Installation and method for separating carbon dioxide from the ambient air

Abstract

The invention relates to an installation (10) for separating carbon dioxide from the ambient air. The installation (10) comprises a dehumidifying unit (20) for dehumidifying a gas stream of ambient air and a carbon dioxide separating unit (40) which is downstream of the dehumidifying unit (20) in the flow direction of a gas stream through the installation (10). The carbon dioxide separating unit (40) comprises an adsorption chamber (42) and a desorption chamber (44) different from the adsorption chamber (42). A sorbent (58) is disposed in the carbon dioxide separating unit (40). The carbon dioxide separating unit (40) comprises a transport means (54) by which the sorbent (58) can be transported, after carbon dioxide has been taken up from a gas stream dried by the dehumidifying unit (20), from the adsorption chamber (42) into the desorption chamber (44) and / or, after the carbon dioxide has been desorbed from the sorbent (58), from the desorption chamber (44) into the adsorption chamber (42). The invention further relates to a method for separating carbon dioxide from the ambient air using an installation (10) of this type.

Description

[0001] Description

[0002] Plant and process for separating carbon dioxide from the ambient air

[0003] The invention relates to a plant for separating carbon dioxide from the ambient air and to a method for separating carbon dioxide from the ambient air using such a plant according to the preamble of the independent patent claims.

[0004] The need to slow global climate change, which is being accelerated by greenhouse gas emissions, is extremely urgent. Above all, the increase in atmospheric carbon dioxide levels must be sustainably reduced. To reduce the carbon dioxide content in the ambient air and achieve climate neutrality, not only must carbon dioxide emissions be reduced, but unavoidable carbon dioxide emissions must also be compensated accordingly. A well-known method for separating carbon dioxide from the ambient air is the so-called "direct air capture (DAC) process," in which ambient air is passed through an adsorption chamber and the carbon dioxide contained in the ambient air is at least partially separated from the ambient air. Such processes are suitable for reducing the carbon dioxide content of the atmosphere and thus counteracting climate change.The development of powerful and efficient processes for separating carbon dioxide from the atmosphere is essential. One possibility is the use of a sorbent material for carbon dioxide capture. The carbon dioxide is chemically and / or physically bound and then released from the sorbent material by heating and reducing the pressure level. This concentrates the released carbon dioxide and feeds it into an intermediate storage facility or a subsequent process step that requires carbon dioxide as a feedstock.

[0005] To separate carbon dioxide from industrial plants and from the ambient air, systems, also known as direct air capture systems, are used, among others, with stationary (stationary) sorbent material. The sorbent material can be spherical or pellet-shaped and is usually a few millimeters in size. The sorbent is in loose form. The ambient air or industrial exhaust gases are passed over this sorbent bed, and the sorbent separates CO2 from the gas stream. The binding of carbon dioxide (CO2) to the sorbent is reversible. If the sorbent material used is sensitive to moisture, the gas stream must first be dehumidified. For this purpose, a dehumidification stage is installed upstream of the carbon dioxide separation stage. This is a stationary bed with a solid desiccant that can reversibly bind water. The desiccant is usually spherical and a few millimeters in size.If the desiccant is so saturated that water is no longer completely absorbed, it is regenerated. This involves drying the desiccant at high temperatures until the water is completely dissolved from the desiccant. The desiccant is then regenerated and available for repeated water absorption. Following desiccant regeneration, the dry gas stream is passed through a fixed bed of sorbent material specifically designed to bind carbon dioxide, or through structured packings capable of binding carbon dioxide. The sorbent reversibly binds carbon dioxide, and the outgoing gas stream is essentially free of carbon dioxide.

[0006] Once the sorbent has reached CO2 saturation, it is subjected to high temperatures and low pressure or vacuum until the carbon dioxide is completely released from the sorbent (desorption). The sorbent is thus regenerated and available for repeated absorption of carbon dioxide. The removed carbon dioxide is compressed and collected in a separate device, such as a gas cylinder. The desorbed carbon dioxide is highly concentrated and can be used, for example, as synthesis gas.

[0007] A disadvantage of these processes is the alternating heating and cooling processes in the stationary sorbent beds for dehumidification and regeneration, as well as for the separation and desorption of carbon dioxide. High temperatures of 100 °C to 250 °C are required for the desorption of carbon dioxide from the sorbent and the regeneration of the desiccant. This makes the desorption process very energy-intensive. Heat distribution in a stationary sorbent bed is rather poor and becomes more difficult the larger the volume of the fixed sorbent bed and the larger the diameter of the sorbent. After the desorption of carbon dioxide and the regeneration of the desiccant, the respective fixed sorbent beds must be cooled back to room temperature so that they are available again for dehumidification and separation of carbon dioxide.

