Air treatment device and system and method of using the same

Abstract

The present invention describes a method of direct air capture of carbon dioxide (DAC integrated with an external source providing waste heat through a hot fluid, as well as a DAC unit and system for use in the method. The integration of the DAC method, unit, and system with an external source providing a hot fluid, lowers the energy demands of the DAC method and makes this an energy-efficient and environmentally friendly way of capturing carbon dioxide from ambient air or from streams having higher concentration of carbon dioxide than in ambient air. The method also involves circulating the the hot fluid back to the external source as a cooling liquid. Water captured from air in the form of humidity may also be circulated to the external source as make-up water.

Description

[0001] AIR TREATMENT DEVICE AND SYSTEM AND METHOD OF USING THE SAME

[0002] TECHNICAL FIELD

[0003] The present invention describes a method of direct air capture of carbon dioxide (DAC integrated with an external source providing waste heat through a hot fluid, as well as a DAC unit and system for use in the method.

[0004] BACKGROUND OF THE INVENTION

[0005] Direct air capture (DAC), which removes carbon dioxide directly from ambient air, is a critical negative emission technology for mitigating global climate change. Efficiency and the source of energy are crucial considerations for DAC to enable negative emissions. Substantial technological progress has been made in DAC technologies, and promising opportunities exist for commercial-scale deployments. However, DAC technologies require high regeneration energy to release carbon dioxide from sorbents. Various approaches have been tested and optimized for different DAC systems. The work equivalent regeneration energy demand (supported by either the electric grid or fossil fuel combustion) ranges from 0.5- 18.75 GJ / t-carbon dioxide for solid sorbent DAC systems and 0.62-17.28 GJ / t-carbon dioxide for liquid solvent DAC systems. The regeneration process is the energy-demanding process in DAC that is a key step for efficient operation. Potential methods to lower the regeneration energy demand include using waste heat from different processes, microwave, ultrasound, magnetic particle heating, and electric swing.

[0006] Another issue of sorbent material DACs is how to replace degraded sorbent in an uncomplicated way.

[0007] The present invention provides solutions to these problems.

[0008] SUMMARY OF THE INVENTION

[0009] The present invention describes a method of direct air capture of carbon dioxide (DAC) integrated with an external source providing waste heat through a hot fluid, as well as a DAC unit and system for use in the method.

[0010] The integration of the DAC method, unit, and system with an external source providing a hot fluid, lowers the energy demands of the DAC method and makes this an energy-efficient and environmentally friendly way of capturing carbon dioxide from ambient air or from streams having higher concentration of carbon dioxide than in ambient air. The integration with the external source may be at least a two-way integration as the hot fluid may be recirculated to the external source, thus reducing the energy-demands of the operation of the external source. Products of the DAC method are thus carbon dioxide gas, water, and cooling fluid, which may be forwarded to external sources and / or be used in the DAC method and products as heating or cooling fluid, water supply, carrier gas, etc.

[0011] The present method and products may be integrated with more or less any external industrial process generating waste heat in the form of hot fluids and thus having the need of a cooling step.

[0012] Embodiments of the invention are associated with various advantages and / or technical effects.

[0013] The DAC unit and its cassette design, in combination with the DAC system container construction, provide easy handling of sorbent replacement if the sorbent degrades. According to a first aspect of the invention, there is provided a method of direct air capture of carbon dioxide using waste heat from a fluid from an external source comprising the steps of a) blowing ambient air comprising carbon dioxide through a direct air capture of carbon dioxide DAC unit comprising a sorbent material capable of selectively adsorbing carbon dioxide and water vapour and contacting said air with the sorbent material during an adsorption step to adsorb carbon dioxide and optionally water vapour; optionally, purging the DAC unit by applying vacuum, e.g., at 0.15-1 atm; b) releasing carbon dioxide and water vapour from the sorbent material by transferring heat from the external hot fluid to the sorbent material during a desorption phase, while applying vacuum, and wherein said hot fluid is not in direct contact with the sorbent material, c) separating the carbon dioxide into a carbon dioxide stream, and optionally condensing any water vapour into water and separating the water as a liquid water stream; optionally, cooling the sorbent material using a cooling fluid; and d) recirculating the initially hot fluid to the external source, as a cooled fluid.

[0014] Utilizing waste heat from an external hot fluid source for the desorption phase enhances the energy efficiency of the direct air capture process by repurposing thermal energy that would otherwise be lost to the environment or would have to be generated or converted from other sources.

[0015] The optional application of vacuum during the purging and desorption step of the DAC unit can improve the efficiency of the sorbent material regeneration by facilitating the release of adsorbed carbon dioxide and water vapor, thereby readying the sorbent for subsequent adsorption cycles. The separation of carbon dioxide into a distinct stream, with the optional condensation of water vapor, allows for the capture of high-purity carbon dioxide, which can be beneficial for storage or utilization in various industrial applications.

[0016] The method provides the advantage of efficient carbon dioxide capture from ambient air using waste heat, enhancing the overall sustainability of the process.

[0017] The DAC unit provides the advantage of effective fluid management, allowing for the seamless integration of hot fluids from various external sources.

[0018] The system provides the advantage of improved thermal conductivity through the use of highly conductive materials, optimizing the heat transfer during the desorption phase.

[0019] The method provides the advantage of manufacturable components, enabling easier production and scalability of the DAC units for widespread application.

[0020] The DAC system provides the advantage of liquid water recovery, allowing for the efficient handling and utilization of condensed water vapour during the carbon dioxide capture process.

[0021] In an embodiment of the method, the heat-transfer in step b) is achieved through a highly thermally conducting metal or metal alloy barrier between the hot fluid and the sorbent material. The use of a highly thermally conducting metal or metal alloy barrier ensures efficient heat transfer from the hot fluid to the sorbent material, which can lead to a more rapid and complete desorption of carbon dioxide. The presence of a thermal barrier between the hot fluid and the sorbent material prevents contamination and degradation of the sorbent by the fluid, thereby maintaining the integrity and effectiveness of the sorbent over multiple adsorption-desorption cycles. In an embodiment, the method further comprises a metal barrier material being selected from copper, aluminium, stainless steel, and alloys having high thermal conductivity. Selecting a metal barrier material from copper, aluminium, stainless steel, or high thermal conductivity alloys provides a tailored approach to optimizing heat transfer rates, which can be matched to the specific thermal properties of the sorbent material used. The use of these specific metals and alloys for the barrier material can also contribute to the overall durability and corrosion resistance of the system, ensuring long-term operational stability.

[0022] In step b), the temperature of the external hot fluid may vary but could typically be 30 to 200 °C, such as 30-99 °C, when received from the external source. Specifying the temperature of the external hot fluid ensures that the heat provided is sufficient for the desorption of carbon dioxide without the need for additional heating, thus conserving energy and reducing operational costs. The heat from the external waste heat sources can be directly used or a heat pump can be used to raise the temperature of the heating fluid before it used in the DAC system in the desorption step. Operating at the specified temperature range can prevent thermal degradation of the sorbent material, thereby extending its lifespan and reducing the frequency of sorbent replacement. Setting the temperature of the external hot fluid to a maximum of 99 °C aligns with the typical waste heat temperatures available from industrial processes, allowing for seamless integration of the DAC system into existing facilities without the need for substantial modifications. The use of a sub-boiling temperature for the hot fluid minimizes the risk of degrading the sorbent material.

[0023] In an embodiment, the sorbent material is arranged in the form of a fixed bed. Utilizing a fixed bed of sorbent material enhances the contact efficiency between the sorbent and the substance to be absorbed or reacted with, leading to improved mass transfer rates. The fixed bed configuration allows for a more uniform flow distribution, reducing channelling and dead zones, which can improve the overall performance and predictability of the process.

