AU2019272029A1 - Apparatus and process for separating a gas rich in co2 by distillation and/or partial condensation at subambient temperature - Google Patents

Apparatus and process for separating a gas rich in co2 by distillation and/or partial condensation at subambient temperature Download PDF

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Publication number
AU2019272029A1
AU2019272029A1 AU2019272029A AU2019272029A AU2019272029A1 AU 2019272029 A1 AU2019272029 A1 AU 2019272029A1 AU 2019272029 A AU2019272029 A AU 2019272029A AU 2019272029 A AU2019272029 A AU 2019272029A AU 2019272029 A1 AU2019272029 A1 AU 2019272029A1
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Prior art keywords
liquid
bath
heat exchanger
feed stream
richer
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Abandoned
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AU2019272029A
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Oumar KHAN
Mathieu LECLERC
Paul Terrien
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LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
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Publication of AU2019272029A1 publication Critical patent/AU2019272029A1/en
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0266—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0204—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the feed stream
    • F25J3/0223—H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/0605—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the feed stream
    • F25J3/0625—H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • F25J3/067—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/02—Processes or apparatus using separation by rectification in a single pressure main column system
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/40—Features relating to the provision of boil-up in the bottom of a column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/70—Refluxing the column with a condensed part of the feed stream, i.e. fractionator top is stripped or self-rectified
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2210/00—Processes characterised by the type or other details of the feed stream
    • F25J2210/70—Flue or combustion exhaust gas
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/80—Separating impurities from carbon dioxide, e.g. H2O or water-soluble contaminants
    • F25J2220/82—Separating low boiling, i.e. more volatile components, e.g. He, H2, CO, Air gases, CH4
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
    • F25J2230/80—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2235/00—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams
    • F25J2235/80—Processes or apparatus involving steps for increasing the pressure or for conveying of liquid process streams the fluid being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2245/00—Processes or apparatus involving steps for recycling of process streams
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2250/00—Details related to the use of reboiler-condensers
    • F25J2250/02—Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2270/00—Refrigeration techniques used
    • F25J2270/02—Internal refrigeration with liquid vaporising loop
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/40—Vertical layout or arrangement of cold equipments within in the cold box, e.g. columns, condensers, heat exchangers etc.
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
    • Y02C20/00—Capture or disposal of greenhouse gases
    • Y02C20/40—Capture or disposal of greenhouse gases of CO2

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

In a process for the separation of a feed stream comprising C02, a gas (7) derived from this stream is partially condensed in a heat exchanger (12) in which the feed stream circulates in tubes or between plates, the tubes or the plates being immersed in a bath of liquid C02 at a temperature of less than -430C which partially vaporizes, at least two thirds of the liquid from a separation system downstream of the heat exchanger being sent to the bath. 34 7'-e 17 19 2 [Fig. 1] 3 721- 11 315 o-9i /43 39 13 39 35 33 27 17 19 21 C37