[0008] One way to reduce energy consumption and improve heat distribution is to separate carbon dioxide using moving beds or fluidized beds. This means that the processes of dehumidification and regeneration, as well as the separation and desorption of carbon dioxide, are not carried out sequentially with stationary sorbent beds and alternating heating and cooling processes. Instead, the sorbents are mobile and are guided through the zones where the stationary processes of dehumidification and regeneration, and the separation and desorption of carbon dioxide, take place. The temperatures in the zones are thus kept permanently constant, and the sorbent is fed into and removed from the zones. This method of separating carbon dioxide using a moving sorbent is also called a moving bed or fluidized bed.

[0009] WO 2020 / 148460 A1 discloses a system and a method for capturing carbon dioxide from ambient air. The system comprises an at least partially air-permeable membrane containing a solid sorbent for absorbing carbon dioxide; at least one sorption chamber; at least one regeneration chamber; means for transporting the membrane from the sorption chamber to the regeneration chamber; and an inlet for absorbing air located at one end of the membrane and an outlet for discharging carbon dioxide-enriched air located at the other end of the membrane in the sorption chamber. The system is configured to allow air to flow through the membrane from the inlet to the outlet.The system further comprises means for stripping gas through the membrane into the regeneration chamber; at least one outlet for venting carbon dioxide located in the regeneration chamber; and heating means for heating the regeneration chamber.

[0010] WO 2020 / 046864 A1 describes a carbon dioxide scrubber for a building comprising an adsorption chamber through which an adsorption air stream is passed, a regeneration chamber through which a regeneration air stream is passed, and a partition wall separating the adsorption chamber from the regeneration chamber. A carbon dioxide sorbent bed extends across the adsorption chamber and the regeneration chamber. The carbon dioxide sorbent bed is configured to adsorb carbon dioxide from the adsorption air stream into the sorbent bed and to release carbon dioxide from the carbon dioxide sorbent bed into the regeneration air stream.

[0011] WO 2019 / 165151 A1 discloses a system and method for passively collecting atmospheric carbon dioxide. The system comprises a collection chamber having a first opening and a sorbent regeneration system. The system also comprises a collection body connected to and movable through a support structure. The collection body contains a sorbent material and is movable through the support structure to be in a collection configuration in which at least a portion of the collection body is in contact with a natural airflow outside the harvesting chamber such that atmospheric carbon dioxide is captured by the sorbent material, and in a release configuration in which at least a portion of the collection body containing captured carbon dioxide is processed by the regeneration system within the harvesting chamber such that captured carbon dioxide is released to form an enriched gas.

[0012] US 11,446,605 B2 discloses several processes for the direct capture of carbon dioxide and water from the atmosphere and their conversion into value-added products in an economical and carbon-negative manner. In one embodiment of the process, a portion of the water captured in a DAC process is treated, bottled, and sold as value-added drinking water, thereby offsetting the costs of the capture process. In another embodiment of the process, a portion of the captured carbon dioxide is chemically reduced, preferably using hydrogen from a photovoltaic electrolysis process, to produce methanol for use as a low-carbon fuel.

[0013] In addition, ceramic-based sorbents such as zeolites are known, particularly in spherical or pellet form, which exhibit a high carbon dioxide storage capacity. However, a disadvantage of zeolite materials is that they are unsuitable for use in a moving sorbent bed, as the movement creates friction between the zeolite spheres or pellets or a casing surrounding the zeolite spheres or pellets, which leads to severe abrasion. Therefore, zeolites have so far only been used in stationary sorbent beds.

[0014] The invention is based on the object of improving the energy efficiency of a plant for separating carbon dioxide from the ambient air and at least partially overcoming the disadvantages known from the prior art.

[0015] This object is achieved by a system for separating carbon dioxide from ambient air. The system comprises a dehumidification unit for dehumidifying a gas stream from ambient air and a carbon dioxide separation unit arranged downstream of the dehumidification unit in the flow direction of a gas stream through the system. The carbon dioxide separation unit has an adsorption chamber and a desorption chamber separate from the adsorption chamber. A sorbent is arranged in the carbon dioxide separation unit. The carbon dioxide separation unit comprises a transport means by which the sorbent can be transported from the adsorption chamber to the desorption chamber after absorbing carbon dioxide from a gas stream dried by the dehumidification unit and / or from the desorption chamber to the adsorption chamber after desorption of the carbon dioxide from the sorbent.

[0016] Ambient air is understood to mean the atmospheric air in the vicinity of the carbon dioxide separation plant. A dehumidification unit is understood to mean any part of such a plant that is suitable for reducing the humidity level and in particular the air humidity to less than 20%, preferably to less than 10%, particularly preferably to less than 5%. A carbon dioxide separation unit in this context is understood to mean a part of the plant that reduces the carbon dioxide content in the ambient air. An adsorption chamber is understood to be a process space in which carbon dioxide from the ambient air is bound in a sorbent. A desorption chamber is understood to be a process space in which the carbon dioxide bound in the sorbent is released again and the sorbent material is regenerated.

