Planetary gear train solar heat collection reactor for methane reforming reaction

Abstract

The invention relates to the technical field of solar heat collection, in particular to a planetary gear train solar heat collection reactor for methane reforming reaction, which comprises a heat absorption tube and a hollow tube, planetary gears are respectively fixed at two ends of the heat absorption tube, the planetary gears are meshed with gear rings, sun gears are respectively fixedly connected at two ends of the hollow tube, and the sun gears are meshed with the gear rings. The sun gear is meshed with the planet gear, the sun gear is in transmission connection with the servo motor through a rotating shaft, the servo motor drives the sun gear to rotate, and the sun gear drives the planet gear to rotate in the gear ring; a heat absorption pipe direct radiation heating mode is adopted, the heat efficiency of the system is greatly improved, the axial temperature gradient is effectively reduced, the heat absorption pipe is driven by the planetary gear train to move in a three-dimensional mode, and temperature uniformity control is achieved; the problem that an existing solar heat collector is limited in the aspects of efficiency, stability and energy conversion diversity is solved, and the conversion efficiency of methane and carbon dioxide is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar heat collection, and particularly to a planetary gear solar heat collection reactor for methane reforming reaction. Background Art

[0002] In the traditional energy structure, carbon dioxide emissions from fossil fuel combustion account for 76% of the global greenhouse gas emissions (data from the International Energy Agency in 2022), directly leading to a 1.1°C increase in the global average temperature compared to before industrialization; to address climate change, the Paris Agreement requires limiting the temperature rise within 1.5°C, making the clean energy transition extremely urgent; solar energy, as a renewable resource with a theoretical annual supply of 23,000 terawatt-hours (about 8,000 times the global energy consumption), its efficient utilization technology has become the focus of scientific research in various countries; currently, the utilization of solar energy is mainly divided into two major technical routes: photovoltaic power generation (photoelectric conversion) and concentrating solar thermal (CSP), among which solar thermal conversion has attracted much attention due to its heat storage advantage and potential for industrial heat utilization.

[0003] The methane reforming process dominated by fossil fuels (such as steam methane reforming, SMR) faces severe environmental protection pressure due to high carbon emissions (emitting 10 - 12 tons of CO2 per ton of hydrogen produced); according to the statistics of the International Energy Agency (IEA), 96% of global hydrogen production in 2023 relies on fossil fuels, and clean alternative technologies are urgently needed; solar-driven methane reforming directly heats by focusing solar radiation, theoretically reducing carbon emissions by more than 80%, but the existing technologies still have the following bottlenecks: (1) low thermal conversion efficiency: the traditional parabolic trough solar collector system uses heat transfer oil for secondary heat transfer, with a long heat conduction path, resulting in an exergy loss of more than 30%; (2) significant temperature fluctuations: frequent temperature changes accelerate the sintering and deactivation of the catalyst, and its deactivation rate is 3 to 5 times higher than that under steady-state conditions; (3) poor system integration: existing technologies mostly adopt a separated design (the heat collection unit is physically isolated from the reactor), with a large thermal inertia (response time > 30 minutes), and cannot adapt to the transient changes of solar irradiation.

[0004] In the prior art, the patent publication number is CN116123741A, and the name is a solar spectral selective absorption coating for a trough-type solar thermal power generation high-temperature vacuum heat collection tube and its preparation method, which discloses a coating with a three-layer film structure (infrared reflection layer, absorption layer, antireflection layer). The absorption layer is composed of Mo, Al, Si and their nitrides, and is prepared by magnetron sputtering technology, with a temperature resistance of over 800°C; achieving high absorption rate (>95%) and low infrared emissivity (<0.15) in the solar light band, improving the high-temperature stability of the heat collection tube; however, the coating still has thermal attenuation under long-term high temperature (annual efficiency attenuation rate of 7%), and relies on molten salt working medium for heat transfer, requiring auxiliary heating at night, resulting in temperature fluctuations of ±50°C.

