NO314851B1 - Installations for the removal of contaminated pulp and use - Google Patents

Description

■FACILITIES FOR THE DISPOSAL OF THE CONTAMINATED, FOR EXAMPLE, PARTICULAR MASS LYING ON THE SEA BOTTOM, AS WELL AS THE USE OF A SPECIAL LIQUID/GASEY TRANSPORT MEDIUM FOR SAID MASS

The present invention relates to a facility for the removal of contaminated, for example particulate matter lying on the seabed. The plant is of the type that appears in the introductory part of patent claim 1.

The invention relates to a facility which, among other things, can be used to carry out work operations as described in the application, but which will also be able to be used while achieving special advantages linked to this invention in connection with similar methods for removing various , contaminated masses from the seabed.

The plant according to the invention is of the kind that exhibits a constructive structure as indicated in the introductory part of the first apparatus claim.

The facility can be applicable and useful for a number of removal operations where contaminated, particularly particulate masses are to be taken up from the seabed and transported away,

among other things with a view to improving the environment by raising the quality of the seabed and seawater, with the intention of improving the conditions for marine animal and plant life. However, the present invention is primarily linked to two main tasks, namely the removal of drilling cuttings on the seabed around sea-based platforms, and the removal of other polluted, particulate material and mass from the seabed in fjords and harbor basins.

However, these specifically stated uses are not limiting for the invention's scope of protection as stated in the patent claims, which however state that the bottomed mass to be removed is contaminated and that a liquid/gaseous transport medium is used for the removal.

In accordance with the invention, the aim has thereby been to provide a plant of the type specified in the subsequent patent claim 1's preamble, where - compared to traditional and other known technology - significant advantages are achieved both economically and when applies to capacity and efficiency.

According to the present invention, these purposes are realized by the facility being constructed constructively in accordance with the characterizing part of claim 1.

In accordance with the invention, one proceeds in such a way that the liquid, or possibly gaseous, transport medium for the movement of said polluted mass from the seabed to a possibly temporary emptying point, normally above the sea surface, which transport medium which has been contaminated by contact with said polluted mass, is recycled , where return liquid (or gas) is injected into the free, lower end part of a suction hose for removal of mass on the seabed, in the form of an upward jet at a short distance from the outer end of said suction hose, which is maneuvered, for example, from a remote-controlled underwater vehicle (ROV ) and is connected at the top with a riser pipe for the further, upward transport of contaminated mass of particulate solid material using - apart from the first circulation - likewise contaminated transport liquid (or gas). The use of recycled, contaminated transport medium has been shown to have no negative impact on the process whatsoever. According to the invention, conditions are created for control/management of the mixing ratio between mass and transport medium (usually liquid). The mixture of particulate mass and transport liquid will be subjected to sieving and separation in the surface position, and the pollutants that recycled transport liquid contains thus have a smaller particle size than those retained by the sieves of the vibrating screen and usually consist of liquid pollutants.

Recycling of contaminated transport fluid results in large financial savings. Not least, with known technology, it is expensive to take care of and clean/remove contaminated transport fluid. A practically closed circuit for flowing transport fluid is advantageous for the capacity and efficiency of the invention.

The mass absorption process at the seabed can be subject to audio monitoring. This could be implemented by placing a hydrophone on the suction hose, positioned at a certain distance from the suction end.

The facility according to the invention comprises a hose/pipe-shaped transport device with a longitudinal extent that corresponds to the approximate distance from the mass removal point on the seabed and to a temporary emptying/drop-off point, which transport device is preferably based on the so-called " gas lifting principle" (where compressed air can be used). The transport device preferably comprises an ROV-maneuvered suction hose which is designed to be able to suck in contaminated mass from the seabed at its free end, which suction hose should be connected to a riser at a suitable distance from the work site on the seabed, especially at great depths.

At large depths which correspond to large lifting heights attributed to said riser, the riser should be designed with an increasing diameter (gradually or in stages) towards the outlet which is located above the surface position. This limits speed and pressure drop due to gas expansion (gas supplied to the riser from the gas lift pipeline).

