Continuous solvent recovery in a power to x methanol plant

Abstract

The invention relates to method for recovering carbon capture solvent from reactant streams in a power-to-X plant for methanol production, said power-to-X plant comprising an electrolyzer, a unit capturing COX with a carbon capture solvent, a syngas compressor and a methanol reactor, wherein the electrolyzer creates a H2 stream and wherein the unit 5 capturing COX creates a stream of COX. The carbon capture solvent is returned to the unit capturing COX.

Description

[0001] TITLE

[0002] Continuous solvent recovery in a Power to X methanol plant

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a method for solvent recovering in a Power to X methanol plant, where said plant uses freshly captured COXwhen preparing a syngas for methanol production.

[0005] BACKGROUND OF THE INVENTION

[0006] Recently a new concept called Power-to-X has emerged. In this concept renewable power is used to produce hydrogen in an electrolyzer and then hydrogen is used either directly or processed further to other products like methanol, ammonia or e-natural gas. In the methanol case the hydrogen is then forced to react with a carbon to form a combustible liquid fuel, methanol. In figure 1 is illustrated a conceptual Power-to-X methanol plant. Here renewable power is used to electrolyze water into hydrogen and oxygen. Given that water is the source for hydrogen, the H2 stream resulting from the electrolysis is saturated with or at least contains a lot of moisture. The COx for the methanol reaction is either freshly captured e.g. from a fluegas or it can be freshly released from a carbon captured storage e.g. from a liquid COx transported by tankers or similar. Freshly captured COx from fluegas in particular, but also freshly released COx contains a signification amount of moisture, just as the hydrogen as previously described. Further the COx stream comprises amounts of carbon capture solvents, typically amines. At some point the H2stream and the COx stream are combined into one stream and compressed in a syngas compressor to a syngas stream ready for methanol reaction in the methanol reactor. However, the moisture and the carbon capture solvents in the streams need to be reduced in order for the methanol reaction to occur and in order not to pollute the environment.

[0007] WO 2022 / 200315 A1 describes a Power-to-X plant comprising an electrolyzer and a unit for carbon capturing. In one version the plant of WO 2022 / 200315 A1 is for production of methanol. The plant recovers carbon capture solvent in an non-continuous operation.

[0008] Various types of carbon capturing systems are described in the literature. US 2020 / 0114305 A1 , US 2015 / 0233577 A1 , US 2021 / 0322921 A1 , US 2021 / 0213383 A1 and EP 3097970 A1 describe such carbon capturing systems. Each system has its own internal recirculation systems for recovering carbon capture solvent internally in the unit for carbon capturing.

[0009] The inventors have found that by removing moisture and carbon capture solvent in a certain sequence it is possible to reduce the environmental load and run the plant more efficiently. Especially the removal of carbon capture solvent becomes so efficient that it is possible to recycle the carbon capture solvent directly back into a carbon capturing unit so that it can be run in a continuous mode of operation.

[0010] SUMMARY OF INVENTION

[0011] According to the invention there is provided a method for recovering carbon capture solvent from reactant streams in a power-to-X plant for methanol production, said power- to-X plant comprising an electrolyzer, a unit capturing COx with a carbon capture solvent, a syngas compressor and a methanol reactor, wherein the electrolyzer creates a H2 stream and wherein the unit capturing COx creates a stream of COx, the method comprising the steps of:

[0012] Compressing the H2stream to between 2 and 100 bar(a) in a H2compressing step so as to create a compressed H2stream and a first condensate;

[0013] Compressing the COx stream to between 2 and 100 bar(a) in a COx compressing step so as to create a compressed COx stream and a second condensate, the second condensate comprising condensed carbon capture solvent combining the compressed H2stream with the compressed COx stream to a compressed syngas reacting the compressed syngas into methanol in the methanol reactor wherein at least a part of the second condensate is returned to the unit capturing COx.

[0014] According to another aspect of the invention there is provided a method for recovering carbon capture solvent from reactant streams in a power-to-X plant for methanol production, said power-to-X plant comprising an electrolyzer, a unit capturing COx with a carbon capture solvent, a syngas compressor and a methanol reactor, wherein the electrolyzer creates a H2stream and wherein the unit capturing COx and / or the unit with captured COXcreates a stream of COx, the method comprising the steps of:

[0015] Compressing the H2stream to between 2 and 100 bar(a) in a H2compressing step so as to create a compressed H2stream and a first condensate; Compressing the COx stream to between 2 and 100 bar(a) in a COx compressing step so as to create a compressed COx stream and a second condensate, the second condensate comprising condensed carbon capture solvent combining the compressed H2 stream with the compressed COx stream to a compressed syngas reacting the compressed syngas into methanol in the methanol reactor wherein at least a part of the second condensate is returned to the unit capturing COx without further up-concentration

