WO2012010175A1

WO2012010175A1 - Method and vessel for collection of oil from the sea

Info

Publication number: WO2012010175A1
Application number: PCT/DK2011/050277
Authority: WO
Inventors: Erik Ladefoged
Original assignee: Erik Ladefoged
Priority date: 2010-07-20
Filing date: 2011-07-15
Publication date: 2012-01-26

Abstract

Collecting oil on large sea areas occurs by means of a supertanker which is provided with externally added loading boxes (2), the outer walls (10, 22) of which having a horizontal slot (26) which enables an inflow of the oil contaminated water layer, which falls down into the loading box (2), and which from its bottom area is led through holes (14) in the ship side for further drop into a collecting tank (38). This tank is connected with other tanks (42, 44) separating off the water which has been taken in together with the oil, and the thus separated water is pumped back to the sea whereby the ship can collect a large useful load of oil with low water content. It is directly provided that together with the oil layer there is loaded a large amount of water as this determines an oil influx with great capacity. The intake slot (26) is designed in a wall part (10, 22) which is automatically vertically movable in dependence of a measurement of the sea level position relative to the ship such that the slot (26) is always at level with the oil-contaminated layer, both by the generally increasing draught of the ship in the sea and by occurring wave movements in the water.

Description

Method and Vessel for Collection of Oil from the Sea

Field of the Invention

The present invention concerns a method for collecting oil on the sea and of the kind indicated in the preamble of claim 1. The invention also concerns a vessel for performing the method according to the invention.

Background of the Invention

In later years, oil pollution or contamination of large areas of the sea has become an increasing problem which may assume the character of natural catastrophes for which no relief can be provided in reality. Several methods are developed for delimiting and removing oil contamination on water surfaces, but with the hitherto attained capacities for removal of oil, an efficient cleaning of large sea areas will be economically and practically impossible to perform within a reasonable time frame.

Object of the Invention

The invention has the object of indicating a method by which an oil leak in a large sea area can be controlled with high capacity in an economically viable way. The invention is of the type of control methods by which it is aimed at collecting the oil layer on or at the water surface instead of neutralising the oil by means of chemical precipitation or neutralising agents as the use of such agents is very costly and even of doubtful value by a total environmental consideration.

However, collecting oil is not only environmentally advantageous but furthermore economically in that the collected oil in itself may represent an economic value since it can be recycled. Even if oil collected at sea will have reduced value, the oil will be usable for making some less distilled products.

Oil on an extended water surface usually appears in one or more layers with very small thickness. If or when it is attempted to "skim" such a thin layer of oil, the collecting capacity will unavoidably be very small. The invention is therefore based on the view that for attaining high collecting capacity, it is necessary that a considerable amount of water is collected together with the oil layer, where the water subsequently is just separated off the collected mixture of oil and water.

Description of the Invention

The invention therefore aims at providing realistic possibilities for collecting and treating oil-contaminated water with great capacity.

By the method according to the invention is utilised one or more very large ships, preferably so-called supertankers, which nowadays are even available as relatively cheap excess products from a finished development stage, as such a ship is equipped with means for allowing inflow of the surrounding water at a level which relative to the ship corresponds to the occurrence of an oil-contaminated water layer, most often the surface layer of the water, and with means for performing at least a rough separation of water and oil, preferably for continuously separating off clean water which is pumped back to the sea, and oil or a water-oil mixture with high oil content which is temporarily stored in the ship and transported ashore for reworking in a refinery according to need.

Hereby it is of importance that the very large ship will have such collecting capacity that it advantageously may be loaded with very large amounts of water, why one may substantially reduce the otherwise great demands to the collected material consisting practically only of the desired oil. It is such demands which by the hitherto known proposals have resulted in cleaning capacities which with regard to cleaning of larger sea areas have been almost hopelessly insufficient. To this is added that by collecting an attempted thin water or oil layer, there is a considerable risk that the cleaning becomes insufficient whereas by taking in substantially more water than necessary, a more efficient cleaning will be achieved.

