AU2002319155B2 - Method for separating nitrogen out of a hydrocarbon-rich fraction that contains nitrogen - Google Patents

Method for separating nitrogen out of a hydrocarbon-rich fraction that contains nitrogen Download PDF

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Publication number
AU2002319155B2
AU2002319155B2 AU2002319155A AU2002319155A AU2002319155B2 AU 2002319155 B2 AU2002319155 B2 AU 2002319155B2 AU 2002319155 A AU2002319155 A AU 2002319155A AU 2002319155 A AU2002319155 A AU 2002319155A AU 2002319155 B2 AU2002319155 B2 AU 2002319155B2
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Australia
Prior art keywords
nitrogen
hydrocarbon
rich
cycle
fraction
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AU2002319155A
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AU2002319155A1 (en
Inventor
Peter Butz
Martin Gwinner
Rune Jensen
Pentti Paurola
Rudolf Stockmann
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Linde GmbH
Equinor ASA
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Linde GmbH
Statoil ASA
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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
    • F25J3/0204—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
    • F25J3/0233—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
    • F25J3/0228—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
    • F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
    • F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • 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
    • F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/04—Mixing or blending of fluids with the feed stream
    • 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
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/90—Boil-off gas from storage
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/30—Compression of the feed stream
    • 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
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/60—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being hydrocarbons or a mixture of hydrocarbons
    • 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/42—Processes or apparatus involving steps for recycling of process streams the recycled stream being 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
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/90—Processes or apparatus involving steps for recycling of process streams the recycled stream being boil-off gas from storage
    • 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
    • F25J2260/00—Coupling of processes or apparatus to other units; Integrated schemes
    • F25J2260/20—Integration in an installation for liquefying or solidifying a fluid stream
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/12—External refrigeration with liquid vaporising loop
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/60—Closed external refrigeration cycle with single component refrigerant [SCR], e.g. C1-, C2- or C3-hydrocarbons
    • 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
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/66—Closed external refrigeration cycle with multi component refrigerant [MCR], e.g. mixture of hydrocarbons
    • 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
    • F25J2280/00—Control of the process or apparatus
    • F25J2280/02—Control in general, load changes, different modes ("runs"), measurements