[0016] The inventors have realized that the condensate from compressing a released stream of COx from a carbon capturing unit contains enough carbon capture solvent to be returned to the carbon capturing unit without further up-concentration. This is surprising as a typical carbon capturing unit has multiple internal steps of recovering the carbon capture solvent including compressing and expanding of gaseous streams. Nevertheless, at least a part of the condensate from the compressing of the COx stream as described in the method can be returned to the carbon capturing unit without further up-concentration and thereby allowing a continuous mode of operation for the entire plant. Previously, all the condensates have been collected for final cleaning and / or recovery in batch processes or the condensates have been released to the surroundings.

[0017] In yet another aspect of the invention there is provided a method for recovering carbon capture solvent from reactant streams in a power-to-X plant for methanol production, said power-to-X plant comprising an electrolyzer, a unit capturing COx with a carbon capture solvent, a syngas compressor and a methanol reactor, wherein the electrolyzer creates a H2 stream and wherein the unit capturing COx and / or the unit with captured COXcreates a stream of COx, the method comprising the steps of:

[0018] Compressing the H2 stream to between 2 and 100 bar(a) in a H2 compressing step so as to create a compressed H2 stream and a first condensate;

[0019] Compressing the COx stream to between 2 and 100 bar(a) in a COx compressing step so as to create a compressed COx stream and a second condensate, the second condensate comprising condensed carbon capture solvent combining the compressed H2stream with the compressed COx stream to a compressed syngas reacting the compressed syngas into methanol in the methanol reactor wherein at least a part of the second condensate is returned to the unit capturing COx in a continuous process.

[0020] The continuous process for returning the second condensate can come in various forms. It can be without further up-concentration. This is the most simple form. The continuous process for returning the second condensate can also be a continuous process involving continuous water evaporation, continuous separation processes or the like.

[0021] The inventors have realized that the condensate from compressing a released stream of COx from a carbon capturing unit contains enough carbon capture solvent to be returned to the carbon capturing unit in a continuous process. Previously, it has only been considered possible to use batch processes with their inherent higher costs to recover any remaining carbon capture solvent. However, the content of carbon capture solvent has usually been considered so low that it has been released to the surroundings with the waste water. This is surprising as a typical carbon capturing unit has multiple internal steps of recovering the carbon capture solvent including compressing and expanding of gaseous streams.

[0022] In a preferred embodiment the compressed H2 stream is combined with the compressed COx stream and compressed together to a compressed syngas.

[0023] When the compressed H2 stream is combined with the compressed COx stream and compressed to a compressed syngas, it is preferred that the H2 stream is compressed to between 2 and 20 bar(a) and / or the COx stream is compressed to between 2 and 20 bar(a) so as to form a compressed H2 and / or compressed COx stream respectively

[0024] Typically in such plants you would like to remove moisture in one step as it is believed to be most efficient in that way and also to reduce the amount of equipment: However, the inventors surprisingly have found that by compressing the H2 stream and the COx stream independently and combining them after the first compression and before the syngas compressor multiple advantages can be achieved.

[0025] The recovered and condensed carbon capture solvent together with at least a part of the condensed water present in the second condensate can be returned directly to the carbon capturing unit. If the H2 stream and the COx stream were combined before compression too much water would be present in the resulting condensate solvent and a separation step would be required. Otherwise, the carbon capturing unit will stop functioning as the carbon capturing solvent would be too diluted or that there would be to much liquid in the system for it to function properly.

[0026] Compressing the H2 stream and the COx separately also solves a waste problem. The condensed water from the H2 stream does not contain any traces of the carbon capturing solvent and hence can be freely released into the surroundings. If the two streams were combined before compression it has been discovered that too much carbon capturing solvent would be released into the environment or requiring handling via waste treatment.

[0027] Preferably, the second condensate is returned to the unit capturing COx without further up-concentration. This has the advantage the plant will be able to deliver the service of fast transfer to a low energy consumption regime as the system becomes simpler.

[0028] COx can be carbon monoxide, carbon dioxide and mixtures thereof. Preferably COx is carbon dioxide (CO2).

[0029] The carbon capturing solvent used in the carbon capture unit is preferably an amine or ketone based solvent. Particularly preferred are bifunctional amine based solvents such as solvents with both a primary amine and a primary or secondary alcohol also known as amino alcohols. Examples of such preferred amino alcohols are methanolamine, ethanolamine, 1-amino-2-propanol, 3-amino-1 -propanol. The person skilled in the art would know other solvents in the family of amino alcohols.