A supertanker has very large tank capacity which enables extensive separation of clean water from the water-oil product flowing into the ship as well as the supertanker has the required pump equipment for bringing the separated clean water back to the sea. The remaining oil-rich product can be stored in special tanks that are emptied when calling at refinery/harbour. As the tanks of the ship are filled, the ship will increase the draught in the sea, whereby the relevant inflow level relative to the ship will be elevated. It is a variation in height of several metres, and even if a large water inflow is tolerated, it will not be realistic to operate with a fixed overflow edge at the ship as the inflow will be unrealistically high as the ship is filled and thereby depressed into the sea. It is therefore an essential feature by the invention that the ship is equipped with a water intake limited by a lower overflow edge part which is vertically adjustable in relation to the ship such that it can generally assume a fixed vertical position relative to the sea level irrespective of the vertical movement of the ship relative to the sea level (the actual draught of the ship).

Even by cleaning large sea areas it must be considered that appreciable wave movements may occur in the water whereby particularly a ship will be exposed to the fact that an oil-containing water surface will continuously rise and sink in relation to the ship itself. By the invention it is therefore of particular importance that the overflow edge part is vertically adjustable, not only with reference to the general position of the ship in the sea, but also in a more dynamic way with reference to the occurring wave movements such that the overflow edge part objectively is moved in such a way that it assumes an approximated ideal position relative to the sea level. Hereby, it is of course important that the ship is equipped with means for detecting the immediate relative position of the sea level opposite a considered overflow edge part and with means for in dependence thereof to perform a rapid change of level of the edge part. Thereby it will be possible to control this edge part in such a way that it is rather accurately permanently situated just below the sea level, irrespective of the movements of the sea and the ship; for the sake of simplification in practice is used a horizontal overflow edge of considerable length, e.g. 5-8 m, and in order to achieve the said result under wave movements, the ship is then just to be positioned substantially along the waves. It may very well occur that a polluting oil layer is located a distance down below the sea level, and in such case the water intake over the overflow edge is to be almost unrealistically large in order to collect the oil layer. However, according to the invention the overflow edge is constituted by the lower edge in a slotted opening in a upwardly extended plate part which as a whole is moved up and down for adaptation to the relative water movements, whereby the water inflow will be limited by the height of the slot such that the operation can be performed with the slot disposed at a greater or lesser distance below the sea level. The upper edge of the slot is preferably formed by a separate plate part which is vertically adjustable relative to the lower plate part, but otherwise following its movement whereby the effective height of the slot will be adjustable. An oil layer hovering down in the water may very well be of varying thickness, and this thickness may very well be detected with a suitable measuring equipment such that both the vertical position and the slot height can be adjusted continuously. The slot height still has to be greater than the thickness of the oil layer itself such that a rather large amount of excess water is loaded for increasing the collecting capacity for the oil.

It will be very complicated to form a vertically displaceable, long slot directly in connection with a ship side. By the invention is proceeded in the way that externally of the ship side there is constructed one or more upwardly open boxes, the outer wall of which being constituted by a plate which is vertically displaceable relative to the sidewalls of the box and to its bottom wall, against which walls the outer wall is sealed displaceably; water flowing in over the upper edge of the outer wall may perform a free fall down to the bottom wall of the box, and immediately over it some holes are formed in the ship side itself which do not penetrate the frames of the ship side, additionally allowing the water flowing into the box to perform a renewed fall in through the holes and further on down internally of the ship to lower collecting tanks therein.

These free fall possibilities are important for a high intake capacity, and moreover it appears that the free fall with associated strong water impact down has a favourable effect with regard to breaking up the oil/water layer for later concentrated separation off of the oil. Description of the Drawing

The invention is explained in more detail below with reference to the drawing, in which: Fig. 1 shows a view of a supertanker provided with an embodiment of a facility according to the invention;

Fig. 2 shows a schematic perspective view of a part of the facility shown in Fig. 1 ;

Fig. 3 shows a schematic sectional view of a part of the supertanker shown in Fig. 1 ;

Fig. 4 shows a schematic perspective view of an alternative embodiment of a facility according to the invention;

Fig. 5 shows a perspective view of the facility shown in Fig. 4, provided externally on the ship;

Fig. 6 shows a perspective view of the alternative facility provided externally on the ship; and

Fig. 7 shows that the alternative facility can assume a position at right angles to the ship side.

