AU2010202696B2 - Process for separating off nitrogen - Google Patents

Process for separating off nitrogen Download PDF

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AU2010202696B2
AU2010202696B2 AU2010202696A AU2010202696A AU2010202696B2 AU 2010202696 B2 AU2010202696 B2 AU 2010202696B2 AU 2010202696 A AU2010202696 A AU 2010202696A AU 2010202696 A AU2010202696 A AU 2010202696A AU 2010202696 B2 AU2010202696 B2 AU 2010202696B2
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fraction
double
hydrocarbon
separated
nitrogen
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AU2010202696A1 (en
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Heinz Bauer
Andreas Bub
Stephan Burmberger
Rainer Sapper
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Linde GmbH
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Linde GmbH
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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
    • F25J3/0238—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 2 carbon atoms 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
    • F25J2200/08—Processes or apparatus using separation by rectification in a triple 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
    • F25J2200/38—Processes or apparatus using separation by rectification using pre-separation or distributed distillation before a main column system, e.g. in a at least a double 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
    • F25J2200/74—Refluxing the column with at least a part of the partially condensed overhead 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • 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
    • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
    • 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
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • 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)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

Abstract Process for separating off nitrogen 5 A process is described for separating off C2.- hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons, wherein a) the feed fraction (1, 20) is partially condensed (El, El', E3) and separated by rectification (T) into a C2.- hydrocarbon-rich fraction (11) and a C2.-hydrocarbon depleted fraction (2), 10 b) the C2+-hydrocarbon-depleted fraction (2) is partially condensed (E2) and separated into a liquid fraction which forms at least in part the reflux (3) for the separation by rectification (T), and a C2.- hydrocarbon-depleted gas fraction (4), and c) the C2.-hydrocarbon-depleted gas fraction (4) is separated in a double-column 15 process (N) into a nitrogen-rich fraction (8') and a methane-rich fraction (7"). According to the invention, the liquid fraction obtained in process step b) is fed (10) at least in part likewise to the double-column process (N) and in this separated into a nitrogen-rich fraction (8') and a methane-rich fraction (7"). (Figure 2 is associated herewith.) co r CD) N c a)

