WO2003102347A2

WO2003102347A2 - Procedure and apparatus for the extraction of methane gas from the sea bottom

Info

Publication number: WO2003102347A2
Application number: PCT/RO2003/000005
Authority: WO
Inventors: Petru Baciu
Original assignee: Petru Baciu
Priority date: 2002-06-03
Filing date: 2003-05-06
Publication date: 2003-12-11
Also published as: US20040244227A1; RO119637B1; WO2003102347A3; US20030214175A1

Abstract

The present invention is referring to a procedure and an apparatus of extraction of methane gas from the bottom of the sea. The procedure consists of lowering a take out enclosure to a depth of over 500 m., followed by a take out of a quantity of cryohydrate sediment from the bottom of the sea and the elevation of enclosure until is reached a level at which the water pressure and its temperature create conditions which allowed the beginning of a process of releasing of methane gas from cryohydrate crystals. The following operation is the releasing of methane from the entire quantity of take out cryohydrate, methane that is collected in a room from where is raised through a tube and captured into an enclosure and then liquefied. The remaining sediments without methane are returned to the ocean's floor by gravity.

Description

THE PROCEDURE AND THEAPPARATUS FORTHE EXTRACTION OFMETHANE GAS FROMTHE SEABOTTOM

The present invention is referring to a procedure and to an apparatus destined for the extraction of the methane gas from marine sediments found within the sea's and ocean's bottom and which in the end produces liquefied methane gas.

It is known that in aquatic medium, the animals and vegetal remains fall on the bottom and accumulate in a stratum. These organic sediments enter into a process of putrefaction, due to the presence of anaerobic microorganisms and produce methane gas. When this process takes place at depths of over

500 m, therefore at pressures of over 50 barr and temperatures below 3-7

°C, the methane is found in the stabile state, presents itself enclosed in the form of ice crystals known under the name of cryohydrate or gas hydrate.

The cryohydrate brought in the conditions of pressure lower than 47.2 barr and temperature greater than 7 °C will release methane gas.

The sediments found on the bottom of the oceans and seas can be presented themselves, depending of period of formation, in an emulsion, semisolid or even solid state.

It is also known the fact that the emission of methane gas from the bottom of the sea and oceans sediments makes the pollution of the Earth's atmosphere and that this process can not be hindered.

Are not known any extraction procedures of methane gas from marine sediments of cryohydrate like the present one. Are not known any extraction apparatus of methane gas from cryohydrate sediments from the oceans bottoms like the one shown by this invention.

The problem that the invention resolve is the set-up procedure and an apparatus to extract the methane gas from the sea bottom, by modification of the environmental conditions of cryohydrate.

