Patent Grant
8308518
The present embodiments generally relate to a method for processing and moving liquefied natural gas.
A need exists for a method using a soft yoke configured to provide a means for offshore transfer of liquefied natural gas that can maintain a stable distance between a floating structure or vessel and a transport vessel, such as a ship.
A need exists for a method using a soft yoke configured to dynamically react to environmental conditions, such as wind and waves, to extend and retract a jib to maintain a stable distance between the floating structure and the ship.
A further need exists for a method using a soft yoke with a quick release configured to release ships from the soft yoke when the jib has extended to a maximum extension or retracted to a minimum retraction, and to cease flow of fluid between the floating structure and the ship for safety.
The present embodiments meet these needs.
The detailed description will be better understood in conjunction with the accompanying drawings as follows:
The present embodiments are detailed below with reference to the listed Figures.
Before explaining the present method in detail, it is to be understood that the method is not limited to the particular embodiments and that it can be practiced or carried out in various ways.
The present embodiments generally relate to a method for processing and moving liquefied natural gas.
The method can be used in water, such as in water at a depth of about 200 feet or deeper. The method can be movable and/or relocatable. The method can be designed to be implement ted in open sea conditions.
The method can include receiving dry natural gas, such as from a pretreatment source. The method can include cryogenically cooling the dry gas, forming a liquefied natural gas, such as by using a station heat exchanger with a liquefaction train.
The method can include flowing the liquefied natural gas to a moveable floating transport vessel using offload flexible conduits on a floating station and/or a soft yoke.
The method can include adjusting a distance between the floating station and the floating vessel to accommodate station motion, transport vessel motion, wave motion, current motion, wind motion, changes in draft, or other motions without disengaging. For example, the adjusting can be performed using mooring arms of a soft yoke that maintain a nominal distance between the floating station and the transport vessel.
The method can include forming an enclosed gangway to allow for the transport of personnel, equipment, and the like between the floating station and the transport vessel. The enclosed gangway can be formed using a jib and a boom of the soft yoke.
The method can include monitoring offloading of liquefied natural gas from the floating structure to the transport vessel, and return of a hydrocarbon vapor from the transport vessel to the floating structure.
The method can include providing quick connect/disconnect engagements between the softy yoke and the transport vessel.
The method can include storing the liquefied natural gas on the transport vessel at a cryogenic temperature, and recycling hydrocarbon vapor formed during offloading of the liquefied natural gas to the floating station using an adjustable vapor return flexible conduit.
The method can include maintaining a cryogenic temperature using a flow rate substantially the same as the floating station rate of fuel use, and then releasing the transport vessel from the floating station. The method can include transporting the liquefied natural gas to another location using the transport vessel.
The method can include receiving pretreated dry gas from a pretreatment source through an inlet conduit, which can pass through a spread moored turret that engages a sea bed. For example, the method can include receiving 200 million standard cubic feet per day of dry gas through the dry gas inlet conduit from the pretreatment source. The dry gas can primarily be methane with small amounts of ethane. Other contaminates can be reduced to low levels consistent with typical liquefied natural gas processing.
The method can include the step of cooling the dry gas to a cryogenic temperature such as in a cold box or other type of heat exchanger. The dry gas can be cooled to a low temperature, such as to a temperature of −262 degrees Fahrenheit. The method can include flowing the cooled dry gas through a liquefaction train, forming liquefied natural gas.
The method can include flowing the liquefied natural gas through across a soft yoke, such as through yoke offload flexible conduits on the soft yoke.
The soft yoke can be used to flexibly and moveably connect a transport vessel to the floating liquefied natural gas processing station using at least two telescoping mooring arms. The telescoping mooring arms can have a boom and jib in a nested configuration, allowing the telescoping mooring arms to slide in and out as the transport vessel and the floating liquefied natural gas processing station both pitch, yaw, roll, surge, sway, and heave.
