Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
  • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
  • F25J3/067—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream separation of carbon dioxide
• • 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
  • 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
  • B01D2256/00—Main component in the product gas stream after treatment
  • B01D2256/22—Carbon dioxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/10—Single element gases other than halogens
  • B01D2257/102—Nitrogen
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/30—Sulfur compounds
  • B01D2257/302—Sulfur oxides
• • 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
  • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/80—Water
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2205/00—Processes or apparatus using other separation and/or other processing means
  • F25J2205/40—Processes or apparatus using other separation and/or other processing means using hybrid system, i.e. combining cryogenic and non-cryogenic separation techniques
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2205/00—Processes or apparatus using other separation and/or other processing means
  • F25J2205/60—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/70—Flue or combustion exhaust gas
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
  • F25J2220/80—Separating impurities from carbon dioxide, e.g. H2O or water-soluble contaminants
  • F25J2220/82—Separating low boiling, i.e. more volatile components, e.g. He, H2, CO, Air gases, CH4
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
  • F25J2230/30—Compression of the feed stream
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
  • F25J2230/32—Compression of the product stream
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
  • F25J2230/80—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being carbon dioxide
• • 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 for purifying a flow of feed gas containing CO2 and water, and at least one impurity selected from NOx and SOx, characterized by the integration of a step of purification allowing the preferential elimination of water. It is more precisely a question of developing a complete process for treating CO 2 originating from an oxy-combustion (combustion with pure oxygen or with a gas that is less nitrogen-rich than air) of an industrial nature, allowing it to be condition for transportation and storage for different uses.
• oxy-combustion combustion with pure oxygen or with a gas that is less nitrogen-rich than air
• the combustion gases of fossil fuels and / or biomass or incineration of waste or gases from glass furnaces mainly contain heavy metals such as mercury arsenic, iron, nickel ..., organic pollutants and SOx or NOx compounds.
• EP-A-1332786 discloses a method for purifying a gas stream by removing NOx, SOx, Hg and HgO by oxidation with ozone.
• a problem is to provide an improved method for purifying a CO2-containing gas stream, i.e. a process which ensures a thorough removal of treated pollutants, in particular a thorough elimination of the water.
• the solution of the invention is then a process for purifying a flow of feed gas containing CO2 and at least one impurity selected from water, SOx and NOx, comprising the following successive steps: a) step for pretreating the feed gas stream to at least partially eliminate one of the impurities selected from nitrogen, oxygen, argon, noble gases,
• Adsorption properties of an adsorbent for the preferential removal of a constituent are understood to mean that the adsorbent has an equilibrium adsorption capacity and an adsorption kinetics such that it is possible to remove most of this component of a gas stream and thereby at least partially purify said gas stream in this component.
• NOx and SOx-neutral adsorbent is understood to mean an adsorbent resistant to acids derived from NOx and / or SOx or which does not adsorb NOx and / or SOx.
• adsorbent does not adsorb NOx and SOx, an adsorbent whose pore diameter is such that it does not allow the diffusion of said molecules to the active sites of the adsorbent, that is to say given the characteristics of the molecules in question, having pores of diameter less than 0.4 nm. Since these adsorbents must have adsorption properties vis-à-vis water, the diameter of these pores must also be greater than 0.28 nm.
• the high performance adsorbents consist of an active material having a very large internal porosity, generally greater than 50 m 2 / g and even often greater than 200 m 2 / g.
• the access of the adsorbable molecules to this porosity is possible thanks to the porous structure which must be sufficiently wide to allow the penetration of the molecules.
• the type 3 A zeolite with a pore opening of about 3, practically only accepts the water molecules, which adsorb very strongly.
• Other methods are also possible, such as the chemical deposition of a layer of surface to reduce the opening of the porosity without significantly altering the total volume.
• the determination of the minimum pore size to prevent a molecule from penetrating the porosity depends significantly on its shape.