[0024] In a further embodiment, the particle size of said sorbent material is more than 0.2 mm and up to 2 mm, the sphericity of the particles may range between 0-1, bed voidage is preferably more than 0.4, and the thermal conductivity is more than 0.16 W / mK. A particle size range of more than 0.2 mm and up to 2 mm optimizes the balance between surface area for adsorption and minimal pressure drop across the sorbent material, leading to efficient operation. Specifying a sphericity range for the particles ensures that the flow dynamics within the bed are maintained, which can enhance the mass transfer and reduce attrition of the sorbent material. A bed voidage of more than 0.4 promotes good gas or liquid flow through the bed, while a thermal conductivity of more than 0.16 W / mK ensures effective heat transfer.

[0025] The sorbent material may be selected from amines impregnated on a support material, or weak ionic resins or metal organic frameworks (MOFs). In an embodiment, the support material is selected from silica granules, silica gel, alumina, cellulose, and metal-organic framework materials, organic materials, or any mixture of said support materials. Selecting from a range of support materials such as silica granules, silica gel, alumina, cellulose, and metal-organic frameworks allows for customization of the sorbent properties, including pore size distribution and mechanical strength, to suit different applications. The use of organic materials or mixtures of support materials can provide additional functionality, such as enhanced adsorption capacity or selectivity, due to synergistic effects between the components. In a further embodiment, the sorbent material is mixed with highly thermally conducting material. Mixing the sorbent material with highly thermally conducting material improves heat distribution within the sorbent material, which can be critical for maintaining optimal operating temperatures and enhancing reaction kinetics. The presence of a thermally conductive material can also mitigate the effects of hotspots or temperature gradients that could otherwise lead to decreased sorbent efficiency or degradation.

[0026] In an embodiment, the inlet of ambient air in step a) is stopped when the sorbent material is at least 70% saturated as determined by continuously monitoring the carbon dioxide concentration in the exhaust air leaving the DAC chamber. By halting the intake of ambient air when the sorbent material reaches at least 70% saturation, the efficiency of the DAC process is optimized, ensuring that the sorbent capacity is maximally utilized without overloading the system, which could lead to diminished carbon capture performance or unnecessary energy expenditure. Continuous monitoring of carbon dioxide concentration in the exhaust air allows for precise control of the sorbent saturation process, leading to improved operational control and predictability of the DAC system's performance, which can enhance the overall reliability and maintenance scheduling, as well as avoiding unnecessary energy expenditure.

[0027] The hot fluid emanates from and is circulated back to as cooling fluid to an external source selected from an electrolyzer, a heat pump, a nuclear plant, a transformer, solar panels, a district heating network, a HVAC system, a data centre, an inter-stage cooling system in compressors, steam cycles, and waste heat generated from industrial processes. Utilizing hot fluid from external sources such as electrolysers or heat pumps for cooling purposes creates an integrated energy system that can reduce the overall energy consumption of the DAC process, leading to a more sustainable and cost-effective operation. When the external source is an electrolyzer, the hot fluid used from the electrolyzer may be an electrolyte or cooling fluid. The ability to circulate hot fluid back to various external sources for cooling purposes enables the recovery and reuse of waste heat, which can improve the energy efficiency of those external systems and contribute to a reduction in the environmental impact of both the DAC process and the external systems.

[0028] In one embodiment, in step b) water or water vapour is sprinkled / sprayed on the sorbent material, or carbon dioxide or hydrogen gas is passed through the DAC chamber to increase the speed of the carbon dioxide release. Sprinkling or spraying water or water vapour onto the sorbent material can accelerate the desorption of carbon dioxide, thereby reducing the time required for regeneration of the sorbent and increasing the throughput of the DAC system. Passing carbon dioxide or hydrogen gas through the DAC chamber during the release phase can increase the speed of the carbon dioxide release.

[0029] In a further embodiment, in step a) the ambient air is heated before being blown into the DAC unit. Preheating the ambient air before it enters the DAC unit can improve the sorption kinetics, leading to a more efficient capture of carbon dioxide from the air, especially in colder climates or during periods of lower ambient temperatures. Heating the ambient air can also reduce the relative humidity within the DAC chamber, which can prevent potential water-related issues such as sorbent material degradation or clumping, thereby extending the operational lifespan of the sorbent.

[0030] The condensed water generated during the DAC process may beneficially be feed to the external source, such as an electrolyser, for use in its process. Feeding the condensed water back to the external source can contribute to a closed-loop system that minimizes water waste and reduces the need for additional water resources (an electrolyser may for example use 9 litres of water to produce 1 kilogram of hydrogen via electrolysis), which is particularly advantageous in water-scarce regions. The reuse of condensed water in external systems can also lower the thermal load on those systems, potentially enhancing their efficiency and reducing the need for further cooling, which can lead to energy savings and a decrease in operational costs.

[0031] According to a second aspect of the invention, there is provided a DAC unit or cassette comprising a housing with a chamber, at least an air inlet and at least an air outlet leading carbon dioxide depleted air out of the chamber, an internal perforated floor or mesh and at least a set of metal barriers adapted to accommodate a sorbent material and a hollow metal heat-exchanger device, and the perforated floor retains the sorbent material but allows air led into the sorbent material to pass through, and a fluid inlet header and a fluid inlet piping leading hot fluid to the heat-exchanger device, and a fluid outlet header and a fluid outlet piping leading hot fluid from the heat-exchanger device, and wherein, when ambient air comprising carbon dioxide is led into the chamber through the sorbent material, the perforated floor, and out through the air outlet, carbon dioxide and water vapour (in the form of humidity in air) may be collected by the sorbent material during an adsorption step and released during a desorption step. The integration of a hollow metal heat-exchanger device within the DAC unit allows for efficient utilization of waste heat from an external source and heat-transfer, enhancing the energy efficiency of the carbon capture process. The perforated floor or mesh design ensures uniform distribution of air through the sorbent material, leading to improved contact between the air and sorbent for more effective carbon dioxide adsorption. The configuration of metal barriers adapted to accommodate the sorbent material provides structural support and optimizes the flow path of air, thereby maximizing the exposure of carbon dioxide to the sorbent. This DAC cassette configuration also enables easy monitoring and replacement of degraded sorbent material in the cassette by removal of the cassette from its container, exchange of sorbent materials, and replacement of the cassette in the container. The cassette design also enables easy stacking and scaling of the system size.

[0032] In one embodiment, the metal barriers and hollow metal heat-exchanger device are integrated as hollow heat-exchanger plates. The integration of metal barriers and the hollow heat-exchanger device as hollow heat-exchanger plates simplifies the design, reducing manufacturing complexity and potentially lowering production costs. The hollow heatexchanger plates serve a dual function as both structural components and heat transfer elements, which can lead to a more compact and efficient DAC unit design. The use of hollow heat-exchanger plates can improve the thermal conductivity within the sorbent material, resulting in a more uniform temperature distribution during the desorption step and enhancing the release of captured carbon dioxide. In a further embodiment, the hollow metal heat-exchanger device is in the form of hollow metal pipes. The use of hollow metal pipes as the heat-exchanger device allows for easy scalability of the system, as pipes can be readily configured in various lengths and arrangements to suit different DAC unit sizes. Hollow metal pipes provide a high surface area for heat exchange, which can improve the transfer of waste heat to the sorbent material, leading to more efficient desorption of carbon dioxide. The form factor of hollow metal pipes can facilitate maintenance and replacement, as individual pipes can be accessed and serviced without disrupting the entire heat-exchanger system.

[0033] The DAC unit is stackable on top of at least another DAC unit. The stackable design of the DAC units enables vertical integration, saving valuable floor space and allowing for the creation of larger carbon capture installations in confined areas. Stackability enhances the modularity of the system, permitting incremental expansion of carbon capture capacity by adding more units without the need for extensive redesign. The ability to stack DAC units on top of one another can lead to reduced infrastructure costs, as the same foundation and support structures can be used to support multiple units. If the sorbent material degrades, it can be easily replaced as the cassette design of the DAC units make the removal and replacement of the DAC unit easy.