[0017] Such a system enables a process control in which a process chamber does not need to be heated and cooled alternately for adsorption and subsequent desorption, but only the sorbent needs to be transported from the adsorption chamber to the desorption chamber after the carbon dioxide has been bound. The adsorption chamber and the desorption chamber can each be kept at constant temperatures. This can massively improve the energy efficiency of the system. Furthermore, the system according to the invention enables the continuous separation of carbon dioxide directly from dry atmospheric air using fluidizing sorbent material and the continuous recovery of concentrated carbon dioxide or a carbon dioxide-enriched gas stream without causing abrasion of the sorbent material.If humid atmospheric air is present, the system according to the invention can continuously dehumidify atmospheric air by means of a fluidizing desiccant and generate a dry gas stream.

[0018] The features listed in the dependent claims enable advantageous further developments and improvements of the plant for separating carbon dioxide from the ambient air mentioned in the independent claim.

[0019] In a preferred embodiment of the invention, the dehumidification unit comprises a first chamber for drying a gas stream with a drying agent and a second chamber, different from the first chamber, for regenerating the drying agent, as well as a transport means designed to transport the drying agent from the first chamber to the second chamber and / or from the second chamber to the first chamber. A dehumidification unit comprising a first chamber for drying the air stream and a second chamber for regenerating the drying agent can increase the energy efficiency of the dehumidification system, as alternating heating and cooling of the dehumidification unit can be dispensed with. Furthermore, continuous drying of the air stream can be achieved, whereby the process can be better adapted to the continuously running process of carbon dioxide capture.In this context, a desiccant is a substance that removes moisture from the ambient air and stores it.

[0020] It is particularly preferred if the dehumidification unit comprises a first dehumidification path and a second dehumidification path different from the first dehumidification path, wherein each dehumidification path has at least one storage container for the desiccant, a dehumidification zone for absorbing moisture from the ambient air into the desiccant, a regeneration zone for regenerating the desiccant, and a collection container for receiving the regenerated desiccant. Furthermore, a transport means is provided in the dehumidification unit, with which the desiccant, after passing through one dehumidification path, can be transported into the storage container of the respective other dehumidification path. Such a dehumidification unit enables particularly efficient drying of the gas stream supplied to the carbon dioxide separation unit.

[0021] In a further preferred embodiment of the invention, a heating element for heating the desorption chamber and a vacuum source are arranged on the desorption chamber, as well as an inlet for a pressure equalization gas. A vacuum source can accelerate the desorption process and improve the expulsion of carbon dioxide from the sorbent.

[0022] According to an advantageous embodiment of the system, the sorbent is designed as a powdered zeolite and the adsorption chamber and / or the desorption chamber as a fluidized bed. Firstly, a powdered zeolite enables a particularly high reactive surface, which enables particularly efficient separation of carbon dioxide from the ambient air. Furthermore, a powdered zeolite, in particular primary zeolite crystals, prevents the sorbent from being further crushed by friction and retains its shape during the process. This prevents sorbent material from being lost or its properties from changing during the process.

[0023] In a preferred embodiment of the system, the carbon dioxide separation unit has a first carbon dioxide separation path and a second carbon dioxide separation path, wherein each carbon dioxide separation path has at least one storage container for the sorbent, a carbon dioxide absorption zone in which the sorbent binds carbon dioxide from the dried gas stream, and a desorption zone in which the carbon dioxide bound in the sorbent is released again. A carbon dioxide separation unit with two separation paths enables particularly simple and efficient separation of carbon dioxide from the ambient air. In particular, if the adsorption chamber and the desorption chamber are designed as a fluidized bed, particularly efficient separation of carbon dioxide from the ambient air and subsequent release of the carbon dioxide bound in the sorbent can be achieved.

[0024] It is particularly preferred if the carbon dioxide uptake zone is arranged geodetically higher than the desorption zone, such that the sorbent is transported from the carbon dioxide uptake zone to the desorption zone by gravity upon opening a valve, in particular a ball valve, located between the carbon dioxide uptake zone and the desorption zone. Thus, the powdered sorbent material can be transported from the adsorption chamber to the desorption chamber without additional transport or conveying means. This allows the process to be carried out even more energy-efficiently and can be easily controlled.

[0025] According to a further improvement of the system, it is advantageously provided that a transport means is provided which is designed to transport the sorbent, after it has exited the desorption zone of one carbon dioxide separation path, into the storage tank of the other carbon dioxide separation path. A transport means can easily convey a powdered sorbent material, in particular a powdered zeolite, through the carbon dioxide separation unit.

[0026] It is particularly preferred if the transport means is a pneumatic transport path with a conveying fan, a screw conveyor, or a conveyor belt. A pneumatic transport path is a particularly simple and cost-effective way to transport the sorbent material within the carbon dioxide separation unit. A screw conveyor or a conveyor belt are also suitable for transporting the sorbent material in a simple manner.

[0027] A further aspect of the invention relates to a process for separating carbon dioxide from the ambient air using a plant as described in the preceding sections, which comprises the following process steps:

[0028] Drying an air stream of ambient air by a desiccant in the dehumidification unit

[0029] Feeding the dried gas stream from the dehumidification unit into the adsorption chamber of the carbon dioxide separation unit, wherein the carbon dioxide is bound in a sorbent in the adsorption chamber, and wherein the sorbent is transported from the adsorption chamber into the desorption chamber in order to release the carbon dioxide bound in the sorbent.