Detailed Description of Embodiments of the Invention

The supertanker shown in Fig. 1 is provided at both sides with a pair of attached, slightly projecting boxes 2, of which a single is shown in more detail in Fig. 2. It consists of two vertical sidewalls or side members 4 which are welded on the ship side 6 and designed with mutually facing guide grooves 8 for opposing side edges of a front plate 10, and a bottom plate 12 with the outer edge of which the front plate 10 is in sealingly slide contact as well as this plate 10 is in sealing engagement with the guide grooves 8. Right above the bottom plate 12, some holes 14 are formed in the ship side 6, of which only one is shown.

The upper edge of the front plate 10 is designated 16. The vertical outer edge parts of the plate 10 are extended upwards in column parts 18 which are formed with mutually facing open guide grooves 20 for the side edges of a separate plate part 22 which in a vertically adjustable way is supported by the front plate 10 via a pair of hydraulic cylinders 24 such that between the plates 10 and 22 a horizontal slot 26 with variable slot height is formed. The outer edge faces of the plate 10 and the columnar parts 18 are designed with vertical tooth rack elements 28 that each interact with a drive gear wheel in a gear motor device 30 fastened to the side members 4 such that the front plate 10 and the upper plate 22 supported thereby can be displaced up and down by activating the gear motors 30. It is to be noted that a corresponding controlled displaceability can be achieved in other ways, e.g. by using upright projecting hydraulic cylinders inserted between the front plate 10 and the ship side. At the upper edge of the ship side 6 and above the shown box device there is provided a projecting arm 32 carrying distally a sensor head 34 which by suitable means, such as ultrasound, is adapted to contribute to detection of the immediate vertical position of the sea surface in relation to the ship. By means of a not shown control unit, this sensor head is connected with the gear motors 30 such that the latter are continuously activated for moving the front plate 10 in such a way that its upper edge 16 is correspondingly located a predetermined distance under the sea surface or under the underside of the oil layer, both by varying draught of the ship and by large wave movements occurring in the water. The ship is kept oriented in the sea along the waves such that opposite the box 2 they appear as a generally rising and falling horizontal surface level.

The height of the slot 26 can be preset, or it can be automatically adjusted depending on a continuous measurement of the thickness of the oil layer, which, however, is particularly relevant by collecting oil layers located under the sea surface.

The oil layer at the ship will therefore, together with a relative large amount of water, run in over the edge part 16 and thereby fall down to the bottom part 12 via a free fall of several metres, see also Fig. 3. At the impact, the oil layer is broken and mixed with water, which appears to facilitate separation of the oil later.

The water/oil mixture (Fig. 3) runs from the bottom of the box 2 and further in through the holes 14 and down into a receiver tank 38, again via a considerable free fall, as the liquid level in the tank is kept low by means of a pump 40 continuously pumping liquid over into a separating tank 42 in which the oil is separated on top of the water. As we all know, a supertanker has a very large tank capacity, and there will be good possibilities for using many tanks for simultaneous and successive separation of the oil. In Fig. 3 is only schematically shown that the bottom water in the tank 42 is pumped over into a water tank 44 from where the water is pumped out through a line 46 back to the sea whereas the oil in the upper layer of the tank 42 is pumped over into an oil tank 48 which also receives the residual oil from the water tank 44. The required separation facility does not need to be described in detail as it can be arranged in many different ways according to known principles. It is only to be emphasised that a large tank capacity is suitable, both so that the oil intake can occur with great capacity, namely under simultaneous intake of large amounts of water which then are to be separated off, and in order that the separating of the oil can occur in a simple mechanical way without using expensive degradable chemicals; hereby it can be expected that the collected oil can show a substantial recycling value, depending on the degree of decomposition to which it has been exposed in a natural way before collection. However, the oil will normally at least be usable for making some less distilled products and will even thereby present a significant value. The separated clean water can be pumped back to the sea in great amount whereby the ship can accommodate a large useful load of separated oil besides a remaining content of an insufficiently separated amount of oil/water. The ship may by itself sail the oil to a refinery harbour, or the oil can be picked up by smaller tankers. It is prior art that cheap and harmless chemicals can be added to oil/water mixtures in order to further a well-defined separation, and the ship may suitably be provided with dosing devices for such chemicals which may be added with good effect at the mentioned impact areas for the inflowing and falling liquid. In particular by collecting the surface layer of the sea water itself it is unavoidable that by the preferred loading of the oil/water layer, some large and small foreign bodies will be introduced in the box 2. There may be provided a wide-meshed net that tapers outwardly in front of the slot 16, but the inlet area is preferably to be as open and free as possible. Within the large holes 14 there is preferably provided a collecting net or a net basket which can be replaced according to need or be provided in a movable system, e.g. a revolving system or a longitudinal transport net system.

