Method for direct capture of carbon dioxide in ambient air

Abstract

The invention relates to a method for direct capture of carbon dioxide in ambient air (2), in which use is made of an installation situated at an altitude greater than 1000m, and preferably greater than 1500m, and preferably greater than 1900m, above sea level, this installation comprising carbon dioxide adsorption means (3), means (5) for bringing ambient air into contact with these adsorption means (3), means (7, 21) for controlling the pressure and the temperature of this air in contact with these adsorption means (3), means (21) for discharging the adsorbed carbon dioxide, and means (25, 27) for supplying energy to this installation comprising means operating with solar energy.

Description

DESCRIPTION TITLE: Process for direct capture of carbon dioxide from ambient air

[0001] The greenhouse effect is a natural phenomenon by which gases present in the lower part of the atmosphere prevent part of the heat emitted by the earth under the effect of solar radiation from returning to space.

[0002] These gases thus form a sort of cover which causes the warming of the lower layers of the atmosphere, leading to a certain number of changes such as: melting of ice, rising water levels, increase in the frequency and intensity of extreme climatic episodes (high temperatures, heavy precipitation, etc.).

[0003] Today, the vast majority of the scientific community agrees that human activity contributes significantly to the emission of greenhouse gases, and that there is therefore a way, by changing this activity, to reduce its impact on the greenhouse effect.

[0004] More specifically, the Paris Agreement of COP 21 ("Conference of Parties") set the maximum increase in global warming at 1.5°C-2°C by the year 2100.

[0005] Among the gases that contribute significantly to the greenhouse effect, carbon dioxide, which is found in ambient air at a concentration of around 400 ppm (parts per million), holds a very important place.

[0006] A significant portion of this carbon dioxide comes from human activity, particularly due to the combustion of petroleum products for energy production.

[0007] To reduce the concentration of carbon dioxide in the air, two main areas of progress are being implemented.

[0008] On the one hand, we are seeking to move towards a low-carbon economy, i.e. one with low emissions, particularly in carbon dioxide: this is the current logic of exploring and using alternative energy sources, and in particular renewable energies (wind, photovoltaic, etc.).

[0009] On the other hand, we are trying to recover the carbon dioxide present in the ambient air, so as to store it ("sequester") or use it in chemical reactions allowing the manufacture of useful products.

[0010] Among the processes for recovering carbon dioxide from ambient air, we know of so-called "direct air capture" (DAC) processes, which consist of passing the air through filters coated with substances allowing the adsorption or absorption of carbon dioxide, which is then recovered for storage or use.

[0011] The present invention aims in particular to provide an installation allowing the direct capture of carbon dioxide from the air by adsorption which has an overall energy balance significantly higher than existing installations.

[0012] This object of the invention is achieved in particular with a method for the direct capture of carbon dioxide in the ambient air, in which an installation located at an altitude greater than 1000m, and preferably greater than 1500m, and preferably greater than 1900m above sea level, is used, this installation comprising means for adsorbing carbon dioxide, means for bringing ambient air into contact with these adsorption means, means for controlling the pressure and temperature of this air in contact with these adsorption means, means for evacuating the adsorbed carbon dioxide, and means for supplying energy to this installation comprising means operating on solar energy.

[0013] Using solar energy to power the facility eliminates any carbon dioxide emissions.

[0014] More specifically, planning for this installation to be located at high altitude allows it to benefit from the combination of the following favorable elements: higher luminosity, notably due to an increased albedo effect at altitude (reflection of light on snow in particular), lower temperature, allowing better performance of photovoltaic panels, lower humidity, allowing increased efficiency of adsorption means, which adsorb fewer water molecules and more carbon dioxide molecules.

[0015] The combination of these favorable factors allows for an average improvement of 40% in the efficiency of solar energy production, and lower energy consumption required to implement carbon dioxide desorption, compared to a situation in which the installation would be located at sea level.

[0016] Thus, in addition to the fact that the process according to the invention does not emit carbon dioxide, it is energy efficient compared to existing solutions on the market - which in particular allows for minimal sizing of the solar energy capture panels.