[0034] Other advantages of the DAC unit design are that it features lower pressure drops, and that it is easy to manufacture. According to a third aspect of the invention, there is provided a DAC system capable of using waste heat from a fluid from an external source comprising at least one DAC unit, a container for enclosing the DAC units, an air ventilation unit for providing air to the DAC unit, a hot fluid feeding unit for providing the DAC unit with hot fluid, a vacuum pump, a post-processing unit for handling a stream of carbon dioxide, and optionally water vapour, a recirculation unit for circulating an initially hot fluid back to the external source as a cooled fluid. When ambient air comprising carbon dioxide is led into the DAC by the air ventilation unit, said carbon dioxide and water vapour is collected by the sorbent material during an adsorption step. During a desorption step, the hot fluid feeding unit feeds the DAC unit with hot fluid simultaneously as vacuum is applied by the vacuum pump, whereby carbon dioxide, and optionally water vapour, is released. Afterwards, the post-processing unit separates carbon dioxide into a carbon dioxide stream and optionally condenses any water vapour into water and separates the water as a liquid water stream. When waste / excess heat from the externally provided hot fluid has been extracted from the DAC or DAC system, the cooled fluid is circulated back to the external source by the recirculation unit. In an embodiment, the encompassing container has cylindrical walls and at least one removable wall, which facilitates easy replacement of the DAC units or cassettes. In one embodiment the container is cylindrical and have convex side walls. In one embodiment, one of said convex side walls is removable. The inclusion of a recirculation unit for circulating initially hot fluid back to the external source as a cooled fluid allows for the recovery and reuse of thermal energy, contributing to the overall sustainability and efficiency of the system.

[0035] In an embodiment, the system comprises several DAC units being arranged and stacked on top of each other in the container. The arrangement of multiple DAC units stacked on top of each other in the container maximizes the use of vertical space, allowing for a more compact system design that can be beneficial in space-constrained environments. Stacking DAC units can facilitate the integration of a centralized control and monitoring system, improving operational efficiency and potentially reducing maintenance costs due to the consolidated configuration.

[0036] In another embodiment, the system further comprises a hot fluid feeding unit comprising a fluid tank and a fluid pump. The inclusion of a hot fluid feeding unit with a fluid tank and a fluid pump ensures a consistent and controlled supply of hot fluid to the system, which can lead to more stable and efficient operation. The fluid tank allows for the storage of hot fluid, providing a buffer that can accommodate fluctuations in demand or supply, thus enhancing the reliability of the system. The hot fluid feeding unit (200) may further comprise a fluid feedback loop from the DAC unit (700) to the fluid tank (71). The hot fluid feeding unit enables precise temperature control of the fluid entering the system, which can improve the overall thermal management and efficiency of the process. The integration of the hot fluid feeding unit can allow for the pre-heating of fluids, reducing the energy required for reaching operational temperatures and thus contributing to energy savings.

[0037] The system may utilise hot fluid emanating from an external source selected from an electrolyzer, a heat pump, a nuclear plant, a transformer, solar panels, a district heating network, a HVAC system, a data centre, an inter-stage cooling system in compressors, steam cycles, and an industry generating waste heat in the form of hot fluids. The ability to select from a diverse range of external sources, such as an electrolyzer, heat pump, or nuclear plant, provides flexibility in sourcing hot fluid, allowing the system to be tailored to the most readily available or cost-effective heat source. Utilizing waste heat from various industrial processes, such as data centres or district heating networks, promotes energy recycling, and can significantly reduce the environmental impact of the system by lowering overall greenhouse gas emissions. In an embodiment, the external source is an electrolyzer, and the hot fluid used from the electrolyzer may be an electrolyte or cooling fluid. An electrolyzer as the external source of hot liquid allows the system to integrate with hydrogen production facilities, where waste heat is a byproduct, thus improving the overall energy efficiency of such facilities. In addition, electrolysers benefit from recirculation of cooled fluid and condensed water from the system.

[0038] BRIEF DESCRIPTION OF DRAWINGS

[0039] The present disclosure is illustrated by way of example and not limited in the accompanying figures in which like reference numerals indicate similar elements. Embodiments of the application will now be described with reference to the attached drawings:

[0040] Figure 1 - Shows a cross-sectional view of a direct air capture of carbon dioxide (DAC) unit or cassette according to the invention.

[0041] Figure 2 - Shows an enlarged side-view of the DAC in Figure 1. Figure 3 - Shows an enlarged side-view of the DAC in Figure 1. Figure 4 -Shows a cross-sectional side-view of the DAC in Figure 1, wherein several DACs are stacked in a rack / container.

[0042] Figure 5 - Shows a perspective view of a DAC system according to the invention. Figure 6 - Shows a chart of the method of using the DAC integrated with an external source of fluid providing waste heat.

[0043] Figure 7 - Shows a perspective view of the alternative DAC unit or cassette.

[0044] Figure 8 - Shows a perspective view of the container of an alternative DAC unit according to the invention.

[0045] Figure 8 - Shows a side-view of the long side of the alternative DAC container in Figure 8. Figure 9 - Shows a side-view of the short side of the alternative DAC container in Figure 8 without its side walls.

[0046] Figure 10 - Shows a side-view of the short side of the alternative DAC container in Figure 10, encompassing several alternative DAC units stacked on top of each other.

[0047] Figure 12 - Shows a perspective view of an alternative DAC housing encompassing several alternative DAC units, without side and long side walls.

[0048] Figure 13 - Shows a side-view of the short side of the alternative DAC housing in Figure 11, encompassing several alternative DAC units stacked on top of each other.

[0049] In the drawings, the term “FIG” is used instead of “Figure.” Black bold arrows represent flow direction of air.

[0050] DETAILED DESCRIPTION

[0051] The present invention covers a method of direct air capture of carbon dioxide using waste heat from a fluid from an external source comprising the steps of: a) blowing ambient air comprising carbon dioxide through a direct air capture of carbon dioxide (DAC) unit 1 comprising a sorbent material capable of selectively adsorbing carbon dioxide and water vapour and contacting said air with the sorbent material 8 during an adsorption step to adsorb carbon dioxide and optionally water vapour; optionally, purging the DAC unit 1 by applying vacuum, for example at 0.15-1 atm; b) releasing carbon dioxide and water vapour from the sorbent material by transferring heat from the external hot fluid to the sorbent material during a desorption phase, while applying vacuum, and wherein said hot fluid is not in direct contact with the sorbent material, c) separating the carbon dioxide into a carbon dioxide stream, and optionally condensing any water vapour into water and separating the water as a liquid water stream; optionally, cooling the sorbent material using a cooling fluid; and d) recirculating the initially hot fluid to the external source as a cooled fluid. There are two main phases or steps in the DAC method; first the adsorption phase, and then the desorption phase.

[0052] Adsorption

[0053] In the adsorption step, step a, air is blown through a blower through the sorbent material which is kept between a barrier material (see below), either as a coating on the barrier material or as granules in the form of a fixed bed. In step a), the ambient air may be heated before being blown into the DAC unit to avoid any condensation of water vapour in colder conditions.

[0054] The adsorption step may be stopped, i.e. by stopping the inlet of ambient air by an air blower when the sorbent material is at least 70% saturated, such as at least 75, 80, 85, 90%, 95%, and as determined by continuously monitoring the carbon dioxide concentration in the exhaust or depleted air stream. At the start of the adsorption step, the concentration of carbon dioxide in the DAC may be around 1-60 ppm carbon dioxide in the exhaust or depleted air stream. This concentration keeps rising as and finally the bed starts saturating. In one embodiment, the adsorption step is stopped when the sorbent material is at least 70% saturated. The measuring of the carbon dioxide concentration may be conducted on exhaust air leaving the DAC unit.

