EP2215415A2 - Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide - Google Patents

Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide

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Publication number
EP2215415A2
EP2215415A2 EP08856437A EP08856437A EP2215415A2 EP 2215415 A2 EP2215415 A2 EP 2215415A2 EP 08856437 A EP08856437 A EP 08856437A EP 08856437 A EP08856437 A EP 08856437A EP 2215415 A2 EP2215415 A2 EP 2215415A2
Authority
EP
European Patent Office
Prior art keywords
stream
column
nitrogen
lng
reboiler
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.)
Withdrawn
Application number
EP08856437A
Other languages
German (de)
English (en)
Inventor
Adam Adrian Brostow
Mark Julian Roberts
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.)
Air Products and Chemicals Inc
Original Assignee
Air Products and Chemicals Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Air Products and Chemicals Inc filed Critical Air Products and Chemicals Inc
Publication of EP2215415A2 publication Critical patent/EP2215415A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • 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 different method is disclosed in US-A-5421165.
  • a process is disclosed wherein crude LNG is isentropically expanded in a turbine and cooled in a reboiler heat exchanger.
  • the cooled and expanded LNG stream is then passed through a valve, where it undergoes static decompression, prior to its injection into a denitrogenation column.
  • nitrogen is stripped from the falling liquid by the rising vapor, so that the vapor stream exiting the top of the column is enriched with nitrogen.
  • a liquid LNG stream is withdrawn from the bottom of the column as a nitrogen-diminished product.
  • 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 US-A-5421165 allegedly permits greater methane recovery.
  • 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 US-A-5421165, 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 by use of a thermosyphon reboiler to provide reboil to a nitrogen rejection column by partial vaporization of only a portion of nitrogen bottoms liquid against the LNG stream before or after expansion thereof prior to feed to the column.
  • This process allows for economic benefits by permitting a greater flexibility in the process design and eliminating the requirement of some equipment.
  • the present invention provides a process for the denitrogenation of a liquid natural gas (LNG) feed stream comprising:
  • step (e) at least partially vaporizing a portion of the nitrogen-diminished bottoms liquid by passing said portion through the thermosyphon reboiler of step (a) to form a partially vaporized stream;
  • step (f) injecting the partially vaporized stream into the column at a position of the column above that from which, when the thermosyphon reboiler is located external of the sump of the column, the bottoms liquid portion of step (e) is withdrawn or, when the thermosyphon reboiler is located in the sump of the column, the bottoms liquid portion of step (e) enters the thermosyphon reboiler and below that which received the LNG feed stream of step (b), to provide boilup for the column.
  • a crude LNG stream comprising between 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.
  • 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.
  • 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 is a schematic diagram illustrating a process for removing nitrogen from an
  • Fig. 2 is a schematic diagram illustrating a process for removing nitrogen from an LNG stream in accordance with another embodiment of the present invention.
  • Fig. 3 is Fig. 1 of US-A- 5421165 corrected by removal of the (second) turbine between the heat exchanger and valve (see description in US-A- 5421165 and Fig. 1 of parent PCT application PCT/FR92/00991 ; WO 93/08436).
  • high-pressure LNG stream 100 typically at a pressure of about 700 psia (4.8 MPa), containing from 1 mol% to 10 mol% nitrogen, and the remainder methane and possibly heavier hydrocarbons, is expanded via means 102 for expanding the LNG stream to produce lower-pressure LNG stream 104.
  • the expansion is preferably performed isentropicaliy, 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. Cooled, expanded LNG stream 108 is then substantially isenthalpically expanded through valve 109 and injected into nitrogen rejection column 150, this injection preferably taking place at the top of the column.
  • 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 30% N 2 and less than 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 15% and 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. Where valve 109 is not present, 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 boiiup.
  • the recirculation rate of the reboiler 106 is preferably at least 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.
  • 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.
  • An alternative embodiment is illustrated in Fig. 2. As in Fig.
  • 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 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. For example, by altering the recirculation rate (and, consequently, the flow through the reboiler), the reboiler and piping requirements associated with the process can be adjusted to minimize capital expenditures.
  • thermosyphon reboiler 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.
  • the internal thermosyphon process of the present invention is used, the nozzles required for withdrawal of the recycle stream are also eliminated.
  • 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.
  • 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 (124 kPa).
  • An overhead vapor stream 130 is withdrawn from the top of the column 150 at a flow rate of 8,141 Ibmol/h (3,692 kgmol/h), and contains 31.06% N 2 , 68.94% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia (124 kPa) and a temperature of -261.9 0 F (-163.3 0 C).
  • Bottoms stream 110 is withdrawn from the column 150 at a flowrate of 117,329 Ibmol/h (53,220 kgmol/h), a pressure of 19.45 psia (134.1 kPa), a temperature of -256.8 0 F (-160.4 0 C), 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 Ibmol/h (8,030 kgmol/h), a temperature of -256.8 0 F (-160.4 0 C), a pressure of 19.74 psia (136.1 kPa),, 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 0 F (-158.2 0 C), a pressure of 19.45 psia (134.1 kPa), 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.
  • thermosyphon reboiler 106 Following expansion in dense fluid expander 102, low pressure LNG stream 104, at a flow rate of 125,474 Ibmol/h (56,914 kgmol/h), a pressure of 71.84 psia (495.3 kPa), a temperature of -242.9 0 F (-152.7 0 C), 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 0 F (-158.4 0 C) and a pressure of 64.59 psia (445.3 kPa).
  • 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 (124 kPa).
  • An overhead vapor stream 130 is withdrawn from the top of the column 150 at a flow rate of 8,121 Ibmol/h (3,684 kgmol/h), and contains 31.54% N 2 , 68.46% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia (124 kPa)and a temperature of -262.O 0 F (-163.3 0 C).
  • Bottoms stream 110 is withdrawn from the column 150 at a flowrate of 117,353 Ibmol/h (53,230 kgmol/h), a pressure of 19.45 psia (134.1 kPa), a temperature of -256.7 0 F (-160.4 0 C), 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 Ibmol/h (53,230 kgmol/h), a temperature of -256.7 0 F (-160.4 0 C), a pressure of 19.74 psia (136.1 kPa), 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 0 F (-159.3 0 C), a pressure of 19.45 psia (134.1 kPa), 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.
  • This cooled, expanded stream is throttled through valve 3 and introduced into denitrogenation column 5 comprising 6 trays, at a pressure of 18 psia (124 kPa).
  • An overhead vapor stream 10 is withdrawn from the top of the column 5 at a flow rate of 8,122 Ibmol/h (3,684 kgmol/h), and contains 31.17% N 2 , 68.83% methane, and trace amounts of heavier hydrocarbons, at a pressure of 18 psia (124 kPa) and a temperature of -261.9 0 F (-163.3 0 C).
  • Bottoms stream 11 is withdrawn from the column 5 at a flowrate of 117,329 Ibmol/h (53,220 kgmol/h), a pressure of 19.45 psia (134.1 kPa), a temperature of -256.8 0 F (-160.4 0 C), 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 Ibmol/h (54,906 kgmol/h), a temperature of -259.7 0 F (-162.1 0 C), a pressure of 19.74 psia (136.1 kPa), 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 0 F (-160.4 0 C), a pressure of 19.45 psia (134.1 kPa), 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 Ibmol/h (8,030 kgmol/h), which is only 14.6% of the flow rate of the reboiler stream 6 of US-A- 5421165 process, 121,047 Ibmol/h (54,906 kgmol/h).
  • 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. As demonstrated in Table 2, altering the recirculation rate allows for great variation in the amount of fluid recycled through the thermosyphon reboiler 106, while maintaining equivalent recovery.
  • the total fluid flow through the reboiler (streams 112 and 6) is much closer in this comparison (117,353 Ibmol/h (53,230 kgmol/h) and 121 ,047 Ibmol/h (54,906 kgmol/h)), as is the percentage of fluid vaporized in the reboiler (3.7% and 3.1%).
  • the current process has the flexibility to achieve equivalent separation not only when implementing the preferred lower recycle flow rate, but also under flow rate conditions similar to the prior art.

