FIELD The invention relates to a method defined in claim 1 and to an apparatus defined in claim 11 for recovering carbon dioxide, and to the use of the meth od as defined in claim 16. BACKGROUND

Various methods for separating and recovering carbon dioxide from a gaseous stream or air are known in the prior art. Additionally, in document WO 2017/140954 the recovery of carbon dioxide from air of a building and utilization of it as a raw material are disclosed.

OBJECT

An object of the invention is to disclose a new type of method for recovering carbon dioxide. In addition, an object of the invention is to disclose a new type of apparatus for recovering carbon dioxide. In addition, an object of the invention is to facili tate and speed up the collection of carbon dioxide from a sorbent material and to improve energy effi ciency in connection with recovery of carbon dioxide. In addition, an object of the invention is to disclose a method and an apparatus for cleaning the air of a building or a property. In addition, an object of the invention is to provide purer carbon dioxide for fur ther utilization.

SUMMARY

The method and the apparatus for recovering carbon dioxide and the use of the method according to the invention are characterized by features presented in the claims.

Carbon dioxide is captured directly from air by means of a recovery device in which the carbon di oxide is adsorbed from the air to a sorbent material and is recovered by releasing it from the sorbent ma terial.

DETAILED DESCRIPTION

In the method for recovering carbon dioxide, air, e.g. air of a building or a property, is fed through a carbon dioxide recovery device in which car bon dioxide is adsorbed from the air to a sorbent ma terial for cleaning the air in an adsorption stage. Vacuum conditions are arranged into the recovery de vice in a vacuum formation stage after the feeding of air through the recovery device has been stopped. Af ter this, carbon dioxide, such as industrial grade carbon dioxide or high purity grade carbon dioxide, is fed via a heating device to the recovery device and through the sorbent material for preheating the sorbent material in a preheating stage. Next, heated carbon dioxide, such as the fed carbon dioxide and carbon dioxide released from the sorbent material, is circulated through the sorbent material of the recov ery device and carbon dioxide released from the sorbent material, i.e. desorbed carbon dioxide, is collected in a carbon dioxide collecting stage. In the method, the fed carbon dioxide is used for preheating the sorbent material. The circulated carbon dioxide or carbon dioxide which may contain released water vapor functions as a heat-transfer agent for releasing car bon dioxide from the sorbent material, i.e. for the desorption of carbon dioxide.

The apparatus comprises at least one recovery device including a sorbent material through which air is conducted and in which carbon dioxide is adsorbed from the air to the sorbent material, at least one vacuum formation device for arranging vacuum condi tions into the recovery device after feeding of the air through the recovery device has been stopped, at least one carbon dioxide feeding device for feeding carbon dioxide to the recovery device, at least one heating device for heating carbon dioxide, such as the fed carbon dioxide and/or carbon dioxide to be circu lated, before feeding the carbon dioxide through the sorbent material, at least one circulating device for circulating carbon dioxide in the recovery device, such as from the outlet of the recovery device back to the inlet of the recovery device, and at least one collecting device for recovering carbon dioxide re leased from the sorbent material.

In one embodiment the apparatus comprises at least one air feeding device for conducting air to the carbon dioxide recovery device, e.g. from a building or a property to the recovery device, for removing carbon dioxide from the air.

As the recovery device, any separating or re covery device which is known per se may be used, in which separating or recovery device the recovery or separation of carbon dioxide from air is based on an adsorption method. The air is conducted through the recovery device. If necessary, the air may be fed to and/or through the recovery device by means of a suit able feeding device.

In one embodiment the carbon dioxide recovery device is a DAC (direct air capture) device. The DAC device refers to a device by means of which carbon di oxide may be removed directly from air. In this connec tion the DAC device used comprises a sorbent material for adsorbing carbon dioxide to said material.

In one embodiment the apparatus comprises at least one DAC device as the recovery device. In one embodiment the apparatus comprises more than one DAC device.

As the sorbent material in the recovery de vice, any sorbent material which is suited for the in tended use may be used. In one embodiment the sorbent material is an organic-inorganic hybrid sorbent. In one embodiment the sorbent material is an organic- inorganic hybrid sorbent which contains amines on po rous adsorbent carriers. In one embodiment the sorbent material used is a metal-organic framework (MOF). In one embodiment the sorbent material is selected so as to be suitable for the DAC device. In one embodiment the sorbent material may be arranged inside the recov ery device as at least one bed or layer or as more than one bed or layer, or in one embodiment the recov ery device may be filled with the sorbent material.

