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
  • B01D53/14—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
  • B01D53/1456—Removing acid components
  • B01D53/1475—Removing 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
  • B01D53/14—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
  • B01D53/1493—Selection of liquid materials for use as absorbents
• • 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
  • B01D53/46—Removing components of defined structure
  • B01D53/62—Carbon oxides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/50—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
• • 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

• CO 2 has a multiplicity of industrial applications.
• CO 2 is used for, inter alia, carbonating soft drinks, beers and mineral water and the rapid freezing of foods.
• the requirements imposed by the food industry on the purity of the CO2 to be used are high.
• CO 2 product that meets these requirements is hereinafter referred to as food grade CO 2 .
• CO 2 of (very) high purity is required; such as various analytical and medical applications and use as a coolant. Because of the stringent requirements imposed on food grade and high purity CO 2 , there is a shortage, despite the large quantities that are produced.
• CO2 recovery takes place on a large scale in ammonia processes. By further purifying this CO2 it can be made suitable for use in the food industry. Since there are not always ammonia plants in the vicinity of the numerous areas where there is a demand for CO2, it is not possible to meet the entire demand in this way.
• CO2 Another method that is used to produce CO2 is the controlled combustion of fossil fuels. With these systems a CO2-rich gas must first be generated in order to be able to recover the CO2 from this.
• CO2 can be recovered from gas streams by means of membrane filtration techniques.
• membrane filtration techniques it is not possible with this technology to meet the specifications which apply for food grade and high purity.
• the other disadvantages are high investment costs and operational costs.
• Another option is recovery of CO2 by means of cryogenic separation. With this technique upstream separation of the impurities is necessary in order to obtain high purity.
• US 4 477 419 describes a process for the recovery of CO2 from gas that contains CO2, oxygen and/or sulphur compounds, an aqueous alkanolamine solution in combination with copper as an absorbent.
• the degradation products of the solvent can be removed by an active carbon bed, mechanical filter and an anion exchange resin.
• US 4 537 753 describes a process for the removal of CO2 and H2S from natural gas with an aqueous absorption fluid that contains methyldiethanolamine.
• the solvent is regenerated by flashing.
• the aim of the present invention is therefore to provide a method for the recovery of CO2 from flue gases, wherein the recovered CO2 can be used as food grade or high purity CO2.
• the invention provides a method for the recovery of very pure CO2 from flue gases, which method comprises the following steps: a) absorption of CO2 from the flue gases in a solvent in an absorber, a CO2-depleted gas stream and a CO2-rich solvent stream leaving the absorber; b) desorption of the absorbed CO2 in a desorber, a CO2-rich gas stream and a CO2- depleted solvent stream leaving the desorber; wherein the solvent used is an aqueous solution that contains an alkanolamine and an activator.
• the alkanolamine is chosen from monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, monoisopropanolamine, diisopropanolamine and triisopropanolamine.
• Methyldiethanolamine (CH3N(CH2CH2OH)2), hereinafter designated MDEA, is used in particular.
• MDEA and activator combination is generally designated as aMDEA.
• the alkanolamine concentration in water is 5 to 80 wt.%, preferably 40 to 60 wt.%.
• the activator used can be any activator suitable for such solvents.
• activators are: polyalkylenepolyamines, in particular diethylenetriamine, triethylenetetramine, tetraethylenepentamine and dipropylenetriamine; alkylenediamines and cycloalkylenediamines, in particular hexamethylenediamine, aminoethylethanolamine, dimethylaminopropylamine and diamino-l,2-cyclohexane, heterocyclic aminoalkyl derivatives, in particular piperazine, piperidine, furan, tetrahydrofuran, thiophene and tetrahydrothiophene, aminoethylpiperazine, aminopropyl- piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, aminoethylpiperidine, aminopropylpiperidine, 2-piperidine-ethanol and furfurylamine; alkoxylalkylamines, in particular methoxypropylamine and ethoxypropylamine, and alkyl
• Piperazine is preferably used.
• the activator concentration is 1 to 20 wt.%, preferably 2 - 8 wt.%, in the undiluted mother solution.
• This mother solution which in general will also contain MDEA, is generally diluted 0 to 4 times, preferably 1.5 to 3 times, with water before it is fed to the absorber.
• CO2 of very high purity also referred to in this text as high purity or food grade CO 2
• CO 2 of a quality such that it can be used as such in the food industry.
• Food grade CO must contain at least 99.5 % (V/V) CO 2 .
• the method according to the invention has broad applicability for the recovery of food grade and high purity CO2 from flue gases.
• the homogeneous geographic spread of the locations of, for example, power stations now offers the possibility for producing food grade CO2 from the flue gases close to the outlet in any region where CO2 is sold.
