NO831644L - PROCEDURE AND APPARATUS FOR AA FAA MIRRORS OF OIL POLLUTION ON WATER - Google Patents

Description

This invention relates to a method and a device for controlling oil pollution on open water or along the coast.

The invention is particularly, but not exclusively, applicable to collect the oil and to remove the spilled material from the surface of the sea, on offshore oil fields such as in the North Sea, the Gulf of Mexico, off Alaska and others

.places.

There have:7 been many previous proposals for treating oil pollution. These can be classified as

a) the use of cleaning agents and dispersants,

b) attempt to sink the oil, and

c) attempt to collect the oil on the surface and then

to remove it from this.

The use of cleaning agents and dispersants is expensive when large oil spills are involved, as large quantities of possibly expensive chemicals must be transported and placed precisely on the spill. This procedure also poses a danger to wildlife. The attempts to

sinking the oil has so far not proved to be satisfactory, and entails the disadvantage that they are dangerous for fish and other life in the sea that grows or is located on the seabed. Many previous proposals under point c have been put forward, but most have not satisfactorily solved the many practical problems.

In accordance with the invention, a method has been arrived at to substantially remove oil that has been released into salt water or fresh water, which method comprises the oil being encircled by a fine-mesh net of considerable length, which net is connected to floats and holders on such a way that the net is kept mainly vertically, and causes or enables the oil to be moved to an area near a selected part of the net, and that the oil in this area is collected from the surface of the water and fed into a suitable container.

In the event that the oil has been released into open water, the oil is contained by surrounding it with an elongated, fine-mesh net, one end of which is attached to a suitable vessel,

and by gradually retracting the net, the oil is brought close to the vessel, so that it can be transferred by one or more pumps carried on the vessel into a suitable container, such as a tank in the vessel or a nearby tanker.

In the event that the oil has been released close to the coast, and particularly close to a beach, the elongated net is placed a short distance outside the coastline, in such a way that the effect of wind or tide (or both if they act simultaneously) is to bring the oil to an area near a selected part of the network, and the oil in this area is then transferred to a suitable container, e.g. using pumping or a mechanical scoop.

According to an embodiment of the invention, a method for collecting oil that has been released into open water has been arrived at, which includes the oil being encircled by a fine-mesh net of considerable length which is connected to floats and holders in such a way that the net is held approximately vertically and acts to encircle the oil.

In a preferred method according to this embodiment of the invention, one end of the net is brought out from a ship carrying it. The ship follows such a course while the net is being cast that a loop of net is formed, with an open mouth (in other words a U-shaped net seen from above), the open mouth (or top of the U) being nearest; the source to the oil spill, while the loop protrudes either in the direction of the wind or the direction of the tide. In the event that the wind direction and tidal current are not the same, the net is placed according to how far the oil is driven by the tide or by the wind.

A net of considerable length is preferably used, e.g. 1.6 or 3.2 km, and this preferably has such a mesh size that the holes have a largest dimension of approximately 2.5 mm. Any mesh size which does not allow the oil to pass through may be used and this is the meaning to be given to the words "fine mesh" used here. Optionally, the net may have a number of floats attached to the net approximately mid-height, and these floats may be essentially cylindrical or elongated float blocks connected end to end by a rope or cable. The rope or cable can protrude through the floats.

At suitable intervals along the net, this is supported by a buoy, namely a buoy which has a protruding post or stake. The net is attached at intervals to these posts, and is held by them in a mainly vertical orientation, to serve to largely or completely prevent the oil encircled from escaping. The bows have downwardly projecting poles with weights on the lower ends,

and these ensure that the posts or stakes normally point upwards. The buoys preferably have a mutual distance of approximately 0.8 - 2.0 m, and the spaces are preferably 1 m. The posts on the buoys can protrude through the floating body of these.

The net preferably has a total height of approximately 1.5 - 4 m, of which approximately 1 - 2 m or a fathom is below the water level and approximately 1 - 2 m is above the water level.

In contrast to the type of net used in seine fishing, there is no need to have any significant height of the net below the water level, nor is there any need to have a rope or a cable as a pull cord at the lower edge of the net, which is an essential feature of seine fishing.

According to the invention, a fine-mesh net has also been arrived at for use in controlling oil spills,

and the net has a length of over 200 times its width,

and a number of floats are attached to the net, at least some of which are buoys, the arrangement being such that the net can be kept substantially vertical when deployed in open water. The net can have a width (that is, a vertical height when deployed) of from 2-5

and preferably from 1.5 - 4 m.