Description

- 1 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant/s: Linde Aktiengesellschaft Actual Inventor/s: Heinz Bauer and Rainer Sapper and Andreas Bub and Stephan Burmberger Address for Service is: SHELSTON IP 60 Margaret Street Telephone No: (02) 9777 1111 SYDNEY NSW 2000 Facsimile No. (02) 9241 4666 CCN: 3710000352 Attorney Code: SW Invention Title: PROCESS FOR SEPARATING OFF NITROGEN The following statement is a full description of this invention, including the best method of performing it known to me/us: File: 66651AUP00 -2 Description Process for separating off nitrogen 5 The invention relates to a process for separating off C2.-hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons, wherein a) the feed fraction is partially condensed and separated by rectification into a C 2
.
hydrocarbon-rich fraction and a C 2 .- hydrocarbon-depleted fraction, b) the C 2 .-hydrocarbon-depleted fraction is partially condensed and separated into 10 a liquid fraction which forms at least in part the reflux for the separation by rectification, and a C 2 .-hydrocarbon-depleted gas fraction, and c) the C 2 .- hydrocarbon-depleted gas fraction is separated in a double-column process into a nitrogen-rich fraction and a methane-rich fraction. 15 A process of the type in question for separating off C 2 .- hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons is known, for example, from US patent 4,664,686. With reference to Figure 1 which essentially corresponds to Figure 3 of the abovementioned US patent, a description will be given hereinafter of the process of the type in question for separating off C 2 .- hydrocarbons from a feed fraction 20 containing essentially nitrogen and hydrocarbons. Via line 1, a feed fraction containing essentially nitrogen and hydrocarbons and which originates, for example, from an oil degassing or LNG plant which is not shown in the figure, is introduced. The feed fraction (petroleum associated gas or light expansion 25 gas) preferably has a pressure of above 25 bar. It has optionally already been subjected to a pretreatment, such as desulphurization and/or drying. In the heat exchanger E1, the feed fraction is cooled and partially condensed against process streams which will be considered in more detail hereinafter. Via line 1', the partially condensed freed fraction is taken off from the heat exchanger El and, via the expansion valve a, applied 30 to a separation column T. Separating off nitrogen from a feed fraction containing essentially nitrogen and hydrocarbons by means of a double-column process, as will be described hereinafter, customarily requires a nitrogen content in the feed fraction of at least 30% by volume. 35 This minimum nitrogen content is necessary in order to be able to achieve the customarily required purities for the product streams nitrogen, the methane content of which should be less 0.1% by volume, and natural gas or methane, the nitrogen content - 3 of which should be less than 5% by volume, which product streams are obtained by the double-column process. If the nitrogen content in the feed fraction falls below the abovementioned minimum 5 nitrogen content at times or fundamentally, enrichment of the nitrogen concentration in the feed fraction before it is fed into the double-column process is necessary or desirable. The abovementioned separation column T serves for this purpose. By means of the separation column T, a low-nitrogen, C 2 +-rich hydrocarbon fraction is separated off from the feed fraction, which C 2 .-rich hydrocarbon fraction is taken off from the 10 bottom of the separation column T via the line 5, cold-producingly expanded in the valve b and, after warming and vaporization in the heat exchanger El, is released via line 5' as what is termed a medium-pressure hydrocarbon fraction. A substream of this liquid fraction taken off from the bottom of the separation column T, after a cold-producing expansion in the valve c, is added via the line 6 to the methane-rich fraction taken off 15 from the double-column process N, which methane-rich fraction will be considered in more detail hereinafter, and thus serves for providing cold in the top condenser E2. Via line 2, from the top of the separation column T, a C 2 .- hydrocarbon-depleted fraction is taken off, which fraction has a higher nitrogen content compared with the feed 20 fraction introduced in the line 1. This C 2 .- hydrocarbon-depleted fraction is partially condensed in the heat exchanger or top condenser E2 and fed to the separator D via the line 2'. From the bottom of the separator D, via line 3, the liquid fraction occurring is taken off and fed as reflux to the column T. Generally, a return pump P must be provided in the line 3. This can be omitted if the separator D is arranged above the 25 feed-in point of the reflux stream. The C 2 .-hydrocarbon-depleted gas fraction occurring in the separator D is fed via line 4 to a double-column process N which is shown only schematically. Such double-column processes are sufficiently known to those skilled in the art from the prior art. A prior art 30 double-column process is described, for example, in the German patent application 102009008229 which was not published before the priority date of the present application. By citing the German patent application 102009008229, the contents thereof are hereby integrated fully into the contents of the present patent applications. 35 The bottom of the separation column T is heated by means of a bottom heater integrated into the heat exchanger El - shown by the pipe sections 9 and 9'.
-4 The nitrogen-rich fraction obtained in the double-column process N is taken off via line 8, warmed in the heat exchanger El against the feed fraction to be cooled and then fed via line 8' to further use thereof. The methane-rich fraction obtained in the double 5 column process N is fed via line 7 to the top condenser E2 - if appropriate after previous addition of a substream of the liquid fraction taken off in the separation column T warmed therein and vaporized at least in part, subsequently fed via line 7' to the heat exchanger El and after further warming and complete vaporization against the feed fraction to be cooled is fed via line 7" to further use thereof. 10 In a process as described with reference to Figure 1, the main feature is directed towards optimizing the flow rate of the C 2 .- hydrocarbon fraction taken off from the bottom of the separation column T in order to be able to release this at elevated pressure via the lines 5 and 5'. The remaining hydrocarbons are released at a lower 15 pressure via the line 7" in this procedure. Since both hydrocarbon fractions 5'/7" are to be released together, it is necessary to compress at least one of the two fractions, customarily fraction 7", to the desired release pressure - this compression is not shown in Figure 1. For this reason, the composition of the liquid fraction 5 taken off from the bottom of the separation column T is optimized to a low nitrogen content. The 20 composition of the gas fraction taken off from the top of the separation column T, in contrast, is optimized to a nitrogen content as high as possible, but not in respect of the hydrocarbon composition, in particular a high methane content. If compression of the hydrocarbon fraction(s) is to be avoided, release of the 25 hydrocarbon fractions at a pressure which is uniform and simultaneously as high as possible must be sought. The methane-rich stream taken off from the double-column process N in this case must be set such that it can fulfil its tasks in the heat integration at a pressure as high as possible. 30 Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. It is an object of the present invention to overcome or ameliorate at least one of the 35 disadvantages of the prior art, or to provide a useful alternative.