• the construction of installations for the production of CO2 in the vicinity of, for example, the food industry is therefore not necessary.
• the requisite energy costs for absorbing and desorbing CO2 with the solvent used are low.
• the energy costs are consequently appreciably lower than the energy costs which are required when conventional solvents such as potassium carbonate are used.
• the operational costs are lowered by the prevention of accumulation of heat stable salts and other substances in the solvent circuit, by purification of the solvent using active carbon filtration and ion exchange, as will be described below.
• the degradation problems of the solvent are restricted by a good choice of solvent.
• flue gases are understood to be the off-gases from the combustion of carbon-containing substances. Examples of these are the flue gases from power stations or flue gases originating from combined heat and power plants, gas turbines or utility centres.
• Step a) of the method according to the invention takes place in an absorber, a CO2- depleted gas stream and a CO2-rich solvent stream leaving the absorber.
• contact between solvent and flue gas in the absorber takes place in counter-current.
• the absorber is in general a reactive absorber.
• the temperature in the absorber is 10 to 100 °C, preferably
• Step b) takes place in a desorber.
• the CO2 is liberated from the solvent under the influence of heat. Absorbed impurities such as SO2 and NO x are not desorbed.
• a CO2-rich gas stream and a CO2-depleted solvent stream leave the desorber.
• the CO2- depleted solvent stream is returned to the absorber.
• the CO2-rich gas stream that leaves the desorber is preferably cooled, after which some condensed fluid is separated off and returned to the desorber.
• the desorber is a packed column in which the CO2 is removed from the solvent counter-currently.
• the temperature in the desorber is generally 80 to 120 °C, in particular 95 to 110 °C. According to a preferred embodiment of the invention heat is exchanged between the
• the CO2-rich solvent stream that leaves the absorber and the CO2-depleted solvent stream that leaves the desorber and is returned to the absorber An appreciable saving in the quantity of steam and cooling water required can be achieved by this means.
• the filtration step comprises, successively, a first mechanical filter, an active carbon filter and a second mechanical filter.
• the first filter is preferably a cartridge filter that removes particles > approx. 5 ⁇ m. The efficiency is higher than 99 %.
• the second filter is likewise preferably a cartridge filter that removes particles > approx. 10 ⁇ m and has an efficiency higher than 99 %.
• At least a portion of the CO2-depleted solvent stream which has been subjected to the filtration step is subjected to ion exchange before it is returned to the absorber.
• a cationic ion exchange resin is used.
• heat stable salts can be removed with this method.
• These heat stable salts are alkanolamine salts, in particular of MDEA, which cannot be regenerated by means of heat (such as steam stripping). These salts lower the efficiency of the treatment with
• MDEA MDEA.
• the MDEA salts lower the availability of MDEA for absorption of CO2. These salts can also give rise to corrosion in equipment made of carbon steel.
• the residual amount of oxygen in the flue gas is combusted using a carbon-containing gas, such as natural gas, before the flue gas is fed to the absorber.
• a carbon-containing gas such as natural gas
• the present invention also provides an installation for carrying out the abovementioned process, which installation comprises: an absorber, which absorber is provided with a feed for flue gases, a feed for a solvent for CO2, a discharge for a CO2-depleted gas stream, a discharge for a CO2-rich solvent stream and a feed for make-up water; a desorber, provided with a feed for the CO2-rich solvent stream, a discharge for CO2-rich gas stream and a discharge for a CO 2 -depleted solvent stream.
• the installation is provided with a heat exchanger, positioned between absorber and desorber, which heat exchanger is equipped to exchange heat between the CO 2 -depleted solvent stream originating from the desorber and the CO2-rich solvent stream originating from the absorber.
• the installation is provided with a filtration unit to which at least a portion of the CO2-depleted solvent stream originating from the desorber is fed and optionally with an ion exchanger to which at least a portion of the CO2-depleted solvent stream originating from the desorber downstream of the filtration unit is fed.
• the installation can be provided with a combustion installation provided with a feed for oxygen-rich flue gas, a feed for a carbon-containing gas and a discharge for oxygen-depleted flue gas.
• Figure 1 is a process diagram of the method according to the present invention
• Figure 2 is a process diagram of the method according to Example 1;
• Figure 3 is a process diagram of the method according to Example 2.
• Figure 4 is a process diagram of the method according to Example 3.
• the incoming flue gas is, if necessary, cooled in the flue gas water cooler (G) and pumped through the flue gas compressor (I) to the absorber (A).
• a knock-out drum (H) can also be positioned downstream of the cooler (G) in order to separate off mist droplets (that have formed).
• the CO 2 present is absorbed by the circulating solvent in the absorber (A).
• NO x and SO2 are also virtually completely absorbed.
