Thermochemical energy storage reactor

Abstract

The invention relates to a thermochemical energy storage reactor for carrying out a solid- gas reaction or a corresponding reverse reaction. The thermochemical energy storage reactor comprises a reaction volume (11), in which a solid energy storage material (30) and a gaseous reaction medium (32) form a mixture and react with each other, a particle inlet (15) for introducing the energy storage material (30), a particle outlet (16) for discharging the energy storage material (30), a gas inlet (17) for introducing the reaction medium (32), a gas outlet (18) for discharging the reaction medium (32), and a casing (19), which at least partly surrounds the reaction volume (11) and is adapted so as to carry out a heat transfer between a heat transfer fluid which flows in the casing (19) and the mixture, located in the reaction volume (11), of the energy storage material (30) and the reaction medium (32). The reaction volume (11) is mixed by at least one stirring element (20). The stirring element (20) is adapted so as to mix the energy storage material (30) and the reaction medium (32) by carrying out a stirring process about a stirring axis (22) which is substantially parallel to the direction of gravity (90).

Description

[0001] Thermochemical energy storage reactor

[0002] Technical field

[0003] The present invention relates to a thermochemical energy storage reactor.

[0004] State of the art

[0005] Various thermochemical storage approaches exist for storing and releasing energy at a later time, demonstrating high economic potential for the safe and long-term storage of energy. For example, a thermochemical energy storage reactor can be used to store and / or release thermal energy by conducting a gas-solid reaction between an energy storage material and a reaction medium. This reaction stores energy in the energy storage material, which can then be released through a corresponding reverse reaction.

[0006] Description of the invention

[0007] The object of the invention is to provide a thermochemical energy storage reactor which, with a simple design, is capable of efficiently carrying out a gas-solid reaction or a corresponding reverse reaction.

[0008] The aforementioned problem is solved by a thermochemical energy storage reactor with the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

[0009] One aspect of the invention relates to a thermochemical energy storage reactor for carrying out a gas-solid reaction or a corresponding reverse reaction. The thermochemical energy storage reactor can be provided as part of a thermochemical energy storage device. The thermochemical energy storage device can be configured to store thermal or electrical energy for a long period of time by means of a reaction, for example a gas-solid reaction, and to release it again, for example as heat, by means of a corresponding reverse reaction, for example a gas-solid reverse reaction.

[0010] The thermochemical energy storage reactor has a reaction volume in which a solid energy storage material and a gaseous reaction medium form a mixture and react with each other. The reaction volume can be located within the thermochemical energy storage reactor. The reaction volume can be at least partially cylindrical or cuboidal. The reaction volume can be designed to contain the energy storage material and the reaction medium so that they can form a mixture. The reaction volume can also be designed to allow the mixture of energy storage material and reaction medium to react under reaction conditions. The reaction conditions are the conditions, in particular pressures and temperatures, that prevail in the reaction volume while a reaction or a reverse reaction takes place.The reaction conditions can be, for example, a pressure of 50 bar and a temperature of 800 °C for the reaction, and a pressure of 0.001 bar and a temperature of -50 °C for the reverse reaction. Under these reaction conditions, the mixture can exist as a two-phase mixture. For example, the mixture can contain solid particles of the energy storage material and gaseous components of the reaction medium. Alternatively, the mixture can exist as a three-phase mixture. For example, the mixture can contain solid particles of the energy storage material and gaseous and liquid components of the reaction medium.

[0011] The thermochemical energy storage reactor can be configured to carry out both the reaction and the reverse reaction. It can be configured to perform the reaction and the reverse reaction as an equilibrium reaction. Alternatively or additionally, it can be configured to perform only the reaction or only the reverse reaction. The reaction and the reverse reaction can proceed separately, for example, with a time delay, or they can proceed simultaneously as an equilibrium reaction. In an equilibrium reaction, a reaction equilibrium is established depending on the boundary conditions. This equilibrium corresponds to a state in which the reaction rate of the primary reaction and the reaction rate of the reverse reaction are in a constant ratio. The position of the reaction equilibrium depends, for example, on pressure and temperature.Furthermore, the position of the reaction equilibrium depends on the specific reaction pair of energy storage material and reaction medium used. More precisely, for a given reaction pair at a certain pressure and temperature, the equilibrium lies on one side or the other: for the initial reaction, it lies on the product side, so that almost only products are present; for the reverse reaction, it lies on the reactant side, so that almost only reactants are present. Therefore, depending on the pressure and temperature, the reaction or reverse reaction for a given reaction pair may or may not occur predominantly. Consequently, the reaction outcome for a given reaction pair can be represented as a function of temperature and pressure.

[0012] The reaction and / or the reverse reaction can, as a reaction pair, use at least one reaction medium that exists at least partially as a gas under reaction conditions, and an energy storage material that exists at least partially as a solid under reaction conditions. The reaction and the reverse reaction can use the same reaction medium and the same energy storage material. The reaction and / or the reverse reaction can also use multiple reaction media and / or multiple energy storage materials. The reaction medium can exist as a two-phase mixture of gas and liquid under reaction conditions, with the gaseous reaction medium primarily participating in the reaction or reverse reaction. The reaction medium can be a single substance or a composition of multiple substances. The multiple substances can include reacting components and components that are inert with respect to the reaction.Under reaction conditions, the energy storage material can exist as a solid or as a two-phase mixture with a solid component, with the solid-state energy storage material primarily participating in the reaction and reverse reaction. The energy storage material can be a single substance or a composition of several substances. It can contain substances that can absorb and release reaction enthalpy (Ah) through a reversible equilibrium reaction with the reaction medium. This reversible equilibrium reaction can involve hydrogenation with water. For example, the energy storage material can contain metal oxides. As an example, the energy storage material can contain calcium oxide (CaO) or calcium dihydroxide (Ca(OH)₂), and the reaction medium can contain water (H₂O).

