EP0634618B1 - Self-refrigerating process for cryogenic fractionation and purification of gas and heat exchanger for carrying out the process - Google Patents

Self-refrigerating process for cryogenic fractionation and purification of gas and heat exchanger for carrying out the process Download PDF

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Publication number
EP0634618B1
EP0634618B1 EP94401517A EP94401517A EP0634618B1 EP 0634618 B1 EP0634618 B1 EP 0634618B1 EP 94401517 A EP94401517 A EP 94401517A EP 94401517 A EP94401517 A EP 94401517A EP 0634618 B1 EP0634618 B1 EP 0634618B1
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Prior art keywords
circuit
gas
condensate
circuits
purified
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EP94401517A
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German (de)
French (fr)
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EP0634618A1 (en
Inventor
Henri Paradowski
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Francaise dEtudes et de Construction Technip SA
Technip Energies France SAS
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Francaise dEtudes et de Construction Technip SA
Technip SA
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • 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
    • F25J3/0252—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 hydrogen
    • 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
    • F25J3/0219—Refinery gas, cracking gas, coke oven gas, gaseous mixtures containing aliphatic unsaturated CnHm or gaseous mixtures of undefined nature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0233—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 1 carbon atom or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
    • F25J3/0238—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of CnHm with 2 carbon atoms or more
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
    • F25J5/002—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger
    • F25J5/007—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger combined with mass exchange, i.e. in a so-called dephlegmator
    • 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
    • F25J2200/80—Processes or apparatus using separation by rectification using integrated mass and heat exchange, i.e. non-adiabatic rectification in a reflux exchanger or dephlegmator
    • 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
    • F25J2210/12—Refinery or petrochemical off-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
    • F25J2215/00—Processes characterised by the type or other details of the product stream
    • F25J2215/62—Ethane or ethylene
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S62/00—Refrigeration
    • Y10S62/902—Apparatus
    • Y10S62/903—Heat exchange structure

Definitions

  • the subject of the present invention is a method of cryogenic fractionation and of gas purification, as defined in the preamble of claim 1.
  • Certain gases include both constituents which are fairly easily liquefiable at low temperature and constituents which are more difficult to liquefy or non-liquefiable. It is therefore common to try to separate them by cooling in order to condense the elements which are more easily liquefiable and thus separate them from the constituents which are more difficult to liquefy or non-liquefiable.
  • mixtures of different hydrocarbons or non-hydrocarbon components such as nitrogen, hydrogen, argon and / or carbon monoxide and, for example , catalytic cracking or steam cracking gases.
  • reflux exchangers also known as “dephlegmators”
  • external refrigeration being usually supplied countercurrently through a refrigeration cycle or by dynamic gas expansion. This limits the use of these techniques to the temperatures at which the refrigeration cycles are available and to cases where the expansion of the effluents, for example hydrogen or methane, is possible.
  • the technique consists in cooling the gas to be purified in a first exchanger, in separating the non-gas condensed from the first condensate formed, for example in a fractionation column, to further cool the uncondensed gas in a second exchanger to form a second condensate, to separate this second condensate from the uncondensed gas in a separator and to return the second condensate to the column as reflux.
  • the uncondensed gas separated from the second condensate constitutes the purified gas.
  • the cooling agent for the two exchangers consists of the first condensate which is subjected to vaporization by expansion and passes successively through the second then the first exchanger.
  • the purified gas can itself pass through the second and then the first exchanger.
  • the method and the device of the invention have the advantage of not generally requiring refrigeration using refrigerants foreign to the installation and of not requiring expansion of the constituent (s) ) the most difficult to liquefy (s) of the treated gas mixture.
  • This last point is important because, on the one hand, liquefaction techniques most often require the application of high pressure and, on the other hand, certain separate gases obtained such as, for example, hydrogen and / or carbon monoxide are often reactants for chemical reactions which must themselves be carried out under high pressure. It would therefore be uneconomic to expand these gases during cryogenic separation and then have to recompress them.
  • the method and the device of the invention are more economical than the known method of self-refrigeration because they require only a unitary exchanger which is less expensive than the multiple devices (at least two exchangers, a fractionation column , a separator and many circuits) of the known method. They also reduce heat losses and avoid high expenses for insulating circuits and devices.
  • the gases to which the invention applies are mixtures of at least two, and preferably at least three, different chemical components and of different boiling (or condensation) temperatures under the conditions of the process, and, for example, a mixture of hydrogen, methane and at least one C2 hydrocarbon such as ethane or ethylene, with or without higher hydrocarbons (C3 or more).
  • Other mixtures also contain carbon monoxide and / or nitrogen.
  • the invention uses a unitary heat exchanger (a unitary heat exchange zone) as defined in claim 8.
  • One of the circuits called the reflux circuit or first circuit, is arranged essentially in an upper portion. of the exchanger (the exchange zone), that is to say in a relatively cooler portion of the exchanger. It is preferably a "non-tortuous" circuit, that is to say in which the condensed liquid can flow in a generally descending direction.
  • Another circuit (fifth circuit), preferably of the tortuous type, not suitable for reflux of liquid, is essentially arranged in a lower portion of the exchanger (the exchange zone), that is to say in a portion relatively cooler of the exchanger.
  • circuit of the tortuous type directed generally vertically, is meant a circuit such that the fluid which is introduced therein at the base can progress generally from the bottom upwards without significant reflux of the liquid portions of this fluid, which supposes, by example, an average slope less steep than in the above-mentioned reflux circuit; in other words, all or almost all of the fluid (liquid and gaseous) will follow a generally ascending path in this circuit of tortuous type and will be collected at the top of said circuit, the point (or zone) of discharge being located in a portion intermediate of the heat exchanger, for example in the vicinity of the first third or half the height of the exchanger.
  • the aforementioned tortuous circuit is in whole, or almost in whole, at a level lower than the reflux circuit, and, even better, than the two circuits are arranged substantially one above the other in the exchanger.
  • the second, third and fourth circuits can be tortuous or not, preferably non-tortuous.
  • the five aforementioned circuits are in heat exchange relationship with each other at each level of the exchanger where they are present, which supposes that the exchanger is preferably made of a good heat conductive material, with walls as thin as possible compatible with the resistance of the materials and having a high exchange surface. Specialists can easily make such exchangers from the previous indications.
  • the aforementioned multi-component gaseous fluid (at least two and preferably at least three condensable components) is circulated from bottom to top in the fifth circuit, located in a lower portion of the exchanger, in conditions of temperature and pressure such that it can partially condense without backflow into said circuit.
  • the mixture of gas and liquid (first condensate) withdrawn from the top of the fifth circuit is separated into a gas phase and a liquid phase, in a separation zone.
  • the resulting gas phase is circulated from bottom to top in the first circuit (reflux circuit) preferably located above the fifth circuit, as indicated above.
  • the second condensate thus formed can be mixed with the first condensate already present in the separation zone or be collected separately.
  • the uncondensed gas collected at the top of the first circuit is returned to the exchanger by the aforementioned second circuit to circulate there from top to bottom against the current of the fluids circulating in the first circuit and in the fifth circuit. It comes out heated by constituting the purified gas, formed of the most volatile elements of the gaseous supply fluid.
  • the liquid phase of the separation zone consisting of the first condensate alone or of the mixture of the first and second condensates, is circulated from the bottom to the top in the aforementioned third circuit where it undergoes sub-cooling. It is then relaxed, statically or dynamically, and circulated from top to bottom in the aforementioned fourth circuit of the exchanger where it vaporizes thanks to the heat removed from the fluids of the tortuous circuit, the first circuit and the third circuit.
  • the gas stream discharged at the bottom of the fourth circuit contains the least volatile constituents of the gaseous supply fluid. It can, if desired, be partially recycled or otherwise treated.
  • only part of the gaseous phase collected at the head of the first circuit is sent to the second circuit; the other part is expanded and used in the heat exchanger in the downward direction, either by passing through a sixth exchange circuit or, preferably, by passing through the fourth circuit, in admixture with the expanded liquid phase of the (or ) condensate (s) introduced therein, to allow vaporization at higher pressure.
  • the production of purified gas under high pressure is less important, but this does not present any drawback when the gas stream from the fourth circuit is recycled or the gas stream from the sixth circuit is recompressed.
  • Preferably 90 to 98% by mole of the gaseous phase collected at the head of the first circuit is sent to the second circuit and the other part (2 to 10 mol%) is expanded and joined to said liquid phase of the fourth circuit.
  • part of the gas to be purified does not pass through the fifth circuit and is sent directly to the gas-liquid separation zone or to the first circuit.
  • a fraction of 80 to 95 mol% of the gas passes through the fifth circuit, and a fraction of 5 to 20 mol% is sent to the separation zone. It is thus possible to maximize the quantity of purified gas obtained by the second circuit.
  • Yet another variant consists in supplying a liquid phase of external origin to the exchanger, under conditions where this liquid phase can relax and evaporate after expansion during its passage from top to bottom in the exchanger.
  • This liquid phase of external origin can first pass through the exchanger from bottom to top by an auxiliary circuit to undergo sub-cooling there before descending by an auxiliary circuit. This is advantageous when starting the installation to facilitate and accelerate its cooling. More simply, if its composition is compatible with that of the liquid of the third circuit, it can be mixed with the latter before the entry thereof into the third circuit or only before the entry of said liquid into the fourth circuit.
  • the condensation rate of the gaseous supply fluid in the fifth circuit is also advantageous to adjust the condensation rate of the gaseous supply fluid in the fifth circuit to a value of 2 to 20% by mole.
  • the temperature and pressure conditions in the unitary heat exchange zone of the invention depend, obviously, the composition of the feedstock, and the technician will be able to choose these conditions in each particular case using his knowledge, the main thing being to operate under conditions allowing partial condensation of the fluid. food. Due to the fact that it is a cryogenic process, the operation is carried out below ambient temperature, for example between 0 ° C. and -150 ° C. depending on the gas treated and the pressure chosen. As, moreover, an expansion of the condensates is provided, one advantageously operates at a super-atmospheric pressure, for example between 5 and 100 bars. Below are values given as examples.
  • the invention also relates to a heat exchanger making it possible to implement the method described above.
  • This exchanger is characterized in that it comprises at least five distinct circuits, generally vertical, designated respectively first, second, third, fourth and fifth circuits, in indirect heat exchange relationship with each other at each level of said exchanger, said circuits forming a unitary assembly, the first circuit being of the non-tortuous type and the fifth circuit of the tortuous type, the first circuit being disposed at a level higher than that of the fifth circuit, at least one direct junction between the top of the first circuit and the top of the second circuit, at least one junction through an expansion means between the top of the third circuit and the top of the fourth circuit, at least one zone of separation of phases connected by its upper part to the base of the first circuit, by its lower part to the base of the third circuit and laterally at the top of the fifth circuit.
  • the first circuit is superimposed on the fifth circuit.
  • FIGS 1 and 2 attached illustrate the invention without limitation.
  • the heat exchanger E1 has five main circuits C1 to C5 corresponding respectively to the first, second, third, fourth and fifth circuits of the process.
  • the gas to be purified is sent by lines 1 and 3 to the circuit C5 and leaves it by line 2 in the mixed gas / first condensate phase.
  • the two phases separate in the flask B1: the gas phase is sent by line 16 to the circuit C1; it undergoes cooling there and a second condensate forms and flows back through line 17.
  • the uncondensed gas leaves at the head and is sent by lines 5 and 7 to circuit C2. It comes out warmed at the bottom of this circuit by line 14. This gives the purified gas or the lightest fraction of the charge.
  • the condensates coming from circuits C5 and C1 respectively by lines 2 and 17 are mixed and sent by line 4 to circuit C3 where they undergo sub-cooling. They come out at the head by line 8, pass through the expansion valve V1 and are sent to circuit C4 by line 9. They can pass through a balloon B2, in which case the gas phase and the liquid phase are sent to C4 respectively by the lines 18 and 19 to point 10.
  • the condensates vaporized leaves the circuit C4 via line 11. These are the least volatile fractions of the charge.
  • part of the gas from the circuit C1 is taken from line 5 and sent through the expansion valve V2 and line 6 to the cylinder B2.
  • part of the starting gas is sent to the balloon B1 through the line 15 and the valve V4.
  • a liquid phase compatible with the condensate of line 4 is sent by line 12 to an auxiliary circuit C6 to undergo sub-cooling there before passing through line 13 and the expansion valve V3 and sent to the balloon. B2, preferably by line 9.
  • each circuit is separated from the neighboring circuit by a vertical sheet like the sheets 20, 21, 22, etc.
  • each circuit is of the multi-channel type, circuits C1 and C3 being examples of this, in fact we see vertical sheets such as 23 (corrugated sheet) or 24 (flat partition). ) dividing the circuits into a plurality of elementary channels such as 25 and 26.
  • channels 2, 16 and 17 relating to the fifth (2) and first (16 and 17) circuits of Figure 1, with their equivalents 2 ', 16', 17 ', 2'',16'' and 17 ".
  • the lateral conduits 2, 16, 17 (and their prime and second equivalents) are connected to separate balloons B1 or to a common elongated balloon B1.
  • Valves V2, V3 and V4 are closed.
  • Line 6,111,703 kmol / h of hydrogen-enriched gas containing less than 1 mol% of ethylene is collected under a pressure of 34.7 bar abs and 10.086 kmol / h of gas highly enriched in ethylene in line 12 under a pressure of 1.8 bar abs.
  • the latter gas can be sent to a distillation column to obtain an even richer stream of ethylene.
  • Table 1 The current compositions of the installation are shown in Table 1.
  • Example 2 The procedure is as in Example 1, however, partially opening the valve V2 to allow the vaporization of the fluid circulating in the circuit 4 at higher pressure.
  • Tables 2 and 6 give respectively the compositions of the fluids, at the inlet and at the outlet, and the operating conditions.
  • Example 3 The procedure is as in Example 3 with, in addition, partial opening of the valve V3 allowing the introduction of a distillate consisting of a 50/50 mixture by volume of methane and ethylene, obtained by rectification of the purified gas from a previous operation.
  • Such an operating mode is used when starting the installation to facilitate its cooling.
  • Tables 4 and 8 give the compositions of the fluids and the operating conditions.
  • TABLE 1 Gas to be purified (line 1) Purified gas (line 14) Separate gas (line 11) Molar composition Hydrogen % mol 62.3100 67.7567 1.9871 Carbon monoxide % mol 0.3814 0.4073 0.0941 Methane % mol 31.3551 31.0198 35.0688 Acetylene % mol 0.0369 0.0013 0.4312 Ethylene % mol 5.4370 0.8057 56.7295 Ethane % mol 0.4784 0.0092 5.6743 Propylene % mol 0.0012 0.0000 0.0149 Temperature ° C -93.00 -95.00 -100.00 Pressure abs bar 35.00 34.70 1.80 Molar flow Kmol / h 121,788 111.703 10,086 Gas to be purified (line 1) Purified gas (line 14) Separate gas (line 11) Molar composition Hydrogen % mol 62.3100 67.7566 12.87

