Method for desorbing CO2 sorbed onto a sorbent

Abstract

A method (100) for desorbing CO2 sorbed onto a sorbent is proposed, wherein the sorbent is arranged in a separation chamber (14) of a CO2 separation device (10), comprising the steps of: - generating a negative pressure in the separation chamber (14) by means of a pump unit to remove atmospheric oxygen and subsequently desorbed CO2 from the separation chamber (14); - metering liquid water into the separation chamber (14) under negative pressure by means of a water metering unit (30) depending on a residual amount of atmospheric oxygen in the separation chamber (14) such that the liquid water in the separation chamber (14) evaporates to displace the residual amount of atmospheric oxygen from the separation chamber (14);and- heating the sorbent during the generation (106) of the vacuum by means of a temperature control unit, in particular an electric temperature control unit and / or a temperature control circuit, in order to desorb the sorbed CO2 from the sorbent.;

Description

Prior ArtThe invention relates to a method for desorbing sorbent-absorbed CO2 and to a CO2 separation device for desorbing sorbent-absorbed CO2.In order to limit the heating of the earth's atmosphere, so-called DAC systems (direct air capture) are used to separate or remove CO2(carbon dioxide) from the air.WO 2021 / 239747 A1 discloses a method for adsorbing and desorption of a sorbent used in cyclic adsorption desorption for collecting CO2directly from atmospheric ambient air or highly diluted sources. After the adsorption chamber has been closed, steam is injected in order to displace residual oxygen which would lead to adsorber material degradation at elevated temperature. Furthermore, the water vapor is used to directly heat the adsorber material and to provide the energy for desorption. Finally, the water vapor serves as inert gas with which the CO2is pumped out of the chamber.Disclosure of the InventionThe present invention relates to a method for desorbing CO2sorbed on a sorbent, wherein the sorbent is arranged in a separation chamber of a CO2 abtrennung device, comprising the steps:generating a negative pressure in the separation chamber by means of a pumping unit in order to discharge atmospheric oxygen and subsequently desorbed CO2from the separation chamber;metering liquid water into the separation chamber having the reduced pressure by means of a water metering unit as a function of a residual amount of atmospheric oxygen in the separation chamber in such a way that the liquid water in the separation chamber evaporates in order to displace the residual amount of atmospheric oxygen from the separation chamber; andheating the sorption agent during the generation of the negative pressure by means of a temperature control unit, in particular an electrical temperature control unit and / or a temperature control circuit, in order to desorb the sorbed CO2 from the sorption agent.The present invention further relates to a control unit which is configured to control and / or regulate the steps of the method described above.The present invention also relates to a CO2 separation device for desorbing CO2 absorbed on a sorption agent, comprisinga separation chamber for receiving the sorbent;a pumping unit for creating a negative pressure in the separation chamber to discharge atmospheric oxygen and subsequently desorbed CO2 from the separation chamber;a water metering unit for metering liquid water into the separation chamber as a function of a residual amount of atmospheric oxygen in such a way that the liquid water in the separation chamber evaporates in order to displace the residual amount of atmospheric oxygen from the separation chamber;a temperature control unit, in particular an electrical temperature control unit and / or a temperature control circuit, for heating the sorption agent in the separation chamber in order to desorb the sorbed CO2 from the sorption agent.According to the invention, it is proposed to meter liquid water into the separation chamber in a defined manner, so that atomization and in situ vaporization of the metered water in the separation chamber occur in order to displace a residual amount of atmospheric oxygen from the separation chamber, and to heat the sorption agent for the desorption process by means of a separate temperature control unit.As a result, the advantages of the water vapor can be utilized for inertization and desorption, wherein only a comparatively small defined amount of liquid water to be evaporated is required, since the desorption energy is supplied by means of the separate temperature control unit, for example in the form of electrical heating.Consequently, in contrast to the prior art mentioned at the beginning, a steam generator for generating large amounts of steam can be dispensed with. As a result, the overall size of the vacuum pump can be reduced, so that the overall system can be made more compact. Since the exact metering of steam is complicated and requires measuring and dispensing devices and heat-insulated lines up to a central steam generation system, the metering of liquid water according to the invention and the use of a separate temperature control unit can also be realized and regulated more efficiently and simply and economically.Desorption can be a chemical desorption and / or a physical desorption. In this case, the CO2can be released from the sorbent while introducing energy or introducing heat into the sorbent.The sorbent is preferably a solid (appropriately functionalized) sorbent, in particular a solid adsorbent and / or a solid absorbent. In this case, the sorbent can have, for example, a fibrous or nonwoven solid as a support structure with a base