Description

P :\OPERPH 12366 O5 md do- I/2007 -1- Description A method for separating nitrogen out of a nitrogen-containing, hydrocarbon-rich fraction The invention relates to a combination consisting of: a method for liquefying a hydrocarbon-rich stream, particularly a natural gas stream, by means of indirect heat exchange with at least one refrigerant cycle and/or by means of indirect heat exchange with at least one refrigerant mixture cycle; and a method for separating nitrogen out of a hydrocarbon-rich fraction, which contains nitrogen and which results over the course of the liquefying method, whereby the hydrocarbon-rich fraction is compressed in one stage or in multiple stages, is cooled whereby being partially condensed, and is fed to a double column nitrogen separating process.
The term "double column nitrogen separating process" is to be understood to relate to a wide variety of nitrogen separating processes independent of whether the process concerned is a pure double column process, a double column process with separation of the heavy hydrocarbons, a double column process with a nitrogen enrichment column with or without separation of the heavy hydrocarbons, or a single column process with or without prior separation of the heavy hydrocarbons etc.
Generic methods for liquefying a hydrocarbon-rich stream are known; see for instance DE- B 197 16 415. The latter describes the liquefaction of a hydrocarbon-rich stream against a refrigerant mixture cycle cascade. Besides the method described in DE-B 197 16 415 for liquefying a hydrocarbon-rich stream, a multitude of further liquefaction methods may be known to those skilled in the art. Examples are processes wherein the hydrocarbon-rich stream is liquefied against a refrigerant cycle cascade or by means of a so-called dual flow liquefaction process.
P:\OPERPHIil12306650 nd doc 103/2007 -2- SThe compression of the refrigerant/s or refrigerant mixture/s circulating in the refrigerant cycles and/or refrigerant (mixture) cycles is undertaken by means of energy-intensive compressors. To generate the electrical energy required for the compressor, gas turbines t are provided which, as a rule, have so far been fed by a partial stream of the hydrocarbonrich stream which is to be liquefied. Although the combustion systems and thus the fuel gas of such gas turbines are able to tolerate comparatively high nitrogen concentrations, C they have the disadvantage that the NOx content of their waste gas is comparatively high, i.e. for instance 25 Mol-ppm NO,.
So-called Low-NO, gas turbines (these are gas turbines, which are equipped with a socalled "Dry-Low-NOx-Emission-Combustion-System") are already available, however these require to be operated with a comparatively nitrogen-poor gas mixture. The maximum nitrogen content of the fuel gas fed to the turbines should not exceed 10-30 moldepending on the turbine type, in order not to exceed the desired NOx threshold value of max. 25 mol-ppm for the gas turbine waste gas.
Furthermore, it must be observed that changes relating to the so-called low heating value (LHV), the so-called specific gravity and the wobbe index of the hydrocarbon-rich fuel gas are limited to for instance 1% within for instance 30 seconds since only thereby a stable operation of the gas turbine is guaranteed, without instabilities resulting with regard to the flame for instance.
An aim of the present invention is to propose a generic method combination which allows a reduction of the energy consumption of the nitrogen separation method whilst at the same time reducing the investment costs.
According to the invention, this is achieved in that the cooling and partial condensation of the nitrogen-containing, hydrocarbon-rich fraction is undertaken against the refrigerant cycle, or at least one of the, refrigerant cycle(s) and/or refrigerant mixture cycle(s) of the method for liquefying a hydrocarbon-rich stream.
Inasfar as the liquefaction of the hydrocarbon-rich stream is achieved by indirect heat exchange with the refrigerants of a refrigerant mixture cycle cascade wherein the P:\OPER\PHH\12360650 end do. 103/200)7 -3- Srefrigerant mixture cycle cascade consists of refrigerant mixture cycles having at least 3 different refrigerant compositions and wherein the first of the three refrigerant mixture cycles is for precooling (precooling cycle), the second refrigerant mixture cycle is for tt' liquefying (liquefaction cycle) and the third refrigerant mixture cycle is for subcooling (subcooling cycle) of the hydrocarbon-rich stream to be liquefied, in accordance with an advantageous embodiment of the method combination in accordance with the invention ¢c, C the cooling and partial condensation of the nitrogen-containing, hydrocarbon-rich fraction is undertaken against the precooling cycle and the subcooling cycle of the method for liquefying the hydrocarbon-rich stream.
The invention as well as further embodiments of the same are explained in greater detail, by way of example only, with reference to the embodiment example shown in Figs. 1 and 2.
Shown are in Fig. 1: a three-stage compressor unit which serves for the compression of the nitrogen-containing, hydrocarbon-rich stream; Fig. 2: is an embodiment example of a double column nitrogen separation process.
As shown in Fig. 1, via line 1 of a three-stage compressor unit the three stages of the compressor unit being designated as V1, V2 and V3 a nitrogen-containing, hydrocarbonrich fraction is supplied. This fraction can be composed of any hydrocarbon-rich streams resulting within the respective liquefaction process, for instance of a nitrogen stripper, boil-off gas etc. A nitrogen-rich stream which will be discussed in greater detail in the following can be admixed at least intermittently via line 2 to the nitrogen-containing, hydrocarbon-rich fraction.
W002/088612 PCT/EPO2/04721 4 The nitrogen-containing, hydrocarbon-rich fraction, to which the nitrogen-rich stream was optionally added via line 2, is fed under slightly superatmospheric pressure via line 3 to the first compressor stage VI. After compression, this fraction is fed via line 4 to an aftercooler 1 and there cooled. This procedure is repeated after the 2 nd and 3 rd compressor stages V2 and V3 in the respective aftercoolers E2 and E3.
The nitrogen-containing, hydrocarbon-rich fraction taken off from the compressor unit via line 6 has a pressure between 35 and 65 bar at a temperature of 5 to The nitrogen-containing, hydrocarbon-rich fraction taken off from the compressor unit as shown in the following in Fig. 2 is now cooled against the high purity nitrogen stream, which is fed to the heat'exchanger E4 via line 16 and will be discussed in more detail in the following, and in accordance with the invention is cooled against a refrigerant (mixture) stream x to a temperature between -20 and 0 C. The heat exchangers E4 to E7 shown in Fig. 2 are preferably in the form of socalled plate heat exchangers.
The nitrogen-containing, hydrocarbon-rich fraction is subsequently fed via line 8 to a further heat exchanger E5 and in this heat exchanger again cooled against the previously mentioned high purity nitrogen stream in line 15 as well as a further refrigerant (mixture) stream y to a temperature between -80 and -120 0
C.
Inasfar as the method employed for liquefying a hydrocarbon-rich stream is a refrigerant mixture cycle cascade method, it is useful for the purpose of cooling the nitrogen-containing, hydrocarbon-rich fraction if the latter is cooled and partially condensed in the heat exchanger E4 against the precooling cycle x of the refrigerant mixture cycle cascade and in the heat exchanger E5 against the subcooling cycle y of the refrigerant mixture cycle cascade.
Subsequently, the nitrogen-containing, hydrocarbon-rich fraction is fed via line 9 to the heat exchanger E6, and in the latter taken off against a stripping gas stream which is withdrawn from the lower column a of the double column K via line 11 and subsequently recirculated to it and there cooled to a temperature of -120 to -140 0
C
V002/088612 PCT/EPO2/04721 prior to the nitrogen-containing, hydrocarbon-rich fraction being fed via line 10 of the lower column a to the double column K. The lower column a has an operating pressure of approx. 30 bar.
From the sump of the lower column a, a nitrogen-depleted hydrocarbon rich fraction is withdrawn via line 12 and is cooled in the previously described heat exchanger to a temperature between -155 and -160 0 C prior to this fraction being fed via line 13 and the expansion valve 13' of the upper column b to the double column K. The upper column b has an operating pressure of approx. 2 bar.
From the head region of the lower column a of the double column K, a nitrogenenriched, hydrocarbon-rich liquid or gaseous fraction is withdrawn via line 14, cooled in the heat exchanger E7 if required partially condensed and recirculated to the head of the upper column b of the double column K.
At the head of the upper column b of the double column K, the previously mentioned high purity nitrogen gas fraction, having a hydrocarbon residue of for instance 100 ppm and a temperature of -190°C is withdrawn via line 15. This gaseous fraction is initially heated in the heat exchanger E7 and subsequently fed to the previously described heat exchangers E4 and E5 and in these heated against the nitrogencontaining, hydrocarbon-rich fraction which is fed to the double column K for separation.
The heated high purity nitrogen gas fraction can be released into the atmosphere via line 17. A further option as previously described is to return a partial stream of this gaseous fraction via line 2 upstream of the compressor station V1 to V3.
This mode of operation serves to keep the nitrogen content of the gaseous fraction fed to the compressor station VI to V3 above a desired or required minimum concentration of for inslance 15 In the event this minimum concentration is not reached, the desired nitrogen purity in the stream released into the atmosphere cannot be achieved without an additional preseparation step. Moreover, the process procedure in accordance with the iivention is simplified and stabilised since the P:\OPERPHI 12360650 ,nd do.- I )3R2007 -6fluctuations in the nitrogen content of the gaseous fraction fed to the compressor station V1 to V3 can be minimised. This however is only possible at the expense of a higher energy consumption.
Via a lateral withdrawal (line 18) a methane-rich liquid fraction is withdrawn from the lower region of the upper column b of the double column K which fraction can for instance be fed to a nitrogen strip column which is for instance integrated in a LNG process. This can be achieved by means of gravitation or pumping of the liquid. The methane-rich liquid fraction in accordance with one embodiment of the invention preferably has a nitrogen content of max. 5% by volume.
Whilst for the cooling of the nitrogen-containing, hydrocarbon-rich stream which is to be fractioned, the separated hydrocarbon-rich stream (for instance the methane stream) was as a rule until today heated and again vaporised, the refrigeration in accordance with the present invention is provided by way of the two refrigerant cycles or refrigerant mixture cycles x and y. Depending on the respective method employed for liquefying the hydrocarbon-rich stream, the cooling and partial condensation of the nitrogen-containing, hydrocarbon-rich stream to be separated can naturally also be achieved by only one refrigerant stream or refrigerant mixture stream. In this case, the hydrocarbon-rich stream can be withdrawn in liquid form (see lateral withdrawal via line 18) from the process or the plant.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims (9)

