Particle-particle vibration heat exchanger

Abstract

A device comprising at least one heat exchanger (5) with at least one first inlet (1) for a first material and at least one second inlet (2) for a second material, wherein the first material comprises a particulate heat transfer medium (6) and the second material comprises particles (7), wherein the heat transfer medium (6) and the particles (7) are brought into direct contact with each other in the heat exchanger (5) in a counterflow, whereby heat can be transferred from one particulate material to the other, and at least one device for generating vibrations, wherein the heat transfer medium (6) and the particles (7) have different solid densities, wherein the first inlet (1) is located further down on the heat exchanger (5) than the second inlet (2) in accordance with gravity, wherein in the heat exchanger (5) the particles (7) can rise from top to bottom and the heat transfer medium (6) can rise from bottom to top in accordance with gravity.and wherein the device further comprises various internal components inside the heat exchanger (5) such as ribs, screws, projections, protrusions or depressions which can direct the flow direction and influence the flow behavior of the particles (7) and / or the heat transfer medium (6).

Description

[0001] The present invention relates to a device for transferring heat from one particulate material to another and to a method for transferring heat using particulate materials.

[0002] Heat transfer is a crucial aspect of various industrial processes. For example, foodstuffs, and especially grains, are heated to remove moisture, thus enabling longer storage. High temperatures are also required in other industrial processes, such as cement production. This is typically achieved through the combustion of fossil fuels. The demand for these fuels can be reduced by recovering the sensible heat from the hot products and repurposing it. This is often accomplished by passing ambient air over or through the products from industrial processes. The heated air is then used, for example, as combustion air or to preheat materials to be processed.

[0003] Comparing the volumetric heat capacity of air with that of the material to be heated, such as grain or cement, it becomes clear that, simply because a gas is used compared to a solid, a significantly larger volume flow rate is required to achieve the same heat capacity flow rate for both media. Equal heat capacity flow rates for the media involved are optimal for the efficiency of heat transfer.

[0004] In cement production, a mixture of limestone, clay, sand, and iron ore is fired at approximately 1400 °C. Here, too, the sensible heat from the product, known as clinker, should be recovered to reduce the overall energy consumption of the process. The clinker is cooled by transferring the sensible heat to air. This air serves as a heat transfer fluid and, in particular, as combustion air, since cement production is currently powered by fossil fuels. The reactants are preheated by a mixture of the reaction product gas and the combustion gas. This process can be powered by concentrated solar radiation instead of fossil fuels. In this case, combustion air and combustion gas cannot be used as heat transfer fluids, and the heat must be transferred between two particle streams (the particle stream to be heated and the clinker to be cooled).

[0005] Gas particle heat exchangers are typically used in cement production. Grate or cyclone preheaters are particularly common. Since these heat exchangers operate on the cross-flow or quasi-counter-flow principle, only a limited heat transfer rate can be achieved.

[0006] Another technical area in which heat transfer and heat recovery are relevant is thermochemical cycles for the production of hydrogen using redox particles, as described, for example, by C. Agrafiotis et al. in A review on solar thermal syngas production via redox pair based water / carbon dioxide splitting thermochemical cycles (Renewable and Sustainable Energy Reviews, 42(0) (2015) 254-285).

[0007] These processes are based on the cyclic treatment of a metal oxide—the redox material—which assumes various valence states. At temperatures of approximately 1400 °C, the redox material is reduced, releasing oxygen. After this regeneration step, the material is cooled to approximately 1000 °C and then undergoes the water splitting step. Here, hydrogen is produced through the reduction of water. The cycle is closed by heating the now oxidized redox material to the reduction temperature, preferably using concentrated solar radiation, and then subjecting it to the regeneration step again. Analogous to the described water splitting, CO₂ can also be split into CO or water, and CO₂ into H₂ and CO, so-called synthesis gas. Cerium oxide is typically used as the redox material. The reduction of the redox material used is generally not complete.Only about 5% of the oxygen that can theoretically be released from the redox material is actually released during reduction at commonly achievable temperatures and oxygen partial pressures, for example, when using cerium oxide as the redox material. This leads to high cyclized mass flow rates and thus to high heat flows required to heat the redox material from the temperature level of the splitting step to that of the regeneration step. An efficient heat recovery system from the reduced redox material is therefore essential for a high overall efficiency. Numerous system concepts for solar thermochemical water splitting envision the use of particulate redox materials. This raises the challenge of heat recovery from the particle streams.

[0008] Therefore, with regard to heat recovery and the construction of reactors for solar thermochemical water or carbon dioxide splitting or chemical processes with particulate catalysts or reaction material, the question of heat transfer or heat flow in the reaction or within the reactor in which the reaction takes place is of interest.

[0009] Various methods for heat recovery can be found in the literature: DE 10 2011 108 713 A1 describes a solar thermal power plant with a reflector device and an absorber device, wherein the reflector device reflects sunlight onto the absorber device via reflector surfaces, with a heat transfer fluid that is conductive through the absorber device to absorb thermal energy from sunlight, and with a thermal energy consumer that can be supplied with thermal energy via the heat transfer fluid. It is provided that the heat transfer fluid is a free-flowing bulk material, whereby the thermal energy is transported to the consumer and / or stored via the heat transfer fluid.

[0010] DE 43 36 503 A1 proposes, in order to create a device for carrying out endothermic chemical reactions involving particles, comprising a reaction vessel in which the particles can be heated by electromagnetic radiation, such that an optimized adaptation of the absorbed radiation power to a substantially complete gasification of the carbon-containing material is possible, that the reaction vessel has a heating zone in which absorber particles or absorber particles and the particles can be heated by direct absorption of the radiation, and that the reaction vessel has a residence zone in which the absorber particles transfer heat to the particles in order to maintain the chemical reaction.

[0011] DE 10 2008 036 210 A1 discloses a radiation receiver for transferring the energy of incident solar radiation to solid particles, which has an inclined plane (SE) on which the solid particles slide down in a controlled manner from an inlet device to an outlet. The radiation from a heliostat field is reflected by a secondary mirror onto the inclined plane (SE). The particles sliding down the inclined plane are heated by the solar radiation and discharged into a tank. The particles form a heat storage medium from which heat can be extracted as needed.

