US20090139263A1 - Thermosyphon reboiler for the denitrogenation of liquid natural gas - Google Patents

Thermosyphon reboiler for the denitrogenation of liquid natural gas Download PDF

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US20090139263A1
US20090139263A1 US11/949,828 US94982807A US2009139263A1 US 20090139263 A1 US20090139263 A1 US 20090139263A1 US 94982807 A US94982807 A US 94982807A US 2009139263 A1 US2009139263 A1 US 2009139263A1
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stream
column
lng
nitrogen
reboiler
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US11/949,828
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English (en)
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Adam Adrian Brostow
Mark Julian Roberts
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Air Products and Chemicals Inc
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Air Products and Chemicals Inc
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Priority to US11/949,828 priority Critical patent/US20090139263A1/en
Assigned to AIR PRODUCTS AND CHEMICALS, INC. reassignment AIR PRODUCTS AND CHEMICALS, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ROBERTS, MARK JULIAN, BROSTOW, ADAM ADRIAN
Priority to EP08856437A priority patent/EP2215415A2/fr
Priority to JP2010536542A priority patent/JP2011517322A/ja
Priority to CN2008801189441A priority patent/CN102439384A/zh
Priority to AU2008332869A priority patent/AU2008332869A1/en
Priority to PCT/IB2008/003303 priority patent/WO2009071977A2/fr
Priority to RU2010127280/06A priority patent/RU2010127280A/ru
Publication of US20090139263A1 publication Critical patent/US20090139263A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0209—Natural gas or substitute natural gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0257—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of nitrogen
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/70—Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/04—Recovery of liquid products
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
    • F25J2240/30—Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/02—Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/40—Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.

Definitions

  • This invention relates to processes for the separation of nitrogen from a liquid natural gas stream comprising nitrogen, methane, and possibly heavier hydrocarbons.
  • Crude natural gas is often liquefied to enable storage of larger quantities in the form of liquid natural gas (LNG). Because natural gas may be contaminated with nitrogen, nitrogen is advantageously removed from LNG to produce a nitrogen-diminished LNG product that will meet desired product specifications. Several methods of effectuating nitrogen removal from LNG have been disclosed in the prior art.
  • One simple method for separating nitrogen from a LNG stream is to isentropically expand the crude LNG stream in a turbine and then inject the stream into a flash separator.
  • the liquid product removed from the flash separator will contain less nitrogen than the crude LNG stream, whereas the vapor product will contain a higher proportion of nitrogen.
  • a liquid stream is withdrawn and passed through the heat exchanger to cool the feed and then reinjected into the column at a level below that at which it had been withdrawn, to provide boilup to the column.
  • the passage of the withdrawn stream through the heat exchanger provides an additional equilibrium stage of separation.
  • a similar method for separating nitrogen from an LNG stream replaces the turbine driven dynamic decompression with a valve for static decompression, such that the expansion takes place isenthalpically rather than isentropically.
  • the use of the isentropic expansion in the process of the '165 patent allegedly permits greater methane recovery.
  • the sump of the column is divided by a baffle, one side of which is filled with liquid from the lowest tray of the column.
  • This bottoms liquid is withdrawn and at least partially vaporized in the heat exchanger, while condensing the vapor stream from the phase separator, and returned to the column as a reflux stream to provide boilup.
  • the liquid remaining in the reflux stream falls to the other side of the baffle in the sump.
  • This liquid reflux is then removed as a nitrogen-diminished product stream, pumped to a higher pressure, warmed and vaporized, and then dynamically expanded to reduce the temperature and pressure of the vapor product. Similar to the reboiler heat exchange of the '165 patent, the reflux of the bottoms liquid serves as an additional equilibrium stage of separation.
  • a disadvantage of these prior art nitrogen separation methods is that they each require that the entire liquid flow off of one tray be recycled through the reboiler. Another disadvantage is that they each are completely dependent upon liquid head in the column to drive the heat exchangers. These characteristics limit the flexibility of these methods, as the entire process must be designed to accommodate this large amount of flow. A further disadvantage associated with the prior art is that the processes tend to require a large area for the placement of equipment.