[0005] In the prior art, the invention of a methane reformer for producing hydrogen and hydrocarbon fuels with patent publication number CN116171196A discloses an integrated photocatalytic steam reforming (PSMR) and dry reforming (PDMR) system, which uses plasmon photocatalysts (gold / silver nanoparticles) and a multi-stage reactor in series and waste heat power generation design to achieve a methane conversion rate of 78-83% and a total system efficiency of 42%. It has photothermal synergy and energy recycling, but it has the problems of high-temperature sintering deactivation of precious metal catalysts (activity decay rate of 15% / 100 hours) and a 60% increase in equipment complexity and cost.

[0006] In the prior art, the invention of the conical solar methane reforming reactor based on enhanced preheating is named with the patent publication number CN115057410A, which discloses a conical porous medium reaction chamber and an inner and outer material preheating structure, and achieves a reaction conversion rate of more than 95% at a low inlet flow rate by enhancing heat exchange and porous medium heat absorption through a conical baffle. It has high temperature adaptability and heat distribution optimization, but its conversion rate gradually decreases at a higher inlet flow rate, mainly due to the problem of large axial temperature difference. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to propose a planetary gear system solar thermal collection reactor for methane reforming reaction, which adopts the direct radiation heating mode of the heat absorption tube, eliminates the secondary heat transfer loss, cancels the intermediate heat transfer medium, and improves the thermal efficiency of the system to more than 50%, while reducing the axial temperature gradient to <10℃ / m (traditional system>200℃ / m); the heat absorption tube is driven to move three-dimensionally by the planetary gear system to achieve temperature uniformity control; the present invention solves the limitations of existing solar collectors in terms of efficiency, stability and energy conversion diversity, improves the conversion efficiency of methane and carbon dioxide, realizes the efficient utilization of clean energy, and reduces energy consumption and equipment complexity.

[0008] To achieve the above object, the present invention adopts the following technical solution: A planetary gear system solar thermal collection reactor for methane reforming reaction, comprising a heat absorption tube 2 and a hollow tube 6, wherein planetary gears 4 are respectively fixed at both ends of the heat absorption tube 2, and the planetary gears 4 are meshed with a gear ring 5, and sun gears 3 are respectively fixedly connected at both ends of the hollow tube 6, and the sun gear 3 is meshed with the planetary gears 4, and the sun gear 3 is transmission-connected to a servo motor 7 via a rotating shaft, and the servo motor 7 drives the sun gear 3 to rotate, and the sun gear 3 drives the planetary gear 4 to rotate inside the gear ring 5.

[0009] Furthermore, a spectral selective coating is coated on the outer surface of the heat absorption tube 2. The spectral selective coating includes an infrared reflection layer, an absorption layer, and an antireflection layer from outside to inside. The material of the infrared reflection layer is tungsten, the material of the absorption layer is HfNbTaTiZrNO, and the material of the antireflection layer is Al2O3. The inside of the heat absorption tube 2 is filled with a Ni / Al2O3 porous medium foam catalyst.

[0010] Furthermore, the inner wall of the heat absorption tube 2 is a gear-shaped groove 8 or a spiral groove 9. The heat absorption tube 2 is respectively connected to the upper gas collecting box and the lower gas collecting box of the external methane reforming reaction system through a rotary seal joint, and the methane reforming reaction is carried out inside the heat absorption tube 2.

[0011] Furthermore, the solar heat collection reactor further includes a solar heat collector cavity 1. The heat absorption tube 2 and the hollow tube 6 are located inside the solar heat collector cavity 1. The gear ring 5 is fixed at both ends of the solar heat collector cavity 1, and the solar heat collector cavity 1 is provided with a transparent window.

[0012] Furthermore, the servo motor 7 is a permanent magnet synchronous servo motor, and the servo motor 7 is powered and driven by an external molten salt heat storage power generation system to control the rotation speed of the sun gear 3.

[0013] Furthermore, the hollow tube 6 is connected to an external molten salt heat storage power generation system, and a molten salt substance flows inside the hollow tube 6.

