EP2180231A1 - Conversion de gaz naturel liquéfié - Google Patents

Conversion de gaz naturel liquéfié Download PDF

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Publication number
EP2180231A1
EP2180231A1 EP08352024A EP08352024A EP2180231A1 EP 2180231 A1 EP2180231 A1 EP 2180231A1 EP 08352024 A EP08352024 A EP 08352024A EP 08352024 A EP08352024 A EP 08352024A EP 2180231 A1 EP2180231 A1 EP 2180231A1
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EP
European Patent Office
Prior art keywords
heat exchange
exchange fluid
heat exchanger
main
main heat
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP08352024A
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German (de)
English (en)
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designation of the inventor has not yet been filed The
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Cryostar SAS
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Cryostar SAS
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Publication date
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Priority to EP08352024A priority Critical patent/EP2180231A1/fr
Priority to CN200980135979.0A priority patent/CN102216668B/zh
Priority to EP09797605A priority patent/EP2313680B1/fr
Priority to US13/003,896 priority patent/US20110132003A1/en
Priority to ES09797605T priority patent/ES2396178T3/es
Priority to BRPI0916221A priority patent/BRPI0916221A2/pt
Priority to KR1020117003409A priority patent/KR101641394B1/ko
Priority to JP2011518032A priority patent/JP5662313B2/ja
Priority to PCT/IB2009/006682 priority patent/WO2010007535A1/fr
Publication of EP2180231A1 publication Critical patent/EP2180231A1/fr
Ceased legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C9/00—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure
    • F17C9/02—Methods or apparatus for discharging liquefied or solidified gases from vessels not under pressure with change of state, e.g. vaporisation
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2221/00—Handled fluid, in particular type of fluid
    • F17C2221/03—Mixtures
    • F17C2221/032—Hydrocarbons
    • F17C2221/033—Methane, e.g. natural gas, CNG, LNG, GNL, GNC, PLNG
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
    • F17C2223/0107—Single phase
    • F17C2223/0115—Single phase dense or supercritical, i.e. at high pressure and high density
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
    • F17C2223/0146—Two-phase
    • F17C2223/0153—Liquefied gas, e.g. LPG, GPL
    • F17C2223/0161—Liquefied gas, e.g. LPG, GPL cryogenic, e.g. LNG, GNL, PLNG
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
    • F17C2223/04—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by other properties of handled fluid before transfer
    • F17C2223/042—Localisation of the removal point
    • F17C2223/046—Localisation of the removal point in the liquid
    • F17C2223/047—Localisation of the removal point in the liquid with a dip tube
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
    • F17C2225/01—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel characterised by the phase
    • F17C2225/0107—Single phase
    • F17C2225/0123—Single phase gaseous, e.g. CNG, GNC
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2225/00—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel
    • F17C2225/03—Handled fluid after transfer, i.e. state of fluid after transfer from the vessel characterised by the pressure level
    • F17C2225/035—High pressure, i.e. between 10 and 80 bars
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/01—Propulsion of the fluid
    • F17C2227/0128—Propulsion of the fluid with pumps or compressors
    • F17C2227/0135—Pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/01—Propulsion of the fluid
    • F17C2227/0128—Propulsion of the fluid with pumps or compressors
    • F17C2227/0171—Arrangement
    • F17C2227/0185—Arrangement comprising several pumps or compressors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/03—Heat exchange with the fluid
    • F17C2227/0302—Heat exchange with the fluid by heating
    • F17C2227/0309—Heat exchange with the fluid by heating using another fluid
    • F17C2227/0316—Water heating
    • F17C2227/0318—Water heating using seawater
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/03—Heat exchange with the fluid
    • F17C2227/0302—Heat exchange with the fluid by heating
    • F17C2227/0309—Heat exchange with the fluid by heating using another fluid
    • F17C2227/0323—Heat exchange with the fluid by heating using another fluid in a closed loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2227/00—Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid
    • F17C2227/03—Heat exchange with the fluid
    • F17C2227/0367—Localisation of heat exchange
    • F17C2227/0388—Localisation of heat exchange separate
    • F17C2227/0393—Localisation of heat exchange separate using a vaporiser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
    • F17C2250/04—Indicating or measuring of parameters as input values
    • F17C2250/0404—Parameters indicated or measured
    • F17C2250/0439—Temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2250/00—Accessories; Control means; Indicating, measuring or monitoring of parameters
    • F17C2250/06—Controlling or regulating of parameters as output values
    • F17C2250/0605—Parameters
    • F17C2250/0636—Flow or movement of content
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2265/00—Effects achieved by gas storage or gas handling
    • F17C2265/05—Regasification
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2265/00—Effects achieved by gas storage or gas handling
    • F17C2265/07—Generating electrical power as side effect
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
    • F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
    • F17C2270/00—Applications
    • F17C2270/01—Applications for fluid transport or storage
    • F17C2270/0102—Applications for fluid transport or storage on or in the water
    • F17C2270/0105—Ships

