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WO2010053483A1 - Simultaneous regasification of liquefied natural gas and desalination - Google Patents

Simultaneous regasification of liquefied natural gas and desalination Download PDF

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Publication number
WO2010053483A1
WO2010053483A1 PCT/US2008/082585 US2008082585W WO2010053483A1 WO 2010053483 A1 WO2010053483 A1 WO 2010053483A1 US 2008082585 W US2008082585 W US 2008082585W WO 2010053483 A1 WO2010053483 A1 WO 2010053483A1
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WO
WIPO (PCT)
Prior art keywords
ice
natural gas
stream
heat exchanger
passing
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
PCT/US2008/082585
Other languages
French (fr)
Inventor
Kurt M. Vanden Bussche
Blaise J. Arena
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Honeywell UOP LLC
Original Assignee
UOP LLC
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Filing date
Publication date
Application filed by UOP LLC filed Critical UOP LLC
Priority to PCT/US2008/082585 priority Critical patent/WO2010053483A1/en
Publication of WO2010053483A1 publication Critical patent/WO2010053483A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/22—Treatment of water, waste water, or sewage by freezing
    • 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
    • F17C5/00—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures
    • F17C5/06—Methods or apparatus for filling containers with liquefied, solidified, or compressed gases under pressures for filling with compressed gases
    • 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
    • F17C9/04—Recovery of thermal energy
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • 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
    • 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
    • F17C2225/0146—Two-phase
    • F17C2225/0153—Liquefied gas, e.g. LPG, GPL
    • 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
    • F17C2227/0142—Pumps with specified pump type, e.g. piston or impulsive type
    • 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
    • F17C2227/0311—Air heating
    • 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
    • F17C2227/0367—Localisation of heat exchange
    • F17C2227/0388—Localisation of heat exchange separate
    • 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
    • F17C2265/01—Purifying the fluid
    • F17C2265/015—Purifying the fluid by separating
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination

Definitions

  • the present invention relates to a process for the desalination of seawater.
  • a more common method of freeze desalination involves the use of vacuum freezing of water by spraying cooled seawater into an evacuated chamber creating small ice crystals that are subsequently separated from the brine and then melted.
  • An example of this process is shown in US 3,724,229, issued on April 3, 1973. This process has the significant drawback of working with systems under vacuum.
  • Improvements in the process of freeze desalination can improve access to fresh water, while saving costs.
  • the invention is a process for desalination of water using the freezing capabilities of liquefied natural gas during the regasification process.
  • the liquefied natural gas is passed through one side of a heat exchanger with seawater passed through the other side of the heat exchanger.
  • An ice-brine mixture is formed on the seawater side, while the natural gas is vaporized on the natural gas side of the exchanger.
  • the ice-brine mixture is withdrawn from the heat exchanger and ice is separated from the mixture. The ice is subsequently melted and recovered as fresh water.
  • Figure 1 is a first embodiment of the invention; and [0010] Figure 2 is an alternate embodiment of the invention.
  • Liquefied natural gas is transported around the world as a means to move natural gas from regions where natural gas exists to regions where the natural gas is needed. After shipment, the LNG is regasified. The 'cold' in the LNG can be used to provide fresh water through the process of freeze desalination
  • the present invention provides a process and apparatus for taking advantage of the energy transfer in the process of regasifying LNG.
  • the process for desalinating water with the regasification of LNG includes passing the LNG and seawater through a heat exchanger 10.
  • the LNG is passed through one side 12 and the seawater is passed through the other side 14 of the heat exchanger 10 keeping the LNG and seawater separate while gasifying the LNG and freezing the seawater.
  • As the seawater freezes the salt in the sea water is rejected and an ice-brine mixture is formed.
  • an agitator 16 is included in the seawater side of the heat exchanger 10 to keep the ice-brine mixture as a mixture of small ice particles in the brine and to inhibit the formation of a large ice block.
  • the ice-brine mixture is passed to a separator 20, where the ice is separated from the ice-brine mixture.
  • the separator 20 comprises a tank that allows the ice-brine mixture to settle with the ice rising to the top and the brine sinking to the bottom of the tank.
  • any water having dissolved salts can be used, and the invention is not restricted to seawater.
  • the ice is withdrawn from the separator 20 and passed to a wash unit 30, where the ice is rinsed with fresh water to remove residual salt on the surface of the ice.
  • the ice is subsequently passed to a second heat exchange unit 40, or melting unit, wherein the ice is melted.
  • the rinse water from the wash unit 30 can be passed to first heat exchanger 10 through mixing with the seawater that is directed to the first heat exchanger 10.
  • the second heat exchanger 40 uses a saltwater stream flowing through the hot side to melt the ice, and providing fresh water to be drawn off.
  • the first embodiment includes a natural gas liquids separation unit 50.
  • the regasified natural gas is passed from the first heat exchanger 10 to the separation unit 50.
  • the separation unit 50 is for removing ethane, propane, and other hydrocarbons from the natural gas to meet the specifications of natural gas to be fed into natural gas pipelines.
  • the separation unit 50 comprises a fractionation column, wherein the regasified natural gas is fed to the fractionation column.
  • a portion of the liquefied natural gas is supplied to provide the necessary cooling for vapor passing through the overhead condenser.
  • Seawater is supplied to the boiler to provide the necessary heat to vaporize a portion of the condensed liquids at the bottom of the column.
  • the process comprises pressurizing the liquefied natural gas to a pressure sufficient for injecting the regasified natural gas into a natural gas pipeline.
  • pressurization include optimization for the heat exchanger 10, and the natural gas separation unit 50.
  • Pressurization is preferably to a pressure greater than 3MPa (435 psia), and more preferably to a pressure greater than 6.5 Mpa (940 psia). Pressurization can be obtained during the pumping of the LNG through a feed pump 60 to the heat exchanger 10.
  • This apparatus and process involves no mixing of the natural gas with the water, nor does it require an intermediate hydrocarbon stream.
  • the process and apparatus provide for freezing of seawater to produce ice from liquefied natural gas in a periodic process.
  • the process comprises alternating the flowing LNG and seawater through a heat exchanger to form ice, and then draining residual seawater and flowing a warm fluid through the heat exchanger to melt the ice and produce the fresh water.
  • the process of the second embodiment is shown in Figure 2.
  • the process includes flowing a portion of LNG through the first side of a heat exchanger 100, and flowing seawater through the second side of the heat exchanger 100. When sufficient ice is formed in the heat exchanger 100, the flow of LNG is stopped and the flow of seawater is stopped and any residual seawater is drained from the second side of the heat exchanger 100.
  • a hot combusted flue gas is then passed through the first side of the heat exchanger 100, providing heat to melt the ice, and fresh water from the melted ice is drained from the second side of the heat exchanger 100. After draining the fresh water, the process is repeated. It is contemplated that this process will use multiple heat exchangers 100, and the flow of LNG and flue gas will be passed through the heat exchangers 100 in a sequential manner to provide for continuous production of fresh water.
  • the process further comprises passing a second portion of the LNG stream to a combustor 110, passing a compressed air stream to the combustor 110 and combusting the natural gas to produce a hot combusted gas stream.
  • the hot combusted gas stream is passed to a turbine expander 120 thereby generating power with a hot combusted flue gas stream leaving the turbine expander 120.
  • the turbine expander 120 generates power, and is also used to operate a compressor 130.
  • the compressor 130 compresses an air stream which is fed to the combustor 110.
  • a heat exchanger 140 is preferred to heat the second portion of the LNG stream, and is heated with the hot combusted flue gas stream from the turbine expander 120.
  • the heat exchanger 140 is sized to vaporize the LNG stream, such that the combustor 110 receives a regasified natural gas stream.
  • the hot combusted flue gas stream is subsequently directed to the heat exchangers 100 for melting the ice that was frozen during an earlier step in the process.
  • Operation of the compressor 130 is more efficient if the air to be compressed has been cooled first.
  • the air is cooled by passing LNG through a heat exchanger 150 prior to passing the LNG to the heat exchangers 100 used for regasifying the natural gas. Air passed through the heat exchanger 150 is then passed to the compressor 130 for the production of compressed air.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

A process and apparatus is presented for the desalination of water by freezing seawater. The process is integrated into a liquefied natural gas regasification system.

