Method and system for separating CO2 from other components from gas mixture comprising at least 70% and at most 90% CO2

Abstract

The present invention relates to methods and systems for separating carbon dioxide (CO2) from a CO2-containing gas mixture comprising at least 70% and at most 90% by volume of CO2, such as a gas stream from a direct air capture system. The CO2 gas is separated from the remaining gas contained in the CO2-containing gas mixture by pressurizing and feeding the gas stream to an absorption tower in which CO2 is contacted with and preferentially dissolved in the water stream to produce a CO2-rich water stream. The CO2-containing water stream may then be reinjected into the geological reservoir or sent to the system, where CO2 is eluted from the water by releasing pressure, thereby producing a CO2 stream suitable for utilization. The water stream may then be reused in the absorption column.

Description

Field of the Invention

[0001] The present invention relates to a method and a system for separating substantially all of the carbon dioxide (CO2) from other components of a gas mixture, the gas mixture comprising at least 70% and at most 90% CO2 by volume. The gas mixture preferably originates from a system such as a so-called direct air capture (DAC) for CO2 or a unit designed to capture and / or concentrate a gas mixture containing CO2 emitted from, for example, an industrial plant or a power plant. Insofar as the gas mixture containing CO2 originates from a system for direct air capture (DAC) for CO2, preferably, it will comprise at least 80% and at most 90% CO2 by volume and may have a water content higher than 500 ppm and / or a relative humidity between 20% and 100% (i.e., it may be saturated with H2O at a given temperature and pressure).

[0002] The method and system of the present invention are characterized in that they rely on contacting a first gas mixture stream (G1) comprising at least 70% and at most 90% CO2 by volume with a first water stream (W2), thereby producing a second water stream (W4) which has been enriched in dissolved CO2 compared to the first water stream (W2), and a pressurized gas mixture (G3) which has been depleted of substantially all CO2 compared to the first gas mixture (G1). Preferably, the first gas mixture (G1) will comprise at least 80% and at most 90% CO2 by volume, and may have a water content higher than 500 ppm and / or a relative humidity between 20% and 100% (i.e. it may be saturated with H2O at a given temperature and pressure).

[0003] In one embodiment of the present invention, for example, if the first water flow (W2) is in the form of groundwater from a geological reservoir, the produced water flow (W4) can be transported to an injection system for injection into the geological reservoir and subsequent storage of the CO2 contained therein in the geological reservoir.

[0004] Alternatively, in another embodiment of the present invention, if the gas mixture (G1) comprises less than 10% by volume, such as less than 8%, less than 6% or less than 4%, of any one or more gases whose solubility in water at the applied pressure and temperature is equal to or higher than the solubility of carbon dioxide (CO2), or whose solubility in water at a pressure of 1 atm and a temperature between 10 and 70°C is 0.5 to 2.5 g per kg of water, then the produced water stream (W4) can be conveyed to a system for desorbing or desorbing CO2 dissolved in the water stream (W4), thereby generating a stream of concentrated and purified CO2 and a third water stream (W5), which can be recycled to the flow of the first water stream (W2) at a point before the first water stream (W2) contacts the gas mixture (G1).

[0005] Further alternatively, in yet another embodiment of the present invention, wherein the first water stream (W2) is in the form of seawater, the water stream (W4) may be collected and stored for subsequent use, for example, for transporting the captured CO2 for utilization or for transporting the captured CO2 for permanent or intermediate storage.

[0006] In the method and system of the present invention, substantially all of the carbon dioxide (CO2) can be separated from other components in a gas mixture, which can be from any source. However, gas mixtures originating from, for example, systems for direct air capture (DAC) or units designed to capture or concentrate CO2 in a CO2-containing gas mixture emitted from, for example, an industrial plant or power plant are particularly suitable for the method and system according to the present invention. The CO2-containing gas mixture captured by a DAC system typically contains large amounts of other gases derived from the atmosphere, such as nitrogen (N2), oxygen (O2) and argon (Ar), which need to be separated from the captured CO2 if the CO2 is to be utilized or stored for subsequent use.

[0007] Today, most processes for further purification of CO2-containing gas streams obtained from DAC rely on subsequent liquefaction and transportation of the CO2 by compression at elevated pressure and cryogenic temperatures, which is a relatively energy-intensive process for currently available technologies. Furthermore, the gas streams typically obtained from DAC, and especially when based on regular atmospheric air, will typically contain relatively high amounts of moisture, which is often problematic for currently available technologies in cases involving further processing into more concentrated CO2 streams by, for example, CO2 liquefaction. Thus, compression of CO2 in the presence of large amounts of water produces fluids that cause severe corrosion of pipeline and well materials. While most of the water in a typical gas mixture obtained from DAC can be separated from the CO2 by cooling and condensation, additional drying is typically required to reduce the water content from about 2-4% to below 500 ppm.

[0008] In contrast, the method and system of the present invention rely on pressurized water scrubbing to separate substantially all of the CO2 from other components of a gas mixture (G1) (such as other gases that are part of a gas mixture typically obtained from a DAC system), the gas mixture comprising at least 70% and at most 90% CO2 by volume. Thus, unlike currently known processes for further purification of a CO2-containing gas stream obtained from a DAC, the method and system of the present invention do not require additional drying to reduce the water content from 2-4% to below 500 ppm. Thus, in the case of a gas mixture originating from a direct air capture (DAC) system, the first gas mixture (G1) preferably comprises at least 80% and at most 90% CO2 by volume and may have a relative humidity of up to 20% to 100% (i.e., it may be saturated with H2O at a given temperature and pressure), and there is no problem in handling a gas mixture (G1) having a water content above 500 ppm. The CO2-charged water (W4) thus obtained can then be transferred, for example, to injection wells for permanent removal from the atmosphere by solution capture and subsequent mineral capture by water chemical reactions, thereby achieving permanent sequestration by mineral storage.

[0009] Alternatively, the water stream (W4) rich in dissolved CO2 can be conveyed to a system for desorbing CO2 dissolved in the second water stream (W4), for example by reducing the pressure, thereby desorbing at least part of the CO2 dissolved in the water to produce a concentrated and purified CO2 stream, which can be used for other purposes, such as producing fuels or surface carbonization.

[0010] As a further alternative, if the first water stream (W2) is based on seawater, the CO2 charged water stream (W4) can be collected and stored for subsequent use, for example, for transporting the captured CO2 for utilization or for delivering the captured CO2 for permanent or intermediate storage.

[0011] In order to optimize the use of water resources, in case the CO2-containing gas stream (G1) is obtained from a DAC, the source of water in the method and system according to the invention may be condensate of air originating from the DAC system.

[0012] For geological storage, the method and system according to the invention may rely on bringing the gas mixture (G1) into contact with a water flow (W2) in the form of groundwater coming from a geological reservoir, and then conveying the resulting water flow (W4) rich in dissolved CO2 to an injection system for injecting the second water flow (W4) into the same geological reservoir for mineral storage of CO2.

[0013] In case the CO2-containing gas stream (G1) is obtained from a DAC, any water used as the first water stream (W2) in the process and system of the present invention may be used in the DAC system, for example as an energy source, before being transferred to the process and system of the present invention.

[0014] Compared to methods and systems that rely on removing water by drying (or cooling and condensing) and then liquefying CO2 by compression, the method and system according to the present invention generally reduce the total power demand of the process of separating CO2 from a gas mixture containing CO2. The method and system of the present invention are relevant to all applications that require water-soluble CO2 or purified gaseous CO2, and reduce the steps of drying, liquefaction and CO2 vaporization / regasification, which are specific to known processes for treating gas mixtures containing CO2 derived from, for example, DAC systems. Relative to known processes for separating CO2 from gas mixtures containing CO2, this simplification reduces both equipment requirements and generally reduces energy consumption, which in turn reduces the necessary capital costs and operating expenses of the method and system according to the present invention compared to the prior art. Background Art

[0015] CO2 is a gas that has historically been released in large quantities in a wide range of industrial processes, such as burning fossil fuels and producing cement, aluminum and steel. As a greenhouse gas, CO2 in the atmosphere is a key driver of climate change.

[0016] Achieving net-zero CO2 emissions is essential to mitigating climate change. In addition to deep emissions cuts, CO2 removal technologies will need to be deployed to address hard-to-abate emissions, such as aviation emissions, and to remove CO2 that has already been emitted. Net negative emissions pathways are needed to limit global warming to 1.5°C or less by the second half of the 21st century.

[0017] Direct Air Capture (DAC) technology extracts CO2 directly from the atmosphere. The separated CO2 can then be safely and permanently stored deep underground or converted into products through utilization processes.

