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
  • B01D53/02—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
  • B01D53/0407—Constructional details of adsorbing systems
  • B01D53/0431—Beds with radial gas flow
• • 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
• • 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
  • B01D53/26—Drying gases or vapours
  • B01D53/261—Drying gases or vapours by adsorption
• • 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
• • 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
  • 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
  • B01D2257/80—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
  • B01D2259/41—Further details for adsorption processes and devices using plural beds of the same adsorbent in series
• • 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
• • 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 present invention relates to a process for adsorption purification of a flow of feed gas, in particular air, containing water and carbon dioxide using groups of adsorbers installed in series ,.
• This process generally precedes a process of separation by cryogenic distillation.
• the atmospheric air contains compounds to be removed before the introduction of said air into the heat exchangers of the cold box of an air separation unit, in particular the main carbon dioxide (CO 2 ) compounds, and water vapor (H 2 O) as well as so-called secondary impurities such as nitrogen oxides and / or hydrocarbons, for example.
• the main carbon dioxide (CO 2 ) compounds and water vapor (H 2 O) as well as so-called secondary impurities such as nitrogen oxides and / or hydrocarbons, for example.
• N x Oy means nitrogen oxides
• C n H m means hydrocarbons
• a TSA air purification process cycle comprises the following steps: a) purification of the air by adsorption of the impurities at superatmospheric pressure and at ambient temperature, b) depressurization of the adsorber up to the pressure atmospheric, c) regeneration of the adsorbent at atmospheric pressure, especially by the waste gases, typically impure nitrogen from an air separation unit and heated to a temperature usually between 100 and 250 0 C at by means of one or more heat exchangers, d) cooling at ambient temperature of the adsorbent, in particular by continuing to introduce said waste gas from the air separation unit, but not reheated, and e) repressurization of the adsorber with purified air from, for example, another adsorber in the production phase.
• the air pretreatment devices comprise two adsorbers, operating alternately, that is to say that one of the adsorbers is in the production phase, while the other is in the regeneration phase.
• the production phase corresponds to the purification of the gaseous mixture by adsorption of the impurities.
• the regeneration phase corresponds to the desorption of the impurities, retained on the adsorbent during the adsorption step, by heating the adsorbent by the waste gas heated to a temperature between, for example, 100 ° C. and 250 ° C. It includes the stages of depressurization, heating, cooling and repressurization.
• a step of placing the two adsorbers in parallel, of more or less long duration, that is to say from a few seconds to several minutes, is generally added at the beginning or at the end of the regeneration phase.
• TSA air purification processes are described in particular in US-A-3738084 and FR-A-7725845.
• radial adsorbers allow , reliably and repeatedly, an adsorption purification of large amounts of fluid, especially atmospheric air, while maintaining a good distribution of the treated fluid and fluid circulation speeds compatible with the mechanical properties of the adsorbent particles used .
• the operation of a radial adsorber is shown in FIG. 1.
• the fluid to be purified or separated 1 enters the bottom portion of the radial adsorber 10 and passes through the adsorbent mass.
• the adsorber itself 10 consists of a cylindrical shell of vertical axis AA and 2 funds.
• the adsorbent mass is held in place by means of a perforated outer grid 11 and an internally perforated internal grid 12 fixed on the upper bottom and a solid plate 13 in the lower part.
• the gas 1 circulates vertically at the periphery in the outer free zone 14 between the cylindrical shell and the external grid, passes radially through the adsorbent mass 20 and then flows vertically in the internal free zone 15 before leaving the adsorber from above. Regeneration is carried out in the opposite direction.
• adsorbers are generally used in parallel, each comprising two beds: a first bed of activated alumina or of silica gel, on which the adsorbed agent is preferentially adsorbed; water, and a second bed of molecular sieve, on which CO 2 is preferentially adsorbed.
• Each adsorber therefore consists of three grids.
• the use of these 3 grids causes a limitation on the height of the adsorber.
• the diameter of these radial adsorbers can be up to 6 or 7 meters, although it is sometimes impossible to reach such sizes, often for transport reasons.