Even if the overflow edge 16 or the slot 26 is controlled automatically to follow the relative movements of the sea surface due to wave movements, it is, however, desirable that the collection occurs by wave movements that are as small as possible. Since the ship by itself is an efficient wave damper, it may possibly with advantage be sufficient to let the inlet box or boxes at the lee side of the ship be operative, and for the same reason it may be sufficient to equip a given ship with inlet boxes only at one side. The ship should be moved along the waves at such a speed that an oil layer of reasonably great thickness in relation to the loaded water layer is loaded continuously. The optimal speed will thus be given by the thickness and nature of the oil layer where e.g. the temperature plays a significant role. A possibly more efficient utilisation of the collecting capacity can even be achieved in that the ship is moved in its own transverse direction for efficiently bringing the oil to the operative collection box or boxes at the "front side" of the ship. This movement may be established either by using a transverse propulsion system or simply by letting the ship, or in that case "the superbarge" be towed sideways by means of tugs, preferably in direction against the wind.

By such a sideways movement of the ship, the collecting capacity is considerably increased by using so-called "lances" projecting in a diverging V-shaped way from the intake opening or openings for forming long, projecting funnelling elements that guide a wide surface area of the sea against the relatively short inlet slots 26.

In the same way, however, by means of lateral, obliquely forwardly projecting lances or guides it may be achieved that the ship by moving in its own longitudinal direction can guide a sea surface area against the box 2, the area being considerably wider than the ship itself, whereby the oil collecting capacity of the ship can be substantially increased.

By collecting an actual surface layer of oil or similar, the upper plate 22 can assume a maximum elevated position 1 relative to the lower plate 10, but by collecting an oil layer hovering below the sea surface it is important that the height dimension of the slot 26 is adapted to the thickness of this layer, which may occur fully automatic on the basis of known measuring and control methods, as hereby it should be provided that the height of the slot is at least somewhat greater than the measured thickness of the layer in question as the intake capacity otherwise will be too small.

It has been emphasised above that the considered ship should be a "supertanker", but it will be understood that the object of the invention of course can be reduced in dimensions in such a way that it also includes smaller vessels that e.g. operate on shallow water, but still having a liquid intake with a relatively large component part of sea water, a condition for achieving a substantial collecting capacity. For the same reason, it is important in practice that the ship in itself is equipped with means for neutralising or preferably separating off at least a substantial part of the collected oil.

Instead of or in addition to disposition of the intake boxes 2 at the side of the ship, corresponding boxes may of course be disposed athwartships at the front and/or rear end of the ship. The outer walls of the intake boxes are not necessarily constituted by vertically sliding walls as e.g. the inflow edge part can be defined by the upper edge of a rollable wall which at the top is rolled around a roller which can be rolled up and down in dependence on the variations in the level of the sea surface in relation to the ship. In principle, it will be possible to operate with a separate intake barge from where the water/oil product is continuously transferred to the separating facility in the tanker, for example through a thick downwardly sloping hose; the intake barge may hereby possibly be of such character that it will automatically follow at least the larger wave movements in the sea, whereby in certain instances the vertical adjustability of inflow edge or slots parts may be abandoned.

However, it is advantageous to operate with liquid intake directly into a large ship as then advantage may be taken of the possible great fall height for the inflowing liquid. In practice it should be preferred that the ship has an approximately constant and substantial draught in the sea which is easily attainable in that from the start there is operated with a great load of ballast water which is pumped out as the ship collects water and oil from the sea as correction for the amounts of separated water which is also pumped out or discharged is made. Several advantages are achieved hereby, namely that operation can be performed all the time with great fall height for the inflowing liquid and that the slotted wall 10, 22 is only to be limited movable in relation to the ship, largely only corresponding to the maximum wave movements in the sea. Moreover, operational advantages can be achieved hereby with regard to discharge of separated water as the separation tanks may communicate with the sea like communicating vessels.

