GB2274405A - Apparatus for removing oil from water - Google Patents

Abstract

Apparatus for picking up oil from the surface of open water comprises a floating boom 8 stationed, in use, generally transverse to the direction of wind and/or waves and attached to an oil collecting trough 10 extending along the windward side of boom 8 so that the wind and/or waves spill oil into the trough, preferably up an integral floating ramp 12. The trough 10 may have oil-collecting sumps spaced at intervals, with mesh floors to release the water, steam heating coils and augers to pump out the oil. Or the oil may flow from the trough into removable, rearwardly extending collection bags, with mesh ends. Or the trough itself has a mesh floor. <IMAGE>

Description

APPARATUS FOR SEPARATING OIL FROM WATER This invention relates to apparatus for separating oil from water.

The effect on the environment of oil spillages in the sea, for example, is causing increasing concern. The usual response to a spillage is to protect the most sensitive areas with a floating boom, if that is possible, and to spray the slick with a detergent to encourage it to disperse. Dispersal at best spreads the pollution more thinly or moves it somewhere else. It does not remove the pollution. Indeed, as large quantities of dispersant are used this adds to the overall pollution.

In accordance with the invention, there is provided apparatus for separating oil from the surface of an open body of water, comprising: a floating boom stationed, in use, generally transverse to the direction of wind and/or waves across the surface of the water/oil to be separated, a trough generally parallel to the boom; said trough having a windward edge facing, in use, into the wind and/or waves and positioned at such a height relative to the surface of the water/oil that waves spill oil into the trough.

The apparatus is largely passive in its action.

Power may be utilised to extract the oil from the trough but is otherwise not needed. Neat oil, or a mouse or emulsion of oil an water slop unassisted and unattended into the trough, perhaps with some plain water. The boom prevents oil from slopping out of the trough on the down wind and/or down wave side of the apparatus. Operating costs may be kept low. The apparatus may be constructed inexpensively so that large installations may be used commensurate with the size of a slick. The apparatus may be used in place of a conventional boom additionally to protect an area such as a river estuary from pollution, or to contain a slick by surrounding it completely. Any or all oil installations could thus be isolated by a permanent apparatus in the form of a ring. Any spillages surrounded by such apparatus would be not just contained but almost completely recoverable.

In order to facilitate the oil spilling into the trough under the action of the waves, a ranp is preferably provided upwardly inclined from below the oil/water interface towards the leading edge of the trough. The trough may be inexpensively made from sheet material e.g.

tarpaulin. The ramp may be made from similar material which may be stretched or stiffened by relatively rigid elongate members extending transverse to the length of the boom.

The trough may have holes in its bottom to allow water to drain through.

Tanks may be provided for the oil to drain into from the troughs. The oil may then be pumped from the tanks.

further separation may take place in the tanks so that oil and water may be pumped out separately.

Alternatively, the oil may drain into bags which may then be removed for emptying. Remote froi the trough the bags may have an open end or and end closed by netting in order to encourage movement of oil or oil and water into the bag but retain the oil. Water may seep out the open or netted end. When the bag is full of oil both its ends are closed before it is removed.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross section through apparatus embodying the invention, installed so as to separate oil from the surface of an open body of water; Figure 2 is a plan view of the apparatus of Figure 1; Figure 3 shows tanks for collecting the oil in the apparatus of Figure 1; Figure 4 shows an alternative arrangement of bags for collecting the oil; Figure 5 shows a cross section through another arrangement similar to that of Figure 4; Figure 6 is a perspective view of another apparatus embodying the invention; and Figure 7 is a transverse cross section of the apparatus of Figure 6.

Referring to the drawings, An oil slick 2 floats on the surface of a body of water 4, e.g. the sea. Wind blows in the direction of arrow 6 producing waves on the surface of the oil/water which travel in the same general direction.

The waves and surface drift cause the oil slick also to travel in the same general direction as the wind.

The apparatus comprises a boom 8 which is formed in connected sections and stationed generally transverse to the direction of the wind, the waves and the surface drift. In front of (i.e. to windward of) and parallel to the boom 8 is positioned a trough 10. The windward edge of the trough is positioned a distance above the mean surface level of the oil/water, such that waves cause largely oil, or an oil water mouse or emulsion, to spill into the trough. Holes may be provided in the bottom of the trough to allow water to drain out but retain the oil. The boom is of sufficient height largely to prevent oil from spilling from the trough to leeward.

The action is considerably enhanced by the addition of a ramp in front of the trough. The ramp may be constructed from a frame of which fore and aft members 14 and 16 lie parallel to the boom and are constructed of a flotation material sufficient to support the windward edge of the trough 10. The frame is covered with a flexible sheet material in the form of tarpaulin. The ramp considerably assists the wave action to spill oil into the trough. The trough may be constructed of a material similar to that of the ramp.