Definitions

  • the present invention relates to a method and apparatus for converting liquefied natural gas to a superheated fluid.
  • the method and apparatus are particularly suited for use on board a ship or other ocean-going vessel, for example, an FSRU (Floating Storage and Regasification Unit).
  • FSRU Floating Storage and Regasification Unit
  • Natural gas is conveniently stored and transported in liquid state. It is generally used, however, in gaseous state. There is therefore a need to convert large volumes of liquefied natural gas to a superheated fluid, typically a gas below the critical pressure of natural gas, but sometimes a fluid at a pressure above the critical pressure.
  • US Patent 6 945 049 discloses a method and apparatus for vaporising liquefied natural gas.
  • Liquefied natural gas is pumped through a first heat exchanger to effect vaporisation and a second heat exchanger to raise the temperature of the vapour to approximately ambient temperature, or a little below ambient temperature.
  • the first heat exchanger is heated by a heat exchange fluid, such as propane, flowing in a closed cycle.
  • propane changes from gaseous to liquid state in the first heat exchanger and is converted to a gas again in a plurality of heat exchangers which are typically heated by a flow of sea water.
  • the vaporiser natural gas is heated by a flow of steam.
  • the method and apparatus according to the invention aim at reducing the surface area of corresponding heat exchangers without undue loss of thermodynamic efficiency.
  • a method of converting liquefied natural gas to a superheated fluid comprising the steps of:
  • the said resulting vapour in step (e) may be turbo-expanded intermediate the first supplementary heat exchanger and the first main heat exchanger.
  • the turbo-expansion makes possible power recovery from the vapour.
  • the invention also provides apparatus for converting liquefied natural gas to a superheated fluid comprising:
  • the apparatus according to the invention may also include in the first endless heat exchange fluid circuit a turbo-expander intermediate the first supplementary heat exchanger and the first main heat exchanger.
  • the turbo-expander may be operatively associated with power generation means, thereby making possible the recovery of power.
  • the employment of different condensing pressures in the first and second heat exchange fluid circuits makes it possible to keep down the surface area of the first and second main heat exchangers without undue loss of thermodynamic efficiency.
  • the temperature difference between the temperature of the first heat exchange fluid at its inlet to the first main heat exchanger and the temperature of the natural gas at its exit from the first main heat exchanger is greater than the temperature difference between the temperature of the second heat exchange fluid at its inlet to the second main heat exchanger and the temperature of the natural gas at its exit from the second main heat exchanger.
  • each of the main and supplementary heat exchangers may comprise a single body or core or a plurality of bodies or cores. If plural, the heat exchange bodies or cores may be arranged in series or in parallel.
  • the apparatus according to the invention preferably additionally comprises at least one liquid pump for taking liquid heat exchange fluid from the collection vessel and for circulating it through the first and second endless heat exchange circuits.
  • the liquid heat exchange fluid in the first and second heat exchange circuits is preferably collected in a common collection vessel which is shared by the first and second heat exchange fluid circuits. Accordingly, the first heat exchange fluid is preferably the same as the second heat exchange fluid.
  • each circuit may have its own collection vessel and its own liquid pump.
  • the first heat exchange fluid may be different from the second heat exchange fluid.
  • the flow rates of the first and second heat exchange fluids through the first and second main heat exchangers, respectively, are preferably varied in accordance with any changes in the thermal load thereupon.
  • the control means preferably includes a first valve means adapted to be operated so as to vary the flow rate of the first heat exchange fluid through the first main heat exchanger in accordance with any variation in the thermal load thereupon.
  • the control means preferably includes a second valve means which is also preferably adapted to be operated so as to vary the flow rate of the second heat exchange fluid through the second main heat exchanger in accordance with any variations in the thermal load thereupon.
  • the first endless heat exchange circuit includes a turbo-expander, the flow rate may be controlled by the inlet guide vanes of the turbo-expander.
  • this circuit preferably additionally includes a liquid pump with a variable frequency drive operable to vary the pressure ratio across the turbo-expander. This enables the circuit to cater for different re-vaporising and condensing temperatures.
