METHOD AND SYSTEM FOR REMOVING CARBON DIOXIDE FROM AIR

Abstract

The invention relates to a method for removing and obtaining carbon dioxide from ambient air, comprising the continuous execution of the following steps: a) bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal for the purpose of absorbing the carbon dioxide into the solution, forming the bicarbonate or carbonate of the at least one metal; b) electrodialysis of the resulting solution using a combination of bipolar ion-exchange membranes and ion-exchange membranes that are selective for mono- and multivalent anions to obtain one solution enriched in (bi-)carbonate anions and one solution depleted in (bi-)carbonate anions, wherein the solution depleted in (bi-)carbonate anions is recycled to step a); c) thermal desorption of the carbon dioxide from the solution, obtained in step b), enriched in (bi-)carbonate anions by means of steam stripping in order to obtain a carbon dioxide-steam mixture and a solution depleted in CO.sub.2 which is recycled to step (b), wherein a pH is set there of between 7 and 8.5 or between 8 and 9.5; and d) removing water from the obtained carbon dioxide-steam mixture by cooling to condense the steam, and possibly further drying of the carbon dioxide.

Claims

1. A method for separating and recovering carbon dioxide from ambient air, comprising the continuous execution of the following steps: a) bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution, thus forming the bicarbonate or carbonate of the at least one metal; b) electrodialysis of the resulting solution using a combination of bipolar ion-exchange membranes and ion-exchange membranes that are selective for mono- or multivalent anions to obtain one solution enriched with (hydrogen) carbonate ions and one solution depleted of (hydrogen) carbonate ions, wherein the solution depleted of (hydrogen) carbonate ions is recycled to step a); c) thermal desorption of the carbon dioxide from the solution obtained in step b) that is enriched with (hydrogen) carbonate ions by means of steam stripping in order to obtain a carbon dioxide-steam mixture and a solution depleted of CO.sub.2 that is recycled to step (b), wherein a pH between 7 and 8.5 or between 8 and 9.5 is set; and d) separating water from the obtained carbon dioxide-steam mixture by cooling to condense the steam, and optionally further drying of the carbon dioxide.

2. The method of claim 1, characterized in that, in step a), the water of a natural or artificial lake having a sufficiently high concentration of alkali metal or alkaline earth metal ions, e.g. a flooded gravel pit or open pit lake, is used as said solution of the at least one alkali metal or alkaline earth metal cation, wherein the ion concentration is sufficient to result in a pH of the water of at least 7.5 and is optionally preset by the addition of a base.

3. The method of claim 1, characterized in that, in step a), the aqueous solution of the at least one alkali metal or alkaline earth metal cation is brought into contact with ambient air in a spray washer or spray tower.

4. The method of claim 1, characterized in that, in step b), membranes selective for monovalent anions are used in combination with the bipolar ion exchanger membranes and one solution enriched with hydrogen carbonate ions and one solution depleted thereof are obtained.

5. The method of claim 1, characterized in that steam stripping in step c) is conducted in a packed column, optionally at underpressure.

6. The method of claim to 5, characterized in that the relatively cold solution obtained in step b) and enriched with (hydrogen) carbonate ions is, before steam stripping, subjected to a heat exchange with i) the relatively hot solution that has already been subjected to steam stripping, before it is recycled to step b), in order to heat the former solution and to cool the latter solution; and/or ii) the carbon dioxide/water steam mixture obtained during steam stripping, in order to heat it and to cool the carbon dioxide/water steam mixture to condensate the water steam.

7. The method of claim 1, characterized in that the condensate obtained during cooling of the carbon dioxide/water steam mixture is recycled to step b) and/or recycled to step d) in order to again produce water steam for steam stripping therefrom.

8. The method of claim 1, characterized in that i) waste heat of a power plant or factory is used for producing the water steam in step c) and/or for heating the solution obtained in step b) and enriched with (hydrogen) carbonate ions before steam stripping in step c); and/or ii) DC from renewable energy sources is used for electrodialysis.