[0012] DE 10 2010 053 902 A1 describes a solar radiation receiver comprising an absorber through which a heat transfer medium flows along one flow path and a reactant flows along another flow path. The reactant is to be chemically converted into a product using thermal energy. In daytime mode, the chemical reaction takes place by directly utilizing the absorbed solar radiation, while excess thermal energy is simultaneously transferred to a heat storage unit. In nighttime mode, the heat storage unit is discharged into the absorber. Here, the absorber acts as a heat exchanger, transferring the stored heat to the reactant. This enables continuous operation of the reactor, eliminating the need for an evening shutdown and morning start-up.

[0013] US 4,182,400 A describes a device for transferring heat between solid particles, comprising an inclined cylindrical drum in which a spiral screw is arranged. The outer lip of the screw, which is held in contact with the inner wall of the drum, is curved in the upward direction of the inclination axis. The screw blade has a plurality of openings of generally uniform size. A feed hopper is provided for introducing a first granular material into the upper end of the drum, the particles of this granular material generally being smaller than the size of the openings in the screw blade. A second feed hopper is used for introducing a second granular material into the lower end of the drum, the particle size of the second granular material generally being larger than the size of the openings. The drum and the screw conveyor are rotatable about the inclination axis.During rotation, the first granular material is sieved downwards through the openings in the screw blade inside the drum, while the second granular material is forced upwards through the screw blade. This brings the first and second materials into contact. A curved outer lip for the screw facilitates the downward movement of the first granular material, as it allows the material to move downwards through the openings in a nearly vertical direction. This, in turn, facilitates better counter-flow between the first and second granular materials, enabling heat exchange between them.

[0014] US 4,422,847 A describes methods and apparatus for preheating particulate glass mixtures with a rotatable drum for mixing the mixture with particulate heat transfer media in a heat transfer relationship, wherein the mixture is separated from the media in a media outlet chamber which has a screen through which the mixture passes and which has compartments attached for rotation about the axis of the drum in order to lift the separated mixture to the mixture inlet line where it is directed back into the drum.

[0015] DE 23 49 305 C3 describes a method for carrying out physicochemical exchange processes between a solid phase and a gas phase, in which a gas moves from bottom to top and a comminuted solid material moves from top to bottom due to gravity in a closed space, characterized in that the solid material moves step by step and remains at successive points for a period of time which is equal to the quotient of the desired total duration of the contact time and the number of successive points, as well as devices for carrying out the method.

[0016] Ermanoski et al. use a counterflow recuperator in the form of a vertical screw conveyor with an internal tube (I. Ermanoski, NP Siegel, EB Stechel, A New Reactor Concept for Efficient Solar-Thermochemical Fuel Production, Journal of Solar Energy Engineering, 135(3) (2013) 031002). In this design, heat transfer occurs between a solid wall and a bed of particles. The contact surface area is small compared to the surface area of ​​the particles. Furthermore, the transferred heat flux is significantly limited by the thermal conductivity of the bed. The rotation of the outer cylinder (also called an odds elevator) conveys the redox material against gravity, resulting in high material stress.

[0017] In the method investigated by Felinks et al., the particles are brought into direct contact with a similarly particulate regenerator (J. Felinks, S. Brendelberger, M. Roeb, C. Sattler, R. Pitz-Paal, Heat recovery concept for thermochemical processes using a solid heat transfer medium, Applied Thermal Engineering, 73(1) (2014) 1004-1011). This drastically increases the surface area used for heat transfer compared to the previously described concept. However, in this method, the different particle species are guided in co-current flow by gravity. By connecting several co-current heat exchanger stages, the temperature profile of a counter-current heat exchanger can be approximated, thus increasing the heat exchanger efficiency. However, the efficiency of a counter-current heat exchanger cannot be achieved due to the finite number of individual stages.Furthermore, the interconnection results in a significantly increased equipment requirement for conveying the particles.

[0018] The heat recovery method used in cement production, employing air as a heat transfer medium, is unsuitable for thermochemical cycles. The gaseous heat transfer medium would transport oxygen, which could oxidize the redox material, rendering it unavailable for the desired reaction.

[0019] In principle, any method in which heat is transferred to a particulate material is affected by the present invention. The fundamental objective is to improve heat transfer to particles while simultaneously enabling heat recovery. Therefore, a heat transfer method is needed that overcomes the disadvantages of the prior art. In particular, heat transfer should occur through direct contact between the heat transfer medium and the material to be heated, i.e., the particles. It should be possible to conduct the heat transfer medium and the particulate material to be heated in counterflow and subsequently separate them again.

[0020] Surprisingly, it has been found that a device according to claim 1, which includes at least one heat exchanger with at least one first supply line for a first material and at least one supply line for a second material, solves the problem underlying the present invention. In the heat exchanger according to the invention, the first material, which comprises a heat transfer medium, and the second material, which comprises particles, are brought into direct counter-current contact, thereby enabling heat to be transferred from one particulate material to the other.

[0021] A feed line within the meaning of the present invention is an opening through which the first and / or the second material can be introduced into the heat exchanger. The feed lines are designed such that a continuous process with the device is possible. However, the invention also includes the design of the feed lines such that batch operation is possible, i.e., that particles and heat transfer medium can be introduced through simple openings.

[0022] Mixing the heat transfer medium and particles enables a particularly efficient heat exchange. The heat-transferring surface area is significantly larger due to the direct contact between the particles and the heat transfer medium compared to indirect contact, for example, via a partition. Furthermore, there is no need for a partition wall, which would create thermal resistance and be subject to mechanical wear.

[0023] The device according to the invention offers the advantage over the prior art that it operates on a counterflow principle. This allows for effective heat transfer in a single, scalable stage. Fewer heat exchangers are therefore required compared to a quasi-counterflow principle, while simultaneously increasing heat transfer. Consequently, fewer particle conveying systems are needed, resulting in a lower overall equipment requirement. Furthermore, a solid, rather than a gas, is used as the heat transfer medium. This results in significantly lower volumetric flow rates. Moreover, the selection of an inert, solid heat transfer medium prevents any reaction between the particles and the gas. Additionally, any reaction gases can be easily separated from a particulate solid heat transfer medium. This would be associated with significant energy disadvantages when using a gaseous heat transfer medium.