[0030] Such a process enables a process control in which a process chamber does not have to be heated and cooled alternately for adsorption and subsequent desorption, but only the sorbent needs to be transported from the adsorption chamber to the desorption chamber after the carbon dioxide has been bound. The adsorption chamber and the desorption chamber can each be kept at constant temperatures. This can massively improve the energy efficiency of the plant. Furthermore, the process according to the invention enables the continuous separation of carbon dioxide directly from dry atmospheric air using fluidizing sorbent material and the continuous recovery of concentrated carbon dioxide or a carbon dioxide-enriched gas stream without generating abrasion of the sorbent material.If humid atmospheric air is present, the method according to the invention can be used to continuously dehumidify atmospheric air by means of a fluidizing desiccant and to generate a dry gas stream.

[0031] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0032] The invention is explained below in exemplary embodiments with reference to the accompanying drawings. Figure 1 shows a schematic representation of a first exemplary embodiment of a system according to the invention for separating carbon dioxide from the ambient air;

[0033] Figure 2 is a schematic representation of a dehumidification unit for such a

[0034] Attachment;

[0035] Figure 3 is a schematic representation of another system according to the invention for

[0036] Separation of carbon dioxide from the ambient air;

[0037] Figure 4 is a schematic representation of another dehumidification unit for such a system;

[0038] Figure 5 is a schematic representation of a carbon dioxide separation unit for such a plant; and

[0039] Figure 6 is a schematic representation of a preferred embodiment of a plant according to the invention for separating carbon dioxide from the ambient air.

[0040] Figure 1 shows a schematic representation of a system 10 for separating carbon dioxide from ambient air. The system 10 comprises a dehumidification unit 20 and a carbon dioxide separation unit 40 arranged downstream of the dehumidification unit 20 in the flow direction of a gas stream through the system 10. The dehumidification unit 20 is preferably designed as a dehumidification unit 20 shown in Figure 2 for the continuous or quasi-continuous drying of ambient air. Alternatively, the dehumidification unit 20 can also be designed as a discontinuously operating dehumidification unit 20, which dries a quantity of air and then feeds the dried air to the carbon dioxide separation unit 40. The dehumidification unit 20 has an inlet 12 for ambient air, an outlet 14 for a moist gas stream, and an outlet 22 for dried ambient air.The dried ambient air 22 is fed to the carbon dioxide separation unit 40. In the dehumidification unit 20, water is separated from the ambient air using a desiccant 28, creating a dry gas stream. Silica gel, for example, can be used as the desiccant 28. Alternatively, other desiccant 28 are also conceivable that are suitable for use in a fluidized process, are essentially abrasion-resistant, and absorb moisture from the ambient air.

[0041] The separation of carbon dioxide from the ambient air takes place in a carbon dioxide separation unit 40. The carbon dioxide separation unit 40 comprises an adsorption chamber 42 and a desorption chamber 44. To separate carbon dioxide from the ambient air, the dry gas stream from the dehumidification unit 20 is passed through an inlet 46 into an adsorption chamber 42 of the carbon dioxide separation unit 40. Located in the adsorption chamber 42 is a sorbent 58 that physically and / or chemically separates carbon dioxide from the dry gas stream. A zeolite 60, particularly in the form of zeolite primary crystals, is preferably used as the sorbent 58 for separating carbon dioxide from the ambient air. The sorbent 58 is therefore in powder form and can be stored, in particular, in a container 56. The size of the zeolite primary crystals is in the nm to pm range, preferably in the range of 100 nm to 100 pm.Separation occurs by adsorbing carbon dioxide onto sorbent 58. Dehumidification of the atmospheric air as a precursor to carbon dioxide separation is mandatory for zeolite 60 if the ambient air contains moisture. In most cases, it can be assumed that the ambient air contains a certain percentage of water. Due to the pronounced hydrophilicity of zeolite 60, the ambient air must be dehumidified before carbon dioxide separation. Otherwise, zeolite 60 will primarily bind water molecules instead of carbon dioxide.

[0042] The adsorption chamber 42 has an outlet 18 for substantially carbon dioxide-free air. The adsorption chamber 42 can also be connected to a cooling device, in particular a heat exchanger, to cool the heated sorbent material 58 and feed the heat 38 back into the system 10 as process heat at a suitable location for separating carbon dioxide from the ambient air.

[0043] After absorbing carbon dioxide, the sorbent material 58 is transported from the adsorption chamber 42 to the desorption chamber 44 by a transport device 54. The desorption chamber 44 has a vacuum source 50, with which the pressure in the desorption chamber 44 can be reduced compared to the ambient pressure. The vacuum source is preferably designed as a vacuum pump 97, 117 or as a vacuum pump. Furthermore, a heating element 52 is arranged on the desorption chamber 44, with which heat 38 can be supplied to the desorption chamber 44 in order to heat the desorption chamber 44 to a temperature of 100°C to 250°C. At the temperature of 100°C to 250°C and the vacuum, the carbon dioxide desorbs from the sorbent 58 and can be discharged from the desorption chamber 44 via an outlet 16.Furthermore, the desorption chamber 44 has an inlet 48 for a pressure equalization gas to raise the pressure level back to ambient pressure after a corresponding evacuation. Following the desorption process, the sorbent material 58, freed of carbon dioxide, is transported by the transport device 54 from the desorption chamber 44 to the adsorption chamber 42, where it is again available for binding carbon dioxide.