[0017] According to other optional characteristics of this process, taken alone or in combination:

[0018] - said carbon dioxide adsorption means of the installation comprise amine-coated filters on NFC support: these adsorption means have the advantage of being solid and non-liquid, which makes their handling and implementation very easy; in addition, these adsorption means are active at relatively low temperatures (of the order of 100°C), instead of several hundred °C for liquid solvents - which makes these solid adsorption means particularly suitable for an installation powered by solar energy;

[0019] - the heating means of the adsorption means of the installation include a heat transfer fluid circuit: this heat transfer fluid allows rapid heat exchange with the adsorption means;

[0020] - the heating means of the adsorption means of the installation comprise a heat transfer fluid circuit and heat exchange means interposed between this circuit and said heat transfer fluid circuit: the presence of this intermediate circuit makes it possible to precisely regulate the temperature of the heat transfer fluid;

[0021] - the installation comprises solar water heating means for heating said heat transfer fluid and / or said heat transfer fluid: these solar water heating means constitute a simple and economical solution for heating the heat transfer fluid and / or the heat transfer fluid;

[0022] - the means for removing adsorbed carbon dioxide from the installation comprise at least one vacuum pump: such a pump constitutes a technically simple and economical solution for recovering carbon dioxide; the fact that the installation according to the invention is located at altitude makes it possible to benefit from a lower ambient pressure than at sea level, and thus to consume less energy to create a vacuum in the enclosure where the carbon dioxide adsorption means are located;

[0023] - said means of supplying energy to the installation comprise photovoltaic panels chosen from the group comprising fixed photovoltaic panels and tracking photovoltaic panels: tracking photovoltaic panels allow improved electrical efficiency, thanks to the fact that they permanently have an optimal orientation in relation to the sun;

[0024] - the installation includes means for drying the adsorbed and then evacuated carbon dioxide: these drying means make it possible to separate the carbon dioxide from the water, and thus to recover purified carbon dioxide for storage and / or subsequent use in chemical reactions.

[0025] The present invention also relates to a method according to the above, in which: increasing the pressure and reducing the temperature of the air in contact with the adsorption means to allow the adsorption of carbon dioxide by these means, then reducing the pressure and increasing the temperature of the air in contact with the adsorption means to allow the desorption of carbon dioxide by these means.

[0026] This oscillation of the pressure / temperature couple makes it possible to alternately control the adsorption of carbon dioxide on the adsorption means, and its release by these means.

[0027] Other characteristics and advantages of the invention will emerge on reading the description which follows, with reference to [Fig. 1] which schematically illustrates an embodiment of an installation according to the invention.

[0028] This facility is located on a high altitude site, typically in the mountains at an altitude above 1000 m, preferably above 1500 m, and even more preferably above 1900 m.

[0029] For example, a suitable site in France is the Val-d'Isère resort, located at around 1900 m, and benefiting from strong sunshine.

[0030] The installation according to the invention comprises at least one enclosure 1 inside which are installed filters 3 coated with a material suitable for capturing carbon dioxide from the ambient air by adsorption.

[0031] An example of such a material is the amine ADPES (3-aminopropylmethyldiethoxysilane) used by the company Climeworks Switzerland on NFC (Nano Fibrillated Cellulose) support for the direct capture of carbon dioxide.

[0032] The enclosure 1 comprises grilles through which the ambient air 2 can circulate, being sucked into the enclosure and then forced out of it by a battery of fans 5.

[0033] In doing so, the ambient air comes into contact with the adsorption material located on the filters 3 arranged inside the enclosure 1.

[0034] The temperature inside the enclosure 1 is regulated by a closed circuit 7 of heat transfer fluid such as water, this fluid being stored inside a tank 9 communicating with this circuit 7.

[0035] This heat transfer fluid can be heated through a heat exchanger 11, for example of the tube type, by a heat transfer fluid such as a synthetic oil itself circulating in a closed circuit 13 through a solar water heater 15.