material which is selected from the group consisting of: resins, polymers, ceramics, zeolites, silicates, organometallic compounds, organic materials such as cellulose or activated carbon, and combinations thereof. The base material may in turn be specifically functionalized with amines, potassium carbonate or other components configured to chemically or physically bind CO2.By way of example, mention may be made of CO2 adsorption / absorption on amine compounds, for example Lewatit VP OC 1065, in which first CO2 and water adhere to molecules and then CO2 forms a strong bond by chemical reaction with the cooperation of the water, in order to be effective even at low CO2 concentrations.According to the invention, a reduced pressure is generated in the separation chamber by means of a pump unit in order to discharge or pump off atmospheric oxygen present or present in the separation chamber and subsequently desorbed CO2from the separation chamber. The negative pressure is in particular a vacuum. In other words, the atmospheric oxygen or the air is pumped out of the separation chamber at first, wherein at a chamber pressure of, for example, 100 mbar, a residual amount of atmospheric oxygen still remains present according to the partial pressure.The atmospheric oxygen is preferably the oxygen of the air from which the CO2was previously absorbed, i.e. which was previously supplied to the separation chamber for the sorption or which had previously flowed through the separation chamber.It is therefore advantageous if an air stream is fed into the separation chamber beforehand for sorption of the CO2on the sorption agent, i.e. the air flows through the separation chamber, and the separation chamber is closed with respect to the environment after the sorption process has ended.The pump unit can be connected, for example, to a vacuum connection of the separation chamber. The separation chamber is preferably designed such that it can be closed by means of valves, so that a reduced pressure can be generated therein by means of the pump unit. In this case, the separation chamber can have a valve unit with a multiplicity of, in particular, controllable valves, in order to close the separation chamber for the desorption. The valve unit may comprise an inlet valve arranged in an inlet duct for the supplied air flow and configured to close the inlet duct and isolate the separation chamber upstream. The valve unit may further comprise an outlet valve arranged in an outlet channel for the CO2-reduced air flow and configured to close the outlet channel and isolate the separation chamber downstream. The valve unit may also have a CO2 valve which is arranged in a CO2 outlet channel and is designed to open the CO2 outlet channel in order to discharge or pump desorbed CO2 from the separation chamber in a targeted manner.Subsequently, liquid water is metered, i.e. introduced or injected, into the separation chamber having the reduced pressure by means of a water metering unit in order to displace a residual amount of atmospheric oxygen from the separation chamber. The negative pressure in the separation chamber is maintained here, wherein the negative pressure value can change in an comprehensible manner and therefore does not have to remain constant.The water metering unit is accordingly designed to meter liquid water into the separation chamber, i.e. to introduce it or inject it in a defined manner. For this purpose, the water metering unit can have at least one spray nozzle, in particular a multiplicity of spray nozzles. The spray nozzles can be arranged distributed on the separation chamber.The metering of the liquid water takes place here as a function of a residual amount of atmospheric oxygen in the separation chamber, namely in such a way that the liquid water in the separation chamber evaporates and thereby displaces the residual amount of atmospheric oxygen from the separation chamber. Accordingly, the liquid water is metered in such a way that atomization occurs in the separation chamber and, depending on the pressure and temperature, in the liquid water which is also metered in situ is vaporized. The liquid water can be metered or injected into the separation chamber at a plurality of points.The step of metering the liquid water can be carried out or carried out during the step of generating the reduced pressure. In other words, in a first alternative, the step of generating the negative pressure is carried out continuously, so that the pump unit continues to pump off even during the metering of the liquid water. In a second alternative, the step of generating the negative pressure is interrupted during the step of metering the liquid water, so that although a negative pressure still exists or is present in the separation chamber, no suction or no pumping away by means of the pump unit takes place or is carried out. In both alternatives, the negative pressure in the separation chamber is maintained, wherein the negative pressure value can change in an comprehensible manner and therefore does not have to remain constant.In this case, the amount of liquid water is preferably selected as a function of the residual amount of atmospheric oxygen in the separation chamber. Further preferably, the amount of the liquid water is selected further depending on the reduced pressure generated and / or a temperature in the separation chamber. In this case, the amount of liquid water is preferably selected such that only as much water vapor volume is generated as is necessary in order to displace the remaining amount of atmospheric oxygen.For example, it boils at a pressure of 50 mbar. Water is already at 32.9 °C, so that it is sufficient to meter slightly heated water. If water is