APPARATUS AND METHOD FOR THE SEPARATION AND STORAGE OF CO2 FOR METHANOL FUEL CELLS

Abstract

Apparatus for the capture and storage of carbon dioxide from the exhaust gases of at least one methanol fuel cell, comprising: • A fluidized bed reactor filled with sodium carbonate powder, • at least one exhaust gas inlet for feeding carbon dioxide-containing exhaust gas into the fluidized bed reactor, • at least one unit for water enrichment of the exhaust gas stream from the at least one methanol fuel cell, in order to saturate the exhaust gas with water, • at least one cooling unit, preferably in the fluidized bed area, which cools the water-enriched exhaust gas stream so that the water in the exhaust gas condenses and reacts with the carbon dioxide and sodium carbonate, • at least one sodium carbonate storage tank for storing the fresh sodium carbonate powder, • at least one sodium bicarbonate storage tank for storing saturated powder after the reaction has taken place in the fluidized bed and • at least one outlet, preferably in the form of a fresh air outlet, for the discharge of the post-reactionary exhaust gas from the fluidized bed reactor.

Description

[0001] The invention relates to an apparatus for separating and storing carbon dioxide from the exhaust gases of at least one methanol fuel cell according to the preamble of claim 1 and a method for separating and storing carbon dioxide from the exhaust gases of at least one methanol fuel cell according to the preamble of claim 7. TECHNICAL BACKGROUND

[0002] A fuel cell is a technical device categorized as an electrical energy source. It converts the chemical reaction energy of a continuously supplied fuel and an oxidant into electrical energy. Methanol is often used as the fuel because it represents an alternative, renewable energy carrier. Carbon dioxide is produced during the combustion or reforming of methanol. However, the amount of carbon dioxide is significantly less than with conventional fossil fuels such as gasoline or diesel.

[0003] There is great interest in emission-free energy sources, and achieving very low carbon dioxide emissions is sometimes relevant for political funding, for example in the commercial vehicle sector. However, machines powered by methanol are not completely emission-free, as carbon dioxide is released, as mentioned above. When methanol is used in a fuel cell, no pollutant emissions are produced. Therefore, carbon dioxide emissions are the only emission-relevant component of a methanol fuel cell.

[0004] Carbon dioxide is a commonly used raw material, employed, for example, in the production of plastics and fuels. However, producing high-purity carbon dioxide is complex, as it usually has to be separated from a gas mixture. For transport and storage, carbon dioxide is liquefied and stored in a pressure tank.

[0005] There are several methods for separating carbon dioxide from gas mixtures. However, almost all of these methods require a significant amount of local energy. After separation, the carbon dioxide is liquefied for space-saving transport and storage until needed. This liquefaction process requires additional local energy.

[0006] US 2020 / 0002183A1, US 4664893A, and US 4459272A each describe the capture of carbon dioxide by reaction with water and sodium carbonate in a reactor. US 9056780B2 and WO 93 / 11070A1 each describe the capture of carbon dioxide by reaction with water and trona in a reactor. THE TASK UNDERLYING THE INVENTION

[0007] Accordingly, the object of the invention is to provide a means by which carbon dioxide can be separated and stored from the exhaust gases of at least one methanol fuel cell without a high local energy input. INVENTIONAL SOLUTION

[0008] For this purpose, an apparatus for the separation and storage of carbon dioxide from the exhaust gases of at least one methanol fuel cell according to the preamble of claim 1 is proposed.

[0009] This apparatus includes at least one fluidized bed reactor in which a fluidized bed is built up, the fluidized bed reactor being filled with sodium carbonate powder.

[0010] Furthermore, the apparatus includes at least one exhaust gas inlet for feeding carbon dioxide-containing exhaust gas from the at least one methanol fuel cell into the fluidized bed reactor. Preferably, the exhaust gas stream fed in through this exhaust gas inlet is already saturated with water.

[0011] Furthermore, the apparatus comprises at least one unit for water enrichment of the exhaust gas stream from the at least one methanol fuel cell. Preferably, the apparatus is designed such that it can completely saturate the exhaust gas stream with water.

