APPARATUS FOR FILTERING AND COALESCING LIQUIDS

Abstract: An apparatus which can be used for removing contaminants from a liquid and for coalescing droplets of a liquid dispersed in another immiscible liquid, which comprises a casing (1) divided into two compartments by a substantially tubular fibrous filter (2), formed by fibres attached at each end supports (3) and (4), there being a liquid inlet (8) leading to one side of the fibrous filter and a liquid outlet (9) leading from the other side of the fibrous filter, one of the end supports being connected to an actuating rod (6) which can move the end support axially and rotatably relative to the other end support, the fibrous filter being supported by a cage assembly (10) comprising a plurality of rings located within the fibrous filter preferably in the form of two sets of rings (11), (13) which can either be connected to the end supports or free to move independently. The structure enables more vigorous and effective back-washing.

Description: Apparatus for Filtering and Coalescing Liquids The present invention relates to apparatus for filtering solids from liquids or for coalescing droplets of one liquid dispersed in another liquid. EP 207797 discloses apparatus for removing contaminants from a liquid. The apparatus comprises fibres connected at each end, to end supports, which may be moved away from or towards each other to place the fibres under tension or to relax any applied tension. The end supports can also be rotated relative to each other. The fibres are attached to the end supports so as to form a tube of fibres surrounding a central tubular core provided with perforations. The liquid to be treated passes across the fibres between the central core and an outer compartment surrounding the fibres. In use, the end supports are moved towards one another and rotated relative to one another to twist the fibres and to compress them against the perforated tube. A disadvantage of using perforated tubes is that they may impose a restriction on the flow through the apparatus thereby leading to an increased pressure drop if the rate of flow is to be sustained. EP 360601 discloses an apparatus for removing contaminants from liquids which addresses this problem by using a helical spring to provide adequate support for the tubular fibrous filter both during use and during the backwash procedure for removing the impurities from the apparatus. The radial strength of the helical spring is sufficient to support the fibres against the force exerted by the pressure differential in the bed of fibres forming the tubular filter as it contracts under the torsional stress applied by relative rotation of the end supports However, with larger sizes of equipment with greater throughputs, the strength of spring needed requires to be made of a wire of gauge of such weight that it becomes impractical. This is because, as the diameter increases for higher throughput, the radial force on the spring increases by the square of the diameter, thus as the size increases the spring design becomes uneconomic In order to overcome such problems, the helical spring could either be made of tubular design or made of lighter materials. However, this would result in substantially increased cost of manufacture. In practice, springs cannot be used at diameters greater than 250mm. With this structure the rotation of the ends against the torsion of the spring is always in the same direction so the fibres always are twisted in the same direction around the longitudinal axis of the apparatus. This can be disadvantageous in the backwashing procedure. It would be desirable therefore to provide an apparatus which overcame the above disadvantages and had sufficient radial strength to enable the filtration and coalescence to be performed at a higher throughput of liquid in an economic and efficient manner. In addition we now impose a more rigorous backwash routine on the filter elements in order to have a greater efficiency of backwashing. With the increased backwashing strength there is a much greater strain on the support and we have found that with a springs as the support there is a danger of fatigue failure. We have now found that replacing the helical spring with a cage configuration provides an apparatus which overcomes the aforementioned disadvantages of the helical spring. The apparatus of the present invention can also be used as a coalescer to cause drops or droplets of one liquid dispersed in another immiscible liquid to coalesce and thus be more easily separated. Coalescers are used to separate hydrocarbon oils from water, although they have been used to separate many other dispersions comprising two substantially immiscible liquids. The present invention provides an apparatus which can be used for removing contaminants from a liquid and for coalescing droplets of a liquid dispersed in another immiscible liquid, which apparatus comprises a casing divided into two compartments by a substantially tubular fibrous filter, the said fibrous filter being formed by fibres attached at each end to an end support, there being a liquid inlet leading to one side of the fibrous filter and a liquid outlet leading from the other side of the fibrous filter, the said end supports being moveable axially relative to each other and rotatable relative to each other about the longitudinal axis of the tubular fibrous filter, there being a cage assembly comprising a plurality of rings located within the fibrous filter adapted to support the fibres forming the fibrous filter. The cage assembly is preferably in contact with the fibres forming the fibrous filter to support the fibres so as to resist the inward movement of the fibres caused when the end supports are moved axially towards each other and rotated to twist the fibres; this movement tends to close the compartment surrounded by the tubular filter. One of the end supports is preferably connected to an actuating rod so that this end support can be moved axially towards and away from the other end support. This actuating rod can also rotate the end support to which it is connected relative to the other end support, about the longitudinal axis of the tubular fibrous filter. The cage assembly can consist of a series of rings, preferably arranged along a common axis. Optionally, the rings can be attached to either end support or remain unconnected. The cage can comprise one or more sets of rings connected to each other; in one embodiment the cage comprises two parts, each part consisting of a plurality of rings, being connected to a different end support so that as the end supports are moved closer or further apart, the two parts of the cage are also moved closer or further apart The gaps between the rings are preferably of a distance to give adequate support to the fibres without too great an effect on the flow of liquid through the filter element when the equipment is in operation. The rings forming the cage are preferably of the same diameter and can be made of any suitable material, e.g. stainless steel; optionally the rings can be of a hollow tubular construction. The rings forming the cage structure can, if necessary, be located in position by means of radially located supports and/or longitudinally arranged supports can be used. In one embodiment of the invention, the cage structure comprises two parts, each part consisting of several rings and can be the same or different in length. Each part is attached to a different end support. The actuating rod can move the end support of the apparatus, to which it is connected, towards the other end support so that the first part of the cage assembly attached to this end support is also moved towards the second part of the cage assembly. In this position, the apparatus is in the position for filtration, providing a packed fibrous arrangement. The cage assembly provides full support for the tubular filter. Preferably the second part of the cage assembly is fixed by attachment to the end support of the apparatus opposite to that connected to the actuating rod. In use, the end supports are placed in their operational position with the fibres supported on the cage so as to form the fibrous filter Liquid passes through the inlet through the fibres which act in the conventional way. When it is desired to backwash the filter element, the end supports are moved away from each other and the fibres untwisted. This movement of the end supports causes the gaps to increase between the cage or part of the cage and one or more end supports (depending on to which end support the cage or parts of the cage are attached), thus allowing greater flow of liquid Liquid is then passed through the filter element in the reverse direction (i.e. through the outlet and out through the inlet) to backwash the filter element and remove contaminants on the fibres. In use, the filter apparatus, according to the present invention, is operated in the general manner disclosed in EP 360601. A specific embodiment of the present invention will now be illustrated by reference to the accompanying drawings in which: - Fig. 1 cross-section through an apparatus, according to the invention shown in the packed configuration Fig. 2 is in the fully extended position and. Fig . 3 is an alternative embodiment of the invention in the extended position. The apparatus comprises a casing (1) divided into two compartments by a tubular fibrous filter indicated as (2). The fibrous filter comprises bundles of fibres secured at each end-to-end supports (3) and (4). End support (3) is fixed to the casing via (5). End support (4) is attached to an actuating rod (6) to enable it to be moved axially towards end support (3) and also rotated relative to end support (3). A liquid inlet (7) is provided in casing (1) opening into the compartment surrounding the tubular filter. A liquid outlet (8) is provided in the base of the casing opening into the compartment located within the tubular filter A cage structure comprising a number of circular rings ( 3) is located inside the tubular filter and comprises two parts, a fixed part (10) and a movable part (11). The fixed part (10) is attached to end support (3). The movable part is attached to the end support (4) and may be moved towards and away from the fixed part by means of the actuating rod (6). Alternatively the cage structures (10) and (11) are not fixed to the end supports (3) and (4) but are in the form of a "floating cage", as shown in fig. 3. In the position shown in Fig. 1, the movable part (11) has been moved so that the gap (12) between the two parts is substantially equal to the gaps between the circular rings (13) which make up each part of the cage structure. The filter apparatus is now in its packed position suitable for filtration. In the position shown in Fig. 2, the gap (12) has been increased by moving part (11) away from part (10) and the filter apparatus is in its fully extended position suitable for backwashing.