The process of extracting methane gas from the sea's bottom according to the invention, in a first operation, consists of descent of a take out enclosure from the sea's surface up to over 500 m. deepness, followed by the take out of a certain quantity of cryohydrate sediments from the sea's bottom and the cryohydrate enclosure content lifted up to a level at which the water's pressure and temperature create conditions which allow the gazeification of the entire quantity of cryohydrate crystals in methane gas. The methane gas is collected, because of the difference of density, at the upper part of the enclosure and from where, after that is arising towards o f water's surface through a tube and is captured in an enclosure where then is liquefied and stored. The lifting of enclosure with cryohydrate is done to a level at which the water's pressure is less than 47.5 barr and its temperature is greater than 7 °C. The lifting of the enclosure stops at a level at which the process of gazeification can be started where the presence of methane gas pocket collected to the upper portion of enclosure is detected. The apparatus, according to the procedure, consists of a work platform, guiding arms set-up in crosswise and on which a work platform is sitting and from a central anchor, an cylindrical device which is connected at the superior ends of certain portions of mentioned arms, some collection cages being suspended by the guiding arms with the help of some ropes, while the central anchor by way of a rope being binded to the bottom of the sea. The work platform is square shaped and has in central portion a square opening. The platform is placed in area over _"the guiding arms. The platform is provided with some electrical trolleys, a cryogenic system for liquefaction and depositing of the methane gas and with an electrogenic Diesel group and a collector conduit connected to the cryogenic system along aside of square opening. The guiding arms are provided with a portion of horizontal part, which extends until the square-opening zone, continued by sloping portion, which exceeds in height the platform's surface. The guiding arms are set-up radial and symmetrically in relation with the central anchor and kept them at the sea's surface with the help of floating caissons. On the horizontal longerons and sloping portion of guiding arms slid from one end to the other blocks of guiding rolls on which the ropes are rolling up changing the radial position of the collection cages and to uphold the flexible conduits. The movement on circular direction of cages is being done with the help of electric driving propellers, which are located at the end of guiding arms, and which make the rning of entire ensemble. Under the central anchor is positioned a hoist with which is done the rope stretch until the guiding arms are submerged under the sea level, the inferior end of the mentioned rope being anchored with counterweights to the bottom of the sea. The mentioned cages consist of a parallelepiped room, which is continued at superior side with a pyramidal collector like a bell, and at the inferior side with some cylindrical sectors. The room's walls have in exterior some roles over which are passed some ends of the rope and then connected with some arms with counterweights connected with the semicylindrical sectors. The semicylindrical sectors are jointed to the cage's body and can be rotate at 90 degrees around a horizontal axis in such a way that, when they are open, they penetrate inside the cage's body. The collector bell has at the upper side a sleeve, which is a joint with the inferior ends of a flexible pipe. The collector, in its interior has a gas detector. By using the invention, two main achievements are accomplished:

- The use of these huge resources of energy which can reduce the effects of the energy crises.

- The diminution of the atmosphere ' s pollution.

Following is an example of the invention's making in connection with Fig. 1 to 10 which represent:

- Fig 1 lateral view of the apparatus for the extraction of the methane gas from the sea bottom, in conformity with the invention.

- Fig 2 view from above, from Fig. 1

- Fig. 3 lateral view, partial, of the apparatus for the methane gas extraction from the sea bottom, in conformity with the invention, at the time when the collecting cage is lifted above the sea level.

- Fig. 4 view from above, from Fig. 3

- Fig. 5 section with a plane 5-5 from Fig. 3

- Fig. 6 frontal view of the collecting cage, in conformity with the invention

- Fig. 7 view from above, from Fig. 6

- Fig. 8 laterally view 1-1 from Fig. 6

- Fig. 9 section with a plane II-II, from Fig. 6

- Fig. 10 schematic representation of the collecting cage, where by reaching the pressure and temperature conditions, takes place the process of releasing methane gas from cryohydrate.

The process of methane gas extraction from the sea bottom, in conformity with the invention, consists, in a first operation, in the descent of a taking of enclosure, from the sea surface until depths over 500 m, where the pressures are over 50 barr and the temperatures below 7 degrees Celsius and where the marine sediments of cryohydrate are found, followed by the second operation, period in which takes place the taking of a quantity of cryohydrate sediment from the sea's bottom.

The following operation consists in lifting the enclosure that contains the taking out of cryohydrate to the surface, until is reached a level where the pressure of water is below 47.5 barr, while temperature is greater than 7 degrees Celsius, condition which allows the beginning of the process of eliberating of methane gas from cryohydrate crystals. The halting of the cage's ascent to a level at which the eliberating process is possible to take place is ordered by the presence of methane gas pocket in the upper part of the cage, signaled by a detector. Once the halt is ordered, the cage's position is maintained until all quantity of taking out of cryohydrate is transformed in methane gas which, due to the difference in density, the methane gas is collected in the upper part of the enclosure and which then the methane is arising through a tube towards the water's surface.

In the entire, this time the methane gas released and conducted through a tube to the sea surface is captured in an enclosure of the sea's surface. In the next stage, takes place the liquefaction and collection of the methane gas.

