A system for generating electricity and capturing carbon dioxide from air

Abstract

A fuel cell such as an alkaline fuel cell for generating electricity and for extracting carbon dioxide from the air by means of direct air capture. The carbon dioxide is captured in the fuel by a chemical reaction with the electrolyte of the fuel cell. The product produced by the chemical reaction is transported to a reactor for replenishing the amount of electrolyte that reacted with the carbon dioxide.

Description

[0001]A system for generating electricity The present disclosure is directed to a fuel cell which also functions as an apparatus for direct air capture (A direct air capture fuel cell system, DAC-FC in short). An example of a direct air capture fuel cell system is disclosed in WO2011073621, which is incorporated in the present disclosure by reference. In such a system the carbon dioxide in the air is captured, because it reacts with the elec- trolyte. This causes the electrolyte to precipitate reducing the efficiency of the fuel cell. A reactor is connected to the fuel cell for extracting the carbon dioxide in the electrolyte and for producing new / replenished electrolyte. It is an object of the present disclosure to achieve a self-sustaining direct air capture fuel cell system for large scale production of electricity. A first aspect of the present disclosure is: A system for generating electricity and for extracting carbon dioxide from the air, said system comprising: a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel cell for oxidization at said anode, - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, - an outlet for outlet of said product from said fuel cell. A second aspect of the present disclosure is: A method for generating electricity and for extracting carbon dioxide from the air, said method comprising: - providing a fuel cell including a pair of electrodes including an anode and a cathode separated by an electrolyte, a first inlet for introducing a non-carbon binding fuel into said fuel cell for oxidizing said non-carbon binding fuel at said anode, a second inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product. The “fuel cell” part of the system is to be understood as the pair of electrodes and the space between the pair of electrodes where ions flow from one electrode to the other through the electrolyte. At the same time electrons move between the pair of electrodes in an electric circuit including a load. The term “replenished or new electrolyte” is to be understood as electrolyte that has been produced in the chemical reaction in the reactor between a product comprising hydroxide and the product from the fuel cell. In the present context replenishing refers to substituting the electrolyte that has reacted with the CO2 in the air and can therefore not function as electrolyte for the generation of electric current / electric energy. It should be understood as a loop where the “degraded” electrolyte comes out of the fuel cell and into the reactor where it reacts and the degraded electrolyte is “transformed” back to usable electrolyte. The term “pipe” is to be understood as a passageway for conveying. It may include several pipe sections connected to each other and it may have corners or bends. It may also in- clude a pump for example. The hydroxide may be bound to a metal as it is let into the reactor and inside the reactor exist as a hydroxide ion. The non-carbon binding fuel may be hydrogen. In the following specific examples according to aspects of the present disclosure will be explained in more detail with reference to the accompanying drawings. The present dis- closure may, however, be embodied in different forms than depicted below, and should not be construed as limited to any examples set forth herein. Rather, any examples are provided so that the disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. Like elements will, thus, not be described in detail with respect to the description of each figure. Fig.1 illustrates a schematic example of a fuel cell for generating electricity. The fuel cell is part of a first loop (contactor loop), which is shown to the left in the figure. To the right is shown a second loop (calciner loop). The two loops intersect at a reactor. Kalium may circulate in the first loop, and alternate between binding carbon and hydroxide. Calcium may circulate in the second loop, and also alternate between binding carbon and hydroxide. In the reactor, the carbon is transferred from Kalium to Calcium and hydroxide is trans- ferred from calcium to kalium. Fig.2 illustrates the reactions in the two loops. The fuel cell comprises a pair of electrodes including an anode 10 and a cathode 12. The pair of electrodes are separated by a distance and a fuel cell space is thus defined be- tween the pair of electrodes. A pair of wires 11,13 are connected to the electrodes such that an electric current can flow between the pair of electrodes through a load (not shown). The space between the two electrodes is filled with an electrolyte / aqueous alkaline solu- tion. In the specific example the electrolyte is potassium hydroxide KOH. However, in gen- eral, the idea is that carbon dioxide (CO2) from the air is captured in the fuel cell. Thus, an electrolyte reacting with CO2 may be contemplated such as sodium hydroxide (NaOH) or another compound where a hydroxide is present in the electrolyte, i.e. another metal such as an alkali metal may be used for binding the hydroxide. Hydrogen (H2) may be introduced into the fuel cell at a (hydrogen) inlet 14 for oxidizing the hydrogen at the anode, and air comprising oxygen (O2) is introduced at an (oxygen / air) in- let 16 at the cathode, and the fuel cell produces power through a redox reaction between the hydrogen and the oxygen. A problem with these types of fuel cells is that if air is introduced into the fuel cell through the air inlet there is a carbonate precipitation of the electrolyte whereby the fuel cell loses its effect over time - the electrolyte reacts with the CO2 and a compound containing car- bonate ion is produced such as potassium carbonate (K2CO3) and / or potassium bicar- bonate (KHCO3). This is why pure oxygen is normally introduced through the inlet at the cathode, i.e. to avoid the precipitation of the electrolyte. However, for the present disclosure the idea is to let CO2 from the air be captured by the fuel cell such that the fuel cell also functions as an apparatus for direct air capture. The CO2 in the air reacts with the electrolyte and the reaction produces a product which is transported to a reactor 18. In this case the product is a carbonate product characterized by the presence of the carbonate ion such as potassium carbonate K2CO3 and / or potas- sium bicarbonate KHCO3 as mentioned above. The product resulting from the chemical reaction in the electrolyte (electrolyte reaction) in the fuel cell may be in solid state and form small particles or pellets. The product may have a high temperature and a heat exchanger (not shown) may be ar- ranged between the fuel cell and reactor for heating liquid flowing in a district heating sys- tem. Hydroxide is added to a reactor which reacts with the product from the fuel cell and the re- action produces new electrolyte (reactor product). The hydroxide may be added by means of calcium hydroxide (Ca(OH)2), i.e. adding calcium hydroxide to the reactor. The