Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
  • B01D53/229—Integrated processes (Diffusion and at least one other process, e.g. adsorption, absorption)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
  • B01D53/1487—Removing organic compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/75—Multi-step processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2256/00—Main component in the product gas stream after treatment
  • B01D2256/24—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/50—Carbon oxides
  • B01D2257/504—Carbon dioxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/702—Hydrocarbons
  • B01D2257/7022—Aliphatic hydrocarbons
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

• the invention relates to a method and a device for separating gaseous mixtures by permeation.
• Semipermeable membranes based on hollow polymer fibers are used in many separation units, for example for the treatment of natural gas, the manufacture of ammonia or methanol, the purification of hydrogen or biogas, etc.
• the performance of the selective permeation separation units can deteriorate progressively due to the presence of certain compounds, generally minority, in their feed stream. These compounds, which we will call “poisons", can also lead to premature aging of the membranes, which can go as far as their rapid destruction. Different solutions exist to treat this phenomenon.
• the permeation separation unit is on a recycling loop of a process for the synthesis of methanol or ammonia and is placed downstream of a pre-treatment unit of the following type.
• PSA Pressure Swing Adsorption
• US-B-7318854 discloses a pre-treatment for absorbing the carbon dioxide contained in the feed stream of modules comprising polypropylene membranes.
• the absorbent used is confined in the shell part of the membrane module, outside the polypropylene hollow fibers.
• the process has the disadvantage of being cyclic. Indeed, a phase of regeneration of the absorbent by passage of a purge gas is necessary after a production phase of 8 hours. Due to the cyclic nature of the process, a large area of membranes must be installed.
• the direct contact of the absorbent with the constituent elements of the membrane module (polymer fibers of the membranes, sealing materials) requires a total compatibility of the materials and restricts the possible choices for the absorbent.
• the document FR 07 04708 describes a deacidification process for a natural gas comprising hydrocarbons, hydrogen sulphide (H 2 S) and water.
• the natural gas is first depleted of water during an absorption step with a liquid rich in H 2 S.
• the pressure of the contacting zone of the natural gas and the H 2 S rich liquid is between 45 and 75 bar.
• This depleted gas is then separated through a membrane to obtain a retentate depleted of hydrogen sulfide.
• the pressure of the separation step through the membrane is not disclosed.
• US 2004/0099138 A1 discloses a process for producing high purity methane from natural gas. This process comprises a step of separation of heavy hydrocarbon compounds from natural gas by high pressure absorption, greater than 5.5 MPa.
• the absorbent is a stream rich in carbon dioxide.
• the flow of natural gas that is low in heavy hydrocarbons is then separated through a membrane so as to obtain a retentate depleted of carbon dioxide.
• the pressure of the separation step through the membrane is not disclosed.
• US 2008/0078294 A1 discloses a process for separating hydrogen sulphide, carbon dioxide and hydrogen from a stream. This process includes a step of separating the hydrogen sulfide by absorption with a solvent to produce a low hydrogen sulfide stream. This low hydrogen sulfide stream is then separated through a membrane to obtain a hydrogen-rich permeate. The pressure of the different separation steps are not disclosed.
• An object of the invention is to overcome all or part of the disadvantages mentioned above, that is to say in particular to provide a method and a device for separating gaseous mixtures by permeation, continuous, which minimizes the impact of certain poisons on its performance and offers a good availability rate (multi-year planned shutdown).
• the invention relates to a method for purifying a given gas stream comprising one or more constituents to be recovered, one or more impurities to be removed and one or more poisons for a permeation separation unit, comprising the following steps:
• the given gas flow is brought into contact with one or more liquid solvents suitable and intended to selectively absorb said poisons so as to obtain at least a first flow gaseous depleted in said poisons and a second liquid stream;
• step b) separating said first gaseous stream from step a) in said permeation separation unit, at a given absolute pressure P, into at least a third gaseous stream depleted of impurities and a fourth stream; the separation carried out in step a) being carried out at an absolute pressure of between 50% and 200% of said given absolute pressure P.
• the given gas stream to be purified is of any type that can be purified by selective permeation through one or more membranes. It is essentially gaseous. It may contain drops of liquid and / or solid particles in trace amounts.