[0030] A particularly preferred carbon capturing solvent is ethanolamine also known as 2- aminoethanol, monoethanolamine, ETA or MEA.

[0031] An example of a ketone based solvent is acetone.

[0032] In a preferred embodiment the Power-to-X plant further comprises a guard reactor. The guard reactor has the purpose of protecting the methanol reactor from impurities, such as impurities that could be present in the COx stream

[0033] Preferably the H2 stream is compressed to between 2 and 20 bar(a), more preferably to between 3 and 15 bar(a) and most preferably between 4 and 10 bar(a).

[0034] Preferably the COx stream is compressed to between 2 and 20 bar(a), more preferably to between 3 and 15 bar(a) and most preferably between 4 and 10 bar(a).

[0035] Preferably the pressure difference between the compressed H2 stream and the compressed COx stream is no more than 5 bar, preferably no more than 3 bar and most preferred no more than 1 bar.

[0036] The invention further relates to a Power-to-X plant for methanol production configured for carrying out the method for removing moisture and recovering carbon capture solvent from reactant streams said power-to-X plant for methanol production comprising: an electrolyzer for generating a H2stream a unit capturing COx with a carbon capture solvent for creating a COx stream and a methanol reactor connected to the H2 stream and the COx stream wherein the Power-to-X plant for methanol production further comprises a H2 compressor with a H2 compressor inlet and a H2 compressor outlet, the H2 compressor inlet is connected to the electrolyzer a COx compressor with a COx compressor inlet and a COx compressor outlet, the COx compressor inlet is connected to the unit capturing COx a recirculation piping from the COx compressor for returning condensate with carbon capture solvent to the unit capturing COx piping for connecting the H2 compressor outlet with the COx compressor outlet

[0037] In a further aspect the invention relates to a Power-to-X plant for methanol production configured for carrying out the method for removing moisture and recovering carbon capture solvent from reactant streams, said power-to-X plant for methanol production comprising: an electrolyzer for generating a H2 stream a unit capturing COx with a carbon capture solvent for creating a COx stream and a methanol reactor connected to the H2 stream and the COx stream wherein the Power-to-X plant for methanol production further comprises a H2 compressor with a H2 compressor inlet and a H2 compressor outlet, the H2 compressor inlet is connected to the electrolyzer a COx compressor with a COx compressor inlet and a COx compressor outlet, the COx compressor inlet is connected to the unit capturing COx a recirculation piping from the COx compressor for returning condensate with carbon capture solvent to the unit capturing COx in a continuous process piping for connecting the H2 compressor outlet with the COx compressor outlet.

[0038] The piping for returning the carbon capture solvent in a continuous process can be a direct line, so that no further up-concentration in carried out or it can be via an evaporator or a separator or similar equipment that runs in a continuous operation.

[0039] In another aspect the invention relates to a Power-to-X plant for methanol production configured for carrying out the method for removing moisture and recovering carbon capture solvent from reactant streams, said power-to-X plant for methanol production comprising: an electrolyzer for generating a H2 stream a unit capturing COx with a carbon capture solvent for creating a COx stream and a methanol reactor connected to the H2 stream and the COx stream wherein the Power-to-X plant for methanol production further comprises a H2 compressor with a H2 compressor inlet and a H2 compressor outlet, the H2 compressor inlet is connected to the electrolyzer a COx compressor with a COx compressor inlet and a COx compressor outlet, the COx compressor inlet is connected to the unit capturing COx a recirculation piping from the COx compressor for returning condensate with carbon capture solvent without further up-concentration to the unit capturing COx piping for connecting the H2 compressor outlet with the COx compressor outlet.

[0040] Preferably the Power-to-X plant further comprises a syngas compressor with a syngas compressor inlet and a syngas compressor outlet where the syngas compressor inlet is connected with the H2 compressor outlet and the COx compressor outlet so that a compressed H2 stream and a compressed COx stream is combined prior compression into a compressed syngas.