[0013] The reaction can be endothermic, in which energy is absorbed in the form of heat and added to the reacting pair as reaction enthalpy. This means that at least some of the energy supplied to the thermochemical energy storage reactor is stored in the energy storage material. Therefore, the reaction can serve as a charging step for the energy storage material, after which a charged energy storage material is present. An example of an endothermic reaction is Ca(OH)₂ + Ah → CaO + H₂O. In this example reaction, calcium dihydroxide (Ca(OH)₂) reacts to form calcium oxide (CaO) and water (H₂O), releasing energy that is to be stored. The energy released in this example reaction corresponds at least to the required reaction enthalpy (Ah).It should be noted that some of the input energy may not be stored as reaction enthalpy, but may remain as heat within the thermochemical energy storage reactor and influence temperatures or phase states. The calcium oxide (CaO) can be stored as a charged energy storage material, for example in a storage container.

[0014] The reverse reaction can be exothermic, meaning that reaction enthalpy is released from the reacting pair in the form of heat. At least some of this released reaction enthalpy can be extracted as usable heat from the thermochemical energy storage reactor. This allows the reverse reaction to serve as a discharge step for the energy storage material, resulting in a discharged energy storage material. An example of an exothermic reaction is CaO + HzO → Ca(OH)₂ + Ahβ, where the calcium dihydroxide Ca(OH)₂ can be stored as discharged energy storage material. It should be noted that some of the released reaction enthalpy, or heat, may not be extractable but may remain within the thermochemical energy storage reactor, potentially influencing temperatures or phase states.

[0015] Using the aforementioned examples of energy storage material, reaction medium, and reaction / reverse reaction, a gas-solid equilibrium reaction of Ca(OH)2+ Ah results. R CaO + H₂O, where the reverse reaction is the reverse of the first reaction. The described relationships also apply to other gas-solid reactions, especially gas-solid equilibrium reactions, and the present aspect is applicable to them. Examples of other suitable energy storage materials for gas-solid equilibrium reactions besides calcium oxide (CaO) are magnesium oxide (MgO), calcium dibromide (CaBr₂), and other metal oxides that react with water to form metal hydroxides.

[0016] The gas-solid equilibrium reactions of calcium oxalate (CaC2O4-nH2O) and strontium bromide (SrBr2 / H2O) are particularly suitable.

[0017] The thermochemical energy storage reactor has a particle inlet for introducing the energy storage material, a particle outlet for removing the energy storage material, a gas inlet for introducing the reaction medium, and a gas outlet for removing the reaction medium. Quantities of the energy storage material and the reaction medium can be introduced and removed both during operation and before / after any reaction or reverse reaction. One or more of the particle inlet, gas inlet, and gas outlet can be located on an upper side of the reaction volume; in the case of a cylindrical reaction volume, alternatively or additionally on a radial side; and in the case of a cuboid reaction volume, alternatively or additionally on a lateral side. The thermochemical energy storage reactor can have a lid located at the upper end of the reaction volume.The lid can accommodate one or more particle inlets, gas inlets, and gas outlets. For example, the lid can be equipped with nozzles for the respective inlets and outlets. The particle outlet can be located at or near a lower end of the reaction volume.

[0018] The energy storage material can be introduced into the reaction volume in particle form via the particle inlet. It can also be introduced as granular matter, such as grainy or powdery material. For example, it could be introduced as a metal oxide granulate. The energy storage material can form a clump within the reaction volume. Alternatively or additionally, it can be introduced in liquid, gaseous, or two-phase form and at least partially solidify within the reaction volume. The reaction medium can be introduced in liquid, gaseous, or two-phase mixtures of gas and liquid. For example, if water is the reaction medium, it could be introduced as water vapor or a mixture of boiling water and water vapor.If the reaction medium is introduced as a two-phase mixture due to only partial evaporation, the remainder of the liquid phase can be evaporated before or during the reaction, for example with the heat of reaction or with heat supplied from the outside.

[0019] The thermochemical energy storage reactor has a jacket that at least partially surrounds the reaction volume and is designed to facilitate heat transfer between a heat transfer fluid flowing in the jacket and the mixture of energy storage material and reaction medium within the reaction volume. The jacket can be configured as a double-walled structure between an outer wall of the reaction volume and an outer wall of the thermochemical energy storage reactor. For example, the thermochemical energy storage reactor can, from the inside out, comprise the following: the reaction volume, a reactor wall corresponding to an inner jacket wall or a boundary wall of the reaction volume, a jacket volume, an outer jacket wall, and an outer wall of the thermochemical energy storage reactor. Alternatively or additionally, the jacket can be partially or completely integrated into the outer wall of the thermochemical energy storage reactor.For example, an inner side of the outer wall of the thermochemical energy storage reactor can confine the reaction volume and form the reactor wall, and the jacket can be designed as piping within the outer wall of the thermochemical energy storage reactor. The jacket can be permeated by the heat transfer fluid. The jacket can be connected to other components of the thermochemical energy storage device that includes the thermochemical energy storage reactor to allow the heat transfer fluid to flow to / from them. These other components can be adapted to control the temperature of the heat transfer fluid. For example, these other components can include a cooling system and / or a heating system.