The soft yoke can be used to flexibly transfer the liquefied natural gas from the floating liquefied natural gas processing station to the transport vessel, and to transfer formed hydrocarbon vapor from the transport vessel. The hydrocarbon vapor can be formed during offloading of the liquefied natural gas onto the transport vessel. The hydrocarbon vapor can be transferred back to the floating liquefied natural gas processing station for reprocessing, and/or for use as fuel to operate one or more portions of the floating liquefied natural gas processing station. The hydrocarbon vapor can be recycled through the station heat exchanger, such as a cold box.
While performing other functions, the softy yoke can simultaneous safely transport people and equipment between the floating liquefied natural gas processing station and the transport vessel, such as in open sea during calm weather, and during gale and 100 year storm conditions. The soft yoke can thereby allow for the transfer of people and equipment without people or equipment falling into the sea.
The soft yoke can also function to fold away the telescoping mooring arms, such that the floating liquefied natural gas processing station can be towed or moved without the telescoping mooring arms projecting outward. As such, the soft yoke can be safely maneuvered under or between bridges.
The method can include storing the liquefied natural gas in liquefied natural gas storage tanks on a transport vessel and then moving the liquefied natural gas to another location.
The method can include recycling hydrocarbon vapor from the liquefied natural gas storage tanks to the floating liquefied natural gas processing station using the at least two telescoping mooring arms. Vapor return can be performed at the same rate as the flow rate of the liquefied natural gas.
The liquefied natural gas processing station can use the hydrocarbon vapor as a fuel to run on-board turbines.
Once loading the liquefied natural gas into the transport vessel is complete, and the hydrocarbon vapor is transferred, the method can include releasing the transport vessel from the floating liquefied natural gas processing station to transport the liquefied natural gas to another location. The releasing can include use of three connectors, including a primary quick connect/disconnect connector, a secondary emergency disconnect connector, and a tertiary disconnect connector.
The method can include powering the floating liquefied natural gas processing station with the recycled hydrocarbon vapor created during offloading, such as by using it as fuel in steam generators.
The method can include pressurizing cylinders of the soft yoke using an accumulator in order to continuously and systematically centralize the boom with the jib of the soft yoke. Centralizing cylinders can be used to centralize the boom with the jib, and can have a capacity ranging from about 200 psi to about 2000 psi, or any psi depending upon the application.
The dimensions of the jib can include a length from about 50 feet to about 100 feet, and a width from about 7 feet to about 14 feet.
The method can include cooling of the dry gas to a cryogenic temperature, such as by using a dual expansion nitrogen cycle assembly, another liquefied natural gas liquefication assembly, a single mixed refrigerant, a dual mixed refrigerant, or a cascade refrigerant.
The method can include allowing the floating liquefied natural gas processing station to weather vane according to weather conditions, direction of wind, and direction of waves around a spread moored turret that swivels.
In operation, once the transport vessel is connected to the floating natural gas processing station, the yoke offload flexible conduits can be engaged in fluid communication with one or more storage tanks on the transport vessel, and the fluid, such as the liquefied natural gas, can be pumped from the floating natural gas processing station to the storage tanks.
As such, the soft yoke can be used to connect transport vessel to floating natural gas processing stations, to flow fluid from the floating natural gas processing station to the transport vessel, and then the transport vessels can be used to transport to the fluid to another location.
Each soft yoke mooring arm can have a yoke vapor return flexible conduit for communicating vapor formed during offloading of the fluid back to the floating natural gas processing station for use in running the liquefaction train or other station power plants.
For example, during the flowing of the fluid to the storage tank, certain fluids, such as liquefied natural gas, can form a vapor. The yoke vapor return flexible conduit can receive the formed vapor and flow the formed vapor from the transport vessel to the floating natural gas processing station for reprocessing the vapor or use as a fuel. The formed vapor can be reprocessed, such as with the station heat exchanger, and can flow back through the yoke offload flexible conduit to the transport vessel.
Each telescoping mooring arm can form an enclosed gangway with openings. The enclosed gangway can support movement of personnel and equipment up to 800 pounds at least, between the transport vessel and the floating natural gas processing station.