  • the first valve means is preferably positioned in the first endless heat exchange fluid circuit intermediate the liquid pump and the inlet of the first heat exchange fluid to the first supplementary heat exchanger.
  • the second valve means is preferably positioned in the second endless heat exchange fluid circuit immediate the outlet for the second heat exchange fluid from the second main heat exchanger and the common collection vessel.
  • the apparatus according to the invention preferably also includes a conduit for recirculating condensed heat exchange fluid to the common collection vessel and a third valve means in the conduit for opening (or increasing the flow rate through) the said conduit in the event of the thermal load on the apparatus falling below a chosen minimum.
  • the pressure in the ullage space of the common collection vessel is essentially the condensing pressure of the first endless circuit exchange fluid.
  • the first and second liquid heat exchange fluids may be heated in the first and second supplementary heat exchangers by any convenient medium, but the temperature of this medium influences the choice of the heat exchange fluid.
  • Sea water is typically a convenient medium to use on board a seagoing vessel, but other media such as fresh water, engine cooling water or a mixture of water and ethylene glycol can be used instead.
  • propane is a preferred choice for both the first and second heat exchange fluids.
  • Propane is readily available commercially and has thermodynamic properties that enable the condensing temperatures in the first and second main heat exchangers to be selected to be above minus 40°C but below plus 15°C.
  • Other heat exchange fluid can be used instead of or in a mixture with propane.
  • Such alternative or additional heat exchange fluids contain ethane, butane, other hydrocarbons and fluorocarbon refrigerants, particularly R134(a).
  • the selected heat exchange fluid preferably has a positive equilibrium pressure down to minus 30°C or minus 40°C. If the temperature of the seawater (or alternative medium) is particularly low, the first and second heat exchange fluids may both be composed of the same mixture of propane and ethane. If, on the other hand, such temperature is particularly high, the first and second heat exchange fluids may both be composed of the same mixture of propane and butane.
  • the first and second heat exchange fluids may be fully vaporised and, if desired, superheated in the first and second supplementary heat exchangers. If desired, there may be a superheating section separate from the vaporising section. Both such sections may be provided in different bodies. Alternatively, they may be partially vaporised in the first and second heat exchangers, in which case both the first and second heat exchange circuits may include a phase separator to disengage unvaporised heat exchange fluid from its vapour. The resulting liquid may be returned to the collection vessel associated with the heat exchange circuit.
  • first endless heat exchange fluid circuit 20 that causes the heat exchange fluid to flow through the first main heat exchanger 10 and the first supplementary heat exchanger 14, and a second such circuit 22 which causes the heat exchange fluid to flow through the second main heat exchanger 12 and the second supplementary heat exchanger 16.
  • the circuits 20 and 22 have in common a liquid heat exchange fluid collection vessel 24 and a pump 26 for raising the pressure to which the liquid heat exchange fluid is subjected. It is, however, possible for each circuit to have its own dedicated collection vessel.
  • the first endless heat exchange fluid circuit 20 extends from a liquid outlet from the first main heat exchanger 10 to the liquid collection vessel 24 and includes the pump 26.
  • the first heat exchange fluid circuit 20 extends through the first supplementary heat exchanger 14 in which the liquid heat exchange fluid is reconverted to a vapour.
  • the heat exchange fluid circuit 20 is completed by a conduit placing the outlet for vaporised heat exchange fluid from the first supplementary heat exchanger 14 in communication with an inlet for vaporised heat exchange fluid to the main heat exchanger 10. If desired, both the heat exchange circuits may communicate or be able to be placed in communication with a source of back up heat exchange fluid to enable any loss of heat exchange fluid from the circuits to be made up.
  • Sufficient flow of the heat exchange fluid through the first main heat exchanger 10 is provided so as to vaporise all the liquefied natural gas flowing there through and to superheat it to a chosen temperature.
  • the pump 8 may typically raise the pressure of the liquefied natural gas to above its critical pressure, say to about 100 bar, in which case, the natural gas enters the first main heat exchanger 10 is a supercritical fluid, so strictly speaking, is not vaporised.