[0014] Furthermore, the number of the heat absorption tubes 2 is N, N≥4, and a plurality of planet gears 4 are circumferentially distributed around the sun gear 3 as the axis.

[0015] Furthermore, the axle end of the planet gear 4 adopts a silicon carbide ceramic bearing.

[0016] Furthermore, the solar heat collector cavity 1 is made of high-purity fused quartz.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Through the compound movement of the planetary gear train including the gear ring, the planet gears, and the sun gear, that is, the revolution and rotation of the planetary gear train, the present invention realizes the dynamic temperature adjustment of the heat absorption tube, solves the defect of large temperature gradient (>150 °C / m) of the traditional static reactor. Specifically, the planetary gear train drives the heat absorption tube to rotate three-dimensionally, so that the coverage rate of the light spot trajectory reaches more than 95%, and the axial temperature gradient is reduced to <10 °C / m.

[0018] (2) By integrating the spectral selective coating on the outer surface of the heat absorption tube with direct radiation heating, the present invention eliminates the intermediate heat transfer medium. The multi-layer coating (emissivity ε < 0.15) directly absorbs the focused sunlight, solving the defect that the radiation loss of the traditional tower system caused by molten salt heat transfer is > 40%. In the present invention, the heat efficiency of the methane reforming reaction inside the heat absorption tube is increased by more than 50%.

[0019] (3) Through the groove catalytic bed structure of the heat absorption tube, the spiral grooves or gear-shaped grooves processed on the inner wall of the heat absorption tube increase the specific surface area by 2 to 3 times. Filling the Ni / Al2O3 porous foam catalyst (porosity 85%), the methane conversion rate is increased to more than 85%, solving the problem of low mass transfer efficiency in the fixed bed reactor.

[0020] In summary, compared with the traditional complex heating and reaction system, the structure of the present invention is more concise, easy to manufacture and maintain, reducing the production cost and operation difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the overall structure of the solar heat collection reactor of the present invention.

[0022] Figure 2 is a schematic diagram of the detailed structure of the planetary gear train and transmission of the present invention.

[0023] Figure 3 is a schematic diagram of the gear-shaped groove structure inside the heat absorption tube of the present invention.

[0024] Figure 4 is a flow chart of the present invention.

[0025] Figure 5 is a simulation result diagram of the influence of the inlet temperature and wall temperature of the heat absorption tube on the mass fraction.

[0026] Figure 6 is a simulation result diagram of the influence of the inlet flow rate and wall temperature of the heat absorption tube on the methane conversion rate.

[0027] Figure 7 is a simulation result diagram of the influence of the tube diameter and mass flow rate of the heat absorption tube on the methane conversion rate.

[0028] Figure 8 is a schematic cross-sectional view of the spiral groove structure inside the heat absorption tube of the present invention.

[0029] In the drawings, 1. Solar collector cavity; 2. Heat absorption tube; 3. Sun gear; 4. Planet gear; 5. Ring gear; 6. Hollow tube; 7. Servo motor; 8. Gear-shaped groove; 9. Spiral groove. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following combines the attached Figure 1 to the attached Figure 8The present invention is described in further detail: like Figure 1 and Figure 2 As shown, a planetary gear system solar thermal collection reactor for methane reforming reaction includes a heat absorption tube 2 and a hollow tube 6, wherein planetary gears 4 are fixed at both ends of the heat absorption tube 2, and the planetary gears 4 are meshed with a gear ring 5. Sun gears 3 are fixedly connected at both ends of the hollow tube 6, and the hollow tube 6 is connected to an external molten salt heat storage power generation system. The hollow tube 6 absorbs sunlight heat as a heat source for the molten salt heat storage system. The sun gear 3 is meshed with the planetary gears 4, and the sun gear 3 is connected to a servo motor 7 through a rotating shaft. The servo motor 7 initially uses external electric energy to start the rotation of the sun gear 3. After the molten salt heat storage power generation system generates electricity, the servo motor 7 uses its electric energy to drive the sun gear 3 to rotate. The sun gear 3 drives the planetary gear 4 to rotate inside the gear ring 5. The annular gear ring 5 forms a precise meshing transmission with the planetary gear 4. The upper and lower sun gears 3 at both ends of the hollow tube 6 provide kinetic energy for the planetary gear 4 to rotate and revolve.