Description

SIMULTANEOUS REGASIFICATION OF LIQUEFIED NATURAL GAS AND DESALINATION
FIELD OF THE INVENTION
[0001] The present invention relates to a process for the desalination of seawater.
BACKGROUND OF THE INVENTION
[0002] The production of fresh water from sea water is produced from an evaporation of the water from the salt water and then condensing the purified water vapor. Another commercial method is the use of reverse osmosis. Fresh water also, can be produced by using a freezing process that separates the water as it freezes from the salt water. [0003] Desalination of water by freezing has been studied, but not commercialized. One such desalination process using the cold temperatures of liquefied natural gas (LNG) is shown in US 3,675,436, issued on July 11, 1972. This process uses LNG to cool butane to a liquid and sprays the liquid butane into a crystallizer with seawater to form a butane-ice-brine mixture. The drawback of this process is the use of an intermediate heat exchange material, and the direct mixing of the butane with the seawater to form the butane-ice-brine mixture. This requires further processing to remove and recover the butane from the desalinated water and from the brine.
[0004] Even when there is no direct contacting of a cold hydrocarbon stream with seawater, the use of LNG for freezing seawater involves the liquefaction of a higher hydrocarbon stream for subsequent use in freezing seawater, as shown in US 3,892,103, issued on July 1, 1975. The use of an intermediate heat transfer medium requires more equipment, and entails greater losses, or lower efficiency in the process of freeze desalination.
[0005] A more common method of freeze desalination involves the use of vacuum freezing of water by spraying cooled seawater into an evacuated chamber creating small ice crystals that are subsequently separated from the brine and then melted. An example of this process is shown in US 3,724,229, issued on April 3, 1973. This process has the significant drawback of working with systems under vacuum. [0006] Improvements in the process of freeze desalination can improve access to fresh water, while saving costs.
SUMMARY OF THE INVENTION
[0007] The invention is a process for desalination of water using the freezing capabilities of liquefied natural gas during the regasification process. In one embodiment, the liquefied natural gas is passed through one side of a heat exchanger with seawater passed through the other side of the heat exchanger. An ice-brine mixture is formed on the seawater side, while the natural gas is vaporized on the natural gas side of the exchanger. The ice-brine mixture is withdrawn from the heat exchanger and ice is separated from the mixture. The ice is subsequently melted and recovered as fresh water.
[0008] Additional objects, embodiments and details of this invention can be obtained from the following detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 is a first embodiment of the invention; and [0010] Figure 2 is an alternate embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0011] Liquefied natural gas is transported around the world as a means to move natural gas from regions where natural gas exists to regions where the natural gas is needed. After shipment, the LNG is regasified. The 'cold' in the LNG can be used to provide fresh water through the process of freeze desalination
[0012] The present invention provides a process and apparatus for taking advantage of the energy transfer in the process of regasifying LNG. In one embodiment, as shown in Figure 1 , the process for desalinating water with the regasification of LNG includes passing the LNG and seawater through a heat exchanger 10. The LNG is passed through one side 12 and the seawater is passed through the other side 14 of the heat exchanger 10 keeping the LNG and seawater separate while gasifying the LNG and freezing the seawater. As the seawater freezes the salt in the sea water is rejected and an ice-brine mixture is formed. In one embodiment, an agitator 16 is included in the seawater side of the heat exchanger 10 to keep the ice-brine mixture as a mixture of small ice particles in the brine and to inhibit the formation of a large ice block. The ice-brine mixture is passed to a separator 20, where the ice is separated from the ice-brine mixture. The separator 20 comprises a tank that allows the ice-brine mixture to settle with the ice rising to the top and the brine sinking to the bottom of the tank. In the context of this invention, any water having dissolved salts can be used, and the invention is not restricted to seawater.
[0013] The ice is withdrawn from the separator 20 and passed to a wash unit 30, where the ice is rinsed with fresh water to remove residual salt on the surface of the ice. The ice is subsequently passed to a second heat exchange unit 40, or melting unit, wherein the ice is melted. The rinse water from the wash unit 30 can be passed to first heat exchanger 10 through mixing with the seawater that is directed to the first heat exchanger 10. The second heat exchanger 40 uses a saltwater stream flowing through the hot side to melt the ice, and providing fresh water to be drawn off.