[0018] The most established forms of DAC rely primarily on two different approaches to capture CO2 from the air: liquid and solid DAC.

[0019] In one aspect, a liquid DAC system passes air through a chemical solution (eg, a hydroxide solution) which removes the CO2.

[0020] Solid DAC technology, on the other hand, utilizes a solid sorbent filter that chemically bonds to the CO2.

[0021] Regardless of the specific technology used, capturing CO2 from the atmosphere by direct air capture for subsequent storage or use is currently expensive. For example, the concentration of CO2 in the atmosphere is much lower than that in the flue gas from a power station or cement plant. This results in relatively high energy requirements relative to other CO2 capture technologies and applications. The specific costs and energy requirements vary depending on the type of technology used. However, in most current scenarios, the captured CO2 (whether by solid or liquid DAC) needs to be released from the material in which it is captured, and since none of the currently known DAC technologies can produce 100% pure CO2, the resulting gas mixture needs to be further purified by subsequently removing water and compressing at high pressure. These steps increase the capital cost (due to the need for additional equipment, such as compressors) and operating expenses (for running the compressors) of most current DAC plants.

[0022] In the 2050 net-zero emissions scenario envisioned as part of the Paris Agreement, DAC must be scaled up to capture more than 85 Mt CO2 / yr by 2030 and ~980 Mt CO2 / yr by 2050. This level of deployment will require additional large-scale demonstrations to perfect the technology and reduce capture costs. DAC is therefore an evolving technology area and is considered essential to enable the management of climate change. However, as mentioned above, at the current stage of development, the main limitation to the large-scale implementation of DAC technology is the energy requirements of the system: DAC technology is very energy intensive and relies on carbon-neutral energy resources. Strategies to minimize energy consumption are therefore a key step in scaling up DAC technology to the required Gt scale.

[0023] A major part of the energy requirement of most known DAC systems is the preparation of the CO2-rich gas stream resulting from the initial DAC step for geological storage or for utilization steps taken after the capture process, for example, in the form of energy required for liquefaction by compression.

[0024] Even though DAC technologies are becoming quite diverse, most of the earliest and more mature technologies are based on adsorption / desorption processes, as mentioned above. In these processes, CO2 adsorption is carried out without pretreatment of the incoming air stream, and CO2 desorption is carried out by a temperature-vacuum-swing (TVS) process. During this process, the pressure in the system is reduced and the temperature is increased, thereby releasing the captured CO2. After a cooling phase, the entire process is repeated. The gas stream obtained by such a process inevitably has a variable chemical composition, and the exact concentration of CO2 in the resulting CO2 / air gas mixture depends on the operating parameters of the system. However, in most cases, the resulting gas mixture, even if enriched in CO2, must be subjected to additional treatment steps before injection, for example, for geological storage or utilization.

[0025] One way to separate the CO2 from other gases in the gas mixture leaving the DAC system is by means of liquefaction. In this process, the gas mixture is cooled and compressed, and any N2, O2 and Ar with a boiling point lower than CO2 are discharged from the system, resulting in the production of pure liquid CO2, which can be transported to geological storage or supplied to a utilization process. The energy demand for forming liquid CO2 by pressurizing pure CO2 gas to its liquefaction pressure is high. For gas mixtures that also include other gases besides CO2, the energy demand is even higher. If the final desired product of a given process is gaseous CO2, additional energy in the form of heat is required to convert liquid CO2 into its gaseous counterpart. One application of this is when the CO2 captured by the DAC process will be dissolved in water and injected into the subsurface for immediate dissolution capture and subsequent mineral storage. In addition, the gas mixture from DAC usually contains air and moisture, which must be separated from CO2 before compression and subsequent storage / utilization. Therefore, if the purification and compression steps of the conventional DAC process can be avoided, the overall energy consumption of CO2 capture post-processing and, therefore, per ton of CO2 actually captured for, e.g., geological storage, can be significantly reduced.

[0026] In addition to the conventional DAC processes described above, it has also been proposed to capture CO2 from atmospheric air for subsequent geological storage through multiple stages of aeration (dissolving the gas into water) and subsequent degassing (stripping the gas from the water), until a high concentration of CO2 remains of sufficient quality for sequestration. However, since these methods rely on the ability to treat the relevant gas mixture and water at very low temperatures, i.e., in order to be effective, they are to be carried out at temperatures where the water is as cold as possible, they also suffer from relatively high total energy consumption per ton of CO2 actually captured for possible geological storage.

[0027] The method and system of the present invention provide a solution to this problem by avoiding the purification and compression steps of the conventional DAC process and by avoiding any need to cool the associated gas mixture and water. This is achieved by absorbing substantially all of the relatively soluble CO2 gas from the relatively impure gas mixture typically obtained in the conventional DAC process into a water stream at near ambient temperature, i.e., at a temperature between about 10 and about 50°C, under moderately increased pressure. Thus, the inventors of the present invention have for the first time described a system and a method that meet the need for lower energy consumption and simpler construction and operation, the method for separating substantially all of the CO2 from a first gas mixture (G1) derived from, for example, a conventional DAC system, which relies on contacting the gas mixture (G1) with a first water stream (W2), thereby producing a second water stream (W4) that has been enriched in dissolved CO2 compared to the first water stream (W2) and a pressurized gas stream (G3) that has been depleted of substantially all of the CO2 compared to the flow of the first gas mixture (G1).

[0028] For example, if the first water flow (W2) is in the form of groundwater from a geological reservoir, the produced water flow (W4) can be transported to an injection system for injection into the geological reservoir and subsequent storage of the CO2 contained therein in the geological reservoir.

[0029] Alternatively, if the gas mixture (G1) comprises less than 10% by volume, such as less than 8%, 6% or 4%, of any one or more gases having a solubility in water equal to or greater than that of carbon dioxide (CO2) at the applied pressure and temperature, or having a solubility in water of 0.5 to 2.5 g per kg of water at a pressure of 1 atm and a temperature between 10 and 70°C, the resulting water stream (W4) can be conveyed to a system for desorbing or desorbing CO2 dissolved in the water stream (W4), thereby generating a concentrated and purified CO2 stream and a third water stream (W5), which can be recycled to the flow of the first water stream (W2) at a point before the first water stream (W2) contacts the gas mixture (G1).

[0030] Further alternatively, if the first water stream (W2) is in the form of seawater, the water stream (W4) may be collected and stored for subsequent use, for example, for transporting the captured CO2 for utilization or for delivering the captured CO2 for permanent or intermediate storage.

[0031] If the water stream (W2) used in the method or system according to the invention originates from, for example, a geological storage formation, it can also be used as a source of thermal energy to power the first part of the DAC process before being transferred to the method and system of the invention. In such an embodiment, the overall requirement for external energy input of the DAC process combined with the method of the invention will be lower than the sum of the external energy input required when the DAC and the method of the invention are each used separately.

[0032] Moreover, in contrast to conventional processes that rely on DAC, the methods and systems of the present invention do not rely on the addition of, for example, chemicals, as they leave relatively insoluble O2, N2 and Ar gases in the pressurized gas (G3), which has been depleted of substantially all CO2 compared to the flow rate of the first gas mixture (G1) and can then be discharged from the system.

[0033] CO2 is captured by contacting the entire gas stream (G1) with a water stream (W2). However, since the solubility of different gases in the gas stream (G1) varies greatly, this will require a large amount of water in many cases. For example, at 293K (about 20C) and 1 atmosphere (about 1 bar), the solubility of relatively soluble CO2 is 0.169g per 100g of water, while the solubility of relatively insoluble N2, O2 and Ar is only 0.0019, 0.0043 and 0.0062g per 100g of water, respectively. Therefore, in the method and system of the present invention, when measured in kg / s, the flow rate of water (W2) is usually at least 10 times to 135 times the flow rate of the flow of the first pressurized gas mixture (G1) when measured in kg / s.

[0034] Taking into account the differences in gas solubility, the method and system of the present invention ensure that substantially all of the CO2 can be separated from the other gases in the first gas stream (G1) by absorbing it into a first water stream (W2) to produce a second water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2), and a second pressurized gas stream (G3) depleted of substantially all of the CO2 compared to the flow rate of the first gas mixture (G1).

[0035] In a preferred embodiment of the invention, a first water stream (W2) is in the form of groundwater from a geological reservoir, and a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2) is conveyed to an injection system for injecting said second water stream (W4) into the same geological reservoir for mineral storage of CO2. In a particularly preferred embodiment of this method and system, they will rely only on resources in the form of electricity and water, said water being supplied by the storage formation itself or as condensate from the air of the DAC from which the first gas stream (G1) is produced.