9. A facility for continuously executing the method for separating and recovering carbon dioxide from ambient air according to claim 1, comprising the following devices or facility sections in fluid communication with one another via corresponding connecting conduits: a) an absorber or a standing water body for bringing ambient air into contact with an aqueous solution of at least one alkali metal or alkaline earth metal cation for absorbing the carbon dioxide into the solution by forming the hydrogen carbonate or carbonate of the at least one metal; b) an electrodialysis separator comprising a combination of bipolar ion exchanger membranes and ion exchanger membranes selective for mono- or multivalent anions for conducting ion exchange to obtain one solution enriched with (hydrogen) carbonate ions and one depleted thereof, as well as a conduit for recycling the solution depleted of (hydrogen) carbonate ions to a); c) a desorption column for conducting steam stripping of the solution enriched with (hydrogen) carbonate ions to obtain a carbon dioxide/water steam mixture and a solution depleted of CO.sub.2, as well as a conduit for recycling the solution depleted of CO.sub.2 to b) and means for setting a pH value of between 7 and 8.5 or between 8 and 9.5 therein; and d) a condenser for separating water from the obtained carbon dioxide/water steam mixture through condensation, and optionally a drier for the carbon dioxide.

10. The facility of claim 9, characterized in that the absorber is a spray washer.

11. The facility of claim 9, characterized in that a heating device for heating the solution enriched with (hydrogen) carbonate ions before steam stripping is provided between the electrodialysis separator and the desorption column.

12. The facility of claim 9, characterized in that the desorption column is connected to an evaporator for introducing water steam and/or connected to a vacuum pump for producing underpressure therein.

13. The facility of claim 9, characterized in that the heating device is a heat exchanger to subject the relatively cold solution enriched with (hydrogen) carbonate ions in the electrodialysis separator to a heat exchange with i) the relatively hot solution that has already been subjected to steam stripping before recycling it to the electrodialysis separator in order to heat the former solution and to cool the latter solution; and/or ii) the carbon dioxide/water steam mixture obtained during steam stripping, in order to heat it and to cool the carbon dioxide/water steam mixture to condensate the water steam.

14. The facility of claim 9, characterized in that the condenser for recycling the condensate obtained during cooling of the carbon dioxide/water steam mixture is connected i) to the electrodialysis separator via a conduit; and/or ii) to the evaporator via a conduit to again produce water steam from the condensate.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0055] The present invention will now be described in more detail with reference to preferred embodiments that are, of course, only provided for illustrative purposes and are not meant to limit the invention, a calculation example for the energy consumption of the inventive method and the associated facility, as well as with reference to the enclosed drawings, wherein;

[0056] FIG. 1 is a graph showing the pH-dependent equilibrium between carbonic acid, hydrogen carbonate, and carbonate in aqueous solutions.

[0057] FIG. 2 is a flow diagram of a particularly preferred embodiment of the inventive method or the inventive facility.

[0058] FIG. 3 is a schematic representation of a preferred arrangement of anion-selective (“A”) and bipolar (“AK”) membranes in an electrodialysis separator in step b) of the method.

EXAMPLES

[0059] Preferred embodiments for implementing the inventive method or the inventive facility may be designed as schematically shown in FIG. 2. The reference numbers therein have the following meaning, wherein three-digit reference numbers for conduits also refer to the fluid steams transported therein.

Key to FIG. 2:

[0060] 01a absorber/lake [0061] 01b absorber/lake [0062] 01c absorber/lake [0063] 06 heat exchanger diluate-inlet diluate-outlet (“economizer”) [0064] 08 valve—freshwater for diluate [0065] 03 recirculation pump diluate [0066] 04 filtration/conditioning diluate [0067] 05 electrodialysis [0068] 13 recirculation pump concentrate [0069] 14 filtration/conditioning concentrate [0070] 21 heat exchanger concentrate-inlet/concentrate-outlet (“economizer”) [0071] 22 heat exchanger concentrate-outlet/CO.sub.2 wet (“economizer”) [0072] 23 expansion valve [0073] 24 expansion container [0074] 25 sprinkling pump [0075] 26 regeneration column/desorption column [0076] 27 evaporator [0077] 28 valve—freshwater for concentrate [0078] 31 condenser/drier [0079] 32 condensate container [0080] 33 vacuum pump [0081] 101 diluate, heated [0082] 103 diluate under increased pressure [0083] 104 diluate, conditioned/filtered [0084] 105 diluate, recycled for absorption, warm [0085] 106 diluate, recycled for absorption, cold [0086] 107 connection absorber [0087] 108 connection absorber [0088] 109 diluate, cold [0089] 201 concentrate, cold [0090] 203 concentrate with increased pressure [0091] 204 concentrate, conditioned/filtered [0092] 205 concentrated, recycled for desorption, cold [0093] 210 concentrate, heated [0094] 211 concentrate, heated [0095] 212 concentrate, expanded [0096] 213 concentrate after expansion in expansion container [0097] 214 concentrate, sprayed [0098] 215 concentrate supply to evaporator [0099] 216 steam/CO.sub.2 mixture for regeneration [0100] 217 concentrate, regenerated [0101] 231 CO.sub.2, wet, warm [0102] 233 CO.sub.2, wet, cold [0103] 234 CO.sub.2, dried [0104] 235 CO.sub.2, dried, no underpressure [0105] 238 condensate [0106] 239 condensate feedback to concentrate [0107] 218 heat supply to evaporator [0108] 219 heat supply to evaporator [0109] 241-242 freshwater for concentrate [0110] 236-237 cold for cold drying [0111] 110-111 freshwater for diluate