[0044] The process of separating carbon dioxide from the ambient air takes place continuously or quasi-continuously, with the sorbent material being in continuous circulation between the adsorption chamber 42 and the desorption chamber 44.

[0045] Figure 2 schematically shows a preferred dehumidification unit 20 for such a system 10 for separating carbon dioxide from the ambient air. The ambient air is dehumidified using a desiccant 28 in a first chamber 24 of the dehumidification unit 20. For this purpose, the ambient air is fed through the inlet 12 into the first chamber 24, where the desiccant 28 absorbs and binds the moisture from the ambient air. The dried ambient air is discharged from the first chamber 24 at an outlet 22 and fed to the carbon dioxide separation unit 40. Once the desiccant 28 is saturated with water, the water-rich desiccant 28 is transported to a second chamber 26 of the dehumidification unit 20 and regenerated there. In the regeneration process step, water is separated from the desiccant again using a purge gas and high temperature.For this purpose, an inlet 32 ​​for a purge gas is provided on the second chamber 26. Dry compressed air or nitrogen, for example, can be used as the purge gas. An outlet 14 for a moist gas stream 14 is provided on the second chamber 26 in order to discharge the moisture released from the drying agent 28. The second chamber 26 is heated by a heating element 30, wherein the temperature in the second chamber 26 is preferably constant in the range of 100°C to 150°C and heat 38 is preferably continuously supplied to the second chamber 26. Once the drying agent 28 has been sufficiently freed of water, the now anhydrous drying agent 28 is transported by a transport means 34 back to the first chamber 24, where it can be used again to dehumidify atmospheric air.The special feature of this design is that the operating conditions in the chambers 24, 26, in particular the temperature in the second chamber 26, remain constant for regenerating the desiccant 28, while the desiccant 28 is transported back and forth between the chambers 24, 26. This saves the energy required to heat and cool the corresponding metallic system containers of the chambers 24, 26. The desiccant 28 can be stored, in particular, in containers 36 and / or transported through the dehumidification unit 20.

[0046] Figure 3 schematically shows a system 10 for separating carbon dioxide, comprising the dehumidification unit 20 shown in Figure 2 and the carbon dioxide separation unit 40 shown in Figure 1. This essentially depicts a process for separating carbon dioxide from dehumidified ambient air. The carbon dioxide is separated using the sorbent 58 in an adsorption chamber 42 of the carbon dioxide separation unit 40. For this purpose, the dry gas stream emerging from the dehumidification unit 20 is fed into the adsorption chamber 42, where the sorbent 58 binds the carbon dioxide. Once the sorbent 58 is saturated with carbon dioxide, this carbon dioxide-rich sorbent 58 is transported to the desorption chamber 44, where it is desorbed from the carbon dioxide. Desorption can occur in two ways.One variant is that carbon dioxide is separated from the sorbent 58 in the desorption chamber 44 by means of negative pressure <100 kPa or vacuum and high temperature. The temperature in the desorption chamber 44 is 100 °C to 250 °C. To restore the ambient pressure following the desorption process, a pressure equalization gas, for example dry compressed air or nitrogen, is used. The carbon dioxide separated from the sorbent 58 is discharged from the desorption chamber 44 and is present in concentrated form. Another variant of the desorption process is that carbon dioxide is separated from the sorbent 58 by means of purge gas and high temperature of 100 °C to 250 °C. The purge gas, in particular dry compressed air or nitrogen, is simultaneously the fluidization medium that transports the sorbent 58 through the carbon dioxide separation unit 40.The carbon dioxide separated from the sorbent 58 is passed out of the desorption chamber 44 together with the purge gas and is present in an enriched form in the gas stream.

[0047] Once the sorbent 58 has been completely freed of carbon dioxide, the now carbon dioxide-free sorbent 58 is transported back to the adsorption chamber 42, where it can be used to again separate carbon dioxide from the dehumidified atmospheric air. The special feature of this design is that the operating conditions in the chambers 42, 44, in particular the temperature in the desorption chamber 44, remain essentially constant while the sorbent 58 is transported back and forth between the chambers 42, 44. This saves the energy required to heat and cool the corresponding metallic plant vessels of the adsorption chamber 42 and the desorption chamber 44, respectively. Figure 4 shows the structure of a dehumidification unit 20 for the continuous dehumidification of the ambient air with two dehumidification paths 70, 80. In the first dehumidification path 70, the desiccant 28 is present in a storage container 71.Silica gel, for example, can be used as the drying agent 28. Via a valve 66, in particular a ball valve, at the bottom of the storage container 71, the drying agent 28 trickles into a dehumidification zone 72 for dehumidifying the ambient air. Ambient air flows into this dehumidification zone 72 via an inlet 12 via a fan 62. The inflowing air causes the drying agent 28 to swirl (fluidize). The dehumidification zone 72 corresponds to a first chamber 24 in Figure 2 or 3 and is preferably designed as a fluidized bed. The particle composition (size, porosity, density) of the drying agent 28 must be suitable for fluidizing the drying agent 28. The drying agent 28 should also be abrasion-resistant. An inlet 12 for ambient air and an outlet 22 for a dried gas stream are provided at the dehumidification zone 72.