• the two latter acid gases will not be desorbed in the stripper, but will form anions with the solvent. These anions lead to the formation of heat stable salts.
• An outgoing CO 2 -depleted gas stream (3) issues from the absorber (A).
• This gas stream in general has a residual CO2 content of only 0.5 % (V/V). Because this stream contains more water (vapour) than the incoming gas stream, make-up water (2) is metered in.
• the CO2-rich solvent stream leaves the absorber via (4) and is fed via heat exchanger (J) to desorber (B). In the heat exchanger (J) the CO 2 -rich solvent stream (4) is heated by means of CO2-depleted solvent stream (5).
• the absorbed CO2 is stripped from the absorbent in the desorber or stripper (B).
• the requisite energy is supplied to the stripper (B) by means of reboiler (C).
• the gas that leaves the stripper (B) via the top contains some water vapour and solvent.
• These components are removed by cooling the gas stream in a condenser (D) and then separating off the condensed droplets in the distillate drum (E).
• the collected liquid is returned to desorber (B).
• the CO2 gas (7) now obtained is of such quality that it can be used as such as food grade and high purity CO2. By cooling to a lower temperature in the condenser (D) it is also possible to remove all of the water.
• the CO2-depleted bottom stream (8) from the desorber (B) is returned via heat exchanger (J) and cooler (F) to absorber (A).
• degradation products of the solvent and anions formed are removed from the CO2-depleted absorbent stream (5) that leaves the desorber, optionally after heat exchange has taken place in a heat exchanger (J) and the stream has been cooled in cooler (F).
• Filtration unit (K) consists, successively, of a first mechanical filter, an active carbon filter and a second mechanical filter.
• the first mechanical filter removes the components that could contaminate the active carbon filter.
• the active carbon filter binds all organic degradation products.
• the second mechanical filter prevents carbon that has been flushed out from passing into downstream equipment.
• the filtered solvent is returned to the system.
• An ion exchanger (L) is installed to prevent accumulation of heat stable salts.
• a portion of the stream from the filtration step (K) is fed through the ion exchanger.
• the anions, formed from NO x and SO2, present in the flue gas are removed here.
• the regenerated solvent is returned to the absorber, optionally after passing through heat exchanger (J) and cooler (F).
• a small effluent stream (9) is discharged from the ion exchanger (L).
• Example 1 Food grade/high purity CO2 from flue gas from a power station Flue gas from a power station is fed at a rate of 225,147 Nm /hour to an installation according to the invention as shown in Figure 2. The designations in this figure correspond to those in Figure 1.
• the composition of this flue gas is (in % (V/V)):
• the flue gas also contains the following components (in mg/Nm ): Component Concentration
• the temperature and the pressure of the flue gas are, respectively, 100 °C and 1.05 bara.
• the solvent used is methyldiethanolamine in combination with piperazine in water.
• the methyldiethanolamine concentration is 40 wt %.
• Overhead condenser condensate gas (in) 96 1.1 gas (out) 35 1.05 16490
• the pure CO2 gas obtained has the following composition:
• This purity of the CO2 is such that it can be used without any problem in the food industry.
• a gas that contains 99.993 % (V/V) CO2 can be obtained by removing the water from this CO2.
• CO2 gas having the same composition as in Example 1 is produced in the same way from flue gas, except that a process diagram according to Figure 3 is used. This means that, compared with Figure 2, a heat exchanger (J), a filter unit (K) and an ion exchanger (L) are additionally used.
• Overhead condenser condensate gas (in) 96 1.1 gas (out) 35 1.05 16490
• Example 2 corresponds to Example 2, except that pre-combustion of the residual oxygen in the flue gas is carried out with the aid of natural gas in combustion unit (X) (see Figure 4). h order to produce the same quantity of CO2 as in Examples 1 and 2 97961 Nm /h flue gas is required instead of 225147 Nm /h. In addition, 4703 Nm /h natural gas is required for combustion of the residual oxygen in the flue gas. The other streams are comparable to those in Example 2.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Oil, Petroleum & Natural Gas (AREA)
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• Inorganic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Biomedical Technology (AREA)
• Environmental & Geological Engineering (AREA)
• Treating Waste Gases (AREA)
• Gas Separation By Absorption (AREA)

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• 2000
  • 2000-07-27 NL NL1015827A patent/NL1015827C2/nl not_active IP Right Cessation
• 2001
  • 2001-07-27 EP EP01967856A patent/EP1303344A2/de not_active Withdrawn
  • 2001-07-27 WO PCT/NL2001/000580 patent/WO2002009849A2/en not_active Ceased
  • 2001-07-27 AU AU2001288142A patent/AU2001288142A1/en not_active Abandoned

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