Thermal energy storage device

Abstract

The invention relates to a method for guiding the flow of fluids for charging and discharging a thermal energy storage device, comprising a storage volume (2, 2') with a storage material (3), wherein the storage volume (2, 2') is divided into an inner storage volume (2) and an outer storage volume (2'). The flow guidance is characterized in that, during a charging process, the fluid flows through the inner storage volume (2) from bottom to top and then through the outer storage volume (2') from top to bottom after the flow (S) of the fluid is deflected, whereas, during a discharging process, the fluid flows through the outer storage volume (2') from bottom to top and then through the inner storage volume (2) from top to bottom after the flow (S) of the fluid is deflected.

Description

[0001] THERMAL ENERGY STORAGE DEVICE

[0002] The present invention relates to a method for guiding the flow of fluids for loading and unloading a thermal energy storage device and to a thermal energy storage device for utilizing waste heat from the iron and steel industry, comprising a cylindrical housing with a storage volume, wherein the storage volume has external inlets and outlets and a two-part storage material.

[0003] BACKGROUND OF THE INVENTION

[0004] Thermal energy storage plays a crucial role in increasing energy efficiency. In addition to the benefits of climate and resource protection, expanding this sector also leads to greater economic viability. The iron and steel industry, as well as the cement industry, can particularly benefit, as they generate large quantities of unused high-temperature waste heat and use fossil fuels to produce heat. Utilizing this previously unused waste heat is challenging due to its highly fluctuating availability, the high temperatures involved, and the high dust content in the transported exhaust gases.

[0005] The state of the art describes various solutions to this problem, most of which involve systems filled with a heat storage material. This material can be heated or charged by a flow of fluid, provided the fluid temperature is higher than that of the heat storage material. Conversely, the stored energy can be recovered or the storage material discharged by passing a fluid at a lower temperature through it.

[0006] EP 2 833 092 A2 discloses a method and a storage device for energy storage. In the method, a solid heat storage medium is heated via a coupling element, which is heated by electromagnetic induction. The heat is transferred from the coupling element to the heat storage medium by a fluid heat exchanger. For heat input, the fluid heat exchanger is heated by the coupling element and flows around it to transfer the heat. For heat extraction, the heat exchanger flows around or through the heat storage medium. In one embodiment, the storage device includes, among other things, a medium container surrounded by a ring-shaped heating element.

[0007] CN 116576706 A describes a heat storage device comprising a vertical box divided into high- and low-temperature zones, a heat-insulating partition located inside the vertical box, a latent heat storage module situated above a high-temperature settling chamber, a solid-state heat storage module situated above the low-temperature settling chamber, an air duct, and a flue duct connected to the high-temperature settling chamber. The high-temperature settling chamber serves to separate and remove solid particles from dusty flue gas, while the latent heat storage module serves to store the heat from the dusty high-temperature flue gas.

[0008] WO 2020 / 115131 discloses a method for exporting a cyclic energy storage system for a process chamber in cyclic operation using a storage medium with a hot side and a cold side. The method comprises heating the energy storage medium on the hot side, continuously recording the sensor values ​​on the cold side, and, upon reaching a limit value, supplying a cold medium to the cold side of the energy storage medium and discharging the stored energy.

[0009] EP 3 339 790 Al shows a heat exchanger with a gas inlet, gas outlet and gas flow path extending from the gas inlet to the gas outlet.

[0010] EP 2 989 405 Bl describes a thermal energy storage device which includes a packed rock bed consisting of individual rock units as heat storage material and a channel which allows a fluid to flow in and out, making it possible to load and unload the heat storage material.

[0011] Furthermore, WO 2009 / 103106 A2 describes a device for thermal energy storage. The device comprises a container divided by a partition wall with heat storage materials in both parts of the container, the concentric shape resulting in a hot core zone, which is heated by means of a heating medium or hot air supply, and a surrounding ring zone that can absorb the heat from the core zone and thus reduce heat losses.