[0041] In a preferred embodiment the Power-to-X plant for methanol production further comprises a guard reactor and piping for connecting it with the methanol reactor

[0042] The invention further relates to a control unit for controlling the method for recovering carbon capture solvent from reactant streams in a power-to-X plant for methanol production comprising an electrolyzer, a unit capturing COx, a syngas compressor and a methanol reactor, wherein the electrolyzer creates a H2stream and wherein the unit capturing COx creates a stream of COx the control unit comprises means for controlling the H2 compressor and means for controlling the COx compressor

[0043] LIST OF FIGURES

[0044] Fig. 1 is a schematic illustration of a conceptual Power-to X methanol plant

[0045] Fig. 2 is a schematic illustration of a Power-to X methanol plant according to the invention Fig. 3 is a schematic illustration of a Power-to X methanol plant with guard reactor according to the invention

[0046] Fig. 4 is a schematic illustration of a Power-to X methanol plant according to the invention without a syngas compressor

[0047] DESCRIPTION OF DRAWINGS

[0048] Figure 1 illustrates a conceptual overview of a Power-to-X methanol plant where renewable power (ren. Power) is used to run an electrolyzer so as to generate a H2stream. From a COx source COx is either freshly captured or captured one place and released in the plant so as to create a COx stream. The H2stream and the COx stream are combined into one stream and compressed in a syngas compressor (compr) to create a compressed syngas that is lead into a reactor that converts it into methanol. The present invention addresses the steps prior to the syngas compressor so as to improve the operation of Power-to-X methanol plants.

[0049] Figure 2 illustrates a part of a Power-to-X plant 1 configured to carrying out one embodiment of the invention. The Power-to-X plant 1 comprises an electrolyzer 2 which uses renewable power such as wind power to electrolyze water into hydrogen H2 and oxygen O2. The oxygen is released to the atmosphere or sold elsewhere whereas a H2 stream is collected and turned into a H2 stream, said H2 stream contains a lot of moisture because it originates from the electrolysis of water. The power-to-X plant 1 further comprises a unit capturing COx with a carbon capture solvent 3. Preferably the COx preferably is carbon dioxide but the invention will work equally well with carbon monoxide or mixtures of carbon monoxide and carbon dioxide. In the plant there is also a syngas compressor 4 with a syngas compressor inlet 5 and a syngas compressor outlet 6. In the syngas compressor the syngas is conditioned and compressed to conditions as defined by the methanol reactor 7. The syngas compressor outlet 6 is connected to the methanol reactor 7 in which the syngas reacts and forms methanol. Methanol reactors 7 are known in the field. From the electrolyzer the H2 stream is conveyed to a H2 compressor inlet 9 and from there into the H2 compressor 8. In the H2 compressor 8 the H2 stream is compressed and during that compression moisture condensate and is removed from the stream. The result is a compressed H2 stream leaving the H2 compressor 8 via the H2 compressor outlet 10. In the embodiment shown in figure 2 there is no branching off of a side stream of H2. From the unit capturing COx 3 the COx stream is conveyed to a COx compressor 11 having a COx compressor inlet 12 and a COx compressor outlet 13. In the COx compressor COx is compressed so that moisture and carbon capture solvent is condensed. The condensed carbon capture solvent and at least a part of the condensed moisture is returned via a recirculation piping 14 to the unit capturing COx 3 where it can be used directly. Via the COx compressor outlet a stream of compressed COx is combined with the main stream of compressed H2. The steams are combined prior to reaching the syngas compressor inlet 5. With the term syngas compressor inlet is understood that the streams also can be combined inside the syngas compressor with the same result. In variants the condensed moisture is returned continuously via other units working in a continuous mode. These other units could be evaporators or separators. Figure 3 illustrates an embodiment where the Power-to-X plant 1 further comprises a guard reactor 16. The guard reactor 16 is positioned upstream of the methanol reactor 7 and protects the methanol reactor from impurities that might the present in the reactant streams, such as impurities in the COx stream. The guard reactor can get its reactants from various places which is know the person skilled in the art.

[0050] Figure 4 illustrates the embodiment, where the Power to X plant of figure 3 does not comprise a syngas compressor. In such a plant the H2 compressor 8 and the COx compressor 11 compress the streams sufficiently for the combined stream to be let directly to the methanol reactor 7 optionally via a guard reactor 16. Figure 4 further illustrates a rerouting system 17, 18, 19 for rerouting COx to a point upstream of the unit capturing COx 3.