  • the apparatus shown in Figure 1 is operated so as to ensure that the temperature at which it leaves the first main heat exchanger 10 is in a chosen temperature range, somewhat below 0°C.
  • the second heat exchange circuit 22 is operated so as to raise the temperature of the natural gas further to a chosen delivery value.
  • some liquid heat exchange fluid is diverted from the first heat exchange fluid circuit 20 from a region downstream of the pump 26 and flows through the second supplementary heat exchanger 16 in which it is vaporised.
  • the resulting vapour flows to an inlet for heat exchange fluid to the second main heat exchanger 12.
  • This heat exchange fluid is condensed in the second main heat exchanger 12 by heat exchange with the natural gas, the natural gas thereby being heated to the desired temperature.
  • the so condensed heat exchange fluid passes from the second main heat exchanger to the common collection vessel 24 via a pipe or conduit 34.
  • the necessary heat for the first and second supplementary heat exchangers 14 and 16 may be provided by any convenient supplementary heat exchange medium.
  • the liquid vessel 24 is provided with a recycle conduit 28.
  • One end of the conduit 28 terminates in a common region of the heat exchange circuits 20 and 22 which is downstream of the outlet of the pump 26 but upstream of where the second heat exchange circuit 22 branches from the first heat exchange circuit 20.
  • the other end of the conduit 28 terminates within the liquid collection vessel 24.
  • a valve 30 is disposed within the conduit 28. The valve 30, when open, enables condensed heat exchange fluid to be withdrawn from the heat exchange circuits 20 and 22. Such withdrawal may be carried out if the thermal load on the main heat exchangers 10 and 12 falls below a chosen level.
  • the rate of flow of heat exchange fluid through the main heat exchangers 10 and 12 are controlled by a first valve 32 and a second valve 36, respectively.
  • the first valve 32 is positioned intermediate the outlet of the pump 26 and the inlet for the heat exchange fluid to the first supplementary heat exchanger 14.
  • the second valve 36 is positioned in the conduit 34.
  • the valves 32 and 36 are operated so as to vary the flow rates of the heat exchange fluid through the first and second main heat exchangers 10 and 12, respectively with any changes in the thermal load thereupon.
  • the heat exchange fluid effects indirect heat exchange between the supplementary heat exchange medium and the liquefied natural gas.
  • seawater is a particularly convenient supplementary heat exchange medium. It can, for example, be taken from the surroundings of the ship or FSRU. Other media such as fresh water, engine cooling water, or a mixture of water and ethylene glycerol can be used instead.
  • the supplementary heat exchange medium may flow in open or closed circuit. If in closed circuit, the temperature of the supplementary heat exchange medium may be readily controlled by means of an additional heat source, for example, a boiler, and the heat exchange fluid selected in accordance with this temperature.
  • the preferred heat exchange fluid is propane.
  • Propane is readily available commercially and has thermodynamic properties that enable the condensing temperatures in the first and second main heat exchangers 10 and 12 to be above minus 40°C but below +15°C.
  • the supplementary heat exchange medium for example, sea water
  • the propane may be mixed with ethane for lower supplementary heat exchange medium temperatures and with butane for higher temperatures.
  • the choice of the heat exchange fluid needs to be made in light of these factors, bearing in mind that the heat exchange fluid desirably has a positive equilibrium pressure down to minus 30°C and preferably down to minus 40°C.
  • the thermal load on the heat exchangers 10 and 12 that is the heat they are required to provide in order to raise the temperature of the LNG from its storage temperature of below minus 150°C to a chosen supply temperature (for example +5°C) is likely to vary.
  • the apparatus shown in Figure 1 is able to meet these variations.
  • the flow of the heat exchange fluid through the first supplementary heat exchanger 14 is typically such as to cool the sea water or other medium by 5 to 7°C.
  • the heat exchange fluid is changed in state from liquid to vapour in the first supplementary heat exchanger 14 and may be slightly superheated. It is this vapour that serves to heat the LNG in the first main heat exchanger 10.
  • the heat exchange fluid condenses again in the first main heat exchanger 10.
  • the operation of the second main heat exchanger 12 is analogous to that of the first main heat exchanger 10.
  • the natural gas is heated in it by indirect heat exchange with condensing heat exchange fluid.
  • the operation of the valves 32 and 36 has the effect of making the condensing pressure in the second main heat exchanger 12 higher than in the first main heat exchanger 10.