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Description

La présente invention a pour objet un procédé de fractionnement cryogénique et de purification de gaz, tel que défini dans le préambule de la revendication 1.The subject of the present invention is a method of cryogenic fractionation and of gas purification, as defined in the preamble of claim 1.

Elle vise également un échangeur de chaleur pour l'exécution de ce procédé.It also relates to a heat exchanger for the execution of this process.

Certains gaz comprennent à la fois des constituants assez facilement liquéfiables à basse température et des constituants plus difficilement liquéfiables ou non liquéfiables. IL est donc courant de chercher à les séparer par refroidissement pour condenser les éléments plus facilement liquéfiables et les séparer ainsi des constituants plus difficilement liquéfiables ou non liquéfiables.Certain gases include both constituents which are fairly easily liquefiable at low temperature and constituents which are more difficult to liquefy or non-liquefiable. It is therefore common to try to separate them by cooling in order to condense the elements which are more easily liquefiable and thus separate them from the constituents which are more difficult to liquefy or non-liquefiable.

Parmi les gaz à plusieurs composants qui peuvent ainsi être traités, on peut citer les mélanges d'hydrocarbures différents ou des composants non hydrocarbonés tels que l'azote, l'hydrogène, l'argon et/ou le monoxyde de carbone et, par exemple, les gaz de craquage catalytique ou de vapocraquage.Among the gases with several components which can thus be treated, there may be mentioned mixtures of different hydrocarbons or non-hydrocarbon components such as nitrogen, hydrogen, argon and / or carbon monoxide and, for example , catalytic cracking or steam cracking gases.

Pour obtenir le refroidissement nécessaire on fait appel dans la technique antérieure, à des échangeurs de chaleur, et notamment à des échangeurs à reflux, aussi désignés par "déphlegmateurs", la réfrigération externe étant fournie habituellement à contre-courant par un cycle de réfrigération ou par une détente dynamique de gaz. Ceci limite l'emploi de ces techniques aux températures auxquelles les cycles de réfrigération sont disponibles et aux cas où la détente des effluents, par exemple de l'hydrogène ou du méthane, est possible.In order to obtain the necessary cooling, heat exchangers are used in the prior art, and in particular reflux exchangers, also known as "dephlegmators", external refrigeration being usually supplied countercurrently through a refrigeration cycle or by dynamic gas expansion. This limits the use of these techniques to the temperatures at which the refrigeration cycles are available and to cases where the expansion of the effluents, for example hydrogen or methane, is possible.

On peut également utiliser une technique d'auto-réfrigération. La technique consiste à refroidir le gaz à purifier dans un premier échangeur, à séparer le gaz non condensé du premier condensat formé, par exemple dans une colonne de fractionnement, à refroidir davantage le gaz non condensé dans un deuxième échangeur pour former un second condensat, à séparer ce second condensat du gaz non condensé dans un séparateur et à renvoyer le second condensat à la colonne comme reflux.One can also use a self-refrigeration technique. The technique consists in cooling the gas to be purified in a first exchanger, in separating the non-gas condensed from the first condensate formed, for example in a fractionation column, to further cool the uncondensed gas in a second exchanger to form a second condensate, to separate this second condensate from the uncondensed gas in a separator and to return the second condensate to the column as reflux.

Le gaz non condensé séparé du second condensat constitue le gaz purifié. L'agent de refroidissement pour les deux échangeurs est constitué par le premier condensat qui est soumis à une vaporisation par détente et traverse successivement le second puis le premier échangeur. Le gaz purifié peut lui-même traverser le second puis le premier échangeur.The uncondensed gas separated from the second condensate constitutes the purified gas. The cooling agent for the two exchangers consists of the first condensate which is subjected to vaporization by expansion and passes successively through the second then the first exchanger. The purified gas can itself pass through the second and then the first exchanger.

Le procédé et le dispositif de l'invention présentent l'avantage de ne pas nécessiter, en règle générale, de réfrigération à l'aide de réfrigérants étrangers à l'installation et de ne pas exiger de détente du (ou des ) constituant(s) le(s) plus difficilement liquéfiable(s) du mélange gazeux traité. Ce dernier point est important car, d'une part, les techniques de liquéfaction exigent le plus souvent l'application d'une pression élevée et, d'autre part, certains gaz séparés obtenus tels que, par exemple, l'hydrogène et/ou le monoxyde de carbone sont souvent des réactifs pour des réactions chimiques qui doivent elles-mêmes être mises en oeuvre sous pression élevée. Il serait donc peu économique de détendre ces gaz au cours de la séparation cryogénique pour avoir ensuite à les recomprimer.The method and the device of the invention have the advantage of not generally requiring refrigeration using refrigerants foreign to the installation and of not requiring expansion of the constituent (s) ) the most difficult to liquefy (s) of the treated gas mixture. This last point is important because, on the one hand, liquefaction techniques most often require the application of high pressure and, on the other hand, certain separate gases obtained such as, for example, hydrogen and / or carbon monoxide are often reactants for chemical reactions which must themselves be carried out under high pressure. It would therefore be uneconomic to expand these gases during cryogenic separation and then have to recompress them.