1. A method comprising a combination of: a method for liquefying a hydrocarbon-rich stream by means of indirect heat exchange with at least one refrigerant cycle and/or by means of indirect heat exchange with at least one refrigerant mixture cycle, and; a method for separating nitrogen out of a hydrocarbon-rich fraction which contains nitrogen and which is obtained over the course of the liquefying method, whereby the hydrocarbon-rich fraction is compressed in one stage or in multiple stages, is cooled whereby being partially condensed, and is fed to a double column nitrogen separating process, wherein the cooling and partial condensation of the nitrogen-containing, hydrocarbon-rich fraction is undertaken against the, or at least one of the, refrigerant cycle(s) and/or refrigerant mixture cycle(s) of the method for liquefying a hydrocarbon-rich stream.
2. The method in accordance with Claim 1, wherein the hydrocarbon-rich stream is a natural gas stream.
3. The method in accordance with Claim 1 or 2, wherein the liquefaction of the hydrocarbon-rich stream is achieved by indirect heat exchange with the refrigerants of a refrigerant mixture cycle cascade which consists of refrigerant mixture cycles having at least 3 different refrigerant compositions, a first of the three refrigerant mixture cycles being for precooling (precooling cycle), a second refrigerant mixture cycle being for liquefying (liquefaction cycle) and a third refrigerant mixture cycle being for subcooling (subcooling cycle) of the hydrocarbon-rich stream to be liquefied, and wherein the cooling and partial condensation of the nitrogen-containing, hydrocarbon-rich fraction is undertaken against the precooling cycle and the subcooling cycle of the method for liquefying the hydrocarbon-rich stream. I P OPERPHHI12366O .cnd dod-l1032007 -8-
4. The method in accordance with any one of Claims 1 to 3, wherein in the double column nitrogen separation process a methane-rich liquid fraction is taken off from the sump of the upper column and supplied towards a further use.
The method in accordance with Claim 4, wherein said methane-rich liquid fraction is used as a scrubber liquid in a nitrogen stripping process.
6. The method in accordance with Claim 4 or 5, wherein the taken off methane-rich liquid fraction is pumped.
7. The method in accordance with any one of Claims 4 to 6, wherein the methane-rich liquid fraction taken off has a nitrogen content of max. 5% by volume.
8. The method in accordance with any one of the preceding claims, wherein the nitrogen-rich fraction recovered in the double column nitrogen separation process is heated by way of heat exchange with the nitrogen-containing, hydrocarbon-rich fraction to be cooled.
9. The method in accordance with Claim 8, wherein at least one part stream of the heated nitrogen-rich fraction is at least intermittently added to the nitrogen-containing, hydrocarbon-rich fraction prior to its compression. The method in accordance with Claim 1 and substantially as herein described with reference to the accompanying drawings.
AU2002319155A 2001-05-02 2002-04-29 Method for separating nitrogen out of a hydrocarbon-rich fraction that contains nitrogen Ceased AU2002319155B2 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE2001121339 DE10121339A1 (en) 2001-05-02 2001-05-02 Process for separating nitrogen from a nitrogen-containing hydrocarbon fraction
DE10121339.5 2001-05-02
PCT/EP2002/004721 WO2002088612A1 (en) 2001-05-02 2002-04-29 Method for separating nitrogen out of a hydrocarbon-rich fraction that contains nitrogen