The last stage in the process, conforming to the invention, involves the transfer of the liquefied methane gas to site to where it will be stored. The sediments separated from methane return to the ocean's floor by gravity. The extraction apparatus of methane gas from the bottom of the sea, conforming to the invention, consists of some arms for guiding B which are positioned crosswise and on which a platform A leans and from a central anchor C where the arms B are assembled.

The platform A is located at a sufficient height above sea's level so that the water's waves action do not impede the activity of working personnel and the operation of the equipment placed there. The platform has a square shape and is provided with a central opening also square. The platform A is rigidified with the help of some beams, pillars and diagonals but all these construction details are not showed being themselves known. The interior and exterior sides of platform A are surrounded with some balustrades 1 in order to protect the working personnel.

The arms B which are made from longerons and lattices, has each a horizontal portion b which extends to the opening zone a and is followed by a curved portion and then an inclined portion c that surpasses the platform's surface A. The upper ends of portion c are rigidly assembled with a cylindrical body 2 of the anchor C. The arms B are arranged radially and symmetrically related to the anchor C being maintained at sea level by some floating caissons 3 that are calculated so that they are able to take over the static and dynamic load of apparatus, the waves and wind, conforming to the invention.

On the longerons of arms B glide from one end to the other some blocks of guiding rolls 4 on which are rolling some ropes 5 and 6 with the purpose of vertical maneuvering of some collection cages D and the collection operations of marine cryohydrate sediments. The ropes 5 and 6 action is accomplished with the help of electrical trolleys 7 and 8 placed on A platform, in the upper B arms zone, where is all the technological equipment required for the extraction process and for working personnel. Cryogenic system for liquefaction and storage of methane gas 9 and an electrogen group Diesel 10 are also placed on platform A. Beside these, on platform A should be a control center room of the apparatus, conform to the invention, an electrical supplying system for all equipment and needs, an office, a bedroom, a buffet and a sanitary group.

In the vicinity of 7 and 8 trolleys on the platform A are also placed and some electrical trolleys 11 and 12 which by the help of 13 and 14 ropes and of some not shown devices allowed the modification of the radial position of cages D related of axis dd and the sustaining of flexible conduits 15 through which the methane gas released in cages D is risen to a collector conduit 16 connected to the above mentioned system 9.

The apparatus construction conforming to the invention was so draft that to permit the maneuvering of cages D in radial, vertical and horizontal directions, and the drawing out of cages from the water. Along the inclined portion c of arms B and in the zone of opening a of the platform A for the current cleaning and maintenance operation. And as well for the period when is requested the transportation of apparatus from one to other place, conforming to the invention.

In regards with cages D circular direction motion, meaning around axes dd, this movement is being done by some propellers 17 and 18 acted by electromotors, placed diametrical opposed, to the ends of arms B so that to create a rotating coupling for entire ensemble made by arms B and platform A and some propellers 19 and 20 placed at the other arms ends B so that to create break coupling which to allow to choose the desired position of the apparatus, conforming to the invention.

In order that the entire apparatus, conforming to the invention not to be taken away from the established place by the marine current, the sea's waves or by the winds, it is anchored by the sea's bottom through a rope 21 sized accordingly for the efforts at which is facing and connected to the inferior end with some counterweights 22 oversized for ensuring a good stability. By stretching the rope 21 with the help of a hoist 23 the apparatus arms B can be sunken below sea's level, achieving in this way the elimination of them displacement caused by the waves force.

When the position of the apparatus is moved in other location, conforming to the invention, can be recuperated the inferior portion of the rope 21 and counterweights 22, depending of the showed interest for these elements and their operation recuperation cost.