For example, at the transition between the lower suction hose and the overlying riser in the extension of the suction hose, a gas lift can be connected in the form of a supply hose for compressed gas, for example compressed air.

■^The supply hose is connected at the top to a compressor which is placed above the water surface.

A lower end part of a return hose for contaminated transport liquid (or gas) protrudes into the lower end part of the mass transport hose (suction hose). The end of the return hose can be fitted with a jet nozzle.

A channel/pipe/hose for recycled gas for the gas lift can possibly lead to the compressor from a collection and separation tank. This channel etc. can possibly be bypassed if it is not required to recycle this gas.

From the collection container, which is either designed as a separator or includes a separation device, leads partly an outlet for transported up contaminated mass which can consist of particles of different sizes, and partly an outlet for excess liquid, connected to the mentioned return liquid hose for contaminated transport liquid.

The return hose can be connected just below the collection and separation container to a branch pipeline with a shut-off valve in the immediate vicinity of the return hose.

If the gas used for the gas lift is not to be recycled, the collection and separation container, which may consist of several parts, can be open at the top.

Above the sea surface, a pump may possibly be installed in the return hose for contaminated transport liquid.

This pump can be bypassed if the hydrostatic pressure from the difference in height is sufficient to feed contaminated transport liquid downwards, so that it arrives at said nozzle with a satisfactory flow rate.

The aforementioned nozzle for injecting contaminated transport liquid into the end part of the suction hose for mass on the seabed can be located in a constriction in the end part of the suction hose, preferably some distance from its free end. Thereby, a venturi effect can be achieved to increase the suction effect of the hose on the mass. The nozzle can also be placed eccentrically in relation to the axis of the suction hose end or inclined, whereby in such cases a helical flow is created and maintained which facilitates the feeding of the mass.

A non-limiting example of a preferred embodiment is shown in highly schematic form in the attached single drawing, where a plant for removing contaminated mass from the seabed is shown in one usable working position.

In the figure, 10 denotes the seabed and 12 the sea surface, while the reference number 14 denotes a pile of contaminated particulate mass which exhibits mutually deviating particle sizes, for example drilling cuttings.

The facility for removing contaminated mass from the seabed comprises a suction hose 16 which can consist of a relatively long, flexible hose and forms the lower part of a continuous run which likewise comprises a riser 18 which with its upper part protrudes above the sea surface 12 and there has a twice 90° angled section, so that the outlet 20 of the riser 18 (and thus the common run 16,18) is directed downwards, into the upper area of a storage and separation container 22.

At great depths, corresponding to great lifting heights, the riser 18 can be designed with an increasing diameter towards the outlet. Thereby, flow rate and pressure drop due to gas expansion are limited.

The container is equipped with a vibrating screen (simplified shown in the form of a sloping screen) 24 for separating the mixture of transport liquid and contaminated mass from the pile 14. The reference number 26 suggests a transition piece between the suction hose 16 and the riser 18. The main thing is to create one race 16, 18 which extends from the work site on the seabed 10 and to a processing site, the container 22, above the sea surface 12.

The gas lift in the riser 18 is implemented by means of a supply hose 28 for compressed gas, for example and preferably in the form of compressed air, from a compressor 30. The principle for gas lift is well known: The gas flows, as a result of its specific weight, upwards in a demarcated run (18) and takes with it liquid and other things that may be in/be added to said run.

If this compressed air is to be taken care of when it arrives at the container 22 and you want to recycle it, the container 22 must be made with a closed top, and a channel 32 (dotted) must be created between the container 22 and the compressor 30.

From the vibration screen of the container 22 in the form of a longitudinally sloping screening disc 24, there is an outlet 34 for contaminated mass of particulate dry matter, for example drilling cuttings from the pile 14 on the seabed 10. The contaminated mass particles are brought up to the surface position, and the further transport is to that extent irrelevant to the present invention. In the drawing, such mass is shown as it leaves the container 22 and is on its way out of the outlet 34. This mass will of course be taken care of, for example, via an underlying chute for further transport.

In the starting position, it is assumed that the lower area of the container 22 is filled with a suitable volume of transport liquid.