-5 According to a first aspect the present invention provides a process for separating off C2-hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons, wherein a) the feed fraction is partially condensed and separated by rectification into 5 a C2,-hydrocarbon-rich fraction and a C2,-hydrocarbon-depleted fraction, b) the C2,-hydrocarbon-depleted fraction is partially condensed and separated into a liquid fraction which forms at least in part the reflux for the separation by rectification, and a C2,-hydrocarbon-depleted gas fraction, and 10 c) the C2-hydrocarbon-depleted gas fraction is separated in a double column process into a nitrogen-rich fraction and a methane-rich fraction, wherein the C2-hydrocarbon-depleted fraction is partially condensed against the methane-rich fraction withdrawn from the double-column process, and 15 wherein the liquid fraction obtained in process step b) is fed at least in part likewise to the double-column process and in this separated into a nitrogen-rich fraction and a methane-rich fraction. According to a second aspect the present invention provides C2,-hydrocarbons when 20 separated from a feed fraction containing essentially nitrogen and hydrocarbons and when produced by the process according to the first aspect. It is a preferred object of the present invention to indicate a process of the type in question for separating off C2-hydrocarbons from a feed fraction containing essentially 25 nitrogen and hydrocarbons, which avoids the disadvantages described. For achieving this preferred object, a process is indicated for separating off C2, hydrcarbons from a feed fraction containing essentially nitrogen and hydrocarbons, which is characterized in that the liquid fraction obtained on the partial condensation of 30 the C2-hydrocarbon-depleted fraction taken off from the top of the separation column T is fed at least in part, together with the C2-hydrocarbon-depleted gas fraction, to the double-column process and in this separated into a nitrogen-rich fraction and a methane-rich fraction.
- 5a Further advantageous configurations of the process according to the invention for separating off C2,-hydrcarbons from a feed fraction containing essentially nitrogen and hydrocarbons, which are subjects of the dependent claims, are characterized in that 5 - the feed fraction containing essentially nitrogen and hydrocarbons is divided into - 6 a plurality of substreams, these are partially condensed separately from one another and then separated by rectification, - the cooling of the substreams of the feed fraction proceeds in double-pipe heat 5 exchangers, preferably in helically coiled heat exchangers, wherein the cooling or partial condensation of the substreams proceeds preferably in the tubes and the vaporization or warming of the cold fractionation products proceeds on the shell side of the helically coiled heat exchangers and/or preferably the cooling or partial condensation of the substreams proceeds in an ascending manner on the 10 tube side and the warming or vaporization of the fractionation products proceeds in a falling manner on the shell side, and - at least one of the substreams of the feed fraction is separated into a gas fraction and a liquid fraction and these are fed separately from one another to 15 the separation by rectification. The process according to the invention for separating off C 2 .- hydrcarbons from a feed fraction containing essentially nitrogen and hydrocarbons and also other configurations thereof will be described in more detail hereinafter with reference to the exemplary 20 embodiments shown in Figures 2 and 3. Hereinafter, in the explanation of the exemplary embodiments shown in Figures 2 and 3, only the differences from the procedure as shown in Figure 1 will be considered. As shown in Figures 2 and 3, the liquid occurring in the separator D is fed according to 25 the invention in part via line 10 and expansion valve d to the double-column process N. The remaining part of the liquid from the separator D is fed to the separation column T via line 3 as reflux stream. Owing to the feed to be provided according to the invention of the above-described 30 liquid fraction to the double-column process N, the energy balance thereof is altered in such a manner that the methane-rich stream taken off from the double-column process N via line 7 is completely liquid, instead of partially vaporized as previously. As a result, sufficient cold capacity is available to the top condenser E2 even without the addition shown in Figure 1 of a substream of the liquid fraction taken off from the bottom of the 35 separation column T. The liquid fraction taken off from the bottom of the separation column T via line 11 is therefore, after expansion in the valve e, added to the methane- -7 rich fraction between the top condenser E2 and heat exchanger El. The liquid fraction taken off via line 11 is therefore advantageously only used for precooling the feed fraction in the heat exchanger El. In the procedure according to the invention, the required temperature profile of the overall process can therefore be provided by 5 hydrocarbons vaporizing essentially isobarically - this means that only conventional pressure drops occur of in total a maximum of 1 bar in the heat exchangers E2 and El. By means of the procedure according to the invention, the fraction taken off via line 2 from the top of the separation column T is now freed as far as possible of C 2
.
10 hydrocarbons and carbon dioxide. The methane-rich stream taken off from the double column process N via line 7 thus has a significantly higher methane content than that in the procedure shown in Figure 1. Advantageously, the operation of the separation column T is optimized to the effect that the content of C 2 .- hydrocarbons in the fraction taken off via line 2 from the top of the separation column T is a maximum of 0.1% by 15 volume (1000 vppm), preferably a maximum of 0.01% by volume (100 vppm). The process procedure shown in Figure 3 differs from that shown in Figure 2 essentially in that the multipipe heat exchanger El is divided into a plurality of double pipe heat exchangers El, El' and E3. In addition, an additional separator D' is 20 provided. Such a process procedure makes it possible to ensure stable flow conditions in the heat exchangers in a wide range of feed fraction composition and load states. The feed fraction in this embodiment is divided into two substreams 1 and 20. Both are cooled and partially condensed in the heat exchangers El and El'. The first substream 25 is fed in a known manner to the separation column T via line 1' and expansion valve a. The second substream is fed to the heat exchanger E3 via line 20' and subsequently separated in the separator D' into a liquid fraction and a gas fraction. For the purpose of heating the bottom of the separation column T, a hydrocarbon-rich 30 fraction is taken off via line 30 at a suitable point, warmed in a heat exchanger E3 and also partially vaporized and then fed via line 30' to the separation column T. The gaseous fraction taken off via line 22 from the separator D' is cooled in the heat exchanger El', partially condensed and subsequently fed via line 22' and expansion 35 valve f to the separation column T. Via the choice of the position of the feed-in points of the fractions in the lines 1', 21 and/or 22', the operation of the separation column T can -8 be varied or optimized. The above-described heat exchangers El and El' are advantageously constructed as helically coiled heat exchangers, wherein the cooling or partial condensation of the feed 5 fractions proceeds in the tubes and the vaporization or warming of the cold fractionation products proceeds on the shell side of the helically coiled heat exchangers. In addition, the cooling or partial condensation of the feed fraction preferably proceeds in an ascending manner on the tube side and the warming or vaporization of the fractionation products proceeds in a falling manner on the shell side. 10 If the top condenser E2 is constructed as a circulation evaporator, complete vaporization of the methane-rich fraction taken off via line 7 from the double-column process N can be achieved in a controlled manner. From this circulation vessel having a controlled liquid level in which the top condenser E2 is arranged, the fraction 7' is 15 thereby taken off exclusively in the gaseous state. The process according to the invention for separating off C 2 .-hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons makes it possible to achieve a procedure in which now only one hydrocarbon-rich fraction can be obtained at a 20 comparatively high pressure level and utilized for providing cold, and so generally recompression of this fraction is unnecessary.