[0024] The reduction in volumetric flow rates results from the fact that a gas always has a lower density than a solid. To heat particles, a certain amount of heat must be transferred from the heat transfer medium to the particles. Even assuming that the heat transfer medium and particles have the same heat capacity, the lower density of the gas results in a greater space requirement and / or a higher gas flow velocity. By using a solid, particulate heat transfer medium according to the invention, the volumetric flow rates are reduced by a factor of 10,000 to 20,000 compared to a gaseous heat transfer medium, which in turn results in a smaller apparatus and an overall smaller space requirement for the corresponding device.

[0025] The particulate heat transfer medium according to the invention is in the form of solid, in particular spherical, particles. Spherical particles within the meaning of the present invention are those particles that have at least a two-dimensional, in particular a three-dimensional, dimension. This dimension need not be regular in all spatial directions. Spherical particles within the meaning of the present invention are, for example, rod-shaped particles as well as spherical particles. The external shape of these particles can be regular or irregular. For example, the particulate heat transfer medium is a powder or granules. The total quantity / distribution of the particles need not be homogeneous, but can vary with regard to size and shape.

[0026] The particles are preferably solid, spherical particles. Spherical particles within the meaning of the present invention are those particles that have at least a two-dimensional, and in particular a three-dimensional, dimension. This dimension need not be regular in all spatial directions. Spherical particles within the meaning of the present invention are, for example, rod-shaped particles as well as spherical particles. The external shape of these particles can be regular or irregular. For example, the particulate heat transfer medium is a powder or granules. The total quantity / distribution of the particles need not be homogeneous, but can vary in size and shape. Here, too, a regular configuration is not necessary, but is included in the present invention.

[0027] To enable effective heat transfer, particulate heat transfer fluids and particles are brought into direct contact with each other in a counterflow heat exchanger. This results in heat transfer from the particulate heat transfer fluid to the particles. However, it is also possible that the particles have a higher temperature and then transfer heat to the particulate heat transfer fluid.

[0028] To enable intensive contact between the heat transfer medium and the particles, and also to achieve separation of the particles and the heat transfer medium after heat transfer, the device according to the invention further comprises at least one device for generating vibrations. Vibrations within the meaning of the present invention are all types of periodic or aperiodic oscillations. Periodic vibrations are preferred. These can, for example, have frequencies in the range of 0.01 Hz to 100,000 Hz. Vibration within the meaning of the present invention further includes any type of mechanical excitation of the mixture of particles between which heat is transferred. This can also be achieved by periodic or aperiodic impacts.It is also possible that the mechanical excitation of the mixture, which leads to the opposite movement of the particles involved, is caused by stirring, i.e. by rotating parts located within the mixture.

[0029] In Fig.Figure 1 shows a schematic representation of a device according to the invention, without depicting a device for generating vibrations. According to the invention, the vibration can be generated by a device attached to the outside of the heat exchanger. However, it is also possible for one or more corresponding devices, such as a rod, a piston, a probe, or other devices for generating vibrations, to be located inside the heat exchanger (5). This includes the presence of parts not involved in heat transfer, which, through their own movement, enable mechanical excitation and thus a vibration as defined in the present application. The choice of how the vibration is introduced from the outside or from the inside depends on the dimensions and geometry of the heat exchanger. In principle, the heat exchanger (5) can have any geometric shape and size.The installation of suitable devices for generating vibrations is then the responsibility of a person skilled in the art. Care must be taken to ensure that the vibration fills the entire volume of the heat exchanger in order to guarantee complete separation of particles (7) and the heat transfer medium (6).

[0030] How Fig. As can be seen in Figure 1, the vibration can, for example, be linear. Arrow (8) indicates one possible spatial direction. However, it is also possible for the vibration to be transmitted rotationally. Vibrations in any spatial direction are conceivable and possible. The vibration can be transmitted in one or more spatial directions.

[0031] It has been shown that, under the influence of vibration, good heat transfer occurs between the heat transfer medium (6) and the particles (7). Heat transfer means that heat can be transferred either from the heat transfer medium (6) to the particles (7) or vice versa. Following heat transfer, the particles (7) and the heat transfer medium (6) separate. This separation is caused by the vibration. It has been shown that particularly good separation is possible because, according to the invention, the heat transfer medium (6) and the particles (7) have different densities. The separation behavior can also be optimized by appropriately selecting the diameters of the particles (7) and / or the heat transfer medium (6).

[0032] To enable a counterflow principle, according to the invention, the first inlet (1) is located further down on the heat exchanger (5) than the second inlet (2), in accordance with gravity. According to the invention, the heat exchanger (5) may have not only one first inlet (1) and one second inlet (2), but may also comprise several first and / or second inlets (1 or 2). These are arranged symmetrically, in particular. For example, if the device according to the invention comprises two second inlets (2), these are preferably arranged opposite each other. If the device according to the invention comprises several second inlets (2), these are arranged symmetrically, for example, so that there is an equal distance between all inlets (2).However, it is also possible for the supply lines (2) to be arranged asymmetrically and, for example, to be located in one spatial direction on one side of the heat exchanger (5). Several supply lines (2) can, for example, be arranged side by side, or two supply lines can be arranged side by side and a further supply line opposite them. Any such arrangement is encompassed by the present invention. Preferably, the supply lines are located on the same plane. The same applies, of course, if more than one first supply line (1) is present. According to the present application, the particles (7) rise from top to bottom and the heat transfer medium (6) rises from bottom to top in the heat exchanger (5) in accordance with the force of gravity.

[0033] In a batch process, it is also possible for the first and second feed lines to be identical. Here, the heat transfer medium (6) and particles (7) are placed one above the other in the heat exchanger (5) in a step preceding the heat transfer process and then vibrated. This causes the heat transfer medium (6) and particles (7) to move in opposite directions within the heat exchanger (5), resulting in the separation of the particles (7) and the heat transfer medium (6). The separated materials can then be removed from the heat exchanger one after the other. This can be done through suitable outlets at the bottom or top of the heat exchanger (5). For the next batch, the heat exchanger (5) is then refilled accordingly.