• the kinetic diameter of the molecule is always the good criterion, because by adsorbing the molecule can be oriented with respect to the pores, for example in length and, in this case, it will pass better than allowed suppose its kinetic diameter, or in width, and it is then the opposite.
• the orientation will depend on the forces responsible for the adsorption, which will depend on the molecular properties such as polarity, polarizability, molecular mass.
• One of the ways of testing the accessibility or not of a molecule to the active sites of an adsorbent is to proceed experimentally.
• a breakthrough curve type test that is easy to implement and interpret can be retained.
• the adsorbent is placed in a column having a length to diameter ratio of between 10 and 15, and a diameter of between 10 and 20 times the largest dimension of the particles if they are not beads, or the average diameter in this case. last case.
• the filling is done in rain, to obtain a maximum and reproducible density.
• inert material therefore non-adsorbent in nature, of the same particle size, such as for example glass, non-porous ceramic, etc.
• inert material is therefore meant a material that does not adsorb the impurity that is being studied, typically non-porous glass beads.
• a mixture consisting of helium containing 1% by volume of the gaseous compound to be studied is passed from bottom to top.
• the temperature is 20 0 C, the total pressure of 1 bar abs.
• the concentration at the outlet of the gaseous compound is measured as a function of time, the so-called breakthrough curve.
• the acid-resistant adsorbents are such that a chemical reaction of the framework is not possible. Framing is the continuous solid matrix of which the material is made. This matrix, in the case of adsorbents, is porous, and it is in these pores, or on their surface, that the adsorption takes place.
• the majority of the zeolites, which are aluminosilicates, and the activated aluminas are not resistant to acids because alumina forms stable salts, for example aluminum nitrate: Al 2 O 3 + 6 HNO 3 - » 2 A1 (NO 3 ) 2 + 3H 2 O
• Silica gel is acid-resistant because silica is a compound itself acid, and it forms silicates, for example sodium: SiO 2 + 2 NaOH -> Na 2 SiO 3 + H 2 O but never salts of silicon.
• the reaction of the silica with hydrogen fluoride does not form a salt itself, because the compound obtained SiF 4 is not ionic as evidenced by its molecular form found in the solid form and its high volatility.
• Some compounds are amphoteric, such as alumina, which can react with acids to form aluminum salts, and with bases to form aluminates. This is not the case for silica and other acid-resistant adsorbents.
• the usable adsorbents are reduced to a few families: the macro and microporous silica gels, possibly containing a few% of alumina; activated carbons, for the non-oxidizing acids under the conditions of use, that is to say preferably non-concentrated and / or at low temperature; decationated zeolites with a high Si / Al ratio such as mordenite, chabazite, clinoptilolite, ferririte, offretite, USY ... These zeolites may have undergone a additional dealumination treatment to bring the Si / Al ratio above 5, preferably above 20 or even above 50; porous glasses; activated clays with a high Si / Al ratio.
