CA2520800C

CA2520800C - Systems and methods for low-temperature gas separation

Info

Publication number: CA2520800C
Application number: CA2520800A
Authority: CA
Inventors: Vadim Ivanovich Alferov; Lev Arkad'evich Bagirov; Vladimir Isaakovich Feygin; Salavat Zainetdinovich Imaev; Leonard Makarovich Dmitriev
Original assignee: 3S GAS TECHNOLOGIES Ltd
Current assignee: 3S GAS TECHNOLOGIES Ltd
Priority date: 2004-09-24
Filing date: 2005-09-23
Publication date: 2014-08-19
Anticipated expiration: 2025-09-23
Also published as: BRPI0516049B1; WO2006032139A1; CN101069055A; MX2007003514A; GB0705692D0; AU2005287826B2; NO20071943L; CN101069055B; US20070227186A1; CA2520800A1; UA86266C2; BRPI0516049A; EA200700625A1; RU2272973C1; GB2432413B; EA010564B1; AU2005287826A1; GB2432413A

Abstract

One of the drawbacks common to many currently available low-temperature gas mixture separation techniques is that known systems and methods that embody the techniques are inefficient. In contrast to known systems and methods for low-temperature gas mixture separation, some embodiments of the present invention provide a system for low-temperature gas mixture separation that recycles energy and reduces power consumption by re-circulating heated and/or cooled flows (e.g. gas, liquid and mixed-phase flows) within the system. Accordingly, in some embodiments efficiency is somewhat improved, as compared to comparable systems that do not include the re-circulation of heat energy. In some embodiments the heat energy that is re-circulated is a combination of heat added to the system (i.e. inputs to the system) and heat released within the system (i.e. byproducts from within the system) that are subsequently recovered. In particular, some systems and methods provided in accordance with embodiments of the invention are suited for separating the constituent components of natural gas and other hydrocarbon gas mixtures.

Description

Title: Systems and Methods for Low-Temperature Gas Separation Priority Claim [0001] This application claims the benefit of Russian Patent Application No. 2004128348/06 (030834), filed on September 24, 2004.
Field of the invention [0002] The invention relates to gas separation techniques, and in particular to systems and methods for low-temperature gas separation.
Background of the invention [0003] Existing processes of low temperature separation of the aimed components from the gas mixtures are based on the gas mixtures chilling, aim components condensation and subsequent separation of the condensate, containing the aimed components, from the gas mixture. At this the chilling of a gas mixture is conventionally performed either at the expense of gas expansion in the throttles and expanders or the application of chilling devices.
As additional auxiliary equipment recuperative heat exchangers and rectifying towers are used in the schemes of low temperature gas separation.

[0004] The typical processes of low temperature separation of the aimed components from the gas mixtures are described, for example, in the Patents US6182468B1 and RU2047061C1. The method disclosed in Patent US6182468B1 is based on the gas chilling at the expense of gas mixture throttling in Joule-Thompson valve while in the Patent RU2047061C1 the turbo expander turbine is used for the gas chilling.

[0005] The method of Patent US6182468B1 consists of cooling of a mixture, expansion of the mixture without doing mechanical work, partial condensation of the mixture during its expansion, separation of the mixture or its part in the rectifying tower to obtain the products in liquid and gas phase. In this case, cooling of the mixture is performed using recuperative heat exchangers and a chiller, while expansion of the mixture is achieved by means of mixture throttling in the Joule-Thomson valve.

[0006] The method of Patent RU2047061C1 includes cooling of a mixture and its separation into vapor and liquid phases, expansion of one part of the vapor phase without doing mechanical work and that of the other part by doing mechanical work, separation of the expanded mixture in the rectifying tower to obtain gas and liquid products.

[0007] The essential drawbacks of these methods of low temperature gas separation are the significant mixture pressure losses in the low temperature separation process and high energy consumption.
Summary of the invention [0008] According to an aspect of an embodiment of the invention there is provided a method of low-temperature gas mixture separation, suitable for separating components of a hydrocarbon gas mixture, including: cooling a gas mixture; condensing a gas mixture to produce a liquid stream and a gas/vapor; rectifying at least a portion of the liquid stream thereby producing respective gas-phase products; transferring heat energy to or from at least one of the liquid stream, the gas/vapor stream and gas-phase products from or to at least another one of the gas mixture, the liquid stream, the gas/vapor stream, gas-phase products and another flow in order to recycle energy.

[0009] In some embodiments the method also includes expanding and swirling the gas/vapor stream to produce first and second flows, wherein the first flow primarily includes heavy components of the gas/vapor stream and the second flow primarily includes lighter components of the gas/vapor stream; and transferring heat energy to or from at least one of the liquid stream, the gas/vapor stream, gas-phase products and the first and second flows from or to at least another one of the gas mixture, the liquid stream, the gas/vapor stream, gas-phase products, the another flow and the first and second flows in order to recycle energy.

[0010] In some more specific embodiments the method also includes rectifying at least a portion of the first flow in conjunction with the liquid stream.

[0011] In some more specific embodiments cooling the gas mixture includes at least partially mixing the gas mixture with at least a portion of at least one of the liquid stream, the gas/vapor stream, gas-phase products, the another flow and the first and second flows.

[0012] In some more specific embodiments cooling the gas mixture includes at least partially transferring heat from the gas mixture to at least a portion of at least one of the liquid stream, the gas/vapor stream, gas-phase products, the another flow and the first and second flows.

[0013] In some more specific embodiments the method also includes compressing at least a portion of the gas-phase products.

[0014] In some more specific embodiments the method also includes cooling at least a portion the gas/vapor stream.

[0015] In some more specific embodiments the method also includes compressing at least a portion of the first flow.

[0016] In some more specific embodiments the method also includes compressing at least a portion of the second flow.

[0017] In some more specific embodiments the method also includes cooling at least a portion of the first flow.

[0018] In some more specific embodiments cooling at least a portion of the second flow.

[0019] In some more specific embodiments the transfer of heat energy includes mixing at least a portion of the at least two streams or flows between which the heat is transferred.

[0020] In some more specific embodiments the transfer of heat energy includes exchanging heat energy without mixing the at least two streams or flows between which the heat is transferred.

[0021] In some more specific embodiments the method also includes passing at least a portion of the gas/vapor stream through a turbine.

[0022] In some more specific embodiments the method also includes passing at least a portion of the second flow through a turbine.

[0023] In some more specific embodiments the method also includes condensing at least a portion of the gas-phase products.

[0024] In some more specific embodiments the method also includes further condensing at least a portion of the liquid stream.

[0025] In some more specific embodiments the method also includes condensing at least a portion of the gas/vapor stream.

[0026] In some more specific embodiments the method also includes expanding and swirling at least a portion of the gas-phase products.

[0027] According to an aspect of an embodiment of the invention there is provided a system for low-temperature gas mixture separation, suitable for separating components of a hydrocarbon gas mixture, including: a first gas/liquid separator for separating an incoming gas mixture into a liquid stream and a gas/vapor stream; a first expander, for producing first and second flows, coupled the first gas/liquid separator to receive the gas/vapor stream, the first expander also including a swirling means for swirling the gas/vapor stream to thereby separate heavy components of the gas/vapor stream from the light components of the gas/vapor stream, wherein the heavy components primarily comprise the first flow and the lighter components primarily comprise the second flow; a rectifying tower, for producing at least gas-phase products, coupled to the first gas/liquid separator to receive the liquid stream; and at least one heat exchanger for transferring heat energy to or from at least one of the liquid stream, the gas/vapor stream, gas-phase products and the first and second flows from or to at least another one of the gas mixture, the liquid stream, the gas/vapor stream, gas-phase products, the another flow and the first and second flows in order to recycle energy within the system.

[0028] In some embodiments the first expander is coupled to the rectifying tower to provide at least a portion of the first flow to the rectifying tower.

[0029] In some more specific embodiments the system also includes a first mixer for mixing the incoming gas mixture with a feedback flow, the feedback flow comprising at least a portion of at least one the liquid stream, the gas/vapor stream, gas-phase products, the first and second flows and another flow.

[0030] In some more specific embodiments the system also includes a first compressor for compressing at least a portion of the gas-phase products.

[0031] In some more specific embodiments the system also includes a first compressor for compressing at least a portion of the gas/vapor stream.

[0032] In some more specific embodiments the system also includes a first compressor for compressing at least a portion of the first flow.

[0033] In some more specific embodiments the system also includes a first compressor for compressing at least a portion of the second flow.

[0034] In some more specific embodiments the system also includes a first chiller for cooling at least a portion of the first flow.

[0035] In some more specific embodiments the system also includes a first chiller for cooling at least a portion of the second flow.