[0012] Furthermore, the apparatus includes at least one cooling unit, preferably located in the fluidized bed region, which cools the water-enriched exhaust gas stream. The water then condenses in the exhaust gas stream and can react with the carbon dioxide and sodium carbonate to form sodium bicarbonate.

[0013] Furthermore, the apparatus comprises at least one sodium carbonate storage tank for storing the fresh sodium carbonate powder and at least one sodium bicarbonate storage tank for storing saturated, post-reaction sodium bicarbonate powder after the reaction in the fluidized bed has been completed. Finally, the apparatus comprises at least one outlet, preferably in the form of a fresh air outlet, for the discharge of the post-reaction exhaust gas from the fluidized bed reactor. Preferably, the post-reaction exhaust gas contains no or substantially no carbon dioxide, no or substantially no pollutants, and no or substantially no remaining powder.

[0014] In this way, an apparatus can be provided in a simple manner with which the carbon dioxide is first separated from the exhaust gases of at least one methanol fuel cell and then this carbon dioxide is stored in powdered sodium bicarbonate in the sodium bicarbonate storage. FURTHER EDUCATION OPPORTUNITIES IN INVENTION

[0015] A preferred further development of the apparatus consists in the sodium carbonate storage being a powder tank with a downstream fluidized bed inlet, preferably in the form of a controllable and / or adjustable inlet valve to the fluidized bed reactor. The fluidized bed inlet is thus preferably located between the powder tank and the fluidized bed reactor and enables precise refilling of the fluidized bed reactor with sodium carbonate.

[0016] Furthermore, it is particularly preferred if the sodium bicarbonate storage tank is a powder tank with an upstream fluidized bed outlet, preferably in the form of a controllable and / or adjustable drain valve from the fluidized bed reactor. The fluidized bed outlet is thus preferably located between the powder tank and the fluidized bed reactor and enables targeted discharge of the post-reaction sodium bicarbonate from the fluidized bed reactor. Preferably, the sodium bicarbonate discharge line is located above the distributor plate.

[0017] Furthermore, it is particularly preferred if the cooling unit is at least partially located within the fluidized bed reactor or at least partially surrounding parts of the fluidized bed reactor and incorporates temperature control. Cooling of the exhaust gas stream must occur within the fluidized bed to enable the reaction described above. The temperature control is also preferably adjustable to allow for the separation of a desired amount of carbon dioxide. Temperature can be used to regulate the amount of carbon dioxide absorbed. Preferably, a control system is employed that maintains the temperature within the fluidized bed reactor precisely so that only a specific amount of carbon dioxide is stored. This allows for the targeted achievement of a political or technical target while minimizing powder consumption.

[0018] Furthermore, it is particularly preferred if the fluidized bed reactor has at least one distributor plate on which powdered sodium carbonate is located at least temporarily, and through which the exhaust gas stream, preferably saturated with water, from the at least one methanol fuel cell flows. The distributor plate can thus be used as a simple means of separating the powder from the exhaust gas stream and at which the exhaust gas stream can be mixed with the sodium carbonate powder.

[0019] Furthermore, it is particularly preferred if the apparatus includes a centrifugal separator upstream of the fresh air outlet, designed to separate any powder that may be carried from the fluidized bed reactor. This allows the post-reactionary exhaust gas to be easily cleaned of powder, which can then preferably be released into the environment. A tangential cyclone separator is preferably used for this purpose. Generally, complete separation of powder from the exhaust gas stream is not possible, and fine powder remains in the post-reactionary exhaust gas stream downstream of the centrifugal separator. ANOTHER TASK UNDERLYING THE INVENTION

[0020] Furthermore, the object of the invention is to provide a method by which carbon dioxide can be separated and stored from the exhaust gases of a methanol fuel cell without high local energy input. THE FURTHER INVENTIONAL SOLUTION

[0021] This problem is solved by a process that captures carbon dioxide from exhaust gases and binds it in a carrier material. This carrier material stores the carbon dioxide until it is needed. Then, the carrier material can be regenerated and reused. In this way, the carbon dioxide can also be transported in bound form. Sodium carbonate is used as the carrier material, which reacts with water and carbon dioxide to form sodium bicarbonate. Sodium carbonate is completely regenerable. It is inexpensive and poses little risk to humans and the environment. Therefore, carbon dioxide can be stored in the carrier material for extended periods without any problems.