The telescoping mooring arms can each have a length from about 50 feet to about 150 feet, and a width from about 7 feet to about 14 feet. However, the size of the telescoping mooring arms can be different depending upon the particular application. In one or more embodiments, a stiffness of the telescoping mooring arms can operate within a range from about 2.5 tons per foot to about 10 tons per foot.
The soft yoke can extend up to any length required to maintain a predefined distance between the transport vessel and the floating natural gas processing station, for example from +/−5 feet to +/−30 feet.
The soft yoke can have or use a controller and dynamic positioning to control the distance between the floating natural gas processing station and the transport vessel, and/or a location of the transport vessel relative to a preset longitude and latitude.
Turning now to the Figures, the method can be better understood with regard to the equipment it can be used upon.
Referring now to both
The upper connecting mount 72 and the lower connecting mount 74 can have a diameter from about 48 inches to about 84 inches, and can be made of powder coated steel.
The first telescoping soft yoke mooring arm 68 can be actuated by a soft yoke controller 89, which can be in communication with a station controller (shown in
The soft yoke 66 can include a turn table 76 connected to the lower connecting mount 74. The dimensions of the turn table 76 can be from about 9 feet to about 12 feet in diameter. The turn table 76 can have a thickness from about 12 inches to about 24 inches, and can be made of steel with an internal bearing of bronze or another frictionless material.
The soft yoke 66 can include a king post 78 that engages with the turn table 76, the upper connecting mount 72, and the lower connecting mount 74. The turn table 76 can be configured to rotate with the king post 78. The king post 78 can be connected to a first tensioner 90 and a second tensioner 91 by a tensioner mount 93b.
The king post 78 can be made of steel, and can have a length of from about 12 feet to about 50 feet and a diameter from about 3 feet to about 6 feet. The king post 78 can be a rolled tube with a hollow portion.
The soft yoke 66 can have a boom 80 connected to the turn table 76. The boom 80 can have a length from about 40 feet to about 140 feet, a height from about 8 feet to about 14 feet, and a width from about 8 feet to about 16 feet.
In embodiments, the boom 80 can be a tubular. The boom 80 can have a diameter from about 14 feet to about 16 feet. The boom 80 can include hollow tubulars welded together to reduce cost in shipping. The boom 80 can be configured to not fail upon impacts and slams, which can occur to the floating natural gas processing station to which the boom 80 is attached. For example, the boom 80 can be configured to not fail upon impacts and slams during a 20 year storm, according the US Coast Guard classification of a 20 year storm with wave sizes of up to 12 feet and a frequency of from about 2 feet to about 3 feet.
A heel pin 106 can connect the boom 80 to the turn table 76, allowing the boom 80 to rotate relative to the turn table 76. A typical heel pin can be machined from cold drawn high strength steel shafting, and can have a length from about 6 inches to about 18 inches and a diameter from about 6 inches to about 12 inches. The boom 80 can be locked into the turn table 76 using a collet and locking pin.
As such, the boom 80 can pivot from a first position, such as with the boom 80 extending to a substantially parallel position with the king post 78 (which is shown in
The first luffing wire 82 and the second luffing wire 84 can each connect to the boom 80 at one end and to the king post 78 at the opposite end. The first luffing wire 82 can engage a first turn down sheave 86 mounted to the king post 78. The second luffing wire 84 can engage a second turn down sheave 88 mounted to the king post 78. The first and second turn down sheaves 86 and 88 can be mounted to the king post 78 with a sheave mount 93a.
The first luffing wire 82 can extend from the first turn down sheave 86 to the first tensioner 90, which can function to apply and release tension to the first luffing wire 82. The amount of tension applied to the first luffing wire 82 can be an amount sufficient to hold the first telescoping soft yoke mooring arm 68 or greater. The second luffing wire 84 can extend from the second turn down sheave 88 to the second tensioner 91, which can function to apply and release tension to the second luffing wire 84. The amount of tension applied to the second luffing wire 84 can be an amount sufficient to hold the first telescoping soft yoke mooring arm 68 or greater.
