Method for capturing carbon dioxide from an ambient environment using an organic-inorganic solution

Abstract

The present disclosure relates to a method (100) for capturing CO2 from an ambient environment, the method (100) comprising the steps of providing (110) an organic- inorganic solution having an organic portion and an inorganic portion, wherein the organic portion comprises alcohol and the inorganic portion comprises an alkali. Further, the method comprises the step of introducing air (120) from said ambient environment to react with said organic-inorganic solution for a time-period until a solid is formed, wherein the introduced air has a temperature of -20-60 ˚C. Furthermore, the method comprises the step of post-treating (130) the solid to release CO2 from said solid.

Description

[0001] METHOD FOR CAPTURING CARBON DIOXIDE FROM AN AMBIENT ENVIRONMENT USING AN ORGANIC-INORGANIC SOLUTION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a method for capturing carbon dioxide(CO2) from an ambient environment and a direct air capture apparatus.

[0004] BACKGROUND

[0005] The continuous increase of CO2 concentration in the atmosphere is considered to be one of the greatest challenges that the society faces. The increase of CO2 in the atmosphere is adversely affecting the society for several reasons.

[0006] For example, elevated CO2 concentrations contribute to the greenhouse effect, leading to global warming. Further, pollution of oceans caused by increased CO2 absorption is detrimental to marine ecosystems. Moreover, increased CO2 levels lead to worse air quality which in turn poses a risk to the health of individuals.

[0007] In order to mitigate the increase of CO2 in the atmosphere, methods directed to actively capturing CO2 could be utilized. Accordingly, methods for capturing CC from the atmosphere seem to be necessary to decrease the CO2 concentration in the short, medium and long-term. Such methods can also be referred to as direct air capture (DAC) methods.

[0008] Accordingly, DAC methods are beneficial as they proactively serve to mitigate climate change by active removal of CC from the atmosphere, thereby contributing to reducing the concentration of CO2 in the atmosphere.

[0009] Conventional methods for capturing CO2 from the atmosphere usually bear a considerable energy penalty. In other words, there is a substantial energy cost associated with methods of the present art. Moreover, conventional methods usually demonstrate slow reaction kinetics and are generally too complicated to perform.

[0010] Thus, methods for capturing CO2 of the present art generally fail to fulfil requirements related to efficiency. Specifically, methods of the present art fail to fulfil requirements of energy costs, reaction times and / or convenience. Thus, there is room for methods of the present art to explore the domain to provide a method for capturing CO2 from the ambient environment that is improved in efficiency. Specifically, there is room for such a method that provides reduced energy costs, reaction times and / or convenience compared to the methods of the present art.

[0011] Thus, even though previous solutions may work well in some situations, it would be desirable to provide a method for capturing CO2 from the ambient environment that is improved in efficiency.

[0012] SUMMARY

[0013] It is therefore an object of the present disclosure to alleviate at least some of the mentioned drawbacks by providing an improved method for capturing CO2 that is more efficient compared to the methods of the present art.

[0014] This and other objects, which will become apparent in the following, are achieved by a method and an apparatus as defined in the appended claims.

[0015] The present disclosure relates to a method for capturing CO2 from an ambient environment. The method may also be referred to as a direct air capture method. The method comprises the steps of providing an organic-inorganic solution having an inorganic portion and an organic portion. The organic portion of the organic-inorganic solution comprise an alcohol. The alcohol may have 80-100 v / v%, or 95-100 v / v%. The inorganic portion comprises an alkali, preferably an alkali metal hydroxide. Moreover, the method comprises the step of introducing air from said ambient environment to react with said organic-inorganic solution for a time-period until a solid / solids is formed. The term “solid” may be interchanged with “solid carbonate”. In other words a solid can be formed in said organic-inorganic solution. The solid may be a solid precipitate containing the CO2 in the form of carbonates. Accordingly, at least a part of the organic-inorganic solution may form a solid. Moreover, the introduced air has (e.g. upon reacting with the organic-inorganic solution or entering a receptacle storing the solution) a temperature of -20 to 60 °C (may be referred to as an operating temperature). Furthermore, the method comprises the step of post-treating the solid / solids to release CO2 from said solid, into preferably an isolated environment.

[0016] An advantage of the method is that it is convenient to implement, has low energy costs and a rapid reaction time. Further, as the CO2 reacts to form a solid, it can be conveniently transported to storage / utilization points where it can e.g. be released as a gas again to recover the alkali metal hydroxide.