The invention will be better understood from the following, non-limiting description of examples, with reference to the attached drawings, where: Fig. 1 is a schematic horizontal projection illustrating an early step in the method according to the invention, fig. 2 is a horizontal projection illustrating a later step in the method according to the invention,

fig. 3 shows a section of an example of a net, set

from the front, which can be used in the method according to the invention,

fig. 4 and 5 are cross-sections along the lines IV =r- IV: bg

V - V in fig. 3,

fig. 6 shows, in side view, a buoy for holding a net, which may be used in place of the floats and buoys shown in fig. 3 - 5,

fig. 7 schematically shows a procedure for retracting a net,

fig. 8 and 9 show, seen respectively towards one end and from the side, a drum for retracting a net,

fig. 10 is an illustration showing the use of a method according to the invention for collecting oil in a coastal inlet, and fig. 11 illustrates the deployment of nets according to the invention by means of boats to protect a coastline.

Fig. 1 shows schematically, seen from above, an area of sea or open water, in which there is a device that produces oil, and from which there is an unwanted discharge of oil, which lies on the sea as a sheet 12 and is blown towards the leeward side of the device 10, the wind direction being indicated by the arrow 14. A ship or other vessel 16 is equipped for setting out and retracting a net 18. To encircle the sheet 12, the ship first releases an anchor buoy 20 which is fixed with its anchor in the seabed. The ship then follows a curved path around the lee side of the sheet 12 and at the same time deploys the net 18. The course followed by the ship is approximately U-shaped and is essentially the same as the position taken by the net 18. It is thus formed a loop with an open mouth 22 which is positioned in such a way that all the oil that is released blows into the loop. During collection and call-in.

of the oil, the ship 16 can be anchored in the position shown in fig. 1, or it can be held proportionately

stable in this position using its engines.

The length of the net 18 used can e.g. be

3.2 km, and the distance between the ship 16 and the anchor buoy 20 can be between 0.8 and 1.6 km.

In the description, above, it has been assumed that the wind has the greatest influence on the movement of the oil slick, but if the tide had the greatest influence,

a similar procedure to that shown would have been used, except that the arrow would indicate the direction of tidal flow.

The oil that escapes from an oil rig 10 is thus encircled by the net 18, and after the oil has been stopped, the net loop is closed. The ship 16 is maneuvered to pick up the end 24

of the net, while the end 26 is still attached to the ship. The anchor buoy 20 is also taken in. The ship 16 and net 18 surrounding the oil can then be allowed to drift with the wind or tide, while oil is agglomerated (if desired)

to a thick slurry or gel by progressive addition of a suitable agglomerating agent. Such means are known. When the oil is agglomerated, the formed slurry or gel is transferred to the ship 16, and then, if the amount of slurry or gel exceeds the capacity of the ship 16, to a tanker or a series of tankers which are brought up to the ship 16.

As the situation is shown in fig. 2 wild tankers

be brought up to the port side of the ship 16. The agglomerated oil can be brought out of the ship 16 using scoops or lines, or in the case that agglomeration is not necessary, a mixture of oil and water is pumped on board and taken to separators for the oil and water , as the separated water is led out of the ship.

A suitable design of a net 18 is shown in fig. 3-5,

and the water level is shown at WL. Net 18 has long

rectangular shape, and has a length of e.g. 3.2 km and a width of about 3 m. It is attached at intervals to fender-shaped floats 30. These have a miter longitudinal hole 32, through which a rope or cable 33 is passed. Buoys 34, each of which has an upstanding rod 36 and a downwardly projecting bar 38 holding a plumb line 40 is also attached to the net at intervals, and the top 42 and bottom 44 of the net are suitably attached to the respective bars 36, 38, e.g. by means of cords 46. The height of the net is not critical, but it is believed that the best results will be obtained if the height h^ in .fig-. 3 is from 1 - 2 m and the height h2 is from 2 - 4 m. However, the invention is not limited to any specific dimensions.

It will be seen that with this arrangement the net 18 is held approximately vertically so that it acts as a blocking "fence" around the oil flake. In bad weather, of course, some oil will be thrown outside the net 18 due to rough seas, but in bad weather, as far as the applicants know and believe, none of the previously known methods for treating significant oil spills are satisfactory, and it is assumed that the described method is able to work satisfactorily in worse weather than the previously known methods. The procedures described here make use of techniques that have essentially been shown to be usable, based on experience from seine fishing, and it is assumed that the described procedure will prove advantageous and economical when calling in and collecting oil spills that include hundreds or thousands of tons of oil.

According to a preferred embodiment of the invention, the floats 30 can be made of or coated with an oil-absorbing material. The•middle floats 34

(fig. 4) or buoys can also be made of or be coated in, with such a material.

