Device and method for concentrating solar fluidized catalytic production of magnesium hydride

Abstract

The application relates to the technical field of magnesium-based solid-state hydrogen storage material preparation, and discloses a device and a method for preparing magnesium hydride through concentrated solar energy fluidized catalysis. The device comprises a solar heat supply unit, a reaction unit and a separation unit, and specifically comprises a heliostat field, a concentrated receiver, a heat exchange / heat storage unit, a fluidized reactor, a separation and circulation unit and a hydrogen supply and pressure control unit. Solar heat is transmitted into the fluidized reactor through the heat exchange / heat storage unit, hydrogen is uniformly introduced from the bottom through a gas distribution plate, magnesium powder is fluidized and fully contacts with fixed catalyst structures, and the gas-solid hydrogenation reaction is promoted to generate magnesium hydride. The solar heat supply unit is integrally coupled with the fluidized reactor which has the functions of bottom hydrogen fluidization, heat exchange through heat exchange pipes, fixed catalyst structures and a maintainable design, the gas-solid contact and heat and mass transfer efficiency are improved, the external heating energy consumption is reduced, and the hydrogen utilization rate is improved.

Description

Technical Field

[0001] This invention relates to the field of solar thermochemical utilization and magnesium-based solid hydrogen storage material preparation technology, specifically to an apparatus and method for preparing magnesium hydride using concentrated solar fluidized catalysis. Background Technology

[0002] Magnesium hydride possesses a high theoretical hydrogen storage density, and its raw materials are widely available and relatively inexpensive, making it an important representative of magnesium-based solid-state hydrogen storage materials. However, traditional magnesium hydride preparation processes typically rely on external electric heating or furnace heating, resulting in problems such as high energy consumption, uneven temperature distribution, and limited reaction efficiency. Furthermore, the gas-solid reaction between magnesium powder and hydrogen requires stringent conditions for heat transfer, mass transfer, and interfacial contact. Uneven gas distribution within the reactor or insufficient particle flowability can lead to slow hydrogenation processes, and even localized agglomeration and incomplete reactions.

[0003] In existing technologies, the preparation of magnesium hydride from magnesium powder typically employs conventional heating devices such as tubular furnaces, fixed-bed reactors, or intermittent pressure reactors. These devices mostly rely on electric heating or external furnace heating, with heat transferred from the outer wall of the reactor to the interior. This often results in long heating times, uneven temperature distribution, and significant heat loss. Furthermore, insufficient contact between magnesium powder and hydrogen gas under static or weakly disturbed conditions can lead to localized dead zones, particle agglomeration, and incomplete reactions due to uneven gas distribution. In addition, existing devices typically use direct mixing of catalyst and magnesium powder, making online catalyst replacement or long-term stable utilization difficult, which is detrimental to continuous or semi-continuous operation. Insufficient recovery of unreacted hydrogen and entrained particles from the tail gas also affects feedstock utilization and stable operation. In summary, existing devices still suffer from high heating energy consumption, insufficient gas-solid contact, difficulty in long-term stable utilization of the catalytic interface, and inadequate tail gas recovery. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides an apparatus and method for the preparation of magnesium hydride using concentrated solar fluidized bed catalysis. This invention integrates a solar heating unit, consisting of a heliostat, a concentrator receiver, and a heat exchange / storage unit, with a fluidized bed reactor featuring bottom hydrogen inlet fluidization, heat exchange tubes, a fixed catalyst structure, and a maintainable design. The heliostat and concentrator receiver provide solar heat, the heat exchange / storage unit supplies heat to the fluidized reaction zone, the heat exchange tubes improve temperature field uniformity, a gas distribution plate causes the bottom-entering hydrogen to rise uniformly and agitate magnesium powder, forming a fluidized state, and a replaceable fixed catalyst structure ensures continuous contact between the magnesium powder and the catalytic interface during fluidization. A gas-solid separator and a separation and circulation unit recover entrained particles and recycle unreacted hydrogen, thereby solving the problems of high heating energy consumption, insufficient gas-solid contact, difficulty in long-term stable utilization of the catalytic interface, and inadequate tail gas recovery in traditional devices.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: The purpose of this invention is to provide an apparatus for the preparation of magnesium hydride using concentrated solar fluidized bed catalysis, comprising: The solar heating unit includes a heliostat field for reflecting solar radiation; a concentrator for receiving solar radiation reflected by the heliostat field and converting it into solar heat; and a heat exchange / storage unit for receiving and storing solar heat generated by the concentrator.

