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• • 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
  • B01D53/02—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 adsorption, e.g. preparative gas chromatography
  • B01D53/04—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 adsorption, e.g. preparative gas chromatography with stationary adsorbents
  • B01D53/0462—Temperature swing adsorption
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  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
  • C01B3/50—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification
  • C01B3/56—Separation of hydrogen or hydrogen containing gases from gaseous mixtures, e.g. purification by contacting with solids; Regeneration of used solids
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/102—Carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/104—Alumina
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/10—Inorganic adsorbents
  • B01D2253/106—Silica or silicates
  • B01D2253/108—Zeolites
• • 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
  • B01D2256/16—Hydrogen
• • 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
  • B01D2256/20—Carbon monoxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/40—Nitrogen compounds
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/80—Water
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/40007—Controlling pressure or temperature swing adsorption
  • B01D2259/40009—Controlling pressure or temperature swing adsorption using sensors or gas analysers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/40011—Methods relating to the process cycle in pressure or temperature swing adsorption
  • B01D2259/40043—Purging
  • B01D2259/4005—Nature of purge gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/40083—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption
  • B01D2259/40088—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating
  • B01D2259/4009—Regeneration of adsorbents in processes other than pressure or temperature swing adsorption by heating using hot gas
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/402—Further details for adsorption processes and devices using two beds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/414—Further details for adsorption processes and devices using different types of adsorbents
  • B01D2259/4141—Further details for adsorption processes and devices using different types of adsorbents within a single bed
  • B01D2259/4145—Further details for adsorption processes and devices using different types of adsorbents within a single bed arranged in series
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
  • C01B2203/0415—Purification by absorption in liquids
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
  • C01B2203/042—Purification by adsorption on solids
  • C01B2203/043—Regenerative adsorption process in two or more beds, one for adsorption, the other for regeneration
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/04—Integrated processes for the production of hydrogen or synthesis gas containing a purification step for the hydrogen or the synthesis gas
  • C01B2203/0465—Composition of the impurity
  • C01B2203/0475—Composition of the impurity the impurity being carbon dioxide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
  • C01B2203/14—Details of the flowsheet
  • C01B2203/146—At least two purification steps in series
• • 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
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/151—Reduction of greenhouse gas [GHG] emissions, e.g. CO2

Definitions

• the invention relates to a process for the adsorption purification of a gaseous mixture rich in hydrogen and carbon monoxide, commonly known as H2 / CO mixture or synthesis gas, before its cryogenic treatment in order to produce a rich fraction.
• H2 / CO mixture or synthesis gas commonly known as hydrogen and carbon monoxide
• CO and / or one or more mixtures of H2 / CO of determined content, such as for example a mixture of 50% mole H2 / 50% mole CO. and usually a hydrogen-rich fraction.
• the synthesis gas type mixtures can be obtained in several ways, in particular: by steam or CO2 reforming, by partial oxidation, by mixed processes, such as the ATR (Auto Thermal Reforming) process which is a combination of steam reforming and partial oxidation, from gases, such as methane or ethane, by gasification of coal, or recovered as waste gas downstream of acetylene production units.
• ATR Auto Thermal Reforming
• impurities such as carbon dioxide, water or methanol are often part of the synthesis gas.
• the TSA type method (Swing Adsorption Temperature) is a cyclic process in which each of the adsorbers alternates adsorption stages during which the impurities are retained in the adsorbent and regeneration steps during which a heating phase is used in particular to extract the impurities from the adsorbent.
• the typical operating cycle of this type of unit is described in WO-A-03/049839.
• the units of the TSA-type purification processes are generally dimensioned so as to obtain a synthesis gas of cryogenic quality, ie such that, during the cooling of said synthesis gas in the cold box, the possible deposits of impurities are sufficiently weak to ensure satisfactory operation of said box cold for several years, therefore without clogging or thermal deterioration of the exchange line and without risk to the safety of equipment.
• a CO 2 analyzer ensures the purity of the gas produced. It makes it possible to modify the cycle, for example to shorten the adsorption phase, if detecting premature CO2 breakthroughs linked to a degradation of the performance of the purification unit as mentioned above. The fact remains that despite these precautions, we note after a few years of operation, a degradation of the separation performance of the cold box ensuring the cryogenic separation of the synthesis gas.
• the problem encountered is related to the formation of water in the adsorbent and the recommended solution is to add at the adsorber head a bed of sieve 3A which does not adsorb CO avoids the formation in -situ of the said water.