[0055] The sorbent material may suitably be selected from amines impregnated on a support material, or weak ionic resins or metal organic frameworks (MOFs). In one embodiment, the sorbent material is amine impregnated sorbents. These amines typically primary, secondary, tertiary, and branched amines that are impregnated on a support material. The support material may be selected from silica granules, silica gel, alumina, cellulose, metal-organic framework (MOF) materials, organic materials, or any material on which the amines can be impregnated, or any mixture of said support materials. The weak ionic resins may be selected from commercially available Lewatit VP 1065, Diaion HP 20, etc.

[0056] The particle size of said sorbent material is more than 0.1 mm and up to 2 mm, such as 0.1-2 mm or 0.5-2 mm. The particles may be in the form of granules, beads, or monoliths. The particle size can be smaller, in the form of a fine powder, if the sorbent material is used as a coating on a support structure, such as the pipes or plates in the DAC unit. The size of the particles is optimized to reduce the pressure drop inside the system. When the particle diameter varies between 0.5-2 mm, the pressure drop in the sorbent material (bed) has been estimated to vary between 4193 Pa to 219 Pa. The lower the pressure drop, the lower is the blower work requirement, and thereby the electricity demands of the process.

[0057] The sphericity of the particles may range between 0-1. The bed voidage is preferably more than 0.4. The thermal conductivity is preferably more than 0.16 W / mK.

[0058] Purging step

[0059] After step a, the DAC may be purged by applying vacuum. In this step, the vacuum pump starts purging the gases out of the DAC chamber until the required vacuum is generated, e.g., 0.15-1 atm. This step may or may not be required depending on the desired purity of the final carbon dioxide gas.

[0060] Desorption (regeneration step)

[0061] According to an embodiment, in step b) the heat-transfer is normally achieved through a highly thermally conducting metal or metal alloy barrier between the hot fluid and the sorbent material. The material of construction of the plates is based on achieving higher heat transfer rates into the sorbent material from the hot fluid. The barrier material may be selected from copper, aluminium, and alloys having high thermal conductivity. In some cases, the metal or metal alloy may be stainless steel. In one embodiment, the material is copper or aluminium. In an alternate embodiment, the material is stainless steel. The barrier may be in different forms such as hollow plates (as shown in Figures 2, 3, 7 and 13) acting as carriers of said hot fluid. The metal carrier plates, hollow or not, may also be supplemented with metal carriers pipes / ducting made from the same material as the plates. The plates or pipes may be in direct contact with the sorbent material.

[0062] In step b), the external hot fluid may have a temperature of up to 600 °C in case of combustion and nuclear power plants (typically in the steam cycles mentioned above). In this case, virgin heat generated from said processes. Normally, the temperature would range from 15 to 200 °C, such as 45 to 200 °C when received from the external source. Examples of typical desired temperature intervals would be 45 to 99 °C or 45-95 °C for the externally provided hot fluid when received from the external source such as an electrolyser. However, another selection of electrolyser might change the temperature interval. In the case of a heated fluid directly from a nuclear plant, the temperature interval would be 5-50 °C (depending on ambient conditions) when passed via a heat pump (normally waste heat is discarded from nuclear plants by letting cooling liquids be poured into the sea or cooling dams or towers). If transferred to the DAC via a heat pump, then the 45 to 99 °C or 45-95 °C intervals would apply.

[0063] The present method and products may be integrated with more or less any external industrial process generating waste heat in the form of a hot fluid and thus having the need of a cooling step. Examples of such sources may be an electrolyser, a heat pump, a transformer, a district heating network, a HVAC system, a data centre, a solar panel, an inter-stage cooling system in compressors, steam cycles (waste heat recovery systems in industrial processes or any fuel fired heat and / or power plants), and a nuclear plant provided with a heat pump. The hot-cold fluid could also circulate between the DAC and nuclear plant without a heat pump.

[0064] Most of these processes can provide a hot fluid as a result of an internal cooling process, or excess heat may be converted to a hot fluid in said external source or in the DAC method / system. The fluid may be any gas or liquid. Examples of gases may be carbon dioxide, hydrogen, nitrogen gas, or water vapour. Examples of fluids may be liquid water, electrolyte solution in electrolysers and oil. Excess heat, if not provided in the form of a hot fluid, may be converted using a heat-exchanger or heat pump to a suitable heated fluid.

[0065] Vacuum is maintained in the chamber where the sorbent material is located using a vacuum pump. The combination of vacuum and heating the sorbent material with hot fluid releases the carbon dioxide and water vapour that is bound to the sorbent material.

[0066] The method according to anyone of the preceding claims, wherein the sorbent material is mixed with highly thermally conducting material. The highly thermally conducting material may be of the same material as the barrier material.

[0067] In one embodiment, in step b), water or water vapour is sprinkled / sprayed on the sorbent material, or carbon dioxide or hydrogen gas (optionally heated) is passed through the DAC unit to increase the humidity and pressure inside the chamber to increase the speed of the carbon dioxide release.

[0068] The desorption cycle is monitored using a carbon dioxide analyser, which is measuring the carbon dioxide concentration at the outlet of the DAC unit. It can also be monitored with a flow meter after a vacuum pump.

[0069] During the desorption phase, a carrier gas may be used to facilitate the evacuation of carbon dioxide out of the chamber. Examples of carrier gases may be nitrogen gas, hydrogen gas, carbon dioxide gas, or water vapour. Post-processing

[0070] The desorption process generates release of carbon dioxide gas and normally water vapour. If the purity of the carbon dioxide gas is not crucial, the carbon dioxide gas in the DAC unit is simply evacuated by vacuum for possible further processing or use. The water vapour regenerated from the sorbent material may be condensed using a condenser to purify the carbon dioxide stream.

[0071] Cooling of sorbent material

[0072] Once the sorbent material is regenerated, the sorbent needs to be cooled down to be able to allow adsorption. Either the sorbent material is allowed to cool down, but for efficiency reasons the method preferably includes an active cooling step. The active cooling step may involve blowing air on the sorbent filter, i.e., similar to performing an extended adsorption cycle, or blowing another gas such as carbon dioxide (for example generated using the DAC method), nitrogen gas or any other inert gas. Another option is to allow a cooling fluid, instead of a hot fluid, run through the plates or pipes. Cooling may be performed using an external cooling fluid, but the cooled “hot” fluid may be used for this. Once the DAC unit cools down to an adequate temperature, the adsorption cycle can be initiated.

[0073] Products and recirculation

[0074] The carbon dioxide stream may be utilized as a feedstock, carrier gas, or sent for permanent storage. The condensed H2O can be a used for purposes like water electrolysis in an electrolyser or reused as make-up water in a nuclear plant.

[0075] When the present method has made use of said fluid excess / waste heat, and the initially hot fluid has turned into a cooled fluid, it may be returned to the external source to act as a cooling fluid in its cooling process and thereby increase the efficiency of said external industrial process.

[0076] Further features of the method are disclosed in the illustrative example below.

[0077] DAC unit

[0078] With reference to figure 1, the present invention further covers a DAC unit or cassette 1 using waste heat from a fluid from an external source. The DAC unit 1 comprises a housing 2 with a chamber 3, an outwardly protruding air inlet 4 and an outwardly protruding air outlet 5 leading carbon dioxide depleted air out of the chamber, an internal perforated floor or mesh 6 and at least a set of metal barriers 7 adapted to accommodate a sorbent material 8 and a hollow metal heat-exchanger device 9, and the perforated floor retains the sorbent material but allows air led into the sorbent material to exit, and a fluid inlet header 10 and a fluid inlet piping 11 leading hot fluid to the heat-exchanger device, and a fluid outlet header 12 and a fluid outlet piping 13 leading hot fluid from the heat-exchanger device 9, and wherein, when ambient air comprising carbon dioxide is led into the chamber 3 via the inlet 4 and through the sorbent material 8, the perforated floor 6, and out through the air outlet 5, carbon dioxide and water vapour may be collected by the sorbent material during an adsorption step and released during a desorption step.