[0034] However, depending on the use of the device and the selection of the materials of the particles and heat transfer medium, it is also possible that, in the sense of gravity, the particles (7) are introduced into the heat exchanger (5) from below and the heat transfer medium (6) is introduced into the heat exchanger (5) from above.

[0035] The particles (7) are preferably introduced via the second supply line (2). The heat transfer medium (6) is then introduced into the heat exchanger (5) via the separate first supply line (1). It is possible for the particles (7) and / or the heat transfer medium (6) to be introduced into the heat exchanger (5) by gravity. For example, a funnel or similar filling device may be provided through which the particles (7) enter the heat exchanger (5) by gravity. The heat transfer medium (6) can also be introduced into the heat exchanger (5) in a similar manner. Preferably, the material that is introduced into the heat exchanger (5) from below by gravity is actively introduced. This can be done, for example, by means of a screw conveyor, vibratory system, chute, pipe, and / or conveyor belt.The material is introduced into the heat exchanger (5) through the pipe by means of the pressure generated by its weight. This is comparable to an effect similar to a hydrostatic pressure difference, which causes the particle column to be drawn into the heat exchanger from the bottom. The material is also introduced into the heat exchanger (5) under pressure by the other devices, so that the material tends to rise upwards within the heat exchanger (5) against gravity. This supports the separation effect caused by the vibration.

[0036] As in Fig.As shown schematically in Figure 1, the heat transfer medium (6) is introduced into the heat exchanger (5) from below – in the direction of gravity. Due to vibration and, if applicable, pressure caused by devices for introducing the heat transfer medium (6), the heat transfer medium (6) rises upwards inside the heat exchanger (5). At the corresponding end, there is a first outlet (3) through which the heat transfer medium (6) then exits the heat exchanger (5).

[0037] According to the invention, the outlet (3) can be designed as an overflow. This means that the heat transfer medium (6) is forced upwards out of the heat exchanger (5) due to the continuously flowing material. In this case, the device according to the invention can include a corresponding collection container in which the heat transfer medium (6) is collected and stored for further use as needed. However, it is also possible for a line to be connected to the first outlet (3) in which the heat transfer medium (6) is then transported directly.

[0038] The particles (7) introduced into the heat exchanger (5) via the second inlet (2) migrate downwards due to gravity. This is made possible by the vibration, despite the presence of the heat transfer medium (6) in the heat exchanger (5), so that, due to the separation of the materials, the particles (7) collect at the bottom of the heat exchanger at the end of the heat transfer process, again due to gravity. Preferably, the heat exchanger (5) has a design at this second outlet (4) such that the outflow of the particles (7) from the heat exchanger (5) can be controlled. This allows for control of the contact time between the particles (7) and the heat transfer medium (6) and thus control of the heat transfer between the materials.

[0039] One possibility is to attach a sieve to the second outlet (4). This sieve can be opened and closed as needed. Furthermore, the sieve should have a mesh size such that only particles (7) and not the heat transfer medium (6) can pass through. In such a configuration, the particles (7) and the heat transfer medium (6) preferably have different particle sizes.

[0040] Furthermore, according to the invention, it is also possible that a screw conveyor or other transport device is connected to the second outlet (4), with which the particles (7) are transported, for example, to a reactor and are available there for a reaction. It is also possible that a rotary valve, such as a rotary valve, is provided, which allows the quantity of particles (7) exiting the heat exchanger (5) within a defined period to be controlled.

[0041] The particle size in the context of the present invention is the average particle size. For particles with irregular geometric dimensions in different spatial directions, a specified diameter corresponds to the largest spatial dimension. The particle size can be determined by image analysis, for example, of scanning electron micrographs, camera images or scans, sieve analysis, laser diffraction, or light scattering. Preferably, the heat transfer medium (6) has a larger particle size than the particles (7). Generally, heat transfer is better with smaller particles than with larger particles; therefore, both the particle size of the particles (7) and that of the heat transfer medium (6) are as small as possible, but preferably different from each other.

[0042] An optimal particle size depends on many factors. Besides the best possible heat transfer, handling, stability, and other aspects also play a role. Preferably, however, the particle size of the particles (7) is in the range of 0.01 mm to 200 mm, particularly in the range of 0.1 mm to 3 mm. The particle size of the heat transfer medium (6) is preferably in the range of 0.1 mm to 100 mm, particularly in the range of 0.5 mm to 10 mm. The particle size is determined using the methods described above.

[0043] The device according to the invention further comprises various internal components inside the heat exchanger (5), such as ribs, screws, projections, protrusions or depressions, which enable the control of the flow direction and the flow behavior of the particles (7) and / or the heat transfer medium (6).

[0044] Furthermore, it is also possible that the device according to the invention, following the force of gravity, has a device on its underside for introducing a gas. This gas can lead to fluidization of the material mixture in the heat exchanger (5). The resulting fluidized bed results in faster and more effective separation than vibration alone, so that the velocity or the duration of the materials' residence time in the heat exchanger (5) can be reduced. In addition, further heat transfer can occur through the gas.

[0045] In a further embodiment, the present invention relates to a method according to claim 6 for transferring heat from a particulate heat transfer medium (6) to particles (7) and vice versa. The method according to the invention is characterized in that the heat transfer medium (6) and the particles (7) are brought into direct contact in a heat exchanger (5) and guided in countercurrent flow under the influence of vibration. In a preferred method, the heat transfer medium (6) is circulated in a closed loop. This means that the heat transfer medium (6), after leaving the heat exchanger (5), is used in a further heat exchanger. Alternatively, it is also possible that the heat transfer medium (6) is further heated before entering the further heat exchanger and is then available again in the method according to the invention.If heat is removed from the process via the heat transfer medium, the heated medium can also release this heat into another process or further increase the temperature in that process. If heat is introduced into the process via the heat transfer medium, the medium can also be heated externally. This heating can be achieved particularly through non-fossil energy (sun, wind, water) and preferably through concentrated solar radiation. The thermal utilization of solid, liquid, or gaseous fuels from renewable or fossil sources is also conceivable. These include, for example, biomass, waste, or synthetically produced hydrocarbons.

