GB2413506A - A liquid adsorbing apparatus - Google Patents

Abstract

A method of filtering using a filtering apparatus 10 of the kind including a chamber 12 into which a liquid mixture is introduced above a separating member 15, the liquid mixture including first and second liquids, the first liquid having a greater density than the second liquid, the separating member 5 in use, adsorbing second liquid from the mixture, and the chamber 2 having an outlet 14 from which separated first liquid is in use, discharged, characterised in that the method includes moving the separating member 15 downwardly in the chamber 12 as the separating member 15 adsorbs second liquid, at a rate which is independent or at least not substantially independent of the mass of second liquid adsorbed.

Description

241 3506

L

Title: Method of Filtering

Description of Invention

This invention relates to a method filtering using a filtering apparatus of the kind including a chamber into which a liquid mixture is introduced above a separating member, the liquid mixture including first and second liquids, the first liquid having a greater density than the second liquid, the separating member in use, adsorbing second liquid from the mixture, and the chamber having an outlet from which separated first liquid is in use, discharged.

A prior proposal of such a filtering apparatus is described in previous patent application GB-A-2350571.

It will be appreciated that in use of such a filtering apparatus, the second liquid will tend to float on the first liquid in the chamber by virtue of its lesser density, thus forming a first and second liquid interface layer. The separating member adsorbs the second liquid primarily at the interface layer, although some second liquid may also be adsorbed by the separating member as the liquid mixture flows through the separating member.

In the previous proposal, the position of the separating member in the chamber thus depends substantially upon the mass of second liquid adsorbed by the separating member; as the separating member adsorbs more second liquid, the separating member sinks downwardly in the chamber to present a fresh adsorbing part of the separating member at the interface layer. There is described in the previous proposal, the inclusion in the separating member of a float, or alternatively the use of some other device, such as a spring, to prevent the separating member sinking too quickly in the chamber.

Of course, for most efficient use of the separating member, it is desirable that the separating member becomes saturated with adsorbed second liquid. The float/spring in the previous proposal were efforts to ensure that the separating member became saturated with adsorbed second liquid at the level of the interface layer in the chamber, because below the interface layer, there tends to be little or no more second liquid to adsorb.

However it will be appreciated that depending on the flow of the liquid mixture into the chamber, there are different requirements to ensure separating member saturation at the interface layer. In high flow conditions, the flowing liquid will impose a high drag force on the separating member through which, and possibly around which too, the liquid is flowing as the liquid passes from the inlet to the outlet of the chamber; in lower flow conditions, a lower drag force will be imposed. Thus relying on the mass of adsorbed second liquid to govern the position of the separating member in the chamber, can, in changing conditions, result in the separating member not becoming saturated with adsorbed second liquid at the interface layer.

Of course if the buoyancy of the float or spring force is increased to counter high drag forces, e.g. by increasing the area of the float, it may be the case that the separating member will not lower in the chamber in low flow conditions as the increase in mass of the separating member as it becomes saturated at the second liquid level will be insufficient to weigh down the separating member, and after saturation at the interface layer, the separating member will be unable to ffilfil its primary role of separating the liquids.

According to a first aspect of the invention we provide a method of filtering using a filtering apparatus of the kind including a chamber into which a liquid mixture is introduced above a separating member, the liquid mixture including first and second liquids, the first liquid having a greater density than the second liquid, the separating member in use, adsorbing second liquid from the mixture, and the chamber having an outlet from which separated first liquid is in use, discharged, characterised in that the method includes moving the separating member downwardly in the chamber as the separating member adsorbs second liquid, at a rate which is independent or at least substantially independent of the mass of second liquid adsorbed.

In its simplest form, the method according to the invention may include exposing a first part of the separating member to the second liquid at the interface layer, and as the first part of the separating member becomes saturated with second liquid, lowering the separating member in the chamber so that a fresh second part of the separating member is exposed to the second liquid at the interface layer.

The separating member may be constrained in a position in the chamber to expose the first part of the separating member to the second liquid, and may be constrained in a position to expose the second part of the separating member to the second liquid at the interface layer, whereby the separating member is lowered in step by step at intervals.

