Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0211—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
  • F25J1/0212—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a single flow MCR cycle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B21/00—Tying-up; Shifting, towing, or pushing equipment; Anchoring
  • B63B21/50—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers
  • B63B21/507—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers with mooring turrets
  • B63B21/508—Anchoring arrangements or methods for special vessels, e.g. for floating drilling platforms or dredgers with mooring turrets connected to submerged buoy
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B22/00—Buoys
  • B63B22/02—Buoys specially adapted for mooring a vessel
  • B63B22/021—Buoys specially adapted for mooring a vessel and for transferring fluids, e.g. liquids
  • B63B22/023—Buoys specially adapted for mooring a vessel and for transferring fluids, e.g. liquids submerged when not in use
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B22/00—Buoys
  • B63B22/02—Buoys specially adapted for mooring a vessel
  • B63B22/021—Buoys specially adapted for mooring a vessel and for transferring fluids, e.g. liquids
  • B63B22/026—Buoys specially adapted for mooring a vessel and for transferring fluids, e.g. liquids and with means to rotate the vessel around the anchored buoy
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
  • F25J1/0022—Hydrocarbons, e.g. natural gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
  • F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
  • F25J1/0035—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by gas expansion with extraction of work
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
  • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
  • F25J1/005—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by expansion of a gaseous refrigerant stream with extraction of work
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
  • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
  • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant stream
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
  • F25J1/007—Primary atmospheric gases, mixtures thereof
  • F25J1/0072—Nitrogen
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
  • F25J1/008—Hydrocarbons
  • F25J1/0087—Propane; Propylene
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
  • F25J1/0097—Others, e.g. F-, Cl-, HF-, HClF-, HCl-hydrocarbons etc. or mixtures thereof
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
  • F25J1/0204—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a single flow SCR cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
  • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
  • F25J1/0262—Details of the cold heat exchange system
  • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
  • F25J1/0265—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
  • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
  • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
  • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
  • F25J1/0275—Construction and layout of liquefaction equipments, e.g. valves, machines adapted for special use of the liquefaction unit, e.g. portable or transportable devices
  • F25J1/0277—Offshore use, e.g. during shipping
  • F25J1/0278—Unit being stationary, e.g. on floating barge or fixed platform
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B63—SHIPS OR OTHER WATERBORNE VESSELS; RELATED EQUIPMENT
  • B63B—SHIPS OR OTHER WATERBORNE VESSELS; EQUIPMENT FOR SHIPPING 
  • B63B22/00—Buoys
  • B63B22/02—Buoys specially adapted for mooring a vessel
  • B63B2022/028—Buoys specially adapted for mooring a vessel submerged, e.g. fitting into ship-borne counterpart with or without rotatable turret, or being releasably connected to moored vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2205/00—Processes or apparatus using other separation and/or other processing means
  • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
  • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
  • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
  • F25J2220/62—Separating low boiling components, e.g. He, H2, N2, Air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
  • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
  • F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
  • F25J2240/40—Expansion without extracting work, i.e. isenthalpic throttling, e.g. JT valve, regulating valve or venturi, or isentropic nozzle, e.g. Laval
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
  • F25J2290/60—Details about pipelines, i.e. network, for feed or product distribution

Definitions

• the invention relates to a method for offshore produc ⁇ tion of liquefied natural gas, wherein natural gas is supplied from an underground source to a field installation for gas treatment, the gas after possible purification being transferred in compressed form from the field installation to a LNG ⁇ tanker, the transfer taking place through a pipeline surrounded by sea water, and wherein the compressed gas is fed to a conversion plant provided on the LNG tanker and arranged to convert at least a part of the gas to liquefied form by expansion of the gas, and the so liquefied gas is transferred to storage tanks on board the tanker.
• the invention relates to a system for offshore production of liquefied natural gas, comprising a field instal ⁇ lation for treatment of natural gas supplied to the installation from an underground source, equipment arranged on the field installation for gas purification and for compression of the natural gas to a high pressure, and a pipeline surrounded by sea water for transfer of the compressed gas to a LNG tanker, the LNG tanker including a plant for conversion of at least a part of the gas to liquefied form by expansion of the gas, and storage tanks for storage of the liquefied gas on the tanker.