The D cages are composed from parallelipipedic body 24 continued at superior portion in a pyramid-shaped collection bell 25 and provided at the inferior portion with an axle with some springs e and with some cylindrical sector 26 and 27. The lateral walls of the body 24 are provided in exterior with some roll wills 28 and 29 over which are passing some ends of rope 5 and then tied to some arms with counterweight 30. Because of this construction by pulling the rope 5 the sectors 26 and 27 which are joined through bearings, springs e and shaft ff to the body 24 will rotate 90 degrees in opposite directions, around the horizontal shaft ff opening and closing in this way the entrance to the interior of body 24. In this situation the cages D are ready for operation.

The inferior halves of sector 26 and 27 are provided with some perforate sectors g whose orifices permit the separating of cryohydrate crystals from the sea's water.

The collection bell 25 is provided with a sleeve h in uppermost part to which the inferior end of flexible conduit 15 with rope 14 is joined. Above and on exterior ends of room 24 are provided rolls 31 for rolling rope's 5 ends. The flexible c onduits 15 a re submerged i n w ater w ith a large p ortion b ut partial is placed in air above the water surface until to the collection conduit 16. Because the conduits 15 are filled with water on their entire portion from cages D and up to the sea's surface, the pressure and temperature at which are submitted on both sides of their walls are equals at each section. It is very important that the ascent of the methane gas trough conduits 15 to be done without hydraulic resistance and without the possibility of forming of a hydraulic vane, which can impede the gas's ascent and can lead to the gas's dissipation.

The conduits 15 are tied, at their submerged portions, with some rings not shown, to the rope 14 through which, helped by trolleys 12 the conduits 15 will be maintained in a tension state.

For making the apparatus operational, conforming to the invention, the cryohydrate deposit is determined from the sea's level or from deepness by known methods, with the help of which the bottom of the sea profile and the eventually fauna and flora can be established.

In accordance to the cryohydrate deposit characteristics, the place and the action ray, where apparatus to be anchored is established, conforming to the invention. The exterior of arms B ends are bridled between them with the purpose of construction rigidness, by some ropes 32. The body 2 of the anchor C houses axial-radial pressure bearing 33, which permits the rotation of the entire installation around the vertical axis dd.

The cages D by the help of electrical trolleys 7 are launched towards sea bottom i at touching of cryohydrate deposit j their semicylindrical sectors 26 and 27 have to be open completely by maneuvering the electrical trolleys 8. When reaching of a certain depth in cryogenic deposit j the cages D advance ceases and with the help of springs e trolleys 8 and of arms 30 from ends of the rope 5 the closing of sectors 26 and 27 is done, operation which leads to the taking out a quantity of cryohydrate from deposit j.

The cages D loaded with cryohydrate are lifted to the surface using trolleys

7.

The ascent of cages D continues until is reached a level were the pressure of water becomes to be less than in the cryogenic deposit pressure, and the temperature surpasses 7 degrees Celsius, ensuring the gradual release of methane gas from collected cryohydrate. A gas detector 34 is provided in the superior portion of bell 25, which at methane gas detection signals halting of cage D.

The gas that is formed, having a lower density than the water rises and is collected under the bell 25 and further is risen trough conduit 15 towards the cryogenic system 9. After the entire quantity of the cryohydrate collected in cages D release the methane gas, the opening of sectors 26 and 27 is signaled, the remaining sediments without methane are returned to the ocean's floor. The descent of cages D into the sediment deposit is started again. In this way the collection cycle is repeated until the depletion of the entire deposit in the area where the apparatus conforming to the invention was placed.

The position of cages D towards axis dd can be modified in a radial direction with the help of trolleys 11 and on its circumference using propellers 17, 18, 19 and 20, to assure coverage of the entire deposit area.

Claims

1. Procedure of extraction of methane gas of the sea bottom, characterized by so that: in a first operation, consists of lowering of a take out enclosure to the depths of over 500 m. from the sea surface, followed by taking out a quantity of cryohydrate sediment of the bottom of the sea and lifting of the enclosure which contain the cryohydrate until reaching of a level at which the water pressure and its temperature created conditions which permit the beginning of process of releasing methane gas from cryohydrate crystals, the following operation being the releasing of entire quantity of methane gas from cryohydrate, by keeping at this level the enclosure. The methane gas being collected because difference of density between water and gas at upper side of enclosure and which then the methane is risen towards water surface trough a tube and is captured in a cryogenic system, while then liquefied and stored. The remaining sediments without methane are returned to the ocean's floor by gravity.