An alternative design of a buoy used to provide buoyancy for the net is shown in fig. 6. This is a simple buoy which has a protruding rod or rod 41, e.g. with a length from 1 - 4 m, and with a float 43 attached between the side ends. The lower end 45 is designed as or carries a plumb line, so that the buoy will float in a vertical position in the water. A pair of rings 47 can optionally be attached to the clamp 41 to simplify the attachment of the buoy to the net. The float 43 may be approximately at 2/3 of the height of the rod 41 but its exact height will be chosen according to the dimensions and material of the net for which the buoys are to be used. The buoys can be attached to the net in advance, during the manufacture of the net, or they can be attached one by one as the net is put into the water from the vessel that brings the net with it. In the latter case, the rings 47 on the buoy can be attached to the net by means of clips of the type that have a snap lock.

Fig. 7 shows a net 50 which is set out so that it surrounds an oil slick 52. A vessel 54 is in the process of drawing in the net and pumping oil into tanks in the hull. When it comes to a bulk oil volume, this will naturally be pumped into a number of tankers. The vessel 54 has a winch 56 for retracting, through a guide 57, a rope or a pair of ropes attached to one end of the net 50, to bring one end of the net close to the vessel's hull, to which it is then attached by means of suitable ropes or cables. The vessel also carries a drum device ^56 for retracting the net. This is a motor-driven drum on which the net 50 is wound, for retracting the net 50 and reducing the circumference of the oil slick. It is shown in more detail in fig. 8 and 9.

With reference to fig. 8 and 9, the drum device 56 has a drum 60 for a net, with an axial length of approximately 2 m, i.e. slightly more than the height of the net. The net drum 60 cooperates with a pair of pressure rollers 62, one at each end of the drum 60. Together with the drum 60, each of the rollers 62 defines a gap. In use, a front cable and a rear cable extend along the top and bottom of the net, and are attached to or threaded through the rings 47 on each buoy. When the net is pulled up from the water by means of the drum device 56, the front and rear cable and the nearest parts of the net are clamped in the respective slots between the rollers. The rollers 62 are of short axial length, so that they do not interfere with the winding of the web on the drum, since the web becomes thicker in its central part due to the presence of the floats 43. The drum 60 is held to rotate on

a shaft 6 3 projecting between end supports. 64, and is in the form of a hollow cylinder. At each end it contains motors and gears 66, so that the drum can be rotated in both directions relative to the holders 64. The motors 66 can be electric, pneumatic or hydraulic, or they can be driven mechanically by the main engine of the vehicle 54.

As mentioned, a pair of pressure rollers 62 form slots 68 together with the drum 60. Each pressure roller 62 is supported on a pivot arm 70, pivoted for movement about a horizontal axis 72. A piston-cylinder device 74 is mounted between a fixed bracket 76 and the free end 78 to each arm 70. The task of the device 74 is to provide pressure in the slot 68, so that it grips the net and the rear or front cable, as the case may be, so that the net can be drawn in, even against the very significant resistance that occurs due to the inertia of the oil slick 52. Fig. 10 shows the use of several elongated, fine-mesh nets 80-88 along the coast, to prevent oil from damaging beaches or rocks along the coastline. These nets 80-88 can be of the type shown in Figures 2 - 5, but a simpler net of the type described with reference to Figure 6 may also be used, as shown.A boat 90 is shown deploying the net 80 in a position where it is located between an oil slick 92 and the coastline one, and the ends of the nets 82 and 84 are anchored at 96, and these nets are deployed by boats 98 and 100. These nets are deployed to prevent oil from reaching an outer rock 102. Other nets 86,88 that are deployed of vessels 104,106 serves to block the oil slick from moving away from the coastline should the wind or tide change direction. A motorized suction pump 108 having a motor 110 and a suction nozzle 112 at the end of a boom 114 is located on a suitable wharf or jetty, in a position where it can collect oil from inside the net and transfer it to a transport line 116. Instead for the pump 108, a mechanical scoop can be used to collect the oil. Fig. 11 shows the deployment of an elongated, fine mesh net 120 from a boat 122 close to shore. Other nets are shown during deployment from other vessels, and the intended course of the boat 122 is shown by arrow 124. The individual nets will be joined after the deployment, and serve to protect the shoreline 125. Depending on the direction of wind and tide, the oil in the flake may 126 is collected in a suitable area near the lee side or in the part of the net which is located in the direction of flow, by means of a small tanker (not shown) which carries one or more suction pumps. As shown in fig. 11, one end of the net 120 is anchored by means of an anchor 128 and attached to a buoy 130.

