The present invention relates to certain floatable devices for absorbing spilt oil from a surface, in particular a water surface. It also relates to the use of the floatable devices for absorbing spilt oil and to a method of manufacturing such floatable devices.

It is well known that during marine oil well drilling, oil production, and oil transportation operations the possibility exists for oil to be spilt, which will then float as a film on the water, being subject to drifts and currents which may eventually wash the spilt oil or a less volatile part of it ashore.

Previous proposals to deal with spilt oil on beach or water surfaces include so-called booms, i.e., floatable tube-like structures having an oil absorbing material disposed near their circumference (e.g., WO 93/04236 A1). Such booms have primarily a barrier effect, in that they separate the contaminated water surface from clean areas; their secondary effect is to absorb oil coming into contact with the booms. In practice, it has become clear that the effectiveness of known booms is unsatisfactory.

It is also known, in principle at least, to drop hydrophobic mats onto oil contaminated water or other surfaces, and to recollect such mats after some time (e.g., US 6,506,307 B1). Again, in actual practice, it has become clear that it is quite ineffective to deal even with a medium-sized marine oil spill in this manner.

Patent document US 3,679,058 discloses a water-floatable modular device according to the preamble of claim 1, and in particular an oil absorbing boom comprising an elongated flat tubular sleeve of polymer netting having pouches each enclosing within itself one flat elongated slab or bat of polymer material arrayed end to end, the pouches sufficiently spaced apart to permit accordion folding of the sleeve at fold lines between adjacent bats, with a tension bearing rope or cable being positioned within the tubular sleeve alongside the bats.

Patent document US 3,904,528 discloses a method of manufacturing a floatable modular device according to the preamble of claim 7, and in particular a process of making an oil absorbing element comprising stitching together and heat sealing three sides of two water impervious sheets to provide a seal against the ingress of water, placing one comb-like absorber inside, and folding double and stitching a fourth side of the sheets to form a seal therealong.

It is an object of the present invention to suggest a device, its use, and its method of manufacture, with which the detrimental effects of marine oils spills can be reduced in a more effective manner. This is accomplished by the device of claim 1, the method of claim 7, and the uses of claims 8 or 10.

According to a first aspect, a device for absorbing oil from a surface is modular and floatable, and comprises a generally disk-shaped floatable cage tapering towards the periphery of the cage in a peripheral region thereof, and a water-repellent strip-shaped oil absorbent accommodated in the cage. The cage further comprises at least one connector element configured for joining plural ones of the modular devices together, to form an articulate oil absorber in which the individual cages are oriented in parallel to one another. Polyolefins are useful as water-repellent material.

In embodiments, the at least one connector element includes connecting structure configured to support the plural ones of the cages in a non-coplanar, face-on manner as a stack, in which stack the peripheral regions of the mutually adjacent cages form a corrugated envelope. In one example, each cage may have a central eye, and all cages are arranged on a common rod or tube passing through the eyes. The cages may be round, or generally polygonal.

In embodiments, a stack of mutually connected devices results, wherein the stack may include connecting structure configured to connect a top or bottom of the stack to the top or bottom of an adjacent, like stack in an end-on fashion. In this manner, a chain of stacks can be formed, each stack constituting a member of the chain. In some embodiments, a cushion may be interposed between the connected stacks. E.g., a smaller number of disks than the number accommodated in each stack may be arranged between adjacent stacks, to form such a cushion, allowing some relative bending of the connected stacks.

In another embodiment, there are plural connector elements on each modular device, each configured to be joined with a corresponding connector element of an adjacent, like modular device in a coplanar, edge-on fashion, to form a one- or two-dimensional array, in which array each modular device has a generally polygonal disk shape, such as rectangular or square.

In this embodiment, each modular device takes the shape of a mat, with plural eyes around its periphery. E.g., the rims may be folded in the region where the eyes are formed to provide enhanced stability. Neighboring mats can then be connected by connecting means such as loops made of a plastic material, to form an array of mats matching e.g. the size of the oil spill.