[0079] In one embodiment, the metal barriers 7 and hollow metal heat-exchanger device 9 are integrated as hollow heat-exchanger plates 15 (see figure 2). In another embodiment, the hollow metal heat-exchanger device 9 is in the form of hollow metal piping (not shown in the drawings). In this case, said pipes are arranged on the inside of the metal barriers 7, i.e., in contact with the sorbent material. In one embodiment, the sorbent material is coated on the hollow heat-exchanger plates 15.

[0080] The DAC unit is designed to be stackable on top of at least another DAC unit. The outwardly protruding air inlet 4 and outlet 5 are designed to be capable of being used as suspension elements, so that the DACs can be suspended / supported in a rack or container 20. The air inlet 4 and outlet 5 would then protrude through rack or the container walls (see figure 4).

[0081] The air inlet 4 may be equipped with an inlet valve 41 placed inside or outside of the orifice of the air inlet 4. Air outlet 5 may also be equipped with an air outlet valves 42 and 90), which may also be placed both inside and outside of the orifice of the air outlet 5.

[0082] In another and currently preferred embodiment, the DAC unit or cassette is devised differently. With reference to mainly figure 7, a DAC unit 700 is shown which comprises a housing 701 with a chamber 702, an air inlet 703 for ambient air with carbon dioxide and an air outlet 704 (figure 12) leading carbon dioxide depleted air out of the chamber, an internal perforated floor or mesh 712 and at least a set of metal barriers 705 adapted to accommodate a sorbent material 8 and a hollow metal heat-exchanger device 706, and the perforated floor retains the sorbent material but allows air led into the sorbent material to pass through. The perforated floor 712 is supported by a support / spacer structure 711, which also provides a space for the depleted air to escape to and exit via the outlet 704. The DAC unit 700 further comprises a fluid inlet header 707 with a fluid inlet piping 708 leading hot fluid to the heatexchanger device 706, and a fluid outlet header 709 with a fluid outlet piping 710 leading hot fluid from the heat-exchanger device 706, and wherein, when ambient air comprising carbon dioxide is led into the chamber 3 via inlet 703 and through the sorbent material 8, the perforated floor 712, and out through the air outlet 704, carbon dioxide and water vapour may be collected by the sorbent material during an adsorption step and released during a desorption step.

[0083] In one embodiment, the metal barriers 705 and hollow metal heat-exchanger device 706 are integrated as hollow heat-exchanger plates 713. In another embodiment, the hollow metal heat-exchanger device 706 is in the form of hollow metal piping (not shown in the drawings). In this case, said pipes are arranged on the inside of the metal barriers 705, i.e., in contact with the sorbent material. In one embodiment, the sorbent material is coated on the hollow heat-exchanger plates 713.

[0084] The DAC unit 700 is designed to be stackable on top of at least another DAC unit. The air inlet 4 and air outlet 5 are designed to be capable of supporting each other. Thus, a rack is not needed for supporting them (see figures 12 and 13).

[0085] Air inlet 4 may be equipped with an inlet valve 41 placed inside or outside of the orifice of the air inlet 4. Air outlet 704 may also be equipped with an air outlet valves 42 and 90), which may also be placed both inside and outside of the orifice of the air outlet 704.

[0086] Further features of the DAC unit 1 is disclosed in the illustrative example below.

[0087] DAC system

[0088] With reference to figure 5, the present invention further covers a DAC system comprising a DAC system 25 capable of using waste heat from a hot fluid 52 from an external source comprising: at least one DAC unit 1, for example the one described above, a container or rack 20 encasing and suspending said DAC unit(s), an air ventilation unit 30 having an air drum 31, an air inlet 32, a blower 33 for transporting inlet air to an air inlet connection channel 34 connected to the air inlet 4 of the DAC unit, a hot fluid feeding unit 200 for providing the DAC unit 1 unit with hot fluid 52, a vacuum pump 106, a post-processing unit 300 for handling a stream of carbon dioxide, and optionally water vapour, a recirculation unit for circulating the initially hot fluid cooled fluid to the external source. When ambient air comprising carbon dioxide is led into the DAC unit 1 by the air ventilation unit 30, said carbon dioxide and water vapour is collected by the sorbent material 8 material during an adsorption step.

[0089] The hot fluid feeding unit 200, having received hot fluid from an external source, feeds the hot fluid 52 to the DAC unit 1 during a desorption step, while vacuum is applied by the vacuum pump 106, carbon dioxide, and optionally water vapour, is released.

[0090] Afterwards, the post-processing unit 300 separates carbon dioxide into a carbon dioxide stream via a post-processing subunit 300 A and optionally condenses any water vapour into water and separates the water as a liquid water stream via a post-processing subunit 300B.

[0091] When waste / excess heat from the externally provided hot fluid has been extracted from the DAC unit 1 or DAC system 25, the cooled fluid is circulated back to the external source by the recirculation unit.

[0092] In the DAC system 25 several DAC units 1 may be arranged, and stacked on top of each other. The DAC units 1 may be suspended in a rack or container 20 having walls 21 through which the outwardly protruding air inlets 4 and outlets 5 penetrate and protrude through said walls into said air inlet connection channel 34, thus providing the DAC units with air. Air inlet 4 may be equipped with a valve 42 (for venting of air during adsorption or cooling steps) placed inside or outside of the orifice of the air inlet 4 . In the latter case, the inlet valve of air inlet 4 is thus facing the inside of air inlet connection channel 34. Air outlet 5 may also be equipped with a valve 90 (for venting of air during purging, desorption and postprocessing steps), which may also be placed both inside and outside of the orifice of the air outlet 5.

[0093] The air ventilation unit 30 may also comprise a heater 40 for heating inlet air to avoid any liquid condensation in colder climates / temperatures. The heater is preferably located before the air blower 33. Further, the air ventilation unit 30 may comprise an air filter 60 for filtering air before being blown into the DAC unit. In case of a heater 40, the filter 60 is located before the heater.

[0094] In one embodiment, the hot fluid feeding unit 200 comprises an external hot fluid source 70 (for example an electrolyser), a fluid tank 71 and a fluid pump 73. The hot fluid 52 from the external hot fluid source enters the hot fluid feeding unit 200 via hot fluid tank 71, from which the hot fluid is fed to the DAC 1 by pump 73.

[0095] The hot fluid feeding unit 200 further comprises a fluid feedback loop from the DAC unit 1, preferably to fluid tank 71. This is regulated by valves determining the direction of flow towards the fluid feedback loop or towards the recirculation unit 400. When the hot fluid has been circulated in the DAC system 25 until excess heat has been extracted and the fluid has cooled, then the cooled liquid is shunted back to the external source via the recirculation unit 400. Before being recirculated to the external source (for example an electrolyser), the cooled liquid may also be used as a cooling fluid in the DAC unit 1, whereby the cooled liquid is circulated in the hollow metal heat-exchanger device to cool the sorbent material.

[0096] Ambient air enters the air ventilation unit 30 through the air inlet 32 (of for example an air drum 32), where the air may be heated and blown via the air inlet connection channel 34 to the air inlet 4 of the at least one DAC unit 1.

[0097] With reference to figure 6 in combination with figures 7-13, there is provided another embodiment of the system, comprising a DAC system 800 capable of using waste heat from a hot fluid 52 from an external source comprising: at least one DAC unit 700, a container 500 having at least one removable side wall 504, wherein the container encases the at least one DAC unit (700), and further has an air inlet 510, a fluid inlet 520, an air outlet 540, and a fluid outlet 550, an air ventilation unit 801 (having for example an air drum 31, an air inlet 32, a blower 33) transporting inlet air to an air inlet 703 of the DAC unit 700, a hot fluid feeding unit 200 for providing the DAC unit 700 unit with hot fluid 52, a vacuum pump 106, a post-processing unit 300 for handling a stream of carbon dioxide, and optionally water vapour, a recirculation unit for circulating the initially hot fluid cooled fluid to the external source.