[0017] The temperature of the organic-inorganic solution may range from -20 to 75 °C preferably -20 to 60 °C. Preferably, the organic-inorganic solution has room temperature (i.e. about 15 to 25 °C, or 14 to 27 °C) to optimize energy costs. The timeperiod may be varied within the context of the present disclosure. In some aspects, the solution and the introduced air have the same temperature, e.g. ambient temperature. The introduced air may be thermally unregulated ambient air, in other aspects, the introduced air may be thermally regulated (e.g. altered in temperature) before / upon being introduced.

[0018] The organic-inorganic solution may be a solution free from water. In other words, it may be a water-free solution. In some aspects, the organic-inorganic solution may comprise less than 20%, preferably less than 10%, more preferably less than 5% water , less than 4% water, or most preferably less than 1 % of water.

[0019] The step of introducing air may be performed by introducing air with a (pre-determined) flow rate, the flow rate being based on a volumetric ratio of air to said organic-inorganic solution and is equivalent about 10-60 Litres of air per minute per Litre of organic- inorganic solution ((Lair / min) / LSoiution), preferably about 50 (Lair / min) / LSoiution. The step of introducing air may be performed naturally, and / or by utilizing an air circulating device (such as a fan). The introduced air may have room temperature.

[0020] Also, the step of post treating may be performed at room temperature. Accordingly, the method may (in all steps) be performed fully in room temperature and / or ambient pressure (approximately 1 bar) to optimize energy costs. Thereby, no heating and / or cooling procedures may be needed. The method may further comprise the step of, prior to post-treating, performing a step of separating to separate alcohol from the organic-inorganic solution containing said solid. The step of separating may be performed by utilizing, for example, membrane filtration, centrifugation, or any combination thereof. Thereby, the step of separating may comprise filtering the solution containing the solid / solids through said separation method to enable said solid / solids to be separated from the solution. The step of separating may be performed at room temperature. The step of separating may be performed after that said solid is formed. Accordingly, after said step of separating, a solid carbonate may be obtained. The separated alcohol, and any unreacted alkali, are suitable for re-use during an iteration of the method.

[0021] The organic-inorganic solution may comprise of a concentration greater than 20 grams of alkali per litre of said alcohol. Preferably, greater than 30 grams of alkali per litre of said alcohol. More preferably, greater than 40 grams of alkali per litre of said alcohol. More preferably greater than 50 grams of alkali per litre of said alcohol. Most preferably greater than 60 grams of alkali per litre of said alcohol. An advantage of such a range is that it provides an optimum capture capacity (grams of CO2 captured per Litre of solution).

[0022] The step of post-treating may comprise adding at least one of water and acids to said solid. The acids may be one or more weak acids. The acids may be for example citric acid, hydrochloric acid or any other suitable acid.

[0023] Advantageously, the CO2 can conveniently be released from said solid. The CO2 may then be in a gaseous state. This enables the solid to be transported to a defined location / facility away from said ambient environment, as a solid, prior to the release of said CO2 from said solid in a gaseous state. Accordingly, the CO2 may be released isolated from said ambient environment in which it was captured. By adding at least one of water and acids, the inorganic portion of the solution is separated / obtained, suitable for re-use during an iteration of the method.

[0024] Accordingly, the method may further comprise the step of, prior to the step of posttreating said solid, transporting the solid to a location, such as a storage point / facility / chamber or a utilization point / facility / chamber (away from said ambient environment in which it was captured). Hence, the method may capture the CO2 from the ambient environment in a solid form, transport it to a storage point and release said CO2 at said storage point in a gaseous state.

[0025] The ambient environment may comprise 10-50 000 parts per million (ppm), or 1 -50 000 parts per million (ppm), preferably 100-50 000 ppm, most preferably 300-800 ppm CO2. Accordingly, the method may comprise to introduce air having 300-800 ppm of CO2. Advantageously, the method performed by introducing air with concentration of 1- 50 000 ppm allows for a capture yield of 80-100% of introduced CO2. The method may further comprise the step of, during the step of introducing air, performing a bubbling operation to introduce bubbles into said organic-inorganic solution.

[0026] Advantageously, the organic-inorganic solution may be stirred to enhance the mixing between the solution and air. This increases the absorption rate of the CO2. The bubbling and stirring operation may allow for an absorption of CO2, to be substantially 100% of the alkali in the solution.

[0027] The bubbles may be produced by a nozzle / nozzles immersed in the solution, the size and number of the bubbles, and the velocity at which they are introduced may be pre- determined / designed. E.g. this may be stored in a memory unit connected to control circuitry for use in the method.