D'autre part le procédé et le dispositif de l'invention sont plus économiques que le procédé connu d'auto-réfrigération car ils ne requièrent qu'un échangeur unitaire moins coûteux que les multiples appareils (au moins deux échangeurs, une colonne de fractionnement, un séparateur et de nombreux circuits) du procédé connu. Ils réduisent aussi les pertes thermiques et évitent des dépenses élevées d'isolation des circuits et appareils.On the other hand, the method and the device of the invention are more economical than the known method of self-refrigeration because they require only a unitary exchanger which is less expensive than the multiple devices (at least two exchangers, a fractionation column , a separator and many circuits) of the known method. They also reduce heat losses and avoid high expenses for insulating circuits and devices.

Les gaz auxquels s'applique l'invention sont des mélanges d'au moins deux, et de préférence d'au moins trois, composants chimiques différents et de températures d'ébullition (ou de condensation) différentes dans les conditions du procédé, et, par exemple, un mélange d'hydrogène, de méthane et d'au moins un hydrocarbure en C2 tel que l'éthane ou l'éthylène, avec ou sans hydrocarbures supérieurs (C3 ou plus). D'autres mélanges renferment en outre du monoxyde de carbone et/ou de l'azote.The gases to which the invention applies are mixtures of at least two, and preferably at least three, different chemical components and of different boiling (or condensation) temperatures under the conditions of the process, and, for example, a mixture of hydrogen, methane and at least one C2 hydrocarbon such as ethane or ethylene, with or without higher hydrocarbons (C3 or more). Other mixtures also contain carbon monoxide and / or nitrogen.

Par ailleurs, on connaît d'après le document US-A-5 017 204 un procédé autoréfrigéré de fractionnement cryogénique et de purification d'un fluide gazeux d'alimentation, correspondant à l'état de la technique décrit dans le préambule de la revendication 1.Furthermore, from the document US Pat. No. 5,017,204, a self-refrigerated process for cryogenic fractionation and purification of a gaseous feed fluid is known, corresponding to the state of the art described in the preamble of claim. 1.

Le procédé de l'invention est un procédé autoréfrigéré de fractionnement cryogénique et de purification d'un fluide gazeux d'alimentation à au moins deux composants condensables de températures de condensation différentes, respectivement au moins un composant relativement lourd à éliminer et au moins un composant relativement léger à récupérer de manière à produire un gaz purifié comprenant préférentiellement le(s) composant(s) relativement léger (s) et un gaz séparé comprenant préférentiellement le(s) composant(s) relativement lourd(s), dans lequel :

  • on opère dans une zone d'échange thermique formant un ensemble unitaire et comprenant au moins cinq circuits distincts, désignés respectivement par premier, deuxième, troisième, quatrième et cinquième circuits, en relation d'échange thermique indirect les uns avec les autres à chaque niveau de la zone d'échange thermique, globalement verticaux,
  • on refroidit au moins une fraction du fluide gazeux d'alimentation dans des conditions telles qu'il puisse se condenser en partie pour donner un premier condensat et ce premier condensat est entraîné sans reflux substantiel par ledit fluide gazeux, on décharge le mélange résultant de gaz non condensé et du premier condensat dans une zone de séparation de phases,
  • on sépare ledit gaz non condensé dudit premier condensat, dans ladite zone de séparation de phases, on fait circuler le gaz ainsi séparé globalement de bas en haut, dans le premier circuit, ou circuit de reflux, dans des conditions telles qu'une partie du gaz puisse donner un deuxième condensat et que ce deuxième condensat puisse refluer dans ledit premier circuit et être collecté à sa base,
  • on fait circuler une partie au moins du gaz non condensé, déchargé du haut du premier circuit, globalement du haut vers le bas dans le deuxième circuit, à contre-courant du fluide circulant dans le premier circuit et on décharge le gaz purifié résultant,
  • on fait circuler le premier condensat et le deuxième condensat globalement de bas en haut dans au moins un troisième circuit pour y subir un sous-refroidissement,
  • on décharge du haut d'un au moins troisième circuit les premier et deuxième condensats sous-refroidis résultants,
  • on les détend et on les fait circuler globalement du haut vers le bas dans au moins un quatrième circuit où ils se vaporisent en prélevant de la chaleur sur les fluides des premier et troisième circuits et
  • on décharge enfin lesdits condensats vaporisés du bas d'un au moins quatrième circuit, ces condensats vaporisés constituant le gaz séparé,
caractérisé en ce que le premier circuit, ou circuit de reflux, est disposé essentiellement dans une portion supérieure et relativement plus froide de la zone d'échange thermique, le cinquième circuit est disposé essentiellement dans une portion inférieure et relativement moins froide de la zone d'échange thermique et en ce que l'on fait circuler la fraction du fluide gazeux d'alimentaiton globalement de as en haut dans le cinquième circuit pour y effectuer ledit refroidissement et ladite condensation partielle de ladite fraction du fluide gazeux d'alimentation.The process of the invention is a self-refrigerated process for cryogenic fractionation and purification of a gaseous fluid supplying at least two condensable components of different condensation temperatures, respectively at least one relatively heavy component to remove and at least one component relatively light to recover so as to produce a purified gas preferably comprising the relatively light component (s) and a separate gas preferably comprising the relatively heavy component (s), in which:
  • operating in a heat exchange zone forming a unitary assembly and comprising at least five distinct circuits, designated respectively by first, second, third, fourth and fifth circuits, in relation indirect heat exchange with each other at each level of the heat exchange zone, generally vertical,
  • at least a fraction of the gaseous supply fluid is cooled under conditions such that it can partially condense to give a first condensate and this first condensate is entrained without substantial reflux by said gaseous fluid, the resulting mixture of gases is discharged uncondensed and the first condensate in a phase separation zone,
  • separating said uncondensed gas from said first condensate, in said phase separation zone, the gas thus separated is circulated generally from bottom to top, in the first circuit, or reflux circuit, under conditions such that part of the gas can give a second condensate and this second condensate can flow back into said first circuit and be collected at its base,
  • at least part of the uncondensed gas discharged from the top of the first circuit is circulated, generally from top to bottom in the second circuit, against the flow of the fluid flowing in the first circuit and the resulting purified gas is discharged,
  • the first condensate and the second condensate are circulated overall from bottom to top in at least a third circuit to undergo sub-cooling there,
  • the first and second resulting sub-cooled condensates are discharged from the top of at least a third circuit,
  • we relax them and circulate them globally from top to bottom in at least a fourth circuit where they vaporize by taking heat from the fluids of the first and third circuits and
  • finally discharging said vaporized condensates from the bottom of at least a fourth circuit, these vaporized condensates constituting the separated gas,
characterized in that the first circuit, or reflux circuit, is arranged essentially in an upper and relatively cooler portion of the heat exchange zone, the fifth circuit is arranged essentially in a lower and relatively cooler portion of the zone d heat exchange and in that the fraction of the gaseous fluid supplying fluid is circulated overall from as up in the fifth circuit to effect said cooling and said partial condensation of said fraction of the gaseous fluid supply.

Ainsi l'invention met en oeuvre un échangeur de chaleur unitaire (une zone unitaire d'échange de chaleur) tel que défini en revendication 8. L'un des circuits, appelé circuit de reflux ou premier circuit, est disposé essentiellement dans une portion supérieure de l'échangeur (la zone d'échange), c'est-à-dire dans une portion relativement plus froide de l'échangeur. Il s'agit, de préférence, d'un circuit "non tortueux" c'est-à-dire dans lequel le liquide condensé peut ruisseler en sens globalement descendant. Un autre circuit (cinquième circuit), de préférence de type tortueux, non apte au reflux de liquide, est 11disposé essentiellement dans une portion inférieure de l'échangeur (la zone d'échange), c'est-à-dire dans une portion relativement moins froide de l'échangeur.Thus, the invention uses a unitary heat exchanger (a unitary heat exchange zone) as defined in claim 8. One of the circuits, called the reflux circuit or first circuit, is arranged essentially in an upper portion. of the exchanger (the exchange zone), that is to say in a relatively cooler portion of the exchanger. It is preferably a "non-tortuous" circuit, that is to say in which the condensed liquid can flow in a generally descending direction. Another circuit (fifth circuit), preferably of the tortuous type, not suitable for reflux of liquid, is essentially arranged in a lower portion of the exchanger (the exchange zone), that is to say in a portion relatively cooler of the exchanger.

Par circuit de type tortueux, dirigé globalement verticalement, on entend un circuit tel que le fluide qui y est introduit à la base puisse progresser de manière générale du bas vers le haut sans reflux important des portions liquides de ce fluide, ce qui suppose, par exemple, une pente moyenne moins forte que dans le circuit de reflux précité ; en d'autres termes, la totalité ou presque du fluide (liquide et gazeux) suivra un chemin globalement ascendant dans ce circuit de type tortueux et sera recueillie en haut dudit circuit, le point (ou la zone) de décharge étant situé dans une portion intermédiaire de l'échangeur de chaleur, par exemple au voisinage du premier tiers ou de la demi-hauteur de l'échangeur.By circuit of the tortuous type, directed generally vertically, is meant a circuit such that the fluid which is introduced therein at the base can progress generally from the bottom upwards without significant reflux of the liquid portions of this fluid, which supposes, by example, an average slope less steep than in the above-mentioned reflux circuit; in other words, all or almost all of the fluid (liquid and gaseous) will follow a generally ascending path in this circuit of tortuous type and will be collected at the top of said circuit, the point (or zone) of discharge being located in a portion intermediate of the heat exchanger, for example in the vicinity of the first third or half the height of the exchanger.