[0031] Furthermore, the outer surface of the heat absorption tube 2 is coated with a spectrally selective coating, and the spectrally selective coating comprises an infrared reflection layer, an absorption layer, and an anti-reflection layer coated in sequence from the outside to the inside. The infrared reflection layer material is tungsten, that is, the infrared reflection layer is a tungsten layer, and the absorption layer material is HfNbTaTiZrNO, that is, the absorption layer is a high entropy oxynitride layer, wherein HfNbTaTiZrNO represents oxynitride (NO) of hafnium (Hf), niobium (Nb), tantalum (Ta), titanium (Ti), and zirconium (Zr), and the anti-reflection layer material is Al2O3 (aluminum oxide layer). The spectrally selective coating has an emissivity of <0.15, and the light The absorption rate of the spectrally selective coating is ≥0.95. The interior of the heat absorption tube 2 is filled with a Ni / Al2O3 porous medium foam catalyst for catalyzing the methane reforming reaction under high temperature conditions to improve the conversion efficiency. The two ends of the heat absorption tube 2 are respectively connected to the upper gas collecting box and the lower gas collecting box of the methane reforming reaction system. The methane reforming reaction gas (i.e., CO2 and methane) is evenly mixed in the upper gas collecting box through a vortex distributor, and then enters the heat absorption tube 2 for reaction. The H2 and CO gases generated by the reaction in the heat absorption tube 2 are discharged through the exhaust port of the lower gas collecting box. The lower gas collecting box is used to collect and output the reaction products. The methane reforming reaction is carried out in the heat absorption tube 2.

[0032] Further, if Figure 3 and Figure 8 As shown, the inner wall of the heat absorbing tube 2 is provided with gear-shaped grooves 8 or spiral grooves 9, which increase the reaction contact area in the tube and improve the anti-erosion performance.

[0033] The heat absorbing pipe 2 is respectively connected to the upper gas collecting box and the lower gas collecting box of the external methane reforming reaction system through a rotary sealing joint.

[0034] Furthermore, the solar heat collector reactor further includes a solar heat collector cavity 1. The heat absorption tube 2 and the hollow tube 6 are located inside the solar heat collector cavity 1. The gear ring 5 is fixed at both ends of the cylindrical solar heat collector cavity 1. The solar heat collector cavity 1 is provided with a transparent window, and the transparent window is made of a material with a high light transmittance, such as a high light transmittance quartz window. The solar heat collector cavity 1 is made of high-purity fused quartz and is used to absorb solar heat.

[0035] Furthermore, the servo motor 7 is a permanent magnet synchronous servo motor, and the servo motor is powered and driven by a molten salt energy storage power generation system to control the rotation and speed of the sun gear 3.

[0036] Furthermore, the hollow tube 6 is connected to an external energy storage power generation system for circulation. The inside of the hollow tube 6 can be used for flowing molten salt substances, and the molten salt substances collect heat through the solar heat collector. The molten salt energy storage power generation system applicable to the present invention includes a high-temperature tank and a low-temperature tank to achieve continuous power supply for 24 hours. The waste heat of the molten salt can drive an engine (such as a Stirling engine) to generate electricity and then supply power to the servo motor 7 to form a closed-loop energy utilization.

[0037] Furthermore, the number of the heat absorption tubes 2 is N, N≥4. A plurality of planet gears 4 are circumferentially evenly distributed around the sun gear 3 at an angle of 360° / N. The selection of the number N is determined according to the size of the heat collector, and motion decoupling is achieved through differential gears.

[0038] Furthermore, the axle end of the planet gear 4 uses a silicon carbide ceramic bearing, and its maximum tolerable temperature reaches 1600°C to ensure low-friction operation in a high-temperature environment.