[0014] In an alternative, the first embodiment includes a natural gas liquids separation unit 50. The regasified natural gas is passed from the first heat exchanger 10 to the separation unit 50. The separation unit 50 is for removing ethane, propane, and other hydrocarbons from the natural gas to meet the specifications of natural gas to be fed into natural gas pipelines. In one embodiment, the separation unit 50 comprises a fractionation column, wherein the regasified natural gas is fed to the fractionation column. A portion of the liquefied natural gas is supplied to provide the necessary cooling for vapor passing through the overhead condenser. Seawater is supplied to the boiler to provide the necessary heat to vaporize a portion of the condensed liquids at the bottom of the column. [0015] hi one embodiment, the process comprises pressurizing the liquefied natural gas to a pressure sufficient for injecting the regasified natural gas into a natural gas pipeline. Considerations for pressurization include optimization for the heat exchanger 10, and the natural gas separation unit 50. Pressurization is preferably to a pressure greater than 3MPa (435 psia), and more preferably to a pressure greater than 6.5 Mpa (940 psia). Pressurization can be obtained during the pumping of the LNG through a feed pump 60 to the heat exchanger 10. [0016] This apparatus and process involves no mixing of the natural gas with the water, nor does it require an intermediate hydrocarbon stream. Without the mixing of a hydrocarbon stream with the seawater, there is no need to have a separator to remove hydrocarbons from the fresh water, or from the brine, thereby saving equipment and operation costs. In addition, by keeping the natural gas separate from the seawater, water is not added to the natural gas and does not need to be later removed.
[0017] In a second embodiment, the process and apparatus provide for freezing of seawater to produce ice from liquefied natural gas in a periodic process. The process comprises alternating the flowing LNG and seawater through a heat exchanger to form ice, and then draining residual seawater and flowing a warm fluid through the heat exchanger to melt the ice and produce the fresh water. The process of the second embodiment is shown in Figure 2. The process includes flowing a portion of LNG through the first side of a heat exchanger 100, and flowing seawater through the second side of the heat exchanger 100. When sufficient ice is formed in the heat exchanger 100, the flow of LNG is stopped and the flow of seawater is stopped and any residual seawater is drained from the second side of the heat exchanger 100. A hot combusted flue gas is then passed through the first side of the heat exchanger 100, providing heat to melt the ice, and fresh water from the melted ice is drained from the second side of the heat exchanger 100. After draining the fresh water, the process is repeated. It is contemplated that this process will use multiple heat exchangers 100, and the flow of LNG and flue gas will be passed through the heat exchangers 100 in a sequential manner to provide for continuous production of fresh water.
[0018] In an alternate embodiment, the process further comprises passing a second portion of the LNG stream to a combustor 110, passing a compressed air stream to the combustor 110 and combusting the natural gas to produce a hot combusted gas stream. The hot combusted gas stream is passed to a turbine expander 120 thereby generating power with a hot combusted flue gas stream leaving the turbine expander 120. The turbine expander 120 generates power, and is also used to operate a compressor 130. The compressor 130 compresses an air stream which is fed to the combustor 110.
[0019] A heat exchanger 140 is preferred to heat the second portion of the LNG stream, and is heated with the hot combusted flue gas stream from the turbine expander 120. The heat exchanger 140 is sized to vaporize the LNG stream, such that the combustor 110 receives a regasified natural gas stream. The hot combusted flue gas stream is subsequently directed to the heat exchangers 100 for melting the ice that was frozen during an earlier step in the process.
[0020] Operation of the compressor 130 is more efficient if the air to be compressed has been cooled first. The air is cooled by passing LNG through a heat exchanger 150 prior to passing the LNG to the heat exchangers 100 used for regasifying the natural gas. Air passed through the heat exchanger 150 is then passed to the compressor 130 for the production of compressed air.
[0021] While the invention has been described with what are presently considered the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but it is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims.