The lower area of the container 22 filled with transport liquid in the initial position is connected to a bottom drain 36 which is primarily connected to a hanging, very long hose/pipe line 38 for transport liquid. After the first circulation through the plant, the transport liquid is contaminated as a result of its contact with contaminated mass and the liquid then constitutes recycled transport liquid.

The hose 38 is therefore referred to as the return hose for contaminated transport liquid.

At its lower end part, the return hose 38 is bent twice, and it protrudes with its outer end 40 into the end part of the suction hose 16. The suction hose 16 is shown in a suitable inclined position in relation to the seabed 10, corresponding to an appropriate position in relation to the mass pile 14, and the outermost end part 40 of the return hose can have a corresponding slope so that the mouth of the return hose 40 is placed coaxially in the lower section of the suction hose 16 .

The nozzle in the angled end portion 40 of the return length 38 can be located in a constriction (venturi) 42 in the enclosing portion of the suction hose 16 to increase its suction effect.

!S

In the aforementioned free end part 40 of the return hose, a nozzle for injection of the transport liquid is fitted. The nozzle can be made up of a nozzle in which a jet pump is inserted, in order to thereby implement an efficient feeding of mass from the pile 14 and at least up to a place in the suction hose/riser where the gas from the supply hose for compressed air in the gas lift is starting to take effect.

The suction hose 16 is close to the transition 26 to the riser

18 mounted a hydrophone 44, an underwater listening device, for audio monitoring of the suction process.

A branch line 46 with shut-off valve 48 is connected to the return hose 38, just below the bottom of the container 22, through which any excess liquid can be drained off.

Immediately downstream of the branch line 46, the return hose 38 is connected to a pump 50. This pump 50 can be bypassed if the hydrostatic pressure from the height difference is sufficiently high.

Claims (9)

1. Installation for the removal of contaminated, for example particulate matter from a position on the seabed, comprising means for in an upwardly directed run (16,18) to initiate a flow of mass and a transport medium to an overlying position, preferably above the sea surface, where the upwardly directed run in hose- /pipeline design (16,18) is assigned to means (28,40) comprising at least one gas supply hose/pipeline (28) connected to the hose/pipeline (16,18) at a distance above its lower suction end and produces a ejector/gas lift effect in the hose/pipeline (16,18), characterized in that the facility comprises a container (22) with sieve/sieve (24) for separating transported, contaminated, particulate mass, which container (22) has a hose -/tubular downwardly directed return flow (38) for contaminated transport medium (fluid), which return flow (38) with its lower end (40) in use position is inside the suction end of said hose/pipeline (16,18). 2. Plant according to claim 1, characterized by that the return pipe (38) which transports contaminated trans- \ — sports medium for recycling purposes, by its i mentioned in the outflow end (40) located at the suction end is provided with a nozzle for injecting return liquid with a directed jet effect. 3. Installation according to claim 2, characterized in that said nozzle consists of a nozzle with a built-in jet pump. 4. Installation according to one or more of the preceding claims, characterized in that an underwater listening device in the form of a hydrophone (44) is mounted to a lower part of said hose/pipeline (16,18) for audio monitoring of the mass suction process . 5. Plant according to one or more of the preceding claims, characterized in that the lower part of said mass-transport medium-up-transporting run in hose/pipeline design is a flexible, relatively long hose (16) which is connected at its upper end to a riser (18) which, especially at large depths/lift heights, up shows increasing diameter towards the uppermost outlet (20). 6. Plant according to one or more of the preceding claims, characterized in that a channel (32) leads between said container (22), which is designed with a closed top, and a compressor (30) for the delivery of compressed gas, for example air , a pipe or hose, for recirculation of compressed gas used in the gas lift. 7. Plant according to one or more of the preceding claims, characterized in that said nozzle/nozzle is located in a narrowing (42) in the lower end part of the suction hose (16). 8. Plant according to one or more of the preceding claims, characterized in that the nozzle/nozzle is eccentric and/or inclined in relation to the longitudinal axis of the suction hose end part (16). 9. Use of a contaminated transport medium, preferably a liquid transport medium, in a process for transporting contaminated, particulate mass of solid material located on the seabed (10), where contaminated transport fluid is recycled in an essentially closed circuit which is essentially oriented vertically.