[0036] Therefore, combining DAC technology with the above-mentioned preferred and particularly preferred embodiments of the present invention reduces the overall resource requirements of the process of permanently removing CO2 from atmospheric air and converting it into solid carbonate minerals, making it a more advantageous option for application in combating climate change.

[0037] In another embodiment of the method and system according to the present invention, if the gas mixture (G1) comprises less than 10% by volume, such as less than 8%, 6% or 4%, of any one or more gases whose solubility in water at the applied pressure and temperature is equal to or higher than the solubility of carbon dioxide (CO2), or has a solubility in water of 0.5 to 2.5 g per kg of water at a pressure of 1 atm and a temperature between 10 and 70°C, the produced water stream (W4) can be conveyed to a system for desorbing or desorbing CO2 dissolved in the water stream (W4), thereby generating a stream of concentrated and purified CO2 and a third water stream (W5), which can be recycled to the flow of the first water stream (W2) at a point before the first water stream (W2) contacts the gas mixture (G1).

[0038] In another embodiment of the method and system according to the present invention, wherein the first water flow (W2) is in the form of seawater, the water flow (W4) can be collected and stored for subsequent use, for example, for transporting the captured CO2 for utilization or for transporting the captured CO2 for permanent or intermediate storage. Summary of the invention

[0039] Liquid and supercritical CO2 are commonly stored and transported commercially, and their compositional integrity can be guaranteed. Given its low viscosity, high density and low critical temperature (31°C) and pressure (74 bar), efficient transportation of CO2 is possible. However, the liquefaction of CO2 as a purification step, and the possible need to remove water from the CO2-rich gas mixture produced by the DAC process prior to liquefaction, are (one or more) energy-intensive processes, which, in addition to the energy requirements of the DAC process itself, may also lead to slowing down the scale-up of such schemes as a method of mitigating climate change. In response to these challenges, the methods and systems of the present invention achieve an efficient direct air capture and storage / utilization chain by avoiding the liquefaction step and any possible need to remove water.

[0040] In addition, the simplicity of the method and system of the present invention relative to known processes for separating CO2 from CO2-containing gas mixtures (e.g., gas mixtures obtained from DAC) results in reduced equipment requirements, which in turn reduces the capital costs and operating expenses required for the method and system according to the present invention compared to the methods and systems of the prior art.

[0041] In a preferred embodiment of the present invention, the method and system can be optimized to provide storage pathways for CO2 that are respectively localized in reactive rock formations, tailings, and highly alkaline industrial slag.

[0042] In order to solve one or more of the above problems, in a first aspect of the present invention, there is provided a method for separating substantially all of CO2 from other components of a first gas mixture (G1), the first gas mixture (G1) comprising:

[0043] - at least 70% and at most 90% by volume of carbon dioxide (CO2),

[0044] The method comprises the following steps:

[0045] - pressurizing said first gas mixture (G1) to a pressure between 10 and 50 bar,

[0046] - bringing said pressurized first gas mixture flow (G1) into contact with a first water flow (W2), said first water flow having a pressure between 10 and 50 bar and a flow rate, measured in kg / s, of 10 to 135 times the flow rate, measured in kg / s, of said first pressurized gas mixture flow (G1),

[0047] - absorbing substantially all of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), thereby

[0048] -produce:

[0049] - a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and

[0050] - a second pressurized gas flow (G3) which has been depleted of substantially all CO2 compared to said flow of said first gas mixture (G1).

[0051] In a preferred embodiment, the first gas mixture (G1) will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm and / or a relative humidity between 20% and 100% (ie it may be saturated with H2O).

[0052] In a preferred embodiment of the method according to the above first aspect of the present invention, the first gas mixture (G1) is pressurized to a pressure between 20 and 40 bar, the first water flow (W2) is in the form of groundwater from a geological reservoir, and the method further comprises the following steps:

[0053] - conveying said second water flow (W4), which is richer in dissolved CO2 than said first water flow (W2), to an injection system for injecting said second water flow (W4) into said geological reservoir for mineral storage of CO2.

[0054] In another preferred embodiment of the method according to the above first aspect of the present invention, the first gas mixture (G1) is pressurized to a pressure between 20 and 40 bar, the first gas mixture (G1) comprises less than 10% by volume, such as less than 8%, 6% or 4% of any one or more gases, which have a solubility in water equal to or higher than the solubility of carbon dioxide (CO2) at the applied pressure and temperature, or have a solubility in water of 0.5 to 2.5 g per kg of water at a pressure of 1 atm and a temperature between 10 and 70° C., and the method further comprises the following steps:

[0055] - conveying the second water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2) to a system for desorbing or stripping the CO2 dissolved in the second water stream (W4), thereby

[0056] -generate:

[0057] -CO2 flow, and

[0058] - a third water stream (W5) which has been depleted in dissolved CO2 compared to the second water stream (W4).

[0059] - Recirculating said third water stream (W5) into the flow of said first water stream (W2) at a point before said first water stream (W2) comes into contact with said stream of said pressurized first gas mixture (G1).

[0060] In another preferred embodiment of the method according to the first aspect of the present invention, the first gas mixture (G1) is pressurized to a pressure between 10 and 20 bar, the first water flow (W2) is in the form of seawater, and

[0061] Wherein, the method further comprises the following steps:

[0062] - Collecting said second water stream (W4), enriched in dissolved CO2 compared to said first water stream (W2), for subsequent transport or transmission to permanent or intermediate storage.

[0063] In a particularly preferred embodiment of the method according to the above-mentioned first aspect of the invention, the first gas mixture (G1) is received from a direct air capture unit (DAC) or a unit designed to capture and / or concentrate a CO2-containing gas mixture emitted from an industrial plant or power plant. Insofar as the first gas mixture (G1) originates from a direct air capture (DAC) system, preferably, the first gas mixture will comprise at least 80% and at most 90% CO2 by volume and may have a water content higher than 500 ppm and / or a relative humidity between 20% and 100% (i.e., it may be saturated with H2O).

[0064] In the context of the present invention, the term separation is understood as any means of separating or keeping separate the different components of a mixture, for example any means of isolating or extracting one component of a mixture from other components of the mixture.

[0065] In the context of the present invention, the term separating substantially all of the CO 2 from the other components of the first gas mixture (G1) is understood as separating or extracting substantially all of the CO 2 in the first gas mixture from the other components of the gas mixture.

[0066] In the context of the present invention, separating substantially all of the CO2 from the other components of the first gas mixture (G1) is understood as separating at least 95%, such as at least 96%, such as at least 97%, i.e. such as preferably at least 98% and even more preferably at least 99% of the CO2 in the first gas mixture from the other components of the gas mixture.

[0067] In the context of the present invention, the term transport is understood as any means of transporting a liquid (eg water) or a gas (eg a gas mixture) from one location to another, for example by pumping.

[0068] In the context of the present invention, the terms recirculation, recirculated and recirculating are understood as any means of causing a liquid or gas flow in a given process flow to circulate again, or the action or process of causing a liquid or gas flow to circulate again in a given process flow, for example, by transporting a liquid (e.g., water) or a gas (e.g., a gas mixture) from a downstream position of a given forward flow of the liquid or gas to an upstream position of the same forward flow of the liquid or gas, for example, by pumping.

[0069] In the context of the present invention, the term flow is understood as a substance (e.g., water or gas) moving at a given speed in a given direction at a certain flow rate, which can be given as a volume flow rate or mass flow rate. The volume flow rate is the volume of a fluid or gas passing a given point per unit time, and is usually represented by the symbol Q (sometimes V). The SI unit of volume flow rate is m 3 / s. Therefore, volume flow rate is equal to volume / time. On the other hand, mass flow rate is the mass of fluid or gas passing through a given point per unit time. The SI unit of mass flow rate is kg / s.

[0070] In the context of the present invention, the term water source or water is understood as any kind of water, such as, for example, water condensed from the air, groundwater, ocean water / seawater, spring water, geothermal condensate or brine (geothermal water), or surface water from a river, stream or lake.

[0071] In the context of the present invention, the term injection well is understood as any kind of structure that provides the possibility of placing fluids or gases deep underground or just into the ground in a downward direction, such as, for example, devices for placing fluids in or below rock formations (such as basalt or basalt stone) and porous rock formations (such as sandstone or limestone) or shallow soil layers.