metered in at, for example, 50° C. at a pressure of 100 mbar (boiling temperature 45.8° C.), the water evaporates.It is advantageous if, in the metering step, the liquid water is metered continuously or periodically as a function of the residual amount of atmospheric oxygen in the separation chamber.It is furthermore advantageous if the step of metering is carried out until a / the residual quantity threshold value is reached. The residual quantity threshold value is selected in such a way that no degradation of the sorbent takes place during heating.It is also advantageous if the liquid water is added in the metering step- the sorbent; and / ora heatable support on which the sorbent is applied; and / ora heatable wall, in particular a heatable chamber wall of the separation chamber;metered, in particular injected, into a sorbent-free antechamber of the separation chamber.The residual amount of atmospheric oxygen in the separation chamber is preferably determined by means of an oxygen sensor, in particular in the region of the vacuum connection for the pump unit.Subsequently, during the generation of the reduced pressure, the sorption agent is heated by means of a temperature control unit, for example to 100° C., in order to desorb the sorbed CO2from the sorption agent. The temperature control unit is here a unit separate from the water metering unit. Furthermore, the temperature control unit naturally does not have a water vapor generator for providing water vapor. Rather, the temperature control unit preferably comprises or is an electrical temperature control unit and / or a temperature control circuit.Accordingly, the desorbed CO2and the co-desorbed water (co-adsorption of CO2and H2O) are pumped off, wherein, contrary to WO 2021 / 239747 A1 described at the beginning, no additionally introduced water vapor has to be removed. The temperature and the water desorbed in parallel with the CO2 fortwährend result in a mixture of CO2and H2O in the separation chamber continuously until the desorption process is complete, i.e. an equilibrium has been established by pumping down at, for example, 100 mbar and the temperature 100° C.In this case, it is advantageous if the heating step is carried out as a function of the residual amount of atmospheric oxygen in the separation chamber, in particularperforming only from and / or below a remaining quantity threshold value; orperforming the sorption agent above a residual amount threshold value to a first temperature and below and / or below the residual amount threshold value to a higher second temperature.It is furthermore advantageous if a further metering of liquid water into the separation chamber by means of the water metering unit after termination of the desorption process is carried out, however, during the generation of the reduced pressure in order to cool the separation chamber. The further metering of liquid water is effected in particular in such a way that the liquid water evaporates in the separation chamber and condensation of the evaporated water is avoided to the greatest possible extent. In this case, it is also advantageous if the quantity of liquid water is selected as a function of the difference between an actual temperature in the separation chamber and a setpoint temperature.In other words, after the desorption process for cooling the system, a defined amount of liquid water is metered in, since this evaporates and absorbs heat during the evaporation. Since water vapor is predominantly formed and the reduced pressure continues to be generated, it is pumped off and discarded. With accurate metering of liquid water and detection of the temperature in the separation chamber, condensation can be avoided since equilibrium is established, i.e. the system is "dry" at, for example, 100 mbar and 60° C. When a temperature is reached which is not critical for air contact of the sorbent, for example <6° C., the water metering is stopped and the separation chamber is opened again to atmosphere.Optionally, the water metering can be stopped and the pressure can be lowered further to 50 mbar, so that the residual water reliably evaporates.The control unit according to the invention is configured to control and / or regulate the steps of the method described above. In this case, the control unit is preferably configured for controlling and / or regulating the entire sorption and desorption process.The control unit can be designed to be connected to other control units and / or a central control unit of the CO2 abtrennung device or of a superordinate system by means of radio transmission such as W-LAN, Bluetooth, near-field communication, etc.The CO2 abtrennung device is configured to desorb CO2sorbed on a sorbent. In this case, the CO2 abtrennung device is in particular configured to release or dissolve the CO2from the sorbent by means of a desorption process in which the CO2is released from the sorbent while introducing energy or introducing heat into the sorbent. Accordingly, the desorption method can comprise in particular at least one of the following methods or mixed forms thereof:chemical desorption methodphysical desorption methodThe CO2 abtrennung device is preferably further configured for sorbing CO2from a supplied air stream by means of a sorption method. In this case, the CO2 abtrennung device is in particular designed to separate the CO2from the supplied air stream by means of a sorption method in which the separation takes place with energy output or heat output to the air stream. The separation process preferably comprises an adsorption process and / or an absorption process. Accordingly, the sorption method can comprise at least one of the following methods or mixed forms thereof:chemical adsorption