[0036] In some more specific embodiments the transfer of heat energy includes mixing at least a portion of the at least two streams or flows between which the heat is transferred.

[0037] In some more specific embodiments the transfer of heat energy includes exchanging heat energy without mixing the at least two streams or flows between which the heat is transferred.

[0038] In some more specific embodiments the system also includes a turbine, for expanding at least a portion of the gas/vapor stream, coupled to the first gas/liquid separator to receive at least a portion of the gas/vapor stream.

[0039] In some more specific embodiments the system also includes a turbine through which at least a portion of the second flow passes, the turbine coupled to receive at least a portion of the second flow.

[0040] In some more specific embodiments the system also includes at least one other gas/liquid separator for separating at least one of a liquid or a gas/vapor stream within the system.

[0041] In some more specific embodiments the system also includes another condenser for further condensing at least a portion of the liquid stream.

[0042] In some more specific embodiments the system also includes another condenser for condensing at least a portion of the gas/vapor stream.

[0043] In some more specific embodiments the system also includes another expander for expanding and swirling at least a portion of the gas-phase products.

[0044] Other aspects and features of the present invention will become apparent, to those ordinarily skilled in the art, upon review of the following description of the specific embodiments of the invention.
Brief description of the drawings [0045] For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, which illustrate aspects of embodiments of the present invention and in which:

[0046] Figure 1 is a schematic drawing of a low-temperature gas mixture separation system according to a first embodiment of the invention;

[0047] Figure 2 is a schematic drawing of a low-temperature gas separation apparatus shown in Figure 1;

[0048] Figure 3 is a schematic drawing of a low-temperature gas mixture separation system according to a second embodiment of the invention;

[0049] Figure 4 is a schematic drawing of a low-temperature gas mixture separation system according to a third embodiment of the invention;

[0050] Figure 5 is a schematic drawing of a low-temperature gas mixture separation system according to a fourth embodiment of the invention;

[0051] Figure 6 is a schematic drawing of a low-temperature gas mixture separation system according to a fifth embodiment of the invention;

[0052] Figure 7 is a schematic drawing of a low-temperature gas mixture separation system according to a sixth embodiment of the invention;

[0053] Figure 8 is a schematic drawing of a low-temperature gas mixture separation system according to a seventh embodiment of the invention;

[0054] Figure 9 is a schematic drawing of a low-temperature gas mixture separation system according to an eighth embodiment of the invention;

[0055] Figure 10 is a schematic drawing of a low-temperature gas mixture separation system according to a ninth embodiment of the invention;

[0056] Figure 11 is a schematic drawing of a low-temperature gas mixture separation system according to a tenth embodiment of the invention;

[0057] Figure 12 is a schematic drawing of a low-temperature gas mixture separation system according to an eleventh embodiment of the invention;

[0058] Figure 13 is a schematic drawing of a low-temperature gas mixture separation system according to a twelfth embodiment of the invention;

[0059] Figure 14 is a schematic drawing of a low-temperature gas mixture separation system according to a thirteenth embodiment of the invention;

[0060] Figure 15 is a schematic drawing of a low-temperature gas mixture separation system according to a fourteenth embodiment of the invention;

[0061] Figure 16 is a schematic drawing of a low-temperature gas mixture separation system according to a fifteenth embodiment of the invention;

[0062] Figure 17 is a schematic drawing of a low-temperature gas mixture separation system according to a sixteenth embodiment of the invention;

[0063] Figure 18 is a schematic drawing of a low-temperature gas mixture separation system according to a seventeenth embodiment of the invention;

[0064] Figure 19 is a schematic drawing of a low-temperature gas mixture separation system according to an eighteenth embodiment of the invention;

[0065] Figure 20 is a schematic drawing of a low-temperature gas mixture separation system according to a nineteenth embodiment of the invention;

[0066] Figure 21 is a schematic drawing of a low-temperature gas mixture separation system according to a twentieth embodiment of the invention;

[0067] Figure 22 is a schematic drawing of a low-temperature gas mixture separation system according to a twenty-first embodiment of the invention; and [0068] Figure 23 is a schematic drawing of a low-temperature gas mixture separation system according to a twenty-second embodiment of the invention.
Detailed description of the invention [0069] In contrast to known systems and methods for low-temperature gas mixture separation, some embodiments of the present invention provide a system for low-temperature gas mixture separation that recycles energy and reduces power consumption by re-circulating heated and/or cooled flows (e.g.
gas, liquid and mixed-phase flows) within the system. Accordingly, in some embodiments efficiency is somewhat improved, as compared to comparable systems that do not include the re-circulation of heat energy. In some embodiments the heat energy that is re-circulated is a combination of heat added to the system (i.e. inputs to the system) and heat released within the system (i.e. byproducts from within the system) that are subsequently recovered. In particular, some systems and methods provided in accordance with embodiments of the invention are suited for separating the constituent components of natural gas and other hydrocarbon gas mixtures.

[0070] In accordance with some embodiments of the invention, a method of low-temperate gas mixture separation includes expansion of a gas mixture without doing mechanical work (i.e. adiabatically expanding the gas mixture), which thereby cools and lowers the pressure of the gas mixture, a step that does not require an addition of energy into the system. Expanding a gas mixture without doing mechanical work can be accomplished by passing the gas mixture through a Joules-Thompson valve or similar device having an expansion valve (or converging-diverging nozzle) that restricts the flow of gas entering an expansion chamber. In accordance with some embodiments of the invention, the gas mixture is also swirled as it enters the gas expanding apparatus. As the swirling gas mixture expands heavier components of the mixture are forced away from a center axis around which the gas mixture is swirling while the lighter components remain near to the center axis. Given the spatial relationship of the heavier swirling components to those of the lighter swirling components, the mixture flow is separated into at least two flows, a first flow that primarily includes the heavier components and a second flow that primarily includes the lighter components of the gas mixture. In some embodiments the heavier components may also condense on the walls of the gas expanding apparatus, thereby facilitating an easier segregation of the first and second flows.

[0071] In one very specific embodiment the first flow (primarily including the heavier components) is at least partially directed to a rectifying tower and the second flow is at least partially directed through a heat-exchanger in order to lower the temperature of an input gas mixture stream. Additionally, in some embodiments the gas-phase products produced in the rectifying tower are compressed, chilled and mixed with the input gas mixture before the input gas mixture arrives at the heat-exchanger.

[0072] In another very specific embodiment the first flow is at least partially directed to a rectifying tower and the second flow is at least partially mixed with the gas-phase products produced in the rectifying tower.
Additionally, in some embodiments the combination of the gas-phase products and the second flow are at least partially directed through a heat-exchanger in order to lower the temperature of an input gas mixture stream.

[0073] In another very specific embodiment the first flow is at least partially mixed with an input gas mixture stream, before the input gas mixture stream is expanded. Additionally, in some embodiments first flow is at least partially directed through a heat-exchanger in order to lower the temperature of an input gas mixture stream. In even more specific embodiments the first flow is also compressed and further chilled before being mixed with the input gas stream. In some such embodiments the second flow (i.e. the lighter flow) is outputted from the system alone or in a suitable combination with some gas-phase products produced elsewhere in the system.