The duration of the adsorption stage for ad sorbing carbon dioxide from air to the sorbent material may vary, for example depending on the conditions of the adsorption stage, the amount of carbon dioxide in air and the recovery device used. In one embodiment the duration of the adsorption stage for adsorbing carbon dioxide from air to the sorbent material is determined so as to have a desired length. In one embodiment the duration of the adsorption stage for adsorbing carbon dioxide from air to the sorbent material is determined based on a desired time. In one embodiment the duration of the adsorption stage for adsorbing carbon dioxide from air to the sorbent material is selected according to when the ventilation system of the building or prop erty is in use or operates at least at normal power. In one embodiment the adsorption stage for adsorbing car bon dioxide from air to the sorbent material lasts for 8 - 10 hours. In one embodiment the temperature is 20 - 25 °C in the adsorption stage. In one embodiment the pressure is approximately 1 bar in the adsorption stage. In one embodiment, water is separated or re moved from air in connection with the carbon dioxide adsorption stage. Thereby moisture may be removed from the air. In the vacuum formation stage the vacuum may be formed into the recovery device by any device which is suited for the intended use, e.g. by a vacuum pump, a rotary vacuum pump, a constant volume flow rate vac uum pump or other suitable device. In one embodiment the temperature is 20 - 25 °C in the vacuum formation stage. In one embodiment the pressure is decreased in the vacuum formation stage such that the pressure is approximately 20 mbar or less than 20 mbar in the re covery device. In the vacuum formation stage, oxygen and/or nitrogen may be removed from the recovery de vice.

In the preheating stage, carbon dioxide, e.g. industrial grade or high purity grade carbon dioxide is fed to the recovery device. In this connection the carbon dioxide fed in the preheating stage to the re covery device refers to carbon dioxide which consists of carbon dioxide and does not substantially contain other gases and which does not have significant amounts of impurities. In the preheating stage, carbon dioxide is fed via the heating device to the recovery device and the sorbent material is heated in a controlled manner. In one embodiment the temperature is raised in the preheating stage such that the temperature is 60 - 90 °C in the recovery device after the preheating stage. In one embodiment the pressure is raised in the pre heating stage such that the pressure is approximately 0.8 - 1 bar in the recovery device.

As the heating device, any heating device or heater which is suited for the intended use may be used, such as a heating device external to the recov ery device, e.g. a radiant heater, a heat pump, an electric gas heater, a solar thermal heater or other suitable heater.

In one embodiment, carbon dioxide is fed in a preselected amount via the heating device to the re covery device in the preheating stage. In one embodi ment, carbon dioxide is fed via the heating device to the recovery device in such amount that the pressure of the recovery device or the partial pressure of the carbon dioxide will be a preselected pressure. In one embodiment, carbon dioxide is fed via the heating de vice to the recovery device in the preheating stage in such amount that the partial pressure of the carbon dioxide will be approximately 0.15 - 0.25 bar, in one embodiment approximately 0.2 bar, in the recovery de vice.

In one embodiment, by the heated carbon diox ide the surface of the sorbent material is heated in the preheating stage. In one embodiment, by the heated carbon dioxide the particles of the sorbent material, e.g. the surface of the particles, are heated in the preheating stage. In one embodiment, by the heated carbon dioxide the adsorbed carbon dioxide is heated in the sorbent material. In one embodiment the water contained in the sorbent material is heated when hot carbon dioxide is conducted through the recovery de vice and the water is vaporized, whereby the water is desorbed from the surface of the sorbent material. In one embodiment, by the heated carbon dioxide, at least the surface of the particles of the sorbent material and additionally the carbon dioxide and/or water con tained in the sorbent material are heated. Prefera bly, the adsorbed carbon dioxide is released from the sorbent material by the effect of heat.

When the preheating is done by means of the fed carbon dioxide, the collection of carbon dioxide from the sorbent material may be made more efficient, and at the same time purer carbon dioxide can be col- lected. Due to the preheating with carbon dioxide, an even temperature is provided fast in the sorbent mate rial without formation of hot temperature points in the sorbent material.