• a method and a system of the above-mentioned type are known from US patent No. 5 025 860.
• the natural gas is purified on a platform or a ship and is thereafter transferred in compressed and cooled form via a high-pressure line to a LNG tanker where the gas is converted to liquefied form by expansion.
• the liquefied gas is stored on the tanker at a pressure of approximately 1 bar, whereas non-liquefied residual gases are returned to the platform or ship via a return line.
• the high-pressure line and the return line which extend through the sea between the platform/ship and the LNG tanker, at both ends are taken up from the sea so that the end portions of the lines extend up from the water surface through free air and at their ends are connected to respective treatment units on the plat ⁇ form/ship and the LNG tanker, respectively.
• the high-pressure line and the return line will be subjected to external influences of different kinds under the different operational conditions which may occur in practice. Difficult weather conditions with storms 5 and high waves will place clear limitations on the system operation, as both security reasons and practical reasons will then render impossible disconnection of the lines from a LNG tanker having full loading tanks, and connection of the lines to another, empty LNG tanker.
• STP Submerged Turret Production
• a submerged buoy of the type comp ⁇ rising a central bottom-anchored member communicating with the topical underground source through at least -one flexible riser, o and which is provided with a swivel unit for the transfer of fluid to a production installation on the vessel.
• this technique reference may be made to e.g. Norwegian laying-open print No. 175 419.
• STL buoy Submerged Turret Loading
• STL Submerged Turret Loading
• Another object of the invention is to provide a method and a system of the topical type which utilizes the STL/STP technique and the possibilities involved therein with respect to flexibility, safety and efficient utilization of the resources.
• a further object of the invention is to provide a method and a system of the topical type which result in a relatively simple and cheap installation for conversion of natural gas to LNG.
• a method of the introductorily stated type which, according to the invention, is characterized in that the gas is supplied to the pipeline at a relatively high temperature, the pipeline being made heat transferring and having a suf ⁇ ficiently long length that the gas during the transfer through the pipeline is cooled to a desired low temperature near the sea water temperature during heat exchange with the surrounding sea water, and that the pipeline, when the storage tanks on the LNG tanker are filled up, is disconnected from the LNG tanker and connected to another, similar tanker, the pipeline being permanently connected to a submerged buoy which is arranged for introduction and releasable securement in a submerged downwardly open receiving space in the tanker, and which is provided with a swivel unit for transfer of gas under a high pressure.
• a method of the introduc ⁇ torily stated type which, according to the invention, is characterized in that the gas is supplied to the pipeline at a temperature substantially below the sea water temperature, the low temperature of the gas being maintained during the transfer through the pipeline in that this is made heat insulating, and that the pipeline, when the storage tanks on the LNG tanker are filled up, is disconnected from the LNG tanker and connected to another, similar tanker, the pipeline being permanently connected to a submerged buoy which is arranged for introduction and releasable securement in a submerged downwardly open receiving space in the tanker, and which is provided with a swivel unit for transfer of gas under a high pressure.
• a system of the introductorily stated type which, according to the invention, is characterized in that the pipeline at the end which is remote from the field installation, is permanently connected to at least one submerged buoy which is arranged for introduction and releasable securement in a submerged downwardly open receiving space at the bottom of the LNG tanker, and which is provided with a swivel unit for transfer of gas under a high pressure.
• the utilization of the STL/STP concept entails that it is only necessary with minor hull modifications in order to construct the necessary receiving space for reception of the topical buoys.
• the hull of the LNG tanker can be designed in an optimal manner, so that vessels having a good seaworthiness can be obtained.
• the system will be far less subject to collisions and far less subject to external weather influences, as compared to the introductorily mentioned, known s system. Further, one achieves the operational advantage that the LNG tanker can turn about the buoy under the influence of wind, waves and water currents.
• the pipeline which is connected to the buoy can be connected and disconnected from the LNG tanker in a simple, quick and safe manner, also under very difficult 0 weather conditions.
• the pipeline may be combined or integrated with a gas return line, and possibly also with a line for transfer of electrical power, in which case these lines then will be connected to special courses or transfer means in the buoy. This makes possible a simple transfer of return gas and/or s possible electrical surplus power from the LNG tanker to the field installation.