[0048] The flow of the incoming ambient air should be regulated so that the desiccant 28 can fluidize. If the desiccant 28 is saturated with water, the valve 66, in particular a ball valve, at the bottom of the dehumidification zone 72 is opened and the water-rich desiccant 28 trickles into a second chamber 26, which represents a regeneration zone 73 for the desiccant 28. In the regeneration zone 73, water is separated again from the desiccant 28. The separation of water from the desiccant 28 takes place at an elevated temperature. The regeneration zone is heated for this purpose by a temperature control unit 74. The temperature in the second chamber 26 for regeneration is 100°C to 150°C. In addition, preferably heated purge gas 64 is introduced into the second chamber 26, thereby fluidizing the desiccant 28. The purge gas can be, for example, nitrogen or compressed air.The second chamber 26 for removing water from the desiccant 28 is preferably also a fluidized bed. Once the desiccant 28 has been completely freed of water, a valve 66 at the bottom of the second chamber 26 is opened, and this now low-water desiccant 28 trickles into a first collection container 75. The regenerated, low-water desiccant 28 is fed to the second dehumidification path 80 of the dehumidification unit 20 via a transport path 76, which is particularly designed as a pneumatic transport path 76, a screw conveyor, or a conveyor belt.

[0049] The second dehumidification path 80 is constructed like the first dehumidification path 70 and comprises a storage container 81, a dehumidification zone 82, a regeneration zone 83, a temperature control unit 84 and a collection container 85. Furthermore, a transport path 86 is provided, with which the drying agent 28 is fed back into the first dehumidification path 70 after passing through the second dehumidification path 80.

[0050] There, it is used to dehumidify ambient air again. Ideally, the process times for dehumidifying the ambient air and regenerating the desiccant 28 in both paths 70, 80 are set so that atmospheric air is continuously dehumidified and a dry gas stream is generated.

[0051] Figure 5 shows a schematic representation of a carbon dioxide separation unit 40 for such a system 10 for separating carbon dioxide from the ambient air. The carbon dioxide separation unit 40 has a first carbon dioxide separation path 90 and a second carbon dioxide separation path 110. In the first carbon dioxide separation path 90, the sorbent 58 is present in the storage container 91. Powdered zeolite is used as the sorbent 58. Via a valve 66, in particular a ball valve, at the bottom of the storage container 91, the sorbent 58 trickles into an adsorption chamber 42, which forms a carbon dioxide absorption zone 92. Therein, the carbon dioxide is separated from the dried gas stream from the dehumidification unit 20 and stored in the sorbent. The dried air flows into this adsorption chamber 42 via a fan 68.The supplied dry air stream simultaneously serves as the fluidization medium, causing the powdered sorbent 58 to swirl (fluidize). The absorption chamber 42 is designed as a fluidized bed. The particle composition (size, porosity, density) of the sorbent 58 must be suitable for fluidizing the sorbent 58. The sorbent 58 must also be essentially abrasion-resistant. The flow of the incoming dry air is regulated so that the sorbent 58 can fluidize. Once the sorbent 58 is saturated with carbon dioxide, a valve 66 at the bottom of the adsorption chamber 42 is opened, and the carbon dioxide-rich sorbent 58 trickles into a desorption chamber 44, which forms a desorption zone 93. In the desorption zone 93, the carbon dioxide is separated again from the sorbent 58. The separation of carbon dioxide from the sorbent 58 takes place at elevated temperature.For this purpose, the desorption zone 93 is heated by a temperature control unit 94. The temperature in the desorption zone is between 100°C and 250°C. To assist desorption, a vacuum of preferably <100 kPa is generated in the desorption zone 93 by means of a vacuum pump 97. To restore atmospheric pressure, a pressure equalization gas is introduced into the desorption chamber 44. The pressure equalization gas can be nitrogen gas or compressed air. The desorption chamber 44 is designed as a fluidized bed. The carbon dioxide separated by the sorbent 58 is concentrated in this design and is passed out of the desorption zone 93 through an outlet 16, compressed by a compressor 119 shown in Figure 6, and collected in a collecting device 98.Once the sorbent 58 has been completely freed of carbon dioxide, a valve 66 at the bottom of the desorption chamber 44 is opened, and this now carbon dioxide-free sorbent 58 trickles into a collection container 95. The carbon dioxide-free sorbent 58 is fed to the second carbon dioxide separation path 110 via a transport path 96, in particular via a pneumatic transport path, a screw conveyor, or a conveyor belt. There, it is used to again separate carbon dioxide from the dry gas stream. Ideally, the process times for the separation of carbon dioxide and the desorption of carbon dioxide in both paths 90, 100 are set such that carbon dioxide is continuously separated from the dry gas stream and concentrated carbon dioxide is produced.