It is also to be mentioned that the overflow edge or vertical position of the intake slot possibly can be controlled directly by using suitable float pontoons which, as mentioned, also may present such edges or slots in themselves.

The required adaptation of commencial tankers may in principle be limited to means for securing the boxes 2 and for prepared inflow holes 14 in the ship hull. During ordinary operation, these holes may be closed by valve plates flushing with the side of the ship such that the valve plates do not give rise to any increased resistance against movement for the ship.

By mounting a box 2 at the outer wall of the ship hull it has been found by the invention to be innate that the entire box 2 can be moved vertically up and down along the ship side, whereby the side of the ship only needs to be designed with vertical guide grooves for receiving the box 2. Such guide grooves only cause minor irregularities of the ship side, and during normal operation of the ship, the grooves may even be filled with filling elements so that the resistance against movement of the ship is not increased appreciably hereby.

Naturally, there will be a long distance from a harbour at which a ship is provided with one or more collecting boxes 2 to a new spillage area, and therefore it is desirable that the ship can sail fast and without substantially increased costs after having received the boxes. This is achievable in that the boxes are brought on board together with particular associated equipment for enabling that the boxes during transport is stored on deck and only mounted at the side of the ship when the ship has arrived at the area, i.e. at sea.

Such a mounting operation at sea can be much facilitated by using the guide grooves at the side of the ship. As shown in Figs. 4-6, the box designate 50 can be mounted on a support frame 52 which is pivotably coupled to the area at the upper end of the guide grooves designated 52 in or at the side of the ship, and which by themselves retain the box 50 in that the latter engages a corresponding guide groove in the support frame 52. This and the box 50 may, as shown in Fig. 4, be transported lying on the deck transversely thereof, and for mounting the box 50 it will be sufficient by suitable crane equipment to pivot the support frame and the box up about the hinge area 56 to a vertical position from where the box 50 can be lowered for engaging the fixed guide grooves 54, Figs. 4 and 5. When the box has been slid completely down, the support frame can be folded down, cf. Fig. 6, after which the operation can be commenced.

By the embodiment with a separately vertically adjustable front wall 58 on the box 50, the front wall formed of a single plate item provided with a number of horizontal intake slots 60 which are each e.g. 10-20 cm high and each covered by a valve flap 62 which is hinged at the lower edge. These valve flaps 62 can be opened individually and gradually, and hereby it is possible to utilise the intake slot 60 which is closest to the water surface, as the plate 58 can be vertically adjusted for correct disposition of the slot in question. The plate 58 is movable in relation to the box 50 corresponding to at least the distance between the slots 60, i.e. as the ship sinks into the sea it is possible to switch to the superpositioned slot 60 by closing the valve flap 62 on the hitherto used slot in the upwardly displaced wall plate and by lowering it until the overlying slot is situated close to the water surface. A corresponding effect may be achieved if the wall plate 58 is stationary on the box 50 so that as the ship sinks, the entire box 50 can be hoisted upwards correspondingly until it can be lowered one pitch for activating the overlying slot. A slot height in the magnitude of 20 cm will normally be sufficient to provide such a strong inflow that the aim of the invention regarding a very large intake capacity is allowed for but not excessively. Frequently it may even be desirable to limit the maximum slot height, not the least by collecting of a below occurring oil layer, and the valve flaps 62 are very well usable for this purpose when they are controllable for gradual closing of the slots.

As indicated in Fig. 4 and 5, the box 50 is by means of the hinge 64 hinge connected with the slide part or parts interacting with the guide groove 54 at the concerned side of the box 50, whereas this at the opposite side is releasably connected with the corresponding slide part or parts interacting with the opposite guide groove. The box 50 will hereby be pivotable to the position shown in Fig. 7 perpendicular to the side of the ship as it can be retained in this position by means of suitable retention means, such as cables 66.