[0012] BRIEF DESCRIPTION OF THE INVENTION

[0013] The devices described in EP 2 989 405 Bl and WO 2009 / 103106 A2 essentially solve the problem of charging a thermal storage system with waste heat. The device described in WO 2009 / 103106 A2 accomplishes this task with the added benefit of reduced heat loss. However, charging such thermal storage systems with dust-laden industrial exhaust gases presents a significant challenge due to two conflicting effects. Since dust particles tend to settle in the storage material, particularly in the inlet zone of the hot exhaust gases, during the charging process, it is advantageous to charge the storage system from the bottom and discharge it from the top to remove these dust deposits. This allows gravity to assist in the removal of the dust particles.From a thermal point of view, however, it is optimal to load the storage unit from the top and discharge it from the bottom, since in this case the effect of gravity helps to stabilize the thermocline, which forms a separating layer between the hot and cold storage zone, within the storage unit.

[0014] The object of the present invention is therefore to provide a method for a novel flow guidance of a thermal energy storage device as well as a thermal energy storage device, whereby the aforementioned disadvantages and contradictions are avoided or resolved.

[0015] This problem is solved by a method according to claim 1. This method is for guiding the flow of fluids for charging and discharging a thermal energy storage device, comprising a storage volume containing a storage material, wherein the storage volume is divided into an inner storage volume and an outer storage volume, the division of the two storage volumes preferably being concentric. During the charging of a thermal energy storage device with fluids or exhaust gases, which are preferably dust-laden, the flow through the inner storage volume is from bottom to top, causing dust and tar to settle within the underside of the inner storage volume. Subsequently, the flow of the exhaust gases is redirected by 180°, so that the outer storage volume is flowed through from top to bottom, resulting in cold and dust-free exhaust gases.During the discharge cycle, the fluid flow is reversed such that the outer storage volume is traversed from bottom to top, while the inner storage volume is traversed from top to bottom. This flow pattern during discharge allows cold ambient air to be converted into hot, dust-free process air. No dust deposited in the storage material is discharged during either the loading or unloading process.

[0016] 1. Method for guiding the flow of fluids for charging and discharging a thermal energy storage device, comprising a storage volume (2, 2') with a storage material (3), wherein the storage volume (2, 2') is divided into an inner storage volume (2) and an outer storage volume (2'), wherein the flow guidance is characterized in that, during charging, the inner storage volume (2) is flowed through by the fluid from bottom to top and, after a deflection of the flow (S) of the fluid, the outer storage volume (2') is subsequently flowed through from top to bottom, while during discharging, the outer storage volume (2') is flowed through by the fluid from bottom to top and, after a deflection of the flow (S) of the fluid, the inner storage volume (2) is subsequently flowed through from top to bottom.

[0017] Charging and discharging are based on heat transfer between the storage medium and the fluid, typically through convection. "Charging" means that the fluid transfers heat to the storage volume. "Discharging" means that the storage volume transfers heat to the fluid. The idea is that heat in a fluid (e.g., hot exhaust gas) is transferred to the storage volume to store this form of energy. The fluid cools down in the process. When energy is needed, cool fluid flows through the storage volume to transfer heat to the fluid. The heated fluid can then be used for energy production. For example, the fluid can be used to generate steam to power a steam engine. The heat stored in the fluid can also be used in other ways.During charging, the energy-rich fluid is introduced into the thermal energy storage device from outside and discharged from it in a lower energy state. Conversely, during discharging, the energy-poor fluid is introduced into the thermal energy storage device from outside and discharged from it in a higher energy state. The method is particularly suitable when the fluids used for charging comprise exhaust gases, preferably dust-laden exhaust gases. It can be provided that, during charging, dust settles within the lower region of the internal storage volume. This dust can be easily removed by tapping the storage material. The dust then falls to the bottom and can be disposed of.

[0018] Preferably, the fluids used for discharging include ambient air. This represents a simple and cost-effective way to discharge the energy storage device.

[0019] The storage material preferably consists of steel slag and / or other bulk materials. This material is a cost-effective storage medium with a high heat capacity. Furthermore, this material is particularly compatible with exhaust gases.

[0020] Preferably, the outer storage volume is divided concentrically to the inner storage volume. This facilitates flow guidance.