• the purification operation essentially consists in removing from this stream one or more compounds which will be called "impurities" so as to obtain a purified stream, that is to say, where the impurity concentration has been lowered below one. predetermined threshold. In particular, it may be to remove the C0 2 from a synthesis gas stream (H 2 / CO), or a hydrocarbon stream constituting the recycle of a catalytic hydrocarbon oxidation process , or a flow of methane.
• the given gas flow is treated in an absorption separation unit intended to remove one or more species harmful to the membrane or membranes implemented in the permeation step b).
• These compounds will be called "poisons".
• compounds such as alcohols (eg methanol, ethanol, etc.), aldehydes (eg formaldehyde, acetaldehyde, acrolein, etc.), ketones (eg acetone, etc.), acids carboxylic acids (eg acetic acid, acrylic acid ...) amines, amides, aromatic compounds (eg benzene, toluene ...) can be considered as "poisons" for polymeric semi-permeable membranes.
• the absorption unit in question is physically distinct from the permeation unit. Between the two units is at least one pipe. There may also be in particular a heat exchanger for adjusting the temperature of the first gas stream before admission into the permeation unit, and a compressor.
• the given gas stream is brought into contact with one or more liquid solvents, for example in a liquid-gas absorption column.
• Their function is to selectively absorb the poison or poisons contained in the given gas stream.
• selective absorption it is meant that these solvents absorb more the poisons in question than the other bodies that constitute the given gas stream.
• concentration of poisons in the given gas stream is gradually lowered by passing these poisons in the solvents.
• the solvent or solvents are gradually loaded into poisons.
• One or more solvents may be used depending on their affinity for one or more of the poisons to be removed.
• the second liquid stream includes solvents and poisons that have been removed from the starting gas stream by absorption.
• a portion of the absorbent compounds may eventually be in the first stream, in a small amount, as drops.
• the absorbing compound is chosen so as to ensure maximum absorption of the poisons at the pressure and temperature conditions of the process step, and not to act as a poison on the membrane or in the rest of the process. .
• some aromatic heavy solvents may be considered poisons for oxidation catalysts.
• the aqueous liquids and preferably the water can be chosen as absorbing compounds because they are not a poison for the membrane or for the catalysts used preferentially.
• the first gas stream where the poison concentration has been reduced, is sent to a selective permeation separation unit by a piping system. It must enter the permeation unit with a given absolute pressure.
• the permeation separation unit implements one or more membranes whose permeability vis-à-vis the species that it is desired to preserve and the impurities that it is desired to eliminate is different.
• membranes examples include, for example, products based on hollow fibers composed of a polymer chosen from: polyimides, cellulose-type polymers, polysulfones, polyamides, polyesters, polyethers, polyether ketones polyetherimides, polyethylenes, polyacetylenes, polyethersulfones, polysiloxanes, polyvinylidene fluorides, polybenzimidazoles, polybenzoxazoles, polyacrylonitriles, polyazoaromatics and copolymers of these polymers.
• a polymer chosen from: polyimides, cellulose-type polymers, polysulfones, polyamides, polyesters, polyethers, polyether ketones polyetherimides, polyethylenes, polyacetylenes, polyethersulfones, polysiloxanes, polyvinylidene fluorides, polybenzimidazoles, polybenzoxazoles, polyacrylonitriles, polyazoaromatics and copolymers of these polymers
• At least two new gaseous streams are thus obtained: a third gaseous stream, depleted of impurities, that is to say purified, i. e. enriched in compounds that it is desired to preserve, and a fourth gaseous stream enriched with impurities.
• Enrichment corresponds to an increase in the volume concentration in the species considered, while depletion corresponds to a decrease in the volume concentration. It is each time with reference to the concentration in the flow to be treated.
• step a) also benefits from a high level of pressure, which increases its efficiency.
• the flow is compressed gas given at an absolute pressure of between one-half and twice that required for the first gas flow at the inlet of the permeation separation unit. It may be necessary to recompress the first gaseous flow from step a) according to the compression level of the gas flow given before step a) and the pressure drops that it undergoes during step a) .