[0039] The solar methane reforming reactor of the present invention makes full use of renewable energy technology, improves the conversion efficiency of methane and carbon dioxide, reduces greenhouse gas emissions, and conforms to the current environmental protection and sustainable development trends.

[0040] Through the innovative design of the planetary gear train, the present invention makes the mixed gas inside the pipeline evenly heated, improves the conversion efficiency of methane and carbon dioxide, and the inside of the heat absorption tube is designed with grooves and protrusions to increase the reaction contact area inside the tube and improve the erosion resistance performance. Compared with the traditional technology, the energy utilization is more sufficient and the conversion rate is higher; the solar heat is absorbed as the main heat source, reducing the use of traditional fossil fuels, thereby reducing the energy consumption of the whole system; through the efficient methane reforming reaction, the present invention realizes the conversion of clean energy, not only reducing greenhouse gas emissions, but also producing recyclable hydrogen and carbon monoxide, which helps to reduce the environmental burden.

[0041] The following uses Example 1 to simulate and verify the feasibility of the present invention.

[0042] I. Matching of Solar Heat Collection Reactor and External Tower-Type Solar Power Generation System The existing tower-type solar thermal power generation system includes a heliostat field with a tracking control drive mechanism, a heat collection and heat absorption device, a heat storage device, and a generator set. Its working principle is as follows: The heliostat with a tracking control drive mechanism is used to track sunlight so as to concentrate it on the heat absorber at the top of the heat collection tower. In the heat absorber, solar energy is converted into the thermal energy of the working fluid, and the high-temperature and high-pressure working fluid drives the steam turbine to do work and generate electricity. The advantages of the tower-type solar thermal power generation system are high concentration ratio, relatively high working temperature of the working fluid (1000 - 1500 °C), large concentration ratio, up to 1:500 at most, and annual power generation efficiency of 17% - 20%. For example, a 10 MW molten salt tower-type solar thermal power station has a maximum annual power generation hours of 5250 h, an annual power generation of about 52500 MWh, and a rated heat absorption power of about 80 MW th 。

[0043] The solar heat collection reactor of the present invention is the heat collection and heat absorption device in the above-mentioned tower-type solar thermal power generation system. The specific parameters of the solar heat collector cavity, planetary gear train drive module, and heat absorption reaction integrated component in Embodiment 1 are as follows: 1. Solar heat collector cavity Most of the surface area of the solar heat collector cavity 1 is made of quartz glass. The quartz glass is made into a window with high-purity fused quartz (SiO2 content > 99.9%), and its light transmittance is > 92% in the 300 - 2500 nm band, ensuring efficient transmission of the entire solar spectrum band; the top and bottom of the solar heat collector cavity 1 can fix the gear ring 5 through high-precision flanges (tolerance ±0.05 mm). The flange material can be Inconel 718, with a temperature resistance of 1100 °C, and forms a precise meshing drive with the planetary gear 4.

[0044] The solar heat collector cavity 1 is designed to be 9 m in height and 7.5 m in diameter.

[0045] 2. Planetary gear train drive module (1) Servo motor and sun gear: Select a 200 kW permanent magnet synchronous servo motor 7, whose speed is adjustable from 1 - 30 rpm and has short-term overload capacity. It is rigidly connected to the sun gear 3 through a silicon carbide hollow shaft with a thermal conductivity of 120 W / m·K; the surface of the sun gear 3 is nitrided to enhance wear resistance, with a surface hardness of HV1100 and a wear rate < 0.01 mm³ / (N·m).

[0046] (2) Planetary gear set: The planetary gears 4 (taking 100 groups as an example) are evenly distributed around the sun gear 3, with a revolution to self-rotation speed ratio of 1:18. The size of the planetary gear train can be adjusted according to actual needs, and motion decoupling is achieved through differential gears; the shaft ends of the planetary gears 4 use silicon carbide ceramic bearings (temperature resistance 1600 °C) to ensure low-friction operation in a high-temperature environment.