Claims (9)

1. Process for separating off C 2 ,-hydrocarbons from a feed fraction containing essentially nitrogen and hydrocarbons, wherein 5 d) the feed fraction is partially condensed and separated by rectification into a C 2 ,-hydrocarbon-rich fraction and a C 2 -hydrocarbon-depleted fraction, e) the C 2 -hydrocarbon-depleted fraction is partially condensed and separated into a liquid fraction which forms at least in part the reflux for the separation by rectification, and a C 2 -hydrocarbon-depleted gas 10 fraction, and f) the C 2 -hydrocarbon-depleted gas fraction is separated in a double column process into a nitrogen-rich fraction and a methane-rich fraction, wherein the C 2 -hydrocarbon-depleted fraction is partially condensed against the methane-rich fraction (7) withdrawn from the double-column 15 process, and wherein the liquid fraction obtained in process step b) is fed at least in part likewise to the double-column process and in this separated into a nitrogen-rich fraction and a methane-rich fraction. 20
2. Process according to Claim 1, wherein feed fraction containing essentially nitrogen and hydrocarbons is divided into a plurality of substreams, these are partially condensed separately from one another and then separated by rectification.
3. Process according to Claim 2, wherein the cooling of the substreams of the feed 25 fraction is performed in double-pipe heat exchangers.
4. The process according to claim 3, wherein the cooling or partial condensation of the sub streams proceeds in the tubes of said double-pipe heat exchangers and the vaporization or warming of cold fractionation products proceeds on the shell side of said 30 double-pipe heat exchangers.
5. The process according to claim 3, wherein the cooling or partial condensation of the sub streams proceeds in an ascending manner on the tube side of said double-pipe heat exchangers and the warming or vaporization of cold fractionation products 35 proceeds in a falling manner on the shell side of said double-pipe heat exchangers.
6. The process according to claim 4, wherein the cooling or partial condensation of -10 the sub streams proceeds in an ascending manner on the tube side of said double-pipe heat exchangers and the warming or vaporization of cold fractionation products proceeds in a falling manner on the shell side of said double-pipe heat exchangers. 5
7. The process according to any one of claims 3 to 6, wherein said double-pipe heat exchangers are helically coiled heat exchangers
8. Process according to any one of claims 2 to 7, wherein at least one of the substreams of the feed fraction is separated into a gas fraction and a liquid fraction and 10 these are fed separately from one another to the separation by rectification in said rectification column.
9. C 2 -hydrocarbons when separated from a feed fraction containing essentially nitrogen and hydrocarbons and when produced by the process according to any one of 15 the preceding claims.
AU2010202696A 2009-07-06 2010-06-28 Process for separating off nitrogen Active AU2010202696B2 (en)

Applications Claiming Priority (2)

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DE102009036366.1 2009-07-06
DE102009036366A DE102009036366A1 (en) 2009-08-06 2009-08-06 Process for separating nitrogen

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AU2010202696B2 true AU2010202696B2 (en) 2016-02-25

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DE (1) DE102009036366A1 (en)
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RU2010132951A (en) 2012-02-10
MX337989B (en) 2016-03-30
MX2010007252A (en) 2011-02-07
AU2010202696A1 (en) 2011-01-20

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