EP2146132A1 - Conversion de gaz naturel liquéfié - Google Patents

Conversion de gaz naturel liquéfié Download PDF

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Publication number
EP2146132A1
EP2146132A1 EP08352015A EP08352015A EP2146132A1 EP 2146132 A1 EP2146132 A1 EP 2146132A1 EP 08352015 A EP08352015 A EP 08352015A EP 08352015 A EP08352015 A EP 08352015A EP 2146132 A1 EP2146132 A1 EP 2146132A1
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EP
European Patent Office
Prior art keywords
heat exchange
exchange fluid
heat exchanger
main heat
main
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
EP08352015A
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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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Filing date
Publication date
Application filed by Cryostar SAS filed Critical Cryostar SAS
Priority to EP08352015A priority Critical patent/EP2146132A1/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 EP2146132A1 publication Critical patent/EP2146132A1/fr
Ceased legal-status Critical Current

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Classifications

    • 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
    • F17C7/00—Methods or apparatus for discharging liquefied, solidified, or compressed gases from pressure vessels, not covered by another subclass
    • F17C7/02—Discharging liquefied gases
    • F17C7/04—Discharging liquefied gases 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
    • F17C2223/0146—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
    • F17C2223/03—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the pressure level
    • F17C2223/033—Small pressure, e.g. for liquefied gas
    • 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
    • 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
    • F17C2227/0178—Arrangement in the vessel
    • 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
    • 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
    • F17C2227/0302—Heat exchange with the fluid by heating
    • F17C2227/0327—Heat exchange with the fluid by heating with recovery of heat
    • 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
    • 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
    • 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
    • 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
    • F17C2270/011—Barges
    • F17C2270/0113—Barges floating

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 invention also provides apparatus for converting liquefied natural gas to a superheated fluid comprising:
  • 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.
  • the apparatus according to the invention preferably additionally comprises a liquid pump for taking liquid heat exchange fluid from the common 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.
  • 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 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 above minus 40°C but below + 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, 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.
  • an LNG facility 2 typically comprises at least one thermally-insulated storage tank 4 having a submerged LNG pump 6.
  • the outlet of the pump 6 communicates with a conduit 8 having disposed therealong, outside the facility 2, a second LNG pump 9.
  • the outlet of the pump 9 communicates with an apparatus according to the invention for heating the flow of LNG.
  • the facility is typically located aboard a seagoing vessel, which may, for example, be a so-called FSRU (Floating Storage and Regasification Unit).
  • FSRU Floating Storage and Regasification Unit
  • This apparatus includes a first main heat exchanger 10, a second main heat exchanger 12, a first supplementary heat exchanger 14 and a second supplementary heat exchanger 16.
  • the first and second main heat exchangers 10 and 12 are both adapted to be heated by a common condensing heat exchange fluid flowing countercurrently to the natural gas.
  • 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 bilge tanks 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, 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 flows in open circuit, however, its temperature may vary throughout the year and with the geographical location of the ship or FSRU.
  • the incoming temperature of the sea water may accordingly vary between, say, 10 and 27°C.
  • the propane may be mixed with ethane for lower supplementary heat exchange medium temperatures and with butane for higher seawater 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 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 higher, 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 to decreased 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 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.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Filling Or Discharging Of Gas Storage Vessels (AREA)
EP08352015A 2008-07-15 2008-07-15 Conversion de gaz naturel liquéfié Ceased EP2146132A1 (fr)

Priority Applications (9)

Application Number Priority Date Filing Date Title
EP08352015A EP2146132A1 (fr) 2008-07-15 2008-07-15 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

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3018634A (en) * 1958-04-11 1962-01-30 Phillips Petroleum Co Method and apparatus for vaporizing liquefied gases and obtaining power
US3068659A (en) * 1960-08-25 1962-12-18 Conch Int Methane Ltd Heating cold fluids with production of energy
US3479832A (en) * 1967-11-17 1969-11-25 Exxon Research Engineering Co Process for vaporizing liquefied natural gas
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
US6945049B2 (en) 2002-10-04 2005-09-20 Hamworthy Kse A.S. Regasification system and method
WO2007039480A1 (fr) * 2005-09-21 2007-04-12 Exmar Procede et installation de regazeification du gaz naturel liquefie avec recuperation de chaleur

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3018634A (en) * 1958-04-11 1962-01-30 Phillips Petroleum Co Method and apparatus for vaporizing liquefied gases and obtaining power
US3068659A (en) * 1960-08-25 1962-12-18 Conch Int Methane Ltd Heating cold fluids with production of energy
US3479832A (en) * 1967-11-17 1969-11-25 Exxon Research Engineering Co Process for vaporizing liquefied natural gas
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
US6945049B2 (en) 2002-10-04 2005-09-20 Hamworthy Kse A.S. Regasification system and method
WO2007039480A1 (fr) * 2005-09-21 2007-04-12 Exmar Procede et installation de regazeification du gaz naturel liquefie avec recuperation de chaleur

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