Il est préférable que le circuit tortueux précité soit en totalité, ou presque en totalité, à un niveau plus bas que le circuit de reflux, et, encore mieux, que les deux circuits soient disposés sensiblement l'un au-dessus de l'autre dans l'échangeur.It is preferable that the aforementioned tortuous circuit is in whole, or almost in whole, at a level lower than the reflux circuit, and, even better, than the two circuits are arranged substantially one above the other in the exchanger.

Les deuxième, troisième et quatrième circuits peuvent être tortueux ou non, de préférence non tortueux.The second, third and fourth circuits can be tortuous or not, preferably non-tortuous.

Il n'est cependant pas indispensable d'utiliser un circuit tortueux et un circuit non tortueux pour obtenir les résultats ci-dessus (reflux et non-reflux respectivement). On peut en effet agir sur la section du circuit et/ou la vitesse de circulation du fluide d'alimentation dans ce circuit. Une vitesse faible dans un canal relativement large permet en effet le reflux tandis qu'une vitesse élevée dans un canal relativement étroit a pour résultat l'entraînement du condensat, l'empêchant ainsi de refluer. Un circuit à multi-canaux de faible section et une grande vitesse de circulation sont donc avantageux, notamment pour le cinquième circuit.However, it is not essential to use a tortuous circuit and a non-tortuous circuit to obtain the above results (reflux and non-reflux respectively). One can indeed act on the section of the circuit and / or the speed of circulation of the supply fluid in this circuit. A low speed in a relatively wide channel allows reflux indeed while a high speed in a relatively narrow channel results in entrainment of the condensate, thus preventing it from backing up. A multi-channel circuit with a small section and a high circulation speed is therefore advantageous, in particular for the fifth circuit.

Les cinq circuits précités sont en relation d'échange thermique les uns avec les autres à chaque niveau de l'échangeur où ils sont présents, ce qui suppose que l'échangeur soit de préférence réalisé dans une matière bonne conductrice de chaleur, avec des parois d'aussi faible épaisseur que possible compatible avec la résistance des matériaux et comportant une surface d'échange élevée. Les spécialistes pourront sans difficulté réaliser de tels échangeurs à partir des indications précédentes.The five aforementioned circuits are in heat exchange relationship with each other at each level of the exchanger where they are present, which supposes that the exchanger is preferably made of a good heat conductive material, with walls as thin as possible compatible with the resistance of the materials and having a high exchange surface. Specialists can easily make such exchangers from the previous indications.

Selon l'invention, le fluide gazeux multi-composants précité (au moins deux et de préférence au moins trois composants condensables) est mis en circulation de bas en haut dans le cinquième circuit, situé dans une portion inférieure de l'échangeur, dans des conditions de température et de pression telles qu'il puisse se condenser en partie sans refluer dans ledit circuit. Le mélange de gaz et de liquide (premier condensat) soutiré du sommet du cinquième circuit est séparé en une phase gazeuse et une phase liquide, dans une zone de séparation. La phase gazeuse résultante est mise en circulation de bas en haut dans le premier circuit (circuit de reflux) situé de préférence au-dessus du cinquième circuit, comme indiqué plus haut. Dans cette portion relativement froide de l'échangeur une partie du gaz se condense et le condensat (deuxième condensat) redescend vers la zone de séparation précitée, ceci en raison du caractère non tortueux de ce premier circuit ou de la faible vitesse ascensionnelle du gaz.According to the invention, the aforementioned multi-component gaseous fluid (at least two and preferably at least three condensable components) is circulated from bottom to top in the fifth circuit, located in a lower portion of the exchanger, in conditions of temperature and pressure such that it can partially condense without backflow into said circuit. The mixture of gas and liquid (first condensate) withdrawn from the top of the fifth circuit is separated into a gas phase and a liquid phase, in a separation zone. The resulting gas phase is circulated from bottom to top in the first circuit (reflux circuit) preferably located above the fifth circuit, as indicated above. In this relatively cold portion of the exchanger, part of the gas condenses and the condensate (second condensate) descends towards the aforementioned separation zone, this due to the non-tortuous nature of this first circuit or the low rate of rise of the gas.

Le deuxième condensat ainsi formé peut être mélangé au premier condensat déjà présent dans la zone de séparation ou être recueilli séparément. Le gaz non condensé recueilli au sommet du premier circuit est renvoyé dans l'échangeur par le deuxième circuit précité pour y circuler du haut vers le bas à contre-courant des fluides circulant dans le premier circuit et dans le cinquième circuit. Il ressort réchauffé en constituant le gaz purifié, formé des éléments les plus volatils du fluide gazeux d'alimentation.The second condensate thus formed can be mixed with the first condensate already present in the separation zone or be collected separately. The uncondensed gas collected at the top of the first circuit is returned to the exchanger by the aforementioned second circuit to circulate there from top to bottom against the current of the fluids circulating in the first circuit and in the fifth circuit. It comes out heated by constituting the purified gas, formed of the most volatile elements of the gaseous supply fluid.

La phase liquide de la zone de séparation, constituée du premier condensat seul ou du mélange des premier et second condensats, est mise en circulation du bas vers le haut dans le troisième circuit précité où elle subit un sous-refroidissement. Elle est alors détendue, statiquement ou dynamiquement, et mise en circulation du haut vers le bas dans le quatrième circuit précité de l'échangeur où elle se vaporise grâce à la chaleur enlevée aux fluides du circuit tortueux, du premier circuit et du troisième circuit. Le courant gazeux déchargé au bas du quatrième circuit renferme les constituants les moins volatils du fluide gazeux d'alimentation. Il peut, si on le désire, être recyclé en partie ou traité autrement.The liquid phase of the separation zone, consisting of the first condensate alone or of the mixture of the first and second condensates, is circulated from the bottom to the top in the aforementioned third circuit where it undergoes sub-cooling. It is then relaxed, statically or dynamically, and circulated from top to bottom in the aforementioned fourth circuit of the exchanger where it vaporizes thanks to the heat removed from the fluids of the tortuous circuit, the first circuit and the third circuit. The gas stream discharged at the bottom of the fourth circuit contains the least volatile constituents of the gaseous supply fluid. It can, if desired, be partially recycled or otherwise treated.

Selon une variante, on peut ne pas mélanger les premier et second condensats et leur faire parcourir séparément les troisième et quatrième circuits, ce qui explique que l'invention utilise "au moins un troisième circuit" et "au moins un quatrième circuit".According to a variant, it is possible not to mix the first and second condensates and have them run through the third and fourth circuits separately, which explains why the invention uses "at least a third circuit" and "at least a fourth circuit".

Le schéma de procédé précité a ainsi permis, sans apport de froid d'origine externe au système, de fractionner un mélange gazeux à basse température, sans perte appréciable de pression pour les constituants les plus volatils de la charge.The abovementioned process diagram thus made it possible, without adding cold from an external source to the system, to fractionate a gas mixture at low temperature, without appreciable loss of pressure for the most volatile constituents of the charge.

Diverses modifications ou variantes peuvent être apportées à l'invention.Various modifications or variants can be made to the invention.

Selon une première variante, une partie seulement de la phase gazeuse recueillie en tête du premier circuit est envoyée dans le deuxième circuit ; l'autre partie est détendue et utilisée dans l'échangeur dans le sens descendant, soit par passage dans un sixième circuit d'échange soit, de préférence, par passage dans le quatrième circuit, en mélange avec la phase liquide détendue du (ou des) condensat(s) qui y est introduite, pour y permettre une vaporisation à pression plus élevée. Dans ce cas la production de gaz purifié sous haute pression est moins importante, mais cela ne présente pas d'inconvénient lorsqu'on procède à un recyclage du courant gazeux issu du quatrième circuit ou à une recompression du courant gazeux du sixième circuit. De préférence 90 à 98% en mole de la phase gazeuse recueillie en tête du premier circuit est envoyée au deuxième circuit et l'autre partie (2 à 10% en mole) est détendue et jointe à ladite phase liquide du quatrième circuit.According to a first variant, only part of the gaseous phase collected at the head of the first circuit is sent to the second circuit; the other part is expanded and used in the heat exchanger in the downward direction, either by passing through a sixth exchange circuit or, preferably, by passing through the fourth circuit, in admixture with the expanded liquid phase of the (or ) condensate (s) introduced therein, to allow vaporization at higher pressure. In this case, the production of purified gas under high pressure is less important, but this does not present any drawback when the gas stream from the fourth circuit is recycled or the gas stream from the sixth circuit is recompressed. Preferably 90 to 98% by mole of the gaseous phase collected at the head of the first circuit is sent to the second circuit and the other part (2 to 10 mol%) is expanded and joined to said liquid phase of the fourth circuit.

Selon une autre variante, une partie du gaz à purifier ne traverse pas le cinquième circuit et est envoyée directement à la zone de séparation gaz-liquide ou au premier circuit. Ceci permet d'adapter le fonctionnement de l'installation aux modifications de composition de la charge. De préférence, dans ce cas, une fraction de 80 à 95% en mole du gaz passe dans le cinquième circuit, et une fraction de 5 à 20% en mole est envoyée à la zone de séparation. On peut ainsi maximiser la quantité de gaz purifié, obtenue par le deuxième circuit.According to another variant, part of the gas to be purified does not pass through the fifth circuit and is sent directly to the gas-liquid separation zone or to the first circuit. This makes it possible to adapt the operation of the installation to changes in the composition of the load. Preferably, in this case, a fraction of 80 to 95 mol% of the gas passes through the fifth circuit, and a fraction of 5 to 20 mol% is sent to the separation zone. It is thus possible to maximize the quantity of purified gas obtained by the second circuit.