[0021] Furthermore, the outer storage volume can act as an additional layer of thermal insulation. This increases the storage efficiency.

[0022] The storage material is preferably arranged in the inner and outer storage volumes such that a thermocline forms in the outer storage volume. Surprisingly, it has been found that the storage process can be optimized if the thermocline is located in the outer storage volume rather than the inner one. The process should therefore be designed so that the thermocline forms in the outer storage volume. This can be achieved by appropriately dimensioning the storage volume and storage material in relation to the amount of heat supplied.

[0023] The invention further relates to a thermal energy storage device comprising a housing with a cylindrical section and a storage volume, wherein the storage volume includes external inlets and outlets as well as a storage material located within the storage volume. Furthermore, the storage volume is divided into an outer and an inner storage volume. The device is characterized in that the inlets and outlets are divided into at least one, preferably two to four, fluid inlets and fluid outlets, as well as at least one dust outlet. In addition, the inner storage volume is fluidly connected to the outer storage volume.

[0024] The cylindrical section is preferably in the form of a right circular cylinder.

[0025] The storage volume can be divided by a partition wall that extends only over part of the height of the housing. Preferably, the partition wall is only present in the cylindrical section. Furthermore, the partition wall is preferably insulating.

[0026] Dividing the storage volume into an inner and outer part minimizes heat loss to the environment, as the outer part of the storage material acts as an additional thermal insulation layer. This is because the radial heat losses from the hot storage material located in the inner part of the storage volume are preferentially transferred to the cooler storage material located in the outer part.

[0027] The storage material can include steel slag, which is also a byproduct of steel production, and / or other bulk materials such as stones, metal spheres, or ceramic spheres. This allows the storage material to be adapted to the process control, thereby optimizing the process control.

[0028] In one embodiment, the inlets and outlets are arranged on the base of the cylindrical housing, with at least one, preferably two, fluid inlets and outlets arranged diametrically opposite each other, while a further fluid inlet and outlet are located in the center of the housing's base. Furthermore, at least two dust outlets can be arranged between the central fluid inlet and outlet and the diametrically opposite fluid inlets and outlets.

[0029] The housing may include a deflector plate. In one embodiment, this potential deflector plate is arranged in the upper inner region of the housing and is shaped to allow the redirection of flows. A dust guard may be arranged below the storage volume, directing dust towards the dust outlet(s) and thus still allowing the inflow and outflow of fluids. In one embodiment, the dust guard is positioned at a certain distance from a centrally located fluid inlet and outlet.

[0030] In one embodiment, at least one fluid inlet and fluid outlet are arranged on the top surface of the housing. The fluid inlet and fluid outlet lead into a preferably cylindrical conduit element, which is longer than the height of the storage volume, so that the conduit element projects beyond the storage volume and thus enables the inner storage volume to be filled from bottom to top.

[0031] The housing can be shaped like a frustum cone in its upper region to facilitate the deflection of airflow. In this case, the base of the frustum is positioned closer to the storage volume than the top surface of the frustum.

[0032] Inside the housing, a grid can be arranged in the lower area, upon which the storage material rests.

[0033] In one embodiment, the portion of the storage material located in the outer storage volume rests on a grid, while the portion located in the inner storage volume rests on a sluice gate or a rotary floor. The sluice gate can be located in the dust outlet and may be configured, for example, as a rotary valve or a rotary tap. In contrast, the rotary floor can be located between ductwork and the dust outlet and may consist of individual rotary beams, preferably diamond-shaped.

[0034] The cylindrical housing can be tapered below the storage volume so that dust can be directed to a dust drain located in the center of the base of the housing, thereby allowing the dust to be discharged from the thermal energy storage device.

[0035] The housing can also include a knocking mechanism that facilitates the cleaning of dust deposited in the internal storage volume. This allows for dust removal during operation without replacing the storage material.

[0036] The housing can have an inlet on its top surface for filling with storage material. Additionally, an outlet can be provided on the base of the housing for the discharge of both dust and the storage material. To facilitate the replacement of the storage material—preferably only the inner, dust-laden material—it can rest on a sluice gate or a rotating platform. By opening the sluice gate or rotating the individual rotating platforms, the internal storage volume can be continuously or cyclically renewed.