[0006] The reaction unit includes a fluidized bed reactor, which contains a fluidized reaction zone for placing magnesium powder. Below the fluidized reaction zone is a gas distribution plate for dispersing hydrogen gas and feeding it into the fluidized reaction zone, causing the hydrogen gas to blow up the magnesium powder and form a fluidized state. Under the action of a catalyst, the magnesium powder reacts with hydrogen gas to produce magnesium hydride. The fluidized reaction zone contains a detachable fixed catalyst structure for loading the catalyst, located within the fluidized reaction zone. Heat exchange tubes are located on the side or periphery of the fixed catalyst structure, and the heat exchange tubes are connected to a heat exchange / storage unit for exchanging solar heat to drive the reaction between magnesium powder and hydrogen gas.

[0007] The separation unit includes a gas-solid separator and a separation and circulation unit. The gas-solid separator is installed on the fluidized reactor and is used to separate unreacted hydrogen carrying magnesium powder and magnesium hydride particles during the reaction. The separation and circulation unit is connected to the gas-solid separator and is used to recover the hydrogen after gas-solid separation and transport it to the gas distribution plate for recycling.

[0008] In a preferred embodiment of the present invention, the fixed catalyst structure is located at the center of the fluidized reaction zone, and the fixed catalyst structure is a porous disk-shaped, mesh-shaped, or bar-shaped structure.

[0009] In a preferred embodiment of the present invention, the pore size of the porous disk structure is 0.5 mm to 5 mm, the mesh size of the grid structure is 1 mm to 10 mm, the diameter of the bar structure is 2 mm to 20 mm, and the porosity of the fixed catalyst structure is 30% to 80%.

[0010] In a preferred embodiment of the present invention, the temperature of the heat exchange medium output by the heat exchange / storage unit is 300℃~450℃.

[0011] In a preferred embodiment of the present invention, the gas distribution plate is connected to a gas supply unit, and the gas supply unit is further provided with a hydrogen supply and pressure control unit for supplying hydrogen to the fluidized reaction zone and regulating the hydrogen supply pressure and flow rate.

[0012] In a preferred embodiment of the present invention, the fluidized reactor is provided with a magnesium powder inlet for conveying magnesium powder to the fluidized reaction zone; the bottom of the fluidized reactor is provided with a MgH2 product outlet for collecting MgH2 product.

[0013] In a preferred embodiment of the present invention, the fluidized reactor is provided with a reactor shell, the reactor shell is provided with a catalyst replacement door, and the outer wall of the reactor shell is provided with a heat insulation layer.

[0014] Another object of the present invention is to provide a method for preparing magnesium hydride using the above-described apparatus, comprising the following steps: S1. The solar light is focused onto the concentrator through the heliostat field to obtain solar heat and transfer it to the heat exchange / storage unit.

[0015] S2. Add magnesium powder to the fluidized reaction zone, and transport the heat exchange medium to the heat exchange tube through the heat exchange / heat storage unit to heat the fluidized reaction zone to 300℃~400℃. Then, disperse hydrogen through the gas distribution plate and input it into the fluidized reaction zone to make the magnesium powder fluidized. Under the catalytic action of the catalyst in the fixed catalyst structure, the magnesium powder and hydrogen undergo a gas-solid hydrogenation reaction to generate magnesium hydride.

[0016] S3. During the reaction, unreacted hydrogen gas carrying magnesium powder and magnesium hydride particles is separated by a gas-solid separator. The unreacted hydrogen gas after gas-solid separation is recovered by the separation and circulation unit and transported to the gas distribution plate for recycling.

[0017] In a preferred embodiment of the present invention, the standard state flow rate of hydrogen is 2 L / min to 20 L / min, and the absolute reaction pressure is 0.5 MPa to 2.0 MPa.

[0018] In a preferred embodiment of the present invention, the magnesium powder particle size is 45μm to 75μm.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides an apparatus for the preparation of magnesium hydride using concentrated solar fluidized bed catalysis. It integrates a solar heating unit consisting of a heliostat field, a concentrator receiver, and a heat exchange / storage unit with a fluidized bed reactor featuring bottom hydrogen inlet fluidization, heat exchange tubes, a fixed catalyst structure, and a maintainable design. This invention utilizes heliostat-concentrated solar energy as a high-temperature heat source, replacing part of the traditional electric heating or furnace heating process, thus reducing the external energy consumption for magnesium hydride preparation. The fluidized bed reactor is equipped with a gas distribution plate, allowing the bottom-entering hydrogen gas to rise uniformly and agitate the magnesium powder, significantly enhancing gas-solid mass transfer and reaction uniformity, and reducing local dead zones and agglomeration. The fixed catalyst structure within the fluidized reaction zone ensures continuous contact between the magnesium powder and the catalytic interface in the fluidized state. Heat exchange tubes on the sides or periphery of the fixed catalyst structure improve temperature field uniformity. The gas-solid separator and separation and circulation unit in the separation unit are used to recover entrained solid particles and unreacted hydrogen, improving raw material utilization and operational stability. This addresses the problems of high heating energy consumption, insufficient gas-solid contact, difficulty in long-term stable utilization of the catalytic interface, and inadequate recovery and utilization of exhaust gas in traditional devices.