  • the present invention provides an improved process for the denitrogenation of an LNG stream contaminated by nitrogen. This process allows for economic benefits by permitting a greater flexibility in the process design and eliminating the requirement of some equipment.
  • a crude LNG stream comprising between about 1% and 10% nitrogen, and the remainder methane and heavier hydrocarbons, is expanded in a means for expansion, and cooled in a thermosyphon reboiler.
  • the resultant crude LNG stream is introduced into a nitrogen rejection column, wherein the nitrogen content of the LNG is reduced as the liquid flows down the column.
  • a nitrogen-enriched vapor stream is withdrawn from the top of the column, and a first nitrogen-diminished liquid stream is withdrawn from the bottom of the column. This nitrogen-diminished liquid stream may be recovered as a LNG product.
  • a second nitrogen-diminished liquid stream is also withdrawn from the bottom of the column.
  • This second stream is passed through the thermosyphon reboiler, thus cooling the crude LNG stream, and at least partially vaporizing the second stream.
  • the partially vaporized second stream is reinjected into the column at a level above the level of withdrawal of the nitrogen-diminished bottoms LNG stream and below the level of introduction of the crude LNG feed stream to provide column boilup.
  • the first and second nitrogen-diminished liquid streams are withdrawn from the column together, through the same conduit, and are separated after withdrawal.
  • thermosyphon reboiler is placed within the sump of the column so that only one nitrogen-diminished liquid stream is withdrawn from the column.
  • the initial crude LNG stream is expanded in a dense fluid expander, which may be placed either upstream or downstream of the thermosyphon reboiler.
  • a valve may also be placed immediately upstream of the nitrogen rejection column, such that the crude LNG stream is throttled through the valve prior to injection into the column.
  • FIG. 1 is a schematic diagram illustrating a first process for removing nitrogen from an LNG stream in accordance with one embodiment of the present invention.
  • FIG. 2 is a schematic diagram illustrating a second process for removing nitrogen from an LNG stream in accordance with one embodiment of the present invention.
  • the present invention achieves flexibility of design and process economic advantages in an LNG denitrogenation operation by using, in part, a thermosyphon reboiler, the flow through which is driven by the density difference between the input and output streams in conjunction with the liquid head of the column, rather than solely by the liquid head of the column, thus permitting a greater flexibility in the overall process design.
  • the present invention also permits variability in the amount of fluid flow through the reboiler which further increases process flexibility.
  • the processes according to the present invention permit the elimination of some equipment, including collection trays, nozzles, and large reboilers, that would otherwise be required of prior art processes, and can therefore achieve the additional advantages of saving both cost and space.
  • thermodynamic inefficiency As will be clarified in the following description, achieving this flexibility, while allowing for the removal of process equipment and the maintenance of output levels and energy requirements, involves the introduction of a small thermodynamic inefficiency.
  • the flexibility and cost and space savings afforded by the present invention more than compensate for this thermodynamic inefficiency, especially given the ease and low expense with which it may be remedied.
  • nitrogen-enriched stream is used herein to mean a stream containing a higher concentration of nitrogen when compared with an initial feed stream.
  • nitrogen-diminished stream is used herein to mean a stream containing a lower concentration of nitrogen when compared with an initial feed stream.
  • below is used herein to mean at a position of lesser height, i.e., closer to the ground.
  • FIG. 1 A preferred embodiment of the invention will now be described in detail with reference to FIG. 1 .
  • the following embodiments are not intended to limit the scope of the invention, and it should be recognized by those skilled in the art that there are other embodiments within the scope of the claims.
  • high-pressure LNG stream 100 is expanded via means for expanding the LNG stream 102 to produce lower-pressure LNG stream 104 .
  • the expansion is preferably performed isentropically, and the means for expanding the LNG stream is preferably a dense fluid expander (also known as a hydraulic turbine), but may also be a valve or other known means for expanding a fluid.
  • Lower-pressure LNG stream 104 is cooled in thermosyphon reboiler 106 to produce cooled, expanded LNG stream 108 .