[0046] In a preferred embodiment, the present invention therefore relates to a method in which the heat transfer medium (6) is first heated. This is done in particular by means of concentrated solar radiation. Subsequently, the heat transfer medium (6) is introduced into the heat exchanger (5) via the first supply line (1). The heat transfer to the particles (7) then takes place in the heat exchanger (5).

[0047] The process according to the invention can, for example, be a process for carrying out chemical reactions consisting of at least two sequential reversible steps in a cycle, a process for processing foodstuffs, in particular grain, or cement production.

[0048] Possible applications include heat recovery and a reactor for solar thermochemical water or carbon dioxide splitting, or heat recovery and a reactor for solar or conventional cement production. In principle, all processes involving the use of particles and heat transfer are covered by the present invention, such as in food processing (e.g., the thermal treatment of grain), chemical processes using particles as catalysts or reaction materials, or heat exchangers between thermochemical storage materials and heat transfer media. Thermal processes for energy generation, preferably electricity production, with thermal cycles, such as the Clausius-Rankine or Brayton cycle, are also potential areas of application.

[0049] In the method according to the invention, vibration enables opposing movement of particles (7) and heat transfer medium (6) during heat transfer. According to the invention, the vibration can be applied continuously throughout the entire heat transfer process. However, it is also possible for the vibration to be intermittent and to be regularly or irregularly interrupted by periods in which no vibration acts on the heat exchanger.

[0050] The vibration can be transmitted, for example, mechanically, by sound, or by a magnetic field or an electric field.

[0051] The vibration causes a relative movement of particles (7) and heat transfer medium (6) within the heat exchanger (5). The particles (7) move due to gravity, while the heat transfer medium (6) is displaced upwards in the vibrating mixture due to buoyancy effects. The material with the lower density is displaced upwards. If particles (7) and heat transfer medium (6) with different initial temperatures are introduced into the heat exchanger (5), heat exchange occurs according to the invention via a counterflow principle. While less efficient, heat exchange via a parallel-flow or cross-flow principle is also possible. This applies, for example, when heat transfer is not continuous but occurs in batch operation.

[0052] The selection of the heat transfer medium (6) depends on the type of process and thus also on the type and properties of the particles (7) as well as on how the vibration is introduced into the heat exchanger (5). Preferably, the heat transfer medium (6) comprises a ceramic material to ensure stability at the prevailing temperatures. Furthermore, the heat transfer medium must be designed such that it does not undergo a chemical reaction with the particles (7), so that after heat transfer, the heat transfer medium (6) and the particles (7) remain unchanged. If the vibration is achieved, for example, by applying an electric field, the particles (7) and / or the heat transfer medium (6) are electrically and / or magnetically conductive. The same applies accordingly if the vibration is achieved by applying a magnetic field. In this case, the particles (7) and / or the heat transfer medium (6) are magnetic.

[0053] The material of the heat transfer medium (6) must be solid at all times, i.e., at every prevailing temperature during the process. While temperatures significantly above 100 °C are not expected during food drying, temperatures of 1000 °C and above occur in thermochemical cycles or cement production. Accordingly, temperature-resistant ceramics are preferred in these cases, whereas in processes involving only lower temperatures, temperature-resistant plastics or metals or alloys can also be used.

[0054] In a preferred embodiment, the heat transfer medium (6) is selected from the group comprising ceramics, high-temperature-resistant alloys, rock, and mixtures thereof. Possible examples are given below: • Oxide ceramics and non-oxide ceramics, both of which can exist in different valence states, for example made of: ◯ Metals: Al2O3, AlN ◯ Semimetals: SiO2, Si2N4, SiC, B4C ◯ Transition metals: TiO2, Y2O3, ZrO2, HfO2, TiN ◯ Alkaline earth metals: MgO2 ◯ Lanthanides: CeO2 ◯ Technical mixtures: Steatite, Cordierite, Mullite, Concrete • Metals and alloys such as Pt, W, Ta, Mo, nickel-based alloys, high-temperature resistant steels • Natural materials / minerals such as quartz, gneiss, basalt, granite, limestone, chert (hornstone), rock salt and others

[0055] If the process is a process for carrying out a chemical reaction consisting of at least two sequential reversible steps in a cyclic process, then this process preferably comprises the following steps: a) Heating the particles (7) to temperature T1, b) Reduction of the particles (7) in a first reaction chamber (12) at a first temperature T1 with elimination of oxygen, c) Transfer of heat from the particles (7) to the heat transfer medium (6) to cool the particles (7) from temperature T1 to temperature T2 in the first heat exchanger (14), d) Oxidation of the particles (7) in the second reaction chamber (13) at a second temperature T2, e) Transfer of heat from the heat transfer medium (6) to the particles (7) in the second heat exchanger (15) to heat the particles (7), the subsequent cycle comprising the aforementioned steps a) to e). Thus, in the first heat exchanger (14), after the reaction in the first reaction chamber (12) has been completed, sensible heat from the particles (7) is transferred to a heat transfer medium (6) at temperature T1. In a second heat exchanger (15), after the reaction in the second reaction chamber (13) has been completed, this heat absorbed by the heat transfer medium (6) in the first heat exchanger (14) is transferred back to the particles (7) at temperature T2. Temperature T1 is higher than temperature T2. Therefore, this variant is a heat exchanger / heat recovery system between particles of the same species, with another particle species used as an intermediate storage medium, a so-called regenerator.

[0056] In Fig. Figure 2 schematically shows a reactor of a preferred embodiment in which the preferred method according to the invention can take place.

[0057] The preferred method now allows the heat exchangers (14, 15) to be designed according to the invention as shown in Fig. As shown in Figure 1, effective heat transfer occurs. Since heat transfer takes place both from the particles (7) to the heat transfer medium (6) – in the second heat exchanger (15) – and from the heat transfer medium (6) to the particles (7) – in the first heat exchanger (14) – the heat introduced into the system is used for a longer period, thus saving energy. If the particles (7) are also heated using non-fossil energy sources, such as solar, wind, or hydropower, fossil fuels are saved and CO2 emissions are significantly reduced or even eliminated.