[0072] In the context of the present invention, a gas mixture containing CO2 is understood to be any gas mixture in which the relative content of CO2 is higher than the relative content of CO2 in the atmosphere. In a particularly preferred embodiment of the present invention, the gas mixture containing CO2 comprises at least 70% by volume and at most 90% carbon dioxide (CO2), such as at least 75% by volume and at most 90% carbon dioxide (CO2), such as at least 80% by volume and at most 90% carbon dioxide (CO2), such as at least 85% by volume and at most 90% carbon dioxide (CO2). In a particularly preferred embodiment of the invention, the CO2-containing gas mixture has a water content higher than 500 ppm and / or a relative humidity between 20% and 100% (i.e. it will be partially or completely saturated with H2O), such as at least 0.05% by volume of H2O, such as at least 0.1% by volume of H2O, such as at least 0.15% by volume of H2O, such as at least 0.20% by volume of H2O, such as at least 0.25% by volume of H2O, such as at least 0.5% by volume of H2O, such as at least 0.75% by volume of H2O, such as at least 1% by volume of H2O, such as at least 1.25% by volume of H2O. Preferably, the CO2-containing gas mixture according to the invention comprises at least 80% and at most 90% by volume of CO2 and has a water content higher than 500 ppm, i.e. at least 0.05% by volume of H2O.

[0073] In the context of the present invention, the term hydraulic is understood as the pressure of the hydraulic fluid, which exerts this pressure in all directions in a container, well, hose or anywhere it is present in. Hydraulic pressure can cause flow in a hydraulic system when the fluid flows from high pressure to low pressure.

[0074] Pressure is measured in the SI unit Pascal (Pa), which is one Newton per square meter (1N / m 2 ) or 1kg / (m·s 2 ) or 1J / m 3 Other commonly used units of pressure are pounds per square inch, or more precisely, pounds-force per square inch (abbreviation: psi) and bar. In SI units, 1 psi is approximately equal to 6895 Pa, and 1 bar is equal to 100,000 Pa.

[0075] In the context of the present invention, the term partial pressure of a gas (CO2) or just pressure is understood as the nominal pressure of said given gas in a gas mixture if this given gas itself occupies the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas mixture is the sum of the partial pressures of the component gases in the mixture.

[0076] In the context of the present invention, the terms pressurize and pressurized are understood as the process of reaching and maintaining a pressure above the environment, for example a pressure above atmospheric pressure, such as between 15 and 45 bar, such as between 16 and 44 bar, such as between 17 and 43 bar, such as between 18 and 42 bar, such as between 19 and 41 bar, for example, 25 to 40 bar. It is worth noting that the terms pressurize and pressurized are not to be interpreted in the context of the present invention as meaning to compress a given gas or a given gas mixture into its liquid state, which would mean, for a given gas or a given gas mixture, subjecting it to a pressure above a certain threshold at a given temperature.

[0077] In the context of the present invention, the term contacting (eg, bringing a gas stream into contact with a water stream) is understood as bringing something into contact with something else, i.e., two or more things touch, physically interact or are associated with each other.

[0078] In the context of the present invention, the term absorption (e.g., absorbing gas into water) is understood as a physical or chemical phenomenon or process in which atoms, molecules or ions enter a bulk phase (e.g., a liquid or solid material). Such an example would be gas-liquid absorption (also referred to as scrubbing), which is an operation in which a gas mixture is contacted with a liquid, the purpose of which is to preferentially dissolve one or more components of the gas mixture and provide a solution thereof in a liquid. In principle, there are 2 types of absorption processes: physical absorption and chemical absorption, depending on whether any chemical reaction occurs between the solute and the solvent (absorbent). In a process similar to the process of the present invention, water is used as an absorbent, and only a chemical reaction rarely occurs between the absorbent and the solute, and therefore the process is generally referred to as physical absorption. However, in the process of changing the pH of a water absorbing agent by adding an alkali or an acid, depending on the chemical properties of the solute, the absorption in water may be accompanied by a rapid and irreversible neutralization reaction in the liquid phase, and then the process may be referred to as chemical absorption or reactive absorption. Thus, chemical reactions induced by, for example, pH changes can be used to increase absorption rates, increase the absorption capacity of a solvent, increase selectivity to preferentially dissolve only certain components of a gas mixture, and / or convert hazardous components of a gas mixture into safe or safer compounds.

[0079] In the context of the present invention, the term producing (eg producing a water flow or a pressurized gas flow) is understood as causing, causing, generating, producing or generating something, eg a water flow or a pressurized gas flow.

[0080] In the context of the present invention, injecting / reinjecting or inject / reinject is understood as forcibly introducing / reintroducing something into something else, such as forcing a fluid into an underground structure.

[0081] In the context of the present invention, the term geological reservoir is understood as a fracture in an underground structure (e.g., basalt rock) that expands in directions other than upward and downward, which structure provides a flow path for water injected into an injection well according to the present invention and may include so-called geothermal reservoirs. In the present context, the term geothermal reservoir is understood as a fracture in hot rock that expands in directions other than upward and downward and provides a flow path for injected water from a well.

[0082] Thus, a method is provided for separating substantially all of the CO2 from the remainder of a first gas mixture by contacting the first gas mixture (G1) with a first water stream (W2), thereby producing a water stream (W4) enriched in dissolved CO2 and thereby preparing the gas for later storage, processing or use.

[0083] In one embodiment, the treatment may be based, for example, on the injection of a water stream (W4) rich in dissolved CO2 into a geological system or reservoir, where it forms chemical bonds through water-rock reactions. Thus, water-rock reactions that already occur in natural geological systems may be exploited by injecting a water stream (W4) rich in dissolved CO2 into a geological system or reservoir. Separating CO2 by dissolving CO2 in a water stream and injecting it below the surface is considered an ideal method for reducing the concentration of CO2 in the atmosphere. In a particularly preferred embodiment of this embodiment involving the treatment of CO2, the first water stream (W2) may be in the form of groundwater from the same geological system or reservoir.

[0084] In one embodiment, the CO2-containing gas mixture (G1) further comprises at least one of the following gases: O2, N2 and / or Ar, and the method for separating substantially all of the CO2 gas from the remaining gases contained in the CO2-containing gas mixture (G1) comprises directing the CO2-containing gas mixture (G1) comprising at least one of said O2, N2 and / or Ar gases through an absorption tower, where the CO2 is contacted with a water stream (W2) to separate the dissolved CO2 from the remaining sparingly soluble O2, N2 and / or Ar gases. In this way, a simple way is provided for separating CO2 from the remaining sparingly soluble gases, which are retained in a second pressurized gas stream (G3), which has been depleted of substantially all of the CO2 compared to the flow rate of the first gas mixture (G1).

[0085] In one embodiment, the remaining gas in the second pressurized gas stream (G3) leaving the absorption tower is conveyed to a system in which energy is recovered by expanding the gas, thereby converting kinetic energy into useful energy with the goal of improving the efficiency of the entire system.

[0086] In one embodiment, the remaining gas in the second pressurized gas stream (G3) leaving the absorption tower is diverted towards the inlet of the DAC after expansion to ambient pressure in order to improve the efficiency of the entire system. This approach is applied if the CO2 concentration in the remaining gas mixture leaving the absorption tower is significantly higher than the CO2 concentration of air.

[0087] In one embodiment, the water stream (W4) rich in dissolved CO2 is transferred to an evaporator where the CO2 is dissolved from the water by releasing the pressure, thereby producing a CO2 stream suitable for utilization and a third water stream (W5) which is depleted in dissolved CO2 compared to (W4). The resulting water stream (W5) is then recycled to the flow of the first water stream (W2) before it is contacted with the stream of the pressurized first gas mixture (G1), with the purpose of being reused in the absorption tower.

[0088] In a second aspect of the present invention, there is provided a system for separating substantially all of the CO2 from other components of a first gas mixture (G1), the first gas mixture (G1) comprising:

[0089] - at least 70% and at most 90% by volume of carbon dioxide (CO2),

[0090] The system comprises the following:

[0091] - means for pressurizing said first gas mixture (G1) to a pressure between 10 and 50 bar,

[0092] - means for contacting said pressurized first gas mixture flow (G1) with a first water flow (W2), said first water flow having a pressure between 10 and 50 bar and a flow rate, measured in kg / s, of 10 to 135 times the flow rate, measured in kg / s, of said first pressurized gas mixture flow (G1), and

[0093] - means for absorbing substantially all of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), and producing:

[0094] - a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and

[0095] - a second pressurized gas flow (G3) which has been depleted of substantially all CO2 compared to said flow of said first gas mixture (G1).

[0096] In a preferred embodiment, the first gas mixture (G1) will comprise at least 80% CO2 by volume and have a water content higher than 500 ppm, ie at least 0.05% H2O by volume.