[0020] The jacket can facilitate heat transfer between the mixture in the reaction volume and the heat transfer fluid. For example, the jacket can provide a thin-walled separation structure between the reaction volume and the heat transfer fluid. The jacket can incorporate structures to modify the flow of the heat transfer fluid through it, further promoting heat transfer. Examples of such structures include baffles or modifications to the jacket's inner surface. The heat transfer fluid can be a fluid with a high heat capacity. For example, the heat transfer fluid can be water, molten salt, air, flue gases, or heat transfer oil. Utilizing the jacket and the heat transfer fluid to increase the temperature in the reaction volume can serve to introduce heat into the reaction volume for temperature changes, phase transitions, or as reaction enthalpy.The use of the jacket and the heat transfer fluid to lower the temperature in the reaction volume can serve to remove heat from the reaction volume. In particular, the jacket can be designed to remove heat from the reaction volume during the reverse reaction and make it available as usable heat. Thus, the jacket can be designed for both the input and output of energy.

[0021] The reaction volume is mixed by at least one agitator. The agitator is designed to mix the energy storage material and the reaction medium by stirring around a stirring axis. The stirring axis is arranged essentially parallel to a direction of gravity. The agitator can be configured to saturate the solid, for example, powdered, energy storage material with the gaseous reaction medium. The degree of saturation of the energy storage material with the reaction medium is crucial for the reaction rate and thus for the efficiency of the thermochemical energy storage reactor.

[0022] The agitator can be rotatable about the agitation axis. The agitation axis can be parallel to the direction of gravity. Alternatively or additionally, the agitation axis can have a slight angular offset, for example between -45° and +45°, preferably between -10° and 10°, even more preferably between -1° and 1°, to the direction of gravity. Alternatively or additionally, when the agitator is at rest, the agitation axis can be oriented perpendicular to a phase interface that forms between the gaseous reaction medium and the gas-solid mixture. The agitator can be configured to cause movement of the particles in axial, radial, and tangential directions, as will be described later. The agitator can be configured to cause upward movement of particles, while gravity causes downward movement of particles. The agitator can, for example, have one or more spirals or...The agitator features helical elements distributed around a central shaft running along the agitation axis, with the axis at its center. One or more supports can be attached to the central shaft at regular intervals, coupling the respective spiral(s) to the shaft. For example, one support can be provided for all spirals or one support for each spiral. The agitator can be driven by a drive mechanism. This drive mechanism can be located outside the reaction volume and transmit a force to the agitator as a rotational motion. Alternatively or additionally, the drive mechanism can be located at least partially within the reaction volume. The drive mechanism can be, for example, an electric motor.The force transmission can occur at an upper end or a lower end of the spiral(s), for example, by arranging the supports at the corresponding end of the spiral(s). The force transmission can also occur in sections of the spiral(s) located between the upper and lower ends. The rotational speed of the agitator can be variable. For example, the agitator can mix the reaction volume at a speed of 0.1 to 2000 rpm, preferably 5 to 100 rpm. The direction of rotation of the agitator can be variable. For example, the agitator can be used for particle mixing in one direction and for emptying the reactor in the other.

[0023] The agitator can have a circulating effect on the energy storage material in the reaction volume, thereby improving the mixing of the solid energy storage material and the gaseous reaction medium. Furthermore, the orientation of the agitator axis parallel to the direction of gravity assists particle movement during stirring. The reaction rate increases because the probability of particle collisions is increased and the contact times between the solid energy storage material and the gaseous reaction medium are extended. This reduces the duration of the reaction and reverse reaction for the same result, thus increasing the efficiency of the thermochemical energy storage reactor. In particular, the efficiency of the thermochemical energy storage reactor is higher the faster the reaction is for storing and releasing a specific amount of energy with the same result.The efficiency of the thermochemical energy storage reactor is understood as the ratio of the amount of energy that can be stored and released to the total amount of energy input into the thermochemical energy storage reactor.

[0024] The agitator of this thermochemical energy storage reactor improves heat transfer between the reactor wall and the mixture in the reaction volume, as well as within the mixture itself. This enhances both heat transfer into and out of the reaction volume, and heat and mass transfer within the reaction volume. Therefore, this thermochemical energy storage reactor exhibits particularly high efficiency.

[0025] In another embodiment, the reaction volume is at least partially defined by a reactor wall, which has a cylindrical section and a transition section located below it. The thermochemical energy storage reactor has the particle outlet close to a lower side of the transition section. The diameter of the transition section, extending from the cylindrical section towards the particle outlet, transitions from the diameter of the cylindrical section to the diameter of the particle outlet. The reactor wall can form a boundary wall of the reaction volume. The cylindrical section of the reactor wall can extend vertically along the direction of gravity and have an upper and a lower side. The cylindrical section can also be partially conical. An upper boundary surface of the reaction volume can be formed on the upper side of the cylindrical section.For example, the upper boundary surface can be designed as a disc-shaped or dome-like lid. The transition section can be formed on the lower side of the cylindrical section. The transition section can have a diameter that decreases downwards. The transition section can, for example, have a conical shape. The particle outlet can be located on or near the lower side of the transition section. The reactor wall, which defines the reaction volume, can be designed such that the energy storage material can be passively removed from the reaction volume by gravity.

