GB2280197A

GB2280197A - Oil recovery

Info

Publication number: GB2280197A
Application number: GB9314485A
Authority: GB
Inventors: Roy Anthony Richard Puncher
Original assignee: PUNCHER WYLIE OILSPILL RECOVER
Current assignee: PUNCHER WYLIE OILSPILL RECOVER
Priority date: 1993-07-12
Filing date: 1993-07-12
Publication date: 1995-01-25
Also published as: AU7130394A; WO1995002733A1; GB9314485D0

Abstract

In an apparatus for recovering oil, a collected oil and water mixture is delivered to a collection tank through a fluid deflector which imparts an upward movement to the mixture, which facilitates separation of the oil. As shown, the mixture is delivered via tube 18 to an annular distributor 206 at the bottom of the tank, having holes 207 in its upper surface. <IMAGE>

Description

IMPROVEMENTS RELATING TO OIL RECOVERY The present invention relates to oil recovery method and apparatus and in particular but not exclusively to apparatus of the kind described in Canadian Patent 1 138 352, the teachings of which are incorporated herein by reference.

Hereinafter described is an improvement of the method and apparatus described in the above mentioned Canadian patent. The arrangement and operation of the apparatus of the present invention is in many respects similar to that described in the Canadian patent and the description hereinafter will concentrate on the differences provided by the present invention.

In the Canadian patent an oil recovery method and apparatus is described which separates oil from an oil/water mixture by relying on the lower specific gravity of oil to achieve the separation. The apparatus comprises a collection unit which has a generally U-shaped vertical retaining wall which funnels the oil/water mixture to a collection area.

Directly below the collection area, there is located a submerged conduit which forms a pumping unit that connects to a trailing recovery unit. The conduit contains an impeller, which draws the oil/water mixture from the collection area through the conduit to a partially submerged holding tank of the recovery unit. The holding tank is a vertically orientated open-ended cylinder and in its lower section there is provided an opening for the input of the oil/water mixture from the conduit. As the mixture is input into the holding tank, the oil separates from the water and rises to accumulate on the surface of the water within the holding tank cylinder. As more and more oil accumulates, water is pushed out of the bottom of the holding tank until the tank is full with recovered oil.

The holding tank is attached to the recovery unit by means of a pair of stub shafts which permit controlled pivoting of the holding tank for storage of the tank during transportation, but in use the holding tank is held rigidly to the recovery unit. In calm weather, the oil recovery apparatus functions as desired but in turbulent weather, movement of the recovery unit and hence of the holding tank may cause spillage of recovered oil and/or slopping of the oil and water which may lead to some emulsification.

Thus, efficient operation of the apparatus is undesirably dependent upon weather conditions.

Clearly this is a limitation of the apparatus described in the Canadian patent.

Furthermore, the relationship between the conduit and the holding tank as described in the Canadian patent is such that as the oil/water mixture is input into the holding tank it is deflected in a circular flow pattern following the inner wall of the holding tank. Oil tends to separate from the oil/water mixture by rising and accumulating on the surface of the water but a sidnificant amount of the oil/water, mixture remains emulsified and hence not all of the oil and water is separated.

The present invention aims to overcome at least some of these problems.

According to one aspect of the present invention there is provided an apparatus for recovering oil in which apparatus a collected oil and water mixture is delivered via a conduit to a collection tank and is input to the collection tank through a fluid deflector which imparts an upward movement to the oil and water mixture and thereby facilitates separation of the oil from the oil and water mixture in the collection tank.

According to another aspect of the present invention there is provided a method of recovering oil, the method comprising: collecting an oil and water mixture; delivering the collected mixture via a conduit to a collection tank; and deflecting the oil and water mixture so as to impart an upward movement thereto and thereby facilitate separation of the oil from the oil and water mixture in the collection tank.

The above and further features of the present invention are set forth with particularity in the appended claims and together with advantages thereof should become clearer to those persons skilled in the art by consideration of the following detailed description of an exemplary embodiment of the invention given with reference to the accompanying drawings.

In the drawings: Figure 1 is an overhead schematic view of an improved holding tank embodying the invention; and Figure 2 is a cross-sectional view of the holding tank in Figure 1 taken through the line A-A'.

Figure 1 of Canadian Patent 1-138 352 shows an oil recovery apparatus 10 which comprises a collection unit 12, a pumping unit 16 and a recovery unit 14.

The collection unit 12 is connected via the pumping unit 16 to the recovery unit 14. The present invention relates to improvements in the recovery unit 14 and in other respects comprises many components similar or equivalent to those shown in the Canadian patent. Reference is made to the description contained in the Canadian patent and no further description will be given herein regarding the components of the present embodiment that have similar or equivalent components in the apparatus described in the Canadian patent.

In Figure 1 of the accompanying drawings there is shown an improved holding tank 70 embodying the present invention. The holding tank 70 is connected to the body of a recovery unit (not shown in the accompanying drawings) by a conventional gimbal arrangement comprising four mounts 200, 201, 202, 203 which permit relatively free rotation of the holding tank 70 about two perpendicular axes. The mounts 200, 201 form a first pair of opposing mounts and are connected directly to the holding tank 70 and a movable circular ring frame 204. This arrangement provides one of the axes of rotation (represented by the line 208) of the holding tank 70; The mounts 202, 203 form a second pair of opposing mounts and are connected between the movable circular ring frame 204 and a stationary ring frame 205. The second pair of opposing mounts 202, 203 provide the second perpendicular axis of rotation (represented by the line 209). The stationary ring frame 205 is fixed to the body of the recovery unit (not shown).

The gimbal arrangement enables the holding tank 70 to remain in a substantially vertical position independent of the movement of the recovery unit.

