GB1604680A - Cleaning contaminated liquids for example oily water - Google Patents

Description

(54) CLEANING CONTAMINATED LIQUIDS FOR EXAMPLE OILY WATER (71) We, ALEXANDER ESPLEN & COMPANY LIMITED, a British Company of, Graphic House, 107 Duke Street, Liverpool, L1 4JR, 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: The invention relates to cleansing liquids, especially cleansing oily water of its oil content, though a wider application to the cleansing of liquidsm particularly the separation of immiscible liquids, is foreseen.

Particular problems arise in relation to oil pollution of the sea by discharges from ships, so much so that the maximum oil content of bilge discharge is now required, at least for new vessels, to be of the order of 15 parts per million or less. Such low oil content is beyond the capability of single stage oil/water separators in use generally for many years, and which usually produce water cleansing to an oil level of about 100 parts per million.

According to the invention, there is provided liquid cleansing apparatus comprising a first stage unit for taking off a relatively light contaminant liquid immiscible with the liquid to be cleansed, by flotation but on a substantially continuous flow basis, and a second stage unit for output of the first stage unit still containing small size droplets or globules of the contaminant liquid entrained therein, the second stage unit including a plurality of substantially vertical independently parallel-fed elements for slowing input liquid flow, most particularly the contaminant droplets or globules, each said element being an outward flow element and comprising a multiple layer filter or honeycomb-like structure offering outlet for liquid and contaminant only by tortuous passage through intercommunicating pores thereof to bring droplets or globules of contaminant into contact to coalesce and substantially saturate the capacity of the elements to hold contaminant whereupon internal pressure of input liquid flow causes appearance on exteriors of the elements of larger globules of contaminant having positive buoyancy.

In preferred embodiments of the invention that meet these new requirements a cleansing system has a first stage unit that takes off a light contaminant liquid (e.g. oil) by flotation in a generally conventional manner, as wherein input liquid flow (e.g. oily water) is pumped, usually downwardly, into a flow diffusing arrangement that slows and spreads the crosssection of flow in introducing direction changes sufficient to cause most of the lighter liquid to separate out and float upwards usually with no through-put reduction but an increased dwell time, and a second stage unit as aforesaid that receives 'cleansed' liquid (lightly contaminated water) still containing small size elements of the contaminant liquid (oil) entrained therein and serves via a plurality of said parallel elements to slow, even temporarily stop, and coalesce the contaminant liquid components to globule sizes of positive buoyancy to float off upwards from the exteriors of those elements.

Suitable coalescing elements comprise generally tubular elements closed at one end and open at the other to receive liquid to be cleaned, with passage sideways through those elements for that liquid via unaligned pores or interstices of fibrous material such as layers of rope, say cotton, or successive layers of woven or matted materials, say synthetic textiles, in a fairly rigid arrangement that reduces or eliminates any tendency to the formation of straight unobstructed through channels.

The use of a number of coalescing elements in parallel increases flow rates and reduces individual element 'work-loads' so as to produce a long element replacement interval, perhaps as low as twice per year for a ship in normal commercial use. Replacement requirement is believed to be more due to the presence of particulate material than to the removal of oil as such and it is envisaged herein that the second stage unit may be provided with a liquid entry chamber into which the liquid may pass only via a separator or filter, preferably of a form resembling that of the coalescing elements but perhaps of a coarser nature and readily replaceable.

It is to be noted that such elements quickly reach oil saturation which maximises internal pressure which, in contrast to conventional filtration represents optimum conditions for coalescence.

It has been found that relatively large globules form on and break away from the coalescing elements at their exterior, and it is further proposed that in order to reduce any entrainment effects from such globules by the cleansed water and/or to catch globules that have traversed the coalescing elements there be provided about the coalescing units a generally cylindrical fine mesh screen through which water must pass out of the unit.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows diagrammatic sectional side views through two stages of that embodiment; Figure 2 shows plan views of the stages of Figure 1;and Figures 3 and 4 show part cutaway side and plan views of a preferred coalescing element.

In Figures 1 and 2 a first stage 10 comprises an upright cylindrical chamber or vessel 12 with removable conical cap 14 and a conical base 16.