[0026] In a further embodiment, the thermochemical energy storage reactor also features internal flow-optimizing components. These flow-optimizing components can, for example, be designed as internals within the reaction volume. They can be designed to increase the heat input into the gas-solid mixture and / or to delineate individual flow and reaction zones for more efficient conversion rates. The flow-optimizing components can be mounted in an upper or lower section of the reactor wall. They can be essentially vertical. The flow-optimizing components can be positioned such that the agitator moves around them. The shaft of the agitator can be positioned above or below the internals.Flow-optimizing components can be designed to redirect particle motion for increased heat transfer, for example, through longer and more intensive contact time at the heated or cooled surfaces. These components can, for instance, have a shape that increases residence time, distributes the flow profile more uniformly, and / or intensifies the flow over the surfaces participating in heat transfer. In particular, the flow-optimizing components can be positioned in a boundary layer region between an upward-flowing portion of the mixture and a downward-flowing portion. As a result, the boundary layer region can be avoided, and the upward and downward flowing portions can be separated, thus preventing backmixing between the two flow zones and irregular flow.Alternatively or additionally, horizontal flow-optimizing components can be designed essentially in a horizontal plane. For example, such horizontal flow-optimizing components can divide the reaction volume into different zones along the stirring axis. The flow-optimizing components can be designed, for example, as sheets, vertical tubes, and / or a double tube concentric with the stirring axis. The vertical tubes can be arranged in a circle on a support, such as a ring.

[0027] In another embodiment, the agitator is adapted to effect a mixing motion of the mixture of energy storage material and reaction medium in the circumferential direction of the agitator. Alternatively or additionally, the agitator is adapted to effect a mixing motion of the mixture of energy storage material and reaction medium in the radial direction of the agitator. Alternatively or additionally, the agitator is adapted to effect a mixing motion of the mixture of energy storage material and reaction medium in the axial direction of the agitator. The agitator can move the particles of the mixture in the axial, radial, and / or tangential direction. Several or all of these directions of movement can be combined to achieve a specific particle movement of the mixture within the reaction volume.In axial circulation, the particles can be transported from near the bottom of the reaction volume outwards and then along the reactor wall against gravity upwards towards the surface of the mixture, in order to achieve the longest possible contact time between the reactor wall and the mixture.

[0028] The goal is to create a mixture and thus maximize heat transfer. The particles then move downwards along the agitator axis due to gravity. Axial circulation can also include radial components. In radial circulation, the particles are transported from the center of the agitator radially outwards along the agitator towards the reactor wall and back towards the reactor center, potentially including an axial component. This promotes mass transfer between the solid and gaseous media as well as heat transfer to the reactor center. Radial circulation can also include tangential components. Furthermore, tangential circulation can occur around the circumference of the agitator. These and other types of circulation can combine to create particle movement.The circulation improves the mixing of the solid energy storage material and the gaseous reaction medium, as well as the heat transfer between the particles and the reactor wall. If a heat source is provided within the reaction volume, as described later, the heat transfer between this source and the particles is also improved.

[0029] In another embodiment, the agitator has several sections with different geometric properties along the agitation axis and is designed to achieve varying degrees of mixing in each section. For example, an upper section can be an agitator segment with a cylindrical casing geometry, and a lower section a segment with a conical casing geometry. This is particularly advantageous in combination with the aforementioned reactor wall, which has a cylindrical section and a transition section. Alternatively or additionally, several sections with different diameters can be provided. If the agitator has spirals or helical elements, each section can have a different spiral pitch. Furthermore, the diameter and / or the spiral pitch can be continuously variable along the agitation axis.The present embodiment allows sections of the agitator to be adapted to geometrically different areas of the reaction volume. Furthermore, different mixing zones can be created, which can, for example, be adapted to a temperature distribution.

[0030] In another embodiment, the thermochemical energy storage reactor has multiple agitators. These agitators can be arranged concentrically around a common agitation axis within the reaction volume. For example, a radially outer agitator can cause upward particle movement, and a radially inner agitator can cause downward particle movement. Alternatively or additionally, multiple axes, each with one or more agitators, can be provided within the reaction volume.

[0031] In another embodiment, the jacket is designed as a heat exchanger for the energy storage reactor. The jacket can, with the aid of the heat transfer fluid, increase the temperature and / or introduce heat of reaction into the thermochemical energy storage reactor. Alternatively or additionally, the jacket can, with the aid of the heat transfer fluid, decrease the temperature and / or remove heat of reaction from the thermochemical energy storage reactor. The heat input through the jacket improves heat transfer in the gas-solid mixture and promotes the reaction, thus achieving higher efficiency. The heat released during the reverse reaction can be easily removed from the reaction volume and the thermochemical energy storage reactor by the jacket and extracted as usable heat.

[0032] In another embodiment, the thermochemical energy storage reactor includes heating elements for increasing the temperature in the reaction volume and / or for introducing reaction energy. The heating elements can be designed separately from the aforementioned jacket. The heating elements can further enhance heat input through the jacket and / or counteract heat losses to the environment. The heating elements can be rods, plates, spirals, and / or other geometries suitable for heat conduction, designed to increase the temperature in the reaction volume, for example, to vaporize the reaction medium, and / or to introduce reaction energy, for example, to initiate the reaction. The heating elements can, for example, be housed in a double tube positioned concentrically to the stirring axis.Alternatively or additionally, the heating elements can be designed as individual heating rods, optionally surrounded by a tube, arranged in a circle on a ring. A single heating element can also be used. The additional heat input and surface area improve heat transfer in the gas-solid mixture, resulting in higher efficiency.

[0033] In another embodiment, the thermochemical energy storage reactor has a reactor wall resistance heater on or in the reactor wall to increase the temperature in the reaction volume and / or to introduce reaction energy. The reactor wall resistance heater can have at least one heating element, for example, a heating resistor. Alternatively or additionally, the heating element can be a wire. Furthermore, the heating element can be in the form of a rod or a tube. The reactor wall resistance heater can have several heating elements. The reactor wall resistance heater, or a part thereof, for example, the heating element, can be located inside and / or outside the reactor wall. Alternatively or additionally, the reactor wall resistance heater, or a part thereof, for example, the heating element, can be integrated into the reactor wall.The reactor wall resistance heating can be provided on the entire surface of the reactor wall or on parts thereof.