[0097] In a preferred embodiment of the system according to the second aspect of the present invention, the system is used for:

[0098] - bringing said pressurized first gas mixture flow (G1) into contact with a first water flow (W2), said first water flow having a pressure between 10 and 50 bar and a flow rate, measured in kg / s, of 10 to 135 times the flow rate, measured in kg / s, of said first pressurized gas mixture (G1), and

[0099] - for absorbing substantially all of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), and producing:

[0100] - a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and

[0101] - has been depleted by substantially

[0102] The device for the second pressurized gas stream (G3) of all CO2 is an absorption tower.

[0103] In another particularly preferred embodiment of the system according to the above second aspect of the present invention, the system further comprises means for:

[0104] - obtaining said first water flow (W2) in the form of groundwater coming from a geological reservoir, and

[0105] - conveying said second water flow (W4), which is richer in dissolved CO2 than said first water flow (W2), to an injection system for injecting said second water flow (W4) into said geological reservoir for mineral storage of CO2.

[0106] In another particularly preferred embodiment of the system according to the above second aspect of the present invention, the system further comprises means for:

[0107] - conveying the second water stream (W4), which is enriched in dissolved CO2 compared to the first water stream (W2), to a system for desorbing or stripping the CO2 dissolved in the second water stream (W4), thereby generating a CO2 stream and a third water stream (W5), which is depleted in dissolved CO2 compared to the second water stream (W4), and

[0108] - Recirculating said third water stream (W5) into the flow of said first water stream (W2) at a point before said first water stream (W2) comes into contact with said stream of said pressurized first gas mixture (G1).

[0109] It should be noted that the term water according to the present invention may mean condensate of air, fresh water, water from geothermal wells, brine (geothermal water), seawater, etc. Therefore, the water source may be any type of water. Likewise, the CO2-containing gas mixture (G1) comprising at least 70% and at most 90% CO2 may originate from any source, such as a conventional power plant, a geothermal power plant, an industrial process, a gas separation station, etc. However, preferably, the CO2-containing gas mixture (G1) comprising at least 70% and at most 90% CO2 originates from a DAC process. Insofar as the first gas mixture (G1) originates from a direct air capture (DAC) system, preferably, the first gas mixture will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0110] In general, the various aspects of the invention may be combined and coupled in any possible way within the scope of the invention. These and other aspects, features and / or advantages of the invention will become apparent and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0111] Several embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which

[0112] Figure 1 A flow chart of a method according to the invention for separating substantially all of the CO2 from other components of a first gas mixture (G1) comprising at least 70% and at most 90% CO2 by volume, wherein the CO2-containing gas mixture (G1) also comprises at least one of O2, N2 and / or Ar gases, such as a gas mixture from a DAC. Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0113] Figure 2 A system is shown according to the invention for separating substantially all of the CO2 from other components of a first gas mixture (G1) comprising at least 70% and at most 90% CO2 by volume, wherein the CO2-containing gas mixture (G1) also contains at least one of O2, N2 and / or Ar gases, such as a gas mixture from a DAC. Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0114] Figure 3An absorber tower and injection well are shown in accordance with the system and method according to the present invention.

[0115] Figure 4 A method is shown according to the invention for separating CO2 from a first gas mixture (G1) comprising at least 70% and at most 90% of CO2, by contacting it with a first water stream (W2) coming from a geological system or reservoir (in an absorption tower at 20-40 bar), thereby producing a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), which is then reinjected into the same geological system or reservoir. Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0116] Figure 5 A method for separating CO2 from a first gas mixture (G1) comprising at least 70% and at most 90% CO2 according to the invention is shown, by contacting it with a first water stream (W2) coming from a geological system or reservoir (in an absorption tower at 20-40 bar), thereby producing a second water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2), and conveying the second water stream (W4) to a system for desorbing or desorbing the CO2 dissolved in the second water stream (W4), thereby generating a CO2 stream and a third water stream (W5), which has been depleted in dissolved CO2 compared to the second water stream (W4). In certain embodiments, the water stream (W5) obtained from the treatment / storage or utilization of CO2 in the water stream (W4) can be reused as the water stream (W2) contacted with the stream of the pressurized first gas mixture (G1).

[0117] Figure 6 The recommended relationship between water flow rate and water temperature for a feed gas stream comprising 80% CO2 in a process according to the invention is shown. This illustrates that the absorption of CO2 in water is temperature dependent, since CO2 is more soluble at lower temperatures than at higher temperatures. The water flow rates shown include a 1.3X design factor.

[0118] Figure 7 The relationship between the water flow rate required to absorb 98% of the CO2 (in a feed gas stream comprising 80% CO2) and the absorber column operating pressure in a process according to the invention is shown. The water flow rates shown include a 1.3X design factor.

[0119] Figure 8The power / energy consumption (in kWh) required to absorb 1 tonne of CO2 in a water flow initially having a near-ambient temperature (i.e. 20°C in the specific example) at a constant elevated pressure (20 bar) for a scenario involving a variable water flow rate is shown.

[0120] Fig. 9 The power / energy consumption (in kWh) required to absorb 1 tonne of CO2 in a water flow initially having a temperature close to ambient (i.e. 20°C in the specific embodiment) at a constant water flow rate (254000 kg / hr, equivalent to approximately 70.56 kg / s) in a scenario involving a variable elevated pressure is shown. DETAILED DESCRIPTION

[0121] Figure 1 A flow chart of a method according to the invention for separating substantially all of the carbon dioxide (CO2) from other components of a CO2-containing gas mixture (G1), said CO2-containing gas mixture comprising at least 70% and at most 90% CO2 by volume, and also containing at least one of O2, N2, Ar gases, such as a gas stream from a DAC. Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume, and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0122] It should be noted that in the context of the present invention, the CO2-containing gas mixture (G1) comprising at least 70% and at most 90% CO2 should not be interpreted as being limited to a gas stream from a DAC. However, for simplicity, the following will relate to an embodiment in which the CO2-containing gas mixture (G1) is derived from a DAC, and therefore, to an embodiment in which the gas stream may further comprise, but is not limited to, one or more gases selected from O2, N2 and Ar. However, a skilled person will be able to easily change the specific conditions described in the following embodiments to provide specific conditions applicable to other embodiments, for example, an embodiment in which the CO2-containing gas mixture (G1) comprising at least 70% and at most 90% CO2 is not derived from a DAC. Insofar as the gas mixture (G1) is derived from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0123] As about Figure 2Discussed in more detail, in a CO2-containing gas mixture (G1) comprising at least 70% and up to 90% CO2, substantially all of the CO2 is separated from any O2, N2, and Ar contained in, for example, the gas stream (G1), preferably by directing the gas stream through an absorption tower, in which substantially all of the CO2 is dissolved in a liquid, typically a water stream (W2), and in this way separated from the remaining more insoluble O2, N2, and / or Ar gases. Subsequently, the resulting water stream (W4) comprising dissolved CO2 is directed, for example, to an injection well for processing / storage or to other processes for utilizing the CO2. In certain embodiments, the water stream (W5) obtained by processing / storing or utilizing the CO2 in the water stream (W4) can be reused as the water stream (W2).

[0124] Reference Figure 2 The present invention relates in particular to a method and system for separating substantially all of the CO2 from other components of a first gas mixture (G1), the first gas mixture comprising:

[0125] - at least 70% and at most 90% by volume of carbon dioxide (CO2),

[0126] The method comprises the following steps:

[0127] o pressurizing the first gas mixture (G1) to a pressure between 10 and 50 bar,

[0128] o contacting said pressurized first gas mixture flow (G1) with a first water flow (W2), said first water flow having a pressure between 10 and 50 bar and a flow rate, when measured in kg / s, of 10 to 135 times the flow rate, when measured in kg / s, of said flow of said first pressurized gas mixture (G1),

[0129] o absorbing substantially all of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), thereby

[0130] oGenerates:

[0131] a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and

[0132] - A second pressurized gas flow (G3) which has been depleted of substantially all CO2 compared to said flow of said first gas mixture (G1).

[0133] Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, ie at least 0.05% H2O by volume.

[0134] like Figure 1 As shown, and as described above, the second pressurized gas stream (G3) leaving the absorption tower can be conveyed to a system for recovering energy by expanding the gas, thereby converting kinetic energy into useful energy, with the aim of improving the efficiency of the entire system. Similarly, if the CO2 concentration in the remaining gas mixture (G3) leaving the absorption tower is significantly higher than the CO2 concentration of the air, it can be diverted towards the inlet of the DAC after expansion to ambient pressure, with the aim of improving the efficiency of the entire system.