[0112] The inventive method and the inventive facility start, as shown at the top of FIG. 2, with several absorbers 01a-c serially connected via conduits 107 and 108 for absorbing CO.sub.2 from ambient air, which in preferred embodiments are either natural or artificial water bodies such as lakes or quarry ponds, or spray washers or spray towers, or a combination thereof. In the case of several absorbers, the solutions contained therein of at least one alkali metal or alkaline earth metal cation may be set to different pH values by, for example, containing different concentrations of at least one alkali metal or alkaline earth metal cation or by setting the respective pH values in a different manner, e.g. by separate addition of acids or bases.

[0113] In particular, the cations are—due to better solubility of hydroxides and carbonates compared to alkaline earth metal ions—alkali metal cations, more preferably Na.sup.+ or K.sup.+ ions or a mixture thereof. In the calculation example below, K.sup.+ ions are used. Furthermore, the solution may contain additives in the absorbers to increase the sorption capacity of the absorption solution or the sorption rate, such as low alcohols or formaldehyde: however, these are not required for operation of the invention and not preferred due to environmental and cost reasons.

[0114] In the alkaline solution, CO.sub.2 is absorbed from ambient air—either due to spontaneous absorption without external interference or through accelerated absorption, e.g. in a spray tower—depending on the pH value of the solution to form hydrogen carbonate and/or carbonate anions. Preferably, a pH between 7.5 and 8.5 is set when using one or more standing water bodies, at which pH the absorbed CO.sub.2 is primarily present as hydrogen carbonate, which may be seen in the graphic representation of the equilibrium between carbonic acid, hydrogen carbonate and carbonate in FIG. 1. A higher pH value might lead to environmental damages. If, on the other hand, absorption devices such as spray washers or towers are used, a substantially higher pH may be preferably set, e.g. a pH value between 10 and 11, to promote absorption.

[0115] The alkaline solution of the absorbed CO.sub.2 is then subjected to a dialysis step and for this purpose supplied to a electrodialysis separator 05. This may either be done directly or, as shown in FIG. 2, preferably after heating and/or filtering or conditioning the solution. On the one hand, heating increases the mass transfer during the dialysis process, and on the other hand the heat of a liquid stream arising later in the method, but being recycled to a previous step, which would otherwise be lost as waste heat, may be used for this purpose. Consequently, optional heating is preferably conducted by means of a heat exchanger 06, to which the alkaline solution of the absorbed CO.sub.2 is supplied via a conduit 109, and in particular heat exchange is conducted with the solution depleted of (hydrogen) carbonate ions during dialysis, before they are recycled to the absorption step. Optional filtration may largely remove contaminants, as they may occur especially when using standing waters as absorbers, from the solution before dialysis, and conditioning herein refers to the optional addition of pH regulators and/or other additives for promoting the absorption and desorption processes. In preferred embodiments, filtration and conditioning are conducted substantially simultaneously in a filter/conditioner 04 to which the alkaline solution of the absorbed CO.sub.2 is supplied in FIG. 2 via conduit 101, pump 03 and conduit 103.