• the method according to the invention may have one of the following characteristics:
• the gas flow is in the liquid state and stored, or in the supercritical state and transported and / or stored, or in the gaseous state and transported;
• the NOx and / or SOx-neutral adsorbents are resistant to acids derived from NOx and / or SOx or do not adsorb NOx and / or SOx;
• the NOx and / or SOx-neutral adsorbent bed consists of silica gel, porous glass or zeolite with Si / Al ratio> 5 and / or zeolite 3A;
• the zeolite is chosen from mordenite, chabazite, clinoptilolite, ferrierite, offereite, or USY, these zeolites possibly being partially de-aluminized or not; the zeolite is characterized by a Si / Al ratio> 20, preferentially> 50;
• the second adsorbent bed consists of silica gel and / or zeolite 3A;
• a third adsorbent bed consisting of zeolite 3A;
• three adsorbent beds of increasing effectiveness are used to stop the water, preferably a first bed of porous glass or of silica gel, a second bed of silica gel and a third bed of silica gel; zeolite bed 3 A;
• a first bed of acid-resistant adsorbents derived from NOx and / or SOx is used so as to at least partially eliminate said NOx and / or SOx and at least partially water;
• said first bed of adsorbents resistant to acids derived from NOx and / or SOx is followed by a bed of adsorbents chosen from activated aluminas, impregnated activated aluminas, zeolites A or X, to eliminate at least partially the water ;
• a bed of adsorbents is used downstream of the first adsorbent bed, allowing the preferential elimination of compounds derived from mercury, arsenic, selenium, cadmium, iron and nickel;
• an at least partial elimination step is carried out at a temperature ⁇ 5 ° C of at least one impurity present in the compressed gas stream, selected from nitrogen, oxygen and argon and rare gases using exchangers combined with separators;
• step a) the purification step is carried out between step a) and step b);
• the purification step is carried out after step b);
• the compression step b) comprises successive compression phases and the purification step is carried out between two successive compression phases of said compression step b);
• the purification step is carried out at a pressure ⁇ 20 bar, preferably ⁇ 10 bar, more preferably ⁇ 6 bar and the compression stages downstream of the purification stage are carried out in carbon steel compressors;
• the purification unit used in the purification step is of the TSA or VSA or PSA type or a combination, preferably of the TSA type;
• the porous glass or the silica gel used in the first bed is regenerated by washing with water or steam followed by heating under a gas flush at a temperature of between 80 and 200 0 C, preferably between 100 and 180 0 C;
• the flow of feed gas corresponds to oxy-combustion fumes
• the pretreatment step comprises at least one of the following treatments: catalysis, filtration, washing and desulphurization, with the washing being able to be coupled with a cooling of the feed gas flow.
• an adsorbent for stopping water, its adsorption kinetics and / or its adsorption capacity of water.
• the adsorbent of a second bed is more effective than the adsorbent used in a first bed, if placing in the second part of the adsorber a second adsorbent different from that used in the first part of the adsorber can improve the separation, that is to say if under the same operating conditions, the water breakthrough is later.
• oxygen is understood to mean combustion during which the coal is burned in a fluid that is low in nitrogen, which may range from pure oxygen (> 95%) to a fluid containing the same quantity of oxygen as air (about 21%) obtained by mixing pure oxygen (> 95%) with recycled fumes rich in CO 2 .
• Porous glass is a chemically inert material, particularly resistant to bases and acids, and has good physical characteristics (crushing, attrition).
• SiO 2 is essentially composed of SiO 2 , generally> 90% by weight, preferably> 95%, and may contain B2O3, Na 2 O, Al 2 O 3, ZrO 2 and / or other metal oxides in a minority manner.
• This porous glass has the peculiarity as the name suggests to have a significant internal vacuum, generally greater than 25% by volume, in the form of pores of varying dimensions depending on the products, which allows it to develop internal surfaces several hundred meters per gram.
• VYCOR Brand Porous Glass 7930 from Corning
• the products of this type behave as adsorbents with respect to water in particular and have isotherms similar to those which can be obtained with activated aluminas with generally capillary type condensation in the mesopores from relative humidity of the order of 80%.
• FIG. 1 represents a device making it possible to carry out a method according to the present invention characterized by the location of the purification step at the end of the compression cycle, that is to say between steps (b) and (c) .
• the first step (a) of the present invention aims at treating the fumes using known methods forming part of the state of the art. We often find washing, which uses different liquids (or solvents) such as water, alcohols (methanol for example), amine solutions, basic solutions ... these are the most classic but there are there are many others, either desulphurisation units or filtration units.
• the gas resulting from stage (a) may contain in general: a large majority of CO2 (generally greater than 80%); nitrogen oxides, called NOx, such as NO, NO2, N2O4 ...; sulfur oxides, called SOx, such as SO2, SO3, H2SO4 ...; - water at saturation (at the conditions of temperature and pressure of the flow).