[0135] exist Figure 2 Not shown is the step of transporting the water stream (W4) rich in dissolved CO2 to an injection well for injecting the water stream (W4) into a geological reservoir, or to a system for utilization purposes.

[0136] Figure 3 The step of conveying said water stream (W4) rich in dissolved CO2 to an injection well for injecting said water stream (W4) into a geological reservoir is shown.

[0137] Figure 5 The use of a water stream (W4) for utilization purposes is shown, wherein at least a portion of the water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2) is conveyed to a system for desorbing or stripping CO2 dissolved in the second water stream (W4), thereby generating a CO2 stream and a third water stream (W5) depleted in dissolved CO2 compared to the second water stream (W4). In certain embodiments, the water stream (W5) resulting from the treatment / storage or utilization of CO2 in the water stream (W4) can be reused as the water stream (W2) in contact with the stream of the pressurized first gas mixture (G1).

[0138] In a particularly preferred embodiment of the method according to the invention, the pressure of the pressurized gas mixture (G1) comprising at least 70% and at most 90% by volume of CO2 and at least one of H2, N2 and / or Ar is between 15 and 45 bar, such as between 16 and 44 bar, such as between 17 and 43 bar, such as between 18 and 42 bar, such as between 19 and 41 bar, such as between 20 and 40 bar or between 15 and 40 bar, such as between 16 and 40 bar, Such as between 17 and 40 bar, such as between 18 and 40 bar, such as between 19 and 40 bar or between 20 and 45 bar, such as between 20 and 44 bar, such as between 20 and 43 bar, such as between 20 and 42 bar, such as between 20 and 41 bar, i.e. such as above 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 bar and below 40, 39, 38, 37, 36, 35, 34, 33, 32, 31 or 30 bar.

[0139] In a further particularly preferred embodiment of the method according to the present invention, the temperature of the gas stream (G1) comprising at least 70% and at most 90% CO2 by volume is close to the environment, i.e. such as between 10 and 50°C, such as between 12 and 48°C, such as between 14 and 46°C, such as between 16 and 44°C, such as between 18 and 42°C, such as between 20 and 40°C, or such as between 15 and 50°C, such as between 16 and 50°C, such as between 17 and 50°C, such as between 18 and 50°C, such as between 19 and 50°C, such as 20 to 50°C, or such as between 10 and 45°C, such as between 11 and 45°C, such as between 12 and 45°C, such as between 13 and 45°C, such as between 14 and 45°C, or such as between 15 and 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30°C.

[0140] In a further particularly preferred embodiment of the method according to the present invention, the temperature of the water stream (W2) is close to the environment, i.e. such as between 10 and 50°C, such as between 12 and 48°C, such as between 14 and 46°C, such as between 16 and 44°C, such as between 18 and 42°C, such as between 20 and 40°C, or such as between 15 and 50°C, such as between 16 and 50°C, such as between 17 and 50°C, such as between 18 and 50°C, such as between 19 and 50°C, such as between 20 and 50°C, or such as between 10 and 45°C, such as between 11 and 45°C, such as between 12 and 45°C, such as between 13 and 45°C, such as between 14 and 45°C, such as between 15 and 45°C, or such as between 15 and 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30°C.

[0141] In a further particularly preferred embodiment of the method according to the invention, the pressure of the water stream (W2) is between 15 and 45 bar, such as between 16 and 44 bar, such as between 17 and 43 bar, such as between 18 and 42 bar, such as between 19 and 41 bar, such as between 20 and 40 bar or between 15 and 40 bar, such as between 16 and 40 bar, such as between 17 and 40 bar, such as between 18 and 40 bar, such as between 19 and 40 bar or between 20 and 45 bar, such as between 20 and 44 bar, such as between 20 and 43 bar, such as between 20 and 42 bar, such as between 20 and 41 bar, i.e. such as above 15, 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 bar and below 40, 39, 38, 37, 36, 35, 34, 33, 32, 31 or 30 bar. In a particularly preferred embodiment of the method according to the invention, the pressure of the water stream (W2) is about 2 to 7 bar, such as 3 to 6 bar, such as 4 to 5 bar, higher than the pressure of the pressurized gas mixture (G1), which comprises at least 70% and at most 90% by volume of CO2 and at least one of O2, N2 and / or Ar. Thus, if the pressure of the pressurized gas mixture (G1) comprising at least 70% and at most 90% by volume of CO2 and at least one of O2, N2 and / or Ar is about 20 bar, the pressure of the water stream (W2) should preferably be about 22 to 27 bar. Nevertheless, the skilled person will recognize that the optimal pressure difference between the pressure of the pressurized gas mixture (G1) comprising at least 70% and at most 90% by volume of CO2 and at least one of O2, N2 and / or Ar and the pressure of the water stream (W2) will depend, for example, on the tower height of the applicable absorption tower and the pressure drop in the applicable water distribution system, just as it depends on the location at which the pressure is measured in a given system.

[0142] In a further particularly preferred embodiment of the method according to the present invention, the flow rate of the gas mixture (G1) is between 0.05 and 0.5 kg / s, such as between 0.1 and 0.45 kg / s, such as between 0.15 and 0.4 kg / s, such as between 0.16 and 0.35 kg / s, such as between 0.17 and 0.3 kg / s, such as between 0.18 and 0.25 kg / s, such as between 0.05, 0.06, 0.08, 0.1, 0.12 or 0.14 kg / s and 0.5, 0.4, 0.3 or 0.2 kg / s.

[0143] In a further particularly preferred embodiment of the method according to the present invention, the flow rate of the water stream (W2) is between 5 and 15 kg / s, such as between 6 and 14 kg / s, such as between 7 and 13 kg / s, such as between 8 and 12 kg / s, such as between 5, 6, 7 or 8 kg / s and between 15, 14, 13 or 12 kg / s.

[0144] In a further particularly preferred embodiment of the method according to the invention, the flow rate of the water flow (W2) when measured in kg / s is at least 10 to 135 times, such as at least 15 times, such as at least 20 times, such as at least 25 times, such as at least 30 times, such as at least 35 times, such as at least 40 times, such as at least 45 times, the flow rate of the flow of the first pressurized gas mixture (G1) when measured in kg / s, that is, it is such as at least 11 times, such as at least 12 times, such as at least 13 times, such as at least 14 times, such as at least 16 times, such as at least 17 times, such as at least 18 times, such as at least 19 times, such as at least 46, such as at least 47, such as at least 48, such as at least 49, such as at least 50, such as at least 51 to 135 times the flow rate of the flow of the first pressurized gas mixture (G1) when measured in kg / s.

[0145] In a further particularly preferred embodiment of the method according to the invention, the flow rate of the water flow (W2), when measured in kg / s, is at least 10 to 135 times, such as at least 15 to 135 times, such as at least 20 to 135 times, such as at least 25 to 135 times, such as at least 30 to 135 times, such as at least 35 to 135 times, such as at least 40 to 135 times, such as at least 45 to 135 times, the flow rate of the flow of the first pressurized gas mixture (G1), when measured in kg / s, i.e. The flow rate of the flow of the first pressurized gas mixture (G1) at the above-mentioned temperature is such as at least 11 to 135 times, such as at least 12 to 134 times, such as at least 13 to 133 times, such as at least 14 to 132 times, such as at least 16 to 135 times, such as at least 17 to 134 times, such as at least 18 to 133 times, such as at least 19 to 132 times, such as at least 46 to 134 times, such as at least 47 to 133 times, such as at least 48 to 132 times, such as at least 49 to 131 times, such as at least 50 to 130 times.

[0146] In a further particularly preferred embodiment of the process according to the invention, said gas mixture (G1) comprising at least 70% and at most 90% CO2 by volume is a gas stream originating from a DAC. Insofar as the gas mixture (G1) originates from a direct air capture (DAC) system, it will comprise at least 80% and at most 90% CO2 by volume and have a water content higher than 500 ppm, i.e. at least 0.05% H2O by volume.