  • Nitrogen rejection column 150 is preferably a tray column, but may be a packed column or any other mass transfer device suitable for fractionation.
  • a nitrogen-enriched vapor stream 130 is withdrawn from the top of column 150 .
  • nitrogen-enriched it is herein understood to mean containing a higher concentration of nitrogen than that of high-pressure LNG stream 100 , and will typically contain more than about 30% N 2 and less than about 70% methane.
  • a first nitrogen-diminished liquid stream 110 is withdrawn from the bottom of column 150 and may be recovered as a product stream.
  • nitrogen-diminished it is herein understood to mean containing a lower concentration of nitrogen than that of high-pressure LNG stream 100 .
  • a second nitrogen-diminished liquid stream, reboiler stream 112 is also withdrawn from the bottom of column 150 .
  • the flow rate of reboiler stream 112 is typically between about 15% and about 100% of the flow rate of liquid stream 110 .
  • Reboiler stream 112 is at least partially vaporized in thermosyphon reboiler 106 to produce partially vaporized reboiler stream 114 , which is then injected into the bottom of column 150 , below the lowest tray in the case of a tray column, or below the packing material in the case of a packed column, to provide boilup.
  • the flow rate of reboiler stream 112 may be adjusted as necessary to provide different recirculation rates (i.e., the ratio of the outlet liquid flow to vapor flow).
  • the means for expanding the LNG stream 102 may be placed downstream of thermosyphon reboiler 106 . In this manner, high-pressure stream 100 is cooled in thermosyphon reboiler 106 prior to undergoing expansion in the means for expanding the LNG stream 102 .
  • nitrogen-diminished liquid stream 110 and reboiler stream 112 may be withdrawn from the bottom of column 150 as a single stream through a single conduit. According to this embodiment, nitrogen-diminished liquid stream 110 would then be separated from the combined stream and optionally recovered as a product stream. The remaining stream would be reboiler stream 112 , and would proceed through the thermosyphon reboiler as before.
  • valve 109 is optional, and, in the alternative, cooled LNG stream 108 can be directly injected into nitrogen rejection column 150 .
  • the means for expanding the LNG stream 102 is preferably a two-phase dense fluid expander.
  • a particularly preferred embodiment is provided wherein a crude LNG stream 100 is substantially isentropically expanded in a dense fluid expander 102 and cooled in a thermosyphon reboiler 106 .
  • This cooled, expanded LNG stream 108 is substantially isenthalpically expanded through valve 109 and injected into a nitrogen rejection column 150 .
  • rising vapor strips the nitrogen from the falling liquid, and a nitrogen-enriched stream 130 is withdrawn from the top of the column.
  • a nitrogen-diminished liquid stream 110 is withdrawn from the bottom of the column and may be recovered as a product stream.
  • Reboiler stream 112 is also withdrawn from the bottom of column 150 .
  • Reboiler stream 112 is at least partially vaporized in thermosyphon reboiler 106 to produce partially vaporized reboiler stream 114 , which is then injected into the bottom of column 150 , below the lowest tray in the case of a tray column, or below the packing material in the case of a packed column, to provide boilup.
  • the recirculation rate of the reboiler 106 is preferably at least about 4.
  • the liquid portion of the partially vaporized reboiler stream 114 mixes with the liquid from the lowest column stage upon reinjection into column 150 such that the nitrogen-diminished liquid stream 110 is not exclusively the liquid from the bottom stage of the rejection column 150 , or from the thermosyphon reboiler 106 , but rather a mixture of both.
  • this can easily and cheaply be compensated for by the addition of a stage or stages to the nitrogen rejection column 150 .
  • the recirculation rate for the thermosyphon reboiler may be any desired rate determined by the geometry of the heat exchanger, and therefore, the ratio of the flow rate of the reboiler stream 112 to the flow rate of the nitrogen-diminished liquid stream 110 can be flexibly defined, and may be easily optimized for the particular process.
  • FIG. 2 An alternative embodiment is illustrated in FIG. 2 .