For example, in operation the first and second tensioners 90 and 91 can be used to apply tension to the first and second luffing wires 82 and 84, allowing the boom 80 to be raised towards the first position with an upward movement away from any deck of a transport vessel. When the first and second tensioners 90 and 91 release tension from the first and second luffing wires 82 and 84, the boom 80 can be lowered towards the second position with a downward movement towards a surface of the sea and towards a deck of a transport vessel.
A jib 92 can be nested within the boom 80, allowing the jib 92 to have an extended position and a retracted position, and enabling the jib 92 to be telescopically contained within the boom 80. The jib 92 can be a tubular. The jib 92 can have a diameter ranging from about 12 feet to about 14 feet. The tubulars of the jib 92 can be made of hollow tubular steel.
The jib 92 can be controlled by at least one centralizing cylinder, such as a first centralizing cylinder 94 and a second centralizing cylinder 95.
The first and second centralizing cylinders 94 and 95 can control a position of the jib 92 within the boom 80. For example, the first and second centralizing cylinders 94 and 95 can be mounted in parallel on the opposite sides of the boom 80 to extend and retract the jib 92 within the boom 80.
The soft yoke 66 can connect between a floating gas processing station or the like and a transport vessel or the like. As such, the soft yoke 66 can be used to accommodate for environmental factors that can shift a position of the transport vessel, the floating natural gas processing station, the soft yoke 66, the like, or combinations thereof, to allow for continuous loading of liquefied natural gas, and to allow for safe transfer of people and equipment over a gangway formed using the soft yoke 66. The soft yoke 66 can provide for higher levels of safety by maintaining safe distances using computer controlled devices between the transport vessel and the floating natural gas processing station and the like, and by providing for quick connects and emergency disconnects in case of fire, high winds, or rogue waves. The environmental factors can include wave motions, current motions, wind, transport vessel dynamics or the like, floating natural gas processing station dynamics or the like, changes in draft, and other such external and internal variables.
The first and second centralizing cylinders 94 and 95 can each be hydraulic or pneumatic cylinders, or combinations thereof, and can be connected to one or more accumulators 104a, 104b, 104c, and 104d. Any number of accumulators can be used.
The first and second centralizing cylinders 94 and 95 can extend and retract the jib 92 to maintain the transport vessel or the like at a nominal standoff position within preset limits from the floating natural gas processing station or the like.
The soft yoke 66 can prevent disconnection of any conduits communicating between the floating natural gas processing station and the transport vessel or the like, by maintaining the correct spacing therebetween.
Preset distances or limits from the floating natural gas processing station or the like can be any distance required for the particular application. The preset limits can be any allowable range of variation from the predefined distance required for the particular application. For example, in an application with a nominal distance of one hundred feet, and a preset limit of plus or minus ten feet, the first and second centralizing cylinders 94 and 95 can operate to extend and retract the jib 92 to maintain the nominal standoff position from about ninety feet to about one hundred ten feet. The nominal standoff position can be a length of the boom 80 plus a length of the jib 92 extending from the boom 80.
The soft yoke 66 can include conduits for flowing fluid between floating natural gas processing stations and transport vessels or the like. For example, the soft yoke 66 can include a yoke offload flexible conduit 98 and a yoke vapor return flexible conduit 99. The yoke offload flexible conduit 98 can be used to flow fluid, such as liquefied natural gas, from the floating natural gas processing stations to waiting transport vessels or the like. The fluid can be a liquefied natural gas or another liquid.
The yoke offload flexible conduit 98 can flow the fluid from the floating natural gas processing station into storage tanks on the transport vessel. The transport vessel can receive, store, transport, and offload the fluid.
The yoke vapor return conduit 99 can flow hydrocarbon vapor formed during offloading of the fluid back from the transport vessel to the floating natural gas processing station. For example, the yoke vapor return flexible conduit 99 can be in fluid communication with a station heat exchanger (shown in
The yoke offload flexible conduit 98 and the yoke vapor return conduit 99 can each be made from about eight inch to about ten inch diameter rigid pipe, or from a similar diameter flexible composite cryogenic hose, or combinations thereof. The yoke offload flexible conduit 98 and the yoke vapor return conduit 99 can be any size or material as required for the particular application, given particular flow rates, pressures, and storm conditions. For example, the yoke offload flexible conduit 98 and the yoke vapor return conduit 99 can be 3 inch or larger diameter reinforced hose, a draped hose, or a festooned hose.