Une autre variante encore consiste à effectuer un apport de phase liquide d'origine externe à l'échangeur, dans des conditions où cette phase liquide puisse se détendre et s'évaporer après détente lors de son passage de haut en bas dans l'échangeur. Cette phase liquide d'origine externe peut traverser d'abord l'échangeur de bas en haut par un circuit auxiliaire pour y subir un sous-refroidissement avant de redescendre par un circuit auxiliaire. Ceci est avantageux lors du démarrage de l'installation pour faciliter et accélérer sa mise en froid. Plus simplement, si sa composition est compatible avec celle du liquide du troisième circuit, elle peut être mélangée à ce dernier avant l'entrée de celui-ci dans le troisième circuit ou seulement avant l'entrée dudit liquide dans le quatrième circuit.Yet another variant consists in supplying a liquid phase of external origin to the exchanger, under conditions where this liquid phase can relax and evaporate after expansion during its passage from top to bottom in the exchanger. This liquid phase of external origin can first pass through the exchanger from bottom to top by an auxiliary circuit to undergo sub-cooling there before descending by an auxiliary circuit. This is advantageous when starting the installation to facilitate and accelerate its cooling. More simply, if its composition is compatible with that of the liquid of the third circuit, it can be mixed with the latter before the entry thereof into the third circuit or only before the entry of said liquid into the fourth circuit.

Il est avantageux par ailleurs de régler le taux de condensation du fluide gazeux d'alimentation dans le cinquième circuit à une valeur de 2 à 20% en mole. Les conditions de température et de pression dans la zone d'échange thermique unitaire de l'invention dépendent, bien évidemment, de la composition de la charge d'alimentation, et le technicien saura choisir ces conditions dans chaque cas particulier à l'aide de ses connaissances, l'essentiel étant d'opérer sous des conditions permettant une condensation partielle du fluide d'alimentation. Du fait qu'il s'agit d'un procédé cryogénique, on opère au dessous de la température ambiante, par exemple entre 0°C et -150°C selon le gaz traité et la pression choisie. Comme, par ailleurs, une détente des condensats est prévue, on opère avantageusement à une pression super-atmosphérique, par exemple entre 5 et 100 bars. On trouvera ci-après des valeurs données à titre d'exemples.It is also advantageous to adjust the condensation rate of the gaseous supply fluid in the fifth circuit to a value of 2 to 20% by mole. The temperature and pressure conditions in the unitary heat exchange zone of the invention depend, obviously, the composition of the feedstock, and the technician will be able to choose these conditions in each particular case using his knowledge, the main thing being to operate under conditions allowing partial condensation of the fluid. food. Due to the fact that it is a cryogenic process, the operation is carried out below ambient temperature, for example between 0 ° C. and -150 ° C. depending on the gas treated and the pressure chosen. As, moreover, an expansion of the condensates is provided, one advantageously operates at a super-atmospheric pressure, for example between 5 and 100 bars. Below are values given as examples.

Grâce à un choix judicieux de conditions opératoires, on pourra aisément obtenir un gaz purifié renfermant moins de 1% molaire de composants relativement lourds et un gaz séparé renfermant au moins 30% molaires desdits composants relativement lourds.Thanks to a judicious choice of operating conditions, it is easy to obtain a purified gas containing less than 1 mol% of relatively heavy components and a separate gas containing at least 30 mol% of said relatively heavy components.

L'invention concerne aussi un échangeur de chaleur permettant de mettre en oeuvre le procédé décrit ci-dessus. Cet échangeur est caractérisé en ce qu'il comprend au moins cinq circuits distincts, globalement verticaux, désignés respectivement premier, deuxième, troisième, quatrième et cinquième circuits, en relation d'échange thermique indirect les uns avec les autres à chaque niveau dudit échangeur, lesdits circuits formant un ensemble unitaire, le premier circuit étant de type non tortueux et le cinquième circuit de type tortueux, le premier circuit étant disposé à un niveau supérieur à celui du cinquième circuit, au moins une jonction directe entre le sommet du premier circuit et le sommet du second circuit, au moins une jonction à travers un moyen de détente entre le sommet du troisième circuit et le sommet du quatrième circuit, au moins une zone de séparation de phases reliée par sa partie supérieure à la base du premier circuit, par sa partie inférieure à la base du troisième circuit et latéralement au sommet du cinquième circuit.The invention also relates to a heat exchanger making it possible to implement the method described above. This exchanger is characterized in that it comprises at least five distinct circuits, generally vertical, designated respectively first, second, third, fourth and fifth circuits, in indirect heat exchange relationship with each other at each level of said exchanger, said circuits forming a unitary assembly, the first circuit being of the non-tortuous type and the fifth circuit of the tortuous type, the first circuit being disposed at a level higher than that of the fifth circuit, at least one direct junction between the top of the first circuit and the top of the second circuit, at least one junction through an expansion means between the top of the third circuit and the top of the fourth circuit, at least one zone of separation of phases connected by its upper part to the base of the first circuit, by its lower part to the base of the third circuit and laterally at the top of the fifth circuit.

De préférence, le premier circuit est superposé au cinquième circuit.Preferably, the first circuit is superimposed on the fifth circuit.

Les figures 1 et 2 annexées illustrent l'invention de façon non limitative.Figures 1 and 2 attached illustrate the invention without limitation.

L'échangeur de chaleur E1 comporte cinq circuits principaux C1 à C5 correspondant respectivement aux premier, deuxième, troisième, quatrième et cinquième circuits du procédé. Le gaz à purifier est envoyé par les lignes 1 et 3 au circuit C5 et en ressort par la ligne 2 en phase mixte gaz/premier condensat. Les deux phases se séparent dans le ballon B1 : la phase gazeuse est envoyée par la ligne 16 au circuit C1 ; elle y subit un refroidissement et un second condensat se forme et reflue par la ligne 17. Le gaz non condensé sort en tête et est envoyé par les lignes 5 et 7 au circuit C2. Il ressort réchauffé au bas de ce circuit par la ligne 14. On obtient ainsi le gaz purifié ou la fraction la plus légère de la charge.The heat exchanger E1 has five main circuits C1 to C5 corresponding respectively to the first, second, third, fourth and fifth circuits of the process. The gas to be purified is sent by lines 1 and 3 to the circuit C5 and leaves it by line 2 in the mixed gas / first condensate phase. The two phases separate in the flask B1: the gas phase is sent by line 16 to the circuit C1; it undergoes cooling there and a second condensate forms and flows back through line 17. The uncondensed gas leaves at the head and is sent by lines 5 and 7 to circuit C2. It comes out warmed at the bottom of this circuit by line 14. This gives the purified gas or the lightest fraction of the charge.

Les condensats provenant des circuits C5 et C1 respectivement par les lignes 2 et 17 sont mélangés et envoyés par la ligne 4 au circuit C3 où ils subissent un sous-refroidissement. Ils ressortent en tête par la ligne 8, traversent la vanne de détente V1 et sont envoyés au circuit C4 par la ligne 9. Ils peuvent traverser un ballon B2, auquel cas la phase gazeuse et la phase liquide sont acheminées à C4 respectivement par les lignes 18 et 19 vers le point 10. Les condensats vaporisés sortent du circuit C4 par la ligne 11. Il s'agit des fractions les moins volatiles de la charge.The condensates coming from circuits C5 and C1 respectively by lines 2 and 17 are mixed and sent by line 4 to circuit C3 where they undergo sub-cooling. They come out at the head by line 8, pass through the expansion valve V1 and are sent to circuit C4 by line 9. They can pass through a balloon B2, in which case the gas phase and the liquid phase are sent to C4 respectively by the lines 18 and 19 to point 10. The condensates vaporized leaves the circuit C4 via line 11. These are the least volatile fractions of the charge.

Selon la première variante, une partie du gaz issu du circuit C1 est prélevé sur la ligne 5 et envoyé à travers la vanne de détente V2 et la ligne 6 au ballon B2.According to the first variant, part of the gas from the circuit C1 is taken from line 5 and sent through the expansion valve V2 and line 6 to the cylinder B2.

Selon la seconde variante, une partie du gaz de départ est envoyée au ballon B1 à travers la ligne 15 et la vanne V4.According to the second variant, part of the starting gas is sent to the balloon B1 through the line 15 and the valve V4.

Selon la troisième variante, une phase liquide compatible avec le condensat de la ligne 4 est envoyée par la ligne 12 à un circuit auxiliaire C6 pour y subir un sous-refroidissement avant passage dans la ligne 13 et la vanne de détente V3 et envoi au ballon B2, de préférence par la ligne 9.According to the third variant, a liquid phase compatible with the condensate of line 4 is sent by line 12 to an auxiliary circuit C6 to undergo sub-cooling there before passing through line 13 and the expansion valve V3 and sent to the balloon. B2, preferably by line 9.

Sur la figure 2, on retrouve l'ensemble échangeur unitaire E1, comportant une pluralité de circuits remplissant, par groupes, la même fonction. Ainsi le circuit C1 de la figure 1 est subdivisé en C1, C1' et C1'', le circuit C2 est subdivisé en C2, C2', C2", etc. Chaque circuit est séparé du circuit voisin par une tôle verticale telles les tôles 20, 21, 22, etc. De préférence, chaque circuit est de type multi-canaux. Les circuits C1 et C3 en sont des exemples. On y voit en effet des tôles verticales telles que 23 (tôle ondulée) ou 24 (cloison plate) divisant les circuits en une pluralité de canaux élémentaires tels que 25 et 26.In FIG. 2, we find the unitary exchanger assembly E1, comprising a plurality of circuits fulfilling, by groups, the same function. Thus the circuit C1 of FIG. 1 is subdivided into C1, C1 'and C1' ', the circuit C2 is subdivided into C2, C2', C2 ", etc. Each circuit is separated from the neighboring circuit by a vertical sheet like the sheets 20, 21, 22, etc. Preferably, each circuit is of the multi-channel type, circuits C1 and C3 being examples of this, in fact we see vertical sheets such as 23 (corrugated sheet) or 24 (flat partition). ) dividing the circuits into a plurality of elementary channels such as 25 and 26.