[0020] 2. The fixed catalyst structure set inside the fluidized reactor in this invention can be used for a long time and can be easily maintained through the catalyst replacement door, thereby improving the stability and practicality of the device operation.

[0021] 3. The present invention provides heat exchange tubes and insulation layers in the fluidized reactor, which helps to improve the uniformity of the temperature field and reduce heat loss. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the concentrated solar fluidized catalytic magnesium hydride preparation device of the present invention. The diagram illustrates: 1. Heliostat field; 2. Concentrating receiver; 3. Heat exchange / storage unit; 4. Separation and circulation unit; 5. Magnesium powder inlet; 6. Fixed catalyst structure; 7. MgH2 product outlet; 8. Gas supply unit; 9. Hydrogen supply and pressure control unit; 10. Fluidized reaction zone; 11. Gas distribution plate; 12. Heat exchange tube; 13. Gas-solid separator; 14. Reactor shell; 15. Insulation layer; 16. Catalyst replacement door.

[0023] Figure 2 The XRD pattern of MgH2 synthesized in this invention is shown.

[0024] Figure 3 This is the SEM image of the MgH2 synthesized in this invention. Figure 3 Image A is a morphological image at 500x magnification, and image B is a morphological image at 2000x magnification.

[0025] Figure 4 This is a graph showing the hydrogen absorption kinetics of the MgH2 synthesized in this invention.

[0026] Figure 5 This is a graph showing the hydrogen desorption kinetics of the MgH2 synthesized in this invention. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0029] In existing technologies, the preparation of magnesium hydride from magnesium powder typically employs conventional heating devices such as tubular furnaces, fixed-bed reactors, or intermittent pressure reactors. These devices mostly rely on electric heating or external furnace heating, with heat transferred from the outer wall of the reactor to the interior. This often results in long heating times, uneven temperature distribution, and significant heat loss. Furthermore, insufficient contact between magnesium powder and hydrogen gas under static or weakly disturbed conditions can lead to localized dead zones, particle agglomeration, and incomplete reactions due to uneven gas distribution. In addition, existing devices often use direct mixing of catalyst and magnesium powder, making catalyst replacement difficult or hindering long-term stable utilization, which is unfavorable for continuous or semi-continuous operation. Insufficient recovery of unreacted hydrogen and entrained particles from the tail gas also affects raw material utilization and stable operation. Therefore, there is a need to develop a magnesium hydride preparation device that can simultaneously improve heating methods, gas-solid contact, catalytic interface stability, and tail gas recovery.

[0030] Based on this, on the one hand, the present invention provides an apparatus for the preparation of magnesium hydride by concentrated solar fluidized catalysis, such as... Figure 1 As shown, it includes a solar heating unit, a reaction unit, and a separation unit. Specifically, it includes a heliostat field 1, a concentrating receiver 2, a heat exchange / storage unit 3, a separation and circulation unit 4, a hydrogen supply and pressure control unit 9, and a fluidized bed reactor.

[0031] The solar heating unit includes a heliostat field 1, a concentrator receiver 2, and a heat exchange / storage unit 3. The heliostat field 1 reflects solar radiation to the concentrator receiver 2. The solar heat generated by the concentrator receiver 2 is transferred to the fluidized reactor through the heat exchange / storage unit 3 to provide process heat for the magnesium powder hydrogenation reaction.

[0032] The reaction unit includes a fluidized bed reactor, which comprises a reactor shell 14, an insulation layer 15, a fluidized reaction zone 10, a gas distribution plate 11, a heat exchange tube 12, a fixed catalyst structure 6, a catalyst replacement door 16, a gas supply unit 8, a magnesium powder inlet 5, and a MgH2 product outlet 7. The fluidized reaction zone 10 is located inside the reactor shell 14. The gas distribution plate 11 is positioned below the fluidized reaction zone 10 and communicates with the gas supply unit 8. The fixed catalyst structure 6 is located near the central axis of the fluidized reaction zone 10, with its lower edge positioned above the gas distribution plate 11. The heat exchange tube 12 is positioned around or adjacent to the fixed catalyst structure 6, maintaining a distance from it. The magnesium powder inlet 5 is located above or to the side of the fluidized bed reactor, and the MgH2 product outlet 7 is located at the bottom of the fluidized bed reactor.