In a method according to the invention, the method may include lowering the separating member step by step at intervals, manually or preferably by an actuating device, the intervals between lowering the separating member being determined in accordance with the actual or a predicted flow rate of the liquid mixture through the separating member.

In each case, the separating member may be lowered by an amount depending on the average thickness or predicted thickness of the interface layer between lowerings of the separating member, or depending upon the actual thickness when the separating member is to be lowered.

In a second method according to the invention, the method may include lowering the separating member downwardly continuously at a rate determined in accordance with the actual or a predicted flow rate of the liquid mixture through the separating member.

In each method, where an actuating device is employed, this may include an actuator, such as an electrically operated actuator, external to the chamber, with there being a linkage or transmission to the separating member so that the actuator may positively move the separating member downwardly in the chamber.

In each of the methods of the invention so far described, the use of a float or spring as with the prior proposal described, is not required, as the position of the separating member in the chamber is controlled manually or by the actuator device. Thus there is scope for providing a separating member in the chamber with a greater volume than for example where a float is required, and so the separating member for its size is thus able to adsorb more second liquid than a comparably sized separating member with a float. Thus the life of the separating member before it becomes entirely saturated with second liquid and requires replacement, can be prolonged.

In another method according to the invention though, the separating member may include a float which is made of a material which degrades when the material is contacted by the first and/or second liquid, the method including permitting the first and/or second liquid to degrade the float, e.g. at the level of the interface layer of the first and second liquids in the chamber, whereby the buoyancy of the float decreases as the float degrades, so that the separating member will move downwardly in the chamber.

Of course in this method, as the amount of second liquid adsorbed by the separating member increases, this will increase the mass of the separating member. To reduce the effect of the increasing mass which will tend to lower the separating member in the chamber, preferably the float at least before the separating member has adsorbed second liquid, has a buoyancy which is substantially greater than that required to support the mass of the separating member in the chamber such that a lower end of the separating member is located at the interface layer.

Thus by providing a float which at least initially has sufficient buoyancy, and provided that the float material is sufficiently resistant to the first and/or second liquid such that the float material degrades only at an appropriate rate, the separating member may adsorb sufficient second liquid at the interface layer so as to become saturated, at a rate which corresponds to the rate at which the float material degrades and the buoyancy of the separating member decreases, so that the separating member moves downwardly in the chamber at a rate which largely is independent of the mass of adsorbed second liquid or at least is not dependent upon the mass of adsorbed second liquid.

In any event, whereas in high flow conditions, where the rate of second liquid saturation may exceed the rate of degradation of the float and thus the efficiency of separation of the first and second liquids may be compromised, the first and/or second liquid will continue to degrade the float material and so, in subsequent lower flow conditions, the separating member will again lower.

In any event, in higher flow conditions, the amount of second liquid at the interface layer will increase, and thus the rate of degradation of the float material will increase, and the mass of the separating member due to increased adsorption of second liquid will increase, these factors tending to lower the separating member at an increased rate, thus at least partially balancing the effect of high flow conditions.

_According to a second aspect of the invention we provide a filtering apparatus including a chamber into which a liquid mixture is introduced above a separating member, the liquid mixture including first and second liquids, the separating member in use, adsorbing second liquid from the mixture, and the chamber having an outlet from which separated first liquid is in use, discharged, characterized in that means are provided to move the separating member downwardly in the chamber as the separating member adsorbs second liquid, at a rate which is independent or at least substantially independent of the mass of second liquid adsorbed.

The filtering apparatus may have any of the features of the filtering apparatus specified for use in the first aspect of the invention.

Embodiments of the invention will now be described with reference to the accompanying drawings in which: FIGURE 1 is an illustrative side view of a first filtering apparatus which may be operated by a method in accordance with the invention; FIGURE 2 is an illustrative side view of a second filtering apparatus which may be operated by a method in accordance with the invention.

Referring first to figure 1, a filtering apparatus 10 includes a chamber 12 having an inlet 13 for a liquid mixture of first and second liquids, of which the first liquid has a higher density than the second liquid, and an outlet 14 from the chamber 12 for first liquid, e.g. oil and water respectively e.g. condensate from an air compressor or like machine.