[0052] The second carbon dioxide separation path 110 is preferably constructed identically to the first carbon dioxide separation path 90 and comprises a storage tank 111, a carbon dioxide receiving zone 112, a desorption zone 113, a temperature control unit 114 for the desorption zone, a collection tank 115, a vacuum pump 117, and a carbon dioxide collecting device 118. Furthermore, a transport path 116 is provided, which connects the collection tank 115 of the second carbon dioxide separation path 110 to the storage tank 91 of the first carbon dioxide separation path 90.

[0053] Figure 6 shows a schematic representation of a system 10 for separating carbon dioxide from the ambient air, comprising a dehumidification unit 20 with a first dehumidification path 70 and a second dehumidification path 80, as well as a carbon dioxide separation unit 40 with a first carbon dioxide separation path 90 and a second carbon dioxide separation path 110. The system 10 further comprises a control unit 100 with a memory unit 102 and a computing unit 104, as well as a computer program code 106 stored in the memory unit 106. When the computer program code 106 is executed by the computing unit 104, a method according to the invention for separating carbon dioxide from the ambient air is carried out.

[0054] In contrast to known solutions, where the sorbent 58 is macroscopically present in spherical or granular form, powdered sorbent material 58 is used in the present invention. Ceramic-based sorbents 58, more specifically primary zeolite crystals, are preferably used that are not embedded in a matrix. The size of the zeolite crystals is in the nm to pm range, preferably 100 nm to 100 pm. The advantage of powdered zeolite 60 is its mechanical stability due to the primary particle size in the nm to pm range. It can be assumed that very small primary particles (diameter 100 nm to 100 pm) do not exhibit any abrasion during fluidization. Experience from the surface coating of silicon oxide, graphite, and transition metal oxide particles (diameter 0.5 - 50 pm) using fluidized bed reactors confirms this assumption.

[0055] The powdered sorbent 58 has the advantage over spherical or pellet-shaped sorbents of rapidly absorbing and releasing carbon dioxide, which significantly shortens the process step of separating carbon dioxide from the ambient air. The heat released during the absorption of carbon dioxide can be quickly dissipated due to the excellent heat distribution of fluidizing powdered material. Dry compressed air or nitrogen can be used as the fluidization medium and pressure equalization gas. The carbon dioxide desorption process can be assisted by applying a negative pressure or vacuum. The fluidization of the powdered sorbent 58 can occur at any pressure below 100 kPa, as long as the pressure drop across the sorbent bed is sufficient to maintain the fluidization of the sorbent 58.