In an embodiment, a stack of mutually connected modular devices of this sort is formed before actual use, wherein connected adjacent ones of the generally polygonal modular devices are folded upon one another in a direction transverse to the plane of the modular devices. Usually, the devices are placed horizontally, and stacked vertically.

According to another aspect, a method of manufacturing a floatable modular device for absorbing oil from a surface comprises providing a first, grid-like sheet made of plastics, positioning a water-repellent strip-shaped oil absorbent on the first grid-like sheet, positioning a second sheet on the oil absorbent, and then welding the first and second sheets together at their peripheries, with the oil absorbent in between, wherein peripheral regions of the first and second sheets are bent towards one another. Depending on which device is to be manufactured, the sheets may be round (circular or oval) or polygonal (such as square or hexagonal). Both sheets may be grid-like, or else only one of them, the other being oil-impervious, for certain on-shore applications.

According to a further aspect, the stack of mutually connected modular devices may be used for absorbing oil spilt on a water surface, comprising connecting plural ones of the stacks as a chain and disposing the chain onto a part of the water surface in a vicinity of the part of the water surface on which the oil has been spilt. In embodiments, the oil has a drift direction, and the chain is disposed transverse to the drift direction, wherein the stacks are oriented such that the individual cages are oriented such that their thickness directions extend transverse to the drift direction of the spilt oil. In this manner, the chain may serve as a barrier to the oil, while the water may flow relatively freely through the vertically arranged cages, in this way enhancing the amount of oil absorbed as compared to a structure which also blocks the flow of water. The drift direction may result from a radial motion of the oil away from the source of the spill, and/or a linear motion due to a current or wind action. Usually, near a coastline the drift direction is transverse to the coastline, eventually washing spilt oil ashore.

According to a yet further aspect, a stack of mats is used for absorbing oil spilt on a water or coastline surface, comprising unfolding the stack and disposing the mats as a one-dimensional or two-dimensional interconnected flat array onto the spilt oil or onto a coastline area to be protected from the spilt oil. In the former case, each modular device may have two cage faces made of grid-like sheets, such that the oil absorber is accessible to the oil from both faces, and the stack is used on a water surface on which oil has been spilt. In this manner, both oil from underneath and oil sprayed on the top surface by wave and wind action can be absorbed. In the latter case, each modular device has one cage face made of a grid-like sheet, the opposing cage face made of an oil-impervious sheet, such that the oil absorber is accessible to the oil from only one face, and the stack is used on a coastline surface on which no oil has yet been spilt, with the oil-impervious face down and the grid-like face up so as to protect the coastline surface from oil to be washed ashore.

In embodiments, the absorbent material and/or shape and/or the number of cages per stack is selected in dependence of the oil grade. E.g., more viscous oil may call for fewer disks per stack, and/or less absorbent per module, and vice versa.

In further embodiments, the disposed modular devices are later recollected along with the absorbed oil. Furthermore, the modular device may be burnt together with the absorbed oil so as to release thermal energy, and a part of the thermal energy so released may be converted into electrical or mechanical energy.

The invention will now be described with respect to the accompanying drawings:

Figure 1

shows a stacked-disks module according to a first embodiment;

Figure 2

shows an end-on view of the module of Figure 1; and

Figure 3

shows a mat absorber according to a second embodiment.

According to the first embodiment of Figure 1, a number of 15-25 individual disks 3 is stacked on a common center rod or tube 5, to form a generally cylindrical module 1. The stack is held together by end grids 7, which end grids are in turn connected by a number of 3-8 outer tubes 17 (in the example, 5 tubes are shown). The end grids 7 may have a star shape as shown (with 5 radial struts 19, one of which is shown dashed).