[0074] Referring to Figure 1, shown is a schematic drawing of a low-temperature gas mixture separation system 200 according to a first embodiment of the invention, referred to as the system 200 hereinafter for brevity. Those skilled in the art will appreciate that the system 200 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 200; however, the system 200 is illustrated showing only those elements necessary to describe aspects of this embodiment.
[0076] The system 200 includes a first mixer 30, a first heat-exchanger 32, a first chiller 34 and a gas/liquid separator 36 connected respectively in series. The first mixer 30 includes respective first and second inputs 30a and 30b. The first input 30a serves as an input to the system 200 as a whole as well as an input of the first mixer 30. The second input 30b serves a feedback input, the purpose of which is described in more detail below. The gas/liquid separator 36 has respective first and second outputs 36a and 36b. The first output 36a is a gas/vapor outlet and the second output 36b is a liquid (or mixed-phase) output. In some embodiments the gas/liquid separator 36 is a condenser.
[0076] The system also includes an expander 40 and a rectifying tower 38. The expander 40 is coupled to receive a gas/vapor flow from the first output 36a of the gas/liquid separator 36, whereas the second output 36b of the gas/liquid separator 36 is coupled to deliver a liquid (or mixed-phase) flow to the rectifying tower 38.
[0077] The expander 40 has respective first and second outputs 40a and 40b. The first output 40a is connected to deliver a first flow, of heavier components, to the rectifying tower 38. The second output 40b is coupled back as an input to the first heat-exchanger 32 to cool the gas mixture entering by the first mixer 30.
[0078] The rectifying tower 38 has respective first and second outputs 38a and 38b. The first output 38a is coupled back to the second input 30b of the mixer 30. The system 200 also includes a compressor 42 and a second chiller 44 connected in series between the first output 38a of the rectifying tower and the second input 30b of the mixer 30.
[0079] Before describing the operation of the system 200, more details about the expander 40 are provided with additional reference to Figure 2. The expander 40 has a tubular body with an input end and an output end that are generally indicated by A and B, respectively. The expander 40 includes a swirling means 41 near the input end and a converging-diverging nozzle section 43 following the swirling means 41. In some embodiments the swirling means 41 includes, without limitation, at least one of vanes, an impeller, and fins. The converging-diverging nozzle section 43 flares open into a conical section 45 leading to the output end B. A divider 47 is provided at the output end B within the conical section 45 to facilitate the separation of output flows leading to the respective first and second outputs 40a and 40b.
[0080] The expander 40 can be made both with flow swirling means placed at the nozzle channel entry as shown in Figure 2 (e.g. as discussed in prior art references EP1131588 and US6372019) and with flow swirling means within the nozzle channel (e.g. as discussed in prior art references EP0496128 and W099/01194).
[0081] With reference to Figures 1 and 2, the operation of the system 200 is as follows. An incoming mixture 201 of natural gas (or another gas mixture) enters the system via the mixer 30, where it is mixed with a feedback flow containing the compressed and cooled gas-phase products from the rectifying tower 38. The combination of the input natural gas and feedback gases is further cooled in the first heat-exchanger 32. In accordance with a broad aspect of the invention, the first heat-exchanger 32 facilitates the recycling of heat energy, or rather, in this particular case, the recycling of energy used to cool various flows within the system. That is, the first heat-exchanger 32 cools the incoming natural gas mixture by transferring heat from the natural gas mixture to a feedback flow originating from the second output 40b of the expander 40, which thereby lowers the temperature of the natural gas mixture.
[0082] The natural gas mixture is further cooled in the first chiller before entering into the gas/liquid separator 36. Within the gas/liquid separator 36 the natural gas mixture is separated into a gas/vapor stream and a liquid (or mixed-phase) stream. The gas/vapor stream flows out of the gas/liquid separator 36 via the first output 36a directly into the expander 40.
The liquid stream flows of the gas/liquid separator via the second output 36b directly to the rectifying tower 38.
[0083] The rectifying tower 38 outputs gas-phase products through the first output 38a and liquid phase products through the second output 38b. The gas-phase products are compressed in the compressor 42 and cooled in the second chiller 44 before being mixed with the incoming mixture 201 as described above.
[0084] With specific reference to Figure 2, within the expander 40 the incoming gas/vapor stream is separated into a first flow and a second flow.
The natural gas mixture enters the expander 40, is swirled by the swirling means 41, and expanded through the converging-diverging nozzle section 43.
As the swirling gas mixture expands the heavier components of the mixture drift away from a center axis around which the gas mixture is swirling while the lighter components remain near to the center axis. Given the spatial relationship of the heavier swirling components to those of the lighter swirling components the gas mixture flow is separated into at least the first and second flows, such that the first flow primarily includes the heavier components and the second flow primarily includes the lighter components.
The first flow exits the expander 40 through the first output 40a. The second flow exits the expander 40 through the second output 40b.

[0085] More specifically, in some embodiments during the expansion process, the temperature of the gas/vapor stream is reduced enough to induce partial condensation of the mixture, thus forming a condensate. The condensate drops in the field of centrifugal forces move toward the walls of the expander 40 collecting into a liquid (or two-phase) flow. When the gas mixture is natural gas the first flow contains components that are heavier than methane, whereas the second flow contains substantially more methane gas.
[0086] Moreover, due to the expansion during the swirling motion of the mixture within the expander 40, the static pressure of the mixture is lower than the pressure at the outputs of the expander 40, and the mixture separation within the nozzle occurs at temperatures lower than the temperature of the mixture traveling through the outputs. In some embodiments a deeper mixture separation is provided due to the gas-phase product from the rectifying tower 38 being fed back to the input mixture 201 before the mixture is processed further in the system 200.
[0087] Referring to Figure 3, shown is a schematic drawing of a low-temperature gas mixture separation system 300 according to a second embodiment of the invention, referred to as the system 300 hereinafter for brevity. The system 300 illustrated in Figure 3 is similar to the system 200 illustrated in Figure 1, and accordingly, elements common to both share common reference numerals. Moreover, for the sake of brevity, portions of the description of Figure 1 will not be repeated with respect to Figure 3. Again those skilled in the art will appreciate that the system 300 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 300; however, the system 300 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[0088] The differences between the systems 200 and 300 are as follows. The system 300 does not include the first mixer 30, the first chiller 34, the second chiller 44 and the first compressor 42. The system 300 does include a second mixer 48 and a first (throttling) valve 50. The first valve 50 is coupled between the second output 36b of the gas/liquid separator 36 and the rectifying tower 38. The second mixer 48 includes respective first and second inputs that are coupled to receive and mix the gas/vapor outputs from the expander 40 and the rectifying tower 38. The second mixer 48 also includes an output that is coupled to deliver the gas mixture to the first heat-exchanger 32.
[0089] In operation the incoming mixture 301 is cooled in the first heat-exchanger 32, before passing directly to the separator 36. The liquid stream from the separator 36 is then directed through the throttling valve 50 to the rectifying tower 38. The gas-phase products from the rectifying tower 38 are mixed with the second flow (primarily including the lighter components of the separation process) from the expander 40 in the second mixer 48 to produce a mixed feedback stream. The mixed feedback stream is then passed through the first heat-exchanger 32 in which heat is transferred from the incoming mixture 301 to the feedback stream, thereby cooling the incoming mixture 301 without the addition of energy to the system 300.
[0090] This method makes it possible to reduce required differential pressure of the mixture in the low temperature separation facilities.
[0091] Referring to Figure 4, shown is a schematic drawing of a low-temperature gas mixture separation system 400 according to a third embodiment of the invention, referred to as the system 400 hereinafter for brevity. The system 400 illustrated in Figure 4 is similar to the respective systems illustrated in Figures 1 and 3, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figures 1 and 3 will not be repeated with respect to Figure 4. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 400; however, the system 400 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[0092] The arrangements specifically shown with respect to the system 400 are as follows. The system 400 includes the first mixer 30, as shown in Figure 1. The system 400 also includes the second chiller 44 and the first compressor 42. However, the first compressor 42 and the second chiller 44 are connected between the first heat-exchanger 32 and the second input 30b (i.e. the feedback input) of the first mixer 30. Moreover, the first output 40a of the expander 40 is coupled to the first heat-exchanger 32 instead of being coupled to the rectifying tower 38 as shown in Figure 1.
[0093] In operation the incoming mixture 401 is mixed in the first mixer 30 with the first flow (i.e. the flow primarily including the heavier components of the mixture separated in the expander 40). That is, the first flow from the first output 40a of the expander 40 is mixed with the incoming mixture 401 in order to cool the incoming mixture 401. The mixture outputted from the first mixer 30 is then passed through the first heat-exchanger 32 to further regulate the temperature of the incoming gas mixture. The first heat-exchanger 32 is coupled to receive the first output 40a of the expander 40 as a regulating inflow. By using the feedback system energy is again conserved and efficiency can be improved.
[0094] In some embodiments the gas-phase products output from the rectifying tower 38 are mixed with the second flow outputted from the second output 40b of the expander 40 in the second mixer 48 and the combined mixture cannot be outputted from the system 400.
[0095] Referring to Figure 5, shown is a schematic drawing of a low-temperature gas mixture separation system 500 according to a fourth embodiment of the invention, referred to as the system 500 hereinafter for brevity. The system 500 illustrated in Figure 5 is similar to the respective systems illustrated in Figures 1 and 3-4, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-4 will not be repeated with respect to Figure 5. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 500; however, the system 500 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[0096] The arrangements specifically shown with respect to the system 500 are as follows. The system 500 includes a second heat-exchanger 52.
The second mixer 48 and the second heat-exchanger 52 are connected between the first output 36a of the gas/liquid separator 36 and the input of the expander 40. The second heat-exchanger 52 is also coupled to receive the first flow from the first output 40a of the expander 40 before the first flow is passed to the first heat-exchanger 32, as described with respect to Figure 4.
[0097] In operation the vapor stream from the separator 36 is mixed with the gas-phase output of the rectifying tower 38 in the second mixer 52.
The output of the second mixer 48 is cooled in the second heat-exchanger 52, before being passed through to the expander 40. The first flow (from the first output 40a) from the expander 40 is first sent through the second heat-exchanger 52 to cool the output of the second mixer 48 and then sent through the first heat-exchanger 32 to further cool the output of the first mixer 30.
The same first flow is then compressed in compressor 42, and is then cooled in a second chiller 44 before being mixed with the incoming gas mixture 501. The second flow (from the second output 40b of the expander 40) can be directly output from the system 500. By using the feedback system energy is again conserved and efficiency can be improved.
[0098] In some embodiments the system 500 facilitates a deep purification of the second flow output from the expander 40 (i.e. the flow primarily including lighter components of the gas mixture). That is, when considering the processing of natural gas the second flow may be significantly depleted of the vapor components heavier than methane, since the first flow is mixed with the incoming flow 501.