[0098] When ambient air comprising carbon dioxide is led into the DAC unit 700 by the air ventilation unit 801, said carbon dioxide and water vapour is collected by the sorbent material 8 material during an adsorption step.

[0099] The hot fluid feeding unit 200, having received hot fluid from an external source, feeds the hot fluid 52 to the DAC unit 1 during a desorption step, while vacuum is applied by the vacuum pump 106, carbon dioxide, and optionally water vapour, is released.

[0100] Afterwards, the post-processing unit 300 separates carbon dioxide into a carbon dioxide stream via a post-processing subunit 300 A and optionally condenses any water vapour into water and separates the water as a liquid water stream via a post-processing subunit 300B.

[0101] When waste / excess heat from the externally provided hot fluid has been extracted from the DAC unit 700 or DAC system 800, the cooled fluid is circulated back to the external source by the recirculation unit.

[0102] In the DAC system 800 several DAC units 700 may be arranged and stacked on top of each other. The stacked DAC units are encased in a container 500 having cylindrical walls 501, a convex side wall 503 and at least one removable convex side wall 504 (see figure 8) forming a chamber 508. The cylindrical shape of the container 500 as well as the convex side walls significantly reduces the need for reinforcements to maintain the structural integrity under vacuum conditions.

[0103] The container 500 may be supported by external support legs 600 for stable placement on the ground. In one embodiment, container features internal seats 610 receiving and supporting the DAC units 700 in the container.

[0104] The air inlet 703 may be equipped with a valve 42 (for venting of air during adsorption or cooling steps) placed inside or outside of the orifice of the air inlet 703. Air outlet 704 may also be equipped with a valve 90 (for venting of air during purging, desorption and postprocessing steps), which may also be placed both inside and outside of the orifice of the air outlet 704.

[0105] The air ventilation unit 801 may also comprise a heater 40 for heating inlet air to avoid any liquid condensation in colder climates / temperatures. The heater is preferably located before the air blower 33. Further, the air ventilation unit 30 may comprise an air filter 60 for filtering air before being blown into the DAC unit. In case of a heater 40, the filter 60 is located before the heater.

[0106] In one embodiment, the hot fluid feeding unit 200 comprises an external hot fluid source 70 (for example an electrolyser), a fluid tank 71 and a fluid pump 73. The hot fluid 52 from the external hot fluid source enters the hot fluid feeding unit 200 via hot fluid tank 71, from which the hot fluid is fed to the DAC 700 by pump 73.

[0107] The hot fluid feeding unit 200 further comprises a fluid feedback loop from the DAC unit 1, preferably to fluid tank 71. This is regulated by valves determining the direction of flow towards the fluid feedback loop or towards the recirculation unit 400. When the hot fluid has been circulated in the DAC system 800 until excess heat has been extracted and the fluid has cooled, then the cooled liquid is shunted back to the external source via the recirculation unit 400. Before being recirculated to the external source (for example an electrolyser), the cooled liquid may also be used as a cooling fluid in the DAC unit 700, whereby the cooled liquid is circulated in the hollow metal heat-exchanger device 706 to cool the sorbent material.

[0108] Ambient air enters the air ventilation unit 801 through the air inlet 32 (of for example an air drum 32), where the air may be heated and blown to the air inlet 704 of the at least one DAC unit 700.

[0109] With reference to figure 8, in one embodiment the container 500 has cylindrical walls 501 and convex side walls. In another embodiment, one of the side walls 504 is removable. The removable side wall 504 is fastened to the cylindrical walls 501. In one embodiment, said cylindrical walls 501 as well as the removable side wall 504 have peripheral flanges 502 and 505, respectively, which may be bolted together.

[0110] With reference to figures 8 to 11, the air inlet 510 has an external connection interface 511, which in one embodiment has an external protruding cylinder 512 and external outwardly protruding flange 513 to which the air ventilation unit 801 is connected. The air is introduced into the container via a hole 514. Air that has been introduced into the container 500 and passed through the DAC units 700 exits the container 500 through an air outlet 550 having an external connection interface 541, which in one embodiment has an external protruding cylinder 542 and external outwardly protruding flange 543 to which the exit air unit 91 and post-processing unit 300 are connected. The air is exits the container via a hole 544.

[0111] The hot fluid 52 enters the container 500 via a fluid inlet 520 which has an external connection interface 521, which in one embodiment has an external protruding cylinder 522 and external outwardly protruding flange 523 (connected to the hot fluid feeding unit 200), and internal connection interface 524, an internal protruding cylinder 525, and an internal outwardly protruding flange 526. The hot fluid is introduced into the container via a hole 527. Flange 526 is connected to a fluid inlet manifold 528 having a flange 529, and a connection interface 530 by which the fluid inlet header 707 of the DAC unit is connected.

[0112] Hot fluid 52 that has been introduced into the container 500 and passed through the DAC units 700 exits the DAC unit 700 via an outlet piping 710 of a fluid outlet header 709. At a connection interface 551, the fluid outlet header 709 is connected to an outlet manifold 552. Said outlet manifold has a connection flange 553 which is connected to a fluid outlet 550 by an internal outwardly protruding flange 556, which continues into an internal protruding cylinder 555, which in turn continues to an external connection interface 557 having an external cylinder 558 and an external outwardly protruding flange 559. The hot fluid 52 exits the container 500 via a hole 560. The container 500 is reconnected with the hot fluid feeding unit 200 via flange 559.

[0113] The fluid inlet and outlet manifolds may be flanged, uni-coupling or of other type.

[0114] With reference to figures 9 and 12, the container 500 further features a carbon dioxide and water vapour outlet 620 which handles the pressure equalization during the vacuum phase. The convex side walls take the pressure, but placing the DAC units 700 directly against the curved side wall does not provide a good seal. Therefore, inwards from the convex side wall 503 there is arranged a flat plate 506 (for example with strengthening elements on the backside to maintain plate strength if less plate material is desired) that the DAC units are pushed against. A gasket 507 may be arranged between the flat plate and DAC units to avoid leaks between the DACs and said wall. The container may also comprise other gaskets or sealing elements to avoid air leakage. Having a closed compartment and reducing the pressure (as under the vacuum phase) the plate 506 would deflect or rip, but the outlet 620 reduces the pressure on said plate such that it will experience the same pressure as the rest of the container chamber 508. There is also an outlet 630 for condensed fluid (water) at the bottom of the container, placed low enough such that any condensation water does not get stuck in the "dead zone" against the convex side wall. The outlets 620 and 630 provide equal negative pressure in all zones of the container, also beneath the DAC units and seats 610 which is a "semi-closed" compartment. The outlet 620 is connected to the exit air unit 91. The outlet 630 is connected to the post-processing unit 300.

[0115] Inside the container 500 there is also provided an air sealing device 640, comprising a sleeve 641 with a support bracket 642. The sleeve as adapted to receive a pipe or rod 643 from which protrudes a sealing blade 644. When the pipe is inserted into the sleeve, the blade pushes against the DAC units 700 during operation. This seals the airway and thereby forces the air through the sorbent material 8 instead of leaking around the DACs, i.e., sealing the “air inlet zone” from the “air outlet zone”. Since all DACs must be removed for change of sorbent material, the sealing blade is turned upward such that the DACs are free to be lifted and pulled out of the container. After the DACs are put back, the sealing blade (suspended with some tension in the sleeve) is rotated down against the boxes.

[0116] Additional equipment may be added in an auxiliary container 35, a condenser, a vacuum pump, a compressor to compress carbon dioxide, a control panel having electrical and electronic parts to control the process, etc. The external source from which hot fluid emanates from may be selected from an electrolyzer, a heat pump, a nuclear plant, a transformer, a district heating network, a HVAC system, a data centre, a solar panel, an inter-stage cooling system in compressors, steam cycles, and an industry generating waste heat.