In the carbon dioxide collecting stage, part of the carbon dioxide may be collected and recovered, and part of the carbon dioxide may be circulated in the recovery device for making the desorption of car bon dioxide from the sorbent material more efficient.

In one embodiment, carbon dioxide is circu lated in the recovery device in the carbon dioxide collecting stage such that the partial pressure of carbon dioxide is maintained at a preselected pres sure, in one embodiment at a pressure of approximately 0.15 - 0.25 bar, e.g. at a pressure of 0.2 bar, in the recovery device.

In one embodiment the temperature is approxi mately 60 - 90 °C in the collecting stage in the recov ery device. In one embodiment the pressure is approxi mately 0.8 - 1 bar in the collecting stage in the re covery device.

In one embodiment, in the carbon dioxide col lecting stage the circulated carbon dioxide is heated by the heating device for keeping the temperature of the recovery device at a desired level. In one embodi ment, in the carbon dioxide collecting stage the car bon dioxide is circulated via the heating device with out heating the circulated carbon dioxide.

In one embodiment, at least part of the water vapor released in connection with the releasing of car bon dioxide is circulated together with carbon dioxide as a carbon dioxide-vapor mixture through the sorbent material of the recovery device, and at least part of the carbon dioxide released from the sorbent material is collected in the carbon dioxide collecting stage. In one embodiment a minor amount of vapor is added to the carbon dioxide, and the vapor is circulated together with the carbon dioxide in the recovery device. Primar ily, in the method, the same vapor is being circulated through the recovery device. In one embodiment the amount of vapor in relation to the amount of carbon di oxide is adjusted and preferably the amount of vapor in relation to the amount of carbon dioxide is predeter mined. With the circulated vapor the releasing of car bon dioxide from the sorbent material may be made more efficient. In one embodiment the amount of vapor in the carbon dioxide-vapor mixture is less than 20 vol-%. In one embodiment, at least part of the water vapor re leased in connection with the releasing of carbon diox ide is removed from the carbon dioxide to be circulat ed.

In one embodiment, carbon dioxide including vapor is fed via the heating device to the recovery device and through the sorbent material for accom plishing the preheating of the sorbent material. In one embodiment the amount of vapor in the carbon diox ide-vapor mixture is less than 20 vol-%. In one embodi ment the carbon dioxide-vapor mixture is circulated via the heating device and through the sorbent materi al of the recovery device and at least part of the carbon dioxide released from the sorbent material is collected in the carbon dioxide collecting stage.

In one embodiment the apparatus comprises at least one device or one means for collecting, i.e. re covering, carbon dioxide from the recovery device and for conducting it to storage or further treatment. As the means for collecting carbon dioxide from the re covery device and for conducting it to storage or fur ther treatment, any devices or means which are known per se and suited for the intended use may be used. As the collecting device for recovering carbon dioxide released from the sorbent material, any device which is known per se and suited for the intended use may be used. In one embodiment the apparatus comprises at least one compressor for recovering carbon dioxide from the recovery device. In one embodiment the appa ratus comprises at least one compressor for conducting carbon dioxide, such as dry carbon dioxide, to storage from the recovery device.

The duration of the collecting stage may vary. In one embodiment the carbon dioxide collecting stage for releasing carbon dioxide from the sorbent material and for collecting carbon dioxide lasts for approxi- mately 7 - 10 hours, in one embodiment approximately 8 hours. In one embodiment the preheating stage and the carbon dioxide collecting stage last for approximately 10 - 12 hours.

In one embodiment, water is removed from the carbon dioxide to be collected. In one embodiment, wa ter is removed from the carbon dioxide released from the sorbent material. In one embodiment, water is re moved from the released carbon dioxide after the re covery device. In one embodiment the apparatus com- prises at least one water separating device or carbon dioxide drying device which is arranged after the re covery device for removing water from the carbon diox ide to be recovered. In one embodiment, water is sepa rated or removed already from air in connection with the carbon dioxide adsorption stage. In one embodiment the water may be recovered or conducted to further treatment, e.g. electrolysis, in which oxygen and hy drogen may be formed from the water.

In one embodiment the sorbent material of the recovery device is cooled after collecting the carbon dioxide in a cooling stage. In one embodiment the sorbent material is cooled after collecting the carbon dioxide by means of an airflow. In connection with cooling performed by an airflow the sorbent material of the recovery device may be cleaned, e.g. by remov ing odorous gases or VOC gases. In one embodiment, by cooling the odour of ammonia is reduced in the recov ery device.