• a suitable pretreatment of the gas on the field installation such as removal of condensate, dehydration of the o gas and removal of C0 2 , whereafter the gas is processed so as to be transferred through the pipeline to the LNG tanker in a condition which is optimized with a view to simplified and economic conversion of the gas to liquid form in the conversion plant on the LNG tanker.
• the gas is compressed 5 to a high pressure, preferably of at least 250 bars, whereby the gas is heated to a correspondingly high temperature, e.g. approximately 100 °C.
• the gas thereafter is transferred through the pipeline in this form, and the pipeline then is made heat- transferring and has such a length that the gas temperature is o lowered to the desired low level during the transfer.
• the compressed gas may also be advantageous to cool the compressed gas "maximally" at the field installation, i.e. to a temperature substantially below 0 °C, and to transfer the gas in a compressed and cooled condition.
• the low tempe- 5 rature will be maintained during the transfer through the pipeline, the pipeline then being made heat insulating.
• FIG. 1 is a schematic view showing the fundamental construction of the system according to the invention
• Fig. 2 shows a block diagram of a first embodiment of a plant for conversion of compressed natural gas on the transport s vessel
• Fig. 3 shows a block diagram of a second embodiment of such a conversion plant.
• the system comprises a floating production vessel (STP vessel) in the form of a barge o l on which there is arranged a field installation 2 for treatment of gaseous fluid which, under a high pressure (e.g. approximately 200 bars) , flows up from an underground source 3.
• the gaseous fluid is supplied through a wellhead 4 and a flexible riser 5 which extends through the body of water 6 and at its upper end s is connected to a STP buoy 7 of the introductorily mentioned type.
• the buoy is introduced into and releasably secured in a submerged downwardly open receiving space 8 at the bottom of the barge 1.
• the buoy comprises a swivel unit forming a flow connection between the riser 5 and a pipe system 0 (not shown) arranged on the barge between the swivel and the field installation 2.
• the central member of the buoy is anchored to the sea bed 9 by means of a suitable anchoring system comprising a number of anchor lines 10 (only partly shown).
• a suitable anchoring system comprising a number of anchor lines 10 (only partly shown).
• the field installation 2 consists of a number of processing units or modules 11 for suitable treatment of the supplied gas fluid, according to the composition of the well flow o from the source 3 in the topical case.
• the gas consists of a number of components, such as condensate and C0 2 , in addition to the natural gas proper.
• the processing module the condensate (liquid fraction) is removed, the gas is dehy ⁇ drated and C0 2 is removed.
• the separated condensate is stored on 5 the barge, and is later transferred through a hose connection 12 to loading tanks on a conventional shuttle tanker 13 taking care of transport of the condensate to a land terminal.
• the dehydrated gas is compressed to a desired high pressure, preferably at least 300 bars, whereby also a heating of the gas to a relatively high temperature takes place.
• the gas is now in a condition which is optimized with a view to conversion of the gas to liquid form in a conversion plant which 5 is substantially cheaper to construct than conventional LNG plants.
• it may, however, in some cases be advantageous also to cool the compressed gas "maximally" before the gas is supplied to the LNG plant.
• a flexible pipeline 14 which is arranged for transfer o of the compressed gas, extends through the body of water (the sea water) 6 between the barge 1 and a floating transport vessel in the form of a LNG tanker 15.
• One end of the pipeline at the barge 1 is permanently connected to the STP buoy 7 and is connected to the field installation 2 via the swivel unit of the buoy and said s pipe system on the barge.
• the other end of the pipeline 14 is permanently connected to an additional STP buoy 16 which is introduced into and releasably secured in a submerged downwardly open receiving space 17 in the vessel 15.
• the buoy is provided with a swivel unit which may be of a similar design as that of 0 the swivel unit in the buoy 7, and its central member is anchored to the sea bed 9 by means of an anchoring system comprising a number of anchor lines 18.
• buoy 16 there is also provided an additional submerged buoy 19 (buoy II) which is 5 anchored to the sea bed by means of anchor lines 20.
• the pipeline 14 is also permanently connected to this buoy via a branch pipeline in the form of a flexible riser 14 ' which is connected to the pipeline 14 at a branch point 21.
• the purpose of the arrangement of two buoys will be further described later.
• the pipeline 14 may extend over a substantial length in the sea, whereby a suitable distance between the barge 1 and the buoys I and II in practice may be 1-2 km.