[0047] The ring gear (internal gear ring) is adopted to drive the planet gear 4, and the pitch circle diameter D of the internal gear ring ring = 7.5 m (aligned with the outer wall of the solar heat collection cavity), and the pitch circle diameter D of the planet gear 4 p = 0.2 m (consistent with the outer diameter of the heat absorption tube), the module m = 10 mm, meeting the strength requirements, the addendum coefficient = 1, the dedendum coefficient = 1.25, then the number of teeth Z of the internal gear ring ring = 750 teeth; the number of teeth Z of the planet gear p = 20 teeth; the meshing center distance = 3.65 m; the addendum circles of adjacent planet gears need to avoid interference, and it is necessary to meet: the chord length of the center distance ≥ the addendum circle diameter + the safety side clearance; the addendum circle diameter of the planet gear: ; the safety side clearance is taken as 5 mm, then the minimum allowable center distance C min = 0.225 m; the circumference L of the circumferential distribution of the planet gears is approximately 23.56 m, so the number n that can be arranged is approximately 104.7, and n = 100 is selected in this embodiment.

[0048] Center angle of adjacent planet gears: ; Then the actual chord length of the center distance , meeting C ≥ C min , without interference.

[0049] (3) Dynamic temperature regulation mechanism: The planet gear 4 drives the heat absorption tube 2 to perform a three-dimensional composite motion with a revolution period of 180 seconds and a rotation period of 10 seconds (corresponding to the revolution-rotation ratio), so that the coverage rate of the focused light spot on the surface of the heat absorption tube 2 > 95%, greatly eliminating local overheating caused by static heating, and the coverage rate of the traditional system is only about 65%.

[0050] 3. Heat absorption reaction integrated component (1) Structure of the heat absorption tube: The outer wall of the heat absorption tube 2 is coated with multiple layers of spectral selective coatings with a thickness of 200 nm. The thermal emissivity ε of this coating at a high temperature of 800 - 1000 °C < 0.15, significantly reducing the radiant heat loss by 65%. The heat absorption tube 2 is made of nickel-based alloy Inconel600 / 601, with a temperature resistance of 1150 °C, anti-carburization and oxidation, and its material density is 8100 kg / m 3 , then the mass of a single heat absorption tube 2 is 1353 kg. 100 heat absorption tubes 2 are used, and each heat absorption tube 2 has a length of 7 m, an outer diameter of 200 mm, and a wall thickness of 10 mm. Spiral grooves 8 with a depth of 5 mm and a pitch of 9 mm are machined on the inner wall, increasing the specific surface area by 2 to 3 times, while enhancing gas turbulence and promoting mass transfer and heat transfer.

[0051] (2) Catalyst bed: Filled with Ni / Al2O3 porous foam, with a porosity of 85%, pore diameter of 0.5 - 1 mm, specific surface area reaching 320 m² / g, and the density of active sites increased by 3 times compared to traditional particulate catalysts.

[0052] (3) Gas path sealing system: The upper gas collecting box and the lower gas collecting box of the external methane reforming reaction system are connected to the heat absorption tube 2 through a high-temperature rotary seal joint. The material of the rotary seal joint is graphite / metal composite material, with a leakage rate <0.01%. An eddy current distributor is set at the air inlet of the upper gas collecting box to make the flow rate distribution uniformity deviation of the CH4 and CO2 mixed gas with a molar ratio of 1:1 <5%.

[0053] The heat absorption tube is verified through detailed gear design. Considering a 5 mm safety side clearance and adjacency conditions, up to 104 heat absorption tubes can be arranged along the outer wall of the cavity. With a 2% redundancy reserved, 100 heat absorption tubes are selected, and the total load is 1326 KN.