[0033] The fixed catalyst structure 6 is disposed inside the reactor, located at the center of the fluidized reaction zone 10. It can be a porous disc, mesh, or bar structure, used to provide a stable catalytic interface during long-term operation and to ensure sufficient contact with rising hydrogen and fluidized magnesium powder. The fixed catalyst structure 6 contains a catalyst, the catalytically active component of which can be at least one metal, oxide, alloy, or combination of metal and metal oxide selected from nickel, titanium, niobium, cerium, iron, and cobalt, capable of promoting the hydrogenation reaction between magnesium powder and hydrogen. The active component can be loaded or fixed on a heat-resistant metal mesh, porous ceramic, or stainless steel support. The pore size of the porous disc structure can be 0.5 mm to 5 mm, the mesh size of the mesh structure can be 1 mm to 10 mm, and the diameter of the bar structure can be 2 mm to 20 mm, with an overall porosity of 30% to 80%. The material of the fixed catalyst structure 6 can be adjusted according to actual operating conditions.

[0034] The gas supply unit 8 is located at the bottom of the reactor and connected to the gas distribution plate 11. Hydrogen gas enters the fluidized reaction zone 10 evenly through the gas distribution plate 11 to agitate the magnesium powder, thereby enhancing the contact reaction between the magnesium powder and hydrogen. The bottom hydrogen inlet combined with the structural design of the gas distribution plate 11 ensures that hydrogen gas not only enters the system as a reactant but also plays a role in agitating the magnesium powder, enhancing fluidization and mass transfer, which is beneficial to improving the contact efficiency between magnesium powder and hydrogen gas and making the reaction more complete. The gas supply unit 8 is also equipped with a hydrogen supply and pressure control unit 9, which is used to supply hydrogen gas to the fluidized reaction zone and regulate the hydrogen supply pressure and flow rate. The gas supply unit 8 is a hydrogen cylinder.

[0035] The aperture and porosity of the gas distribution plate 11 can be adjusted according to the magnesium powder particle size and hydrogen flow rate to achieve uniform hydrogen distribution and prevent magnesium powder leakage.

[0036] The catalyst replacement door 16 is located on the side wall of the reactor and is used for inspecting, replacing or maintaining the fixed catalyst structure.

[0037] The separation unit includes a gas-solid separator 13 and a separation and circulation unit 4. The gas-solid separator 13 is connected to the fluidized reactor through the tail gas outlet at the top or upper part of the fluidized reactor. The separation and circulation unit 4 is connected to the gas-solid separator 13 and is used to separate magnesium powder particles entrained in the tail gas and recover unreacted hydrogen.

[0038] The heat exchange / storage unit 3 is connected to or heat-exchange-connected to the heat exchange tube 12 to provide heat to the fluidized reaction zone 10. The heat exchange / storage unit 3 can be a molten salt heat exchange unit or a high-temperature thermal oil heat exchange unit. The heat exchange medium is transported to the heat exchange tube 12 by a circulating pump, and a closed-loop temperature control system is formed by a temperature sensor, temperature controller, and regulating valve. When molten salt is used as the heat exchange medium, the molten salt pipeline, valves, and pump body are equipped with heat tracing and insulation structures to maintain the molten salt temperature above its solidification temperature during start-up and shutdown. The temperature of the heat exchange medium output by the heat exchange / storage unit 3 can be controlled between 300℃ and 450℃ to meet the heat required for the magnesium powder hydrogenation reaction and avoid local overheating. The material of the heat exchange tube 12 can be adjusted according to actual operating conditions.

[0039] The reactor shell 14 is provided with an insulation layer 15 on the outside. It is understood that the present invention is not limited to the thickness of the insulation layer 15. Its thickness can be adjusted according to the actual insulation effect on the reactor. The material of the reactor shell 14 can be adjusted according to the actual reaction temperature and pressure requirements.

[0040] It should be noted that the heliostat field 1, the concentrating receiver 2, the separation and circulation unit 4, and the hydrogen supply and pressure control unit 9 in this invention can be commonly used equipment in the field. The improvement of this invention lies in the integrated coupling of the above-mentioned solar heating unit with a fluidized bed with bottom hydrogen inlet fluidization, heat exchange tube heat exchange, fixed catalyst structure, and maintainable design, thereby simultaneously solving the problems of high external heating energy consumption, insufficient contact between magnesium powder and hydrogen, difficulty in long-term stable use of catalyst, and low tail gas utilization rate in traditional devices.