This provides good stability to the holding tank in rough seas and prevents slopping and spillage of oil.

The holding tank 70 typically has a diameter of forty feet and contains a perforated endless inner tube 206. The tube 206 is located at the bottom part of the holding tank 70 as shown in Figure 2 of the accompanying drawings. The tube 206 is connected directly to a conduit 152 (equivalent to the conduit 152 shown in the Canadian patent) such that the oil/water mixture delivered from the conduit 152 passes through the tube 206 before it enters the holding tank 70. The tube 206 has multiple outlet apertures 207 of relatively small diameter which provide multiple paths for the oil/water mixture from the conduit 152 to the holding tank 70. The outlet apertures 207 are evenly distributed about the upper surface of the tube 206 so that the oil/water mixture is directed upwardly into the holding tank. This ensures that the oil/water mixture entering the tank is subjected to only minimal turbulence, and this minimises emulsification. Directing the oil/water mixture in an upward direction imparts an upward velocity to the oil and since the oil is lighter than the water this upward velocity makes it easier for the oil to get to the surface of the water. This enhances the separation between the oil and the water and thus improves the yield of recovered oil.

In the design of the tube 206, parameters such as the diameter of the tube 206, the number of outlet apertures 207 and the surface area of each outlet aperture 207 are chosen so that, ideally, a constant and even flow of the oil/water mixture from the collection unit 12 into the holding tank 70 is achieved. Desirably, the flow rate through the conduit 152 and tube 206 should be as high as possible without causing emulsification. In order to achieve this the diameter of the tube 206 is made equivalent to that of the conduit 152, and the number and size of the outlet apertures 207 is selected such that the total area of all the outlet apertures 207 is made equivalent to- the cross-sectional area of the conduit 152.

It should be noted that the total area of all the outlet apertures 207 ought not to be smaller than the cross-sectional area of the conduit 152 as this would increase the average speed at which the oil/water mixture enters the holding tank 70 and will result in increased emulsification of the mixture.

In this embodiment, the diameter of the conduit 152 and tube 207 is 48 inches, and there are thirtytwo apertures 207 each with a radius of approximately 4.24 inches.

It should be noted that it is also possible to make the size of the apertures 207 larger than stated above without increasing the average speed at which the oil/water mixture enters the holding tank.

However, the distribution of oil/water mixture flow around the entire upper surface of the inner tube 206 would not be uniform and hence this may cause some uneven flow or swirling around the holding tank which could in turn lead to a less than optimal recovery rate as more of the mixture is emulsified.

The improved stability of the holding tank 70 and the controlled flow of the oil/water mixture in the holding tank 70 both increase the percentage of oil that is recoverable. Furthermore, the inner tube 206 at the bottom of the holding tank 70 acts as a barrier against water from outside the tank and thus reduces slopping which may otherwise occur when the holding tank 70 is almost full of separated oil.

Having thus described the invention by reference to a particular embodiment, it is to be appreciated that the described embodiment is exemplary only and is susceptible to modification and variation without departure from the spirit and scope of the invention as set forth in the appended claims. In particular, the above described perforated inner tube 206 could be replaced by other types of fluid distribution systems which impart an upward velocity component to the oil/ water mixture.

Claims

CLAIM8:

1. An apparatus for recovering oil in which apparatus a collected oil and water mixture is delivered via a conduit to a collection tank and is input to the collection tank through a fluid deflector which imparts an upward movement to the oil and water mixture and thereby facilitates separation of the oil from the oil and water mixture in the collection tank.

2. An apparatus as claimed in claim 1, wherein the fluid deflector is located at a bottom portion of the collection tank.

3. An apparatus as claimed in claim 1 or 2, wherein the fluid deflector comprises an endless tube having a multiplicity of substantially upwardly facing apertures defined therein.

4. An apparatus as claimed in claim 3, wherein the total area of all of the multiplicity of apertures is equal to the cross-sectional area of the conduit.

5. An apparatus as claimed in claim 3 or 4, wherein the endless tube has a cross-sectional area equal to that of the conduit.

6. An apparatus as claimed in any of claims 3 to 5, wherein said apertures are evenly spaced.

7. An apparatus as claimed in any preceding claim, wherein said collection tank is provided with a gimbal mounting arrangement.

8. An apparatus as claimed in claim 7 wherein said gimbal arrangement comprises a first pair of mounts connected to said collection tank and a movable rim, a second pair of mounts connected between said moveble rim and a fixed rim, wherein said first and second pairs of mounts together define a -pair of movement axes which are perpendicular to each other.

9. An apparatus as claimed in any preceding claim wherein said collection tank comprises a cylinder open at both ends.

10. A method of recovering oil, the method comprising: collecting an oil and water mixture; delivering the collected mixture via a conduit to a collection tank; and deflecting the oil and water mixture so as to impart an upward movement thereto and thereby facilitate separation of the oil from the oil and water mixture in the collection tank.

11. A method as claimed in claim 10, wherein said deflecting occurs at a bottom portion of the collection tank.

12. A method as claimed in claim 10 or 11, wherein said deflecting comprises passing the oil and water mixture through an endless tube and through a multiplicity of substantially upwardly facing apertures defined therein.

13. A method as claimed in claim 12, further comprising arranging the total area of the multiplicity of apertures to be equal to the crosssectional area of the conduit.

14. A method as claimed in claim 12 or 13, further comprising arranging the cross-sectional area of the tube to be equal to that of the conduit.

15. A method as claimed in any of claims 12 to 14, further comprising arranging said apertures to be evenly spaced.

16. A method as claimed in any preceding claim, further comprising mounting said collection tank with a gimbal mounting arrangement.

17. An apparatus or holding means substantially as described herein with reference to the accompanying drawings.

18. A method substantially as described herein.