[0056] List of reference symbols

[0057] 10 Plant for the separation of carbon dioxide from the ambient air

[0058] 12 Inlet for ambient air

[0059] 14 Outlet for moist gas flow

[0060] 16 Carbon dioxide outlet

[0061] 18 Outlet for carbon dioxide-reduced ambient air

[0062] 20 dehumidification unit

[0063] 22 Outlet for dried gas stream

[0064] 24 first chamber

[0065] 26 second chamber

[0066] 28 Desiccants

[0067] 30 heating element

[0068] 32 Purge gas inlet

[0069] 34 means of transport

[0070] 36 containers

[0071] 38 Heat

[0072] 40 Carbon dioxide separation unit

[0073] 42 Adsorption chamber

[0074] 44 Desorption chamber

[0075] 46 Inlet for dried gas stream

[0076] 48 Inlet pressure equalization gas

[0077] 50 vacuum source

[0078] 52 Heating element

[0079] 54 means of transport

[0080] 56 containers

[0081] 58 Sorbent / Sorbent material 60 Zeolite

[0082] 62 blowers

[0083] 64 heated purge gas

[0084] 66 Valve

[0085] 68 blower dried gas stream

[0086] 70 first dehumidification path

[0087] 71 storage tanks

[0088] 72 first dehumidification zone

[0089] 73 first regeneration zone

[0090] 74 Tempering unit first regeneration zone

[0091] 75 first collection container

[0092] 76 first pneumatic transport path

[0093] 80 second dehumidification path

[0094] 81 storage tanks

[0095] 82 second dehumidification zone

[0096] 83 second regeneration zone

[0097] 84 Tempering unit second regeneration zone

[0098] 85 second collection container

[0099] 86 second pneumatic transport path

[0100] 90 first carbon dioxide capture pathway

[0101] 91 storage tank

[0102] 92 first carbon dioxide absorption zone

[0103] 93 first desorption zone

[0104] 94 Tempering first desorption zone

[0105] 95 first collection container

[0106] 96 first pneumatic transport path

[0107] 97 first vacuum pump

[0108] 98 first carbon dioxide capture device

[0109] 100 control unit

[0110] 102 storage unit

[0111] 104 computing unit

[0112] 106 Computer program code 110 second carbon dioxide separation pathway

[0113] 111 Storage tank

[0114] 112 second carbon dioxide absorption zone

[0115] 113 second desorption zone 114 temperature control second desorption zone

[0116] 115 second collection container

[0117] 116 second pneumatic transport path

[0118] 117 second vacuum pump

[0119] 118 second carbon dioxide collection device 119 compressor

Claims

Patent claims 1. Plant (10) for separating carbon dioxide from the ambient air, comprising a dehumidification unit (20) for dehumidifying a gas stream and a carbon dioxide separation unit (40) arranged downstream of the dehumidification unit (20) in the flow direction of a gas stream through the plant (10), wherein the carbon dioxide separation unit (40) has an adsorption chamber (42) and a desorption chamber (44) different from the adsorption chamber (42), wherein a sorbent (58) is arranged in the carbon dioxide separation unit (40), and wherein the carbon dioxide separation unit (40) comprises a transport means (54) with which the sorbent (58) is transported from the adsorption chamber (42) into the desorption chamber (44) after absorption of carbon dioxide from a gas stream dried by the dehumidification unit (20) and / or after desorption of the carbon dioxide from the sorbent (58) can be transported from the desorption chamber (44) into the adsorption chamber (42).

2. Plant (10) for separating carbon dioxide from the ambient air according to claim 1, wherein the dehumidification unit (20) has a first chamber (24) for drying a gas stream with a drying agent (28) and a second chamber (26) different from the first chamber (24) for regenerating the drying agent (28), as well as with a transport means (34) which is designed to transport the drying agent (28) from the first chamber (24) into the second chamber (26) and / or from the second chamber (26) into the first chamber (24).

3. Plant (10) for separating carbon dioxide according to claim 2, wherein the dehumidification unit (20) comprises a first dehumidification path (70) and a second dehumidification path (80), wherein each dehumidification path (70) has at least one storage container (71, 81) for the drying agent (28), a dehumidification zone (72, 82) for absorbing moisture from the ambient air in the drying agent (28), a regeneration zone (73, 83) for regenerating the drying agent (28) and a collection container (75, 85) for receiving the regenerated drying agent, and wherein a transport means (34) is provided with which the drying agent (28) can be transported into the storage container (71, 81) of the respective other dehumidification path (70, 80) after passing through one dehumidification path (70, 80).

4. Plant (10) for separating carbon dioxide from the ambient air according to one of claims 1 to 3, wherein a heating element (52) for heating the desorption chamber (44) and a negative pressure source (50) are arranged on the desorption chamber (44) and an inlet (48) for a pressure equalization gas is formed.

5. Plant (10) for separating carbon dioxide according to one of claims 1 to 4, wherein the sorbent (58) is designed as a powdered zeolite (60) and the adsorption chamber (42) and / or the desorption chamber (44) is designed as a fluidized bed.

6. Plant (10) for separating carbon dioxide from the ambient air according to one of claims 1 to 5, wherein the carbon dioxide separation unit (40) has a first carbon dioxide separation path (90) and a second carbon dioxide separation path (110), wherein each carbon dioxide separation path (90, 110) has at least one storage container (91, 111) for the sorbent (58), a carbon dioxide absorption zone (92, 112) in which the sorbent (58) binds carbon dioxide from the dried gas stream, and a desorption zone (93, 113) in which the carbon dioxide bound in the sorbent (58) is released again.

7. Plant (10) for separating carbon dioxide from the ambient air according to claim 6, wherein the carbon dioxide absorption zone (92, 112) is arranged geodetically higher than the desorption zone (93, 113) such that the sorbent (58) is transported by gravity from the carbon dioxide absorption zone (92, 112) into the desorption zone (93, 113) upon opening of a valve (66) arranged between the carbon dioxide absorption zone (92, 112) and the desorption zone (93, 113).

8. Plant (10) for separating carbon dioxide from the ambient air according to claim 6 or 7, further comprising a transport means (54) which is designed to transport the sorbent (58) after exiting the desorption zone (93, 113) of one carbon dioxide separation path (90, 110) into the storage container (91, 111) of the respective other carbon dioxide separation path (90, 110).

9. Plant (10) for separating carbon dioxide from the ambient air according to claim 8, wherein the transport means (54) is a pneumatic transport path (86, 116) with a conveying fan (62), a conveyor screw or a conveyor belt.

10. Process for separating carbon dioxide from the ambient air using a system (10) according to one of claims 1 to 9, comprising the following steps: Drying an air stream of ambient air by a drying agent (28) in the dehumidification unit (20), Feeding a dried gas stream from the dehumidification unit (20) into the adsorption chamber (42) of the carbon dioxide separation unit (40), wherein the carbon dioxide is bound in a sorbent (58) in the adsorption chamber (42), and wherein the sorbent (58) is transported from the adsorption chamber (42) into a desorption chamber (44) in order to release the carbon dioxide bound in the sorbent (58).

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