On retrouve latéralement la sortie des canaux 2, 16 et 17 relatifs aux cinquième (2) et premier (16 et 17) circuits de la figure 1, avec leurs équivalents 2', 16', 17', 2'', 16'' et 17". On n'a pas représenté les collecteurs placés à la partie supérieure et à la partie inférieure de l'échangeur E1 étant donné qu'ils sont de type classique. Par exemple, l'un des collecteurs réunira les effluents des circuits C1, C1' et C1''; de même pour C2, C2' et C2", etc. Les conduits latéraux 2, 16, 17 (et leurs équivalents prime et seconde) sont reliés à des ballons B1 distincts ou à un ballon B1 allongé commun.We find laterally the output of channels 2, 16 and 17 relating to the fifth (2) and first (16 and 17) circuits of Figure 1, with their equivalents 2 ', 16', 17 ', 2'',16'' and 17 ". The collectors placed at the upper part and at the lower part of the exchanger E1 since they are of the conventional type. For example, one of the collectors will bring together the effluents from circuits C1, C1 'and C1''; the same for C2, C2 'and C2 ", etc. The lateral conduits 2, 16, 17 (and their prime and second equivalents) are connected to separate balloons B1 or to a common elongated balloon B1.

L'ordre de succession des circuits décrits ci-dessus, à savoir C1, C2, C3, C4, C5 n'est pas essentiel et toute autre combinaison peut être envisagée. Par exemple, on pourra avoir l'ordre C1, C4, C3, C2, C5 ou C2, C4, C1, C3, C5, etc... étant entendu que de préférence C1 est superposé à C5.The order of succession of the circuits described above, namely C1, C2, C3, C4, C5 is not essential and any other combination can be envisaged. For example, we can have the order C1, C4, C3, C2, C5 or C2, C4, C1, C3, C5, etc ... it being understood that preferably C1 is superimposed on C5.

Les exemples 1 à 4 suivants, donnés à titre non limitatif, illustrent l'invention.The following examples 1 to 4, given without limitation, illustrate the invention.

EXEMPLE 1EXAMPLE 1

On traite un gaz disponible à -93°C sous 35 bar abs. Sa composition est donnée dans le tableau 1. Son débit est de 121,788 kmol/h.An available gas is treated at -93 ° C under 35 bar abs. Its composition is given in table 1. Its flow rate is 121.788 kmol / h.

Les conditions de température et pression aux différents points des circuits sont données dans le tableau 5.The temperature and pressure conditions at the various points of the circuits are given in table 5.

Les vannes V2, V3 et V4 sont fermées.Valves V2, V3 and V4 are closed.

On recueille, dans la ligne 6,111,703 kmol/h de gaz enrichi en hydrogène et renfermant moins de 1% molaire d'éthylène, sous une pression de 34,7 bar abs et 10,086 kmol/h de gaz fortement enrichi en éthylène dans la ligne 12 sous une pression de 1,8 bar abs. Ce dernier gaz peut être envoyé à une colonne de distillation pour obtenir un courant encore plus riche en éthylène. Les compositions des courants de l'installation figurent au tableau 1.Line 6,111,703 kmol / h of hydrogen-enriched gas containing less than 1 mol% of ethylene is collected under a pressure of 34.7 bar abs and 10.086 kmol / h of gas highly enriched in ethylene in line 12 under a pressure of 1.8 bar abs. The latter gas can be sent to a distillation column to obtain an even richer stream of ethylene. The current compositions of the installation are shown in Table 1.

EXEMPLE 2EXAMPLE 2

On opère comme dans l'exemple 1 en ouvrant toutefois partiellement la vanne V2 pour permettre la vaporisation du fluide circulant le circuit 4 à pression plus élevée.The procedure is as in Example 1, however, partially opening the valve V2 to allow the vaporization of the fluid circulating in the circuit 4 at higher pressure.

Les tableaux 2 et 6 donnent respectivement les compositions des fluides, à l'entrée et à la sortie, et les conditions opératoires.Tables 2 and 6 give respectively the compositions of the fluids, at the inlet and at the outlet, and the operating conditions.

EXEMPLE 3EXAMPLE 3

On opère comme dans l'exemple 2 avec, en outre, ouverture partielle de la vanne V4. Les tableaux 3 et 7 donnent les compositions des fluides et les conditions opératoires.The procedure is as in Example 2 with, in addition, partial opening of the valve V4. Tables 3 and 7 give the compositions of the fluids and the operating conditions.

EXEMPLE 4EXAMPLE 4

On opère comme dans l'exemple 3 avec, en outre, ouverture partielle de la vanne V3 permettant l'introduction d'un distillat constitué d'un mélange 50/50 en volume de méthane et d'éthylène, obtenu par rectification du gaz purifié d'une opération antérieure.The procedure is as in Example 3 with, in addition, partial opening of the valve V3 allowing the introduction of a distillate consisting of a 50/50 mixture by volume of methane and ethylene, obtained by rectification of the purified gas from a previous operation.

Un tel mode de fonctionnement est utilisé lors du démarrage de l'installation pour faciliter sa mise en froid.Such an operating mode is used when starting the installation to facilitate its cooling.