The yoke offload flexible conduit 98 can have a jib flexible portion 109a, and the yoke vapor return flexible conduit 99 can have a jib flexible portion 109b. The jib flexible portions 109a and 109b can allow the yoke offload flexible conduit 98 and the yoke vapor return conduit 99 to move easily along with the boom 80 as the jib 92 expands and retracts within the boom 80. Since the boom 80 can be raised and lowered using the first and second tensioners 90 and 91, the jib flexible portions 109a and 109b can enable the yoke offload flexible conduit 98 and the yoke vapor return conduit 99 to have enough range of motion and flexibility to move with the boom 80 without fracturing or being over tensioned.
The yoke offload flexible conduit 98 can have a first rigid portion 110a, and the yoke vapor return flexible conduit 99 can have a second rigid portion 110b. The rigid portions 110a and 110b can provide a rigid connection between the yoke offload flexible conduit 98, the yoke vapor return conduit 99, and the boom 80, allowing the boom 80 to securely move the yoke offload flexible conduit 98 and the yoke vapor return conduit 99 as the boom 80 moves.
The yoke offload flexible conduit 98 and the yoke vapor return flexible conduit 99 can be secured to the boom 80, such as by gussets 105a and 105b, and support structures 114a, 114b, and 114c. Each support structure 114a, 114b, and 114 and gusset 105a and 105b can be pivotable and/or rotatable.
The soft yoke 66 can include one or more low pressure fluid accumulators 113a, 113b, 113c, and 113d for the first and second centralizing cylinders 94 and 95. The one or more low pressure accumulators 113a, 113b, 113c, and 113d can have a pressure from about 30 psi to about 300 psi each.
The soft yoke 66 can include a connection interface 103 for connecting the soft yoke 66 to the transport vessel or the like. For example, the connection interface 103 can be a primary quick connect/disconnect connector with a secondary emergency disconnect connector and a tertiary disconnect connector that engages a mooring socket on a transport vessel.
The soft yoke 66 can include a stop 404 configured to selectively engage a hydraulic actuator switch 404. For example, the stop 404 can be located on the boom 80, and the hydraulic actuator switch 403 can be located on the jib 92.
The secure enclosed gangway 100 can have openings 102a, 102b, and 102c, which can provide ventilation and allow spray and wind to pass through the secure enclosed gangway 100 without pulling a person into the sea.
The secure enclosed gangway 100 can function to allow for personnel to move between transport vessel and floating natural gas processing stations when the soft yoke 66 is connected therebetween. The secure enclosed gangway 100 can be made of aluminum, steel, or another material. The secure enclosed gangway 100 can have an anti-slip tread, handrails, lighting, and other safety features.
The jib 92 is depicted in a partially extended position relative to the boom 80 with the jib flexible portion 109a slightly tensioned as it connects to the rigid portion 110a. The rigid portion 110a is shown connected to the boom flexible portion 112a.
The boom flexible portion 112a can allow the conduits of the soft yoke 66 to move extend and retract along with the jib 92. For example, when the jib 92 is extended and retracted using the centralizing cylinders, the boom flexible portion 112a can provide the conduits with enough range of motion and flexibility to extend and retract with the jib 92 without fracturing or being over tensioned.
The jib flexible portion 109a is configured to have a length sufficient to have enough range of motion and flexibility to extend and retract along with the jib 92. The boom flexible portion can be configured the same as the jib flexible portion 109a, and can function in the same manner.
In one or more embodiments, the first and second telescoping soft yoke mooring arms 68 and 70 can connect directly to the stern 16 of the transport vessel 12, with the first and second telescoping soft yoke mooring arms 68 and 70 both angled inwards towards the stern 16. First and second mooring sockets 18 and 20 can connect the first and second telescoping soft yoke mooring arms 68 and 70 to stern 16.
A station heat exchanger 53 can be connected to a pretreatment source 50 for receiving dry gas 48 from the pretreatment source 50.