Claims

CLAIMS:
1. A process for desalination of water comprising: continuously passing liquefied natural gas through a first side of a heat exchanger; passing salt water through a second side of the heat exchanger; forming an ice-brine mixture in the second side of the heat exchanger and forming a vaporized natural gas stream on the first side of the heat exchanger; and separating the ice from the ice-brine mixture, and drawing off a first stream comprising an ice enriched mixture and a second stream comprising a first brine stream.
2. The process of claim 1 further comprising: passing the first stream comprising ice to a wash column; passing water over the ice from the first stream forming a washed-ice stream and a second brine stream; drawing off the washed-ice from the wash column; and drawing off the second brine stream.
3. The process of claim 2 further comprising: passing the washed-ice to a melter having a first side for passing the washed-ice through and a second side for passing a salt water stream through; passing the salt water stream through the second side; and drawing off a water stream from the melted washed-ice.
4. The process of claim 3 wherein the salt water stream from the melter is passed to the second side of the heat exchanger.
5. The process of claim 1 further comprising passing the vaporized natural gas stream to a separation unit for separating natural gas liquids from the vaporized natural gas stream.
6. The process of claim 1 further comprising agitating the ice-brine mixture in the second side of the heat exchanger.
7. The process of claim 1 further comprising pressurizing the liquefied natural gas to a pressure greater than 3 MPa (435 psia) thereby creating a pressurized liquid natural gas stream to pass through the first side of the heat exchanger.
8. The process of claim 7 wherein the liquefied natural gas is pressurized to a pressure greater than 6.5 MPa (940 psia) thereby creating a pressurized liquid natural gas stream to pass through the first side of the heat exchanger.
PCT/US2008/082585 2008-11-06 2008-11-06 Simultaneous regasification of liquefied natural gas and desalination Ceased WO2010053483A1 (en)

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WO2012104787A1 (en) * 2011-01-31 2012-08-09 I.D.E. Technologies Ltd. Apparatus and method for freeze desalination
CN105800716A (en) * 2016-04-01 2016-07-27 南京航空航天大学 Sea water desalination system and method achieved by means of condensate waste heat of refrigeration system
US20170008778A1 (en) * 2015-07-08 2017-01-12 King Abdulaziz University Freezing desalination module
US10246345B2 (en) 2015-12-30 2019-04-02 General Electric Company Water desalination system and method for fast cooling saline water using turbines
CN110294505A (en) * 2018-03-23 2019-10-01 中国石油化工股份有限公司 Freezing seawater desalination system based on solar energy and LNG cold energy

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JPH08261611A (en) * 1995-03-23 1996-10-11 Mitsui Eng & Shipbuild Co Ltd Combined heat supply and desalination system
JPH0952083A (en) * 1995-08-16 1997-02-25 Nkk Corp Seawater desalination equipment

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US4283211A (en) * 1979-04-09 1981-08-11 Levor, Incorporated Power generation by exchange of latent heats of phase transition
JPH08261611A (en) * 1995-03-23 1996-10-11 Mitsui Eng & Shipbuild Co Ltd Combined heat supply and desalination system
US5553456A (en) * 1995-05-17 1996-09-10 Ramco, Inc. Clathrate freeze desalination apparatus and method
JPH0952083A (en) * 1995-08-16 1997-02-25 Nkk Corp Seawater desalination equipment

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2012104787A1 (en) * 2011-01-31 2012-08-09 I.D.E. Technologies Ltd. Apparatus and method for freeze desalination
CN103459324A (en) * 2011-01-31 2013-12-18 I.D.E.技术有限公司 Apparatus and method for freeze desalination
JP2014508268A (en) * 2011-01-31 2014-04-03 アイ・ディ・イー・テクノロジーズ・リミテッド Freezing and desalting apparatus and freezing and desalting method
CN103459324B (en) * 2011-01-31 2016-08-24 I.D.E.技术有限公司 Apparatus and method for freeze desalination
US20170008778A1 (en) * 2015-07-08 2017-01-12 King Abdulaziz University Freezing desalination module
US10246345B2 (en) 2015-12-30 2019-04-02 General Electric Company Water desalination system and method for fast cooling saline water using turbines
CN105800716A (en) * 2016-04-01 2016-07-27 南京航空航天大学 Sea water desalination system and method achieved by means of condensate waste heat of refrigeration system
CN110294505A (en) * 2018-03-23 2019-10-01 中国石油化工股份有限公司 Freezing seawater desalination system based on solar energy and LNG cold energy

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