[0034] In a further embodiment, the thermochemical energy storage reactor features a reaction volume resistance heater located within the reaction volume. The reaction volume resistance heater can comprise at least one heating element, for example, a heating resistor. Furthermore, the heating element can be designed as a wire. Additionally, the heating element can be in the form of a rod or a tube. The reaction volume resistance heater can have multiple heating elements. The reaction volume resistance heater, or a part thereof, for example, the heating element, can be located within the flow-optimizing components, if present. Alternatively or additionally, the reaction volume resistance heater, or a part thereof, for example, the heating element, can be arranged freestanding or suspended within the reaction volume and in direct contact with the mixture.

[0035] In a further embodiment, the thermochemical energy storage reactor has flowable geometries arranged to introduce or remove heat into or out of the reaction volume via a heating or cooling system for temperature changes, phase transitions, or as heat of reaction. The heating and / or cooling system can be separate from or integrated with the thermochemical energy storage reactor. For example, the heating and / or cooling system can be components of the thermochemical energy storage device. The heating and / or cooling system can provide an additional heat transfer fluid that flows through the flowable geometries and performs heat transfer with the mixture in the reaction volume. The heating and / or cooling system can be configured to regulate the temperature of the additional heat transfer fluid.

[0036] In a further embodiment, the heating elements and the reaction volume resistance heater, if present, are arranged in the reaction volume such that the particle movement of the mixture by the agitator in the reaction volume is at least not impaired. If flow-optimizing components are provided, the heating elements and the reaction volume resistance heater can be arranged within them to avoid impeding the particle movement of the mixture. Alternatively or additionally, the heating elements and the reaction volume resistance heater can be arranged in flow zones where a dead volume with flow components close to zero is created during stirring by the agitator.

[0037] In another embodiment, cooling elements are provided as an alternative or in addition to the aforementioned heating elements. These elements are arranged analogously and can serve as heat sinks, for example, to remove heat from the reaction volume.

[0038] In another embodiment, inner surfaces of the reaction volume are coated with a non-stick coating. This can increase the service life of the thermochemical energy storage reactor. It can also promote particle movement.

[0039] In a second aspect of the invention, a method is provided for operating the thermochemical energy storage reactor of the first aspect. In a further aspect of the invention, a thermochemical energy storage device is provided, comprising the thermochemical energy storage reactor of the first aspect. The thermochemical energy storage device may include a heating system for introducing heat into the reaction medium and / or for introducing heat of reaction into the thermochemical energy storage reactor. The thermochemical energy storage device may include a cooling system for removing heat from the reaction medium and / or for removing heat of reaction from the thermochemical energy storage reactor.The thermochemical energy storage device can include a storage container for storing the energy storage material and a material flow device for conveying energy storage material from the storage container to the thermochemical energy storage reactor and from the thermochemical energy storage reactor to the storage container.

[0040] Brief description of the characters

[0041] Fig. 1 schematically shows a thermochemical energy storage reactor according to one embodiment.

[0042] Fig. 2a schematically shows the reaction volume of a thermochemical energy storage reactor without internal components.

[0043] Fig. 2b is an enlarged view of a section of Fig. 2a and schematically shows flow conditions in the reaction volume.

[0044] Fig. 2c schematically shows the reaction volume of a thermochemical energy storage reactor with internals.

[0045] Fig. 2d is an enlarged view of a section of Fig. 2c and schematically shows flow conditions in the reaction volume.

[0046] Fig. 3a schematically shows flow conditions in the reaction volume. Fig. 3b schematically shows axial circulation in the reaction volume.

[0047] Fig. 3c schematically shows a radial circulation in the reaction volume.

[0048] Fig. 3d schematically shows a tangential circulation in the reaction volume.

[0049] Fig. 4a schematically shows the reaction volume of another embodiment of the thermochemical energy storage reactor.

[0050] Fig. 4b schematically shows the reaction volume of another embodiment of the thermochemical energy storage reactor.

[0051] Fig. 4c schematically shows the reaction volume of another embodiment of the thermochemical energy storage reactor.

[0052] Fig. 4d schematically shows the reaction volume of another embodiment of the thermochemical energy storage reactor.

[0053] Fig. 5 schematically shows the reaction volume of another embodiment of the thermochemical energy storage reactor.

[0054] Detailed description of embodiments

[0055] Fig. 1 schematically shows a thermochemical energy storage reactor 10 according to one embodiment. The thermochemical energy storage reactor 10 is provided as part of a thermochemical energy storage device (not shown). The thermochemical energy storage reactor 10 is configured to store thermal energy by means of a gas-solid reaction and to release it again as heat by means of a corresponding gas-solid reverse reaction. The thermochemical energy storage device includes a heating system (not shown) with which incoming electrical energy is converted into heat to be supplied to the thermochemical energy storage reactor. The thermochemical energy storage device also includes a cooling system (not shown) with which heat is removed from the thermochemical energy storage reactor as usable heat.