[0058] In this embodiment, the particles (7) are then directed from the first reaction chamber (12) into the first heat exchanger (14). In this heat exchanger (14), the heat from the particles (7) is transferred to a second heat transfer medium (6). The particles (7), cooled in this way, are then used in the second reaction chamber (13), where the splitting step of water or carbon dioxide can take place. Subsequently, they are reheated in the second heat exchanger (15) by means of the second heat transfer medium (6).

[0059] The heat transfer medium (6) is heated by concentrated solar radiation (18), for example, in a receiver (16). Before the heated heat transfer medium (6) is added to the cycle, it can be stored, for example, in a storage tank (hot storage tank) (17).

[0060] In a preferred embodiment, a first heat transfer medium (6) is heated in a receiver (16), in particular by means of concentrated solar radiation (18). The heated heat transfer medium (6) is stored in a first storage tank (hot storage) (17) before being used to heat the particles (7) in the first reaction chamber (12). In the first reaction chamber (12), the first heat transfer medium (6) releases its heat, thereby cooling down. The now cooled first heat transfer medium (6) can then be stored in a second storage tank (cold storage) (19) before being heated again in the receiver (16).

[0061] According to the invention, the particles (7) are thus cooled in the first heat exchanger (14) from the high temperature level T1 after reduction in the first reaction chamber (12) to the lower temperature level T2, which then prevails in the second reaction chamber (13). The particles (7) are then preheated again in the second heat exchanger (15). In step c), the heat from the particles (7) cannot be completely transferred to the heat transfer medium (6). Complete heat recovery would be desirable, but is only theoretically possible. However, the counterflow principle according to the invention allows for a significantly higher heat transfer than is possible with the methods described in the prior art.

[0062] If the particles (7) in the heat exchanger (14) do not yet reach temperature level T2, additional heat is dissipated to the environment or to another process. Complete heat transfer from the heat transfer medium (6) to the particles (7) is not necessarily possible even in step e) of the inventive method. Here, the heat transfer in the second heat exchanger (15) results in a significant warming of the particles (7), so that if reheating is necessary, only a small amount of heat needs to be added to reach temperature level T1.

[0063] The temperature of the particles (7) during the oxidation reaction in the second reaction chamber (13) is lower than during the reduction reaction in the first reaction chamber (12). In the process according to the invention, the sensible heat present in the particles in the first reaction chamber (12) can be stored by means of the heat transfer medium (6) and then used to heat the particles (7), which have a temperature T2 after the oxidation reaction. Complete heating to temperature T1 can be achieved with optimal heat transfer and insulation. However, it may also be necessary to heat the particles (7) using other energy sources if the temperature T1 for the solid reactant cannot be reached by the heat transfer medium (6). Such energy sources are well described in the literature.For example, heat can be generated using fossil fuels, nuclear energy, or alternative energy sources (wind, solar, water), which is then fed into the process according to the invention. Preferably, any necessary heating is carried out using alternative energy sources, preferably using solar radiation, in particular concentrated solar radiation.

[0064] Sequential steps within the meaning of the present invention are successive reaction steps of a chemical reaction in which the reaction products can be isolated. Reversible steps within the meaning of the present invention are reaction steps in which the chemical equilibrium can be adjusted so that either the forward or reverse reaction preferentially proceeds.

[0065] A circular process within the meaning of the present invention consists in the fact that the at least two sequential reversible steps are always carried out one after the other.

[0066] A chemical reaction within the meaning of the present invention is, in principle, any chemical reaction that is carried out in the presence of a solid reactant in the form of particles (7). The particles (7) are preferably chemical compounds with redox properties. Chemical compounds with redox properties within the meaning of the present invention are those compounds that can be reversibly oxidized and reduced. Advantageously, these chemical compounds with redox properties are selected from the group consisting of metal oxides, mixed metal oxides, doped metal oxides, and mixtures thereof. Metal oxides are particularly preferred because they are the most versatile. The use of a multivalent metal oxide as particles (7) has proven to be particularly advantageous because it is especially easy to regenerate, i.e., it can readily switch between the oxidized and reduced states.Multivalent within the meaning of the invention is a metal oxide that has several oxidation states side by side, and in particular when the metal is present in an oxidation state > +1, in particular > +2.

[0067] Preferably, the metal oxides comprise ferrites and / or zinc oxides and / or manganese oxides and / or lanthanum oxides and / or cerium oxides and / or perovskites and / or oxides of the general formula M x 2+ Zn 1-x 2+ Fe2O4, where M x 2+ A divalent metal ion selected from the group consisting of magnesium, calcium, manganese, iron, cobalt, nickel, copper, zinc, strontium, tin, barium, cadmium, and lead, whereby mixtures of the oxides can also be used. Mixtures of the oxides are used particularly when hydrogen elimination is desired, as they are especially efficient in this regard. Basically, in the general formula M x 2+ Zn 1-x 2+Fe2O4 x a number in the range of 1 to 5, in particular from 2 to 3. Cerium oxide is preferably used as a metal oxide.

[0068] The inventive method is preferably used for the following exemplary reaction types: reaction type First step Second step H2 production MeO x +H2O→H2+MeO y MeO y →MeO x +½O2 Carbon dioxide reduction MeO x +CO2→MeO y +CO MeO y →MeO x +½O2 Splitting of nitrogen oxides MeO x +NO z →MeO y +½N2 MeO y →MeO x +½O2 Division of MeO x +SO3→MeO y + MeO y →MeO x +½O2 SO3 / Production of SO2 SO2 Selective oxidation MeO x +½O2→MeO y C m H n +MeO y →MeO x +C m H n Oh Dehydration MeO x +½O2→MeO y C m H n +MeO y →MeO x +CmH n -2+H2O H2 production Me + H2O → H2 + MeO MeO→Me+½O2 H2 production MX y +HX→MX y+1 +½H2 MX y+1 →MX y +½X2

[0069] The table shows the reaction equations for stoichiometric reactions. However, it is also possible for the reactions to proceed non-stoichiometrically. The corresponding adjustment of the reaction equation is well known to those skilled in the art. In the table, Me represents a metal atom, X a halogen or pseudohalogen, and subscripts n, m, x, y, or z denote positive numbers. These can be integers. Since the reactions do not always proceed stoichiometrically, the subscripts can also represent real numbers.