• the treatment processes in the first stage almost all require the contact of the gas with an aqueous solution; oxygen up to a few percent (derived from the excess compared to the stoichiometry necessary to ensure a good efficiency of oxy-combustion); - CO (unburnt combustion); incondensables vis-à-vis CO2: nitrogen, argon, oxygen and rare gases, mainly from the air inlets on the oxy-combustion boiler and the purity of oxygen; compounds derived from heavy metals: AsCl 3 , AsO, AsH 3 , AsN; B (OH) 3 , HBO2, BH 3 ; BaCl 2 , BaO; Be (OH) 2 ; CdO, CdS, CdSO 4 , CdCl 2 ; CoCl 2 , CoO,
• Co 2 [(CO) 4 ] 2 CuCl 2 , CuCl, CuO, CuH; HgO, HgCl 2 , CH 3 HgCl, HgH, HgS, HgSe;
• the volatile organic compounds are preferably chosen from formaldehyde, acetaldehyde, formic acid, acrolein and acetic acid.
• the gas flow is compressed to a sufficient pressure level to be able firstly to separate a part of the undesirable compounds (separators generally located immediately after each compression step). followed by a heat exchange to cool the gas flow to eliminate the condensables that appeared during this cooling: water for example) and on the other hand to bring the gas under the right conditions (temperature and pressure) to prepare removing other impurities in the following steps.
• a heat exchange to cool the gas flow to eliminate the condensables that appeared during this cooling: water for example
• this third step can be optimized if it is carried out at low temperature, that is to say at a temperature ⁇ 5 ° C, preferably at a negative temperature, more preferably between -20 0 C and -60 0 C using exchangers combined with separators in a cold cycle .
• the fourth step (c) then aims to recover a stream of purified gas, enriched in CO2.
• the water present in the gas flow must be stopped until a content such that its presence does not pose a problem of clogging either in the case of a low temperature treatment ⁇ 0 ° C ( case for example of the possible penultimate step), either during transport or storage of CO2.
• This water content may be lower than the ppm but also reach a few tens of ppm depending on the conditions of treatment, storage or transport.
• the NOx and SOx present in the gas to be treated may or may not be acceptable depending on the one hand their content, and secondly the standards for the CO 2 product or processes envisaged for the treatment of CO2.
• the NOx and SOx are acceptable, they can be adsorbed and / or dissolve in the aqueous phase during the purification step and subsequently cause deterioration of the adsorbents.
• This purification step may be placed throughout the second step b) which aims to gradually compress the gases from around atmospheric pressure to the pressure required for the separation of the inerts.
• the choice of the location of the purification step will be a function of a number of criteria such as the investment, the type of materials in the second step b), the nature and the concentration of the impurities.
• the first possibility is to place the purification step at the beginning of step b), that is to say to carry out the purification at low pressure.
• this position has two disadvantages, namely:
• the position of the purification stage upstream of the compressor train constituting the second step b) makes it possible to envisage removing impurities that are detrimental to the rest of the process: ie water, and possibly NOx , volatile organic compounds, compounds based on metals ... also, it may result in a certain advantage as to the nature of the materials to be used in the following, particularly in the compression steps.
• combustion fumes are loaded with CO2 and other acid gases and of course wet.
• the present invention proposes for example to dry the gas at the beginning of compression or at a pressure of about 4 bar and to implement downstream of the carbon steel compressor compressors.
• a low pressure ⁇ 6 bar can lead to advantageously implement radial beds capable of treating large gas flow rates for drying instead of horizontal beds.
• the second possibility is to place the purification step between two compression stages of the second step b).
• This second possibility makes it possible to dispose of the gas at an intermediate pressure between that which is close to the atmospheric (beginning of the second step b) and that which is required in the third step of the process. This necessarily results in a significant reduction in the installed volume and therefore the cost of the unit. This is all the more true that we move the purification step towards the end of the second step. Indeed, water is likely to be the key element in the design of the purification unit implemented in the purification step (in the case of cyclic adsorption for example). On the one hand, all the compression steps upstream of the purification step make it possible to liquefy a good portion of the water contained in the starting gas. On the other hand, the increase in pressure is accompanied by a reduction in the volume installed to purify the gas.