  • high-pressure LNG stream 100 is expanded via means for expanding the LNG stream 102 to produce lower-pressure LNG stream 104 ; lower-pressure LNG stream 104 is cooled in thermosyphon reboiler 106 to produce cooled, expanded LNG stream 108 ; and cooled, expanded LNG stream 108 is then substantially isenthalpically expanded through valve 109 and injected into nitrogen rejection column 150 .
  • the thermosyphon reboiler 106 is placed within the sump of the column 150 , such that the top of the reboiler 106 is above the height of the liquid.
  • thermosyphon reboiler 106 Liquid within the sump is passed through the thermosyphon reboiler 106 by means of a pressure gradient established within the reboiler 106 , which forces liquid into the bottom of the reboiler 106 and expels liquid and vapor from the top of the reboiler 106 , at a ratio defined by the recirculation rate.
  • This orientation eliminates the need to withdraw a reboiler stream from, and reinject a reboiler stream into, the column 150 .
  • a nitrogen-enriched vapor stream 130 is withdrawn from the top of column 150 .
  • a nitrogen-diminished liquid stream 110 is withdraw from the bottom of the column and may be recovered as product.
  • the recirculation rate may be adjusted to any value to provide the desired amount of boilup.
  • the present invention provides a significant improvement in the adaptability and flexibility of a LNG denitrogenation process through the implementation of a hydraulically different process from those of the prior art.
  • a thermosyphon reboiler 106 By permitting a thermosyphon reboiler 106 to assist in driving the flow of the reboiler streams 112 / 114 rather than relying exclusively on the column head, and by allowing variability in the selection of the design recirculation rate, greater flexibility of design is permitted. This flexibility can lead to a smaller capital expense at the remediable cost of a minor thermodynamic loss.
  • the reboiler and piping requirements associated with the process can be adjusted to minimize capital expenditures.
  • the use of a thermosyphon rebolier for the denitrogenation of an LNG stream can also lead to improvements in the controllability of the overall process.
  • thermosyphon process of the present invention there is no need for a liquid collection tray below the distillation section of the column, which would be required were all of the liquid coming off of a tray to pass through a reboiler. Additionally, when the internal thermosyphon process of the present invention is used, the nozzles required for withdrawal of the recycle stream are also eliminated. Moreover, by placing the thermosyphon reboiler inside of the column, valuable space can be saved because there is no longer a need to dedicate space outside of the column to the reboiler and associated piping.
  • thermosyphon reboiler When the external thermosyphon reboiler is used, space may still be saved, due to the simplified piping, smaller required heat transfer surface area, and small footprint associated with thermosyphon reboilers as compared to other reboiler types.
  • process simulations of the entire natural gas liquefaction process were run, using an ASPEN process simulator, comparing two embodiments of the invention (“current process”) with the process disclosed in the '165 patent.
  • the comparison basis is an equal LNG production and a satisfied fuel balance (the amount of LNG product flash required to drive a gas turbine driving the process).
  • the respective reference numerals used in this example refer to FIG. 1 , as described above, and the '165 patent (see, e.g., FIG. 1 therein).
  • low pressure LNG stream 104 following expansion in dense fluid expander 102 , low pressure LNG stream 104 , at a flow rate of 125,470 lbmol/hr, a pressure of 71.78 psia, a temperature of ⁇ 242.9° F., and containing 2.96% N 2 , 95.47% methane, 1.10% C 2 hydrocarbons, and 0.47% heavier hydrocarbons, is cooled in thermosyphon reboiler 106 to produce cooled, expanded LNG stream 108 at a temperature of ⁇ 252.5° F. and a pressure of 64.52 psia.
  • Cooled, expanded stream 108 is throttled through valve 109 and introduced into a denitrogenation column 150 comprising 6 trays, at a pressure of 18 psia.
  • An overhead vapor stream 130 is withdrawn from the top of the column 150 at a flow rate of 8,141 lbmol/hr, and contains 31.06% N 2 , 68.94% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia and a temperature of ⁇ 261.9° F.
  • Bottoms stream 110 is withdrawn from the column 150 at a flowrate of 117,329 lbmol/hr, a pressure of 19.45 psia, a temperature of ⁇ 256.8° F., and contains 1.01% N 2 , 97.31% methane, 1.17% C 2 hydrocarbons, and 0.51% heavier hydrocarbons.