[0070] The process according to the invention can, in particular, split water into hydrogen and oxygen. Furthermore, it is possible to split CO2 into CO and oxygen. The process according to the invention is preferably a process for splitting water into hydrogen and oxygen, or CO2 into CO and oxygen. Here, hydrogen is produced from water vapor or carbon monoxide from carbon dioxide in a cyclic process, preferably at temperatures in the range of 800 °C to 1,200 °C. For example, a metal oxide system is used in the cyclic process, which can split oxygen from water molecules or from carbon dioxide and reversibly incorporate it into its crystal structure.

[0071] In this cycle, the release of oxygen and its incorporation into the particles (7) takes place at a second temperature T2. The subsequent release of oxygen from the particles (7), which reduces their size, occurs at a first temperature T1. To start the cycle, the particles (7) must first be heated to temperature T1. According to the invention, this is preferably done using concentrated solar radiation. It is possible to heat the particles (7) themselves or to heat the heat transfer medium (6) and transfer heat from it to the particles (7) in a heat exchanger (14).

[0072] As in Fig. As shown schematically in 2, the preferred method according to the invention in this embodiment comprises three independent particle cycles. In a first cycle (cycle 1) (9), which in Fig.As shown in the dashed line 2, the first heat transfer medium is circulated. This includes heating in the receiver (16), storage in the first storage tank (17), transfer of heat from the first heat transfer medium to the particles (7) in the first reaction chamber (12), and storage of the then cooled heat transfer medium in the second storage tank (19).

[0073] In another cycle (Cycle 3) (11), which in Fig.As shown in Figure 2 by dotted lines, a second heat transfer medium is circulated. This includes the absorption of heat from the particles (7) in the first heat exchanger (14) and the release of heat to the particles (7) in the second heat exchanger (15). The first and second heat transfer media can be different from each other. It is also possible for the first and second heat transfer media to be the same. Separating the two heat transfer circuits has the advantage of improving the efficiency of the process.

[0074] The particles (7) are also circulated in the process according to the invention (circulation 2) (10). This circulation corresponds to the process in a thermochemical cycle. In addition, heat transfer to a heat transfer medium (6) and from the heat transfer medium (6) to the particles (7) takes place between reduction and oxidation in the first reaction chamber (12) and the second reaction chamber (13), respectively.

[0075] According to the invention, the heat transfer medium (6) has the function of absorbing, storing, and releasing sensible heat, which is required for heating particles (7) in various processes and is contained in the process. In a preferred embodiment, if the heat transfer medium (6) is heated by means of concentrated solar radiation (18), it additionally serves as an absorbing medium for the highly concentrated solar radiation. The hot heat transfer medium (6) can be stored and supplied to a reaction chamber as needed.

[0076] In a preferred embodiment, the present invention relates to a reactor according to claim 12, which is characterized, among other things, in that it comprises two reaction chambers (12, 13) and at least two heat exchangers (14, 15) with a particulate heat transfer medium (6), wherein in the heat exchangers (14, 15) particles (7) and heat transfer medium (6) are brought into direct contact with each other in countercurrent flow, whereby an exchange of heat takes place and the particles (7) and the heat transfer medium (6) are separated from each other by means of vibration.

[0077] In a preferred embodiment, the reactor further comprises a receiver (16). In this receiver (16), the heat transfer medium (6) can be heated, for example, by concentrated solar radiation (18). This allows for any geometric arrangement of the receiver (16) facing the solar radiation (18), thus enabling effective heating. Alternatively, heating can be achieved, for example, using fossil fuels, nuclear energy, or other known methods of generating heat energy. However, it is also possible to heat the particles (7) in the receiver (16) and only then feed the particles (7) into the actual cycle (10).

[0078] According to the invention, a reactor comprises at least one, preferably at least two, devices according to the invention with a heat exchanger (5). In this heat exchanger, not only does the heat exchange take place, but the desired reaction occurs simultaneously. This reduces the equipment complexity and increases efficiency. The vibration does not affect the actual chemical reaction. An advantage is that, according to the countercurrent principle, the most reacted material reaches the highest temperature.

[0079] Unlike in Fig.Figure 2 shows that the reactor is not to be connected as a direct current reactor, but as a countercurrent reactor. The reactor for the fission step can also be implemented using the design according to the invention. The heat from the exothermic fission reaction is carried away from the reactor by the heat transfer medium. During the design, care must be taken to ensure that at least one, preferably several, gas inlets and at least one, preferably several, gas outlets are installed. This allows the reactant and product gases to be supplied and discharged, respectively.

[0080] In a further embodiment, the process according to the invention is the production of cement. In cement production, a mixture of limestone, clay, sand, and iron ore is fired at approximately 1400 °C. The sensible heat can be recovered from the product, the so-called clinker (particles (7)), to reduce the overall energy requirement of the process. The clinker is cooled by transferring the sensible heat to the heat transfer medium (6). This process can also be operated with concentrated solar radiation instead of fossil fuels, as currently described in the prior art. A reactor in which the cement production takes place essentially comprises a similar structure to that described in Fig. The reactor shown represents the cycle. In this process, only the endothermic reaction, calcination, is relevant. Furthermore, the reactant and product are not recyclable, but rather added to and removed from the process.

[0081] In another embodiment, the method according to the invention is a method for treating foodstuffs, for example for drying grain.

[0082] While simple aeration of grain aims to reduce the heat stored in the kernels during harvesting, drying is intended to bring the grain into a storable state. Dried grain can be transported safely and poses no problems during marketing. Therefore, grain drying is a standard storage method and is predominantly used by cooperatives, agricultural traders, and farms with large quantities of stored grain.