In this position, the intake openings 14 at the side of the ship will have to be closed. On the other hand, by the pivoting of the box 50 it will occur that an opening (Fig. 6) formed in the box side and which hitherto has been closed by a slide is brought to sealing contact with the side of the ship outside an additional intake opening 70 in the former, which opening hitherto has been closed by a gate 72 flush with the side of the ship. After pivoting the box 50, both openings 68 and 70 are opened up, after which the product flowing into the box will be conducted to the mentioned inner equipment via the intake openings 70. Hereby, the ship may possibly be able to collect the contaminated water in a desired way by sailing against the polluted area whereby an increased oil collection can be expected in that the wide supertanker cleaves or spreads the contaminated water layer for increasing the concentration of contamination along the sides of the ship such that the boxes 50 will receive the contaminated product in concentrated condition. Furthermore, the previously mentioned lances can be used for intensified collection of the contaminated product as such lances can be provided forwardly-outwardly projecting obliquely in the sailing direction from the outer side of the unfolded boxes 50. In the unfolded condition, the boxes 50 will of course give rise to a substantially increased resistance against movement for the ship, but in the same connection a significant phenomenon has been recognised which can justify the associated increase in power consumption to a great extent. It has been discovered that by the sailing forward of the ship in the area behind the unfolded boxes 50 an expected strong eddy formation occurs in the water, and that by this eddy formation an upwards movement of the material in the water contaminated layer down into the water arises, i.e. in water layers that normally lie below the sea level. These layers will thus be brought up to the surface immediately behind the unfolded boxes 50, and it is therefore a special feature of the invention that also at the rear side of the boxes 50 there by may be formed a vertically adjustable intake opening which during sailing forward can be located at the water surface, irrespectively whether at the front side of the boxes 50 there is possibly operated with a liquid intake at some distance below the sea surface.

By using boxes 50 which are displaceable upwardly and downwardly at the side of the ship there is allowed for the fact that the box as a whole can be influenced by a buoyant force from the water, meaning that means from above to keep the box depressed into the water to the desired position of the box should to be provided.

Depending on the dimensions of the ship, the dimensions of the box 50 can be a height of a few metres up to 20-30 metres, and a width of few metres up to e.g. 10-15 metres. The depth of the box may vary between e.g. 0.5 and 2-3 metres.

Claims

1. A method for collecting oil on sea surfaces by which the oil layer is brought to flow into a floating collecting container (2) by overflowing an edge part (16) thereof, by which as collecting container is used a vessel equipped with means for separating water from the loaded mixture of oil and water and for pumping the separated water back to the sea, as the layer of oil is allowed to flow over the edge part (16) together with substantial amounts of water, where as inflow edge part is used an upper edge part of an element which is height adjustable relative to the vessel, the element being actuated to assume a substantially constant vertical position relative to the sea level, irrespective of the vertical movement of the vessel in the sea, characterised in that the inflow edge part (16) is held oriented along the wave direction in the sea, and that it is controlled for moving up and down corresponding to the wave movement opposite the edge part (16).

2. Method according to claim 1, characterised by using an inflow edge part appearing as a lower edge (16) of a slot (26) in a wall element for limited loading of water and oil at a level below the sea level.

3. A vessel for performing the method according to claim 1, constituted by a tank vessel with a substantial excess capacity in relation to the oil loading capacity and with equipment for separating off substantial amounts of water coming from the loading of the oil layer combined with a water layer of relatively significant thickness, and for pumping the separated water back to the sea, characterised in that the inflow edge part is formed on a vertically movable element generally at a level below the sea level.

4. Vessel according to claim 3, characterised in that above the inflow edge part there is provided an upper wall element which is movable in height together with the inflow edge part, and the lower edge of which together with this forms an intake slot which can operate below the sea level, the slot height of which being preferably adjustable.

5. Vessel according to claim 3 or 4, characterised in that it is provided with means for detecting the elevation of the sea level relative to the vessel and in dependence thereof to adjust the level of the inflow edge part correspondingly by occurring general change of the position of the vessel at sea and by wave movements occurring at sea, respectively.

6. Vessel according to claim 3, 4 or 5, characterised in that the inflow edge part is constituted by an upper edge of an outer wall element of a box-shaped extension on a side part of the vessel, in that close to the bottom of this extension there is formed holes in the side of the vessel for leading in the inflowing oil/water mixture for further flowing down into a collecting tank in the vessel.

7. Vessel according to claim 6, characterised in that the box-shaped extension is substantially vertically oriented such that the oil/water mixture loaded therein can perform a free fall in the magnitude of several metres.

8. Vessel according to any of claims 3-7, characterised in that it is constituted by a so-called supertanker, the tank facilities of which are utilised for continuous separating off the greater part of the loaded water.