Les tableaux 4 et 8 donnent les compositions des fluides et les conditions opératoires. TABLEAU 1 Gaz à purifier
(ligne 1) Gaz purifié
(ligne 14) Gaz séparé
(ligne 11) Composition molaire Hydrogène % mol 62,3100 67,7567 1,9871 Oxyde de carbone % mol 0,3814 0,4073 0,0941 Méthane % mol 31,3551 31,0198 35,0688 Acétylène % mol 0,0369 0,0013 0,4312 Ethylène % mol 5,4370 0,8057 56,7295 Ethane % mol 0,4784 0,0092 5,6743 Propylène % mol 0,0012 0,0000 0,0149 Température °C -93,00 -95,00 -100,00 Pression bar abs 35,00 34,70 1,80 Débit molaire Kmol/h 121,788 111,703 10,086 TABLEAU 2 Gaz à purifier
(ligne 1) Gaz purifié
(ligne 14) Gaz séparé
(ligne 11) Composition molaire Hydrogène % mol 62,3100 67,7566 12,8710 Oxyde de carbone % mol 0,3814 0,4073 0,1460 Méthane % mol 31,3551 31,0198 34,3984 Acétylène % mol 0,0369 0,0013 0,3600 Ethylène % mol 5,4370 0,8057 47,4753 Ethane % mol 0,4784 0,0092 4,7369 Propylène % mol 0,0012 0,0000 0,0124 Température °C -93,00 -95,00 -98,30 Pression bar abs 35,00 34,70 2,40 Débit molaire Kmol/h 121,788 109,703 12,086 TABLEAU 3 Gaz à purifier
(ligne 1) Gaz purifié
(ligne 14) Gaz séparé
(ligne 11) Composition molaire Hydrogène % mol 62,3100 67,4592 18,7556 Oxyde de carbone % mol 0,3814 0,4066 0,1682 Méthane % mol 31,3551 31,3225 31,6311 Acétylène % mol 0,0369 0,0012 0,3385 Ethylène % mol 5,4370 0,8021 44,6420 Ethane % mol 0,4784 0,0085 4,4529 Propylène % mol 0,0012 0,0000 0,0116 Température °c -93,00 -95,00 -99,39 Pression bar abs 35,00 34,70 2,40 Débit molaire Kmol/h 121,788 108,912 12,876 TABLEAU 4 Gaz à purifier
(ligne 1) Gaz purifié
(ligne 14) Gaz séparé
(ligne 11) Distillat
(ligne 12) Composition molaire Hydrogène % mol 62,3100 67,4592 9,1827 0,0000 Oxyde de carbone % mol 0,3814 0,4066 0,1097 0,0000 Méthane % mol 31,3551 31,3225 34,4823 50,0000 Acétylène % mol 0,0369 0,0012 0,3332 0,0000 Ethylène % mol 5,4370 0,8021 51,4970 50,0000 Ethane % mol 0,4784 0,0085 4,3836 0,0000 Propylène % mol 0,0012 0,0000 0,0115 0,0000 Température  °c -93,00 -95,00 -99,19 -92,00 Pression bar abs 35,00 34,70 2,40 17,80 Débit molaire Kmol/h 121,788 108,912 13,076 2,000 TABLEAU 5 Désignation Flux n° Température °C Pression bar abs. Débit Kmol/h Gaz à purifier 1 -93,00 35,00 121,788 Gaz à purifier réfrigéré 2 -100,00 34,90 121,788 Gaz à purifier alimentant E1 3 -93,00 35,00 121,788 Liquide de B1 4 -101,47 34,90 10,086 Gaz purifié 5 -120,35 34,80 111,703 Gaz purifié injecté dans B2 6 -120,35 34,80 0,000 Gaz purifié réintroduit dans E1 7 -120,35 34,80 111,703 Liquide de B1 réfrigéré 8 -120,00 34,80 10,086 Alimentation de B2 9 -136,57 1,90 10,086 Gaz purifié 10 -136,57 1,90 10,086 Gaz purifié réchauffé 11 -100,00 1,80 10,086 Distillat 12 0,000 Distillat réfrigéré 13 0,000 Gaz purifié réchauffé 14 -95,00 34,70 111,703 Gaz à purifier injecté dans B1 15 -93,00 35,00 0,000 TABLEAU 6 Désignation Flux n° Température °C Pression bar abs. Débit Kmol/h Gaz à purifier 1 -93,00 35,00 121,788 Gaz à purifier réfrigéré 2 -100,00 34,90 121,788 Gaz à purifier alimentant E1 3 -93,00 35,00 121,788 Liquide de B1 4 -101,47 34,90 10,086 Gaz purifié 5 -120,35 34,80 111,703 Gaz purifié injecté dans B2 6 -120,35 34,80 0,000 Gaz purifié réintroduit dans E1 7 -120,35 34,80 111,703 Liquide de B1 réfrigéré 8 -120,00 34,80 10,086 Alimentation de B2 9 -136,57 2,50 12,086 Gaz purifié 10 -136,57 2,50 12,086 Gaz purifié réchauffé 11 -100,00 2,40 12,086 Distillat 12 0,000 Distillat réfrigéré 13 0,000 Gaz purifié réchauffé 14 -95,00 34,70 109,703 Gaz à purifier injecté dans B1 15 -93,00 35,00 0,000 TABLEAU 7 Désignation Flux n° Température °C Pression bar abs. Débit Kmol/h Gaz à purifier 1 -93,00 35,00 121,788 Gaz à purifier réfrigéré 2 -100,00 34,90 101,788 Gaz à purifier alimentant E1 3 -93,00 35,00 101,788 Liquide de B1 4 -96,75 34,90 9,576 Gaz purifié 5 -120,30 34,80 112,212 Gaz purifié injecté dans B2 6 120,30 34,80 3,300 Gaz purifié réintroduit dans E1 7 -120,30 34,80 108,912 Liquide de B1 réfrigéré 8 -120,00 34,80 9,576 Alimentation de B2 9 -137,56 2,50 12,876 Gaz purifié 10 -137,56 2,50 12,876 Gaz purifié réchauffé 11 -99,39 2,40 12,876 Distillat 12 0,000 Distillat réfrigéré 13 0,000 Gaz purifié réchauffé 14 -95,00 34,70 108,912 Gaz à purifier injecté dans B1 15 -93,00 35,00 20,000 TABLEAU 8 Désignation Flux n° Température °C Pression bar abs. Débit Kmol/h Gaz à purifier 1 -93,00 35,00 121,788 Gaz à purifier réfrigéré 2 -100,00 34,90 101,788 Gaz à purifier alimentant E1 3 -93,00 35,00 101,788 Liquide de B1 4 -96,75 34,90 9,576 Gaz purifié 5 -120,30 34,80 112,212 Gaz purifié injecté dans B2 6 -120,30 34,80 1,500 Gaz purifié réintroduit dans E1 7 -120,30 34,80 110,712 Liquide de B1 réfrigéré 8 -120,00 34,80 9,576 Alimentation de B2 9 -137,56 2,50 13,076 Gaz purifié 10 -136,87 2,50 13,076 Gaz purifié réchauffé 11 -99,19 2,40 13,076 Distillat 12 -92,00 17,76 2,000 Distillat réfrigéré 13 -120,00 17,66 2,000 Gaz purifié réchauffé 14 -95,00 34,70 110,712 Gaz à purifier injecté dans B1 15 -93,00 35,00 20,000 Tables 4 and 8 give the compositions of the fluids and the operating conditions. TABLE 1 Gas to be purified
(line 1) Purified gas
(line 14) Separate gas
(line 11) Molar composition Hydrogen % mol 62.3100 67.7567 1.9871 Carbon monoxide % mol 0.3814 0.4073 0.0941 Methane % mol 31.3551 31.0198 35.0688 Acetylene % mol 0.0369 0.0013 0.4312 Ethylene % mol 5.4370 0.8057 56.7295 Ethane % mol 0.4784 0.0092 5.6743 Propylene % mol 0.0012 0.0000 0.0149 Temperature ° C -93.00 -95.00 -100.00 Pressure abs bar 35.00 34.70 1.80 Molar flow Kmol / h 121,788 111.703 10,086 Gas to be purified
(line 1) Purified gas
(line 14) Separate gas
(line 11) Molar composition Hydrogen % mol 62.3100 67.7566 12.8710 Carbon monoxide % mol 0.3814 0.4073 0.1460 Methane % mol 31.3551 31.0198 34.3984 Acetylene % mol 0.0369 0.0013 0.3600 Ethylene % mol 5.4370 0.8057 47.4753 Ethane % mol 0.4784 0.0092 4.7369 Propylene % mol 0.0012 0.0000 0.0124 Temperature ° C -93.00 -95.00 -98.30 Pressure abs bar 35.00 34.70 2.40 Molar flow Kmol / h 121,788 109.703 12,086 Gas to be purified
(line 1) Purified gas
(line 14) Separate gas
(line 11) Molar composition Hydrogen % mol 62.3100 67.4592 18.7556 Carbon monoxide % mol 0.3814 0.4066 0.1682 Methane % mol 31.3551 31.3225 31.6311 Acetylene % mol 0.0369 0.0012 0.3385 Ethylene % mol 5.4370 0.8021 44.6420 Ethane % mol 0.4784 0.0085 4.4529 Propylene % mol 0.0012 0.0000 0.0116 Temperature ° c -93.00 -95.00 -99.39 Pressure abs bar 35.00 34.70 2.40 Molar flow Kmol / h 121,788 108,912 12,876 Gas to be purified
(line 1) Purified gas
(line 14) Separate gas
(line 11) Distillate
(line 12) Molar composition Hydrogen % mol 62.3100 67.4592 9.1827 0.0000 Carbon monoxide % mol 0.3814 0.4066 0.1097 0.0000 Methane % mol 31.3551 31.3225 34.4823 50.0000 Acetylene % mol 0.0369 0.0012 0.3332 0.0000 Ethylene % mol 5.4370 0.8021 51.4970 50.0000 Ethane % mol 0.4784 0.0085 4.3836 0.0000 Propylene % mol 0.0012 0.0000 0.0115 0.0000 Temperature ° c -93.00 -95.00 -99.19 -92.00 Pressure abs bar 35.00 34.70 2.40 17.80 Molar flow Kmol / h 121,788 108,912 13,076 2,000 Designation Stream # Temperature ° C Pressure bar abs. Kmol / h flow Gas to be purified 1 -93.00 35.00 121,788 Refrigerated gas to be purified 2 -100.00 34.90 121,788 Gas to be purified supplying E1 3 -93.00 35.00 121,788 B1 liquid 4 -101.47 34.90 10,086 Purified gas 5 -120.35 34.80 111.703 Purified gas injected into B2 6 -120.35 34.80 0,000 Purified gas reintroduced into E1 7 -120.35 34.80 111.703 Refrigerated B1 liquid 8 -120.00 34.80 10,086 B2 feeding 9 -136.57 1.90 10,086 Purified gas 10 -136.57 1.90 10,086 Purified gas heated 11 -100.00 1.80 10,086 Distillate 12 0,000 Chilled distillate 13 0,000 Purified gas heated 14 -95.00 34.70 111.703 Gas to be purified injected into B1 15 -93.00 35.00 0,000 Designation Stream # Temperature ° C Pressure bar abs. Kmol / h flow Gas to be purified 1 -93.00 35.00 121,788 Refrigerated gas to be purified 2 -100.00 34.90 121,788 Gas to be purified supplying E1 3 -93.00 35.00 121,788 B1 liquid 4 -101.47 34.90 10,086 Purified gas 5 -120.35 34.80 111.703 Purified gas injected into B2 6 -120.35 34.80 0,000 Purified gas reintroduced into E1 7 -120.35 34.80 111.703 Refrigerated B1 liquid 8 -120.00 34.80 10,086 B2 feeding 9 -136.57 2.50 12,086 Purified gas 10 -136.57 2.50 12,086 Purified gas heated 11 -100.00 2.40 12,086 Distillate 12 0,000 Chilled distillate 13 0,000 Purified gas heated 14 -95.00 34.70 109.703 Gas to be purified injected into B1 15 -93.00 35.00 0,000 Designation Stream # Temperature ° C Pressure bar abs. Kmol / h flow Gas to be purified 1 -93.00 35.00 121,788 Refrigerated gas to be purified 2 -100.00 34.90 101,788 Gas to be purified supplying E1 3 -93.00 35.00 101,788 B1 liquid 4 -96.75 34.90 9.576 Purified gas 5 -120.30 34.80 112,212 Purified gas injected into B2 6 120.30 34.80 3,300 Purified gas reintroduced into E1 7 -120.30 34.80 108,912 Refrigerated B1 liquid 8 -120.00 34.80 9.576 B2 feeding 9 -137.56 2.50 12,876 Purified gas 10 -137.56 2.50 12,876 Purified gas heated 11 -99.39 2.40 12,876 Distillate 12 0,000 Chilled distillate 13 0,000 Purified gas heated 14 -95.00 34.70 108,912 Gas to be purified injected into B1 15 -93.00 35.00 20,000 Designation Stream # Temperature ° C Pressure bar abs. Kmol / h flow Gas to be purified 1 -93.00 35.00 121,788 Refrigerated gas to be purified 2 -100.00 34.90 101,788 Gas to be purified supplying E1 3 -93.00 35.00 101,788 B1 liquid 4 -96.75 34.90 9.576 Purified gas 5 -120.30 34.80 112,212 Purified gas injected into B2 6 -120.30 34.80 1,500 Purified gas reintroduced into E1 7 -120.30 34.80 110,712 Refrigerated B1 liquid 8 -120.00 34.80 9.576 B2 feeding 9 -137.56 2.50 13,076 Purified gas 10 -136.87 2.50 13,076 Purified gas heated 11 -99.19 2.40 13,076 Distillate 12 -92.00 17.76 2,000 Chilled distillate 13 -120.00 17.66 2,000 Purified gas heated 14 -95.00 34.70 110,712 Gas to be purified injected into B1 15 -93.00 35.00 20,000

Claims (10)