Within this cylindrical container is a substantially central so called compactum chamber 18 surrounded by an impervious cylindrical sleeve 20 depending from a through-flow permitting support 22 above the compactum chamber and extending to a level below an impervious base 24 of that compactum chamber. The impervious cylindrical sleeve 20 enters a cylindrical pan 26 supported with its base below the end of that sleeve so that water from the compactum chamber must first flow downwardly and upwardly and again downwardly past the pan to an exit position 30 formed at the centre of base 16 with communication to the downtumed end 32 of an exit pipe 34.

Bilge water feed to the first stage of the vessel is by way of an entry pipe 36 above the support 22 but bent downwardly therethrough into the compactum chamber 18 which, as shown, is of a multiple spiral vane type fed from its centre the vane slowing, spreading, and changing the direction of, input liquid flow to promote separation and upward floating of oil components.

Oil will tend to collect at the top of the vessel within its conical top and an oil removal dish and pipe arrangement 40 is shown in conjuction with an oil drain valve 42. This valve will normally be controlled by sensing the oil level at the top of the tank, typically by capacitive sensors 44 and 46, so as to keep it between two prescribed levels. A further and lower sensor 48 may be provided for stopping the system altogether should the build-up of oil become too great. Inlet and outlet valves 50 and 52 are also shown and may be interlocked in any desired way for control purposes, for example utilising a pressure gauge 54 so that the outlet valve may not open unless the vessel is full. A system relief valve 56 is also shown at a lower tapping 58 on the vessel, as is a drain valve 60 from the conical bottom and an input water test connection 62 from the entry pipe to a tap 64 external of the vessel and above a bilge return trough 66.

The second stage unit 70 is also a generally cylindrical vessel 72 with a conical bottom 74 and having a reduced diameter upper oil chamber 76 with conical top 78. Within the central part of the cylindrical vessel and inside a fine mesh polyproplylene coated metal screen 80 there is a regular arrangement of a plurality of coalescing elements 82 each of generally cylindrical form with a closed upper end 84 and an open lower end 86 extending through a support plate 88 for hollow formers 90. These capped former tubes 90 are apertured at appropriate positions 92 within their upper portions whereat they are surrounded by flow obstructing elements 94 in the form of multiple layers of synthetic textile material so that inlet water thereto from the lower part of the vessel will be stripped of a least the majority of small and thus non-floating oil globules which will be slowed and stopped in, then pushed through, the textile layers and gradually coalesce so that at least at and towards the outsides they form globules that will detach from the outsides and float upwards to the oil chamber.

Once the coalescing layers are substantially saturated with oil droplets in conjunction with carrying water, a maximum internal pressure will obtain for the coalescing elements, and optimum running conditions then provided will result in an overall equilibrum of the system for as long as it remains in use, and without requiring attention.

Water inlet from the first stage via a valve 96, to lower chamber 98 of the vessel is through an element 100 of a form substantially similar to that of the coalescing elements but usually of coarser structure to allow more ready and quicker flow without substantial coalescence of said globules or droplets but still ensure that at least a majority of solids in the form of particulate entrainment material will be caught in the element which is fitted for ready removal and replacement as required by withdrawal from one side 102 of the chamber through closable access means. Clearly, more complex structures could be used though withdrawal may be less easy.

Cleaned water exit is via a valved tapping 104 at a low level of the vessel, but above the solid coalescing element mounting plate 88, and adjacent a lower pan-like screen mount 106 flanged at 107 to cooperate with casing flanging in making a tortuous flow path.

An oil take off unit 108 generally similar to that of the first stage, including liquid level detection means as desired, is shown taken from the reduced diameter oil chamber and a vessel drain 110 from the conical bottom is also provided. A bilge return trough 112 is shown with pipe work 114 and 116 for oil and input water test purposes, the former being branched to a valve member 118 so that water at the upper part of the vessel but outside the fine mesh screen may be tested.