Description

[Fig. 1]
3
11 721-
315 o-9i /43
13 39
39 35 33 27 17 19 21 C37
DESCRIPTION Title: Apparatus and process for separating a gas rich in C02 by distillation and/or partial condensation at subambient temperature
This application claims priority from French application number 1873365 filed on 19 December 2018, the contents of which are to be taken as incorporated herein by this reference. The present invention relates to a process and to an apparatus for separating a gas rich in C02 by distillation and/or partial condensation at subambient temperature, that is to say below 0°C. A gas rich in carbon dioxide contains at least 60 mol% of carbon dioxide, indeed even at least 80 mol% of carbon dioxide. The remainder of the gas may contain one or more of the following components: • the more volatile compounds, such as oxygen, nitrogen, argon, carbon monoxide, hydrogen, mercury or methane, • the heavier compounds, such as nitrogen oxide (NO or N02 or N20 or N204), S02, S03, C2+ compounds, H2S or aromatic compounds. The purification can be carried out by one or more successive stages of partial condensation and/or by distillation. EP 2 685 191 Al presents a solution for the separation of C02 by the cryogenic route using a shell-and-tube exchanger for the cooling to the lowest temperatures, close to the triple point of C02 (between -45 and -560 C). The gas is cooled down to temperatures close to the triple point, in order to condense a maximum of C02 with a minimum energy consumption. The gas to be condensed is cooled in the tubes against the liquid present in the shell. Thus, the gas is cooled down to the temperature of the liquid vaporizing in the bath (except for the approach in the exchanger, which is between 1 and 100 C). The liquid in the bath is generally a portion of the C02 resulting from the productive output of the unit or a portion of a dedicated cold cycle reduced in pressure to a pressure close to that of the triple point of C02 and at a temperature of between -56 and -50C. The other portions are vaporized at higher pressures (thus higher temperatures) in the main exchanger (of brazed aluminium plate and fin exchanger type generally). It is also possible to inject more liquid than necessary for the heat exchange into the shell-and-tube exchanger in order to obtain a liquid purge which makes it possible to prevent concentration phenomena in the bath. This purge is generally pumped and sent to production. In the case where the C02 used for the cooling contains a significant portion of impurities, its temperature is greater within the bath than before it is injected into the main exchanger. The term "impurities" is understood to mean all the compounds dissolved in the C02, either more volatile, such as N2, 02, Ar, CO, H2 or CH4, or heavier, such as CH30H, N02/N204, S02, SO3, C2+ compounds, H2S, aromatic compounds and the like. The phenomenon of rise in temperature in the bath is related to the difference in composition within the bath and before the injection of the C02. This is because, as the liquid in the bath vaporizes, if it is impure, its change in state does not take place at constant temperature. As the exchange of heat is carried out between the gas to be condensed and the bath, for a given approach, the gas to be condensed cannot be cooled as far as in the case where the bath consists of virtually pure C02. For example, if 2 0C of approach are considered, with a virtually pure cooling C02 at -54 0C, it will be possible to cool the gas to be condensed as far as -520 C. On the other hand, even if the cooling C02 is at -540 C but impure, the temperature of the bath will be greater than -54 0C and thus the gas to be condensed cannot be cooled down to -52C. Thus, not as much condensed C02 is recovered. One solution might consist in lowering the temperature of the cooling C02 to a lower temperature in order to obtain the desired temperature in the bath. However, this operation at a lower temperature would increase the risk of solidification of the C02 since the cooling C02 would have a temperature closer to the triple point of C02 before it is injected into the bath. As the purge flow rate of the path is generally low, if the purge is sent to production, a small pump with a very high compression ratio is then employed, which may present technological problems. A piston pump is then generally chosen but this type of pump requires repeated maintenance involving the shutdown of the pump and major costs. Finally, when a distillation column is employed in order to purify the C02 produced to give light compounds, the bottom liquid is generally reboiled in the main exchanger. In order for the liquid to be able to flow from the column toward the exchanger, the column has to be installed at a higher level than the exchanger. It is thus necessary to install a specific structure under the column. According to a subject matter of the invention, provision is made for a process for the separation of a feed stream comprising C02, comprising at least the following stages: a) Cooling the feed stream in a first brazed aluminium plate heat exchanger, consisting of corrugated sheets separated by plates. b) Cooling and partial or complete condensation of at least a portion of the feed stream cooled in a) or of a gas derived from this stream cooled in a) down to a temperature of less than -45 0C in a