one down-comer allowing downward flow of liquid between vertically-spaced deaerators.

4. A deaerating system as claimed in claim 3 in which each down-comer has an associated seal pan into which the liquid flows before flowing over the edge of same downwards towards the next lower dearator.

5. A deaerating system as claimed in claim 3 or 4 in which theliquid distribution means comprises spaced orifices spaced over the area of the seal barrier.

6. A deaerating system as claimed in any one of claims 1 to 4, in which the liquid distribution means comprises below the seal arrangement a sieve arrangement incorporating gas risers.

7. A deaerating system as claimed in claim 6, in which the sieve arrangement is a series of spaced sieve plates, the spaces between the sieve plates consistuting the gas risers.

8. A deaerating system as claimed in any one of claims 3 to 7 in which, where more than one packed dearator is provided, the down-comer for the or each lower packed deaerator has an upper sieve.

9. A deaerating system as claimed in claim 8, in which the or each lower packed deaerator has its upper end closed by a mesh grid or similar.

10. A deaerating system as claimed in any one of claims 1 to 9, in which the vacuum maintaining system is connected to the tank in the region of each deaerator by valved piping.

11. A deaerating system as claimed in any one of claims 1 to 10, in which a liquid supply is connected to the spray deaerator by valved piping.

12. A deaerating system as claimed in claim 11, in which the collection area is connected by valved piping to a boiler or other apparatus or location and by further valved piping to the valved supply piping for recirculatory purposes.

13. A deaerating system comprising a deaerating tank housing at least two dearators with therebetween a combined seal and liquid distribution arrangement comprising an imperforate barrier tranverse by at least one down-comer incorporating below the imperforate barrier an arrangement of spaced perforated liquid distributing pipes.

14. A deaerating system as claimed in claim 13 in which the or each down-comer comprises inner and outer tubes with the inner tube being the inlet to the liquid distributing pipe arrangement.

15. A deaerating system as claimed in claim 13 or 14 in which the upper deaerator is of the spray type with its spray pipes or manifolds disposed alongside the down-comer.

16. A deaerating system as claimed in claim 13 or 14 in which the upper dearator is of the packed type with the down-comer extending therein.

17. A deaerating system substantially as hereinbefore described with reference to the accompanying drawing.