One particular coalescing element 94 is shown in the partially cut away longitudinal and fragmentary cross-sectional views of Figures 3 and 4. That tubular element has, from its outside, successive layers comprising a muslin outer sleeve 120, four layers 122 to 128 of Terylene (Registered Trade Mark) needle felt, typically of a total thickness of about inch, and bound by nylon cord 130, a sheath 132 of open weave glass fibre mesh about a layer 134 of glass fibre wadding 134, typically about 1 inch thick, plastics coated expanded steel flattened mesh 136, typically of 20 SWG sheet with 52% open area, a pleated layer 138 of felt crimped with wire mesh, typically of 26 SWG wire with 14 meshes per linear inch, all secured between layers 140, 142 of embedding resin within plastic coated metal end covers 144, 146 bearing neoprene gaskets 148, 150 for coupling to the central feed cavity.

WHAT WE CLAIM IS: 1. Liquid cleansing apparatus comprising a first stage unit for taking off a relatively light contaminant liquid immiscible with the liquid to be cleansed, by flotation but on a substantially continuous flow basis, and a second stage unit for output of the first stage unit still containing small size droplets or globules of the contaminant liquid entrained therein, the second stage unit including a plurality of substantially vertical independently parallelfed elements for slowing input liquid flow, most particularly the contaminant droplets or globules, each said element being an outward flow element and comprising a multiple layer filter or honeycomb-like structure offering outlet for liquid and contaminant only by tortuous passage through intercommunicating pores thereof to bring droplets or globules of contaminant into contact to coalesce and substantially saturate the capacity of the elements to hold contaminant whereupon internal pressure of input liquid flow causes appearance on exteriors of the elements of larger globules of contaminant having positive buoyancy.

2. Apparatus according to claim 1, wherein each said element serves temporarily substantially to stop at least some incoming contaminant globules or droplets for coalescence thereof.

3. Apparatus according to claim 1 or claim 2, wherein each said element comprises laminated layers at least some successive ones of said layers being of different materials.

4. Apparatus according to any preceding claim, wherein each said element is generally tubular, closed at one end and open at the other to receive output of the first stage unit.

5. Apparatus according to claim 4, wherein each said element is substantially as herein described and shown in Figures 3 and 4 of the accompanying drawings.

6. Apparatus according to any preceding claim, comprising for passing liquid output of the first stage unit to said elements, filter means to remove entrained particulate material.

7. Apparatus according to claim 6, wherein the filter means has a construction resembling that of said elements but of a coarser nature inadequate to produce substantial coalescence of said globules or droplets.

8. Apparatus according to claim 6 or claim 7, wherein the filter means is within an entry chamber of the second stage unit.

9. Apparatus according to claim 8, wherein said entry chamber is below said elements.

10. Apparatus according to claim 8 or 9, wherein said filter means is removable from the entry chamber via closable access means of a casing of the second stage unit.

11. Apparatus according to any preceding claim, wherein said elements are surrounded by a cylindrical fine mesh screen through which cleansed liquid must pass from the elements to an outlet therefor.

12. Apparatus according to any preceding claim, wherein each of the first and second stage units has an upper contaminant collection region or chamber.

13. Apparatus according to claim 12, further comprising liquid level detection means for sensing that contaminant take-off from said collection regions or chambers is required.

14. Apparatus according to claim 13, comprising automatically controlled valve means operative according to the level detection means.

15. Apparatus according to any preceding claim, wherein the first stage unit comprises a flow diffusing arrangement that serves to slow and spread the cross section of liquid flow by means causing direction changes of flow.

16. Apparatus according to any preceding claim, wherein overall flow of the liquid to be cleansed through the first stage unit is from an upper to a lower level.

17. Apparatus according to any preceding claim. wherein overall flow through the second stage unit is constrained to be from a lower level to the elements.

18. Apparatus according to any preceding claim, when used to cleanse water of oil.

19. Cleansing apparatus arranged and adapted to operate substantially as herein described with reference to and as shown in Figures 1 and 2 or Figures 1,2 and 3 of the accompanying drawings.

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

Claims (19)

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

   water test purposes, the former being branched to a valve member 118 so that water at the upper part of the vessel but outside the fine mesh screen may be tested.