• the invention may comprise one or more of the following characteristics: in step a), said given gas stream and said liquid solvents are circulated in countercurrent manner in means of facilitating the absorption of said poisons by said one or more solvents. These means of facilitating may be in particular trays or packings intended to promote contact between the solvents and the given gas flow.
• the method comprises a step c) where said second liquid flow is expanded to at least one capacity where it separates into at least a fifth liquid stream depleted in said poisons which is recycled in whole or part in said absorption unit and a sixth gas stream. said sixth gas stream is added to said third impurity depleted gas stream obtained in step b).
• the sixth gas stream, rich in poisons, may optionally be combined with the purified stream from step b).
• the absorbent compound (s) used in step a) can be a liquid stream of aqueous or organic solvent.
• the solvent used is preferably water.
• the circulation of the absorbent compounds is preferably countercurrent of the gases to be treated.
• the purification process according to the invention makes it possible to avoid the accumulation in a solid and fixed adsorbent of compounds present in small quantities in the gas to be treated and to reduce the risks of associated inflammation.
• compounds which, in very small quantities, do not represent any risk can accumulate in excess of a critical concentration sufficient to ignite and propagate the inflammation to the treated gas and / or the adsorbent (eg charcoal).
• the adsorbent eg charcoal
• the accumulation of these compounds can lead to their explosion.
• aromatic compounds such as toluene present in a gas to be treated in very small amounts adsorb on activated carbon, the treated gas also containing NOx type compounds.
• the toluene remains adsorbed and can thus accumulate.
• the nitration reaction of toluene is catalyzed by the solid support (here activated carbon).
• the accumulation of nitro derivatives of toluene (powerful explosive) on activated carbon becomes extremely dangerous.
• the absorption compared to the adsorption has a lower investment cost and a much lower sensitivity to contamination, or even zero if water is used as the solvent.
• step c) said second liquid stream from the absorption separation unit, loaded with poisons for the membrane, can be decompressed into a capacity or equivalent means, so as to release the absorbed poisons in the form a gas flow.
• the solvent (s) thus freed from a portion of the poisons can be recycled to the solvent feed of the absorption separation unit. Purge and solvent booster may be necessary to avoid poison accumulation.
• the gas stream rich in poisons can be added to the purified gas stream from step b).
• the solvents used are to be used separately or in groups, several different flash capacities and recycling circuits are used.
• the given gas stream then sees these solvents successively during step a) in as many reactors as necessary.
• the invention also relates to a method implementing at least one petrochemical unit and comprising the following successive steps:
• the purification as described above is ideally applied to a petrochemical process operating at a relatively low pressure, for example less than 10 bar.
• the use of membranes on a stream to be recycled, at a higher pressure than said petrochemical process, is generally intended to purge this stream of certain compounds that it is not desired to recycle in said petrochemical process.
• the liquid effluent of this column charged in poisons for the membrane, can be decompressed at the pressure of recycling of said petrochemical process.
• the gas phase generated by this decompression enriched with harmful compounds for the membrane, can be recycled to the petrochemical process in order to valorize these compounds.
• the method according to the invention has the advantage of not being cyclic and thus greatly simplifying the design and conduct of the pre-treatment process.
• the operation of the high pressure pre-treatment process makes it possible to achieve very low levels of poisons to be removed from the stream sent to the permeation separation unit.
• the nature of the solvent (s) is chosen so that the solubility of the poisons is high. In general, if the poisons are hydrophilic, water will be preferred as the solvent; if the poisons are rather hydrophobic, a hydrophobic solvent will be preferred, such as, for example, ditolyl ether.
• the absorbing compound can be a miscible mixture of different solvents (for example ditolyl ether and dimethylphthalate) allowing the absorption of all the poisons without resorting to a multistage absorption process.
• solvents for example ditolyl ether and dimethylphthalate
• the nature of the solvent will also be chosen so that it is not itself a "poison" for the membrane. Indeed, the solvent will be present in the purified gas sent to the permeation unit in a concentration equal to its vapor pressure under the conditions of temperature and pressure of the absorption unit.