reactor has a reactor inlet 19 for adding the hydroxide. In this case the potassium carbonate prod- uct reacts with the calcium hydroxide and the reaction produces potassium hydroxide. The new electrolyte is added to the fuel cell, i.e. there is a first loop comprising the fuel cell and the reactor. Potassium K circulates in the first loop and transfers from being bound to hydroxide to car- bonate (the chemical reaction in the fuel cell = electrolyte reaction) and back again from being bound to carbonate to hydroxide (the chemical reaction in the reactor). As mentioned above another metal may be used and circulate in the first loop. With re- spect to the metal the loop is considered a closed loop in that metal is not added into the loop except for compensating for any leakage that may occur. A first pipe 20 or conduit is arranged between the fuel cell and the reactor for transporting the product resulting from the electrolyte reaction to the reactor. A second pipe 22 or conduit is arranged between the fuel cell and the reactor for transport- ing the reactor product to the fuel cell. In the reactor a byproduct is produced, specifically a carbonate such as limestone CaCO3 in the present case, i.e. a carbonatation process. With the first loop the precipitation of the electrolyte is compensated by the replenished electrolyte thereby maintaining a balance between the outlet of precipitated electrolyte and the inlet of electrolyte such that the efficiency of the fuel cell is not degraded during opera- tion. The reactor is also part of a second loop in order to maintain a circulation in the first loop, e.g. in order to maintain the first loop. A third pipe is used for transporting the hydroxide to the reactor. A fourth pipe 24 is used for transporting the byproduct to an oven for calcination 26 (Cal- ziner). In the oven the byproduct is heated in a chamber and thereby decomposed into calcium oxide (CaOH) and carbon dioxide. The calcination / decomposition may require high temperatures such as temperatures up to 900 degrees Celsius. It is contemplated that the energy for this may come from the non- carbon binding fuel also used for the fuel cell (and air). In this way only the fuel such as hydrogen needs to be supplied to the plant. Alternatively, it is contemplated that the elec- tricity generated by the fuel cell may be used for heating the oven / chamber. The carbon dioxide may be compressed (in a compressor 28) and stored or used. Calcium (Ca) circulates in the second loop and transfers from being bound to hydroxide to carbonate (the carbonatation process in the reactor) and back again from being bound to carbonate to hydroxide (the decomposition in the oven). Another metal than calcium such as an alkaline earth metal may be used in the second loop as long as it reacts with the product from the reactor, e.g. so that it is more desirable for the Carbon atom to bind to the metal in the second loop than to bind to the metal in the first loop. Between the oven and the reactor is a slaker 30 in which water is mixed with the calcium oxide and produces calcium hydroxide – the third pipe connect the output of the slaker to the reactor. A fifth pipe 32 is used for transporting the calcium oxide from the oven to the slaker. Thus, the carbon atom that originally is bound in the carbon dioxide molecule in the air is transferred from the first loop to the second loop where in the end it may be stored or used. The two loops and an example of the reactions taking place in the two loops are illustrated in fig.2 as previously mentioned. The following description is a summary of the features of the present disclosure ar- ranged according to subject. 1. A system for generating electricity and for extracting carbon dioxide from the air, said system comprising: a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel cell for oxidization at said anode, - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, - an outlet for outlet of said product from said fuel cell. 2. The system according to any of the preceding items, comprising: a first pipe connected to said outlet for transporting said product away from said fuel cell. 3. The system according to any of the preceding items, comprising: a second pipe connected to said third inlet for transporting electrolyte to said fuel cell. 4. The system according to any of the preceding items, comprising: a reactor for reacting with said product for producing replenished electrolyte and a byprod- uct. 5. The system according to any of the preceding items, said reactor having a fourth inlet constituting a reactor inlet for introducing said product into said reactor. 6. The system according to any of the preceding items, said reactor having a second outlet constituting a reactor outlet for outlet of said replen- ished electrolyte from said reactor. 7. The system according to any of the preceding items, said first pipe connected to said reactor inlet for transporting said product from said fuel cell to said reactor. 8. The system according to any of the preceding items, said second pipe connected to said reactor outlet for transporting said replenished electro- lyte from said reactor to said fuel cell. 9. The system according to any of the preceding items, said reactor having a fifth inlet for introducing hydroxide to said reactor. 10. The system according to any of the preceding items, said reactor having a third outlet constituting a byproduct outlet for outlet of a carbonate from said reactor. 11. The system according to any of the preceding items, comprising: a first loop for circulating a first metal for binding hydroxide in said electrolyte from said fuel cell through said reactor and back to said fuel cell. 12. The system according to any of the preceding items, said first metal being an alkali metal such as potassium. 13. The system according to any of the preceding items, comprising: an oven for heating said byproduct. 14. The system according to any of the preceding items, comprising: a second loop for circulating a second metal for binding carbon from said reactor to said oven and back to said reactor. 15. The system according to any of the preceding items, said second metal being an alkali earth metal such as calcium. 16. The system according to any of the preceding items, comprising: a third pipe for transporting said byproduct from said reactor to said oven. 17. The system according to any of the preceding items, comprising: a fourth pipe for transporting Calcium oxide from said oven to said reactor. 18. The system according to any of the preceding items, comprising: comprising a sixth inlet between said oven and said reactor for inletting a liquid for dissolv- ing said Calcium oxide into an aqueous solution. 19. The system according to any of the preceding items, said oven comprising a chamber, and a seventh inlet for introducing said non-carbon bind- ing fuel into said oven for heating said chamber. 20. The system according to any of the preceding items, said oven arranged for heating said byproduct by means of electricity generated by said fuel cell. 21. The system according to any of the preceding items, said reactor being part of said first loop and said second loop. 22. The system according to any of the preceding items, said electrolyte comprising an aqueous alkaline solution. 23. The system according to any of the preceding items, said fuel cell being an alkaline fuel cell.