[0116] From there, the heated and filtered/conditioned solution reaches, via a conduit 104, the electrodialysis separator 05, where one solution depleted of (hydrogen) carbonate ions and one enriched therewith are obtained. Regarding the preferred choice of a pH value of the alkaline solution in the absorption step between 10 and 11 according to the invention—in the case of using spray washers as absorbers—a combination of anion-selective ion exchanger membranes “A” and bipolar membranes “AK” is used in the electrodialysis separator 05 in order to conduct dialysis as shown in FIG. 3. If, on the other hand, for example a pH of the absorption solution of only between 7.5 and 8.5 is set in a standing water as absorber, at which the absorbed CO.sub.2 is primarily present as hydrogen carbonates and only at a very low extent as carbonates, ion exchanger membranes selective only for monovalent anions are preferably used instead of the anion-selective membranes “A” in order to selectively enrich or deplete only hydrogen carbonate on the dilate side or concentrate side, respectively.

[0117] The concentrate thus obtained in the separator 05 is passed to the next step, steam stripping, via a conduit 205, while the diluate depleted of CO.sub.2, which is usually heated during dialysis through the warm solution preferably recycled from steam stripping, is in preferred embodiments recycled via conduit 105 to the heat exchanger 06, where it releases its heat to the alkaline solution of the absorbed CO.sub.2 before it reaches the dialysis step, and subsequently recycled back via conduit 106 to the absorbers 01a to 01c. In order to balance any water loss in this absorber solution cycle, preferably a water supply conduit is provided consisting of conduits 110 and 11l with a valve 08 therebetween.

[0118] Forwarding the solution enriched with (hydrogen) carbonate ions in the electrodialysis separator for steam stripping via conduit 205 may again be done directly or in preferred embodiments of the present invention subjected to various operations before, particularly preferred to a heat exchange, in particular with one or more process steams arising from steam stripping, in order to heat them before they enter the desorption column 26 and thus increase desorption. In addition, the solution being subject to overpressure during pumping may also be subjected to an expansion step for the same purpose.

[0119] A combination of both measures is shown in FIG. 2: via conduit 205, the enriched solution first passes from electrodialysis separator 05 to a heat exchanger 21, where it is subjected to heat exchange with the alkaline solution recycled from steam stripping via conduit 217, and then it is supplied via conduit 210 to a further heat exchanger 22, where it is subjected to heat exchange with a hot gas mixture of water steam and carbon dioxide obtained during steam stripping, which is supplied to heat exchanger 22 via conduit 231. Then, the thus heated solution is supplied via conduits 211 and 212 and valve 23 to an expansion container 24 in order to expand them. Any CO.sub.2 already desorbed during this expansion is led from expansion container 24 via conduit 232 to conduit 231 and thus into the CO.sub.2/H.sub.2O gas mixture supplied to heat exchanger 22. The expanded solution is then, via conduit 213 and 214 and sprinkling pump 25, fed into desorption column 26 in order to subjected to steam stripping there.

[0120] Preferably, an evaporator 27 is connected to the desorption column 26, which evaporator generates the water steam required for steam stripping, which steam is fed into the column via conduit 216. Here, the evaporator is preferably operated with waste heat from a power or incineration plant, as is partly shown in FIG. 2 via conduits 218 and 219. Alternatively or in addition, heat of the hot gas mixture of CO.sub.2 and water steam contained in the desorption column may be fed via a heat exchanger to evaporator 27.

[0121] In the desorption column 26, which preferably is a packed column, as indicated in FIG. 2 by hatching, the preheated solution enriched with (hydrogen) carbonate ions is led as a countercurrent to ascending hot water steam, which leads to a decarboxylation and desorption of the CO.sub.2 dissolved as (hydrogen) carbonate and to the formation of the mentioned hot gas mixture of carbon dioxide and water steam, which exits the column via conduit 231. In addition, the pH in the (hydrogen) carbonate solution may be lowered for supporting desorption, for example by introducing gaseous or aqueous HCI, which is, however, not preferred due to cost and environmental reasons.

[0122] The alkaline solution depleted of CO.sub.2 may now be discarded; preferably, however, it is recycled, either directly—or after previous heat exchange with the solution to be desorbed in heat exchanger 21—to the dialysis step or first again to the desorption column 26, in order to complete desorption, before it is recycled to the electrodialysis separator 05. The latter variation is shown in FIG. 2: the solution subjected to desorption is fed via conduit 215 to evaporator 27, where it is used for producing water steam for steam stripping, wherein CO.sub.2 still dissolved at this time is simultaneously desorbed, so that a hot gaseous mixture of CO.sub.2 and H.sub.2O—even though with a relatively lower content of CO.sub.2 than in the column—is formed already here, which is fed into the desorption column 26 as “water steam” as mentioned above and subjected to another desorption, which herein is called “regeneration”. At the same time, however, part of the solution is continuously withdrawn from the evaporator 27 and via conduit 217 to separator 05, wherein this part of the solution subjected to desorption several times is called “regenerate”.