The pretreatment source 50 can have a pretreatment dehydrator 51 and a pretreatment heat exchanger 52. Accordingly, the pretreatment source 50 can be configured to cool and dry natural gas from a wellbore or other source.
The liquefied natural gas 54 can flow from station offload flexible conduits, which are also termed “offload flexible conduits” herein, through the yoke offload conduits to liquefied natural gas storage tanks 22, 23, 25, and 26 on the transport vessel 12.
A hydrocarbon vapor 101 can flow from the transport vessel 12, through yoke vapor return flexible conduits, through station vapor return flexible conduits, and to the station heat exchanger 53.
A station controller 43 can be located on the floating natural gas processing station 40 to control one or more components thereof. The floating natural gas processing station 40 can include one or more liquefaction trains 57 in communication with the station heat exchanger 53.
The station controller 43 can control flow of liquefied natural gas 54, hydrocarbon vapor 101, and can control the station heat exchanger 53.
The transport vessel 12 can be positioned at a nominal standoff position 97 relative to the floating natural gas processing station 40. In one or more embodiments, the first and second telescoping soft yoke mooring arms 68 and 70 can be connected directly to the transport vessel 12 or to the docking bar 116, allowing versatility of connection for vessels with small narrow sterns, and for vessels with larger, wider sterns.
The pretreatment source 50 can communicate with the station heat exchanger 53 via inlet conduit 46, allowing dry gas 48 to flow to the station heat exchanger 53 after passing through the pretreatment heat exchanger 52 and the pretreatment dehydrator 51.
The liquefied natural gas 54 can flow from the floating natural gas processing station 40, through an offload flexible conduit 56 and through corresponding yoke offload flexible conduits on the soft yoke 66 to the transport vessel 12.
The hydrocarbon vapor 101 can return from the transport vessel 12 through yoke vapor return flexible conduits on the soft yoke and through a corresponding vapor return flexible conduit 65 on the floating natural gas processing station 40.
The liquefaction trains 57a and 57b can functions to cool the station heat exchanger 53. The liquefied natural gas 54 and the hydrocarbon vapor 101 can flow through the liquification trains 57a and 57b between the transport vessel 12 and the station heat exchanger 53.
The primary quick connect/disconnect connector 58 can engage a mooring socket on the transport vessel. Hydraulic cylinders can force the quick connect/disconnect connector 58 into the mooring socket.
The secondary emergency disconnect connector 59 can be operatively engaged with an emergency actuator 406, which can be operatively engaged with a hydraulic actuator switch 403. The first lock release 408 can have a pin recess 414 for operatively engaging the emergency actuator 406. Quick release bearings 410 can be disposed between the first lock release 408 and a locking recess sleeve 412.
In operation, the secondary emergency disconnect connector 59 can connect the soft yoke to the transport vessel. A stop can be configured to engage the hydraulic actuator switch 403 when the jib has reached a maximum extension length relative to the boom. The hydraulic actuator switch 403 can be configured to flow hydraulic fluid to the hydraulic actuator 406 upon engagement with the stop. The hydraulic actuator 406 can receive the flowing fluid from the hydraulic actuator switch 403. The hydraulic actuator 406 can push the first lock release 408 upon receipt of the fluid from the hydraulic actuator switch 403.
The first lock release 408 can then disengage the quick release bearings 410 and release the telescoping soft yoke mooring arms from the transport vessel. The quick release bearings 410 move from being engaged within a locking recess sleeve 412 to within a pin recess 414, thereby releasing the soft yoke from the transport vessel.
A dry gas inlet conduit 46 can extend into the spread moored turret 45 for communicating dry gas 48 from a pretreatment source for processing on the floating natural gas processing station 40 with a natural gas liquefaction train 57.
The spread moored turret 45 allows the floating natural gas processing station 40 to weather vane according to weather conditions, wind direction, and waves. For example, the spread moored turret 45 allows the floating natural gas processing station 40 to pivot and/or rotate about the spread moored turret 45, while the spread moored turret 45 is fixed by the mooring lines 44a and 44b.