• This document recommends a regeneration temperature of between 100 ° C. and 400 ° C., which classically corresponds to a skin temperature of the heater of the order of 150 ° C. to 450 ° C.
• Some chemical reactions may also be catalyzed by secondary component deposits on the adsorbent surface.
• Deposits of metals such as iron, nickel, copper, facilitate the reactions mentioned above. For some of them, their origin is due to the decomposition of metal-carbonyls formed upstream of the purification.
• the document WO-A-2006/034765 describes a process for purifying a gas stream rich in carbon monoxide and hydrogen, in which the gas stream is brought into contact with an adsorption layer containing a silica gel. and the adsorption layer is regenerated with a gas whose temperature is between 70 ° C. and 150 ° C., which normally corresponds to a skin temperature of the heater of the order of 150 ° C. to 200/250 ° C.
• the skin temperature of the heater is defined as the temperature at which the regeneration gas is subjected by passing through the heater, that is to say at the temperature of the exchange surface in contact with the gas. It is known, moreover, that for a given thermal power (Q) expressed for example in Kcal / h, the exchange surface to be installed (S) is inversely proportional to the temperature difference ⁇ T between the skin temperature Ti of the heating surface and the temperature of the regeneration gas T 2 From this, it is easily understood that to reduce the necessary exchange surface, and therefore the investment, it is necessary to use a skin temperature Ti as high as possible .
• a chemical or petrochemical plant to heat a fluid at a temperature of 170 0 C, it is conventional to use vapors 250/270 0 C or more.
• the claimed process makes it possible to limit the formation of formic acid and to extend the life of the adsorbents of said purification.
• one of the problems is to provide a cryogenic quality synthesis gas without having to intervene prematurely on the purification units and / or on the cold box by proposing an effective process for purifying a mixture H2 / CO containing at least one impurity, so as to avoid or minimize parasitic reactions.
• the solution of the invention is then a process for purifying or separating a feed gas stream containing at least one impurity, wherein: a) said feed gas stream is brought into contact with a first adsorbent to remove by adsorption at least said impurity, b) recovering said purified or separated gas, c) a regeneration gas containing at least hydrogen (H 2 ) and carbon monoxide (CO) is heated by means of a heater whose skin temperature (Ti) is between 150 ° C. and 200 ° C. C during the heating phase of the gas, and d) periodically regenerating the adsorbent of step a) with the regeneration gas heated in step c) at a regeneration temperature (T 2) such that:
• T 2 Ti - AT with 5 ° C ⁇ T ⁇ 50 0 C
• the method according to the invention may have the following characteristics: the regeneration temperature (T 2 ) is such that the temperature difference ( ⁇ T) is between 5 and 40 ° C., preferably between 5 and 40 ° C. 25 0 C; the skin temperature (Ti) of the heater is equal to or less than 190 ° C. and in that the regeneration temperature (T 2 ) at the inlet of the adsorber is equal to or greater than 150 ° C. the skin temperature Ti is equal to or lower than 185 ° C, preferably equal to or lower than 175 ° C, and in that the regeneration temperature T 2 at the inlet of the adsorber is equal to or greater than 135 ° C, preferably equal to or greater than
• the regeneration gas further contains methane (CH 4 ) and / or nitrogen (N 2 );
• the regeneration heater is a steam heater, the pressure of said vapor being less than 15 bars effective, preferably of the order of 8 to 12 bars; by the term "effective" it is emphasized that this pressure has been measured by taking the earth's atmospheric pressure as zero, the steam used in the regeneration heater is obtained by expansion of a higher pressure steam, - the regeneration heater is a electric heater equipped with a skin temperature control means, the feed gas contains at least hydrogen (H 2 ) and carbon monoxide (CO), the hydrogen content of the feed gas is between about 30 and 75 mol% and that the carbon monoxide content is between about
• At least one impurity of the feed gas stream is carbon dioxide
• At least one impurity of the feed gas stream belongs to the group formed by water and alcohols, in particular methanol;
• the first adsorbent of step a) contains activated alumina and / or silica gel and / or activated charcoal;
• the activated alumina and / or the silica gel and / or the activated carbon are arranged in successive layers in any order or intimately mixed within at least one adsorption bed;
• - Activated carbon is an activated carbon treated to adsorb more specifically secondary impurities selected from nitrogen oxides, sulfur compounds, amines and their decomposition products;
• said feed gas stream is contacted with a second adsorbent comprising zeolite;
• the zeolite is chosen from zeolites of type X, LSX, 4A or 5A;
• the partial pressure of CO in the regeneration gas heated in step c) is less than 2 bars absolute, preferably less than 1 bar absolute, more preferably equal to or less than 0.5 bar absolute
• Figure 1 depicts a purification unit for carrying out the method according to the invention.