• the third possibility is to place the purification step at the end of the second step b).
• the volume of the purification unit will be minimal but the whole of the second compression step b) will be performed with the flow of unpurified gas.
• the purification is carried out by adsorption. It will be noted that the choice of adsorbents is fundamental since it involves performing a thorough polishing treatment of the gas flow during step b) of the process according to the invention.
• the acids and their derivatives being very polar, will dissolve in the aqueous phase, the water even making it possible to convert the precursors into true acids.
• oxygenated acids the additional presence of oxygen can also lead to the oxidation of the present acids up to their forms of maximum degree of oxidation, which are, in general, the strongest.
• Nitric and sulfuric acids have a sufficiently low vapor pressure to adsorb very efficiently.
• the ideal adsorbent must be able to adsorb all undesirable constituents, especially water to form an aqueous phase, and withstand the oxidizing and acidic conditions encountered. It must also be able to regenerate easily and adsorb little carbon dioxide.
• silica gel can adsorb up to 40% of its weight in water, and withstand very good at acids and oxidants. It can be regenerated at a temperature of between 100 and 180 ° C., preferably between 125 ° C. and 150 ° C.
• the silica gel is produced by polymerization of the Si (OH) 4 monomer obtained by neutralization of a sodium silicate by an acid such as, for example, sulfuric acid, or by hydrolysis of a compound of the kind silicon alkoxide such as Si (EtO) 4 , so as to obtain a liquid aqueous phase called silica sol which then gels. It can also be from a commercial silica sol which is made to gel by modifying the pH or by adding an electrolyte.
• silica gel There are two forms of silica gel, the microporous and the macroporous, which differ in density and pore size; their mass area is between 200 m / g and 850 m / g.
• Silica gel consists of a porous siliceous porous matrix (Si-OH) on the surface of the pores.
• silica gels containing alumina which have the advantage of being resistant (without fracturing) in contact with liquid water.
• Silica gel adsorbs compounds through the hydrogen bonds it forms with them.
• the highly polar OH bond of sulfuric and nitric acids is therefore very favorable for their adsorption fixation.
• the regeneration of the silica gel saturated with acids may be carried out by washing with water or with steam followed by heating under gas flushing at about 150 ° C. The acids thus recovered are in the concentrated state and, therefore, easier to treat.
• the highly acidic and oxidizing medium thus produced in the adsorbent may serve to remove other impurities, such as organic compounds of mercury or arsenic, by mineralizing them.
• the silica gel can be loaded with a compound such as sodium which will fix the acids in the form of fixed ionic salts, according to the following reaction: Na 2 CO 3 + H 2 SO 4 ⁇ Na 2 SO 4 + CO 2 + H 2 O
• porous glasses and certain zeolites, optionally de-aluminated, having an Si / Al ratio greater than 5, preferably greater than 20, and even more preferably greater than 50.
• the different beds used in the purification step will be dimensioned so as to prevent the target species from being transmitted to the next adsorbent. Also, their sizing will depend on the amount of gas flow to be treated and the content of impurities.
• an adsorbent resistant to NOx and SOx may be advantageous to use to eliminate them, possibly together with a portion of the water, to complete the drying with a conventional adsorbent having no particular resistance vis-à-vis NOx and / or SOx, for example impregnated activated aluminas, adsorbent X or A zeolites conventionally used for the industrial drying of CO2.

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  • 2008-07-08 CN CN2008800245711A patent/CN101842143B/zh active Active
  • 2008-07-08 WO PCT/FR2008/051274 patent/WO2009010691A2/fr active Application Filing
  • 2008-07-08 EP EP08826430A patent/EP2178621A2/fr not_active Ceased
  • 2008-07-08 CA CA2693034A patent/CA2693034C/fr active Active
• 2009
  • 2009-12-10 ZA ZA2009/08818A patent/ZA200908818B/en unknown

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