[0028] The organic-inorganic solution may be an ethanol-sodium hydroxide solution, i.e. containing ethanol and sodium hydroxide which are widely available and relatively cheap chemicals which allows the method to capture CO2 cost-efficiently. Specifically, the inorganic portion may comprise at least one of sodium hydroxide and potassium hydroxide. The organic portion may comprise at least one of ethanol, methanol or any other suitable alcohol.

[0029] The method may further comprise the step of depositing the released CO2, for example by injection underground, into geological formations (such as depleted oil fields) and / or other permanent storage facilities. Prior to this, the released CO2 may be compressed. The CO2 may additionally or alternatively be utilized in commercial applications.

[0030] The method steps of providing, introducing and post-treating may be performed iteratively according to a closed-loop. Accordingly, in some aspects herein, the method may comprise the steps of:

[0031] I. providing an organic-inorganic solution having an inorganic portion and an organic portion;

[0032] II. introducing air from said ambient environment to react with said organic- inorganic solution for a time-period until a solid is formed in said organic- inorganic solution, wherein the organic-inorganic solution has a temperature of (preferably 20 to 60) up to 75 degrees Celsius°C; III. separating said solid portion from said organic-inorganic solution, and obtaining said organic portion and unreacted inorganic portion of said solution;

[0033] IV. post-treating the solid to release CO2 and obtain said inorganic portion from said solid; re-iterate steps l-IV at least one time, wherein for each subsequent iteration, said organic-inorganic solution is provided by utilizing at least a part of said separated organic portion and at least a part of said obtained inorganic portion of a former / prior / previous iteration.

[0034] The present disclosure also relates to a direct air capture system comprising:

[0035] - a receptacle storing an organic-inorganic solution having an inorganic portion and an organic portion;

[0036] - an air inlet opening arranged to receive air from said ambient environment to react with said organic-inorganic solution to allow a solid to be formed;

[0037] - a post-treatment means arranged to post-treat the solid to release CO2 therefrom, preferably isolated from an ambient environment.

[0038] The system may be operable to perform the method according to any aspect of the present disclosure. The receptacle may be a sealed receptacle.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] These and other features and advantages of the present disclosure will now be further clarified and described in more detail, with reference to the appended drawings;

[0041] Figure 1 illustrates a method in the form of a flowchart in accordance with some aspects of the present disclosure;

[0042] Figure 2 illustrates a method in the form of a flowchart in accordance with some aspects of the present disclosure;

[0043] Figure 3 illustrates a graph representative of CO2 absorption efficiencies; and Figure 4 illustrates a direct air capture apparatus in accordance with some aspects of the present disclosure.

[0044] DETAILED DESCRIPTION

[0045] In the following detailed description, some embodiments of the present disclosure will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present disclosure, it will be apparent to one skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present disclosure.

[0046] It is also to be understood that the terminology used herein is for purpose of describing particular aspects only, and is not intended to be limiting. It should be noted that, as used in the specification and the appended claim, the articles "a", "an", "the", and "said" are intended to mean that there are one or more of the elements unless the context clearly dictates otherwise. Thus, for example, reference to "a unit" or "the unit" may refer to more than one unit in some contexts, and the like. Furthermore, the words "comprising", "including", "containing" do not exclude other elements or steps. It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps, or components. It does not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. The term “and / or” is to be interpreted as meaning “both” as well and each as an alternative. More specifically, the wording “one or more” of a set of elements (as in “one or more of A, B and C” or “at least one of A, B and C”) is to be interpreted as either a conjunctive or disjunctive logic. Put differently, it may refer either to all elements, one element or combination of two or more elements of a set of elements. For example, the wording “A, B and C” may be interpreted as A or B or C, A and B and C, A and B, B and C, or A and C. It will also be understood that, although the term first, second, etc. may be used herein to describe various elements or features, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the embodiments. The first element and the second element are both elements, but they are not the same element.

[0047] The phrase “method for capturing CO2” may refer to both the capturing and subsequent treatment of CO2 (i.e. the subsequent release thereof).

[0048] Figure 1 illustrates a method 100 for capturing CO2 from an ambient environment in the form of a schematic flowchart. Figure 1 illustrates that the method 100 comprises the step of providing 110 an organic-inorganic solution / mixture having an inorganic portion and an organic portion, wherein the organic portion comprises alcohol and the inorganic portion comprises an alkali. Further, the method 100 comprises the step of introducing air 120 (comprising e.g. N2, O2, Ar, CO2) from said ambient environment to react with said organic-inorganic solution for a time-period until a solid is formed, wherein the organic-inorganic solution has a temperature of up to 75 °C. The method 100 further comprise post-treating 130 the solid to release CO2 from said solid. Figure 1 further illustrates that the method 100 may comprise the step of depositing 140 the released CO2.