[0123] On the way back to electrodialysis, the recycled solution 217 is, as mentioned, subjected, in heat exchanger 21, to a heat exchange with the solution 205 from the dialysis step that still has to be subjected to steam stripping, in order to heat the latter before steam stripping. From there, it reaches, via conduit 201 and 203 and pump 13, preferably also, i.e. like the diluate-side cycled solution, a filter/conditioner 14 in order to remove contaminants before dialysis and optionally set the pH value, and from there via conduit 205 the electrodialysis separator 05. Optionally, the water amount of the so circulated solution may be supplemented by a water supply (not shown). Preferably, in the inventive method, however this supplement is added in a further recycled material, namely the water steam that is drained from the column 26 together with the desorbed CO.sub.2 as a gas mixture. In preferred embodiments it is, as mentioned above, fed via conduit 231 to a heat exchanger 22, where it gives part of the heat to the solution that was enriched with (hydrogen) carbonate ions in the dialysis step and still has to be subjected to steam stripping, whereafter it is fed to a cooler 31 in order to condense off the water from the mixture and thus obtain CO.sub.2 largely freed from water. The latter is drawn from the method via conduits 234 and 235 as well as pump 33, wherein—depending on the intended purpose—it may be subjected to further drying.

[0124] The cooler 31 may, for example, be operated with the cold water of a natural flowing water (or also standing water). The condensed water arising and being collected in the condensate container 32 is, according to the present invention, preferably fed back via conduit 239 into the recycled material 201 drawn from the heat exchanger 21 on its way back to dialysis and thus recycled, wherein here the additional water supply is preferably provided via conduits 241 and 232 as well as valve 28 in order to keep the solution volume constant.

[0125] Trough these process steps under circulation of water in two cycles on the dilate or condensate side, respectively, of the electrodialysis separator, the method of the present invention may be executed in a highly efficient manner, which will be clearly shown in the calculation example below. However, it is to be understood that the method described in detail above and the associated facility of the present invention may also be put into practice with numerous variations, as long as they are within the scope defined by the attached claims.

[0126] For example, the electrodialysis separator 05 may, depending on the technical layout, be provided with various conventional side aggregates, e. g. internal recirculation pumps for intensifying the ion transport, and/or anti-fouling systems (e.g. by alternating electrical polarity). Since during longer operation of the facility, membrane defects in the separator may lead to the enrichment of metal ions in one of the cycles, electro-dialysis may additionally be conducted by using additional pumps for periodically or continuously balancing the metal ions in the diluate or in the concentrate. Nevertheless, all embodiments of the inventive method and the inventive facility comprise two liquid cycles.

Calculation Example

[0127] In this example, a model of the inventive method and the inventive facility as shown in FIG. 2 was calculated based on empirical data and with computer assistance in order to be able to estimate the required energy consumption.

[0128] The model is based on the following assumptions: [0129] It is winter and the ambient temperature is 10° C. Since the solubility of gases in liquids increases with decreasing temperatures, the inventive method can absolutely be used at very low temperatures outdoors. [0130] The absorber is a large, artificial basin from which an aqueous (hydrogen) carbonate solution is withdrawn at three places, 01a to 01c. [0131] The alkaline absorption solution is a commercially available 20% caustic potash solution (% by weight), such as those used as electrolyte solutions, having a pH of approximately 10.5. [0132] The pH value is only set in the absorption basin and regulates itself during the further course of the method by the equilibrium setting depending on the CO.sub.2 partial pressure of the ambient air. [0133] The heat required for producing steam is provided in the form of electrical energy. [0134] The desorption takes place at an underpressure of 460 mbara (mbar absolute pressure). [0135] The cooling required for operating the condenser 31 is provided through electrical energy.

[0136] All further assumptions and selected or (automatically) set parameters are shown in Table 1 below.