2. Procedure of the extraction of methane gas of the sea bottom according c laim 1 , characterized by so that, the lifting of enclosure with cryohydrate is done until reaching a level at which the pressure of water is less then 47.5 barr and its temperature is more than 7 degrees Celsius.

3. Procedure of the extraction of methane gas of the sea bottom, according claim 1, characterized by so that, the halting of enclosure's ascent at a level at which the methane's release process can take place is ordered by the signal of presence of a pocket of methane gas collected at the upper part of the enclosure.

4. Apparatus of the extraction of methane gas of the sea bottom characterized by so that, is composed from some guiding arms B, positioned in crosswise and on which a platform A is sitting and from a central anchor C at which cylindrical corp 2 are assembled through superior ends of c portions the mentioned arms B, some cages D being suspended on arms B with the help of ropes 5 , 6 , 13 a nd 14 while anchor C being connected through a rope 21 to the sea bottom.

5. An apparatus of the extraction of methane gas of the sea bottom, according claim 4, characterized by so that, the work platform A is of a square shape and has in the central part an opening a also square, on it being placed some electrical trolleys 7, 8, 11 and 12, positioned in the zones of over the arms B, and is provided with a cryogenic system for liquefaction and depositing of the methane gas 9 and with a group electrogen Diesel 10 and along with the sides of opening a collection conduit 16 connected to the cryogenic system 9.

6. An apparatus of the extraction of methane gas of the sea bottom, according claim 4, characterized by so that, the guiding arms B being provided with a portion b horizontally which extends until the opening zone a followed by a inclined portion c which exceed in high the platform A surface, their disposition being radial and symmetric towards the anchor C while their supporting to the sea surface being achieved by the help of floating caissons 3.

7. An apparatus of the extraction of methane gas of the sea bottom, according claim 6, characterized by so that, on the longerons of portions b and c of arms B guide from one end to the other some rolls blocks 4 on which rolling the ropes 5 and 6 and which permit the modification of the radial position of cages D and the support of flexible conduits 15 with the help of ropes 13 and respective 14, the circular movement of cages D is achieved by the help of some propellers 17, 18, 19 and 20 which are electrical powered and placed at the ends of arms B and which allow the rotation of entire ensemble. •

8. An apparatus of the extraction of methane gas of the sea bottom, according claim 4, characterized by so that, under the central anchor C is positioned a hoist 23 with which is making the stretching of rope 21 until can be reached the submerged under sea level of arms B. The inferior end of mentioned rope 21 being anchored by some counterweights 22.

9. An apparatus of the extraction of methane gas of the sea bottom, according claim 4, characterized by so that, the mentioned cages D are provided a collected room 24 parallelepiped, continued at superior part with a collecting bell 25 of pyramidal shape and at the inferior part with some cylindrical sectors 26 and 27, the exterior walls of room 24 being equipped with some rolls wills 28 and 29 over which are passing some ends of rope 5 and then tied by some arms 30 connected with sectors 26 and 27.

10. An apparatus of the extraction of methane gas of the sea bottom, according claim 9, characterized by so that, the cylindrical sectors 26 and 27 are joined to room 24 and can be rotated with the help of some springs e and ropes 5 at 90 degrees around of a horizontal axis, so that when they are opened penetrate inside of room 24 and are provided at the inferior half with some portions perforated g.

11. An apparatus of extraction of methane gas of the sea bottom, according claim 9, characterized by so that, the c ollected bell 25 i s equipped at upper part with a sleeve h at which is connected the inferior end of conduit 15 and at interior with a gas detector 34.