[0099] Referring to Figure 6, shown is a schematic drawing of a low-temperature gas mixture separation system 600 according to a fifth embodiment of the invention, referred to as the system 600 hereinafter for brevity. The system 600 illustrated in Figure 6 is similar to the respective systems illustrated in Figures 1 and 3-5, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-5 will not be repeated with respect to Figure 6. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 600; however, the system 600 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00100] The arrangements specifically shown with respect to the system 600 are as follows. The system 600 includes a second gas/liquid separator 60. The second gas/liquid separator 60 includes respective first and second outputs 60a and 60b that are coupled to the second mixer 48 and the rectifying tower 38, respectively. The system 600 also includes a second (throttling valve 66) coupled between the second output 60b and an input to the rectifying tower 38. The first output 40a of the expander 40 is coupled to deliver the first flow from the expander 40 to the second gas/liquid separator 60.
[00101] In operation, since there are two gas/liquid separators 36 and 60, liquid separation in the form of condensation is performed twice: before and after various forms of the mixture are expanded in the expander 40. More specifically, the first flow from the expander 40 is sent to a second separator 60, which provides a second vapor stream and a second liquid stream. The second liquid stream passes through a second throttling valve 66 and into the rectifying tower 38. A second vapor stream is mixed with the second flow from the expander 40 in the second mixer 48. The mixture 48 produced in the second mixer 48 is then passed through the first heat-exchanger 32 as described above.
[00102] Referring to Figure 7, shown is a schematic drawing of a low-temperature gas mixture separation system 700 according to a sixth embodiment of the invention, referred to as the system 700 hereinafter for brevity. The system 700 illustrated in Figure 7 is similar to the respective systems illustrated in Figures 1 and 3-6, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-6 will not be repeated with respect to Figure 7. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 700; however, the system 700 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00103] The arrangements specifically shown with respect to the system 700 are as follows. The second heat-exchanger 52 is coupled between the first throttling valve 50 and an input to the rectifying tower 38. The second chiller 44 is coupled between the rectifying tower 38 and the second heat-exchanger 52. More specifically, the second chiller 44 is coupled to receive and cool the gas-phase products from the first output 36a of the rectifying tower 38. The second heat-exchanger 52 is also coupled to the first mixer 30 to provide the cooled gas-phase products from the rectifying tower 38 as a feedback input to the first mixer 30.
[00104] In operation the incoming mixture 701 is mixed with the gas-phase products of the rectifying tower 38 as shown in Figure 1, however the gas-phase products are first cooled by the second chiller 44 and the second heat-exchanger 52 before mixing with the incoming mixture 701. In turn, the second heat-exchanger 52 heats the first flow (i.e. the heavy output flow) from the expander 40 before the first flow is delivered into the rectifying tower 38.