[0083] The warm air required for drying is usually generated using propane, natural gas, or oil burners. The temperature of the drying air must be adjusted to the grain moisture content. Excessively high temperatures lead to heat damage to the grain. After drying, a further cooling process is generally necessary to bring the warm grain down to a storage temperature of no more than 20 °C, ideally 15 °C.

[0084] The method according to the invention now makes it possible to heat the grain (corresponding to the particles (7)) by means of a heat transfer medium (6) and thus drive off the moisture. Due to the reduced volume flow compared to gas drying, less equipment is required. The subsequent cooling can also be carried out by means of a suitable heat transfer medium (6) in a device according to the invention.

[0085] The inventive method can also be used here for heat recovery. The grain (corresponding to particles (7)), heated for drying and subsequently cooled, is brought into contact with the heat transfer medium (6) in the described counterflow heat exchanger. There, it transfers heat to the heat transfer medium (6). The thus heated heat transfer medium (6) can then transfer heat to the incoming grain, which is to be heated for drying, in a further heat exchanger. Thus, a large part of the required heat can be saved in this method, thereby improving efficiency. Example implementation:

[0086] Aluminium oxide particles with an average size of 5 mm and a density of 3700 kg / m³ were used as the heat transfer medium (6). 3 used.

[0087] The particles (7) were zirconium oxide-cerium oxide particles with an average size of 0.8 mm and a density of approximately 6200 kg / m3.

[0088] The heat transfer medium (6) was placed at the bottom of a 0.5 liter beaker. The particles (7) were then added over the heat transfer medium (6). The heat transfer medium (6) and the particles (7) had comparable total volumes. The beaker was approximately ¾ full.

[0089] The beaker was placed on a metal sheet, through which a vibration was transmitted to the beaker and the materials inside. The beaker was fixed to the sheet with a thin film of pressure-sensitive adhesive and was thus firmly bonded to the sheet for the duration of the applied vibration.

[0090] Immediately after the vibration began, the heat transfer medium (6) and particles (7) moved. The heat transfer medium (6) rose upwards, and the particles (7) moved towards the bottom of the beaker. After a few minutes, the separation was complete. The particles (7) were entirely at the bottom of the beaker, while the heat transfer medium (6) was located above the particles (7).

[0091] This experiment corresponds to a batch process. However, the heat exchanger (present invention) can also be operated in continuous mode, which is particularly desirable.

Claims

[1] Device comprising at least one heat exchanger (5) with at least one first inlet (1) for a first material and at least one second inlet (2) for a second material, wherein the first material comprises a particulate heat transfer medium (6) and the second material comprises particles (7), wherein the heat transfer medium (6) and the particles (7) are brought into direct contact with each other in the heat exchanger (5) in a counterflow, whereby heat can be transferred from one particulate material to the other, and at least one device for generating vibrations, wherein the heat transfer medium (6) and the particles (7) have different solid densities, wherein the first inlet (1) is located further down on the heat exchanger (5) than the second inlet (2) in accordance with gravity, wherein in the heat exchanger (5) the particles (7) can rise from top to bottom and the heat transfer medium (6) can rise from bottom to top in accordance with gravity,and wherein the device further comprises various internal components inside the heat exchanger (5) such as ribs, screws, projections, protrusions or depressions which can direct the flow direction and influence the flow behavior of the particles (7) and / or the heat transfer medium (6). [2] Device according to claim 1, characterized by that it further has a first outlet (3) for the heat transfer medium (6) and a second outlet (4) for the particles (7), wherein the second outlet (4) is in particular designed such that the particles (7) can be removed from the heat exchanger (5) in a controlled manner. [3] Device according to claim 2, characterized by , that the second outlet (4) has a sieve, a screw conveyor or a sluice gate, in particular a rotary valve. [4] Device according to any one of claims 1 to 3, characterized bythat it further includes a device for introducing the heat transfer medium (6) and / or the particles (7). [5] Device according to claim 4, characterized by that the device is a screw conveyor, a vibratory conveyor, a chute, a pipe and / or a conveyor belt. [6] Method for transferring heat from a particulate heat transfer medium (6) to particles (7) and vice versa, characterized by , that the heat transfer medium (6) and particles (7) are brought into direct contact with each other in a heat exchanger (5) in counterflow under the influence of vibration, wherein the heat transfer medium (6) and particles (7) have different solid densities, wherein in the heat exchanger (5) the particles (7) rise from top to bottom and the heat transfer medium (6) rises from bottom to top in the direction of gravity. [7] Method according to claim 6, characterized by, that the heat transfer medium (6) is heated, then introduced into the heat exchanger (5) via the first supply line (1) and there transfers the heat to the particles (7). [8] Method according to claim 6 or 7, characterized by , that the heat transfer medium (6) and / or the particles (7) are carried in a cyclic process. [9] Method according to any one of claims 6 to 8, characterized by that it is a process for carrying out a chemical reaction consisting of at least two sequential reversible steps in a cycle, a process for processing foodstuffs or cement production. [10] Method according to claim 6 or 7, characterized by, that the heat transfer medium (6) and particles (7) are placed one above the other in the space of the heat exchanger in a step preceding the heat transfer and are then subjected to vibration, causing the heat transfer medium (6) and particles (7) to move in opposite directions within the heat exchanger (5), thereby separating the particles (7) and the heat transfer medium (6). [11] Reactor for carrying out a process according to one of claims 6 to 8 or 10, comprising a device according to one of claims 1 to 5, wherein in the heat exchanger (5) in addition to the heat transfer, a further reaction, in particular a chemical reaction consisting of at least two sequential reversible steps, takes place. [12] Reactor for carrying out a chemical reaction consisting of at least two sequential reversible steps in a cycle according to claim 9, comprising two reaction chambers (12, 13), and at least two devices according to any one of claims 1 to 5 with two heat exchangers (14, 15), wherein which comprise at least two heat exchangers (14, 15) and a particulate heat transfer medium (6), and In the heat exchangers (14, 15) particles (7) and heat transfer medium (6) are brought into direct contact with each other in counterflow, whereby an exchange of heat takes place and the particles (7) and the heat transfer medium (6) are separated from each other by means of vibration.

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