second heat exchanger in which the feed stream circulates in tubes or between plates, the tubes or the plates being immersed in a bath of liquid C02 at a temperature of less than -43C which partially vaporizes. c) Dispatch of at least a part of the partially or completely condensed feed stream to a separation system comprising at least one phase separator and/or at least one distillation column in order to produce a liquid richer in C02 than the feed stream. d) Dispatch of at least two thirds of the liquid richer in C02, indeed even all the liquid richer in C02, to the second heat exchanger in order to feed the liquid bath. e) Withdrawal of a portion of the liquid present in the bath. f) Pumping of at least a part of this liquid in order to form a pumped liquid. g) Injection, into the first heat exchanger, of at least a part of this pumped liquid or of a fluid derived from this pumped liquid in order to cool the feed stream. According to other optional characteristics: • The gas partially condensed in the second heat exchanger is sent to a first phase separator and the liquid from this phase separator feeds a distillation column or a second phase separator, a bottom liquid from the column or from the second separator constituting the liquid richer in C02 than the feed stream. • The pumped liquid of stage g) vaporizes in the first exchanger to form part of the gaseous product rich in C02. SA part of the liquid richer in C02 vaporizes in the bath, is reheated in the first exchanger and forms part of the gaseous product rich in C02. • At least a part of the liquid richer in C02 vaporizes in the bath, is reheated in the first exchanger and is mixed with the feed stream to be separated. SA part of the liquid richer in C02 originating from the bath forms part of a liquid product rich in C02, without having to be reheated in the first exchanger. • The separation system comprises a distillation column and a part of the liquid richer in C02 originating from the bath is vaporized in the first exchanger and sent back in the gaseous form to the bottom of the distillation column. SAllthe product rich in C02 originates from the second heat exchanger.
• The pumping is carried out by means of a pump of centrifugal type. According to another subject matter of the invention, provision is made for an apparatus for separation of a feed stream comprising C02, comprising a first brazed aluminium plate heat exchanger, consisting of corrugated sheets separated by plates, a second heat exchanger comprising a liquid bath and tubes or plates immersed in the bath, a separation system comprising at least one phase separator and/or at least one distillation column, a pipe for sending the feed stream to be cooled into the first heat exchanger, a pipe for sending a flow which is a portion of the feed stream cooled in the first heat exchanger or a gas derived from this cooled stream to be cooled down to a temperature of less than -45 0C into the tubes or between the plates of the second heat exchanger which are immersed in the bath of liquid C02 at a temperature of less than 43 0C, a pipe for sending a liquid produced by partially or completely condensing the flow into a separation system comprising at least one phase separator and/or at least one distillation column, in order to produce a liquid richer in C02 than the feed stream, a pipe connected to the liquid bath of the second heat exchanger, in order to send thereto all the liquid richer in C02, a pump, a pipe for withdrawing a portion of the liquid present in the bath, connected to the pump, a pipe connected to the outlet of the pump and to the first heat exchanger and a pipe for exiting the vaporized pumped liquid from the first heat exchanger. Optionally, the bottom of the distillation column and/or the bottom of the phase separator is installed at a level equal to or lower than that of the first heat exchanger. The present invention consists firstly in significantly increasing the portion of the C02 sent to the bath, although the amount of cooling liquid C02 sent to the exchanger is then markedly greater than that which is necessary for the condensation of the gas to be cooled. Thus, as the flow rate of vaporized liquid into the bath remains the same, its portion has decreased compared to the flow rate of liquid injected into the bath. The change in composition due to this vaporization is then reduced and the temperature in the bath is virtually constant. It is then possible to cool the gas to be condensed to lower temperatures, making possible an energy optimization. In this way, the amount of cooling liquid available at higher pressure has then been reduced. The purge pump of the bath will then be used to increase the pressure of the purged liquid. The liquid, again pressurized, will then be able to be vaporized and/or sent to production. In this case, the purge pump has significantly increased in size, which can affect its cost. However, in this case, a pump of centrifugal type can generally be used, then making possible a reduction in the maintenance costs. A portion of the pumped liquid can moreover be vaporized in the main exchanger and sent back to the distillation column in order to provide for the reboiling thereof. In this case, the column no longer needs to be with a pressure head over the main exchanger. It is thus possible to install the column on the ground