[0022] The corresponding procedure comprises the following steps: - Transfer of the carbon dioxide-containing exhaust gas stream from at least one methanol fuel cell into a fluidized bed reactor. This transfer can be actively driven by transport air or guided automatically by the natural movement of the exhaust gas stream. - Enrichment of the exhaust gas stream with water until the exhaust gas stream is saturated. This preferably takes place before the exhaust gas stream is fed into the fluidized bed reactor. - Feeding the water-saturated exhaust gas stream into a fluidized bed filled with sodium carbonate powder. - Cooling of the water-saturated exhaust gas stream, causing the water in the exhaust gas stream to condense and react with the carbon dioxide and sodium carbonate to form sodium bicarbonate. The corresponding balanced chemical equation for this is: Na₂CO₃ + H₂O + CO₂ = 2 NaHCO₃ - Storage of the carbon dioxide in bound form as sodium bicarbonate, preferably in a sodium bicarbonate storage tank after transfer to this tank from the fluidized bed reactor.

[0023] The reaction taking place in the fluidized bed reactor is exothermic, which is why no additional energy is required for the separation of carbon dioxide. Since the carbon dioxide is stored in the support material and sodium bicarbonate is formed almost "automatically," no additional energy is needed for compression.

[0024] In a fluidized bed, the carbon dioxide-containing exhaust gas flows through the sodium carbonate powder. The gas stream is warm and saturated with water vapor. Within the fluidized bed, the gas cools, and the water condenses. This allows the sodium carbonate to react with the liquid water and the carbon dioxide. Exhaust gases at temperatures above 100 °C can also be used. At these temperatures, the reaction of sodium carbonate produces Wegscheider salt. Wegscheider salt also absorbs carbon dioxide.

[0025] If the gas is not yet saturated with water, this can occur before the fluidized bed reactor in the apparatus. The gas flows through water and thus comes into contact with it, becoming saturated. Furthermore, the gas can be heated more efficiently through contact with water, preferably using warm water. For this purpose, the water is preferably heated and replenished.

[0026] Cooling within the fluidized bed reactor removes the energy from the reaction within the fluidized bed. The amount of water condensing from the gas stream can be precisely controlled by adjusting the inlet and outlet temperatures. This also allows for precise control over the amount of carbon dioxide removed.

[0027] After the powdered sodium carbonate has absorbed carbon dioxide and sodium bicarbonate has formed, it is removed from the fluidized bed and fresh sodium carbonate powder is added. The removed powder can then be stored, for example, in a dry container as a sodium bicarbonate reservoir.

[0028] A carbon dioxide source can also be created in a simple way. If the carbon dioxide stored in the sodium bicarbonate is needed, the saturated powder can be heated to over 120 °C. This adds the reaction energy back, and the reaction proceeds in the opposite direction. The separated carbon dioxide can be obtained in a high purity and used as a raw material.

[0029] Sodium bicarbonate can also be used as a raw material, for example as an ingredient in baking powder. This eliminates the need for energy regeneration, as the sodium bicarbonate is used directly.

[0030] The regeneration of sodium bicarbonate requires a significant amount of energy. Due to renewable energy sources, electricity generation is not constant. When the power grid is underutilized, the energy could be used to regenerate the powder. When the grid is operating at full capacity, the carbon dioxide remains stored in the powder. During regeneration, the carbon dioxide is then liquefied and stored. FURTHER TRAINING OPPORTUNITIES FROM THE INVENTION

[0031] A preferred further development of the process is that the process can be carried out on board vehicles, preferably with one or more tanks each for sodium carbonate storage and sodium bicarbonate storage, and the fluidized bed reactor on board the vehicle, wherein the sodium bicarbonate storage can be emptied after the journey and new sodium carbonate can be added. This provides a flexible system that reliably generates energy on board a vehicle without emissions.