Claims: Claims 1 An apparatus which can be used for removing contaminants from a liquid and for coalescing droplets of a liquid dispersed in another immiscible liquid, which apparatus comprises a casing divided into two compartments by a substantially tubular fibrous filter, the said fibrous filter being formed by fibres attached at each end to an end support, there being a liquid inlet leading to one side of the fibrous filter and a liquid outlet leading from the other side of the fibrous filter, the said end supports being moveable axially relative to each other and rotatable relative to each other about the longitudinal axis of the tubular fibrous filter, there being a cage assembly comprising a plurality of rings located within the fibrous filter adapted to support the fibres forming the fibrous filter 2. Apparatus as claimed in claim 1 in which the cage assembly is in contact with the fibres forming the fibrous filter to support the fibres so as to resist the inward movement of the fibres caused when the end supports are moved axially towards each other and rotated to twist the fibres. 3 Apparatus as claimed in claim 1 or 2 in which one of the end supports is connected to an actuating rod which can move this end support axially towards and away from the other end support and rotate this end support about the longitudinal axis of the tubular fibrous filter 4 Apparatus as claimed in any one of claims 1 to 3 in which the cage assembly consists of a series of rings arranged along a common axis 5 Apparatus as claimed in claim 4 in which the rings are connected to an end support 6 Apparatus as claimed in claim 4 in which the rings are not connected to either end support 7 Apparatus as claimed in any one of claims 1 to 6 in which the cage comprises at least one set of rings comprising a plurality of rings connected to each other 8. Apparatus as claimed in claim 7 in which the cage comprises two sets of rings. 9. Apparatus as claimed in claim 8 in which each set of rings is connected to a different end support so that as the end supports are moved closer or further apart, the two parts of the cage are also moved closer or further apart. 10. Apparatus as claimed in claim 8 in which neither of the sets of rings are connected to an end support. 11. Apparatus as claimed in any one of claims 4 to 10 in which the gaps between the rings in each set are of a distance to give adequate support to the fibres without too great an effect on the flow of liquid through the filter element when the equipment is in operation. 12. Apparatus as claimed in any one of claims 4 to 10 in which the rings forming the cage structure are located in position by means of radially and/or longitudinally arranged supports. 13. Apparatus as claimed in claim 1 as hereinbefore described with reference to the drawings.

Inventors: COSGROVE RONALD CHARLES, GOUGH ANDREW, GREGORY GEOFFERY, PEARCE GRAEME KEITH, PHILLIPS EDWIN DAVID, COSGROVE, RONALD, CHARLES, GOUGH, ANDREW, GREGORY, GEOFFERY, PEARCE, GRAEME KEITH, PHILLIPS, EDWIN, DAVID
Applicants: COSGROVE RONALD CHARLES, GOUGH ANDREW, GREGORY GEOFFERY, KALSEP LTD, PEARCE GRAEME KEITH, PHILLIPS EDWIN DAVID, COSGROVE, RONALD, CHARLES, GOUGH, ANDREW, GREGORY, GEOFFERY, KALSEP LIMITED, PEARCE, GRAEME KEITH, PHILLIPS, EDWIN, DAVID
Application year: 1996
Main classification: B01D35
IPC codes: B01D17, B01D29, B01D35