Between the inlet 13 and the outlet 14 the apparatus 10 includes a separating member IS. The liquid mixture is introduced into the chamber 12 though the inlet 13 which is above the separating member 15, and is constrained by virtue of the separating member 15 extending across the entire area of the chamber 12, to pass through the separating member 1 S before liquid can be discharged from the chamber 12 from the outlet 14.

The oil in the liquid mixture has a lesser density than the water in the liquid mixture, and thus the oil will tend to float on the water at an interface layer which is indicated at 17, within the chamber 12. The separating member includes an oleophillic material such as polypropylene strands, or a blown polymer, which adsorbs oil but rejects the water. Thus the separating member adsorbs oil from the liquid mixture as the liquid mixture passes therethough, but primarily at the interface layer 17 where the lighter oil accumulates.

Thus primarily water is discharged from the outlet 14 of the chamber 12, and the discharged water may then be subject to fine filtering, for example in a further chamber 18, to remove any remaining oil, prior to discharging the water for example, to the environment. The liquid level in the chamber 15 may be controlled by the liquid level in the further chamber 18 where this is provided, or otherwise as required.

The separating member 15 is attached via a transmission rod 20 of an actuator device 21, to an externally located actuator of the device 21.

In use, the oil/water liquid mixture enters the chamber 12 via the inlet 13, and flows down through the separating member 15. The oil will tend to float on the water at the interface layer 17, and thus the separating member 15 will adsorb the oil at the interface layer predominantly, from the liquid mixture.

As the part of the separating member 15 at the interface layer 17 adsorbs more and more oil, eventually the part will become saturated and unable to adsorb more oil.

So that the filtering apparatus 10 can continue to separate the oil and water from the liquid mixture, it is necessary to move the separating member 1 S in the chamber 12 downwardly, so that a fresh part ofthe separating member 15 is positioned at the interface layer 17.

In accordance with the invention this may be achieved in different ways.

First, the actuator device 21 may include a timer, and at pre-set intervals, the actuator may be operated to lower the separating member 15 in steps. In the figure 1 example, the actuator of the device 21 may rotate the transmission rod 22 which may be male threaded and engaged with a female threaded fitting, as indicated at 23 which is fixed with respect to the separating member 15. In the example shown, the fitting 23 may be embedded in the oleophillic material of the separating member 15, but could be secured to a top surface part 24 and/or to a bottom surface part 25 of the separating member 15 or otherwise.

Thus as the actuator rotates the transmission rod 20 in an appropriate sense of rotation, the separating member 15 will be lowered in the chamber 15 to present a fresh part of the separating member 15 at the interface layer 17.

The pre-set intervals at which the separating member 1 S is lowered may be detemmined manually or by a processor 28, to correspond to the likely time between intervals during which the part of the separating member 15 present at the interface layer 17 is likely to become saturated with adsorbed oil.

For example, this may be determined empirically, and the controller 28 where provided may simply be arranged to lower the separating member 15 in steps at the empirically determined intervals, or where there is no controller 28, the separating member 15 may be lowered manually, e.g. using a push rod.

Also, the amount of downward movement may be determined empirically and effected manually, or by the actuator device 21.

Alternatively, the likely time between intervals during which the part of the separating member 15 present at the interface layer 17 is likely to become saturated with adsorbed oil, may be determined by calculation, for example by determining the flow rate or average flow rate of liquid mixture fed into the chamber 12 over a period of time, and determining the likely proportions of water to oil, thus to calculate a likely oil adsorption rate. By knowing the dimensions of the separating member 15 and particularly the area of the separating member 15 exposed to the liquid at the interface layer 17, a determination can be made of the likely time for a part of the separating member 15 to become saturated with adsorbed oil. Again movement of the separating member 15 may be effected manually, or by the actuator device 21 in accordance with the calculated expected adsorption rate.

In another arrangement, the actuating device 21 may lower the separating member 15 continuously at a rate which may be determined empirically or by calculation, to correspond to the rate of absorption of the oil.