[0051] REFERENCES

[0052] 1 Power to X plant

[0053] 2 electrolyzer

[0054] 3 unit capturing COx

[0055] 4 syngas compressor

[0056] 5 syngas compressor inlet

[0057] 6 syngas compressor outlet

[0058] 7 methanol reactor

[0059] 8 H2 compressor

[0060] 9 H2 compressor inlet

[0061] 10 H2 compressor outlet

[0062] 11 COx compressor

[0063] 12 COx compressor inlet

[0064] 13 COx compressor outlet

[0065] 14 recirculation piping

[0066] 16 guard reactor

[0067] 17 branching point

[0068] 18 COx rerouting piping

[0069] 19 front end of the carbon capture unit

Claims

CLAIMS1 . A method for recovering carbon capture solvent from reactant streams in a power- to- X plant (1) for methanol production, said power-to-X plant (1) comprising an electrolyzer (2), a unit capturing COx (3) with a carbon capture solvent, a syngas compressor (4) and a methanol reactor (7), wherein the electrolyzer (2) creates a H2 stream and wherein the unit capturing COx (3) and / or the unit with captured COXcreates a stream of COx the method comprising the step of:Compressing the H2 stream to between 2 and 100 bar(a) in a H2 compressing step so as to create a compressed H2 stream and a first condensate;Compressing the COx stream to between 2 and 100 bar(a) in a COx compressing step so as to create a compressed COx stream and a second condensate, the second condensate comprising condensed carbon capture solvent combining the compressed H2stream with the compressed COx stream to a compressed syngas reacting the compressed syngas into methanol in the methanol reactor (7) characterized in that at least a part of the second condensate is returned to the unit capturing COx (3) without further up-concentration2. A method for recovering carbon capture solvent from reactant streams in a power-to- X plant (1) for methanol production, said power-to-X plant (1) comprising an electrolyzer (2), a unit capturing COx (3) with a carbon capture solvent, a syngas compressor (4) and a methanol reactor (7), wherein the electrolyzer creates a H2 stream and wherein the unit capturing COx (3) and / or the unit with captured COXcreates a stream of COx the method comprising the step of:Compressing the H2 stream to between 2 and 100 bar(a) in a H2 compressing step so as to create a compressed H2 stream and a first condensate;Compressing the COx stream to between 2 and 100 bar(a) in a COx compressing step so as to create a compressed COx stream and a second condensate, the second condensate comprising condensed carbon capture solvent combining the compressed H2stream with the compressed COx stream to a compressed syngas reacting the compressed syngas into methanol in the methanol reactor (7)characterized in that at least a part of the second condensate is returned to the unit capturing COx (3) in a continuous process.

3. A method according to claim 1 or 2 wherein the compressed H2 stream and the compressed COx is combined and compressed into a compressed syngas4. A method according to any one of the preceding claims , wherein COx is carbon dioxide5. A method according to any one of the preceding claims wherein the carbon capturing solvent is an amino alcohol6. A method according to any one of the preceding claims wherein the carbon capturing solvent is ethanolamine7. A method according to claim 1-6 wherein the power-to-X plant for methanol production further comprises a guard reactor.

8. A method according to any one of the preceding claims wherein the difference between the compressed H2 stream and the compressed COx stream is no more than 5 bar, preferably not more than 3 bar and most preferred no more than 1 bar.

9. A method according to any one of the preceding claims wherein the second condensate is returned to the unit capturing COx without further up-concentration.

10. A Power-to-X plant (1) for methanol production configured for carrying out the method according to claim 1-9 said power-to-X plant (1) for methanol production comprising:- an electrolyzer (2) for generating a H2 stream- a unit capturing COx (3) with a carbon capture solvent for creating a COx stream- and a methanol reactor (7) connected to H2 stream and the COx stream wherein the Power-to-X plant for methanol production further comprises- a H2compressor (8) with a H2compressor inlet (9) and a H2compressor outlet (10), the H2compressor inlet (9) is connected to the electrolyzer (2)- a COx compressor (11) with a COx compressor inlet (12) and a COx compressor outlet (13), the COx compressor inlet (11) is connected to the unit capturing COx (3)- a recirculation piping (14) from the COx compressor (11) for returning condensate with carbon capture solvent without further up-concentration to the unit capturing COx (3)- piping for connection the H2 compressor outlet (10) with the COx compressor outlet (13)11. A Power-to-X plant (1) for methanol production configured for carrying out the method according to claim 1-9 said power-to-X plant (1) for methanol production comprising: an electrolyzer (2) for generating a H2 stream a unit capturing COx (3) with a carbon capture solvent for creating a COx stream and a methanol reactor (7) connected to the H2stream and the COx stream wherein the Power-to-X plant (1) for methanol production further comprises a H2 compressor (8) with a H2 compressor inlet (9) and a H2 compressor outlet (10), the H2 compressor inlet (9) is connected to the electrolyzer (2) a COx compressor (11) with a COx compressor inlet (12) and a COx compressor outlet (13) , the COx compressor inlet (11) is connected to the unit capturing COx (3) a recirculation piping (14) from the COx compressor (11) for returning condensate with carbon capture solvent to the unit capturing COx (3) in a continuous process piping for connecting the H2 compressor outlet (10) with the COx compressor outlet (13).

12. A Power-to-X plant according to claim 10 or 11 wherein the Power-to-X plant (1 ) further comprises a guard reactor (16).

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