   One particular coalescing element 94 is shown in the partially cut away longitudinal and fragmentary cross-sectional views of Figures 3 and 4. That tubular element has, from its outside, successive layers comprising a muslin outer sleeve 120, four layers 122 to 128 of Terylene (Registered Trade Mark) needle felt, typically of a total thickness of about inch, and bound by nylon cord 130, a sheath 132 of open weave glass fibre mesh about a layer 134 of glass fibre wadding 134, typically about 1 inch thick, plastics coated expanded steel flattened mesh 136, typically of 20 SWG sheet with 52% open area, a pleated layer 138 of felt crimped with wire mesh, typically of 26 SWG wire with 14 meshes per linear inch, all secured between layers 140, 142 of embedding resin within plastic coated metal end covers 144, 146 bearing neoprene gaskets 148,

   150 for coupling to the central feed cavity.

   WHAT WE CLAIM IS: 1. Liquid cleansing apparatus comprising a first stage unit for taking off a relatively light contaminant liquid immiscible with the liquid to be cleansed, by flotation but on a substantially continuous flow basis, and a second stage unit for output of the first stage unit still containing small size droplets or globules of the contaminant liquid entrained therein, the second stage unit including a plurality of substantially vertical independently parallelfed elements for slowing input liquid flow, most particularly the contaminant droplets or globules, each said element being an outward flow element and comprising a multiple layer filter or honeycomb-like structure offering outlet for liquid and contaminant only by tortuous passage through intercommunicating pores thereof to bring droplets or globules of contaminant into contact to coalesce and substantially saturate the capacity of the elements to hold contaminant whereupon internal pressure of input liquid flow causes appearance on exteriors of the elements of larger globules of contaminant having positive buoyancy.
2. 2. Apparatus according to claim 1, wherein each said element serves temporarily substantially to stop at least some incoming contaminant globules or droplets for coalescence thereof.
3. 3. Apparatus according to claim 1 or claim 2, wherein each said element comprises laminated layers at least some successive ones of said layers being of different materials.
4. 4. Apparatus according to any preceding claim, wherein each said element is generally tubular, closed at one end and open at the other to receive output of the first stage unit.
5. 5. Apparatus according to claim 4, wherein each said element is substantially as herein described and shown in Figures 3 and 4 of the accompanying drawings.
6. 6. Apparatus according to any preceding claim, comprising for passing liquid output of the first stage unit to said elements, filter means to remove entrained particulate material.
7. 7. Apparatus according to claim 6, wherein the filter means has a construction resembling that of said elements but of a coarser nature inadequate to produce substantial coalescence of said globules or droplets.
8. 8. Apparatus according to claim 6 or claim 7, wherein the filter means is within an entry chamber of the second stage unit.
9. 9. Apparatus according to claim 8, wherein said entry chamber is below said elements.
10. 10. Apparatus according to claim 8 or 9, wherein said filter means is removable from the entry chamber via closable access means of a casing of the second stage unit.
11. 11. Apparatus according to any preceding claim, wherein said elements are surrounded by a cylindrical fine mesh screen through which cleansed liquid must pass from the elements to an outlet therefor.
12. 12. Apparatus according to any preceding claim, wherein each of the first and second stage units has an upper contaminant collection region or chamber.
13. 13. Apparatus according to claim 12, further comprising liquid level detection means for sensing that contaminant take-off from said collection regions or chambers is required.
14. 14. Apparatus according to claim 13, comprising automatically controlled valve means operative according to the level detection means.
15. 15. Apparatus according to any preceding claim, wherein the first stage unit comprises a flow diffusing arrangement that serves to slow and spread the cross section of liquid flow by means causing direction changes of flow.
16. 16. Apparatus according to any preceding claim, wherein overall flow of the liquid to be cleansed through the first stage unit is from an upper to a lower level.
17. 17. Apparatus according to any preceding claim. wherein overall flow through the second stage unit is constrained to be from a lower level to the elements.
18. 18. Apparatus according to any preceding claim, when used to cleanse water of oil.
19. 19. Cleansing apparatus arranged and adapted to operate substantially as herein described with reference to and as shown in Figures 1 and 2 or Figures 1,2 and 3 of the accompanying drawings.