[0117] Further features of the DAC system are disclosed in the illustrative example below.

[0118] Method, DAC unit, and system

[0119] An illustrative example of a DAC method, DAC unit 1 and system 25 will now be given, with reference to Figure 6.

[0120] During the adsorption step, air enters the DAC system 25 through the air ventilation unit 30 via air inlet 32 of air drum 31, passes through a filter 60, may or may not be heated by heater 40. An intermediate air valve 61 regulates the inflow of air, and air that passes said valve is blown into the DAC unit 1 by air blower 33 after having passed air inlet valve 41 of air inlet 4, preventing back-flow from the DAC unit. The air inlet connection channel 34 lies in between blower 33 and the DAC unit 1 (see figure 5). Air that has passed the sorbent material exits the DAC 1 unit via valve 90 into an exit air unit 91.

[0121] If there is a desire to heat the inlet air to during adsorption, heater 40 does this. Air, heated or not, enters the sorbent material or sorbent bed material 8. Carbon dioxide and possibly water in the form of humidity is adsorbed by the sorbent material 8. Air passing through the DAC unit exits through air outlet valve 90 of air outlet 5. Adsorption ends when a carbon dioxide sensor or monitoring device (not shown in drawings) indicates that saturation has been reached.

[0122] After a purging step, optionally with vacuum applied by vacuum pump 106 (while air outlet valve 42 is open), the DAC unit 1 is ready for desorption step.

[0123] In the desorption step, hot fluid 52 in tank 71 (received from an external source) is pumped is pumped by pump 73 (through open valves 72 and 74) through inlet valves 50 into the hollow heat-exchanger device 9 via the fluid header inlet 10 and the fluid inlet piping 11. A bridging piping 14 (see figure 3) connects the heat-exchanger device 9 on each side of each sorbent material. During the desorption step, pump 106 applies vacuum to the DAC 1 unit (valve 42 being open). The hot fluid 52 leaves the heat-exchanger device 9 via fluid outlet header 12, outlet piping 13 (see figure 2) and outlet valves 51. The hot fluid is circulated back to tank 71 (valve 75 being open and valve 80 being closed), thus passing through the whole hot fluid feeding unit 200. Then the hot fluid is fed yet again to the DAC unit 1. Optionally, water or water vapour is sprinkled / sprayed on the sorbent material through sprinkler / spray devices (not shown in drawings), or carbon dioxide or hydrogen gas (optionally heated) is passed through the DAC chamber 3 to increase the speed of the carbon dioxide release. A carrier gas such may be used to facilitate the evacuation of carbon dioxide out of the chamber. Examples of carrier gases may be nitrogen gas, hydrogen gas, carbon dioxide gas, or water vapour. Devices for adding such gases are not shown in the drawings.

[0124] The circulation of hot fluid in the until the fluid waste heat has been transferred to the sorbent material and the fluid has cooled. The cooled liquid 81 may then be shunted towards the recirculation unit 400 for recirculating the hot fluid (valve 75 being closed and valve 80 being open) to the external source as a cooling fluid, for use in the external source’s processes.

[0125] The post-processing of desorbed fluids is handled by post-processing unit 300, which separates carbon dioxide into a carbon dioxide stream via a post-processing subunit 300 A and optionally condenses any water vapour into water and separates the water as a liquid water stream via a post-processing subunit 300B. If purified carbon dioxide gas is desired, condenser 101 (valve 42 being open), condenses any water vapour and the formed water is pumped by pump 104 to water storage tank 105. The condenser is connected to cooling water supply 102 and return 103. Connections from the water storage tank 105 to the sprinkler / spray device of the DAC unit 1 and unit for recirculation of make-up water to the external source is not shown in the drawings.

[0126] Purified or non-purified a carbon dioxide is driven by vacuum pump 106 of postprocessing subunit 300 A, via open valve 107 (valve 111 being closed), to compressor 108 that compresses the carbon dioxide for storage in carbon dioxide storage tank 110 (inlet valve 109 being open). If carbon dioxide is to be circulated to an external user as external carbon dioxide 113, inlet valve 109 is kept shut and carbon dioxide flows via open valve 11 to compressor 112, which compresses the carbon dioxide before delivery to the external user.

[0127] After desorption, the sorbent material may need to be cooled. This is performed either by passive or active cooling. In the latter case, either air is blown over the sorbent material 7 by the air ventilation unit 30 and / or the now cooled fluid from the hot fluid feeding unit 200 is circulated in the heat-exchanger device 9 for reverse heat-exchange. Air blown through the sorbent material for cooling purposes exits the DAC 1 unit via valve 90 into the exit air unit 91.

[0128] When the sorbent material has cooled, another adsorption cycle is initiated.

[0129] The DAC system 25 may also feature a number of valves. Examples of said valves and their locations are given in the illustrative system given above and as depicted in figure 6. Valves are depicted as either open (white) or closed (black). The “open” or “closed” states in the drawings represents states in a certain phase and does not represent their constant state.

[0130] In the application the term “pipe” or “ducting” is used alternatively or together, with equivalent meaning.

[0131] EXAMPLES

[0132] Example 1 - Direct air capture of carbon dioxide from ambient air Sorbent material in the form of Lewatit VP 1065 samples (weak ionic resin) were obtained from Lanxess. 626 gm of the Lewatit samples was dried for 617 mins (365 and 252 mins on two different days) at 95 °C using a furnace. The final mass of the dried samples was 389 g. The samples were passed over a sieve of 53 microns, but there was no mass loss, i.e. the particles were all larger than 53 pm. The perforated floor or mesh 6 in the DAC had 50- micron size holes, thus no sorbent particles could flow out of the chamber. However, the actual size of the particles used were approximately 500 um or 0.5 mm. The density of the samples was measured was approximately 0.57 g / cc after drying.

[0133] The Lewatit sample was then poured and placed inside a small-scale DAC unit 1 prototype. It occupied 682 cc of volume inside the DAC unit. This was almost half of the volume of the chamber. The DAC unit was then sealed off in an airtight manner.

[0134] During the adsorption step, dry and compressed air having 420-440 ppm carbon dioxide was passed through the DAC unit which contains the sorbent material. The flowrate of the air was controlled by a gas mass flow controller, which was calibrated for Air / N2 flow. The outlet of the air from the DAC unit was connected to the carbon dioxide analyser. The analyser was a Model 906E carbon dioxide analyser (obtained from Quantek Instruments with range 0-2000 ppm with 1 ppm resolution and accuracy of ±5 ppm, and the frequency of measurement was set to 1 sec. The air flow rate during the experimental trials was between 1- 5 1 / min. The air was led into the DAC unit until the sorbent material was saturated with carbon dioxide (70 to more than 95%). This could be tracked through the breakthrough curve that shows the carbon dioxide concentration in the outlet of the DAC unit. The carbon dioxide concentration in the outlet from the DAC unit was between 2-60 ppm when the adsorption started and reached 420-440 ppm when the sorbent material saturated with carbon dioxide (i.e., the same concentration as of the ambient air). The air flow is stopped after the sorbent material was saturated with carbon dioxide and no further change in the carbon dioxide concentration was observed in the outlet of the DAC unit. During the desorption step, the DAC unit was heated with hot water (hot fluid) flowing in the outer copper jacket (hollow plates) of the DAC unit to heat up the sorbent material, and a vacuum pump kept the DAC unit under vacuum conditions. The temperature of the hot water was set between 60 to 92 °C during the experimental runs. The water temperature was held constant, and at the point of saturation, the sorbent material temperature was approximately 5 °C less than the temperature of the hot fluid.