and to achieve savings in committed costs. Finally, as the purge is significantly increased in the exchanger, the risks of concentration of impurities in the bath are further reduced. This is all the more important when these impurities can solidify, such as N02/N204, for example. It is also possible to use this stage to reboil the liquid. This is because, in a column free scheme, to send all of the liquid originating from the pot(s) makes it possible to reboil the light impurities. By then recycling the vaporized gas and by using only the liquid exiting from the bath of the exchanger as final product, it is possible to purify beyond a simple partial condensation scheme. In this case, the gas vaporized in the exchanger is recycled at the inlet of the cold box (in a feed stream compressor, a recycle compressor or a dedicated booster, according to the scheme). It is thus possible to operate a unit for the cryogenic separation of C02 without a distillation column but with better performance qualities than a simple partial condensation scheme. A fluid is derived from another fluid in the following cases: * when a fluid is divided into several parts without change in composition, • when a fluid is reheated, • when a fluid is cooled, • when a fluid is pressurized, • when a fluid is reduced in pressure, • when a fluid is cooled and partially condensed, it being possible for the fluid derived from the fluid to be the noncondensed gas or the condensed liquid. The invention will be described in more detail with reference to the figure, which represents a process according to the invention.
[Fig 1] shows a process of the separation of a gas rich in C02 1, containing 60 mol% of carbon dioxide, indeed even at least 80 mol% of carbon dioxide. The remainder of the gas may contain one or more of the following components:
• the more volatile compounds, such as oxygen, nitrogen, argon, carbon monoxide, hydrogen, mercury or methane, or • the heavier compounds, such as nitrogen oxide (NO or N02 or N20 or N204), S02, SO3, C2+ compounds, H2S or aromatic compounds. The gas 1 is at a pressure of at least 5.5 bar, optionally after compression in a compressor. The gas 1 is cooled and partially condensed in a first brazed aluminium plate heat exchanger 3, consisting of corrugated sheets separated by plates. The partially condensed gas is separated in a phase separator 5. The gas 7 from the phase separator is subjected to cooling down to a temperature of less than -450 C, which results in a partial or complete condensation, in a second heat exchanger 12 in which the feed stream circulates in tubes or between plates, the tubes or the plates being immersed in a bath of liquid C02 at a temperature of less than -43C. The liquid of the bath partially vaporizes. The gas 7, in this instance partially condensed, is sent to a phase separator 15. The liquid from the phase separator 15 is sent to the top of a distillation column 21. The gas 11 from the phase separator 15 is reheated in the heat exchanger 3. The liquid 9 from the phase separator 5 is mixed with the liquid 13, the mixture is reduced in pressure in a valve 17 and sent as liquid 19 to the top of the column 21. The top gas 43 from the column 21 is reheated in the heat exchanger 3. The liquid 23 constitutes a liquid richer in C02 than the gas 1. At least two thirds of this liquid 23 are sent, after reduction in pressure, into the second heat exchanger in order to form the liquid bath and to exchange heat with the gas 7. Optionally, all the liquid 23 may be sent thereto, as illustrated. A part of the liquid sent to the second heat exchanger vaporizes to form a gas 29 which is reheated in the heat exchanger 3 and which is rich in C02. This liquid can comprise at least 90 mol%, indeed even at least 99 mol%, of C02. A high proportion of the liquid 23 does not vaporize in the heat exchanger and is withdrawn from the exchanger 12 as liquid 27. This liquid is pressurized by a pump 25 of centrifugal type up to a pressure of 80 bara. The liquid 27 is divided into two. A part 33 is reduced in pressure in the valve 35 and vaporized in the heat exchanger 3 to form a gaz. The gas is divided into two. A part 37 is sent back, without having been cooled, to the bottom of the distillation column 21 in order to provide reboiling. The gas 29 enters a compressor 31 and another part 39 of the gas formed by vaporizing the liquid 33 is sent to an intermediate level of the compressor 31. The compressor 31 produces a pressurized gas 45 which can be condensed and mixed with the liquid 41 to form a liquid product under pressure 47. It will be noted that, if the gas 7 is completely condensed in the exchanger 12, the phase separator 15 is not required and the liquid 13 can pass directly to the column. Likewise, the column 21 can be replaced by a phase separator. In this case, the liquid from this phase separator feeds the bath of the second exchanger 12 as the liquid 23. The gas from the last phase separator is reheated and mixed with the gas to be separated 1. The bottom of the distillation column (when present) and/or the bottom of the phase separator or of the last phase separator (in the absence of distillation column) is installed at a level equal to or lower than that of the first heat exchanger. Thus, no supporting structure is required. The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