[0037] By dimensioning the housing, considering the properties of the storage material, and optimizing the behavior of the upstream process, the thermocline can be arranged so that, during operation of the thermal energy storage device, it is preferentially located in the outer storage volume. By positioning the thermocline in the outer storage volume and by implementing the flow guidance described above, the thermocline can be kept in a more thermally optimal position. In this position, the upper region of the thermocline is hotter than the lower region. This further improves the thermal efficiency of the thermal energy storage system.

[0038] DETAILED DESCRIPTION OF THE INVENTION

[0039] Further advantages and details of the invention are explained below with reference to the following figures and examples, without these being to be understood as limiting.

[0040] Fig. 1a, 1b show a sectional view of a thermal energy storage device according to the invention with fluid inlet and fluid outlet on the top surface of the housing.

[0041] Fig. 2 shows a sectional view of an embodiment of a thermal energy storage device according to the invention with fluid inlet and fluid outlet on the base of the housing.

[0042] Figs. 1a and 1b each show a sectional view of a thermal energy storage device according to the invention, featuring different mechanisms for loading and unloading the storage material. Both Figs. 1a and 1b show the thermal energy storage device, which comprises a housing 1 with a cylindrical section and a storage volume 2, 2', the storage volume 2, 2' having external inlets and outlets. Furthermore, the storage volume 2, 2' contains a storage material 3 and is divided by a partition 4 into an inner storage volume 2 and an outer storage volume 2'. The partition 4 is located (only) in the cylindrical section. The storage material 3 in the outer storage volume 2' rests on a grid 8, while the storage material 3 in the inner storage volume 2 rests on a sluice gate 12 in Fig. 1a and on a rotating beam floor 13 in Fig. 1b.The used lock 12 should be suitable for bulk materials and is located in the dust outlet 6.

[0043] In Fig. 1b, the rotating beam base 13 is arranged below the duct element 11 and above the dust drain 6. The individual rotating beams of the rotating beam base 13 are diamond-shaped.

[0044] Furthermore, in the embodiments shown in Figs. 1a and 1b, the fluid inlets and fluid outlets 5, 5' are arranged on the top and side surfaces of the housing 1. Additionally, a dust outlet 6 is located in the center of the base of the housing 1, and a storage material inlet 10 is located in the center of the top surface of the housing 1. Moreover, the housing 1 tapers above the cylindrical section towards the top surface on one side and towards the base surface on the other, with the taper beginning only at the storage volume 2, 2'.

[0045] The fluid inlets and fluid outlets 5' are arranged opposite each other on the outer surface of the housing 1 and serve to charge or discharge the thermal energy storage device with cold air. The fluid inlets and fluid outlets 5 also serve to charge or discharge the thermal energy storage device with dust-laden or hot air.

[0046] The storage material inlet 10 is preferably for introducing storage material 3 into the inner storage volume 2, and the dust outlet 6 allows not only the discharge of dust but also the discharge of dust-laden storage material 3. For example, a dust-laden exhaust gas is directed into the thermal energy storage device via one of the fluid inlets and fluid outlets 5 and the duct element 11, which is longer than the height of the storage material 3. From there, the dust-laden exhaust gas flows through the inner storage volume 2 from bottom to top, whereby dust and tars are deposited in the storage material 3 during this process. Subsequently, the exhaust gas flow S enters a void 7. The void 7 connects the inner storage volume 2 with the outer storage volume 2' and redirects the flow S.By redirecting the flow S, the exhaust gas now flows through the outer storage volume 2' from top to bottom and can subsequently flow out via the fluid inlets and fluid outlets 5'.