• the synthesis gas resulting from an amine wash 10 is directed via the valve 21 - valve 22 closed - to the adsorber 11 consisting of a bed of activated alumina 110 followed by a bed of zeolite 111 in which are respectively retained the water and CO2 contained in the synthesis gas and the gas thus purified is sent to the cold box 60 via the valve 31-valve 32 closed and then is introduced into the cryogenic exchanger principal 70.
• the regeneration gas 30, a hydrogen-rich fraction containing CO and / or CH4, is heated during the heating phase through the steam heater 80 by means of high or medium pressure steam 50.
• the inlet temperature in the adsorber 12 is regulated by means of a temperature probe 13 and a by-pass circuit of the exchanger controlled by the valve 44.
• the valve 43 is closed and the Cold regeneration gas is directed to the adsorber 12 starting to cool the screen bed 121 freed of previously adsorbed CO2 while pushing the residual heat front through the activated alumina bed 120.
• a temperature probe 14 on the circuit regeneration gas evacuation 40 makes it possible to control the smooth running of the heating and cooling steps.
• the hydrogen content remains approximately in the range 30 to 75 mol% and the carbon monoxide in the range 25 to 75 mol%. at 60 mol%.
• the carbon dioxide (CO2) can vary between approximately 5 and 500 molar ppm. If the decarbonation is carried out by washing with amines, the synthesis gas is moreover normally saturated with water. In the case of cryogenic washing with alcohols, it is generally possible to find between 20 and 500 molar ppm of residual CO2. Of the alcohols, methanol is the most common impurity.
• the pressure of the synthesis gas is generally between 10 and 70 bar, many units however operating between 15 and 50 bar.
• the temperature of the feed gas is in the range 5 to 50 ° C., more generally between 15 and 40 ° C. in the case of an amine wash and in the range -70 to -20 ° C. after a washing with alcohols , usually methanol. In the latter case, it is also possible to heat the synthesis gas and to purify at room temperature. The choice is not dictated by purification alone but by global thermal balances around the entire washing, purification, cold box.
• the flow rates of synthesis gas to be purified can range from a few hundred NmVh to several hundred thousand Nm / h. According to the invention, it has been demonstrated that the skin temperature of the heater plays an essential role in the introduction of impurities into the cold box.
• the skin temperature of the regeneration heater must be less than 200 ° C., preferably less than or equal to 175 ° C. so as not to create traces of moisture in the regeneration heater.
• the regeneration gas, and secondly, the regeneration gas must have at the inlet adsorbers a sufficient temperature, greater than 130 0 C, preferably greater than 140 0 C, more preferably of the order of 150 0 C .
• the final regeneration temperature in steps, for example one hour at 80 ° C. at 120 ° C. for one hour before performing the actual regeneration at 150 ° C. or more.
• a steam regeneration heater can be used in the context of the invention.
• a means of limiting the maximum temperature is to use a low-pressure steam, in particular a vapor at a pressure of less than or equal to 15 effective bars, preferably 8 to 12 bars.
• An electric heater can also be used.
• the skin temperature of the heater is limited to a maximum temperature by means of a method defined during the design of the heater. It may be a control of the wall temperature of the heating element through one or more temperature probes for adjusting the electrical power.
• Other means are possible according to the technologies used, the regulation being able to be internal to the equipment (self-regulation) and in this case being part of the specification of the equipment, or external to the equipment, the temperature regulation in question. being treated in the central control system in the same way as the other regulations of the synthesis gas treatment unit.
• the adsorbent will preferably be chosen to regenerate at least during the heating phase, a gas stream containing less than 2 bar of CO partial pressure, preferably less than 1 bar and more preferably less than 0.5 bar.
• the regeneration flow rate expressed as a% of the synthesis gas flow rate, varies greatly depending on the units. It can range from 5% to 50% and more depending on the separation process involved.
• the use of a heater at low temperature leads to preferentially use regeneration rates of at least 10% of the flow rate of the synthesis gas.
• the regeneration temperature of the adsorber less than 150 ° C. leads to the use of regenerable adsorbents at this temperature level. It will therefore be preferable to use water or alcohols, generally methanol, activated alumina and / or silica gel and / or activated charcoal known for their lower affinity with water or alcohols than zeolites. X or A. To stop the CO 2, it will be possible conventionally to use a zeolite or a doped activated alumina.

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