Claims

1 CLAIMS 1. A system for generating electricity and for extracting carbon dioxide from the air, said system comprising: a fuel cell including: a pair of electrodes including an anode and a cathode separated by an electrolyte, - a first inlet constituting a fuel inlet for introducing a non-carbon binding fuel into said fuel cell for oxidization at said anode, - a second inlet constituting an air inlet for introducing air into said fuel cell at said cathode, said air reacting with said electrolyte and producing a product, - a third inlet constituting an electrolyte inlet for introducing electrolyte into said fuel cell, - an outlet for outlet of said product from said fuel cell, - a reactor for reacting with said product for producing replenished electrolyte and a by- product, - a first loop for circulating a first metal for binding hydroxide in said electrolyte from said fuel cell through said reactor and back to said fuel cell, and - a second loop for circulating a second metal for binding carbon from said reactor to an oven and back to said reactor.

2. The system according to any of the preceding claims, said first metal being an alkali metal such as potassium.

3. The system according to any of the preceding claims, said second metal being an alkali earth metal such as calcium.

4. The system according to any of the preceding claims, said oven comprising a chamber, and a seventh inlet for introducing said non-carbon bind- ing fuel into said oven for heating said chamber.2 5. The system according to any of the preceding claims, said oven arranged for heating said byproduct by means of electricity generated by said fuel cell.

6. The system according to any of the preceding claims, said electrolyte comprising an aqueous alkaline solution.

7. The system according to any of the preceding claims, said fuel cell being an alkaline fuel cell.

8. The system according to any of the preceding claims, comprising: a first pipe connected to said outlet for transporting said product away from said fuel cell.

9. The system according to any of the preceding claims, comprising: a second pipe connected to said third inlet for transporting electrolyte to said fuel cell.

10. The system according to any of the preceding claims, comprising: a third pipe for transporting said byproduct from said reactor to said oven.

11. The system according to any of the preceding claims, comprising: a fourth pipe for transporting Calcium oxide from said oven to said reactor.

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