This arrangement helps provide a more rational distribution of mass and enthalpy flows in the low-temperature separation process.
[00105] Referring to Figure 8, shown is a schematic drawing of a low-temperature gas mixture separation system 800 according to a seventh embodiment of the invention, referred to as the system 800 hereinafter for brevity. The system 800 illustrated in Figure 8 is similar to the respective systems illustrated in Figures 1 and 3-7, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-7 will not be repeated with respect to Figure 8. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 500; however, the system 800 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00106] The arrangements specifically shown with respect to the system 800 are as follows. Liquid separation by condensation is facilitated twice before expansion in the expander 40. To that end, the second gas/liquid separator 60 is coupled to receive the combination of the liquid (or two phase output) from the first gas/liquid separator 36 and the gas-phase products from the rectifying tower 38. Moreover, the gas-phase products from the rectifying tower 38 are first coupled through the second heat-exchanger 52 that also receives the liquid phase (or two phase) output of the second separator 60, so that heat energy can be transferred between the two, thereby cooling one and heating the other in order to recycle energy within the system 800.
[00107] The incoming mixture 801 is cooled in the first heat-exchanger 32 and further cooled in the first chiller 34 before entering the first gas/liquid separator 36. The liquid stream from the separator 36 is passed through a throttling valve 50 and is mixed with the gas-phase products of the rectifying tower 38 before entering the second gas/liquid separator 60. The second gas/liquid separator 60 also provides a second liquid stream, which passes through the second heat-exchanger 52, thereby cooling the gas-phase products and heating the second liquid stream. After passing through the second heat-exchanger 52 the second liquid stream is coupled into the rectifying tower 38. Elsewhere in the system, the gas/vapor streams from the first and second separators 36 and 60 are combined in the second mixer 48 before being delivered to the expander 40 where the mixture undergoes the process above described with respect to Figures 1 and 2 to produce the first and second flows. This method allows a deeper purification of the second flow by removing a greater proportion of components heavier than methane when natural gas is being processed.
[00108] Referring to Figure 9, shown is a schematic drawing of a low-temperature gas mixture separation system 900 according to an eighth embodiment of the invention, referred to as the system 900 hereinafter for brevity. The system 900 illustrated in Figure 9 is similar to the respective systems illustrated in Figures 1 and 3-8, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-8 will not be repeated with respect to Figure 9. Those skilled in the art will appreciate that the system includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 900; however, the system 900 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00109] The arrangements specifically shown with respect to the system 900 are as follows. The first chiller 34 precedes the first heat-exchanger 32.
A
third heat-exchanger 62 is coupled in series between the first heat-exchanger 32 and the first gas/liquid separator 36. The third heat-exchanger 62 is also coupled to receive a portion of the liquid (or two phase) stream from the first gas/liquid separator 36. To that end, the second throttling valve 66 is coupled between the second output 36b and the third heat-exchanger 62 to prevent a reversal of flow and maintain a forward pressure through the third heat-exchanger 62. Also, similar to the system 500 shown in Figure 5, the gas-phase products from the rectifying tower 38 are combined with the gas/vapor stream from the first gas/liquid separator 36 in the mixer 48 before expansion.
To that end, and as similar to Figure 8, the second heat-exchanger 52 is coupled between the first output 38a of the rectifying tower 38 and the second mixer 48. The second heat-exchanger 52 also receives a portion of the liquid stream from the first gas/liquid separator 36, with the first throttling valve connected there between.
[00110] In operation a portion of the liquid stream from the first gas/liquid separator 36 is used to cool the incoming mixture 901. The incoming mixture 901 is cooled through the first chiller 34 and then is mixed with a portion of the liquid stream from the first gas/liquid separator 36 as described in more detail below. The resulting mixture is further cooled in the first heat-exchanger 32 and in a third heat-exchanger 62 before entering the first gas/liquid separator 36. As should be understood by now, the first gas/liquid separator 36 produces a gas/vapor stream and a liquid (or two-phase) stream. The gas/vapor stream is mixed in the second mixer 48 with the gas-phase products from the rectifying tower 38, and the resulting gas/vapor mixture is expanded and separated into the first and second flows as described above with respect to Figures 1 and 2. The first flow is coupled into the rectifying tower 38 and the second flow is coupled back to the first heat-exchanger 32.
Again, as for the systems described previously, the heat-exchangers facilitate the recycling of energy within the system 900 thereby improving the efficiency of the system 900.
[00111] Referring to Figure 10, shown is a schematic drawing of a low-temperature gas mixture separation system 1000 according ninth to a ninth embodiment of the invention, referred to as the system 1000 hereinafter for brevity. The system 1000 illustrated in Figure 10 is similar to the respective systems illustrated in Figures 1 and 3-9, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-9 will not be repeated with respect to Figure 10. Those skilled in the art will appreciate that the system 1000 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1000; however, the system 1000 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00112] The arrangements specifically shown with respect to the system 1000 are as follows. The system 1000 includes a turbine 70 connected between the second output 40b of the expander 40 and the first heat-exchanger 32. The addition of the turbine 70 effectively modifies the expander 40 to create a turbo-expander. The system 1000 also includes a second compressor 64 connected in series between the first compressor 42 and the second input 30b of the first mixer 30.
[00113] In operation the second flow, coupled from the second output 40b of the expander 40, passes through the turbine 70 and is then sent back through the first heat-exchanger 32 to the incoming mixture 1001. In some embodiments a turbo-expander may be used to provide additional expansion, either before or after the mixture passes through the expander 40.
Additionally, the incoming mixture 1001 is mixed with a feed back gas/vapor stream that includes portions of the liquid stream of the first gas/liquid separator 36 and portions of the gas/vapor stream from the second gas/liquid separator 60. The resulting mixture is then cooled in the first heat-exchanger 32 before entering the first gas/liquid separator 36. The liquid stream of the first gas/liquid separator 36 is split into a first portion and a second portion.
The first portion passes through a throttling valve 50 and into the rectifying tower 58. The second portion of the first liquid stream is passed through a second throttling valve 66 before mixing with the gas/vapor stream of the second gas/liquid separator 60. By contrast, the gas/vapor stream from the first gas/liquid separator 36 passes through the second heat-exchanger 52 where it is cooled before entering second mixer 48. The second mixer also receives the gas-phase products from the rectifying tower 38. The output of the second mixer 48 is then coupled into the expander 40 as described above. The first flow from the expander 40 is directed into the second gas/liquid separator 60. The second separator 66 also provides the liquid stream which it produces directly to the rectifying tower 38.
[00114] By employing the turbine 70 as described with the second flow from the expander 40 the service life of the turbine blades (not shown) is extended because the quantity of condensate (drops) in flow over the blades is decreased, thereby resulting in less wear.
[00115] Referring to Figure 11, shown is a schematic drawing of a low-temperature gas mixture separation system 1100 according to a tenth embodiment of the invention, referred to as the system 1100 hereinafter for brevity. The system 1100 illustrated in Figure 11 is similar to the respective systems illustrated in Figures 1 and 3-10, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-10 will not be repeated with respect to Figure 11. Those skilled in the art will appreciate that the system 900 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1100; however, the system 1100 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00116] The arrangements specifically shown with respect to the system 1100 are as follows. Again, the first input 30a to the first mixer 30 serves as an input to the system 1100 as well as an input to the first mixer 30. The first compressor 42 is coupled in series between the first mixer 30 and the first chiller 34, which is in turn coupled in series to the first heat-exchanger 32.
The first and second outputs of the first heat-exchanger 32 are connected to the first gas/liquid separator 36 and the second compressor 64 respectively. The second output 36b of the first gas/liquid separator 36 is coupled to the parallel combination of first and second throttling vales 50 and 66, which are in turn connected to the rectifying tower 38 and the second heat-exchanger 52, respectively. That is, the liquid (two-phase) stream from the first gas/liquid separator is divided between the second heat-exchanger 52 and the rectifying tower. The second heat-exchanger 52 is also coupled to receive the gas/vapor stream output of the first gas/liquid separator before the gas/vapor stream enters the expander.
[00117] The system 1100 is particularly useful when, in operation, the incoming mixture 1101 enters at a relatively low differential pressure. More specifically, the incoming mixture 1101 is mixed with the second flow separated in the expander 40. The resulting combined mixture is then compressed in a first compressor 42 before being cooled in the first chiller and the first heat-exchanger 32.
[00118] The liquid stream from the first gas/liquid separator 36 is split into a first portion, which passes through a first throttling valve 50 into the rectifying tower 38, and a second portion that passes through the second throttling valve 66 into the second heat-exchanger 52. After traveling through the second heat-exchanger 52, the second portion enters the second mixer 48, where it is mixed with the gas-phase products of the rectifying tower 38.
The combination is then fed back to the first mixer 30 to be mixed with the incoming mixture 1101, as described above. The gas/vapor stream 36 from the first separator is sent to the expander 40 and undergoes the process described above with respect to Figures 1 and 2.
[00119] Referring to Figure 12, shown is a schematic drawing of a low-temperature gas mixture separation system 1200 according to an eleventh embodiment of the invention, referred to as the system 1200 hereinafter for brevity. The system 1200 illustrated in Figure 12 is similar to the respective systems illustrated in Figures 1 and 3-11, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-11 will not be repeated with respect to Figure 12. Those skilled in the art will appreciate that the system 1200 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1200; however, the system 1200 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00120] The arrangements specifically shown with respect to the system 1200 are as follows. The gas/vapor stream of the first gas/liquid separator 36 is split into two streams. The first stream is coupled into the expander 40.
The second stream is coupled into the turbine 70 that is placed in parallel with the expander 40. The first output 40a of the expander 40 and the output of the turbine 70 meet at the second mixer 48 that is in turn coupled to the rectifying tower 38. The second output 40b of the expander 40 and the first output 38a of the rectifying tower meet at the third mixer 68 that is in turn connected in series to the second heat-exchanger 52 and the second compressor 64. The system 1200 is suitable for situations in which it is desirable to provide increased pressure within the system to improve the effectiveness of the mixture separation.
[00121] In operation after mixing of the incoming mixture 1201 with a portion of the liquid stream from the first gas/liquid separator 36, the resulting mixture is compressed in the compressor 42 and cooled in the first chiller 34 and the first heat-exchanger 32. Another portion of the liquid stream from the first gas/liquid separator 36, is passed through the throttling valve 50 and into the rectifying tower 38. The gas/vapor stream of the first gas/liquid separator 36 is also split into two portions. The first portion is directed into the turbine 70 and the second portion is directed into the expander 40. The first flow from the expander 40 and the output of the turbine 70 are mixed and delivered to the rectifying tower 38. The second flow is mixed with the gas-phase products from the rectifying tower 38 and passes through the second heat-exchanger 52 and compressor 64 before exiting the system.
[00122] Referring to Figure 13, shown is a schematic drawing of a low-temperature gas mixture separation system 1300 according to a twelfth embodiment of the invention, referred to as the system 1300 hereinafter for brevity. The system 1300 illustrated in Figure 13 is similar to the respective systems illustrated in Figures 1 and 3-12, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-12 will not be repeated with respect to Figure 13. Those skilled in the art will appreciate that the system 1300 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1300; however, the system 1300 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00123] The arrangements specifically shown with respect to the system 1300 are as follows. The system 1300 includes a second expander 80 similar in design and function to the expander 40 described above with respect to Figure 2. Analogous to the first expander 40, the expander 80 has respective first and second outputs 80a and 80b. The first output 80a is connected to deliver a first flow, of heavier components, to the second gas/liquid separator 60, and the second output 40b is coupled to combine a second flow, of lighter components, with the gas/vapor stream of the second gas/liquid separator 60.
The system 1300 also includes a pump 72 and a third throttling valve 74 connected in series between the liquid (or two-phase) stream (i.e. the second output 60b) of the second gas/liquid separator 60 and the third heat-exchanger 62, which is in turn coupled to the rectifying tower 38. The gas-phase products from the rectifying tower 38 are also coupled through the third heat-exchanger 62.
[00124] In operation the gas-phase products from the rectifying tower are cooled, expanded (in the second expander 80) and separated, and the resulting second flow from the second expander 80 is directed, either partially or totally, back to the rectifying tower 38.
[00125] Referring to Figure 14, shown is a schematic drawing of a low-temperature gas mixture separation system 1400 according to a thirteenth embodiment of the invention, referred to as the system 1400 hereinafter for brevity. The system 1400 illustrated in Figure 14 is similar to the respective systems illustrated in Figures 1 and 3-13, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-13 will not be repeated with respect to Figure 14. Those skilled in the art will appreciate that the system 1400 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1400; however, the system 1400 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00126] The arrangements specifically shown with respect to the system 1400 are as follows. The system 1400 includes a cooling and compression loop connected between the first output 38a of the rectifying tower 38 and the input of the second gas/liquid separator 60 that includes a third heat-exchanger 76, the second compressor 64 and second chiller 44 connected in series. The output of the second chiller 44 is then connected in a feedback loop through the third heat-exchanger 76. The first output 60a (i.e. the gas/vapor output) of the second gas/liquid separator 60 is coupled to the second expander 80. The first output 80a (containing the heavier of the separated components from the expansion and separation process) of the expander 80 is coupled to the rectifying tower 38 and the second output 80b is combined with the second output 40b of the expander 40.
[00127] In operation the gas-phase products from the rectifying tower are chilled and compressed in the aforementioned cooling and compression loop. Specifically, the gas-phase products from the rectifying tower 38 are cooled in the heat-exchanger 76, compressed in the compressor 64, cooled in the chiller 44, and further cooled in second heat-exchanger 62 before entering into the second gas/liquid separator 60. The liquid stream from the second gas/liquid separator 60 also passes through the second heat-exchanger 162 before entering into the rectifying tower 38. The operation of the rest of the system 1400 is analogous to that of the system 1300 illustrated in Figure 13.