In one embodiment the temperature is de creased in the cooling stage such that the temperature is approximately 20 - 25 °C in the recovery device af ter the cooling stage. The pressure after the cooling stage is approximately 1 bar.

When the carbon dioxide has been collected from the sorbent material, the adsorption stage, the vacuum formation stage, the preheating stage and the carbon dioxide collecting stage as well as the possible cooling stage of the method are repeated for cleaning a new batch of air and for removing carbon dioxide from the air.

In one embodiment the apparatus comprises at least one control device for controlling the carbon di oxide recovery process and the different stages there of.

In one embodiment the apparatus comprises at least two recovery devices. The recovery devices may be arranged in parallel. Thereby in one device, carbon di oxide may be adsorbed from air, while in the other de vice, at the same time, carbon dioxide is recovered from the sorbent material.

In one embodiment, carbon dioxide is recovered from air, such as air to be conducted to a building, circulated in the building and/or air to be removed from the building. In one embodiment, carbon dioxide is recovered from air coming from a ventilation sys tem, such as HVAC (Heating Ventilation Air Condition ing). As an example the content of carbon dioxide in the air coming to the recovery device can be 300 - 600 ppm, and approximately 50 - 200 ppm in the air cleaned by means of the recovery device.

In this connection the building refers to any property or building, such as a residential building, an industrial building, a hall, an office space, a public building or other corresponding building, or a group of buildings consisting of more than one build ing.

In one embodiment the apparatus functions as a separate unit which is as a whole or the parts of which are easily movable and/or locatable to a desired site for use.

The method and the apparatus according to the invention may be used in the recovery of carbon diox ide, in the treatment of indoor air of a building, in the treatment of supply air of a building, in the treatment of exhaust air of a building, in the manu facture of a carbon dioxide product, in the manufac ture of hydrocarbons, in the manufacture of chemical or biological products and combinations thereof. In one embodiment, carbon dioxide is removed from supply air, circulated air of exhaust air of a building. The recovered carbon dioxide may be stored, used as a product or fed to a carbon dioxide treatment stage. The carbon dioxide recovered by the present method and apparatus, preferably pure carbon dioxide such as high purity grade or industrial grade carbon dioxide, may be stored for further use, or it may for example be bottled as a product to be used for a desired purpose or conducted to a desired process stage directly or via temporary storage. In one treatment embodiment, carbon dioxide is treated in a treatment stage by means of a hydrogen treatment, such as by means of hy drogen, for forming a chemical compound, e.g. for forming a hydrocarbon. In one embodiment the carbon dioxide is conducted to a hydrocarbon synthesis unit. In one embodiment the carbon dioxide is conducted to a methanation unit. In one embodiment the carbon dioxide is conducted to the manufacture of chemical or biolog ical products.

Due to the invention, carbon dioxide may be recovered efficiently from air. Additionally, pure carbon dioxide can be recovered from air, whereby the carbon dioxide may be used in applications requiring purity of carbon dioxide and pure hydrocarbons may be formed therefrom. The high-quality hydrocarbons may be used for example in applications requiring clean fuels.

Further, due to the invention the recovery of carbon dioxide may be accomplished without feeding va por and the apparatus does not require a vapor genera tor. Additionally, heating elements or heating pipes need not be located inside the recovery device or in connection with the sorbent material for heating the sorbent material. Due to the invention the sorbent ma terial may be heated evenly and quickly without for mation of hot temperature points in the sorbent mate rial. Also the cooling of the sorbent material may be accomplished quickly.

The apparatus according to the invention may be implemented easily and cost efficiently. Addition ally, by means of the invention, for example DAC re covery devices may be easily converted for efficient recovery of carbon dioxide. Additionally, the appa ratus may be easily added to buildings and building complexes.

LIST OF FIGURES

Fig. la-ld present one apparatus according to the invention and different process stages in the ap paratus, and

Fig. 2 presents an additional process stage in the apparatus according to Fig. la-ld.