TABLE-US-00001 TABLE 1 Description Ref. No. Parameter Unit Nominal value Range Comment Atmosphere 01a. . . 01c CO.sub.2 content vol. ppm 450 190 to 1000 invention also practicable temperature ° C. +10 −30 to +40 below freezing Diluate inlet 109 . . . 104 salt content solution % by weight ~20 1 to 40 after concentration HCO.sub.3.sup.− mol/l 0.44 0.04 to 0.9 absorption of concentration CO.sub.3.sup.2− mol/l 1.5 0.15 to 3.0 CO.sub.2 temperature solution at 104 ° C. 17 5 to 40 pH value solution — 10.4 8 to 11.5 Diluate outlet 105. . . 106 concentration HCO.sub.3.sup.− mol/l ~0 0 to 0.1 concentration CO.sub.3.sup.2− mol/l 1.72 0.17 to 5.5 Electrodialysis 05 depletion of HCO.sub.3− in the diluate mol/l 0.22 0.02 to 0.5 for membranes selective depletion of CO.sub.3.sup.2− in the diluate mol/l ~0 ~0 to 0.5 for monovalent anions transition of CO.sub.2 from diluate to Nm.sup.3 CO.sub.2/ m.sup.3 4.9 0.4 to 12 relative to 1 m.sup.3 diluate concentrate stream energy consumption kWh/Nm.sup.3 CO.sub.2 3.5 2.4 to 6.0 Concentrate 205. . . 214 salt content solution % by weight ~20 10 to 40 outlet concentration HCO.sub.3.sup.− mol/l 3.0 1.7 to 6.1 concentration CO.sub.3.sup.2− mol/l 0.21 0.05 to 1.2 relation volume streams — 0.3 0.1 to 1.2 usually <0.4 concentrate/diluate temperature concentrate at 205 ° C. 19 15 to 40 temperature concentrate at 210 ° C. 73 60 to 125 temperature concentrate at 211 ° C. 76 60 to 125 pH value concentrate — 8.5 8 to 9.5 Desorption/ 26, 27 column temperature ° C. 80 70 to 130 regeneration column pressure mbara 470 300 to 1500 produced steam amount kg/Nm.sup.3 CO.sub.2 1.6 1.2 to 3.8 heat requirement kWh/Nm.sup.3 CO.sub.2 1 0.8 to 2.1 Gas mixture 231. . . 233 CO.sub.2 portion in mixture % by volume 34 12 to 59 H.sub.2O/CO.sub.2 Concentrate 201. . . 204 concentration HCO.sub.3.sup.− mol/l 1.74 0.93 to 2.6 inlet concentration CO.sub.3.sup.2− mol/l 0.85 0.35 to 2.1 temperature at 204 ° C. 22 Condenser,  31, 234 gas mixture after cooling gas mixture temperature ° C. 4 2 to 8 H.sub.2O/CO.sub.2 CO.sub.2 portion in mixture % by volume 96 85 to 99 energy consumption cooling kWh/NM.sup.3 CO.sub.2 0.22 0.15 to 0.4 Heat recovery 21, 22 specific heat loss total kWh/Nm.sup.3 CO.sub.2 0.41 0.27 to 0.9 Underpressure 33 pressure suction side mbara 460 300 to 1000 generation pressure pressure side mbara 1100 950 to 1500 energy consumption kWh/Nm.sup.3 CO.sub.2 0.08 0.05 to 0.1 Total energy electrical energy kWh/Nm.sup.3 CO.sub.2 3.8 2.6 to 6.5 requirement heat energy kWh/Nm.sup.3 CO.sub.2 1.41 1.07 to 3.0

[0137] From the table it can be seen that per standard cubic meter CO.sub.2 that is absorbed from the atmosphere and recovered as a 96% pure gas (rest: H.sub.2O) at position 235 in FIG. 2, only relatively low amounts of electrical energy of 3.8 kWh and of heat energy of 1.41 kWh are required.

[0138] In addition, the heat energy required for steam production in evaporator 27 could, as mentioned above, be obtained from waste heat of a power plant (or factory) close to the inventive facility and the energy required for cooling in the condenser 31 could at least partly be provided by using the already relatively cold water of a nearby river or lake, which would further reduce the costs for recovering CO.sub.2.

[0139] The present invention thus provides an extraordinarily efficient and economic method and an associated facility by means of which carbon dioxide can be recovered from air continuously and in comparably high purity.