[00128] Referring to Figure 15, shown is a schematic drawing of a low-temperature gas mixture separation system 1500 according to a fourteenth embodiment of the invention, referred to as the system 1500 hereinafter for brevity. The system 1500 illustrated in Figure 15 is similar to the respective systems illustrated in Figures 1 and 3-14, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-14 will not be repeated with respect to Figure 15. Those skilled in the art will appreciate that the system 1500 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1500; however, the system 1500 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00129] The arrangements specifically shown with respect to the system 1500 are as follows. In system 1500 the first output 38a of the rectifying tower 38 is coupled to the input of second expander 80 via the second chiller 44.
The first output 80a of the expander 80 is coupled to the second gas/liquid separator 60. In turn, as also shown in Figure 14, the liquid (or two-phase) output of the separator 60 is coupled into the rectifying tower 38.
[00130] In operation the gas-phase products from the rectifying tower 38 are expanded within the second expander 80 to separate heavy and light components from one another as described above with respect to Figure 2.
The first flow (containing the heavier components) from the first output 80a of the second expander 80 passes into the second gas/liquid separator 60. The liquid (or two-phase) output is pumped into the rectifying tower 38 through pump 72 and the third throttling valve 74. The second output 80b of the expander 80 is combined with the gas/vapor stream output from the second separator 60 and the second output 40b of the expander 40. The resulting mixture is fed back to the first heat-exchanger 32 to cool the incoming mixture 1501. The incoming mixture 1501, having been mixed with a feedback flow as described previously, is also compressed before entering the first gas/liquid separator 36. The remaining operations are similar to the systems described previously.
[00131] Referring to Figure 16, shown is a schematic drawing of a low-temperature gas mixture separation system 1600 according to a fifteenth embodiment of the invention, referred to as the system 1600 hereinafter for brevity. The system 1600 illustrated in Figure 16 is similar to the respective systems illustrated in Figures 1 and 3-15, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-15 will not be repeated with respect to Figure 16. Those skilled in the art will appreciate that the system 1600 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1600; however, the system 1600 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00132] The arrangements specifically shown with respect to the system 1600 are as follows. Unlike the system 1500, the system 1600 only includes the first gas/liquid separator 36. The third heat-exchanger 62 is connected in series between the first output 38a of the rectifying tower 38 and the input of the second expander 80. The first output 80a of the expander 80 is fed back and coupled through the third heat-exchanger 62 via the third throttling valve 74 and through the second heat-exchanger 52, which is in turn coupled back to the first mixer 30 [00133] In operation the first flow separated in the second expander travels through the third and second heat-exchangers 62 and 52, respectively before being combined with the incoming mixture 1601. The liquid (or two-phase) output stream from the first gas/liquid separator 36 is also combined with the first flow separated in the second expander 80 before the second heat-exchanger 52. The second throttling valve 66 prevents back flow of the liquid output stream to the first gas/liquid separator 36. The remaining elements operate as discussed with respect to Figure 15.

[00134] Referring to Figure 17, shown is a schematic drawing of a low-temperature gas mixture separation system 1700 according to a sixteenth embodiment of the invention, referred to as the system 1700 hereinafter for brevity. The system 1700 illustrated in Figure 17 is similar to the respective systems illustrated in Figures 1 and 3-16, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-16 will not be repeated with respect to Figure 17. Those skilled in the art will appreciate that the system 1700 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1700; however, the system 1700 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00135] The arrangements specifically shown with respect to the system 1700 are as follows. The system 1700 includes four gas/liquid separators, namely, the first and second gas/liquid separators 36 and 60 and additionally third and fourth gas/liquid separators 82 and 84. The first and second gas/liquid separators 36 and 60 are connected such that the gas/vapor output of the first gas/liquid separator 36 is coupled into the second gas/liquid separator 60. The turbine 70 and second mixer 48 are connected there between, as illustrated in Figure 17. The liquid outputs of the first and second gas/liquid separators 36 and 60 are combined and coupled to the third separator 82. The liquid output of the third separator 82 is coupled to the fourth separator 84 via the second heat-exchanger 52. The liquid output of the fourth gas/liquid separator 84 is coupled to the rectifying tower 38 and the gas/vapor output is coupled through the second mixer 48 to the second gas/liquid separator 60 along with the gas/vapor output of the third gas/liquid separator 82. The gas/vapor output stream of the second gas/liquid separator 60 is coupled into the expander 40. The compressor stage of the turbo-expander can be used as compressor 42, and this scheme makes it possible to improve power consumption in the process of low-temperature separation.