• At fixed adsorber diameter it is not always possible to increase the height of the adsorber to increase the capacity because of the assembly of these 3 grids. This assembly can be performed horizontally, the grids being successively threaded, concentrically, starting from the internal grid. The end of each grid is successively fixed on a bottom, the other end being released to be able to thread the next grid.
• a flow rate to be treated representing 800,000 Nm 3 / h of air at 6 bar. It is not possible to treat such a flow rate using two three-grid adsorbers. For example, two units each comprising two adsorbers three grids and allowing each to treat half of the flow concerned. It also requires a flow control system to ensure that the flow of air separates well in two between the two units (flowmeters on the air inlet with control valve, and the same thing at the level of regeneration gas), which generates additional pressure drop.
• each of the two units must be equipped with its own operating valves and its own regeneration heater.
• a solution of the invention is a process for purifying a feed gas stream comprising a main compound, water (H 2 O) and carbon dioxide (CO 2 ), as well as so-called secondary impurities.
• the feed gas stream is introduced into at least one radial adsorber 2 grids containing, as sole adsorption bed, a bed of activated alumina or of silica gel, on which the adsorbed is preferentially adsorbed; H 2 O, b) the gas resulting from step a) is introduced into at least one radial adsorber 2 grids containing, as sole adsorption bed, a bed of molecular sieve, on which CO 2 and impurities are preferentially adsorbed; secondary, and c) recovering a gas from step b) enriched in main compound and capable of undergoing cryogenic distillation.
• secondary impurities oxides of nitrogen and hydrocarbons.
• the invention presented here is based in part on the removal of the intermediate gate, involving the use of a single adsorbent per bottle. In the absence of this intermediate gate, we will speak of adsorber "2 grids" or single-bed, thus allowing a much simpler construction, less expensive, allowing an increase in the size of the adsorber and therefore the flow rate of air that it can handle, and solving any problems of regularity of the thickness of the sieve bed.
• the method according to the invention may have one or more of the following characteristics:
• the molecular sieve is an X-type zeolite
• the adsorber used in step b) has a size less than or equal to the size of the adsorber used in step a) in a ratio ranging from 0.4 to 1,
• each adsorber is subjected to a pressure / temperature cycle, the cycle time of the adsorber or adsorbers used in step a) being between 90 and 600 minutes and the cycle time of the adsorber or adsorbers used in step b) being less than or equal to the duration of the cycle implemented in step a) in a ratio of between 0.4 and 1, preferably between 0.5 and 0.8,
• the hourly molar flow rate of the treated feed gas stream is between 100,000 Nm 3 / h and 1,000,000 Nm 3 / h, in step b), the secondary impurities are stopped with a stopping rate of between 30% and 100%, preferably between 60% and 100%;
• step a) two radial adsorbers 2 grids are used, containing as single adsorption bed a bed of activated alumina or of silica gel, and operating alternately (that is to say that the adsorber is in the regeneration phase while the other is in the production phase and vice versa), and / or in step b) two radial adsorbers 2 grids are used, containing as sole adsorption bed a molecular sieve bed, and operating alternately,
• N pairs of radial adsorbers 2 grids are used, containing as a single adsorption bed a bed of activated alumina or of silica gel, the adsorbers of the same pair operating alternately and the N pairs running in parallel with the same pressure cycle, and / or in that in stage b) N 'pairs of radial adsorbers 2 grids are used, containing as a single adsorption bed a bed of sieves molecular, the adsorbers of the same pair operating alternately and the N pairs parallel to the same pressure cycle, with N> 1 and N' ⁇ 1;
• the hourly molar flow rate of the treated feed gas stream is between 100,000 Nm 3 / h and 3,000,000 Nm 3 / h
• the adsorbers used in step a) are regenerated periodically with a regeneration gas heated by means of a first heater and in that the adsorbers used in step b) are regenerated periodically with a gas of regeneration heated by means of a second heater,
• the adsorbers used in steps a) and b) are regenerated periodically with a regeneration gas heated by means of a single heater,
• each adsorber has a diameter greater than 4.5 m and up to 7 meters.