  • a reboiler stream 112 is withdrawn from the column 150 at a flow rate of 17,704 lbmol/hr, a temperature of ⁇ 256.8° F., a pressure of 19.74 psia, and contains 1.01% N 2 , 97.31% methane, 1.17% C 2 hydrocarbons, and 0.51% heavier hydrocarbons.
  • the reboiler stream 112 is passed through the thermosyphon reboiler 106 , where it is partially vaporized to produce vaporized reboiler stream 114 .
  • Vaporized reboiler stream 114 which is at a temperature of ⁇ 252.7° F., a pressure of 19.45 psia, and has a vapor fraction of 25.3%, is injected below the bottom tray of column 150 to provide boilup. This liquefaction process requires approximately 229 MW of power.
  • low pressure LNG stream 104 following expansion in dense fluid expander 102 , low pressure LNG stream 104 , at a flow rate of 125,474 lbmol/hr, a pressure of 71.84 psia, a temperature of ⁇ 242.9° F., and containing 2.96% N 2 , 95.47% methane, 1.10% C 2 hydrocarbons, and 0.47% heavier hydrocarbons, is cooled in thermosyphon reboiler 106 to produce cooled, expanded LNG stream 108 at a temperature of ⁇ 253.1° F. and a pressure of 64.59 psia.
  • Cooled, expanded stream 108 is throttled through valve 109 and introduced into a denitrogenation column 150 comprising 6 trays, at a pressure of 18 psia.
  • An overhead vapor stream 130 is withdrawn from the top of the column 150 at a flow rate of 8,121 lbmol/hr, and contains 31.54% N 2 , 68.46% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia and a temperature of ⁇ 262.0° F.
  • Bottoms stream 110 is withdrawn from the column 150 at a flowrate of 117,353 lbmol/hr, a pressure of 19.45 psia, a temperature of ⁇ 256.7° F., and contains 0.98% N 2 , 97.34% methane, 1.17% C 2 hydrocarbons, and 0.51% heavier hydrocarbons.
  • a reboiler stream 112 is withdrawn from the column 150 at a flow rate of 117,353 lbmol/hr, a temperature of ⁇ 256.7° F., a pressure of 19.74 psia, and contains 0.98% N 2 , 97.34% methane, 1.17% C 2 hydrocarbons, and 0.51% heavier hydrocarbons.
  • the reboiler stream 112 is passed through the thermosyphon reboiler 106 , where it is partially vaporized to produce vaporized reboiler stream 114 .
  • Vaporized reboiler stream 114 which is at a temperature of ⁇ 254.8° F., a pressure of 19.45 psia, and has a vapor fraction of 3.7%, is injected below the bottom tray of column 150 to provide boilup. This liquefaction process also requires approximately 229 MW of power.
  • An overhead vapor stream 10 is withdrawn from the top of the column 5 at a flow rate of 8,122 lbmol/hr, and contains 31.17% N 2 , 68.83% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia and a temperature of ⁇ 261.9° F.
  • Bottoms stream 11 is withdrawn from the column 5 at a flowrate of 117,329 lbmol/hr, a pressure of 19.45 psia, a temperature of ⁇ 256.8° F., and contains 1.01% N2, 97.32% methane, 1.17% C 2 hydrocarbons, and 0.50% heavier hydrocarbons.
  • First LNG fraction 6 is withdrawn from the lowest tray of the column at a flow rate of 121,047 lbmol/hr, a temperature of ⁇ 259.7° F., a pressure of 19.74 psia, and contains 1.56% N 2 , 96.81% methane, 1.14% C 2 hydrocarbons, and 0.49% heavier hydrocarbons.
  • This first LNG fraction 6 is passed through indirect heat exchanger 2 to produce stream 7 , which is at a temperature of ⁇ 256.8° F., a pressure of 19.45 psia, and has a vapor fraction of 3.1%.
  • Stream 7 is returned to column 5 under the lowest tray to provide boilup. This liquefaction process also requires approximately 229 MW of power.