[0041] In this invention, concentrated solar energy technology converts solar radiation into solar heat, providing a renewable heat source for the gas-solid hydrogenation reaction. A heliostat field concentrates sunlight onto a concentrator, which then supplies stable heat to the reactor via a heat exchange / storage unit. This technology is coupled with the magnesium powder hydrogenation process, and a fixed catalyst structure is installed inside the reactor. Simultaneously, a bottom hydrogen inlet and gas distribution plate create fluidization enhancement, which improves the contact efficiency and reaction rate between magnesium powder and hydrogen.

[0042] On the other hand, the present invention provides a method for preparing magnesium hydride using the above-mentioned concentrated solar fluidized catalytic oxidation apparatus, comprising the following steps: S1. The sunlight is focused onto the concentrator receiver 2 through the heliostat field 1. The concentrator receiver 2 converts the solar radiation into heat and heats and stores the heat exchange medium in the heat exchange / storage unit 3.

[0043] S2. Start the heat exchange medium circulation pump to transport the heat exchange medium in the heat exchange / storage unit 3 to the heat exchange tube 12. The heat exchange medium indirectly exchanges heat with the fluidized reaction zone 10 in the heat exchange tube 12. The temperature signal is collected by the temperature sensor installed in the fluidized reaction zone, and the circulation pump speed and bypass regulating valve opening are adjusted by the temperature controller to control the temperature of the fluidized reaction zone 10 at 300℃~400℃, which is the temperature for the reaction of magnesium powder and hydrogen.

[0044] S3. Magnesium powder is added to the fluidized reactor through magnesium powder inlet 5 and enters the fluidized reaction zone 10.

[0045] S4. Before introducing hydrogen, the fluidized reactor and tail gas circulation pipeline are first replaced with argon until the oxygen content in the outlet gas is less than 1 vol.%. Then, the hydrogen supply and pressure control unit 9 adjusts the hydrogen pressure and flow rate. The hydrogen enters the gas distribution plate 11 through the gas supply unit 8. After being evenly dispersed by the gas distribution plate 11, the hydrogen enters the fluidized reaction zone 10 from bottom to top, so that the magnesium powder is in a fluidized state.

[0046] S5. Fluidized magnesium powder comes into contact with a fixed catalyst structure 6 supported by a catalyst, and under the catalytic action of the catalyst, it undergoes a gas-solid hydrogenation reaction with hydrogen to generate magnesium hydride.

[0047] S6. During the reaction, unreacted hydrogen gas, carrying solid particles, namely magnesium powder or magnesium hydride particles, undergoes gas-solid separation in gas-solid separator 13. The separated hydrogen gas enters separation and circulation unit 4. After cooling, filtration, and buffering, the unreacted hydrogen gas is returned to the hydrogen supply pipeline by the circulation compressor. After the reaction is completed, hydrogen supply and heating are stopped. The hydrogen gas in the system is recovered first, and then argon gas is used to replace the fluidized reactor and tail gas pipeline. After the reactor is cooled and depressurized to atmospheric pressure, the generated magnesium hydride is discharged from MgH2 product outlet 7 into a sealed receiving tank pre-filled with argon gas.

[0048] The fixed catalyst structure 6 does not participate in the overall movement during the reaction, while the magnesium powder is fluidized around it and contacts the reaction.

[0049] The above method combines solar thermal heating, bottom hydrogen inlet fluidization, fixed catalysis, and tail gas recirculation to ensure continuous connection between heating, reaction, and recovery steps, facilitating scale-up operation and improving hydrogen utilization efficiency.

[0050] The following specific examples will provide further explanation.

[0051] Example 1 A method for preparing magnesium hydride using the above-mentioned concentrated solar fluidized catalytic converter includes the following steps: S1. The heliostat field 1 tracks the sun's movement and reflects solar radiation to the concentrator receiver 2, which absorbs and converts solar energy into solar heat. In this embodiment, the heat exchange / storage unit 3 adopts a dual-tank molten salt heat storage and exchange unit, including a hot molten salt tank, a cold molten salt tank, a molten salt circulation pump, a three-way regulating valve, and a temperature controller; the heat exchange medium is a mixed molten salt of sodium nitrate and potassium nitrate with a mass ratio of 60:40. The heated molten salt is stored in the hot molten salt tank, and the molten salt circulation pump transports the hot molten salt to the heat exchange tube 12 for indirect heat exchange with the fluidized reaction zone 10. The molten salt after heat exchange returns to the cold molten salt tank. The molten salt pipelines, valves, and pump bodies are all equipped with electric heat tracing and insulation layers to maintain the molten salt temperature above 250°C during start-up and shutdown to prevent the molten salt from solidifying. A K-type thermocouple is installed in the fluidized reaction zone 10. The temperature controller adopts PID control mode. Based on the thermocouple feedback signal, the speed of the molten salt circulation pump and the opening of the three-way regulating valve are adjusted to control the temperature of the fluidized reaction zone 10 at 375℃, and the temperature fluctuation is controlled within ±5℃.