In another arrangement (not illustrated) the trough is supported between two ramps The apparatus may be moored as shown in the drawings by anchors or may, in the alternative, be held on station by ships or boats. In Figure 1, a cable 18 is attached to a ground anchor, not shown. A mooring buoy 20 is attached to the upper end of the cable 18. As may be seen from Figure 2, a plurality of anchored buoys 20 are spaced along the apparatus. Mooring lines 22 attach each cable 18 to the ramp at positions spaced therealong.

At the ends or at intervals along the trough are positioned tanks 24 into which the trough drains. Oil or oil and water thus collect in the tank 24 from the trough.

The bottom of the trough is preferably net so that water can pass through but oil will be retained. Heavy crude oil is almost solid at sea water temperatures and so will be retained by quite coarse netting. Light crude oil may require finer mesh. The netting may allow the water into a slump from which it may be pumped, or may allow the water to drain straight back into the sea. The oil is pumped from the tank with and auger 28, for example. Heavy crude oil, especially, will require heating before it can be pumped and for this purpose coiled steam pipes 30 are provided in the tank 24. Steam heating lines (not shown) may also be run down the trough to improve oil flow therethrough.

In the arrangement shown in Figure 4, the bottom of the trough is extended by tubular outlets 32 under the boom to connect to oil collection bags 34. The outlets are laced up at 36 until a bag is fitted. The remote ends 36 of the bags are closed by netting so as to allow the movement of water therethrough but so as to retain the oil. Once a bag is full it may be removed and replaced with an empty one.

Before disconnection of the bag its ends are closed e.g. by lacing, as is the tube 32. The full, closed bag may be towed away and emptied.

The arrangement shown in Figure 5 is similar to that of Figure 4. In Figure 5, however, the boom 10 is in the form of a triangular section polystyrene baulk. The floats 14 and 16 are in the form of sealed tubes which may be flooded to a greater or lesser extent to adjust the height of the windward edge of the trough and to adjust the angle of attack of the ramp 12. The boom 10 is prevented from drifting off and flattening the trough 10 by rope ties spaced at intervals therealong.

The embodiments described above include rigid members, in the form of the fore and aft members 14 and 16 (Figure 1) or the baulk type boom 8 of Figure 5 which extend in the longitudinal direction of the boom. Since the apparatus may be required in lengths of several kilometres across the path of a slick or to surround a slick, these rigid members might provide an encumbrance to stowage during transport to the spillage. These embodiments would thus need to be stowed in many section.

A potentially more convenient arrangement is illustrated in Figure 6. Here weights 40 are suspended beneath the buoys 20 by lines 42. The leading edge of the tarpaulin ramp 12 is tethered to the lines 42 or the weights 40 a predetermined distance between the mean level of the water/oil surface. Elongate relatively rigid members 12 stretch and/or stiffen the ramp in the fore and aft direction transverse to the length of the boom.

Longitudinal stiffening is provided by the boom itself, which is inflated, by a longitudinally extending inflatable wedge 44 at the aft end of the ramp and, at the fore end of the ramp by the tension provided by mooring the apparatus to the buoys 20. The apparatus may be flaked into a container or hold for transport with the buoys or these may be detached for transport and attached as the apparatus is shot into the water.

The trough 10 is prevented from drawing out flat in this embodiment by bars 46. The bottom of the trough is formed partly of net 48 to allow water to escape but retain the oil. The bags 34 are also made from net to allow the water to escape but collect the oil.

Claims (13)

1. Apparatus for separating oil from the surface of an open body of water, comprising: a floating boom stationed, in use, generally transverse to the direction of wind and/or waves across the surface of the water/oil to be separated, a trough generally parallel to the boom; said trough having a windward edge facing, in use, into the wind and/or waves and positioned at such a height relative to the surface of the water/oil that waves spill oil into the trough.

2. Apparatus as claimed in claim 1, wherein a ramp is provided upwardly inclined from below the oil/water interface towards the leading edge of the trough.

3. Apparatus as claimed in claim 1 or claim 2, wherein the trough is made from sheet material.

4. Apparatus as claimed in any preceding claim, wherein the ramp is made from sheet material.

5. Apparatus as claimed in claim 4, wherein the sheet material of the ramp is stretched or stiffened by relatively rigid elongate members extending transverse to the length of the boom.

6. Apparatus as claimed in any of claims 3 to 5, wherein the sheet material is tarpaulin or canvass.

7. Apparatus as claimed in any preceding claim, wherein the through has holes in its bottom to allow water to drain through.

8. Apparatus as claimed in any preceding claim, wherein tanks are provided for the oil to drain into from the troughs.

9. Apparatus as claimed in claim 8, including means to pump the oil from the tanks.

10. Apparatus as claimed in any of claims 1 to 7, including bags arranged for the oil may drain into.

11. Apparatus as claimed in claim 10, wherein the bags are removable for emptying.

12. Apparatus as claimed in claim 10 or 11, wherein remote from the trough the bags have an open end or and end closed by netting in order to encourage movement of oil or oil and water into the bag but retain the oil.

13. Apparatus substantially as hereinbefore described with reference to the accompanying drawings