  • Table 1 sets forth data of corresponding streams of the current process with a recirculation rate of 2.9 and the prior art process in order to more clearly illustrate the comparison.
  • the respective feed streams, 104 and 22 , and the respective product streams, 110 and 11 , and 130 and 10 are substantially identical with respect to all relevant properties. This equivalency of feed streams and product streams enables a valid comparison of the two processes.
  • the reboiler stream of the current process 112 is at a flow rate of 17,704 lbmol/hr, which is only 14.6% of the flow rate of the reboiler stream 6 of the '165 patent process, 121,047 lbmol/hr.
  • This difference is attributable to the fact that, while the '165 patent process requires that the entire liquid flow off of a column tray be recycled through the reboiler heat exchanger, the current process may be designed to function with various recirculation rates, permitting optimization of the amount of flow necessary to achieve the desired separation, and therefore only recycles the amount of bottoms liquid necessary to produce the required product.
  • Table 2 sets forth data of corresponding streams of the current process with a recirculation rate of 26.0 and the prior art process in order to demonstrate the flexibility of the current process.
  • the respective feed streams, 104 and 22 , and the respective product streams, 110 and 11 , and 130 and 10 are, again, substantially identical with respect to all relevant properties. This equivalency of feed streams and product streams enables a valid comparison of the two processes.

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US11/949,828 2007-12-04 2007-12-04 Thermosyphon reboiler for the denitrogenation of liquid natural gas Abandoned US20090139263A1 (en)

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Application Number Priority Date Filing Date Title
US11/949,828 US20090139263A1 (en) 2007-12-04 2007-12-04 Thermosyphon reboiler for the denitrogenation of liquid natural gas
EP08856437A EP2215415A2 (fr) 2007-12-04 2008-11-28 Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide
JP2010536542A JP2011517322A (ja) 2007-12-04 2008-11-28 液化天然ガスの脱窒素用熱サイホンリボイラー
CN2008801189441A CN102439384A (zh) 2007-12-04 2008-11-28 对液态天然气进行脱氮的热虹吸式再沸器
AU2008332869A AU2008332869A1 (en) 2007-12-04 2008-11-28 Thermosyphon reboiler for the denitrogenation of liquid natural gas
PCT/IB2008/003303 WO2009071977A2 (fr) 2007-12-04 2008-11-28 Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide
RU2010127280/06A RU2010127280A (ru) 2007-12-04 2008-11-28 Термосифонный ребойлер для деазотирования сжиженного природного газа

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JP2013036676A (ja) * 2011-08-08 2013-02-21 Air Water Inc ボイルオフガス中の窒素除去方法およびそれに用いる窒素除去装置
US8893513B2 (en) 2012-05-07 2014-11-25 Phononic Device, Inc. Thermoelectric heat exchanger component including protective heat spreading lid and optimal thermal interface resistance
US8991194B2 (en) 2012-05-07 2015-03-31 Phononic Devices, Inc. Parallel thermoelectric heat exchange systems
US9593871B2 (en) 2014-07-21 2017-03-14 Phononic Devices, Inc. Systems and methods for operating a thermoelectric module to increase efficiency
US10458683B2 (en) 2014-07-21 2019-10-29 Phononic, Inc. Systems and methods for mitigating heat rejection limitations of a thermoelectric module
CN117889612A (zh) * 2024-03-12 2024-04-16 新疆凯龙清洁能源股份有限公司 含氮甲烷气脱氮液化的方法及系统

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US10458683B2 (en) 2014-07-21 2019-10-29 Phononic, Inc. Systems and methods for mitigating heat rejection limitations of a thermoelectric module
CN117889612A (zh) * 2024-03-12 2024-04-16 新疆凯龙清洁能源股份有限公司 含氮甲烷气脱氮液化的方法及系统

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RU2010127280A (ru) 2012-01-10
WO2009071977A3 (fr) 2011-05-26
JP2011517322A (ja) 2011-06-02
WO2009071977A2 (fr) 2009-06-11
AU2008332869A1 (en) 2009-06-11
EP2215415A2 (fr) 2010-08-11

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