[0036] As is known per se, such a water heater 15 typically comprises reflective panels 17 of parabolic shape converging the solar rays towards a tube 19 in which the heat transfer fluid circulates.

[0037] A vacuum pump 21 allows the filter on which the carbon dioxide has been adsorbed to be periodically purged.

[0038] In reality, the adsorption of carbon dioxide is automatically accompanied by the adsorption of water molecules, so that it is a mixture of carbon dioxide and water which is sucked in by the vacuum pump 21.

[0039] This mixture is directed to a drying unit 23, which separates the carbon dioxide from the water by cooling the water temperature to the dew point of the water, which is approximately 45°C.

[0040] The power supply of all the electrical devices of the installation according to the invention (fans 5, vacuum pump 21, heat transfer fluid circulation and heat transfer pumps, solenoid valve, electronic supervision means, etc.) is preferably carried out exclusively by means of solar energy.

[0041] For this, fixed photovoltaic panels 25 and / or trackers 27 are installed on the installation site, these panels being connected to an integrator electric 29 allowing the electric currents coming from each of them to be added.

[0042] This electrical integrator 29 is itself connected on the one hand to an inverter 31 making it possible to power the aforementioned electrical devices, and on the other hand to electrical accumulators 33, making it possible to store and restore electrical energy as needed.

[0043] The operation and advantages of the installation just described are as follows.

[0044] As has just been mentioned, the photovoltaic panels 25, 27 provide the electrical energy necessary to power the various electrical devices 5, 21... of the invention.

[0045] If necessary, even if it is not the solution preferred by the present invention, electricity from a complementary source can be considered: for example electricity from a hydroelectric power station located near the operating site.

[0046] The heat transfer fluid is brought to a temperature of around 120°C by the solar water heater 15.

[0047] By circulating inside the heat exchanger 11, this heat transfer fluid in turn brings the heat transfer fluid passing through the enclosure 1 via the circuit 7 to a temperature of the order of 100°C.

[0048] Thermal regulation means are provided in the exchanger 11 to precisely regulate the temperature of this heat transfer fluid.

[0049] Under the effect of the circulation of ambient air 2 through the filters 3 arranged inside the enclosure 1, enabled by the fans 5, the carbon dioxide molecules in this air are adsorbed on the amine coating these filters 3.

[0050] By varying the temperature inside enclosure 1 on the one hand and the pressure inside this enclosure 1 on the other hand, the filters 3 can be periodically purged of adsorbed carbon dioxide.

[0051] The regulation of the temperature inside the enclosure 1 is obtained by adjusting the temperature of the heat transfer fluid circulating inside this enclosure 1.

[0052] The regulation of the pressure inside the enclosure 1 is obtained by means of the vacuum pump 21.

[0053] Typically, the release of carbon dioxide by the filters 3 can be obtained by oscillating the temperature / pressure couple inside the enclosure 1 alternately and respectively between high and low values.

[0054] For example, when the temperature inside enclosure 1 is increased to 100 - 110°C and the pressure is reduced to 0.1 - 0.4 bars, the adsorbed carbon dioxide and water vapour are released.

[0055] On the contrary, when the pressure is increased to 1 bar and the temperature is reduced to 20°C, the absorption of carbon dioxide by the filters 3 is allowed.

[0056] This oscillation cycle thus makes it possible to periodically recover a mixture of carbon dioxide and water vapor, sucked downstream of the enclosure 1 by the vacuum pump 21, and sent inside the drying unit 23.

[0057] As explained above, this drying unit 23 makes it possible to separate carbon dioxide from water by operating at a temperature close to the dew point of the water.

[0058] The carbon dioxide recovered downstream of the drying unit 23 can then be stored, for example, in basalt subsoils where it undergoes a natural reaction of transformation into carbonates.

[0059] This carbon dioxide can also be used later for chemical reactions leading to the production of high added value products.