Claims (10)

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:
1. Process for the separation of a feed stream comprising C02, comprising at least the following stages: a) Cooling the feed stream in a first brazed aluminium plate heat exchanger, consisting of corrugated sheets separated by plates. b) Cooling and partial or complete condensation of at least a portion of the feed stream cooled in a) or of a gas derived from this stream cooled in a) down to a temperature of less than -45 0C in a second heat exchanger in which the feed stream circulates in tubes or between plates, the tubes or the plates being immersed in a bath of liquid C02 at a temperature of less than -43C which partially vaporizes. c) Sending of at least a part of the partially or completely condensed feed stream to a separation system comprising at least one phase separator and/or at least one distillation column in order to produce a liquid richer in C02 than the feed stream. d) Sending of at least two thirds of the liquid richer in C02, indeed even all the liquid richer in C02, to the second heat exchanger in order to feed the liquid bath. e) Withdrawal of a portion of the liquid present in the bath. f) Pumping of at least a part of this liquid in order to form a pumped liquid. g) Injection, into the first heat exchanger, of at least a part of this pumped liquid or of a fluid derived from this pumped liquid in order to cool the feed stream.
2. Process according to Claim 1, in which the gas partially condensed in the second heat exchanger is sent to a first phase separator and the liquid from this phase separator feeds a distillation column or a second phase separator, a bottom liquid from the column or from the second separator constituting the liquid richer in C02 than the feed stream.
3. Process according to Claim 1 or Claim 2, in which the pumped liquid of stage g) vaporizes in the first exchanger to form part of the gaseous product rich in C02.
4. Process according to any one of Claims 1 to 3, in which a part of the liquid richer in C02 vaporizes in the bath, is reheated in the first exchanger and forms part of the gaseous product rich in C02.
5. Process according to any one of Claims 1 to 4, in which at least a part of the liquid richer in C02 vaporizes in the bath, is reheated in the first exchanger and is mixed with the feed stream to be separated.
6. Process according to any one of the preceding claims, in which a part of the liquid richer in C02 originating from the bath forms part of a liquid product rich in C02, without having to be reheated in the first exchanger.
7. Process according to any one of the preceding claims, in which the separation system comprises a distillation column and a part of the liquid richer in C02 originating from the bath is vaporized in the first exchanger and sent back in the gaseous form to the bottom of the distillation column.
8. Process according to any one of the preceding claims, in which all the product rich in C02 originates from the second heat exchanger.
9. Process according to any one of the preceding claims, in which the pumping is carried out by means of a pump of centrifugal type.
10. An apparatus for separation of a feed stream comprising C02, comprising a first brazed aluminium plate heat exchanger, consisting of corrugated sheets separated by plates, a second heat exchanger comprising a liquid bath and tubes or plates immersed in the bath, a separation system comprising at least one phase separator and/or at least one distillation column, a pipe for sending the feed stream to be cooled into the first heat exchanger, a pipe for sending a flow which is a portion of the feed stream cooled in the first heat exchanger or a gas derived from this cooled stream to be cooled down to a temperature of less than -45 0C into the tubes or between the plates of the second heat exchanger which are immersed in the bath of liquid C02 at a temperature of less than 43 0C, a pipe for sending a liquid produced by partially or completely condensing the flow into a separation system comprising at least one phase separator and/or at least one distillation column, in order to produce a liquid richer in C02 than the feed stream, a pipe connected to the liquid bath of the second heat exchanger, in order to send thereto all the liquid richer in C02, a pump, a pipe for withdrawing a portion of the liquid present in the bath, connected to the pump, a pipe connected to the outlet of the pump and to the first heat exchanger and a pipe for exiting the vaporized pumped liquid from the first heat exchanger.
[Fig. 1]
1/1
AU2019272029A 2018-12-19 2019-11-29 Apparatus and process for separating a gas rich in co2 by distillation and/or partial condensation at subambient temperature Abandoned AU2019272029A1 (en)

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EP2685191A1 (en) 2012-07-13 2014-01-15 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and apparatus for the separation of a gas rich in carbon dioxide
FR2993353B1 (en) * 2012-07-13 2018-06-15 Air Liquide PROCESS AND APPARATUS FOR PURIFYING A LOW TEMPERATURE CARBON DIOXIDE RICH MIXTURE
FR3002312A1 (en) * 2013-02-21 2014-08-22 Air Liquide SUBAMBIOUS TEMPERATURE SEPARATION OF A GASEOUS MIXTURE CONTAINING CARBON DIOXIDE AND LIGHTER CONTAMINANT
FR3034509B1 (en) * 2015-04-02 2019-07-12 L'air Liquide, Societe Anonyme Pour L'etude Et L'exploitation Des Procedes Georges Claude PROCESS FOR TREATING NATURAL GAS TO MINIMIZE LOSS OF ETHANE

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