  • the difference in the condensing pressures is equal to the differential pressure across the pump 26 minus the pressure drops in the relevant piping and heat exchangers.
  • the condensing pressure in the first main heat exchanger is equal to the condensing pressure in the ullage space of the common collection vessel. This pressure is not fixed but tends to float as the heat exchange circuits adjust to a change in the thermal load.
  • the condensing pressure in the first main heat exchanger 10 is lower, these pressure changes being brought about by adjustment of the valve 32 in response to changes in the thermal load upon the heat exchanger 10. If desired, the adjustment of the valve 32 may be effected automatically in response to a parameter which is a function of the changes in thermal load.
  • the valve 36 may be similarly adjusted and because the condensing pressure in the first main heat exchanger 10 floats, so does the condensing pressure in the second main heat exchanger 12.
  • the condensing pressure in the second main heat exchanger 12 is greater than the condensing pressure in the first main heat exchanger 10
  • the sizes of the two heat exchangers can readily be kept down without undue loss of thermodynamic efficiency even at low sea water (or other supplementary exchange medium) temperatures.
  • the first main heat exchanger 10 is called upon to meet a larger thermal load than the second main heat exchanger. It is preferred that the difference in temperature between the heat exchange fluid entering the first main heat exchanger 10 and the natural gas exiting it is greater than the difference in temperature between the heat exchange fluid entering the second main heat exchanger 12 and the natural gas exiting from it.
  • the pressure difference across the pump 26 is a significant factor in determining the difference in condensing pressure and hence condensing temperature between the two main heat exchangers 10 and 12.
  • the pump 26 has a constant frequency drive and therefore the differential pressure cannot be altered. This is not a disadvantage as the apparatus shown in Figure 1 can generally cope with normal changes in thermal load that are encountered. If the thermal load falls too much causing the control valves 32 and 36 to throttle the flow too much, the setting of the valve 30 is able automatically to maintain the minimum flow through the pump 26 necessary for it be run. If the thermal load rises too much, then a valve (not shown) in the LNG pipeline can be adjusted to reduce the LNG flow. At lower sea water inlet temperatures however (say in the order of 10°C), it may be advantageous to use a variable frequency pump 26 and operate it at a slightly increased pressure differential to reduce the condensing temperature in the first main heat exchanger 10 at higher thermal loads.
  • the first main heat exchanger 10 raises the temperature of the LNG to minus 40 to minus 20°C so that it vaporises (unless at a supercritical pressure) and the second main heat exchanger 12 further raises its temperature to 0 to 5°C.
  • the first main heat exchanger 10 may typically meet 80% of the thermal load and the second main heat exchanger 12 the remaining 20%.
  • the heat exchange fluid is propane, and the supplementary heat exchange medium is seawater.
  • the apparatus shown in Figure 1 is essentially self-adjusting to changes in the LNG vaporisation load placed upon it. If the LNG flow decreases, there will be a lower rate of condensation of propane in the heat exchangers 10 and 12 and the propane pressure will increase in the supplementary heat exchangers 14 and 16 and the common collection vessel. This increase in pressure has a compensatory effect on the propane vaporisation rate by decreasing the temperature difference between the supplementary heat exchange medium and the vaporising propane in the heat exchangers 14 and 16.
  • the heat exchange circuits 20 or 22 are able to adjust to keep the temperature of the vaporised propane no more than a few degrees Celsius above its boiling temperature.
  • the LNG flow increases, there will be a higher rate of condensation of propane in the heat exchangers 10 and 12 and the propane pressure will fall in the supplementary heat exchangers 14 and 16 and the common collection vessel 24.
  • This decrease in pressure has a compensatory effect on the propane vaporisation rate by increasing the temperature difference between the supplementary heat exchange medium and the vaporising propane in the heat exchangers 14 and 16.
  • the heat exchange circuits 20 and 22 are able to adjust to keep the temperature of the vaporised propane no more than a few degrees Celsius above its boiling temperature.
  • the apparatus shown in Figure 2 enables superheating of the propane (or other heat exchange fluid in the supplementary heat exchangers 14 and 16 to be avoided.