• An installation or plant 22 for conversion of compres ⁇ sed gas to liquid form is provided on the LNG tanker 15.
• the plant is supplied with compressed gas from the pipeline 14, the
• Liquefied natural gas which is produced in the plant is stored in tanks 23 on board the vessel.
• the natural gas 1 is supplied in compres ⁇ sed and more or less cooled form to the conversion plant 22, and o this plant therefore mainly is based on expansion of the gas to convert at least a part thereof to liquid form.
• one or more cooling steps which are located either before or after the expansion step or steps.
• the constructive design of the plant s partly will be dependent on the nature of the topical gas, and partly on the results which are wanted to be achieved, i.a. with respect to efficiency, utilization of surplus energy, residual gas etc. which is produced during the process.
• the pipeline 14 may also comprise a return line for the transfer of such gas from the conversion plant back to the field installation. Further, in some cases it will be convenient to produce electrical energy as a by- 5 product during the LNG process. In such cases the pipeline 14 may also comprise a power cable for the transfer of electric current from the LNG tanker 15 to the barge 1, as the swivel units of the STP buoys may be constructed for such transfer.
• the LNG tanker 15 is connected to o the loading buoy 16 (buoy I), whereas the additional buoy 19 (buoy II) is submerged, in anticipation of connection to another LNG tanker.
• the conversion plant 22 can produce approximately 8000 tons of LNG per day. With a vessel size of 80 000 tons, the vessel 15 will then be 5 connected to the buoy I for ten days before its storage tanks 23 are full. When the tanks are full, the vessel leaves the buoy I, and the production continuous via the buoy II where another LNG tanker is then connected. The finished loaded vessel transports its load to a receiving terminal.
• LNG tankers may be connected to the shown arrangement of two buoys I and II, to thereby achieve operation with "direct shuttle loading” (DSL) without any interruption in the production.
• DSL direct shuttle loading
• the LNG tanker may leave the field/buoy for at least shorter periods (some days) without this having negative consequences.
• the gas arrives from the production vessel or barge 1 to the conversion plant 22 via the swivel unit of the STP buoy 16, which swivel unit here is designated 30.
• the gas arrives e.g. with a pressure of ap ⁇ proximately 350 bars and a temperature of approximately 5 °C.
• a liquid separator 32 a so-called knock-out drum in which possible condensed liquid and solid particles are separated.
• the gas is transferred via a pipeline 33 to an isentropic expansion turbine or turbo expander 34 wherein the gas is expanded from a high pressure to a low pressure and thereby is strongly cooled to a temperature of around -140 °C at which there is formed liquefied gas of a so-called heavy type. It may here be necessary to use several expansion steps, for example three turbines of 10 MW each.
• An electrical generator 35 for the production of electrical power is connected to the expansion turbine 34. Further, the expansion turbine is bypassed by a bypass line 36 having a Joule-Thomson valve 37 which is influenced by a pressure-sensitive control means 38.
• the expansion turbine is connected through a line 39 to a container or product collector 40 for heavy LNG.
• the pressure is here reduced to a low level, e.g. 3 bars.
• a pipeline 41 leads to a tank 42 for cryogenic storage of the heavy LNG.
• a level control valve 43 controlled by a level sensor 44.
• An additional pipeline 45 which is connected to the top of the container 40, transports gas which has "flashed off" during the expansion process, to a low-pressure heat exchanger unit 46 for additional cooling of this gas.
• a pressure-controlled 5 valve 47 which is controlled by a pressure control unit 48, is connected in the pipeline 45.
• the heat exchanger 46 may be a so- called plate-rib heat exchanger in which the utilized cooling medium may be nitrogen or a mixture of nitrogen and methane. In the heat exchanger most of the content of the gas of hydrocarbons o and liquid is condensed.
• the heat exchanger unit 46 is connected via a pipeline 49 to an additional product container 50 which, through a pipeline 51, is connected to a tank 52 for storage of the liquefied gas from the heat exchanger unit.
• the temperature at s this point in the plant is lowered to a value of approximately -163 °C, and the pressure may be close to 1 bar.
• a level control valve 53 which is control ⁇ led by a level sensor 54.
• an o additional pipeline 55 for discharge of residual gas from the container.