[0147] Moreover, in addition to the above method, the present invention also particularly relates to a system for separating substantially all of the CO2 from other components of a first gas mixture (G1), the first gas mixture comprising:

[0148] - at least 70% and at most 90% by volume of carbon dioxide (CO2),

[0149] The system comprises the following:

[0150] - means for pressurizing said first gas mixture (G1) to a pressure between 10 and 50 bar,

[0151] - means for contacting said pressurized first gas mixture flow (G1) with a first water flow (W2), said first water flow having a pressure between 10 and 50 bar and a flow rate of said first water flow, measured in kg / s, of 10 to 135 times, such as at least 15 times, such as at least 20 times, such as at least 25 times, such as at least 30 times, such as at least 35 times, such as at least 40 times, such as at least 45 times, i.e. of at least 11 times, such as at least 12 times, such as at least 13 times, such as at least 14 times, such as at least 16 times, such as at least 17 times, such as at least 18 times, such as at least 19 times, such as at least 46, such as at least 47, such as at least 48, such as at least 49, such as at least 50, such as at least 51 to 135 times the flow rate of said flow of said first pressurized gas mixture (G1) measured in kg / s , such as at least 10 to 135 times, such as at least 15 to 135 times, such as at least 20 to 135 times, such as at least 25 to 135 times, such as at least 30 to 135 times, such as at least 35 to 135 times, such as at least 40 to 135 times, such as at least 45 to 135 times, the flow rate of the flow of the first pressurized gas mixture (G1) when measured in kg / s, i.e., the flow rate of the first pressurized gas mixture (G1) when measured in kg / s The flow rate of the stream is such as at least 11 to 135 times, such as at least 12 to 134 times, such as at least 13 to 133 times, such as at least 14 to 132 times, such as at least 16 to 135 times, such as at least 17 to 134 times, such as at least 18 to 133 times, such as at least 19 to 132 times, such as at least 46 to 134, such as at least 47 to 133, such as at least 48 to 132, such as at least 49 to 131, such as at least 50 to 130 times, and

[0152] - means for absorbing substantially all of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), and producing:

[0153] a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and

[0154] - A second pressurized gas flow (G3) which has been depleted of substantially all CO2 compared to said flow of said first gas mixture (G1).

[0155] Although the present invention has been described and illustrated in detail in the drawings and the foregoing description, such description and illustration are to be considered illustrative or exemplary rather than restrictive; the present invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments may be understood and effected by a person skilled in the art in practicing the claimed invention by studying the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may perform the functions of multiple items recited in a claim. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be interpreted as limiting the scope.

[0156] Example

[0157] Example 1 :

[0158] A demonstration capture plant and injection system was designed for the DAC plant, connected to the SW Iceland Carbfix injection facility.

[0159] A gas stream with 80% CO2 and 20% air (including any H2O) from the DAC plant is directed to an absorption column where the CO2 is dissolved in water at elevated pressure (20 bar) at constant temperature (15-17°C).

[0160] The operating conditions for capturing water-soluble carbon dioxide (CO2) from a CO2-containing gas stream from a DAC are summarized as follows:

[0161] operate

[0162]

[0163]

[0164] scope:

[0165]

[0166] More than 95% of the CO2 is dissolved in water and injected deep into the bedrock at the site for mineralization.

[0167] The skilled person will readily appreciate that the above temperatures, flows and pressures are based on the specific conditions of the project in Hellisheiei, Iceland, and that these may be different taking into account other predetermined conditions regarding gas flows and temperatures. Similarly, the skilled person will readily appreciate that the associated water flow should be a certain ratio of the actual gas flow, which ratio should vary depending on the applicable pressure and temperature. In this context, the skilled person will be able to obtain, for example, Figure 6 It is understood from the recommended relationship between water flow rate and water temperature for a feed gas stream comprising 80% CO2 in the process according to the invention shown that CO2 absorption in water is temperature dependent, since CO2 is more soluble at lower temperatures than at higher temperatures. Likewise, the skilled person is able to Figure 7 The relationship between the water flow rate required for absorbing 98% of the CO 2 (in a feed gas stream comprising 80% of CO 2 ) in the process according to the invention and the operating pressure of the absorber column is found in .

[0168] Example 2 :

[0169] A demonstration system was designed to capture CO2 from a DAC plant and inject dissolved CO2 for mineral storage.

[0170] The gas stream from the DAC plant contains 80% CO2 and 20% air and is directed to the absorption tower at 20 bar using a dry compressor with a capacity of 832 kg / h. There, CO2 is dissolved in water at a constant temperature (15°C-17°C) under elevated pressure (20 bar).

[0171] Water is fed to the absorber by a submersible pump followed by a booster pump at 22 bar to compensate for the pressure losses encountered in the system and the height difference between the pump and the point where the water enters the tower. The same water supply is used to cool the gas compressor feeding the absorber. The used cooling water is transferred to the CO2-charged water stream leaving the absorber, resulting in an increase in the temperature of the water outlet relative to its inlet temperature.

[0172] For this system, water can also be passed directly to the injection well through the absorber to ensure stable injection conditions in the event of unstable operating conditions in the absorber. Maintaining an elevated pressure in the injection system prevents any CO2 exsolution downstream of the absorber and prevents sudden pressure and flow changes in the injection well during unstable gas supply.

[0173] The parameters of the stainless steel absorption tower are shown below.

[0174]

[0175] The operating conditions for capturing water-soluble carbon dioxide (CO2) from a CO2-containing gas stream from a DAC and achieving a CO2 capture efficiency of more than 98% using the parameters of the capture plant are summarized below. The table shows that 51.3 kg of water are required to capture 1 kg of CO2. This water carries the CO2 into the storage formation. The water is then pumped out of the storage formation and fed back into the system for reuse.

[0176] operate

[0177]

[0178]

[0179] scope:

[0180]

[0181] More than 98% of the CO2 is dissolved in water and injected deep into the bedrock of the site for mineralization (patent PCT / EP 2020 / 064306).

[0182] The skilled person will readily appreciate that the above temperatures, flows and pressures are based on the specific conditions of a particular DAC plant located at a particular location where those utility flows are available and that these may be different taking into account other predetermined conditions regarding gas flows and temperatures. Similarly, the skilled person will readily appreciate that the associated water flow should be a certain ratio of the actual gas flow, which ratio should vary depending on the applicable pressure and temperature. In this context, the skilled person will be able to obtain from e.g. Figure 6 It is understood from the recommended relationship between water flow rate and water temperature for a feed gas stream comprising 80% CO2 in the process according to the invention shown that CO2 absorption in water is temperature dependent, since CO2 is more soluble at lower temperatures than at higher temperatures. Likewise, the skilled person is able to Figure 7 The relationship between the water flow rate required for absorbing 98% of the CO 2 (in a feed gas stream comprising 80% of CO 2 ) in the process according to the invention and the operating pressure of the absorber column is found in .

[0183] Example 3 :

[0184] A demonstration system was designed to capture CO2 from a DAC plant using seawater and inject the dissolved CO2 into a shallow underground formation for immediate dissolved storage.

[0185] The gas stream from the DAC plant contains 80% CO2 and 20% air and is directed to the absorption column at a pressure of 10 bar using a liquid ring compressor with a capacity of 832 kg / h. There, CO2 is dissolved in water at a constant temperature (15°C) under elevated pressure (10 bar).

[0186] Water is fed to the absorber at 12 bar by a submersible pump followed by a booster pump to compensate for the pressure losses encountered in the system and the height difference between the pump and the location where the water enters the tower. The same water supply is used to cool the gas compressor feeding the absorber. The spent cooling water is transferred to the CO2-filled water stream (stream not shown in the figure) leaving the absorber, resulting in an increase in the temperature of the water outlet relative to its inlet temperature.

[0187] The same parameters of the stainless steel absorption tower as in Example 2 were used for the system.

[0188] The operating conditions for capturing water-soluble carbon dioxide (CO2) from a CO2-containing gas stream from a DAC and achieving a CO2 capture efficiency of more than 98% are summarized below using the parameters of a capture plant. The table shows that approximately 100 to 130 kg of water are required to capture 1 kg of CO2. This water carries the CO2 into the storage formation.

[0189] The system is designed to operate in coastal or offshore areas. Seawater for the process can be supplied from shallow depths, in which case only the operating pressure of the absorber and the electricity to overcome the pressure losses in the system need to be achieved. In addition, the gas-filled water can be processed into shallow wells on the seabed to maintain CO2 dissolution at a level where the hydrostatic pressure in the storage formation is higher than 10 bar (deeper than 102m). The final arrangement of the injection wells and the depth at which the CO2-filled fluid leaves the casing must take into account the scale of the injection activity and the reservoir structure and conditions. The parameters of the absorber are shown below.

[0190]

[0191] Operation parameters

[0192]

[0193]

[0194] As with the above embodiment, the skilled person will readily appreciate that the above temperature, flow rate and pressure are based on the specific conditions of this embodiment and that these may be different given other predetermined conditions regarding gas flow rate and temperature. Similarly, the skilled person will readily appreciate that the associated water flow rate should be a certain ratio of the actual gas flow rate, which ratio should vary depending on the applicable pressure and temperature. In this context, the skilled person will appreciate from, for example, Figure 6 It is understood from the recommended relationship between water flow rate and water temperature for a feed gas stream comprising 80% CO2 in the process according to the invention shown that CO2 absorption in water is temperature dependent, since CO2 is more soluble at lower temperatures than at higher temperatures. Likewise, the skilled person is able to Figure 7The relationship between the water flow rate required for absorbing 98% of the CO 2 (in a feed gas stream comprising 80% of CO 2 ) in the process according to the invention and the operating pressure of the absorber column is found in .