  1. Self-refrigerating method of cryogenic fractionation and purification of a gaseous feed fluid with at least two condensable components with differing condensation temperatures, at least one relatively heavy component to be removed and at least one relatively light component to be recovered, respectively, so as to produce a purified gas preferentially comprising the relatively light component(s) and a separated gas preferentially comprising the relatively heavy component(s), wherein :
    - one operates in a thermal exchange zone forming a unitary system and comprising at least five distinct globally vertical circuits called first, second, third, fourth and fifth circuits, respectively, in indirect thermal exchange relationship with each other at each level of the thermal exchange zone,
    - one cools at least one fraction of the gaseous feed fluid under conditions such that it may condense in part to give a first condensate and this first condensate is carried along without any substantial reflux by the said gaseous fluid, one discharges the resulting non-condensed mixture of gas and of the first condensate into a phase separation zone,
    - one separates the said non-condensed gas from the said first condensate within the said phase separation zone, one causes the thus separated gas to circulate globally from bottom to top in a first circuit or reflux circuit under conditions such that one part of the gas may give a second condensate and that this second condensate may flow back into the said first circuit and be collected at its base,
    - one causes at least one part of the non-condensed gas discharged from the top of the first circuit to circulate globally from top to bottom in the second circuit in counter-current with the fluid circulating in the first circuit and one discharges the resulting purified gas,
    - one causes the first condensate and the second condensate to circulate globally from bottom to top in at least one third circuit for undergoing a a sub-cooling there,
    - one discharges from the top of at least one third circuit the resulting sub-cooled first and second condensates,
    - one expands them and one causes them to circulate globally from top to bottom in at least one fourth circuit where they are vaporizing by taking the heat from the fluids of the first and third circuits and
    - one at last discharges the said vaporized condensates from the bottom of at least one fourth circuit, these vaporized condensates constituting the separated gas,
    characterized in that the first circuit or reflux circuit is disposed essentially in an upper relatively colder portion of the thermal exchange zone, the fifth circuit is disposed essentially in a lower relatively less colder portion of the thermal exchange zone and in that one causes the fraction of the gaseous feed fluid to circulate globally from bottom to top in the fifth circuit for there effecting the said cooling and the said partial condensation of the said fraction of the gaseous feed fluid.
  2. Method according to claim 1, wherein one operates under conditions such that the purified gas contains at least one molar percent of the relatively heavy components and that the separated gas contains at least 30 molar percent of the said relatively heavy components.
  3. Method according to claim 1 or 2, wherein one fraction equal to 90 to 98 molar percent of the non-condensed gas discharged from the top of the first circuit is caused to circulate in the second circuit and another fraction of the said gas representing from 2 to 10 molar percent of the said non-condensed gas is expanded and caused to circulate after expansion in the heat exchange zone in the direction globally from top to bottom as a mixture with the first condensate or the second condensate or both of them to there allow a vaporization at a higher pressure of the said condensate(s).
  4. Method according one of claims 1 to 3, wherein a fraction equal to 5 to 20 molar percent of the gaseous feed fluid does not flow through the fifth circuit and is conveyed directly into the said phase separation zone.
  5. Method according to claim 4, wherein one varies the portion of gaseous feed fluid carried directly to the phase separation zone in response to the variations in composition of the said gaseous feed fluid so as to maximize the amount of purified gas obtained from the second circuit.
  6. Method according to one of claims 1 to 5, wherein one carries out a supply of liquid phase of external origin to the heat exchange zone during the start up of the equipment to facilitate its being put in a cold condition under conditions where this liquid phase may evaporate after expansion and flow through the heat exchange zone from top to bottom.
  7. Method according to one of claims 1 to 6, wherein one condenses from 2 to 20 molar percent of the gaseous feed fluid in the fifth circuit.
  8. Heat exchanger permitting a self-refrigerated reflux purification of gas for carrying out the method according to one of claims 1 to 7, comprising at least five globally vertical distinct circuits called first, second, third, fourth and fifth circuits (C1, C2, C3, C4, C5), respectively, in indirect thermal exchange relationship with each other at each level of the said exchanger, characterized in that the said circuits form a unitary system, the first circuit (C1) being of the non-tortuous type and the fifth circuit (C5) being of the tortuous type, the first circuit being disposed at a level higher than that of the fifth circuit, the said exchanger moreover comprising at least one direct junction (7) between the top of the first circuit and the top of the second circuit, at least one junction across one expansion means (V1) between the top of the third circuit and the top of the fourth circuit, at least one phase separation zone (B1) connected with its upper portion to the base of the first circuit, by its lower portion to the base of the third circuit and sidewise to the top of the fifth circuit.
  9. Exchanger according to claim 8, wherein the first circuit is superposed to the fifth circuit.
  10. Exchanger according to claim 8 or 9, wherein at least one part of the circuits is of the multiple channel type.
EP94401517A 1993-07-15 1994-07-01 Self-refrigerating process for cryogenic fractionation and purification of gas and heat exchanger for carrying out the process Expired - Lifetime EP0634618B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9308695A FR2707745B1 (en) 1993-07-15 1993-07-15 Self-refrigerating cryogenic fractionation and gas purification process and heat exchanger for implementing this process.
FR9308695 1993-07-15

Publications (2)

Publication Number Publication Date
EP0634618A1 EP0634618A1 (en) 1995-01-18
EP0634618B1 true EP0634618B1 (en) 1997-09-03

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94401517A Expired - Lifetime EP0634618B1 (en) 1993-07-15 1994-07-01 Self-refrigerating process for cryogenic fractionation and purification of gas and heat exchanger for carrying out the process

Country Status (12)

Country Link
US (1) US5461870A (en)
EP (1) EP0634618B1 (en)
JP (1) JPH07167556A (en)
KR (1) KR950003753A (en)
CN (1) CN1102879A (en)
BR (1) BR9402812A (en)
CO (1) CO4410270A1 (en)
DE (1) DE69405330T2 (en)
ES (1) ES2109631T3 (en)
FR (1) FR2707745B1 (en)
MY (1) MY111414A (en)
RU (1) RU2126519C1 (en)

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GB9503592D0 (en) * 1995-02-23 1995-04-12 Boc Group Plc Separation of gas mixtures
CN1055026C (en) * 1995-08-10 2000-08-02 抚顺石油化工公司石油二厂 On-line optimizing and controlling method of balanced microcomputer for producing processed materials by gas separation unit
US5596883A (en) * 1995-10-03 1997-01-28 Air Products And Chemicals, Inc. Light component stripping in plate-fin heat exchangers
DE19645077C1 (en) * 1996-10-31 1997-10-16 Paul Haslauer Treatment installation for steam bath, e.g. sauna
US5937656A (en) * 1997-05-07 1999-08-17 Praxair Technology, Inc. Nonfreezing heat exchanger
US5802871A (en) * 1997-10-16 1998-09-08 Air Products And Chemicals, Inc. Dephlegmator process for nitrogen removal from natural gas
CN1186942A (en) * 1997-10-27 1998-07-08 易元明 Technical method for industrial waste gas deep cooling and purifying and power generation and its device
US6212906B1 (en) 2000-02-16 2001-04-10 Praxair Technology, Inc. Cryogenic reflux condenser system for producing oxygen-enriched air
US6237366B1 (en) * 2000-04-14 2001-05-29 Praxair Technology, Inc. Cryogenic air separation system using an integrated core
US6295836B1 (en) * 2000-04-14 2001-10-02 Praxair Technology, Inc. Cryogenic air separation system with integrated mass and heat transfer
US6266977B1 (en) 2000-04-19 2001-07-31 Air Products And Chemicals, Inc. Nitrogen refrigerated process for the recovery of C2+ Hydrocarbons
FR2808460B1 (en) * 2000-05-02 2002-08-09 Inst Francais Du Petrole METHOD AND DEVICE FOR SEPARATING AT LEAST ONE ACID GAS CONTAINED IN A GAS MIXTURE
US6351969B1 (en) * 2001-01-31 2002-03-05 Praxair Technology, Inc. Cryogenic nitrogen production system using a single brazement
KR20020029659A (en) * 2002-03-07 2002-04-19 서영석 Portable Reverse Osmosis Water Purifier with Midnight Power
US7263859B2 (en) * 2004-12-27 2007-09-04 L'air Liquide, Societe Anonyme A Directoire Et Conseil De Surveillance Pour L'etude Et L'exploitation Des Procedes Georges Claude Process and apparatus for cooling a stream of compressed air
US7481074B2 (en) * 2006-03-01 2009-01-27 Air Products And Chemicals, Inc. Self-contained distillation purifier/superheater for liquid-fill product container and delivery systems
JP2010501657A (en) * 2006-08-23 2010-01-21 シエル・インターナシヨネイル・リサーチ・マーチヤツピイ・ベー・ウイ Method and apparatus for treating hydrocarbon streams
FR2920529B1 (en) * 2007-09-04 2009-12-11 Total Sa METHOD FOR STARTING A HYDROCARBON MIXED REFRIGERATION CYCLE.

Family Cites Families (6)

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FR2384221A1 (en) * 1977-03-16 1978-10-13 Air Liquide PLATE EXCHANGER TYPE HEAT EXCHANGE ASSEMBLY
US4721164A (en) * 1986-09-04 1988-01-26 Air Products And Chemicals, Inc. Method of heat exchange for variable-content nitrogen rejection units
US5017204A (en) * 1990-01-25 1991-05-21 Air Products And Chemicals, Inc. Dephlegmator process for the recovery of helium
FR2665755B1 (en) * 1990-08-07 1993-06-18 Air Liquide NITROGEN PRODUCTION APPARATUS.
US5122174A (en) * 1991-03-01 1992-06-16 Air Products And Chemicals, Inc. Boiling process and a heat exchanger for use in the process
US5291738A (en) * 1992-12-07 1994-03-08 Edwards Engineering Corp. Vapor recovery apparatus and method

Also Published As

Publication number Publication date
RU94026286A (en) 1996-08-10
EP0634618A1 (en) 1995-01-18
JPH07167556A (en) 1995-07-04
US5461870A (en) 1995-10-31
CO4410270A1 (en) 1997-01-09
MY111414A (en) 2000-04-29
FR2707745B1 (en) 1995-10-06
FR2707745A1 (en) 1995-01-20
BR9402812A (en) 1995-04-04
KR950003753A (en) 1995-02-17
ES2109631T3 (en) 1998-01-16
DE69405330D1 (en) 1997-10-09
CN1102879A (en) 1995-05-24
RU2126519C1 (en) 1999-02-20
DE69405330T2 (en) 1998-04-02

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