[0052] S2. In this embodiment, the reactor shell 14 is made of 316L stainless steel, with an inner diameter of 80mm, an effective height of 500mm, a wall thickness of 8mm, and a design pressure of 2.5MPa. The gas distribution plate 11 adopts a double-layer structure. The lower layer is a 3mm thick 316L stainless steel perforated plate with a pore diameter of 0.7mm, a pore center distance of 3mm, and an opening rate of 4% to 5%. The upper layer is covered with a 316L sintered metal porous plate with a filtration accuracy of 20μm to prevent magnesium powder from leaking downwards into the gas supply unit 8. 50g of magnesium powder with a particle size of 45μm to 75μm is added to the fluidized reaction zone 10 through the magnesium powder inlet 5. Before introducing hydrogen, the reactor and tail gas circulation pipeline are first purged with argon until the outlet oxygen content is lower than 1 vol.%. After the hydrogen supply and pressure control unit 9 adjusts the hydrogen pressure and flow rate, hydrogen enters through the gas supply unit 8. The standard state hydrogen flow rate is controlled at 5L / min, and the absolute reaction pressure is controlled at 1.0MPa. Hydrogen gas is evenly distributed through the gas distribution plate 11 and flows from bottom to top, causing the magnesium powder particles to be in a fluidized state. The fixed catalyst structure 6 is arranged along the central axis of the fluidized reaction zone 10, with its lower edge 30 mm away from the gas distribution plate 11. The heat exchange tube 12 is made of 316L stainless steel with an outer diameter of 8 mm and a wall thickness of 1 mm, and is arranged in a spiral around the fixed catalyst structure 6 with a pitch of 25 mm. The minimum radial distance between the heat exchange tube 12 and the fixed catalyst structure 6 is 5 mm.

[0053] S3. Under the combined action of solar heat and the catalyst in the fixed catalyst structure 6, magnesium powder gradually absorbs hydrogen to generate magnesium hydride. The fixed catalyst structure 6 adopts a detachable double-layer 316L stainless steel mesh box with external dimensions of 30mm×30mm×12mm and internal effective cavity dimensions of 25mm×25mm×10mm. The outer supporting mesh has a mesh size of 5mm, and the inner layer uses a 316L sintered metal microporous mesh with a filtration precision of 5μm. The total amount of nickel powder and niobium pentoxide used is 10wt.% of the magnesium powder mass, i.e., 5g, with a nickel powder to niobium pentoxide mass ratio of 1:1, i.e., 2.5g nickel powder and 2.5g niobium pentoxide. After the nickel powder and niobium pentoxide are mixed evenly, they are uniformly filled into the internal effective cavity, with a catalyst layer thickness of 10mm and a filling density of 0.8g / cm³. 3 Subsequently, the catalyst powder is folded and pressed on all four sides and secured with stainless steel bolts to prevent it from falling off during fluidization, and the two do not require pre-formation of a chemical complex. Nickel powder and niobium pentoxide were purchased from Aladdin Reagent Co., Ltd. The tail gas generated during the reaction enters the gas-solid separator 13 via a top pipeline, and then enters the separation and circulation unit 4. In this embodiment, the gas-solid separator 13 adopts a combination structure of an expanded settling chamber and a sintered metal filter element with a filtration accuracy of 5μm and a pressure resistance of not less than 2.5MPa, used to separate magnesium powder or magnesium hydride particles entrained in the tail gas. The separation and circulation unit 4 works as follows: the filtered tail gas is cooled to below 50°C by a cooler and then enters a buffer tank, where it is pressurized by a hydrogen diaphragm compressor and returned to the hydrogen supply pipeline via a check valve and a mass flow controller, realizing the recycling of unreacted hydrogen.

[0054] S4. An insulation layer 15 is installed on the outside of the reactor shell 14. The insulation layer 15 is made of ceramic fiber blanket with a temperature resistance of over 1000℃ and a thickness of 50mm. A stainless steel protective shell with a thickness of 1mm is installed on the outside. The heat exchange tubes 12 are spirally arranged around the fixed catalyst structure 6, so that solar heat is evenly transferred to the fluidized reaction zone 10. After the reaction is completed, the supply of fresh hydrogen is stopped and the hydrogen in the system is recovered. Then, the reactor and tail gas circulation pipeline are purged with argon. After the heating is stopped, the molten salt in the heat exchange tubes 12 is discharged back to the cold molten salt tank, and then the molten salt circulation pump is turned off. The reactor is cooled to below 80℃ and slowly depressurized to atmospheric pressure through the tail gas pipeline. Then, the pressure-resistant discharge valve set at the MgH2 product outlet 7 is opened to discharge the generated magnesium hydride into a sealed receiving tank pre-filled with argon.