According to an important but optional feature of the invention, an elongated, fine-mesh net as described above can be placed at the desired location from an aircraft, such as a slow-moving cargo plane or a helicopter, to encircle spilled oil. The net (with attached buoys) can be carried in the hold of the aircraft or helicopter, and released from this while the aircraft is flying, out through an open door or hatch in the aircraft. Alternatively, a roll of netting, already attached to buoys, can be held on a rotatable shaft which is carried on suitable bearings in the aircraft. Alternatively, a trough (or other equipment containing a net) may be suspended, e.g. in cables, under the aircraft, and an elongated net to which buoys are already attached, can be laid in folds in the trough, in one_.sling arrangement with a free end of the net attached to an anchor. The anchor is carried on the trough in a place where it can easily be knocked over or pulled from the trough, e.g. by a rope operated by the crew of the helicopter. The net is arranged in such a way that it will fall out freely after the anchor has fallen out of the trough, and this is done when the helicopter is in the desired position in relation to the oil slick. The rig attaches one end of the elongated net, and the helicopter is then flown around the oil slick, causing the net to be progressively pulled out of the trough and placed in the water around the oil slick. When the entire net is placed, another helicopter can take over, to place another net in a similar way, if the flake has...a size that makes this necessary. Otherwise, the end of the net is released, and also becomes anchored. Another anchor, at the other end of the net, can be set out in a similar manner if desired. The oil slick that is thus encircled can then be processed..That is to say, the oil can be agglomerated if necessary and collected mechanically, or it can be pumped into a tanker.

It will be understood that a usable and relatively inexpensive method and device for treating oil flakes of a significant size is described here. Compared to an earlier method proposed by NYFELDT (British patent application no. 2,044,623 A published 22 October 1980), problems with operating the pull rope 26, loosening and towing of oil-filled sections are avoided, and the method is better suited for treating large volumes of oil. In practice, towing a large volume of oil will entail large expenses for fuel for the towing vessels, and by using the applicant's method, no expenses for special, snake-shaped net sections arise. Compared to the proposal of REID (British patent application no. 2074,887 A published 11 November 1981) problems are avoided when steering a ship in bad weather, hindered by a wire net and a bag, as it is necessary occasionally to release filled bags and attach empty bags. The applicant assumes that his method is better suited for treating large volumes of oil, e.g. a flake that is 1.6 km or more in diameter.

Claims (18)

1. Method for substantially removing oil that has been released into salt water or fresh water, comprising encircling the oil with a fine-mesh net of considerable length, which is connected to floats and holders in such a way that the net is kept mainly vertical , and causes or enables the oil to move to an area near a selected part of the net, and for the oil in this area to be collected from the water surface and taken to a suitable container. 2. Method as set forth in claim 1, in which the fine-mesh net is placed to separate an oil slick from a nearby shoreline. 3. Method as stated in claim 2, in which the elongated net is placed a short distance outside the shoreline, in such a way that the effect of wind or tide (or both if these work together) is to bring the oil to an area near a selected part of the network, and that the oil in this area is then transferred to a suitable container, e.g. using pumping or a mechanical scoop. 4. Procedure for collecting oil that has been released into open water, comprising encircling the oil with a fine-mesh net of a substantial length, which is connected to floats and holders in such a way that the net is held approximately vertically and acts to encircle the oil. 5. Method as stated in claim 4, in which one end of the net is anchored and the net is deployed from a ship in such a way as to form a loop with an open mouth. 6. A method as set forth in claim 4 or 5, in which the mesh used has a mesh size such that the holes have a largest dimension of approximately 2.5 mm. 7. Nets for use for collecting oil on the surface of open water, characterized in that it has a small mesh size as indicated, that it has a length greater than 1,000 m, and that it is connected to buoys in such a way that it can float approximately vertically with a significant part of its height above and a significant part of its height below the water level. 8. Net as stated in claim 7, which is also connected to floats. 9. Net as specified in claim 7 or 8, in that at least 33% of the height of the net is above the water level when floating. 10. Net as stated in claim 9, in that at least 45% of the height of the net is below the water level when floating. 11. Netting as specified in claims 7-10, which has a mesh size such that the holes have a largest dimension of approximately 2.5 mm. 12. Net as specified in claim 8, the floats being made of or coated with an oil-absorbing material. 13. Nets as specified in claims 7-12, the buoyant floats being made of or coated with an oil-absorbing material. 14. Net as set forth in claim 13, comprising a front cable and a rear cable connected to the buoys and the net. 15. Method as set forth in claims 1-6, in which the net is drawn in from the sea using a net drum device carried by a vessel and having rollers defining a pair of slots, through which the net is drawn, during the draw-in, by operation of one or both rollers. 16. Method as stated in claim 15, and which comprises that a force is exerted on one of the rollers in the direction across the web, in order to increase the clamping force exerted against the web by the rollers. 17. Method as specified in claims 1-6, 15 and 16, in which the net, to which buoys are attached, is deployed from an aircraft. 18. Method as stated in claim 17, in which the net is deployed from a helicopter.