[0135] Experiments were conducted within a pressure range of 150-1013 mbar inside the DAC unit. The vacuum pump maintains the vacuum pressure inside the chamber by removing the gases inside the DAC unit. Therefore, as soon as carbon dioxide starts desorbing from the sorbent material, the vacuum pump pushes the gases out of the chamber. The carbon dioxide released by the sorbent under the effect of vacuum and temperature, can also be carried out of the chamber through a carrier gas. In some of the experimental runs, a carrier gas in the form of nitrogen gas was used. The desorption step was carried out until there was no or very little carbon dioxide concentration detected in the carbon dioxide analyser of the stream coming out of the vacuum pump, at which point the hot fluid flow to the DAC unit was stopped and the vacuum pump turned off. The sorbent material was allowed to cool (no active cooling) before starting the next adsorption step.

Claims

Claims1. A method of direct air capture of carbon dioxide using waste heat from a hot fluid from an external source comprising the steps of: a) blowing ambient air comprising carbon dioxide through a direct air capture of carbon dioxide (DAC) unit comprising a sorbent material capable of selectively adsorbing carbon dioxide and water vapour and contacting said air with the sorbent material during an adsorption step to adsorb carbon dioxide and optionally water vapour;- optionally, purging the DAC unit by applying vacuum; b) releasing carbon dioxide and water vapour from the sorbent material by transferring heat from the external hot fluid to the sorbent material during a desorption phase, while applying vacuum, and wherein said hot fluid is not in direct contact with the sorbent material, c) separating the carbon dioxide into a carbon dioxide stream, and optionally condensing any water vapour into water and separating the water as a liquid water stream; d) optionally, cooling the sorbent material using a cooling fluid; and e) recirculating the initially hot fluid to the external source as a cooled fluid.

2. The method according to anyone of the preceding claims, wherein in step b) the heattransfer is achieved through a highly thermally conducting metal or metal alloy barrier between the hot fluid and the sorbent material.

3. The method according to claim 2, wherein the metal barrier material is selected from copper, aluminium, stainless steel, and alloys having high thermal conductivity.

4. The method according to anyone of the preceding claims, wherein in step b) the temperature of the external hot fluid is 30 to 200 °C when received from the external source.

5. The method according to claim 4, wherein the temperature of the external hot fluid is 30 to 99 °C when received from the external source.

6. The method according to anyone of the preceding claims, wherein the sorbent material is arranged in the form of a fixed bed.

7. The method according to claim 6, wherein the particle size of said sorbent material is more than 0.2 mm and up to 2 mm, the sphericity of the particles may range between 0-1, bed voidage is preferably more than 0.4, and the thermal conductivity is more than 0.16 W / mK.

8. The method according to anyone of the preceding claims, wherein the sorbent material is selected from amines impregnated on a support material, or weak ionic resins.

9. The method according to claim 8, wherein the support material is selected from silica granules, silica gel, alumina, cellulose, and metal-organic framework materials, organic materials, or any mixture of said support materials.

10. The method according to anyone of the preceding claims, wherein the sorbent material is mixed with highly thermally conducting material.

11. The method according to anyone of the preceding claims, wherein the inlet of ambient air in step a) is stopped when the sorbent material is at least 70% saturated as determined by continuously monitoring the carbon dioxide concentration in the exhaust air leaving the DAC chamber.

12. The method according to anyone of the preceding claims, wherein the hot fluid emanates from and is circulated back to as cooling fluid to an external source selected from an electrolyzer, a heat pump, a nuclear plant, a transformer, solar panels, a district heating network, a HVAC system, a data centre, an inter-stage cooling system in compressors, steam cycles, and waste heat generated from industrial processes.

13. The method according to claim 12, wherein the external source is an electrolyzer and the hot fluid used from the electrolyzer is an electrolyte or cooling fluid.

14. The method according to anyone of the preceding claims, wherein in step b) water or water vapour is sprinkled / sprayed on the sorbent material, or carbon dioxide or hydrogen gas is passed through the DAC chamber to increase the speed of the carbon dioxide release.

15. The method according to anyone of the preceding claims, wherein in step a) the ambient air is heated before being blown into the DAC unit.

16. The method according to anyone of the preceding claims, further comprising feeding the condensed water to the external source.

17. A direct air capture of carbon dioxide unit or DAC unit (700) capable of using waste heat from a hot fluid from an external source comprising a housing (701) with a chamber (702), at least an air inlet (703) and at least an air outlet (704) leading carbon dioxide depleted air out of the chamber, an internal perforated floor or mesh (711) and at least a set of metal barriers (705) adapted to accommodate a sorbent material (8) and a hollow metal heat-exchanger device (706), and the perforated floor maintains the sorbent material but allows air led into the sorbent material to pass through, and a fluid inlet header (707) and an fluid inlet piping (708) leading hot fluid to the heatexchanger device (706, and a fluid outlet header (709) and a fluid outlet piping (710) leading hot fluid from the heat-exchanger device (706), and wherein, when ambient air comprising carbon dioxide is led into the chamber (702) and through the sorbent material (8), the perforated floor (711), and out through the air outlet (707), carbon dioxide and water vapour may be collected by the sorbent material during an adsorption step and released during a desorption step.

18. DAC unit according to claim 17, wherein the metal barriers (705) and hollow metal heat-exchanger device (706) are integrated as hollow heat-exchanger plates (713).

19. The DAC unit according to claim 17, wherein the hollow metal heat-exchanger device (706) is in the form of hollow metal pipes.

20. The DAC unit according to anyone of claims 17 to 19, wherein the DAC unit is stackable on top of at least another DAC unit.

21. A DAC system (800) capable of using waste heat from a hot fluid from an external source comprising: at least one DAC unit (700) as defined in claims 17 to 20, a container (500) having least one removable wall, wherein the container encases the at least one DAC unit (700), and further has an air inlet (510), a fluid inlet (520), an air outlet (530), and a fluid outlet (540), an air ventilation unit (801) for providing air to the DAC unit, a hot fluid feeding unit (200) for providing the DAC unit with hot fluid, a vacuum pump (106), a post-processing unit (300) for handling a stream of carbon dioxide, and optionally water vapour, a recirculation unit (400) for circulating an initially hot fluid back to the external source as a cooled fluid, wherein, when ambient air comprising carbon dioxide is led into the DAC by the air ventilation unit (801), said carbon dioxide and water vapour is collected by the sorbent material during an adsorption step, wherein the hot fluid feeding unit (200) having received hot fluid from an external source provides the DAC unit with hot fluid feeds hot fluid to the DAC during a desorption step, whereby carbon dioxide, and optionally water vapour, is released, wherein the post-processing unit (300) for handling a stream of carbon dioxide separates the carbon dioxide into a carbon dioxide stream, and optionally condenses any water vapour into water and separates the water as a liquid water stream, and wherein the recirculation unit circulates the initially hot fluid back to the external source as a cooled fluid.

22. The DAC system according to claim 21, wherein several DAC units (1) are arranged, and stacked on top of each other in the container (500).

23. The DAC system according to anyone of claim 21 or 22, wherein the hot fluid feeding unit (200) comprises a fluid tank (71) and a fluid pump (73).

24. The DAC system according to claim 23, wherein a hot fluid feeding unit (200) further comprises a fluid feedback loop from the DAC unit (700) to the fluid tank (71).

25. The DAC system according to anyone of claims 21 to 24, wherein the external source from which hot fluid emanates from is selected from an electrolyzer, a heat pump, a nuclear plant, a transformer, solar panels, a district heating network, a HVAC system, a data centre, an inter-stage cooling system in compressors, steam cycles, and an industry generating waste heat in the form of hot fluids.

26. The DAC system according to claim 25, wherein the external source is an electrolyzer.

27. The DAC system according to claim 26, wherein the external source is an electrolyzer and the hot fluid used from the electrolyzer is an electrolyte or cooling fluid.

28. The DAC system according to anyone of claims 21 to 27, wherein the container (500) has cylindrical walls and convex side walls.

29. The DAC system according to claim 28, wherein one of the side walls is removable.

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