[0056] The gas-solid reaction and gas-solid reverse reaction are described here as a gas-solid equilibrium reaction of calcium dihydroxide to calcium oxide and water vapor and back, i.e., Ca(OH)₂ + Ah R <-> CaO + H2O, provided. To store energy, calcium dihydroxide Ca(OH)2 is converted to calcium oxide CaO and water vapor H2O with the addition of heat, whereby the heat input is at least equal to the required reaction enthalpy Ah. R This corresponds to the following. Thus, calcium oxide CaO and calcium dihydroxide Ca(OH)₂ serve as an energy storage material 30, with the calcium oxide CaO serving as the charged energy storage material and the calcium dihydroxide Ca(OH)₂ as the discharged energy storage material. Water or water vapor H₂O serves as a reaction medium 32. The energy storage material 30 is present as a solid or granules in the operation of the thermochemical energy storage reactor 10, i.e., on both sides of the equilibrium reaction.

[0057] Meanwhile, primarily gaseous water vapor H2O reacts as reaction medium 32 with the energy storage material 30.

[0058] The thermochemical energy storage reactor 10 has a reaction volume 11. The reaction volume 11 is bounded laterally and downwards by a reactor wall 12, which has a cylindrical section 13 and a conical transition section 14 (Fig. 2a). The reaction volume 11 is bounded upwards by a lid (not shown). The reaction volume 11 contains energy storage material 30 and reaction medium 32, which form a mixture and react with each other.

[0059] The thermochemical energy storage reactor 10 further comprises a particle inlet 15, a particle outlet 16, a gas inlet 17, and a gas inlet 18 for introducing and expelling the energy storage material 30 and the reaction medium 32. The particle inlet 15, the gas inlet 17, and the gas inlet 18 are incorporated in the lid and are provided as separable nozzles, with only the nozzle at the particle inlet 15 being shown by way of example in Fig. 1. The particle outlet 16 is designed as a circular opening at a lower end of the reaction volume 11.

[0060] The thermochemical energy storage reactor 10 has a jacket 19 through which a heat transfer fluid flows. The jacket 19 surrounds the reaction volume 11, specifically the reactor wall 12. The jacket 19 is designed as a double-tube structure through which the heat transfer fluid flows. The jacket 19 is connected to the cooling and heating systems of the thermochemical energy storage device, with the heat transfer fluid passing through the cooling and / or heating system as needed to reach a desired temperature. The reacting mixture in the reaction volume 11 exchanges heat with the heat transfer fluid via the jacket 19. Thus, depending on the temperature difference, heat is either added to or removed from the mixture by the heat transfer fluid.

[0061] The thermochemical energy storage reactor 10 further comprises an agitator 20, which mixes the reaction volume 11 or the mixture within the reaction volume 11. The agitator 20 is shown symbolically in Fig. 1 and will be described in more detail later. The agitator 20 rotates about a stirring axis 22, which runs parallel to a direction of gravity 90. The agitator 20 is driven by an electric motor 26 via a central shaft 24. In this case, the electric motor 26 is arranged above the reaction volume 11.

[0062] The thermochemical energy storage reactor 10 further comprises a control unit 80. The control unit 80 includes measuring devices that detect the temperature and pressure in the reaction volume 11 and transmit this information to the control unit 80. The control unit 80 also includes a metering device 82 at the particle inlet 15, a metering device 84 at the particle outlet 16, and metering devices (not shown) at the gas inlet 17 and gas outlet 18 to detect and control mass flows into and out of the reaction volume 11. Furthermore, the control unit 80 is configured to adjust the temperature of the heat transfer fluid and to control heat flows into and out of the mixture. In addition, the control unit 80 is configured to control heating elements described later. Finally, the control unit 80 is configured to control a pressure control device (not shown) that is part of the thermochemical energy storage device.

[0063] Fig. 2a schematically shows the reaction volume 11 of a thermochemical energy storage reactor 10 without internal components. More precisely, Fig. 2a schematically shows the reactor wall 12, which defines the reaction volume 11. No internal components or flow-optimizing elements are provided in the reaction volume 11 of Fig. 2a. The reactor wall 12 has a cylindrical section 13 and a transition section 14, the transition section 14 being located below the cylindrical section 13 and seamlessly connected to it. The transition section 14 has a conical shape, the diameter of which decreases downwards from the cylindrical section 13. The particle outlet 16 is formed at the lower end of the transition section 14. The diameter of the transition section 14 transitions from the diameter of the cylindrical section 13 to the diameter of the particle outlet 16.

[0064] As can be seen in Fig. 2a, the agitator 20 of the present embodiment has the form of a double helix of type 1. Thus, the agitator 20 is designed as two spirals offset by 180° about the agitation axis 22 and each connected to the central shaft 24. The spirals have a constant diameter over their height. Furthermore, Fig. 2a shows an exemplary fill level 34 that forms during agitation. Above the fill level 34, the reaction volume 11 is essentially filled only with gaseous reaction medium 32. Below the fill level 34, the reaction volume is essentially filled with the mixture of energy storage material 30 and reaction medium 32. A phase interface between the mixture and the reaction medium 32 therefore exists at the fill level 34. It should be noted that the phase interface can typically be a curved surface, which is determined by the geometry of the material.Particularly during stirring by the agitator 20, the phase interface can change its shape. Fig. 2b is an enlarged view of a section of Fig. 2a and schematically shows flow conditions in the reaction volume 11 during stirring by the agitator 20. The figure shows an exemplary vertical velocity profile of the mixture against the radius. Furthermore, exemplary motion arrows of the mixture in a boundary layer region 36 are shown. As can be seen in the figure, parts of the mixture in the region of the agitator 20 and near the reactor wall 12 move vertically upwards due to the stirring. Conversely, parts of the mixture in the region radially inside the agitator 20 and near the central shaft 24 move vertically downwards due to gravity. The boundary layer region 36 is therefore formed between these two opposing flows.In boundary layer region 36, the velocity profile transitions from upward flow velocity to downward flow velocity and therefore exhibits a zero crossing. It should be noted that the position of the zero crossing changes with height, i.e., along the stirring axis 22, as well as with time, and is thus variable both temporally and spatially. Therefore, irregular and unstable flow conditions exist in boundary layer region 36, which may reduce the mixing and thus the efficiency of the energy storage reactor.