[0060] For example, by reacting with dihydrogen, carbon dioxide can lead to the production of methanol, depending on the reaction: CO2+ 3H2^ CH3OH + H2O

[0061] In another example, carbon dioxide can lead to carbon monoxide by means of the so-called "Reverse water gas shift" reaction: CO2+ H2-> CO + H2O followed by the so-called “Fisher-Tropsch” reaction: nCO + (2n+l)H2-> C n H 2n+2 + nH2O allowing hydrocarbons to be obtained by heterogeneous catalysis.

[0062] As is evident from the above description, the installation according to the invention has numerous advantages.

[0063] Thanks to the fact that this installation is located at altitude, the capture of solar energy by the photovoltaic panels 25, 27 is optimal, in particular due to the albedo effect which is maximal in high mountains.

[0064] Altitude also lowers average temperatures, allowing these photovoltaic panels 25, 27 to operate at higher efficiency.

[0065] The altitude also has the effect of reducing the average pressure of the ambient air 2, which facilitates the suction by the vacuum pump 21 of the mixture of carbon dioxide and water vapor from the enclosure 1, thus leading to a reduction in electricity consumption.

[0066] Altitude also has the effect of reducing the average humidity, which limits the quantity of parasitic water molecules that adsorb on the amine-coated filters 3.

[0067] The optimization: on the one hand of the conditions for producing electrical energy by the photovoltaic panels 25, 27, and of the heat by the solar water heater 15, and on the other hand of the operating conditions of the amine filters 3 (low hygrometry) and the vacuum pump 21 (low pressure), allow the installation according to the invention to be autonomous from an energy point of view, and thus in particular to efficiently capture carbon dioxide from the ambient air without producing it elsewhere.

[0068] Naturally, the invention is described in the foregoing by way of example. It is understood that those skilled in the art are able to carry out different variant embodiments of the invention without departing from the scope of the invention.

[0069] For example, one could consider a simplified installation in which there would be no heat transfer fluid circuit: in this case, the heat transfer fluid circulating inside the enclosure 1 would be directly heated by the solar water heater 15.

Claims

CLAIMS 1. Method for the direct capture of carbon dioxide from ambient air (2), in which an installation located at an altitude greater than 1000m, and preferably greater than 1500m, and preferably greater than 1900m above sea level is used, this installation comprising carbon dioxide adsorption means (3), means (5) for bringing ambient air into contact with these adsorption means (3), means (7, 21) for controlling the pressure and temperature of this air in contact with these adsorption means (3), means (21) for evacuating the adsorbed carbon dioxide, and means (25, 27) for supplying energy to this installation comprising means operating on solar energy.

2. Method according to claim 1, wherein said carbon dioxide adsorption means (3) of the installation comprise amine-coated filters on NFC support.

3. Method according to one of claims 1 or 2, in which the heating means of the adsorption means (3) of the installation comprise a heat transfer fluid circuit (7).

4. Method according to claim 3, in which the heating means of the adsorption means (3) of the installation comprise a heat transfer fluid circuit (13) and heat exchange means (11) interposed between this circuit (13) and said heat transfer fluid circuit (7).

5. Method according to one of claims 3 or 4, in which the installation comprises solar water heating means (15) for heating said heat transfer fluid and / or said heat transfer fluid.

6. Method according to any one of the preceding claims, in which the means for removing the adsorbed carbon dioxide from the installation comprise at least one vacuum pump (21).

7. Method according to any one of the preceding claims, in which the means for supplying energy to the installation comprise panels photovoltaic panels selected from the group comprising fixed photovoltaic panels (25) and tracking photovoltaic panels (27).

8. Method according to any one of the preceding claims, in which the installation comprises means (23) for drying the adsorbed and then evacuated carbon dioxide.

9. Method according to any one of the preceding claims, in which: the pressure is increased and the temperature of the air in contact with the adsorption means (3) is reduced to allow the adsorption of carbon dioxide by these means, then the pressure is reduced and the temperature of the air in contact with the adsorption means (3) is increased to allow the desorption of carbon dioxide by these means.

Images