• This gas may, for example, be used as a fuel gas which may be utilized on board the vessel 15, e.g. for operation of the propulsion machinery thereof.
• a pressure-controlled valve 56 which is controlled by 5 a pressure control unit 57.
• the utilized cooling medium in the heat exchanger unit 46 may be e.g. nitrogen.
• This cooling medium circulates in a cooling loop 59 forming part of a cryogenic cooling package 60 of a commercially available type, e.g. a unit o of the type used in plants for the production of liquid oxygen.
• the cooling loop is shown to comprise a low-pressure compressor 61 which is connected to a condenser 62, and a subsequent high- pressure compressor 63 which is connected to a condenser 64, the condenser 64 being connected to a heat exchanger 65 for heat 5 exchange of the cooling medium in the loop 59.
• the heat exchanger 65 contains a first branch leading from the condenser 64 to a cooling expander 66 the output of which is connected through the cooling loop 59 to the heat exchanger 46, and a second branch connecting the cooling loop 59 to the input of the low-pressure compressor 61.
• a cooling medium in the condensers 62 and 64 for example sea water (S ) may be used.
• the swivel unit of the STL buoy 16 is designated 30, and the gas is presupposed 5 to arrive at the conversion plant 22 with a pressure of ap ⁇ proximately 350 bars and a temperature of approximately 5 °C. From the swivel unit the gas is transferred via a pipeline 70 to a liquid separator 71 for separation of possible condensed liquid and solid particles. In this embodiment of the conversion plant, o the gas goes through a precooling before it is subjected to pressure lowering and cooling by means of expansion.
• the gas from the liquid separator 71 thus is transported through a pipeline 72 to a pair of serially connected condensers 73 and 74 in which the temperature of the gas is lowered to approximately -35 °C. s
• the condensers 73 and 74 are cooled by means of a cooling medium circulating in a two-step cooling loop 75 using propane as a cooling medium.
• the cooling loop comprises a compressor 76 which is driven by a generator 77 and is coupled via a condenser 78 to a liquid separator 79.
• the condenser is o cooled by means of sea water (SW).
• liquid separator 79 To the output of the liquid separator 79 there is connected a pair of pipelines 80 and 81 which are connected to a respective one of the two condensers 73 and 74, and these pipelines 80, 81 are connected via the condensers to a respective 5 one of a pair of additional liquid separators 82, 83 the outputs of which are connected to respective inputs of the compressor 76.
• the cooled gas is supplied to an isentropic expansion turbine 85 in which the gas is expanded from a high pressure to a low pressure and thereby is cooled additionally to such a low o temperature that most of the gas is converted to liquid form.
• the temperature here may be approximately -164 °C.
• an electrical generator 86 for the production of electrical power is associated with the expansion turbine 85. Further, the expansion turbine is bypassed by a bypass line 87 5 having a Joule-Thomson valve 88 which is influenced by a pressure-sensitive control means 89.
• the expansion turbine 85 is connected via a line 90 to a product container 91 for the liquefied gas from the expansion turbine 85.
• a pipeline 92 leads to a tank 93 for storage of the produced LNG.
• the pressure here may be approximately 1, 1 atmospheres, and the temperature may be approximately -163 °C.
• a level control valve 94 which is controlled by a level sensor 95.
• an additional pipeline 96 for discharge of residual gas from the container. This gas may be utilized in a similar manner as stated in connection with the embodiment according to Fig. 2.
• a pressure-controlled valve 97 which is controlled by a pressure-control unit 98.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Ocean & Marine Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Filling Or Discharging Of Gas Storage Vessels (AREA)
• Separation By Low-Temperature Treatments (AREA)

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• 1994
  • 1994-12-08 NO NO944754A patent/NO179986C/no not_active IP Right Cessation
• 1995
  • 1995-12-08 AU AU42730/96A patent/AU4273096A/en not_active Abandoned
  • 1995-12-08 US US08/849,346 patent/US6003603A/en not_active Expired - Fee Related
  • 1995-12-08 CA CA002207042A patent/CA2207042A1/en not_active Abandoned
  • 1995-12-08 WO PCT/NO1995/000227 patent/WO1996017777A1/en active Application Filing
  • 1995-12-08 GB GB9711775A patent/GB2311981B/en not_active Expired - Fee Related

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