methodphysical adsorption process- chemical absorption methodphysical absorption methodThe CO2 abtrennung device is preferably designed to carry out the sorption process and the desorption process cyclically. The basic mode of operation of the CO2 abtrennung device can be carried out, for example, analogously to WO 2021 / 239747 A1 mentioned at the beginning.Within the scope of the present invention, the term "feeding" or "supplied" primarily encompasses an actively carried out or initiated and thus technically controlled or regulated feeding of the air stream by means of a blower unit or fan unit of the CO2 abtrennung device. The term "feeding" or "supplied" can, however, also comprise a passively carried out or initiated feeding of the air flow without thereby departing from the scope of the present invention. Consequently, the air flow can be supplied in any desired manner, for example in a natural manner (as wind).The CO2 abtrennung device may further include at least one of the following units:- the control unit described above; and / orblower unit, in particular having a plurality of fans for supplying the air flow.In particular, the CO2 abtrennung device or the CO2 abtrennung system can be part of a building climate system, in particular integrated in a climate system in a building. In this case, the separation chamber of the CO2 abtrennung device can be integrated into the air-conditioning circuit of the building, so that the fan present there in any case can quickly cool down the sorbent, since no large heat capacities in the system have a damping effect. The air conditioning device can also be temporarily colder for cooling, should this be advantageous overall.DRAWINGSThe invention is explained in more detail below by way of example with reference to the attached drawings. The following are shown: FIG. 1 is a schematic illustration of a CO2 abtrennung device according to the invention; and FIG. 2 shows a flow diagram of a method according to an exemplary embodiment.Fig. 1 shows a CO2 abtrennung device, which is denoted in its entirety by the reference numeral 10.The CO2 abtrennung device 10 is configured to separate CO2(carbon dioxide) from an air flow 12 supplied by a blower unit (not shown) by a cyclically operable adsorption-desorption process.For this purpose, the CO2 abtrennung device 10 has a separation chamber 14 for receiving a sorption agent (not shown). The separation chamber 14 has an inlet valve 16 at an inlet duct 18 for the intake air flow 12 which is designed to close the inlet duct 18 and to isolate the separation chamber 14 upstream. The separation chamber 14 further comprises an outlet valve 20 at an outlet channel 22 for the CO2-reduced air flow 12', which is configured to close the outlet channel 22 and isolate the separation chamber 14 downstream. The separation chamber 14 also has a CO2 valve 24, which is arranged in a CO2 outlet duct 26 and is designed to open the CO2 outlet duct 26 in order to discharge adsorbed, i.e. bound / filtered and re-desorbed, i.e. released, CO2 from the separation chamber 14 in a targeted manner into a plant 28 for permanent CO2 removal with CO2 conditioning.The CO2 abtrennung device 10 further includes a pumping unit for generating a negative pressure in the separation chamber 14 to discharge a remaining amount of atmospheric oxygen and then desorbed CO2from the separation chamber 14 through the CO2 auslasskanal channel 26.The CO2 abtrennung device 10 further comprises a water dosing unit 30 for dosing liquid water into the separation chamber 14. The water metering unit 30 is designed to meter the liquid water into the separation chamber 14 in such a way that it evaporates and displaces a residual amount of atmospheric oxygen from the separation chamber 14 during the generation of the reduced pressure.The CO2 abtrennung device 10 further comprises an electrical temperature control unit (not shown) for heating the sorbent in the separation chamber 14 to desorb the sorbed CO2from the sorbent.FIG. 2 shows a flow diagram of an exemplary embodiment of the approach presented here as a method 100 for desorbing CO2sorbed on a sorption agent, wherein the sorption agent is arranged in a separation chamber 14 of a CO2 abtrennung device 10. The method 100 comprises a step of generating 106 a negative pressure in the separation chamber 14 by means of a pumping unit in order to discharge atmospheric oxygen and subsequently desorbed CO2from the separation chamber 14. The method 100 further comprises a step of metering 108 liquid water into the separation chamber 14 having the reduced pressure by means of a water metering unit 30 as a function of a residual amount of atmospheric oxygen in the separation chamber 14 in such a way that the liquid water in the separation chamber 14 evaporates in order to displace the residual amount of atmospheric oxygen from the separation chamber 14. The method 100 also comprises a step of heating 110 the sorption agent during the generation 106 of the reduced pressure by means of a temperature control unit, in particular an electrical temperature control unit and / or a temperature control circuit, in order to desorb the sorbed CO2from the sorption agent.The method 100 further comprises an optional step of supplying 102 an air stream 12 into the separation chamber 14 for sorption of the CO2on the sorbent and an optional step of closing 104 the separation chamber 14 from the environment after completion of the sorption process.If an exemplary embodiment comprises an "and / or" combination between a first feature and a second feature, this is to be read in such a way that the exemplary embodiment has both the first feature and the second feature according to one embodiment and either only the first feature or only the second feature according to a further embodiment.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2021 / 239747 A1 [0003, 0028, 0037]