[0065] To improve mixing, flow-optimizing components can be provided, for example, as internals in the reaction volume 11. Fig. 2c schematically shows the reaction volume 11 of a thermochemical energy storage reactor with exemplary internals. Fig. 2d is an enlarged view of a section of Fig. 2c and schematically shows flow conditions in the reaction volume 11 with the internals. The reaction volume 11, the reactor wall 12, and the agitator 20 of Fig. 2c are designed analogously to Fig. 2a. Additionally, a double tube 50 is provided as a flow-optimizing component. The double tube 50 has an outer tube and an inner tube that are concentric with each other and with the agitator axis 22. The double tube 50 is arranged in the boundary layer region 36. For example, the double tube 50 overlaps an average zero crossing of the velocity profile.Since the flow velocities radially inside and outside the double tube 50 are naturally zero in the boundary layer with the double tube 50, the variable zero crossing of the velocity profile can thus be avoided. This results in a steady velocity profile with respect to zero crossings, as shown in Fig. 2d, instead of the irregular and unstable flow conditions of Fig. 2b. Furthermore, this creates two separate flow and reaction zones radially inside and radially outside the double tube 50.

[0066] Fig. 3a schematically shows flow conditions in the reaction volume 11. The arrows in the figure represent exemplary particle movements 40 in the reaction volume 11. The particle movements 40 consist of three primary flow mechanisms. The primary flow mechanisms in the reaction volume 11 are an axial circulation 42, shown in Fig. 3b, a radial circulation 44, shown in Fig. 3c, and a tangential circulation 46, shown in Fig. 3d. The aforementioned circulation modes are determined by the design of the agitator 20. The axial circulation 42 and the tangential circulation 46, in particular, promote the residence times of the particles near the jacket 19, which improves heat transfer. The radial circulation 44 particularly promotes the mixing and thus the reaction rate of the energy storage material 30 and the reaction medium 32 within the reaction volume 11.

[0067] Fig. 4a schematically shows another embodiment of the thermochemical energy storage reactor 10. In this embodiment, five heating rods 52, forming a reaction volume resistance heater, are provided in the reaction volume 11. The heating rods 52 are arranged radially within the agitator 20. The heating rods 52 therefore serve to provide additional heat input besides that of the jacket 19. The heating rods 52 are attached to the lower end of the reactor wall 12 by a mounting 54. The mounting 54 has an annular section that holds the heating rods 52 and several arms that extend from the annular section to the reactor wall 12. During operation, the heating rods 52 are arranged completely below the fill level 34 to prevent overheating. Fig. 4b schematically shows another embodiment of the thermochemical energy storage reactor. This embodiment corresponds to the embodiment of Fig.4a, in contrast to the heating rods 52, a double tube 50 with a heating coil 56 (not shown) housed within the double tube 50 is provided. The heating coil 56 forms the reaction volume resistance heater. Furthermore, the double tube 50 is permeated by an additional heat transfer fluid, which is connected to the heating and cooling systems. Thus, the double tube 50 provides a flowable geometry and is able to introduce and remove additional heat from the reaction volume 11. The double tube 50 and the heating coil 56 are attached to the lower end of the reactor wall 12 by a mounting 54. During operation, the heating coil 56 is positioned completely below the fill level 34 to prevent overheating.

[0068] Fig. 4c schematically shows another embodiment of the thermochemical energy storage reactor. This embodiment corresponds to the embodiment of Fig. 4a, except that the five heating rods 52 are attached to the upper end of the reactor wall 12 by a mounting 54. The mounting 54 of Fig. 4d is arranged above the fill level 34.

[0069] Fig. 4d schematically shows another embodiment of the thermochemical energy storage reactor. This embodiment corresponds to the embodiment of Fig. 4b, except that the double tube 50 and the heating coil 56 are attached to the upper end of the reactor wall 12 by a mounting 54. The mounting 54 of Fig. 4c is arranged above the filling level 34.

[0070] Fig. 5 schematically shows another embodiment of the thermochemical energy storage reactor. This embodiment differs from the embodiment of Fig. 2a in that a dividing plate 51 is provided horizontally in the reaction volume 11 as a flow-optimizing component. The dividing plate 51 has a flat shape and is connected to the reactor wall 12. The dividing plate 51 is designed such that particle movement from the zone below the dividing plate 51 to the zone above the dividing plate 51 is only possible to a limited extent. Thus, the dividing plate 51 forms two separate flow and reaction zones in the reaction volume 11. Furthermore, the agitator of this embodiment has two different geometries. An upper region 28 of the agitator above the dividing plate 51 has a first helical diameter and a first pitch.A lower section 29 of the agitator below the dividing plate 51 has a second helix diameter and a second pitch. The second helix diameter is smaller than the first helix diameter, and the second pitch is larger than the first pitch. The upper section 28 and the lower section 29 of the agitator are coupled by a common central shaft 24. Furthermore, a heating element 58 is provided on the reactor wall 12 below the dividing plate 51. The heating element 58 forms a reactor wall resistance heater for introducing additional heat into the mixture. In another embodiment, a heating element is provided above the dividing plate 51. In yet another embodiment, the heating element is provided on an outer surface of the reactor wall 12 inside the jacket and over the entire height of the cylindrical section 13.