[00136] In operation the incoming mixture 1701 is cooled by the series combination of the first and second heat-exchangers 32 and 52 before entering the first gas/liquid separator 36. The liquid streams from the first and second gas/liquid separator 36, 60 are combined and directed into the third gas/liquid separator 82 along with the first flow produce by the expander 40.
The third gas/liquid separator 82 produces a liquid stream that is used as a coolant in the second heat-exchanger 52 before being further processed in the fourth gas/liquid separator 84. The liquid stream produced by the fourth gas/liquid separator 84 is then delivered to the rectifying tower 38. The gas/vapor streams from the third and fourth gas/liquid separators 82 and 84 are combined and fed back to the second gas/liquid separator 60 along with the gas/vapor stream from the first gas/liquid separator.
[00137] Referring to Figure 18, shown is a schematic drawing of a low-temperature gas mixture separation system 1800 according to a seventeenth embodiment of the invention, referred to as the system 1800 hereinafter for brevity. The system 1800 illustrated in Figure 18 is similar to the respective systems illustrated in Figures 1 and 3-17, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-17 will not be repeated with respect to Figure 18. Those skilled in the art will appreciate that the system 1800 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1800; however, the system 1800 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00138] The arrangements specifically shown with respect to the system 1800 are as follows. The liquid stream output 36h of the first gas/liquid separator 36 is coupled to both the rectifying tower 38 and the third heat-exchanger 62. The third heat-exchanger 62 is coupled in series between the first heat-exchanger 32 and the first gas/liquid separator 36. Moreover, the third heat exchange 62 couples the liquid stream output 36b back to the first mixer 30 via the first compressor 42 and the second chiller 44.
[00139] In operation a portion of the liquid stream from the first gas/liquid separator 36 is used to cool the incoming mixture 1701, as shown by example in Figure 18. The incoming mixture 1701 is cooled through the first chiller 34 and then mixed with a portion of the liquid stream from the first gas/liquid separator 36. That portion of the liquid stream, however, is first used as a coolant in the third heat-exchanger 62 and then compressed and chilled before being added to the incoming mixture 1701. The remaining portions of the system operate as described with respect to Figure 3.
[00140] Referring to Figure 19, shown is a schematic drawing of a low-temperature gas mixture separation system 1900 according to an eighteenth embodiment of the invention, referred to as the system 1900 hereinafter for brevity. The system 1900 illustrated in Figure 19 is similar to the respective systems illustrated in Figures 1 and 3-18, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-18 will not be repeated with respect to Figure 19. Those skilled in the art will appreciate that the system 1900 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 1900; however, the system 1900 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00141] The arrangements specifically shown with respect to the system 1900 are as follows. The gas/vapor stream of the first gas/liquid separator 36 is split into two streams. The first stream is coupled into the expander 40.
The second stream is coupled into the turbine 70 that is placed in parallel with the expander 40. The first output 40a of the expander 40 and the output of the turbine 70 are coupled into the rectifying tower 38. The second output 40b of the expander 40 and the first output 38a of the rectifying tower meet at the second mixer 48 that is in turn connected in series to the first heat-exchanger 32. The system 1900 is suitable for situations in which it is desirable to provide increased pressure within the system to improve the effectiveness of the mixture separation.
[00142] In operation incoming mixture 1901 is cooled in the first heat-exchanger 32 and separated in the first gas/liquid separator 36. The liquid stream 16 passes through a valve 42 and into the rectifying tower 18. Before expansion, the gas/vapor stream produced by the first gas/liquid separator 36 is separated into at least two flows, one of which is pumped through a turbo-expander turbine 70 and directed to the rectifying tower 38, and the other flow is expanded through the expander 40. The first flow from the expander 40 is sent to the rectifying tower 38, while the second flow is mixed with the gas-phase products from the rectifying tower 38, the combination of which is sent through the first heat-exchanger 32 and outputted after being compressed in the first compressor 42. This method is applicable for deeper purification of the mixture and for substantially removing heavier components from the mixture.
[00143] Referring to Figure 20, shown is a schematic drawing of a low-temperature gas mixture separation system 2000 according to a nineteenth embodiment of the invention, referred to as the system 2000 hereinafter for brevity. The system 2000 illustrated in Figure 20 is similar to the respective systems illustrated in Figures 1 and 3-19, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-19 will not be repeated with respect to Figure 20. Those skilled in the art will appreciate that the system 2000 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 2000; however, the system 2000 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00144] The arrangements specifically shown with respect to the system 2000 are as follows. The system 2000 is almost identical to the system 1900 with the exception that the compressor 42 is not included. In operation this system 2000, as well as system 1900, may facilitates improved efficiency of the turbo-expander turbine 70, thus providing for deeper gas cooling in the turbine 70 and allowing for a greater compression ratio.
[00145] Referring to Figure 21, shown is a schematic drawing of a low-temperature gas mixture separation system 2100 according to a twentieth embodiment of the invention, referred to as the system 2100 hereinafter for brevity. The system 2000 illustrated in Figure 21 is similar to the respective systems illustrated in Figures 1 and 3-20, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-20 will not be repeated with respect to Figure 20. Those skilled in the art will appreciate that the system 2100 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 2100; however, the system 2100 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00146] The arrangements specifically shown with respect to the system 2100 are as follows. The first output 36a of the first gas/liquid separator 36 is split between the turbine 70, the expander 40 and the third mixer 68. The third mixer 68 also receives the first flow from the expander 40 and the gas-phase products from the rectifying tower 38.
[00147] In operation the gas/vapor stream produced by the first separator 36 is divided into three portions that are passed to the turbine 70, the expander 40 and the third mixer 68, respectively. The remaining components operate as discussed with reference to Figures 19 and 20. This method makes it possible to stabilize the mass flow rate through the turbo-expander turbine 70 in case of variations in the incoming mixture 2101.
[00148]
Referring to Figure 22, shown is a schematic drawing of a low-temperature gas mixture separation system 2200 according to a twenty-first embodiment of the invention, referred to as the system 2200 hereinafter for brevity. The system 2200 illustrated in Figure 15 is similar to the respective systems illustrated in Figures 1 and 3-21, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-21 will not be repeated with respect to Figure 22. Those skilled in the art will appreciate that the system 2200 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 2200; however, the system 2200 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00149] The arrangements specifically shown with respect to the system 2200 are as follows. The second output (i.e. the liquid output) 36b of the first gas/liquid separator and the first output 40a of the expander 40 are coupled into the second mixer 48, which is in turn coupled to the first heat-exchanger 32.
[00150] In operation the resulting combination of the liquid output of the first gas/liquid separator 26 and the first flow from the expander 40 is used to cool the incoming mixture 2201 within the first heat-exchanger 32, as well as being added to the incoming mixture 2201 within the first mixer 30. This method can be effective in cases where the gas-phase products produced by the rectifying tower 38 contain relatively light components from the incoming mixture 2201. For example, when processing natural gas the gas-phase products produced by the rectifying tower 38 may have very low amounts of components that are heavier than methane.
[00151] Referring to Figure 23, shown is a schematic drawing of a low-temperature gas mixture separation system 2300 according to a twenty-second embodiment of the invention, referred to as the system 2300 hereinafter for brevity. The system 2300 illustrated in Figure 23 is similar to the respective systems illustrated in Figures 1 and 3-22, and accordingly, elements common to each share common reference numerals. Moreover, for the sake of brevity, portions of the descriptions for Figure 1 and 3-22 will not be repeated with respect to Figure 23. Those skilled in the art will appreciate that the system 2300 includes a suitable combination of associated structural elements, mechanical systems, hardware, firmware and software that is employed to support the function and operation of the system 2300; however, the system 2300 is illustrated showing only those elements necessary to describe aspects of this embodiment of the invention.
[00152] The arrangements specifically shown with respect to the system 2300 are as follows. A portion of the second output 36b of the first gas/liquid separator 36 and the first output 40a of the expander 40 are connected and coupled through the second and the third heat-exchangers 52 and 62. The first output 38a of the rectifying tower 38 is also coupled with the corresponding output of the third heat-exchanger 62 and then coupled into the first compressor 42. The first compressor 42 is then coupled in series to through the second chiller 44 to the first mixer 30 that also accepts the incoming mixture 2301.
[00153] In operation a portion of the liquid output from the first gas/liquid separator 36 is combined with the first flow produced by the expander 40. The combination is used to chill the gas/vapor stream from the first gas/liquid separator 36 in the second heat-exchanger 52 and the incoming mixture 2301 in the third heat-exchanger 62 before being combined with the incoming mixture 2301 in the mixer 30. The system 2300 is suitable for processing gas mixtures in which the concentration of the target components is low in the incoming mixture.
[00154] What has been described is merely illustrative of the application of the principles of the invention. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the following claims, the invention may be practiced otherwise than as specifically described herein.

Claims

1. A method of low-temperature separation of a mixture of hydrocarbon gases, which includes cooling of the mixture, expansion of the mixture or its part without doing mechanical work, partial condensation of the mixture during its expansion, separation of the mixture or its part in a rectifying tower to obtain products in liquid and gas phase, wherein the process of the mixture expansion is implemented by passing the mixture through a nozzle channel such that in the nozzle channel and/or at an entry of the nozzle channel the mixture flow is swirled, flows through a converging-diverging nozzle section of the nozzle channel, and at an exit of the nozzle channel or its part the mixture flow is separated based on a spatial relationship of heavier swirling components and lighter swirling components into, at least, two flows, one of which is enriched in components heavier than methane, while the other flow is depleted in these components; the enriched flow is directed, either partially or totally, to the rectifying tower, and the gas-phase products, obtained in the rectifying tower, are directed, either partially or totally, to the mixture before its expansion.

2. The method as claimed in claim 1, wherein after the separation of the flows at least one of them is compressed by passing the flow through a diffuser.

3. The method as claimed in claim 1, wherein before expansion the mixture or its part is mixed in an ejector with the gas-phase products coming from the rectifying tower.

4. The method as claimed in claim 1, wherein before expansion and/or after it the liquid phase is separated from the mixture or its part, which is passed through a throttling valve, and the products obtained after the valve are directed, either partially or totally, to the rectifying tower.

5. The method as claimed in claim 1, wherein the gas-phase products, coming from the rectifying tower, are cooled additionally.

6. The method as claimed in claim 4, wherein at least part of the gas-phase products, coming from the rectifying tower, is directed to the mixture before its expansion together with part of the products obtained after the throttling valve.

7. The method as claimed in claim 4, wherein at least part of the liquid phase separated from the mixture is used for additional cooling of the mixture or its part and directed to the mixture before its expansion.

8. The method as claimed in claim 6 or 7, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

9. The method as claimed in claim 8, wherein before expansion the mixture is additionally compressed in a compressor.

10. The method as claimed in claim 1, wherein after mixing with the products directed to the initial mixture before its expansion, the obtained mixture is additionally compressed in a compressor.

11. The method as claimed in claim 10, wherein the gas-phase products, coming from the rectifying tower, are cooled and expanded, and part of the products enriched in components heavier than methane is separated, which is directed, either partially or totally, to the rectifying tower.

12. The method as claimed in claim 11, wherein the gas-phase products, coming from the rectifying tower, are additionally compressed in the compressor before cooling.

13. The method as claimed in claim 12, wherein the gas-phase products, coming from the rectifying tower, are expanded to obtain the products enriched in components heavier than methane, the latter is directed, either partially or totally, to the rectifying tower or returned to the flow of gas-phase products before its expansion.

14. The method as claimed in claim 13, wherein part of the products enriched in components heavier than methane, which are obtained after expansion of the gas-phase products, is returned to the initial mixture before its expansion.

15. The method as claimed in claim 5, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

16. A method of low-temperature separation of a mixture of hydrocarbon gases, which includes cooling of the mixture, expansion of the mixture or its part without doing mechanical work, partial condensation of the mixture during its expansion, separation of the mixture or its part in a rectifying tower to obtain products in liquid and gas phase, wherein the process of the mixture expansion is implemented by passing the mixture through a nozzle channel such that in the nozzle channel and/or at an entry of the nozzle channel the mixture flow is swirled, flows through a converging-diverging nozzle section of the nozzle channel, and at an exit of the nozzle channel or its part the mixture flow is separated based on a spatial relationship of heavier swirling components and lighter swirling components into, at least, two flows, one of which is enriched in components heavier than methane, while the other flow is depleted in these components; the enriched flow is directed, either partially or totally, to the rectifying tower, and the gas-phase products, coming from the rectifying tower, are mixed, either partially or totally, with the depleted flow.

17. The method as claimed in claim 16, wherein after separation of the flows, at least one of them is compressed by passing the flow through a diffuser.

18. The method as claimed in claim 16, wherein before and/or after expansion the liquid phase is separated from the mixture or its part, which is passed through a throttling valve, and the products obtained after the valve are directed, either partially or totally, to the rectifying tower.