With respect to Figure 2, each individual disk 3 is round in shape and doughnut-shaped in cross section, having an outer peripheral region in which the thickness gradually tapers towards the rim. Each disk has faces made of grid-like polyethylene sheets, and an interior made up of polypropylene strips. The polyethylene sheets may have a weight of 300-400 g/m², with openings of 7-10 mm mean size. The strips may be 70-120 mm in length, 3-5 mm in width, and 0.5-2 mm in thickness. Generally, the width/thickness ratio is in the range 1.5-10, with 3-5 preferred. While the size D of the disks depends on the intended use, it has been found that 30-100 cm is most useful, with 40-70 cm preferred. The overall diameter D' of the module will be slightly larger, by about 5 to 10 cm. The strip-shaped absorber material (250-350 g for a 50-60 cm sized disk) allows for a loose packing avoiding dense clots. Therefore, water may pass relatively unrestrictedly through the bulk of the module, the created turbulence carrying the oil to the absorber.

The method of manufacturing the individual disks includes placing a proper amount of the oil absorbent polypropylene strips onto a lower grid-like polyethylene sheet, then placing a like sheet on top, and welding the sheets together at their peripheral rims 21.

In the embodiment shown in Figure 1, 25 disks are housed inside each module 1, with 5 further disks 15 mounted on an outward extension of the center rod 5, held by an end disk 9 of the rod.

Two cables 11 (polypropylene) with hooks 13 are led through two (non-adjacent ones) of the 5 outer tubes 17, for connecting adjacent modules 1 to one another. In the connected state, the 5 external disks 15 fill the space between adjacent modules 1. In this manner, a chain of modules 1 can be disposed transverse to the expected drift of spilt oil, the oil everywhere encountering an oil absorbing module 1. A typical size of a module would be 0.5 m to 1 m in length L including the 10-20 cm extension L" for the outer disks 15 (length of main body L'=L-L"). Each module of this type can absorb more than 100 and up to 150 l of oil, e.g. 110-120 liters for a module 60 cm in diameter and 75 cm in length, weighing only 12 kg dry.

It may be noted that on account of the density of the plastic material of 950-965 kg/m³ the inventive structures have sufficient buoyancy to float even in fresh water, more so in salt water. The bulk of the structures will, however, sink below sea level and therefore is able to absorb oil from the water passing through it. At the same time, no oil can pass through underneath the modules.

In the second embodiment of Figure 3, a generally rectangular or square mat 10 is shown, with top and bottom sheets of the same grid-like polyethylene material as described above, and also the same filling of oil absorbing polypropylene strips. In this case, the rims of the pillow are folded (indicated by dashed lines), and eyes 22 (circular or oval as shown) formed therethrough to provide connectability. Welding the rims may be dispensible where the eyes are configured to secure the rims against unintended reopening.

Such mats 10, the size of which may vary e.g. between 50 cm and 100 cm side length, can easily be interconnected to form a two-dimensional array of in principle unlimited size. In one approach, such interconnected mats are folded atop one another in the shape of a stack, ready to be unfolded when used. In this manner, it is possible to quickly dispose large numbers of mats onto an oil-contaminated water surface or beach area, while still being able to later recollect the oil-filled mats as easily. Each mat of this type (~2 kg/m² of absorber) may absorb more than 10 and up to 20 l of oil, e.g. 16 l per square meter.

It is also contemplated to use mats of this type together with the modules, in order to absorb the spilt oil when it has accumulated upwind (or upstream) of a chain of the modules of the invention.

In a variant, one of the two faces of each mat is not grid-shaped, but is made of an oil-impervious sheet. In this embodiment, mats can be placed e.g. on a beach or other coastal area which is not yet contaminated. When spilt oil is later washed ashore by wave and wind action, it will be absorbed by such mats covering the beach, and will not contaminate the beach.

The oil-filled modules or mats can be recollected and removed from the water surface, significantly reducing the amount of oil present on the water. The modules or mats may be burnt together with the oil, in order to use the thermal energy so released. In order to provide for clean burning, no halogenated polymer should be used in the manufacturing of the modules and mats, although the use of polyolefins as explained above is not strictly necessary.

Further modifications or variations will be readily contemplated by the skilled person, without departing from the scope of present invention as set out in the appended claims.