[0047] In the embodiment shown in Fig. 2, a sectional view of a thermal energy storage device with external inlets and outlets is depicted, wherein the inlets and outlets are arranged on the base of the cylindrical housing 1. The inlets and outlets are divided into fluid inlets and fluid outlets 5, 5' and dust outlets 6. The outer fluid inlets and fluid outlets 5' are arranged diametrically opposite each other, while the inner fluid inlet and fluid outlet 5 are located in the center of the base of the housing 1. Furthermore, the dust outlets 6 are arranged between the central fluid inlet and fluid outlet 5 and the outer fluid inlets and fluid outlets 5'.Furthermore, the fluid inlets and fluid outlets 5' serve to load with cold ambient air and discharge cold and clean exhaust gas, while the fluid inlet and fluid outlet 5 serve to load with hot and dust-laden exhaust gas and discharge with hot and clean process air.

[0048] The device shown in Fig. 2 also comprises a concentrically divided storage volume 2, 2' with a storage material 3 that rests on a grid 8. Therefore, a flow configuration according to the inventive method is possible. Additionally, the thermal energy storage device has an internal dust guard 9, which is arranged between the grid 8 and the base of the housing 1. The dust guard 9 is conical or pyramidal in shape to allow the inflow and outflow of fluids and to direct dust towards the dust outlets.

Claims

REQUIREMENTS 1. Method for guiding the flow of fluids for charging and discharging a thermal energy storage device, comprising a storage volume (2, 2') with a storage material (3), wherein the storage volume (2, 2') is divided into an inner storage volume (2) and an outer storage volume (2'), wherein the flow guidance is characterized in that, during charging, the inner storage volume (2) is flowed through by the fluid from bottom to top and, after a deflection of the flow (S) of the fluid, the outer storage volume (2') is subsequently flowed through from top to bottom, while during discharging, the outer storage volume (2') is flowed through by the fluid from bottom to top and, after a deflection of the flow (S) of the fluid, the inner storage volume (2) is subsequently flowed through from top to bottom.

2. Method according to claim 1, characterized in that the fluids used for loading comprise exhaust gases, preferably dust-laden exhaust gases.

3. Method according to claim 1 or 2, characterized in that during loading, dust settles within the lower region of the inner storage volume (2).

4. Method according to one of claims 1 to 3, characterized in that the fluids used for unloading comprise ambient air.

5. Method according to one of claims 1 to 4, characterized in that the storage material (3) comprises steel slag and / or other bulk material.

6. Method according to one of claims 1 to 5, characterized in that the outer storage volume (2') is divided concentrically to the inner storage volume (2).

7. Method according to one of claims 1 to 6, characterized in that the outer storage volume (2') acts as an additional thermal insulation layer.

8. Method according to one of claims 6 or 7, characterized in that the storage material (3) is arranged in the inner storage volume (2) and in the outer storage volume (2') such that a thermocline is formed in the outer storage volume (2').

9. Thermal energy storage device comprising a housing (1) with a cylindrical section and a storage volume (2, 2'), wherein the storage volume (2, 2') has external inlets and outlets and a storage material (3) located in the storage volume (2, 2'), wherein the storage volume (2, 2') is divided into an inner storage volume (2) and an outer storage volume (2'), characterized in that the inlets and outlets are divided into at least one fluid inlet and one fluid outlet (5, 5'), preferably into two to four, fluid inlets and fluid outlets (5, 5'), and at least one dust outlet (6), and that the inner storage volume (2) is fluidly connected to the outer storage volume (2').

10. Thermal energy storage device according to claim 9, characterized in that the storage volume (2, 2') is separated by a partition (4) which extends only over a part of the height of the housing (1), preferably in the cylindrical section.

11. Thermal energy storage device according to claim 9 or 10, characterized in that a dust guard (9) is provided.

12. Thermal energy storage device according to one of claims 9 to 11, characterized in that the storage material (3) is arranged in the housing (1) such that, in the operating state, the thermocline is preferably arranged in the outer storage volume (2').

13. Thermal energy storage device according to one of claims 9 to 12, characterized in that the thermocline is held in a position from a thermal point of view in which the thermocline is hotter in the upper region than in the lower region.

14. Thermal energy storage device according to one of claims 9 to 13, characterized in that the storage material (3), preferably the storage material (3) of the inner storage volume (2), is replaceable.

15. Thermal energy storage device according to one of claims 9 to 14, characterized in that the energy storage device comprises a knocking mechanism.

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