• the pressure of the feed gas stream is preferably between 1 bar and 35 bar absolute.
• the percentage of secondary impurities entering the purification which has been retained in the adsorber during the cycle is defined as the secondary impurity quench rate.
• the secondary impurity quench rate the percentage of secondary impurities entering the purification which has been retained in the adsorber during the cycle.
• the present invention also relates to a plant for purifying a feed gas stream comprising oxygen (O 2 ), water (H 2 O) and carbon dioxide (CO 2 ), said plant comprising at least one radial adsorber containing, as sole adsorption bed, a bed of activated alumina or of silica gel, and at least one radial adsorber containing as sole adsorption bed a bed of molecular sieve, characterized in that the two radial adsorbers are placed in series.
• said installation comprises at least a first pair of radial adsorbers, containing as sole adsorption bed a bed of activated alumina or of silica gel and operating alternately, and at least a second pair of radial adsorbers containing as a single adsorption bed a molecular sieve bed and operating alternately, the first and second pairs of radial adsorbers being placed in series.
• FIG. 2 illustrates a "series" installation according to the invention.
• the adsorbers "A” are adsorbers containing only a bed of activated alumina or silica gel and adsorbers "B” are adsorbers containing only a bed of molecular sieve.
• adsorbers containing a single adsorbent bed are used. Also, each of these radial adsorbers comprises only two grids and not three grids such as radial adsorbers of the prior art used for a similar purification. The height of these adsorbers two grids are then increased.
• the maximum flow rate treated with a unit comprising 2 adsorbers 2 grids is about
• 850,000 Nm / h can be treated with two units, in series, each comprising two adsorbers 2 grids, in other words using four adsorbers. From here, the process according to the invention makes it possible to treat the flow rate under consideration with the same number of adsorbers, while reducing the cost of manufacturing the adsorbers and improving the rate of arrest of secondary impurities.
• the cycle time of a standard 3-grid unit is set by the regeneration time of the adsorber, which is conditioned, for an available regeneration flow, by the thermal inertia of the adsorber, especially by the quantity of water adsorbed on alumina.
• the cycle time of the adsorber containing a bed of activated alumina or silica gel will therefore be close to that of the standard unit containing a bed of alumina and a bed of molecular sieve.
• the cycle time of the adsorber containing a bed of molecular sieve may be reduced when it will correspond essentially to the thermal inertia. Indeed, there is no more water to desorb, but only CO 2 and secondary impurities requiring a very small amount of energy
• the CO 2 stop adsorber may be a water stop adsorber of a smaller size.
• This reduction in the cycle may also be of interest for stopping secondary impurities because the zone of mass transfer of CO 2 will be all the more important, relative to the saturation zone, that the cycle time is short.
• this relative importance of the MTZ with respect to the saturated zone also leads to an unfavorable non-linearity of the CO 2 dimensioning of the bed as a function of the cycle time, in other words a halving of the cycle time will not result in a division by two of the necessary volume of adsorbent due to the adsorption kinetics.
• each adsorber or pair of adsorbers is equipped with its own operating valves and its own regeneration heater. The size of the heater will be different depending on whether the alumina or sieve is regenerated.
• the method according to the invention has the advantage of providing a different cycle time depending on the adsorber in question: the cycle time of an adsorber containing only a molecular sieve will be shorter, which will give an advantage in terms of rate of arrest in secondary impurities.

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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)
• Separation Of Gases By Adsorption (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Separation By Low-Temperature Treatments (AREA)
• Drying Of Gases (AREA)

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• 2008
  • 2008-11-18 FR FR0857819A patent/FR2938451B1/fr active Active
• 2009
  • 2009-11-06 CN CN2009801459854A patent/CN102215937A/zh active Pending
  • 2009-11-06 WO PCT/FR2009/052144 patent/WO2010058112A1/fr active Application Filing
  • 2009-11-06 JP JP2011543795A patent/JP2012509174A/ja active Pending
  • 2009-11-06 CA CA2743951A patent/CA2743951A1/fr not_active Abandoned
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