[0032] Furthermore, it is particularly advantageous if the process can also be used to remove pollutants other than carbon dioxide from the exhaust gas stream, especially for cleaning combustion gases. The sodium bicarbonate produced in the fluidized bed can absorb many pollutants from combustion. Sodium bicarbonate is frequently used to reduce pollutant emissions from combustion. Thus, the device can remove not only carbon dioxide but also pollutants from the exhaust gas, thereby eliminating the need for an additional cleaning stage. Exhaust gases containing water are particularly suitable, as they already contain water. With these exhaust gases, the temperatures can be selected so that no further water needs to be added.

[0033] Furthermore, it is particularly advantageous if the process is suitable for stationary use in an emergency power system that uses methanol as an energy carrier, allowing the carbon dioxide produced during a power outage to be stored and later regenerated. The apparatus can be used in an emergency power system. If the power grid fails, energy can be generated from methanol. The resulting carbon dioxide can be stored without significant energy expenditure. Once the power grid is stable again, the powder can be regenerated. During regeneration, the carbon dioxide is liquefied and stored. LIST OF FIGURES Fig. Figure 1 schematically shows the apparatus according to the invention for carbon dioxide storage and its flow diagram. Fig. Figure 2 shows a schematic flow diagram of the apparatus according to the invention. PREFERRED EXAMPLE OF EXECUTION

[0034] The Fig. Figure 2 schematically shows the flow diagram of the apparatus 13 according to the invention and thus the method according to the invention that can be carried out with the apparatus 13.

[0035] The core of apparatus 13 is the fluidized bed reactor 1, which is located in Fig. Figure 2 shows all inlet and outlet components in more detail. Fresh sodium carbonate in powder form can be fed from a sodium carbonate storage tank 5 into the fluidized bed reactor 1 through the fluidized bed inlet 8.

[0036] The exhaust gas from at least one methanol fuel cell 3 flows through water in a water saturation unit 2. This saturates the exhaust gas stream with water, and the now saturated exhaust gas stream flows through the exhaust gas inlet 14 into the eddy current reactor 1. Fig. Figure 1 also shows how a methanol fuel cell 3 is supplied with methanol from a methanol tank 7. The exhaust gas or exhaust gas stream can preferably be connected directly to the apparatus 13.

[0037] The water-saturated, carbon dioxide-containing exhaust gas stream preferably flows through a distributor plate 10 into the fluidized bed reactor 1. In this process, the exhaust gas stream becomes charged with sodium carbonate, which is preferably introduced into the fluidized bed reactor 1 via the sodium carbonate storage tank 5 and the subsequent fluidized bed inlet 8, or at least can be replenished via this sodium carbonate storage tank 5.

[0038] A cooling unit 11 preferably cools the exhaust gas stream in the fluidized bed reactor 1, causing the water in the exhaust gas stream to condense. This allows the sodium carbonate to react with the liquid water and carbon dioxide to form sodium bicarbonate. The cooling unit 11 also preferably removes the resulting reaction energy. The amount of water condensed from the exhaust gas stream can be controlled by appropriate temperature control of the cooling unit 11. This also allows the amount of carbon dioxide removed to be adjusted.

[0039] After the reaction, the resulting sodium bicarbonate, which is preferably in powder form, is extracted from the fluidized bed reactor 1 via the fluidized bed outlet 9 and preferably stored in a sodium bicarbonate storage tank 6. New sodium bicarbonate powder can be replenished from the sodium bicarbonate storage tank 5. This is preferably done automatically via a control system.

[0040] Preferably by means of a centrifugal separator 12, the post-reactionary exhaust gas stream from the fluidized bed reactor 1 is separated from any powder that may be carried along. The carbon dioxide-free exhaust gas then flows through the fresh air outlet 4 and can be released into the environment.