EXAMPLES

The invention will be described in the fol lowing by way of detailed examples of its embodiments with reference to the accompanying figures. Example 1

The apparatus according to Fig. la - Id com prises one recovery device (2) which is a DAC device and which includes a sorbent material. Air (1) to be cleaned is conducted through the sorbent material of the recovery device (2) for adsorbing carbon dioxide present in the air to the sorbent material during an adsorption stage presented in Fig. la.

Further, the apparatus comprises a vacuum formation device (4) for arranging vacuum conditions into the recovery device (2) after feeding of the air (1) through the recovery device has been stopped. In a vacuum formation stage presented in Fig. lb, air (5) in the recovery device is sucked out and thereby the recovery device can also be purified of oxygen and hy drogen. In the vacuum formation stage the temperature is 20 - 25 °C, and the pressure is decreased such that the pressure is approximately 20 mbar or less than 20 mbar in the recovery device. In addition, the apparatus comprises a carbon dioxide feeding device for feeding industrial grade or high purity grade carbon dioxide (6) to the recovery device (2) and a heating device (8) for heating the industrial grade or high purity grade carbon dioxide (6) in a preheating stage presented in Fig. lc. From the heating device, carbon dioxide (9) is fed to the recovery device and through the sorbent material. The industrial grade or high purity grade carbon dioxide (6) is fed to the recovery device in the preheating stage in such amount that the partial pressure of the carbon dioxide will be a predetermined pressure, e.g. approximately 0.2 bar. After the preheating stage the temperature is 60 - 90 °C, and the pressure is approx imately 0.8 - 1 bar in the recovery device. Addition- ally, the apparatus comprises a circulating device for circulating carbon dioxide in the recovery device. Carbon dioxide (10) conducted out from the recovery device, which carbon dioxide comprises fed carbon di oxide and also carbon dioxide released from the sorbent material, may be circulated via the heating device back to the recovery device in the preheating stage. The circulated carbon dioxide may contain water vapor released in connection with the desorption of carbon dioxide. In one embodiment a minor amount of water vapor (7) may be fed to the carbon dioxide to be fed for making the desorption of carbon dioxide more efficient.

Further, the apparatus comprises a collecting device for recovering carbon dioxide (11) released from the sorbent material in a collecting stage pre sented in Fig. Id. In the collecting stage the temper ature is 60 - 90 °C, and the pressure is approximately 0.8 - 1 bar in the recovery device. The partial pres sure of the carbon dioxide is to be kept the same as in the preheating stage. In the collecting stage, part of the carbon dioxide (10) coming from the recovery device is circulated as a carbon dioxide flow (9) via the heating device (8) back to the recovery device and through the sorbent material, and part of the carbon dioxide (10) is collected as carbon dioxide (11) to be recovered. The carbon dioxide (11) to be recovered may be conducted through a drying device (14) for removing water from the carbon dioxide, and collected as a product (16) by means of a compressor (15). The carbon dioxide to be circulated may be heated in the heating device (8) or just conducted via the heating device.

Example 2

In this example, carbon dioxide is recovered in a process according to Example 1 and by the appa ratus presented in Fig. la-d, which apparatus compris es, after the carbon dioxide collecting stage (Fig. Id), a cooling stage which is presented in Fig. 2. The apparatus comprises at least one air feed ing device for conducting cooling air (12) through the carbon dioxide recovery device (2). Warmed-up, practi cally clean air (13) is conducted out from the recov ery device. In the cooling stage the temperature is decreased such that the temperature is approximately 20 - 25 °C in the recovery device after the cooling stage. The pressure after the cooling stage is approx imately 1 bar.

Example 3

In this example, carbon dioxide is recovered from air to be conducted to a building by means of the process according to Examples 1 and 2. In this example the recovery of carbon dioxide is performed such that the adsorption stage for adsorbing carbon dioxide from air to the sorbent material lasts for approximately 8 - 10 hours, the collecting stage for releasing carbon di oxide from the sorbent material and for collecting car bon dioxide lasts for approximately 8 - 9 hours and the whole recovery cycle, i.e. stages la-d and 2, lasts for 24 hours. Thereby the adsorption stage may be carried out for example during the day, such as during a work day, whereby cleaned air may be conducted to the build ing.

The method and the apparatus according to the invention are suitable as different embodiments to be used for recovering carbon dioxide in most different applications.

The invention is not limited only to the above-described examples, but many modifications are possible within the scope of the inventive idea de fined by the claims.