[0049] Figure 2 illustrates the method 100 in accordance with some aspects of the present disclosure in the form of a flowchart. In the following, the example method 100 as disclosed in Figure 2 will be explained. Firstly, air is introduced 120 into a liquid solution comprising alcohol and alkali. As apparent by the present disclosure the solution may be any organic-inorganic solution and is not limited by the disclosure of Figure 2.

[0050] Further, as the air is introduced into the solution CO2 is absorbed into the solution such that clean air is obtained s1 . Accordingly, in the example method 100 of Figure 1 , once the solution has reached its CO2 absorption capacity, which may be pre-determined by e.g. a pre-determined look-up table (LUT), a calculation model, or by letting the air react with the solution for a pre-chosen time-period value (e.g. 12-60 hours or more), a separation step 125 may be performed. Thus, once CO2 is absorbed to a specific extent and a carbonate compound (solid) is formed in said solution, said separation step 125 may be performed. The separation step 125 may in some aspects herein employ / utilize a selective permeable membrane dimensioned to allow the passage of ethanol / alcohol while retaining the carbonate compound (solid). The carbonate- enriched solution is filtered through a membrane that acts as a semi-permeable barrier. As the solution comes into contact with the membrane, ethanol molecules pass through it, driven by a concentration gradient, and are effectively separated from the solids. The ethanol, once it permeates the membrane, is then captured in a pure form on an opposite side. The solids which are now devoid of ethanol, but contain the carbonate compound / compounds, proceed to the next phase s3.

[0051] Accordingly, the alcohol may be re-used in a subsequent iteration of the method 100 such that for a subsequent iteration, said solution is provided by utilizing said separated alcohol of a former / prior iteration.

[0052] Moreover, after the solid carbonate is obtained, a step of post-treating 130 may be performed in which water and acid is added to the solid carbonate to allow the CO2 to be transformed into a gaseous state in which it can be stored or utilized. Hence, prior to post-treating, the solid carbonates may be transferred to a safe location so that they can be utilized / stored in a manner that does not again release it into the ambient environment.

[0053] Accordingly, by adding water and acid the alkali solution may be recovered and as indicated by arrow s5, reused in said subsequent iteration of the method 100. The amount of water and acid may be arbitrarily chosen, in some aspects, the solid is immersed in a water and acidic solution.

[0054] Figure 3 illustrates a bar graph that represents carbon capture efficiencies of different ratios in the concentration of the solution (i.e. ratio of organic and inorganic portions). In Figure 3, the area a1 within the dashed lines corresponds to the range of CO2 concentration in the airflow. The bars in black show the results when ethanol was refilled once during the experiment to compensate for its evaporation loss. For 10 and 20 g / L the evaporation of ethanol was faster, and the ethanol was gone after 8 hours. The diagonally striped bar corresponds to the CO2 absorption when ethanol was refilled more than once. In large scale, the alcohol will be replenished by reflux after condensation of the evaporated solvent. As illustrated in Figure 3, the range of 10-50 g of alkali per litre of said alcohol demonstrates a CO2 removal of 88.8-97.9% of the CO2 contained in the air inlet flow. Thus, optimal capture capacity may be achieved at the entire 10-50 g of alkali per litre of said alcohol range, and potentially at even greater alkali concentrations.

[0055] Figure 3 is based on a testing of the method according to some aspects herein in which operating temperature during the experiments was ambient (~ 25 °C). To study the performance of the process at different atmospheric temperatures which could occur in cold and warm environments, experiments were conducted also at -20 °C and 45 °C. All experiments were conducted by bubbling air through a stirred reactor with the organic-inorganic solution for 8 hours at a ratio of 20 (Lair / min) / LSoiution. The CO2 concentration in air was within the range of 458 to 495 ppm. The results are displayed in Table 1. It can be seen from table 1 that different temperatures in the ambient range may marginally affect the CO2 absorption capacity of the organic-inorganic solution.

[0056] Table 1

[0057] A reactor containing 1 litre of the organic-inorganic solution may continuously operate for a time period of 8-72 hours to partially or fully consume the alkali in reaction. However, feed of CO2 is 7.25 g during 8 hours and 65.32 g during 72 hours. Thus, an organic-inorganic solution of 65 g of alkali per litre or more will be fully reacted after 72 hours of operation.