19. The method as claimed in claim 16, wherein the gas-phase products, coming from the rectifying tower, are cooled additionally.

20. The method as claimed in claim 18, wherein at least part of the gas-phase products, coming from the rectifying tower, is directed to the mixture before its expansion together with part of the products obtained after the throttling valve.

21. The method as claimed in claim 18, wherein at least part of the liquid phase separated from the mixture is used for additional cooling of the mixture or its part and directed to the mixture before its expansion.

22. The method as claimed in claim 16, wherein during the process of expansion or after it the liquid phase is separated from the mixture, which is passed through a throttling valve, and part of the products, obtained after the throttling valve, is used to cool the mixture or its part and directed to the mixture before its expansion.

23. The method as claimed in claim 16, wherein the mixture flow is separated into, at least, two parts, one of which is pumped through a turbo-expander turbine and directed to the rectifying tower, while the other part is expanded in the swirled flow passed through the nozzle channel to obtain part of the flow enriched in components heavier than methane, the enriched flow is directed to the rectifying tower.

24. The method as claimed in claim 23, wherein the enriched flow, obtained during the process of expansion, and the flow, passed through the turbo-expander turbine, are mixed in an ejector.

25. The method as claimed in claim 23, wherein the mixture flow is separated into, at least, three flows, one of which is directed through the valve with the controlled mass flow rate to the rectifying tower or mixed with the products coming from the rectifying tower in gas phase.

26. The method as claimed in claim 16 or 22, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

27. The method as claimed in claim 26, wherein before expansion the mixture is compressed additionally in a compressor.

28. The method as claimed in any one of claims 16, 22, 24, 25, wherein after mixing with the products directed to the initial mixture before its expansion, the obtained mixture is compressed additionally in a compressor.

29. The method as claimed in claim 28, wherein the gas-phase products, coming from the rectifying tower, are cooled and expanded, and part of the products enriched in components heavier than methane is separated, which is directed, either partially or totally, to the rectifying tower.

30. The method as claimed in claim 29, wherein the gas-phase products, coming from the rectifying tower, are compressed additionally in the compressor before cooling.

31. The method as claimed in claim 30, wherein the gas-phase products, coming from the rectifying tower, are expanded to obtain the products enriched in components heavier than methane, the latter is directed, either partially or totally, to the rectifying tower or returned to the flow of gas-phase products before its expansion.

32. The method as claimed in claim 31, wherein part of the products, enriched in components heavier than methane, which are obtained after expansion of the gas-phase products, is returned to the initial mixture before its expansion.

33. The method as claimed in claim 19, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

34. A method of low-temperature separation of a mixture of hydrocarbon gases, which includes cooling of the mixture, expansion of the mixture or its part without doing mechanical work, partial condensation of the mixture during its expansion, separation of the mixture or its part in a rectifying tower to obtain the products in liquid and gas phase, wherein the process of the mixture expansion is implemented by passing the mixture through a nozzle channel such that in the nozzle channel and/or at an entry of the nozzle channel the mixture flow is swirled, flows through a converging-diverging nozzle section of the nozzle channel, and at an exit of the nozzle channel or its part the mixture flow is separated based on a spatial relationship of heavier swirling components and lighter swirling components into, at least, two flows, one of which is enriched in components heavier than methane, while the other flow is depleted in these components; the enriched flow is directed, either partially or totally, to the mixture before its expansion, and the gas-phase products, coming from the rectifying tower, are mixed, either partially or totally, with the depleted flow.

35. The method as claimed in claim 34, wherein after separation of the flows at least one of them is compressed by passing the flow through a diffuser.

36. The method as claimed in claim 34, wherein before expansion or after it the liquid phase is separated from the mixture or its part, which is passed through a throttling valve, and the products, obtained after the valve, are directed, either partially or totally, to the rectifying tower.

37. The method as claimed in claim 34, wherein the gas-phase products, coming from the rectifying tower, are cooled additionally.

38. The method as claimed in claim 36, wherein at least part of gas-phase products, coming from the rectifying tower, is directed to the mixture before its expansion together with part of the products obtained after the throttling valve.

39. The method as claimed in claim 36, wherein at least part of the liquid phase separated from the mixture is used for additional cooling of the mixture or its part and directed to the mixture before its expansion.

40. The method as claimed in claim 34, wherein during the process of cooling or after it the liquid phase is separated from the mixture, which is passed through a throttling valve, and part of the products, obtained after the throttling valve, is used to cool the mixture and directed to the mixture before its expansion.

41. The method as claimed in claim 34 or 40, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

42. The method as claimed in claim 41, wherein before expansion the mixture is compressed additionally in a compressor.

43. The method as claimed in claim 34 or 40, wherein after mixing with the products, directed to the initial mixture before its expansion, the obtained mixture or compressed additionally in a compressor.

44. The method as claimed in claim 43, wherein the gas-phase products, coming from the rectifying tower, are cooled and expanded, and part of the products enriched in components heavier than methane is separated, which is directed, either partially or totally, to the rectifying tower.

45. The method as claimed in claim 43, wherein the gas-phase products, coming from the rectifying tower, are compressed additionally in the compressor before cooling.

46. The method as claimed in claim 45, wherein the gas-phase products, coming from the rectifying tower, are expanded to obtain the products enriched in components heavier than methane, the latter is directed, either partially or totally, to the rectifying tower or returned to the flow of gas-phase products before its expansion.

47. The method as claimed in claim 46, wherein part of the products enriched in components heavier than methane, which are obtained after expansion of the gas-phase products, is returned to the initial mixture before its expansion.

48. The method as claimed in claim 37, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

49. A method of low-temperature separation of a mixture of hydrocarbon gases, which includes cooling of the mixture, expansion of the mixture or its part without doing mechanical work, partial condensation of the mixture during its expansion, separation of the mixture or its part in a rectifying tower to obtain the products in liquid and gas phase, wherein the process of the mixture expansion is implemented by passing the mixture through a nozzle channel such that in the nozzle channel and/or at an entry of the nozzle channel the mixture flow is swirled, flows through a converging-diverging nozzle section of the nozzle channel, and at an exit of the nozzle channel or its part the mixture flow is separated based on a spatial relationship of heavier swirling components and lighter swirling components into, at least, two flows, one of which is enriched in components heavier than methane, while the other flow is depleted in these components; the enriched flow and the gas-phase products, coming from the rectifying tower, are directed, either partially or totally, to the mixture before its expansion.

50. The method as claimed in claim 49, wherein after separation of the flows at least one of them is compressed by passing the flow through a diffuser.

51. The method as claimed in claim 49, wherein before expansion the mixture or its part is mixed in an ejector with the gas-phase products coming from the rectifying tower.

52. The method as claimed in claim 49, wherein before expansion and/or after it the liquid phase is separated from the mixture or its part, which is passed through a throttling valve, and the products, obtained after the valve, are directed, either partially or totally, to the rectifying tower.

53. The method as claimed in claim 49, wherein the gas-phase products, coming from the rectifying tower, are cooled additionally.

54. The method as claimed in claim 52, wherein at least part of the gas-phase products, coming from the rectifying tower, is directed to the mixture before its throttling together with part of the products obtained after the throttling valve.

55. The method as claimed in claim 52, wherein at least part of the liquid phase separated from the mixture is used for additional cooling of the mixture or its part and directed to the mixture before its expansion.

56. The method as claimed in claim 49, wherein before expansion or after expansion the liquid phase is separated from the mixture, which is passed through a throttling valve, and the products, obtained after the throttling valve, are used to cool the mixture or its part.

57. The method as claimed in claim 49 or 56, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.

58. The method as claimed in claim 57, wherein before expansion the mixture is compressed additionally in a compressor.

59. The method as claimed in claim 49 or 56, wherein after mixing with the products directed to the initial mixture before its expansion, the obtained mixture is compressed additionally in a compressor.

60. The method as claimed in claim 59, wherein the gas-phase products, coming from the rectifying tower, are cooled and expanded, and part of products enriched in components heavier than methane is separated, which is directed, either partially or totally, to the rectifying tower.

61. The method as claimed in claim 59, wherein the gas-phase products, coming from the rectifying tower, are compressed additionally in the compressor before cooling.

62. The method as claimed in claim 61, wherein the gas-phase products, coming from the rectifying tower, are expanded to obtain the products enriched in components heavier than methane, which is directed, either partially or totally, to the rectifying tower or returned to the flow of gas-phase products before its expansion.

63. The method as claimed in claim 62, wherein part of the products enriched in components heavier than methane, which are obtained after expansion of the gas-phase products, is returned to the initial mixture before its expansion.

64. The method as claimed in claim 53, wherein before expansion or after expansion the mixture or its part is passed through a turbo-expander turbine.