  • the heat exchange circuits 20 and 22 both include phase separators, and the supplementary heat exchangers 14 and 16 effect only partial vaporisation of the propane or other heat exchange fluid.
  • a first phase separator 40 is provided in the first heat exchange circuit 20 intermediate the propane exit and of the first supplementary heat exchanged 14 and the propane inlet end of the first main heat exchanger 10. If desired, as shown in Figure 2 , the first supplementary heat exchanger 14 may be split and comprise two parallel heat exchange units 14(a) and 14(b).
  • the first phase separator 40 has an inlet 42 for a liquid-vapour propane mixture to a vessel 44, in which the liquid phase collects.
  • the phase separator vessel 44 has a first outlet 46 at its top for vapour communicating with the propane inlet to the first main heat exchanger 10, and a second outlet 48 at its bottom for liquid propane communicating with the common collection vessel 24.
  • a flow control valve 52 is located at the conduit 50 and is operatively associated with a level detector 54 in the vessel 44 such that a constant liquid propane level can be maintained thereon.
  • a demister 56 is located in the vessel 44 in order to disengage droplets of liquid from the vapour flowing to the first main heat exchanger 10.
  • a second phase separator 60 is provided in the second heat exchange circuit 22 intermediate the propane exit end of the second supplementary heat exchanger 16 and the propane exit end of the second main heat exchanger 12.
  • the second phase separator 60 has an inlet 62 for a liquid-vapour mixture to a vessel 64, a first outlet 66 at its top for vapour communicating with the propane inlet to the second main heat exchanger 12, and a second outlet 68 at its bottom for liquid propane communicating via conduit 70 with the common liquid propane collection vessel 24.
  • a flow control valve 72 is located in the conduit 70 and is operatively associated with a level detector 74 in the vessel 64 such that a constant liquid level can be maintained therein.
  • a demister 76 is located in the vessel 64 in order to disengage droplets of liquid from the vapour flowing to the second main heat exchanger 12.
  • the heat exchanger 14 may be split into two parallel parts.
  • the apparatus shown in Figure 2 has an additional liquid pump 80 to assist in the circulation of the liquid propane.
  • the pumps 26 and 80 are operable to vary, if desired, the pressure difference between the propane in the heat exchange circuits 20 and 22.
  • the heat exchange circuits 20 and 22 are self-adjusting in a manner analogous to the corresponding circuits in the apparatus shown in Figure 1 .
  • the apparatus may be charged with propane via a conduit 78 having stop valve 79 disposed therein and terminating in the collection vessel 24.
  • both the heat exchange circuits 20 and 22 have dedicated liquid propane collection vessels 82 and 84, respectively.
  • the circuits 20 and 22 are separate from each other and each circuit has its own liquid propane supply pipeline 86, having a stop valve 88 disposed therein, terminating in the vessel 82, and the circuit 22 has a liquid propane supply pipeline 90, with a stop valve 92 disposed therein, terminating in the vessel 64.
  • both the heat exchange circuits 20 and 22 have dedicated liquid collection vessels 82 and 84, respectively.
  • the circuits 20 and 22 have dedicated liquid collection vessels 82 and 84, respectively.
  • the circuits 20 and 22 are separate from each other.
  • the circuit 20 has its own liquid heat exchange fluid supply pipeline 86, having a stop valve 88 disposed therein, terminating in the vessel 82, and the circuit 22 has a liquid heat exchange fluid supply pipeline 90, with a stop valve 92 disposed therein, terminating the vessel 84.
  • the heat exchange fluid in the circuit 20 can be of the same or a different composition from that of the heat exchange fluid in the circuit 22.
  • the circuit 20 has a turbo-expander 100 intermediate the heat exchange vapour exit from the supplementary heat exchanger 14 and the heat exchanger vapour inlet to the main heat exchanger 10.
  • the turbo-expander 100 is operatively associated in a conventional way with a generator 104 that is connected to an electrical grid 106, thus making possible power recovery from the heat exchanger fluid.
  • the cycle pump 26 is designed correspondingly for a higher differential pressure to suit the turbine design pressure ratio and is equipped with a variable frequency drive 110 to adapt the pressure ratio for different re-vaporising and condensing temperatures.
  • the pump 26 creates the necessary pressure differential for the operation of the turbo-expander 100 to generate electrical power in addition to circulating the heat exchange fluid in the circuit 20.
  • the pump 80 circulates the heat exchange fluid in the circuit 22.
  • both pumps 26 and 80 compensate for pressure drops in the apparatus.
  • operation of the apparatus shown in Figure 4 is analogous to that shown in Figures 1 and 3 .