The floating natural gas processing station 40 can be a ballasted floating vessel with a station hull 41 with a station variable draft.
In embodiments, the floating natural gas processing station 40 can use heading controls 49 connected to thrusters 55, allowing the floating natural gas production station 40 to dynamically maintain position with the transport vessel 12 using GPS positioning with other dynamic positioning equipment to maintain space between the floating natural gas processing station 40 and the transport vessel 12.
A vessel controller 43 can be connected to the heading controls 49 and the station thrusters 55.
The stern 16 of the transport vessel 12 can connect directly to the boom of the soft yoke 66. For example, a first mooring socket 18 can connect to the soft yoke 66. Pivot can be employed with the soft yoke 66 to rotate the mooring arms of the soft yoke 66, allowing the liquefied natural gas 54a, 54b, 54c, and 54d to flow into the storage tanks 22, 23, 25, and 26 from the natural gas liquefaction train 57 and/or the station heat exchanger 53.
The transport vessel 12 is shown having a hull 14 with a variable draft 17, allowing the transport vessel 12 to change draft and balance with respect to sea level 39 to be capable of receiving and offloading the processed liquefied natural gas 54a-54d.
The transport vessel 12 can have a bow 15 opposite the stern 16, with the storage tanks 22, 23, 24, 25, and 26 located on the hull 14. The storage tanks 22, 23, 24, 25 and 26 can be independent of each other.
The transport vessel 12 can include a vessel controller 30 with a processor and data storage for monitoring data associated with the receipt of the processed liquefied natural gas 54a-54d, the storage of the processed liquefied natural gas 54a-54d, and the offloading the processed liquefied natural gas 54a-54d from the transport vessel 12.
The transport vessel 12 can include a propulsion system 32 for moving the transport vessel 12 and a navigation system 34 for controlling the propulsion system 32.
The transport vessel 12 can have a station keeping device 38 that operates dynamic positioning thrusters 37. The station keeping device 38 and the navigation system 34 can communicate with a network 33, shown here as a satellite network, for dynamic positioning of the floating vessel 12. Client devices 416 with computer instructions can communicate with the network 33, allowing a remote user 1000 to monitor the processing, storage, and offloading.
The floating natural gas processing station 10 can have a station variable draft and can be ballasted like the transport vessel 12.
The data storage 35 can have computer instructions 150 to monitor various offloading and other data including: LNG loading rate, vessel draft, LNG temperature, cargo tonnage, vessel trim, and vessel motions including pitch, yaw, roll, surge, sway, and heave.
The data storage 35 can have computer instructions 151 to compare real-time monitored data to stored data in a data storage associated with the vessel controller processor and initiate alarms if loading rates, pressures, or temperatures exceed or fall below predefined limits for a certain transport vessel, a certain set of storage tanks, or a certain weather condition.
Step 500 can include receiving pretreated dry gas from a pretreatment source.
The dry gas can be received at a rate of at least 200 million standard cubic feet per day. The pretreated dry gas can be primarily methane with small amounts of ethane.
Step 502 can include cooling the dry gas to a cryogenic temperature, forming cooled dry gas.
The dry gas can be cooled to a temperature no warmer than −262 degrees Fahrenheit.
Step 504 can include passing the cooled dry gas through a liquefaction train, forming liquefied natural gas.
Step 506 can include flowing the liquefied natural gas from the floating ballasted station to the moveable floating transport vessel using a soft yoke.
Step 507 can include adjusting offload flexible conduits to accommodate floating station motion, transport vessel motion, wave motion, current motion, other weather motion without disengaging.
Step 508 can include maintaining a nominal distance between the moveable floating transport vessel and the floating ballasted station dynamically using a pivotable telescoping mooring arm having a jib nested within a pivotable boom accommodating for: floating ballasted station motion, moveable floating transport vessel motion, wave motion, current motion, and other weather motion without disengaging or leaking
Step 509 can include providing slack to luffing wires that engage between the jib and tensioners.
Step 510 can include forming a telescoping and dynamically moving enclosed gangway to safely transport personnel and gear between the floating vessel.