[0058] The organic-inorganic solution may be prepared by adding the alkali and alcohol in a stirred flask / enclosure until the alkali is fully dissolved, i.e. the step of providing 110 may comprise of preparing the organic-inorganic solution by stirring the solution / mixture. The mixture may be stirred at e.g. 500 rpm for at least 30 minutes, preferably 1 hour. The alkali may be completely dissolved in the alcohol, but it can also be partially dissolved, as long as there is stirring during the CO2 absorption step. Thus, the solid alkali will gradually be dissolved as the alkali in solution is being consumed toward the formation of solid carbonates. Accordingly, after preparing, the mixture may be added in the receptacle to perform the method 100 according to any aspect herein. Advantageously, the preparation allows for the dissolving of the alkali which in turn enables the method 100 to be performed efficiently.

[0059] Figure 4 illustrates schematically a direct air capture system 200 which may be arranged to perform the method 100 in accordance with any aspect herein. The system 200 comprises a receptacle 210 storing an organic-inorganic solution having an inorganic portion and an organic portion. Further, the system 200 comprises at said receptacle 210, an air inlet opening 220 arranged to receive air from said ambient environment to react with said organic-inorganic solution to allow a solid to be formed. Moreover, the system 200 comprises a post-treatment means 230 arranged to posttreat the solid to release CO2 therefrom. The post-treatment means may be located at an environment 250 isolated from the ambient environment. The air may be introduced naturally or e.g. by a fan 240 as illustrated in Figure 4. The receptacle may have a bubble injection nozzle for injecting bubbles into said solution to increase absorption rate of the CO2.

[0060] The air inlet opening may be configured to receive / draw in air with a flow rate of 1-4 L / minutes.

[0061] The system 200 may also comprises a filtering device 270 having a membrane for performing the separation step.

Claims

CLAIMS1 . A method (100) for capturing CO2 from an ambient environment, the method (100) comprises:- providing (110) an organic-inorganic solution having an organic portion and an inorganic portion, wherein the organic portion comprises alcohol and the inorganic portion comprises an alkali;- introducing air (120) from said ambient environment to react with said organic- inorganic solution for a time-period until a solid is formed, wherein the introduced air has a temperature of -20 to 60 °C, preferably 15 to 25 °C; and- post-treating (130) the solid to release CO2 from said solid.

2. The method (100) according to claim 1 , wherein the step of post-treating (130) is performed at room temperature.

3. The method (100) according to claim 1 or 2, wherein the organic-inorganic solution comprises a range of 20-60 grams of alkali per litre of said alcohol, preferably 10-60 grams of alkali per litre of said alcohol.

4. The method (100) according to any one of the preceding claims, wherein the step of post-treating (130) comprises adding at least one of water and acids to said solid.

5. The method (100) according to any one of the preceding claims, wherein the method comprises, during the step of introducing air (120):- performing (121 ) a bubbling operation to introduce bubbles into said organic- inorganic solution.

6. The method (100) according to any one of the preceding claims, wherein the method (100) further comprises the step of, prior to post-treating:- separating (125) the formed solid from the organic-inorganic solution, preferably by filtration through a membrane.

7. The method (100) according to any one of the preceding claims, wherein the method (100) further comprises the steps of:- depositing (140) the released CO2.

8. The method (100) according to any one of the preceding claims, wherein the inorganic portion comprises at least one of sodium hydroxide and potassium hydroxide, wherein the organic portion comprises at least one of ethanol and methanol.

9. The method (100) according to any one of the preceding claims, wherein the introduced air from said ambient environment comprises 300-800 parts per million, ppm, CO2.

10. The method (100) according to any one of the preceding claims, wherein the step of introducing air (120) is performed by introducing air with a flow rate the flow rate being based on a volumetric ratio of air to said organic-inorganic solution and is equivalent to 10-60 Litres of air per minute per Litre of organic- inorganic solution, (Lair / min) / LSoiution), preferably about 50 (Lair / min) / LSoiution.11 .A direct air capture system (200) comprising:- a receptacle (210) storing an organic-inorganic solution having an inorganic portion and an organic portion;- an air inlet opening (220) arranged to receive air from said ambient environment to react with said organic-inorganic solution to allow a solid to be formed;- a post-treatment means (230) arranged to post-treat the solid to release CO2 therefrom.

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