[0041] In order to transport the apparatus 13 on board a vehicle, it is preferred that the sodium carbonate storage 5, the sodium bicarbonate storage 6, and the fluidized bed reactor 1 are each mounted in or on the vehicle in the form of at least one tank, preferably vibration-resistant. The sodium bicarbonate storage 6 can then preferably be emptied after the journey and refilled with new material. REFERENCE MARK LIST 1 fluidized bed reactor 2 Water saturation units 3 Methanol fuel cell 4 Fresh air outlets 5 Sodium carbonate storage 6 Sodium bicarbonate storage 7 Methanol tank 8 Fluidized bed inlet 9 Fluidized bed outlet 10 distribution board 11 Cooling unit 12 centrifugal separators 13 Apparatus 14 Exhaust gas inlet

Claims

[1] Apparatus (13) for capturing and storing carbon dioxide from the exhaust gases of at least one methanol fuel cell (3), comprising: • a fluidized bed reactor (1) filled with sodium carbonate powder, • at least one exhaust gas inlet (14) for feeding carbon dioxide-containing exhaust gas into the fluidized bed reactor (1), • at least one unit (2) for water enrichment of the exhaust gas stream from the at least one methanol fuel cell in order to saturate the exhaust gas with water, • at least one cooling unit (11), preferably in the fluidized bed region, which cools the water-enriched exhaust gas stream so that the water in the exhaust gas condenses and reacts with the carbon dioxide and sodium carbonate, • at least one sodium carbonate storage tank (5) for storing the fresh sodium carbonate powder, • at least one sodium bicarbonate storage tank (6) for storing saturated powder after the reaction has taken place in the fluidized bed and • at least one outlet, preferably in the form of a fresh air outlet (4) for the discharge of the post-reactionary exhaust gas from the fluidized bed reactor (1). [2] Apparatus (13) according to claim 1, characterized by , that the sodium carbonate storage (5) is a powder tank with a downstream fluidized bed inlet (8), preferably in the form of a controllable and / or adjustable inlet valve to the fluidized bed reactor (1). [3] Apparatus (13) according to any one of the preceding claims, characterized by , that the sodium bicarbonate storage (6) is a powder tank with an upstream fluidized bed outlet (9), preferably in the form of a controllable and / or adjustable drain valve from the fluidized bed reactor (1). [4] Apparatus (13) according to any one of the preceding claims, characterized bythat the cooling unit (11) is at least partially located in the fluidized bed reactor (1) or at least partially located around parts of the fluidized bed reactor (1) and has a temperature control or temperature regulation. [5] Apparatus (13) according to any one of the preceding claims, characterized by , that the fluidized bed reactor (1) has at least one distribution plate (10) on which powdered sodium carbonate is located at least temporarily and through which the exhaust gas stream, preferably saturated with water, flows from the at least one methanol fuel cell. [6] Apparatus (13) according to any one of the preceding claims, characterized by , that the apparatus (13) has a centrifugal separator (12) upstream of the fresh air outlet (4), which is designed in such a way that any powder carried along is separated from the fluidized bed reactor (1). [7] Method for capturing and storing carbon dioxide from the exhaust gases of at least one methanol fuel cell (3), preferably by means of a device according to claim 1, comprising the steps: • Transfer of the carbon dioxide-containing exhaust gas stream from at least one methanol fuel cell into a fluidized bed reactor (1), • Enrichment of the exhaust gas stream with water until the exhaust gas stream is saturated, • Feeding the water-saturated exhaust gas stream into a fluidized bed (1) which is filled with sodium carbonate powder, • Cooling of the saturated exhaust gas stream so that the water in the exhaust gas stream condenses and reacts with the carbon dioxide and sodium carbonate to form sodium bicarbonate and • Storage of carbon dioxide in bound form using sodium bicarbonate, preferably in a sodium bicarbonate storage (6). [8] Method according to claim 7, characterized bythat the process can also be used to remove pollutants other than carbon dioxide from the exhaust gas stream, in particular for cleaning combustion gases. [9] Method according to any one of the preceding claims, characterized by that the process is suitable for stationary use in an emergency power system where methanol is used as an energy carrier, whereby the resulting carbon dioxide can be stored in the event of a power failure and regenerated later. [10] Vehicle, in particular a truck with a gross vehicle weight exceeding 7.5 t, comprising at least one apparatus (13) according to at least one of claims 1 to 6 directed to the apparatus, characterized by that the apparatus (13) is attached to or in the vehicle and has at least one exhaust inlet (14) through which the exhaust flow derived from the vehicle drive flows or is directed into the apparatus (13).

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