The safely personnel and gear can move between the moveable floating transport vessel and the floating ballasted station using the enclosed gangway formed by the jib and the boom.
Step 512 can include monitoring offloading and return of hydrocarbon vapor from the transport vessel during offloading of the liquefied natural gas.
The monitoring can be continuous, and can include monitoring return of a hydrocarbon vapor from the moveable floating transport vessel to the floating ballasted station, such as by using a yoke controller in communication with a vessel controller and a floating ballasted station controller.
Step 514 can include accommodating transport vessels with a variety of stern configurations for offloading.
Step 516 can include providing for quick connect/disconnect engagements and at least one emergency disconnect engagement to the transport vessel for fast connect and fast disengagement in case of storms, a rogue wave, or a fire.
At least two connectors can be used to quick connect and emergency disengage from the moveable floating transport vessel motion to the floating ballasted station.
Step 518 can include storing the liquefied natural gas in liquefied natural gas storage tanks on the transport vessel at a cryogenic temperature of colder than −262 degrees Fahrenheit.
Step 520 can include recycling hydrocarbon vapor formed during offloading onto the transport vessel to the floating liquefied natural gas processing station using vapor return flexible conduits and maintaining a cryogenic temperature using a flow rate substantially the same as the rate at which the floating vessel uses fuel.
Step 522 can include releasing the transport vessel from the floating ballasted station to transport the liquefied natural gas to another location.
Step 523 can include using the hydrocarbon vapor to power the transport vessel and/or the floating ballasted station.
Step 524 can include using an accumulator to manage pressure in a cylinder used to control the engagement between the jib and the boom for maintaining a distance between the transport vessel and the floating ballasted station at a preset distance.
Step 536 can include using at least one luffing wire attached to at least one sheave and at least one hydraulic cylinder to raise and lower the boom as it pivots while secured to a turntable, enabling compact storage of the pivotable telescoping mooring arm.
Step 540 involves using a spread moored turret with the floating ballasted station, and flowing the dry gas into the floating ballasted station, thereby allowing the floating ballasted station to weather vane according to weather conditions, direction of wind, and direction of waves around the spread moored turret.
Step 542 involves using modified equipment on the station that provides a docking notch formed into the floating station to surround the bow of the transport vessel and at least one of the telescoping mooring arms to a port side or a starboard side of a hull of the transport vessel.
Step 544a involves using at least two telescoping mooring arms to engage mooring sockets in a stern the transport vessel to directly connect the stern to the floating ballasted station.
Step 544b can include connecting a docking bar to a stern of the transport vessel, and then engaging at least two telescoping mooring arms to the docking bar to maintain the transport vessel at a nominal distance from the floating ballasted station.
Step 544b can be an alternative to Step 544a. The docking bar can be secured to a stern of the transport vessel, then the two telescoping mooring arms can engage the docking bar to maintain the transport vessel at a nominal distance from the floating ballasted station.
Step 546 can include using three connectors to quickly connect and disconnect the floating ballasted station from the transport vessel.
The three connectors can include a primary quick connect/disconnect connector, a secondary emergency disconnect connector, and a tertiary emergency disconnect connector used simultaneously by the floating ballasted station to engage or release the transport vessel.
Step 548 involves using hydraulic centralizers to maintain the jib in a neutral sliding engagement with the boom.
Step 550 can include using controllers on the floating ballasted station in communication with the soft yoke and with at least one controller on the transport vessel to monitor and control: offloading of the liquefied natural gas through the offload flexible conduits to the liquefied natural gas storage tanks, and to monitor and control flow of the hydrocarbon vapor from the transport vessel to the floating ballasted station.
Step 552 can include communicating from the controllers to a network to allow client devices of remote users to monitor the loading and offloading of the liquefied natural gas.
Step 554 can include using computer instructions to form an executive dashboard of controllers enabling the remote users to view floating ballasted station functions while monitoring offloading and return vapor flow in real time, 24 hours a day, 7 days as week using less than 10 minute updates from the floating ballasted station to the remote users.
While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.
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