• the invention also relates to a purification plant of a given gas flow comprising:
• an absorption separation unit separate from said permeation separation unit, fluidically connected as input to a source of said given gas stream and one or more liquid solvent sources adapted and adapted to absorb one or more poisons for said permeation separation unit (5) included in said given gas stream, a first outlet of said absorption separation unit being fluidly connected to said unit permeation separation.
• connection means that there is connection by a system of pipes capable of transporting a flow of material.
• This connection system may include valves, intermediate storages, bypasses, heat exchangers, compressors, but not chemical reactors.
• the invention may comprise one or more of the following features: said absorption separation unit comprises at least one liquid-gas absorption column, countercurrent, comprising means for facilitating absorption of said poisons in said liquid solvents.
• one of said liquid solvent sources is a capacity fluidly connected at the input to a second output of said absorption separation unit, this connection comprising expansion means.
• the relaxation means are typically valves.
• said capacitance has at least two outputs, one of which is fluidly connected to an input of said absorption separation unit.
• one of said capacitance outlets is fluidly connected to a given output of said permeation unit.
• said source of said gas stream is a petrochemical unit and said given output of said permeation unit is fluidly connected to an inlet of said petrochemical unit.
• Said petrochemical unit in a nonlimiting manner, is capable and intended to carry out any one of the following methods:
• the petrochemical process 14 is a unit of oxidation of propylene to acrylic acid. It converts a propylene stream 13 in the presence of an oxygen stream (17) into a stream of acrylic acid. During the conversion, a given gas stream 1 is produced. It comprises an impurity, C0 2 , a poison, acrolein, and a mixture of propane and propylene which it is desired to recycle in the petrochemical unit 14.
• the stream 1 is compressed at a pressure of 12 bar absolute and injected into a unit 2 of absorption separation. This consists of a plate column supplied countercurrently by the gas stream 1 and by recycled water 9 and a makeup 12 from a source 18 of water.
• This unit 2 performs step a) of the process at a temperature of 30 ° C and 12 bar abs. During absorption, the water gradually becomes poisonous. At the outlet of the absorption unit 2, a first stream 3 of poison-depleted gas is obtained, as well as a stream 4 of water charged with poison. Stream 3 is injected after heating in a permeation separation unit 5 to
• This comprises a membrane which preferably passes CO 2 and preferably retains propane and propylene.
• the flow 4 of poison-laden water is expanded in a capacity 8 via a valve 4a. This expansion separates the stream 4 into a poison-rich gas stream 10 which is added to the stream 6 purified before recycling in the petrochemical unit 14 and a stream of water 9 less charged with poison which is compressed and sent to the inlet of the tank.
• a purge of liquid 11 prevents the accumulation of poison in the water circuit 9, 4. means 12 can inject water, especially to make the extra.
• An absorption column (2) consisting of 20 trays countercurrently contacts 460 kmol / h of the gas stream (1) with 5 tons / h of a stream of liquid water; the gas stream (3) produced by said absorption column is depleted in poison (here acrolein) and is fed to a polyetherimide type semi-permeable membrane (5); this membrane makes it possible to produce a stream (6) depleted of CO2 which is recycled to the unit (14), and a stream (7) which is purged or used in other units such as ovens.
• the following table shows the flow rates of the main constituents of the main flows in the example.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Environmental & Geological Engineering (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Gas Separation By Absorption (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

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• 2009
  • 2009-11-02 FR FR0957730A patent/FR2951959B1/fr not_active Expired - Fee Related
• 2010
  • 2010-10-27 CN CN2010800493691A patent/CN102648038A/zh active Pending
  • 2010-10-27 RU RU2012122855/05A patent/RU2012122855A/ru not_active Application Discontinuation
  • 2010-10-27 BR BR112012010350A patent/BR112012010350A2/pt not_active IP Right Cessation
  • 2010-10-27 KR KR1020127011134A patent/KR20120102047A/ko not_active Withdrawn
  • 2010-10-27 EP EP10788104A patent/EP2496335A1/fr not_active Withdrawn
  • 2010-10-27 WO PCT/FR2010/052303 patent/WO2011051622A1/fr active Application Filing
  • 2010-10-27 US US13/505,299 patent/US20120210870A1/en not_active Abandoned
  • 2010-10-27 IN IN3072DEN2012 patent/IN2012DN03072A/en unknown

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