If desired, the filtering apparatus 10 may include a flow rate sensor 30, for example to provide an input to the controller 28 which is indicative of liquid mixture flow rate into the chamber 12 (although the flow rate of residual water from the outlet 14 could instead be sensed), and a sensor 32 may be provided to provide an input to the controller 28 indicative of the likely concentration of oil in the liquid mixture. For example such a sensor 32 could be an optical sensor.

In yet another example, a flow rate sensor 30 may be provided, but the likely relative proportions of oil and water in the liquid mixture may be indicated to the controller 28 by a manual input device, depending upon an analysis of liquid mixture.

In a modified apparatus 10, instead of the actuator of the actuator device 21 driving a threaded transmission rod 20, any other suitable transmission or linkage arrangement might be used, so that the actuator may be located exteriorly of the chamber 12, although the whole actuator device 21 could be located within the chamber 12 as required.

Where the separating member 15 is moved downwardly in steps, the amount of downward movement may depend on the average measured or predicted thickness of the interface layer 17 between lowerings of the separating member 15.

Also, if desired a sensor may be provided to sense the saturated fluid of adsorbed liquid in the separating member and/or the position of the separating member 15 in the chamber 12, the sensor providing an input to the controller 28 which responds when the saturated liquid has reached a threshold level to provide an audible or visual warning, locally to the apparatus 10 or remotely, that the separating member 15 requires changing.

In figure 2 a different apparatus 10 is shown, but like parts to those of the filtering apparatus 10 of figure 1 are labelled by the same references.

In the figure 2 arrangement, there is no actuating device 21.

The separating member 15 includes a float 35 the buoyancy of which decreases as the float 35 is exposed to the less dense second liquid in the liquid mixture, as the second liquid degrades the float 35.

This example is particularly applicable where the float 35 is made of a material such as polystyrene and the second liquid to be separated from the first liquid e.g. water in the liquid mixture, is for example or contains, Polyalkaline Glycol ("PAG"), which is a common constituent of condensate from an air compressor which utilises a particular kind of lubrication oil. The PAG degrades polystyrene, and the longer the PAG is in contact with the polystyrene the more profound the effect.

Thus as in the present case where the polystyrene performs as a float, as the float 35 is exposed to the PAG, the buoyancy of the float 35, and hence of the separating member 15 in which the float 35 is provided, will decrease.

In figure 2, the degradation ofthe float 35 which has been exposed to the PAG, i.e. the part 36 of the float 35 below the interface layer 17, is exaggerated for the purposes of illustration. The original float 35 shape is indicated by dotted lines.

Thus the separating member 15 will lower in the chamber 12 as the buoyancy of the separating member 15 decreases, at a rate largely dependent upon the rate of degradation of the float 35. However to offset the effect of the increasing mass of the separating member 15 as a result of adsorbed PAG, desirably the buoyancy of the float 35 and hence of the separating member 15, at least before any second liquid is adsorbed, is substantially greater than is required to support the separating member 15 in the chamber 12 at a position in which its lowest surface part 25 is at the interface layer 17. Preferably the float is sufficiently buoyant prior to any degradation, that the separating member 15 cannot move downwardly in the chamber 12 only as a result of its mass increasing as the part of the separating member 15 at the interface layer 17 becomes saturated by adsorbed liquid.

In each embodiment, the rate of lowering of the separating member 12 in the chamber 12 is wholly independent (as with the examples described with reference to figure 1), or at least substantially independent, and in each case not wholly dependent, on the mass of adsorbed liquid.

In each example, even if the separating member 15 is lowered in the chamber 12 at a rate less than the rate of adsorption of the liquid by the separating member 15, for example where there is a temporary higher than expected flow of liquid mixture into the chamber 12, although the part of the separating member 15 then exposed to the second liquid at the interface layer 17 may become saturated with second liquid, subsequently, when the flow rate has decreased and the separating member IS has been further lowered, the separating member 15 may again function to separate the first and second liquids.

Various modifications may be made without departing from the scope of the invention.