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AU2002319155A1 AU2002319155A1 (en) 2003-04-17
AU2002319155B2 true AU2002319155B2 (en) 2007-03-29

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EP1715267A1 (en) 2005-04-22 2006-10-25 Air Products And Chemicals, Inc. Dual stage nitrogen rejection from liquefied natural gas
DE102007007097A1 (en) * 2007-02-13 2008-08-14 Linde Ag Process for liquefying a hydrocarbon-rich stream
DE102009009477A1 (en) * 2009-02-19 2010-08-26 Linde Aktiengesellschaft Process for separating nitrogen
DE102009038458A1 (en) * 2009-08-21 2011-02-24 Linde Ag Process for separating nitrogen from natural gas
FR2991442B1 (en) * 2012-05-31 2018-12-07 L'air Liquide,Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude APPARATUS AND METHOD FOR CRYOGENIC SEPARATION OF A MIXTURE OF CARBON MONOXIDE AND METHANE AND HYDROGEN AND / OR NITROGEN
WO2014173598A2 (en) * 2013-04-22 2014-10-30 Shell Internationale Research Maatschappij B.V. Method and apparatus for producing a liquefied hydrocarbon stream

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DE2502959A1 (en) * 1975-01-24 1976-07-29 Linde Ag Natural gas liquefaction process - with circulating medium leakage compensated by higher boiling liquid fraction from feed stock

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DE10121339A1 (en) 2002-11-07

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