[0055] Example 2 Except for the shape and arrangement of the fixed catalyst structure 6, the catalyst type, total amount, mass ratio of nickel powder to niobium pentoxide, and other reaction conditions are the same as in Example 1.

[0056] The difference from Example 1 is that the fixed catalyst structure 6 adopts a porous disc-shaped module, which is arranged in three layers from top to bottom in the center of the fluidized reaction zone 10. The pore size is 2mm. The magnesium powder particles are in continuous contact with the surface of the porous disc-shaped module in the fluidized state, which is suitable for scenarios that require a large gas-solid contact area.

[0057] Example 3 Except for the shape and arrangement of the fixed catalyst structure 6, the catalyst type, total amount, mass ratio of nickel powder to niobium pentoxide, and other reaction conditions are the same as in Example 1.

[0058] The difference from Example 1 is that the fixed catalyst structure 6 adopts a grid-like module with a mesh size of 5mm, which can improve air permeability and reduce the risk of local blockage.

[0059] Example 4 Except for the shape and arrangement of the fixed catalyst structure 6, the catalyst type, total amount, mass ratio of nickel powder to niobium pentoxide, and other reaction conditions are the same as in Example 1.

[0060] The difference from Example 1 is that the fixed catalyst structure 6 adopts a bar-type module with a bar diameter of 10mm, which is convenient for manufacturing, installation and disassembly, and is suitable for long-term operation.

[0061] Comparative Example 1 The difference from Example 1 is that: no fixed catalyst structure 6 is set, and the reactor is heated by conventional external electric heating. The magnesium powder addition amount, hydrogen flow rate, reaction pressure and reaction temperature are the same as those in Example 1.

[0062] Comparative Example 1 did not have a fixed catalyst structure and used a conventional external electric heating method. Therefore, it did not have the fixed catalyst interface and the coupling structure of solar heat supplying heat to the fluidized reaction zone through heat exchange tubes as in Example 1.

[0063] The hydrogen absorption and desorption properties of MgH2 obtained in Example 1 are shown in [reference needed]. Figure 4 and Figure 5 The results showed that it had both hydrogen absorption and desorption responses at different temperatures, indicating that under the above reaction conditions, magnesium powder can be hydrogenated in the fluidized reactor to obtain MgH2 products with hydrogen absorption and desorption responses, thus providing performance support for the feasibility of the aforementioned device structure.

[0064] Since Examples 1 to 4 all belong to different forms of fixed catalyst structures, their preparation processes and reaction principles are similar. Therefore, we will take the MgH2 prepared in Example 1 as an example for further explanation, and the results are analyzed as follows.

[0065] Figure 2 This is the XRD pattern of the MgH2 synthesized in this invention. Figure 2It can be seen that the main diffraction peaks of the sample correspond to the characteristic peaks of MgH2, indicating that magnesium powder can form magnesium hydride phase after being processed by this device, and no obvious impurity phase peaks are observed, indicating that the sample is mainly composed of MgH2 phase.

[0066] Figure 3 This is the SEM image of the MgH2 synthesized in this invention. Figure 3 Image A is a 500x magnification topographic view, and image B is a 2000x magnification topographic view. Figure 3 It can be seen that the product particles have a mixed morphology of irregular blocks and fine particles, and the particles have a certain degree of dispersion, indicating that the bottom hydrogen inlet fluidization process is beneficial to reduce local agglomeration and increase the gas-solid contact area.

[0067] Figure 4 This is a hydrogen absorption kinetic curve of the MgH2 synthesized in this invention. (From...) Figure 4 It can be seen that at 325℃, 350℃ and 375℃, the hydrogen absorption of the sample gradually increases with time; after the temperature increases, the hydrogen absorption rate and the final hydrogen absorption both increase significantly. Among them, the hydrogen absorption at 375℃ for 60 min is about 5.3 wt.%, indicating that increasing the reaction temperature is beneficial to promoting the hydrogenation process of magnesium powder.

[0068] Figure 5 This is a hydrogen desorption kinetic curve of the MgH2 synthesized in this invention. (From...) Figure 5 It can be seen that the sample can release hydrogen at 325℃, 350℃ and 375℃, and the higher the temperature, the faster the hydrogen release rate and the greater the amount of hydrogen released; the absolute value of the amount of hydrogen released in 60 minutes at 375℃ is about 3.8 wt.%, indicating that the obtained MgH2 has a certain reversible hydrogen absorption and release performance.