[0071] While the embodiment of Fig. 5 with the combination of dividing plate 51, heating element 58, and two sections 28, 29 of the agitator has been described, one, several, or all of these features can be omitted. In a further embodiment, the agitator is divided into two sections without a dividing plate. In yet another embodiment, the heating element extends over the entire reactor wall 12; in yet another embodiment, the heating element extends over parts of the reactor wall 12; and in yet another embodiment, the heating element is omitted entirely. List of reference numerals

[0072] 10 thermochemical energy storage reactor

[0073] 11 reaction volume

[0074] 12 Reactor wall

[0075] 13 cylindrical section

[0076] 14 Transition section

[0077] 15 Particle intake

[0078] 16 Particle outlet

[0079] 17 Gas inlet

[0080] 18 Gas outlet

[0081] 19 coat

[0082] 20 Stirring element

[0083] 22 Stirring shaft

[0084] 24 medium wave

[0085] 26 electric motor

[0086] 28 upper area

[0087] 29 lower area

[0088] 30 Energy storage material

[0089] 32 Reaction medium

[0090] 34 Fill level, phase interface

[0091] 36 Boundary layer area

[0092] 40 particle movements

[0093] 42 axial circulation

[0094] 44 radial circulation

[0095] 46 tangential circulation

[0096] 50 Double pipe, flow-optimizing component, flowable geometries

[0097] 51 Dividing plate, flow-optimizing component

[0098] 52 Heating rod, reaction volume resistance heater

[0099] 54 Fastening

[0100] 56 Heating coil, reaction volume resistance heater

[0101] 58 Heating resistor, reactor wall resistance heater

[0102] 80 Control unit Metering device Particle inlet Metering device Particle outlet Gravity direction

Claims

Patent claims 1. Thermochemical energy storage reactor (10) for carrying out a gas-solid reaction or a corresponding reverse reaction, wherein the thermochemical energy storage reactor (10) comprises: a reaction volume (11) in which a solid energy storage material (30) and a gaseous reaction medium (32) form a mixture and react with each other, a particle inlet (15) for introducing the energy storage material (30), a particle outlet (16) for removing the energy storage material (30), a gas inlet (17) for introducing the reaction medium (32), a gas outlet (18) for removing the reaction medium (32), and a jacket (19) which at least partially surrounds the reaction volume (11) and is adapted to carry out heat transfer between a heat transfer fluid flowing in the jacket (19) and the mixture of energy storage material (30) and reaction medium (32) located in the reaction volume (11).wherein the reaction volume (11) is mixed by at least one stirring element (20), and wherein the stirring element (20) is adapted to mix the energy storage material (30) and the reaction medium (32) by stirring about a stirring axis (22) which is arranged substantially parallel to a gravity direction (90).

2. Thermochemical energy storage reactor (10) according to claim 1, characterized in that the reaction volume (11) is at least partially defined by a reactor wall (12) which has a cylindrical section (13) and a transition section (14) arranged below it, the thermochemical energy storage reactor (10) has the particle outlet (16) close to a lower side of the transition section (14), and a diameter of the transition section (14) from the cylindrical section (13) towards the particle outlet (16) transitions from the diameter of the cylindrical section (13) to the diameter of the particle outlet (16).

3. Thermochemical energy storage reactor (10) according to claim 1 or 2, characterized in that the thermochemical energy storage reactor (10) further comprises internal flow-optimizing components (50).

4. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the stirring element (20) is adapted to effect a mixing movement of the mixture of energy storage material (30) and reaction medium (32) in the circumferential direction of the stirring element.

5. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the stirring element (20) is adapted to effect a mixing movement of the mixture of energy storage material (30) and reaction medium (32) in the radial direction of the stirring element.

6. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the stirring element (20) is adapted to effect a mixing movement of the mixture of energy storage material (30) and reaction medium (32) in the axial direction of the stirring element.

7. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the stirring element (20) has several areas (28, 29) with different geometric properties along the stirring axis (22) and is adapted to achieve different mixing in the respective areas (28, 29) along the stirring axis (22).

8. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the thermochemical energy storage reactor (10) has several stirring elements.

9. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the jacket (19) is designed as a heat exchanger for the thermochemical energy storage reactor (10); wherein the jacket (19) can, by means of the heat transfer fluid, cause a temperature increase and / or the introduction of heat of reaction into the thermochemical energy storage reactor (10); and / or cause a temperature decrease and / or the removal of heat of reaction from the thermochemical energy storage reactor (10).

10. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the thermochemical energy storage reactor (10) has heating elements (52, 56) for increasing the temperature in the reaction volume (11) and / or for introducing reaction energy.

11. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the thermochemical energy storage reactor (10) has a reactor wall resistance heater (58) on or in the reactor wall (12) for increasing the temperature in the reaction volume (11) and / or for introducing reaction energy.

12. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the thermochemical energy storage reactor (10) further comprises a reaction volume resistance heater (52) for increasing the temperature in the reaction volume (11) and / or for introducing reaction energy, which is arranged in the reaction volume (11).

13. Thermochemical energy storage reactor (10) according to one of the preceding claims, characterized in that the thermochemical energy storage reactor (10) further comprises flowable geometries (50) which are arranged to introduce or remove heat into or out of the reaction volume (11) by means of a heating system or a cooling system for temperature change, phase transition or as heat of reaction.

14. Thermochemical energy storage reactor (10) according to one of claims 10 to 13, characterized in that, where present, the heating elements (52, 56) and the reaction volume resistance heating (52) are arranged in the reaction volume (11) such that the particle movement of the mixture by the stirring element (20) in the reaction volume (11) is at least not impaired.

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