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)
EP08352024A 2008-07-15 2008-10-24 Conversion de gaz naturel liquéfié Ceased EP2180231A1 (fr)

Priority Applications (9)

Application Number Priority Date Filing Date Title
EP08352024A EP2180231A1 (fr) 2008-10-24 2008-10-24 Conversion de gaz naturel liquéfié
CN200980135979.0A CN102216668B (zh) 2008-07-15 2009-07-15 液化天然气的转化
EP09797605A EP2313680B1 (fr) 2008-07-15 2009-07-15 Conversion de gaz naturel liquéfié
US13/003,896 US20110132003A1 (en) 2008-07-15 2009-07-15 Conversion of liquefied natural gas
ES09797605T ES2396178T3 (es) 2008-07-15 2009-07-15 Conversión de gas natural licuado
BRPI0916221A BRPI0916221A2 (pt) 2008-07-15 2009-07-15 conversão de gás natural liquefeito
KR1020117003409A KR101641394B1 (ko) 2008-07-15 2009-07-15 액화 천연 가스 변환 방법 및 장치
JP2011518032A JP5662313B2 (ja) 2008-07-15 2009-07-15 液化天然ガスの変換
PCT/IB2009/006682 WO2010007535A1 (fr) 2008-07-15 2009-07-15 Conversion de gaz naturel liquéfié

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP08352024A EP2180231A1 (fr) 2008-10-24 2008-10-24 Conversion de gaz naturel liquéfié

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EP2180231A1 true EP2180231A1 (fr) 2010-04-28

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2638942A1 (fr) * 2012-03-15 2013-09-18 Cryostar SAS Appareil de séparation de brouillard

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1922779A1 (de) * 1968-05-10 1970-06-25 Linde Ag Verfahren und Einrichtung zum Verdampfen von tiefsiedenden Fluessigkeiten,insbesondere Erdgas
DE2633713A1 (de) * 1976-07-27 1978-02-02 Linde Ag Verfahren zur erwaermung von verfluessigtem erdgas
GB2008239A (en) * 1977-11-17 1979-05-31 Borsig Gmbh A Vaporising Process
EP0043212A1 (fr) * 1980-07-01 1982-01-06 Costain Petrocarbon Limited Production de puissance à partir d'un fluide cryogénique
US20030159800A1 (en) * 2002-02-27 2003-08-28 Nierenberg Alan B. Method and apparatus for the regasification of LNG onboard a carrier
US6945049B2 (en) 2002-10-04 2005-09-20 Hamworthy Kse A.S. Regasification system and method

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1922779A1 (de) * 1968-05-10 1970-06-25 Linde Ag Verfahren und Einrichtung zum Verdampfen von tiefsiedenden Fluessigkeiten,insbesondere Erdgas
DE2633713A1 (de) * 1976-07-27 1978-02-02 Linde Ag Verfahren zur erwaermung von verfluessigtem erdgas
GB2008239A (en) * 1977-11-17 1979-05-31 Borsig Gmbh A Vaporising Process
EP0043212A1 (fr) * 1980-07-01 1982-01-06 Costain Petrocarbon Limited Production de puissance à partir d'un fluide cryogénique
US20030159800A1 (en) * 2002-02-27 2003-08-28 Nierenberg Alan B. Method and apparatus for the regasification of LNG onboard a carrier
US6945049B2 (en) 2002-10-04 2005-09-20 Hamworthy Kse A.S. Regasification system and method

Non-Patent Citations (1)

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Title
KOCH, HEISS, STÄNGL: "Uebungsaufgaben + Musterlösungen", 1985, LEHRSTUHL A FÜR THERMODYNAMIK DER TUM, MÜNCHEN, XP002526658 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2638942A1 (fr) * 2012-03-15 2013-09-18 Cryostar SAS Appareil de séparation de brouillard

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