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  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)
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Abstract

La dénitrogénation d'un courant de GNL brut détendu (104) est conduite dans une colonne de rejet d'azote (150) avec rebouillage par vaporisation partielle de seulement une partie (112) de l'azote liquide de fond de colonne dans un rebouilleur à thermosiphon (106) qui refroidit le courant de GNL brut avant ou après la détente (102). Le rebouilleur à thermosiphon peut être positionné à l'extérieur ou à l'intérieur du soutirage de la colonne.
EP08856437A 2007-12-04 2008-11-28 Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide Withdrawn EP2215415A2 (fr)

Applications Claiming Priority (2)

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
PCT/IB2008/003303 WO2009071977A2 (fr) 2007-12-04 2008-11-28 Rebouilleur à thermosiphon pour la dénitrogénation de gaz naturel liquide

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EP2215415A2 true EP2215415A2 (fr) 2010-08-11

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EP (1) EP2215415A2 (fr)
JP (1) JP2011517322A (fr)
CN (1) CN102439384A (fr)
AU (1) AU2008332869A1 (fr)
RU (1) RU2010127280A (fr)
WO (1) WO2009071977A2 (fr)

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JP5679201B2 (ja) * 2011-08-08 2015-03-04 エア・ウォーター株式会社 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
AU2012359032A1 (en) * 2011-12-20 2014-07-03 Conocophillips Company Liquefying natural gas in a motion environment
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
US20130291555A1 (en) 2012-05-07 2013-11-07 Phononic Devices, Inc. Thermoelectric refrigeration system control scheme for high efficiency performance
US9593871B2 (en) 2014-07-21 2017-03-14 Phononic Devices, Inc. Systems and methods for operating a thermoelectric module to increase efficiency
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CN102439384A (zh) 2012-05-02
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
US20090139263A1 (en) 2009-06-04

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