[0195] Embodiment 4:

[0196] A demonstration system was designed to capture CO2 from a DAC plant and inject dissolved CO2 for mineral storage.

[0197] The gas stream from the DAC plant contains 80% CO2 and 20% air, with a flow rate of 4749 kg CO2 per hour (equivalent to about 1.32 kg / s), and is directed to the absorption tower. Then about 99.85% of the CO2 is absorbed in a water stream with an initial temperature of 20°C:

[0198] - or respectively at a constant elevated pressure (20 bar) with a variable water flow rate and a temperature range of 20° C. to 1° C. in the absorption column,

[0199] - or respectively at a variable elevated pressure, at a constant water flow rate (254000 kg / hr, equivalent to about 70.56 kg / s), at a temperature in the absorption tower ranging from 20°C to 1°C.

[0200] Figure 8 and Fig. 9 The power / energy consumption (in kWh) required to absorb 1 ton of CO2 under various process conditions is shown. Figure 8 Scenarios involving variable condensate / water flow rates (filled circles) at constant elevated pressure (20 bar). Fig. 9 Scenarios involving variable elevated pressure (solid circles) at a constant condensate / water flow rate (254000 kg / hr, corresponding to approximately 70.56 kg / s).

[0201] Figure 8 and 9 The individual energy consumptions for any cooling down of the water (chiller) (hollow squares), for the compressor (solid triangles), for the condensate / water pump (crosses) and for the injection pump (hollow circles), as well as the total (solid diamonds) power / energy consumption (in kWh) are shown separately, and the actual values ​​are shown in the table below.

[0202] Operating parameters, constant condensate / water flow.

[0203]

[0204] Operating parameters, constant pressure:

[0205]

[0206] From the above table and Figure 8 and 9 It can be noted that if the water / condensate stream (initially at ambient temperature) has to be cooled to a temperature below about 10°C, the power / energy consumption (in kWh) required for any cooling down of the water / condensate (cooler, open squares) becomes significant in both cases (i.e., reaching more than about 33% of the total energy consumption (solid diamonds)). Therefore, these results indicate that for any system based on absorbing CO2 in a water / condensate stream at near ambient temperature (i.e., 20°C in this case), its total power / energy consumption (in kWh) will increase significantly, and therefore, the efficiency with which CO2 can be absorbed will decrease significantly if the water / condensate temperature is to be significantly reduced to below 10°C.

Claims

1. A method for separating at least 98% of CO2 from other components of a first gas mixture (G1) received from a direct air capture unit (DAC) or a unit designed to capture and / or concentrate a CO2-containing gas mixture emitted from an industrial plant or power plant, wherein: The first gas mixture (G1) comprises: - 70 to 90% by volume of carbon dioxide (CO2), The method comprises the following steps: o pressurizing the first gas mixture (G1) to a pressure between 15 and 45 bar, o contacting said pressurized first gas mixture flow (G1) with a first water flow (W2), said first water flow having a pressure between 15 and 45 bar and a flow rate, when measured in kg / s, of 10 to 135 times the flow rate, when measured in kg / s, of said flow of said first pressurized gas mixture (G1), o absorbing at least 98% of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), thereby oGenerates: a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and - A second pressurized gas flow (G3) which has been depleted of at least 98% of CO2 compared to said flow of said first gas mixture (G1).

2. The method according to claim 1, wherein: - pressurizing said first gas mixture (G1) to a pressure between 20 and 40 bar, - said first water flow (W2) is in the form of groundwater coming from a geological reservoir, and The method further comprises the step of transporting the second water stream (W4) richer in dissolved CO2 than the first water stream (W2) to an injection system for injecting the second water stream (W4) into the geological reservoir to store CO2 as minerals.

3. The method according to claim 1, wherein: - pressurizing said first gas mixture (G1) to a pressure between 20 and 40 bar, - the first gas mixture (G1) comprises less than 10% by volume in total of any one or more gases having a solubility in water of 0.5 to 2.5 g per kg of water at a pressure of 1 atm and a temperature between 10 and 70° C., and Wherein, the method further comprises the following steps: - conveying the second water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2) to a system for desorbing or stripping the CO2 dissolved in the second water stream (W4), thereby -generate: -CO2 flow, and a third water stream (W5) which is depleted in dissolved CO2 compared to the second water stream (W4), - Recirculating said third water stream (W5) into the flow of said first water stream (W2) at a point before said first water stream (W2) comes into contact with said stream of said pressurized first gas mixture (G1).

4. The method according to claim 1, wherein: - pressurizing said first gas mixture (G1) to a pressure between 10 and 20 bar, - the first water flow (W2) is in the form of seawater, and Wherein, the method further comprises the following steps: - Collecting said second water stream (W4), enriched in dissolved CO2 compared to said first water stream (W2), for subsequent transport or transmission to permanent or intermediate storage.

5. A method according to any one of the preceding claims, wherein: The temperature of the first gas mixture (G1 ) is between 10 and 50°C, such as between 12 and 48°C, such as between 15 and 35°C, such as 20°C.

6. A method according to any one of the preceding claims, wherein: The temperature of the first water stream (W2) is between 10 and 50°C, such as between 10 and 45°C, such as between 15 and 40°C, such as between 16 and 35°C, such as between 17 and 30°C, such as between 18 and 25°C, such as 20°C.

7. A method according to any one of the preceding claims, wherein: The flow rate of the first gas mixture (G1) is between 0.05 and 0.5 kg / s, such as between 0.1 and 0.4 kg / s, such as between 0.15 and 0.3 kg / s, such as 0.2 kg / s.

8. A method according to any one of the preceding claims, wherein: The flow rate of the first water flow (W2) is between 1.5 and 15 kg / s, such as between 3 and 12 kg / s, such as between 5 and 11 kg / s, such as 10 kg / s.

9. A method according to any one of the preceding claims, wherein: The first gas mixture (G1) has a water content higher than 500 ppm, ie at least 0.05% H2O by volume.

10. A system for separating at least 98% of CO2 from other components of a first gas mixture (G1) received from a direct air capture unit (DAC) or a unit designed to capture and / or concentrate a CO2-containing gas mixture emitted from an industrial plant or power plant, wherein The first gas mixture (G1) comprises: - 70 to 90% by volume of carbon dioxide (CO2), The system comprises the following: - means for pressurizing said first gas mixture (G1) to a pressure between 15 and 45 bar, - means for contacting said pressurized first gas mixture flow (G1) with a first water flow (W2), said first water flow having a pressure between 15 and 45 bar and a flow rate, measured in kg / s, of 10 to 135 times the flow rate, measured in kg / s, of said first pressurized gas mixture flow (G1), and - means for absorbing at least 98% of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), and producing: a second water stream (W4) enriched in dissolved CO2 compared to said first water stream (W2), and - A second pressurized gas flow (G3) which has been depleted of at least 98% of CO2 compared to said flow of said first gas mixture (G1).

11. The system according to claim 10, wherein: Used for: - contacting said pressurized first gas mixture flow (G1) with said first water flow (W2), and - for absorbing at least 98% of said CO2 from said flow of said first pressurized gas mixture (G1) into said first water flow (W2), and producing: i. a second water stream (W4) enriched in dissolved CO2 compared to the first water stream (W2), and ii. said second pressurized gas stream (G3) having been depleted in at least 98% of CO2 compared to said flow of said first gas mixture (G1), said device being an absorption tower.

12. The system of claim 10 or 11, further comprising means for: - obtaining said first water flow (W2) in the form of groundwater coming from a geological reservoir, and - conveying said second water flow (W4), which is richer in dissolved CO2 than said first water flow (W2), to an injection system for injecting said second water flow (W4) into said geological reservoir for mineral storage of CO2.

13. The system of claim 10 or 11, further comprising means for: - conveying the second water stream (W4), which is enriched in dissolved CO2 compared to the first water stream (W2), to a system for desorbing or stripping the CO2 dissolved in the second water stream (W4), thereby generating a CO2 stream and a third water stream (W5), which is depleted in dissolved CO2 compared to the second water stream (W4), and - Recirculating said third water stream (W5) into the flow of said first water stream (W2) at a point before said first water stream (W2) comes into contact with said stream of said pressurized first gas mixture (G1).

Images