Claims

A method (100) for desorbing CO2 sorbed on a sorbent, wherein the sorbent is arranged in a separation chamber (14) of a CO2 separation device (10), comprising the steps: - generating (106) a reduced pressure in the separation chamber (14) by means of a pump unit in order to discharge atmospheric oxygen and subsequently desorbed CO2 from the separation chamber (14); - metering (108) liquid water into the separation chamber (14) having the reduced pressure by means of a water metering unit (30) in dependence on a residual amount of atmospheric oxygen in the separation chamber (14) in such a way that the liquid water in the separation chamber (14) evaporates in order to displace the residual amount of atmospheric oxygen from the separation chamber (14); heating (110) of the sorption agent during the generation (106) of the reduced pressure by means of a temperature control unit, in particular an electrical temperature control unit and / or a temperature control circuit, in order to desorb the sorbed CO2 from the sorption agent.Method (100) according to claim 1, characterised in that the step of creating (106) the negative pressure is interrupted or carried out continuously during the step of dosing (108) the liquid water.Method (100) according to Claim 1 or 2, characterized in that the step of heating (110) is carried out as a function of the residual amount of atmospheric oxygen in the separation chamber (14), in particular - is carried out only from and / or below a residual amount threshold value; or - is carried out in such a way that the sorbent is heated to a first temperature above a residual amount threshold value and from and / or below the residual amount threshold value to a higher second temperature.Method (100) according to one of the preceding claims, characterized in that, in the metering step (108), the amount of the liquid water is selected as a function of the residual amount of atmospheric oxygen in the separation chamber (14).Method (100) according to Claim 4, characterized in that, in the metering step (108), the quantity of the liquid water is also selected as a function of the reduced pressure generated and / or a temperature in the separation chamber (14).Method (100) according to one of the preceding claims, characterized in that, in the metering step (108), the liquid water is metered continuously or periodically as a function of the residual amount of atmospheric oxygen in the separation chamber (14).Method (100) according to one of the preceding claims, characterized in that the metering step (108) is carried out until a / the residual quantity threshold value is reached.Method (100) according to one of the preceding claims, characterized in that, in the metering step (108), the liquid water is - sprayed onto the sorption agent; and / or - onto a heatable carrier on which the sorption agent is applied; and / or - sprayed onto a heatable wall, in particular heatable chamber wall, of the separation chamber (14), and / or - metered, in particular injected, into a sorption agent-free antechamber of the separation chamber.Method (100) according to one of the preceding claims, characterized in that the residual quantity of atmospheric oxygen in the separation chamber (14) is determined by means of an oxygen sensor, in particular in the region of a reduced-pressure connection for the pump unit.Method (100) according to one of the preceding claims, characterized bythe steps of: - supplying (102) an air stream (12) into the separation chamber (14) for sorption of the CO2 on the sorption agent; and - closing (104) the separation chamber (14) with respect to the environment after termination of the sorption process.Method (100) according to one of the preceding claims, characterized bythe further step: - further metering of liquid water into the separation chamber (14) by means of the water metering unit (30) after termination of the desorption process in order to cool the separation chamber (14), in particular in such a way that the liquid water in the separation chamber (14) evaporates and condensation of the evaporated water is avoided to the greatest possible extent.Method (100) according to claim 11, characterised in that in the step of further metering the quantity of liquid water is selected as a function of the difference between an actual temperature in the separation chamber (14) and a desired temperature.Control unit which is configured to control and / or regulate the steps of the method (100) according to one of the preceding claims.A CO2 separation device (10) for desorbing CO2 sorbed on a sorbent, comprising - a separation chamber (14) for receiving the sorbent; - a pumping unit for generating a reduced pressure in the separation chamber (14) in order to discharge atmospheric oxygen and subsequently desorbed CO2 from the separation chamber (14); - a water dosing unit (30) for dosing liquid water into the separation chamber (14) depending on a residual amount of atmospheric oxygen in such a way that the liquid water in the separation chamber evaporates in order to displace the residual amount of atmospheric oxygen from the separation chamber; a temperature control unit, in particular an electrical temperature control unit and / or a temperature control circuit, for heating (110) the sorption agent in the separation chamber (14) in order to desorb the sorbed CO2 from the sorption agent.The CO2 separation apparatus (10) according to claim 14, comprising a control unit according to claim 13.

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