For example, although the invention has been described in relation to an apparatus 10 for removing oil, or second liquid containing PAG, from a first liquid being water, the invention may be used to separate other first and second liquids where the first liquid is denser than the second liquid.

Although in the method of the invention the PAG or other second liquid degrades the float 35, in another embodiment where different liquids/materials may be involved, the first andlor the second liquid may degrade the float 35 material.

The chamber 12 need not be of the shape and configuration shown which is purely exemplary, but could be of any desired size and shape, with the separating member 15 configured appropriately so that liquid mixture introduced above the separating member 15 is constrained to flow through the separating member 15 to the outlet 14 beneath.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (16)

1. A method of filtering using a filtering apparatus of the kind including a chamber into which a liquid mixture is introduced above a separating member, the liquid mixture including first and second liquids, the first liquid having a greater density than the second liquid, the separating member in use, adsorbing second liquid from the mixture, and the chamber having an outlet from which separated first liquid is in use, discharged, characterised in that the method includes moving the separating member downwardly in the chamber as the separating member adsorbs second liquid, at a rate which is independent or at least substantially independent of the mass of second liquid adsorbed.

2. A method according to claim 1 wherein a first part of the separating member is exposed to the second liquid at the interface layer, and as the first part of the separating member becomes saturated with second liquid, the method including lowering the separating member in the chamber so that a fresh second part of the separating member is exposed to the second liquid at the interface layer.

3. A method according to claim 2 wherein the method includes constraining the separating member in a position in the chamber to expose the first part of the separating member to the second liquid, lowering the separating member and constraining the separating member in a position to expose the second part of the separating member to the second liquid at the interface layer, whereby the separating member is lowered in step by step at intervals.

4. A method according to claim 3 wherein the separating member is lowered in steps manually, the intervals between lowering the separating member being determined in accordance with the actual or a predicted flow rate of the liquid mixture through the separating member.

5. A method according to claim 3 wherein the separating member is lowered in steps by an actuating device, the intervals between lowering the separating member being determined in accordance with the actual or a predicted flow rate of the liquid mixture through the separating member.

6. A method according to any one of claims 2 to 5 wherein the separating lO member is lowered by an amount depending on the average thickness or predicted thickness of the interface layer between lowerings of the separating member or depending upon the actual thickness when the separating member is to be lowered.

7. A method according to claim 1 wherein the method includes lowering the separating member downwardly continuously at a rate determined in accordance with the actual or a predicted flow rate of the liquid mixture through the separating member, using an actuating device.

8. A method according to claim 5 or claim 7 or claim 6 where dependent upon claim 5, wherein the actuating device includes an actuator external to the chamber, with there being a linkage or transmission to the separating member so that the actuator may positively move the separating member downwardly in the chamber.

9. A method according to claim 9 wherein the actuator of the actuating device is an electrically operated actuator.

10. A method according to claim 1 wherein the separating member includes a float which is made of a material which degrades when the material is contacted by the first and/or second liquid, the method including permitting the first and/or second liquid to degrade the float, whereby the buoyancy of the float decreases as the float degrades, so that the separating member will move downwardly in the chamber.

11. A method according to claim 11 wherein the float, at least before the separating member has adsorbed second liquid, has a buoyancy which is substantially greater than that required to support the mass of the separating member in the chamber.

12. A method of filtering substantially as hereinbefore described with reference to the accompanying drawings.

13. A filtering apparatus including a chamber into which a liquid mixture is introduced above a separating member, the liquid mixture including first and second liquids, the first liquid having a greater density than the second liquid, the separating member in use, adsorbing second liquid from the mixture, and the chamber having an outlet from which separated first liquid is in use, discharged, characterized in that means are provided to move the separating member downwardly in the chamber as the separating member adsorbs second liquid, at a rate which is independent or at least substantially independent of the mass of second liquid adsorbed.

14. An apparatus according to claim 14 having any of the features of the filtering apparatus specified for use in the method of any one of claims 1 to 13.

15. A filtering apparatus substantially as hereinbefore described with reference to and/or as shown in the accompanying drawings.

16. Any novel feature or novel combination of features described herein and/or as shown in the accompanying drawings.