[0069] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended scope of protection is intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0070] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. An apparatus for the preparation of magnesium hydride using concentrated solar fluidized bed catalysis, characterized in that, include: The solar heating unit includes a heliostat field (1) for reflecting solar radiation; a concentrator (2) for receiving solar radiation reflected by the heliostat field (1) and converting it into solar heat; and a heat exchange / storage unit (3) for receiving solar heat generated by the concentrator (2) and storing energy. The reaction unit includes a fluidized reactor, which has a fluidized reaction zone (10) for placing magnesium powder. A gas distribution plate (11) is provided below the fluidized reaction zone (10) to disperse hydrogen and send it into the fluidized reaction zone (10), so that the hydrogen blows up the magnesium powder to form a fluidized state. Under the action of the catalyst, the magnesium powder reacts with the hydrogen to generate magnesium hydride. A detachable fixed catalyst structure (6) for loading the catalyst is provided in the fluidized reaction zone (10). A heat exchange tube (12) is provided on the side or around the fixed catalyst structure (6). The heat exchange tube (12) is connected to the heat exchange / storage unit (3) to exchange solar heat and drive the magnesium powder to react with hydrogen. The separation unit includes a gas-solid separator (13) and a separation and circulation unit (4). The gas-solid separator (13) is installed on the fluidized reactor and is used to separate unreacted hydrogen gas carrying magnesium powder and magnesium hydride particles during the reaction process. The separation and circulation unit (4) is connected to the gas-solid separator (13) and is used to recover the hydrogen gas after gas-solid separation and transport it to the gas distribution plate (11) for recycling.

2. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 1, characterized in that, The fixed catalyst structure (6) is located at the center of the fluidized reaction zone (10), and the fixed catalyst structure (6) is a porous disk-shaped, mesh-shaped, or bar-shaped structure.

3. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 2, characterized in that, The porous disc structure has a pore size of 0.5 mm to 5 mm, the mesh structure has a mesh size of 1 mm to 10 mm, the bar structure has a diameter of 2 mm to 20 mm, and the fixed catalyst structure (6) has a porosity of 30% to 80%.

4. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 1, characterized in that, The output temperature of the heat exchange medium of the heat exchange / storage unit (3) is 300℃~450℃.

5. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 1, characterized in that, The gas distribution plate (11) is connected to the gas supply unit (8), and the gas supply unit (8) is also equipped with a hydrogen supply and pressure control unit (9) for supplying hydrogen to the fluidized reaction zone (10) and regulating the supply pressure and flow rate of hydrogen.

6. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 1, characterized in that, The fluidized reactor is equipped with a magnesium powder inlet (5) for conveying magnesium powder to the fluidized reaction zone (10); the bottom of the fluidized reactor is equipped with a MgH2 product outlet (7) for collecting MgH2 product.

7. The apparatus for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 1, characterized in that, The fluidized reactor is provided with a reactor shell (14), a catalyst replacement door (16) is provided on the reactor shell (14), and an insulation layer (15) is provided on the outer wall of the reactor shell (14).

8. A method for preparing magnesium hydride using concentrated solar fluidized bed catalysis, characterized in that, Performed using the apparatus according to any one of claims 1 to 7, comprising the following steps: The solar light is focused onto the concentrator (2) through the heliostat field (1) to obtain solar heat and transfer it to the heat exchange / storage unit (3). Magnesium powder is added to the fluidized reaction zone (10), and the heat exchange medium is transported to the heat exchange tube (12) through the heat exchange / heat storage unit (3) to heat the fluidized reaction zone (10) to 300℃~400℃. Then, hydrogen is dispersed and input into the fluidized reaction zone (10) through the gas distribution plate (11) so that the magnesium powder forms a fluidized state. Under the catalytic action of the catalyst in the fixed catalyst structure (6), the magnesium powder and hydrogen undergo a gas-solid hydrogenation reaction to generate magnesium hydride. During the reaction, unreacted hydrogen gas carrying magnesium powder and magnesium hydride particles is separated by a gas-solid separator (13). The unreacted hydrogen gas after gas-solid separation is recovered by a separation and circulation unit (4) and transported to a gas distribution plate (11) for recycling.

9. The method for preparing magnesium hydride by concentrated solar fluidized bed catalysis according to claim 8, characterized in that, The standard flow rate of hydrogen is 2 L / min to 20 L / min, and the absolute pressure of the reaction is 0.5 MPa to 2.0 MPa.

10. The method for preparing magnesium hydride using concentrated solar fluidized bed catalysis according to claim 8, characterized in that, The particle size of the magnesium powder is 45μm to 75μm.

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