[0054] Moment of inertia of the heat absorption tube around the central axis (regarded as a particle): ; With a rotational speed of 30 rpm, the angular velocity is ; When the startup time is 60 s, the angular acceleration ; Startup torque ; Then the startup efficiency ; Considering actual losses, when the transmission efficiency is 90%, P actual ≈ 348 kW; When the rotational speed is 30 rpm, the motor power required to drive 100 heat absorption tubes to rotate is approximately 313.2 kW (startup stage), and actually 348 kW is required considering transmission losses; during steady-state operation, the power is mainly used to overcome friction and air resistance, and approximately 150 - 300 kW of power is consumed according to different working conditions; According to the power generation per unit area of the mirror field being 200 W / m 2 , to meet the power demand, a mirror field area of approximately 1500 m 2 is required; The waste heat of the molten salt drives the Stirling engine to generate 4.65 MWe of electric energy, and the generated electric energy is supplied to the servo motor in the present invention, which is much higher than the power demand of the 348 kW gear system.

[0055] 4. Waste heat power generation for energy supply The molten salt thermal energy storage power generation system externally connected to the present invention can use a 60% NaNO3 + 40% KNO3 mixed molten salt, with a melting point of 220 °C and a working temperature of 290 - 565 °C. The mixed molten salt circulates through the inner cavity of the hollow tube 6 in the present invention, and the maximum peak heat flux density is at least 1.5 MW / m 2 . The molten salt thermal energy storage power generation system includes a high-temperature tank (optimal working temperature 565 °C) and a low-temperature tank (290 °C). The diameter of the thermal energy storage tank is 20 m, the height of the tank is 10 m, and the volume is 2660 m 3, heat storage capacity is 500 MWh th , the duration of heat release from heat storage is 15 h; the temperature difference of molten salt waste heat is 290 - 350 °C, which can drive a Stirling engine to generate electricity, with a thermoelectric conversion efficiency of 16%, corresponding to the generated electric energy of 4.65 MWe. The generated electric energy is supplied to the servo motor 7 in the present invention to form a closed-loop energy utilization; the surplus electric energy is incorporated into the power grid or used for other devices, such as control systems, pumps and valves, etc.

[0056] In the first embodiment, the power generation power of the tower-type power station is matched to 10 MW. In actual engineering, the mirror area of the tower-type system is usually tens of thousands to hundreds of thousands of square meters (for example, the total daylighting area of the 10 MW molten salt tower-type solar thermal power station in Dunhuang is 175,000 m 2 ), far exceeding the demand, and the power supply is completely redundant.

[0057] II. Matching between the heat collection temperature in the solar heat collection reactor and the methane reforming reaction 1. Assumptions of the methane reforming reaction model In the present invention, the FLUENT software in ANSYS is used for numerical simulation. During the research on methane reforming for hydrogen production under concentrated irradiation, the multi-component transport model, porous medium model, energy exchange model, radiation heat transfer model and chemical reaction model of this software are used for simulation calculation; since the calculation area of the heat absorption tube used in the present invention is axisymmetric, it can be simplified to a two-dimensional model. During the simulation process, the mass flow inlet is adopted for the gas inlet. The assumptions of this simulation study on the reaction process are as follows: (1) The mixed gas is an incompressible ideal gas and is mixed evenly before entering the reactor; (2) The catalyst is evenly distributed in the heat absorption tube, so the reaction occurs in the heat absorption tube, and the reactants are surface reactions in the heat absorption tube; (3) Radiation heat transfer is ignored during the reaction process; (4) Only one-step overall reaction is considered for the catalytic reaction of CO2 reforming CH4.

[0058] Methane conversion rate: In the formula: —— Methane conversion rate, %; —— Mole fraction of methane at the reactor inlet; —— Mole fraction of methane at the reactor outlet.

[0059] 2. Simulation settings and result analysis The present invention uses a two-dimensional axisymmetric steady incompressible laminar finite rate model to calculate the reforming reaction process in the tube. The density of the gas mixture conforms to the incompressible ideal gas law. The mass diffusion adopts the kinetic theory, and polynomial fitting is used for each individual component to consider the influence of temperature on the specific heat capacity. The inlet is a velocity inlet boundary, the outlet is a pressure outlet boundary, and the tube wall is a no-slip constant wall temperature boundary (T wall = 800 °C). The reaction region is a simple isotropic porous medium, and the volume reaction is used to consider the influence of the catalyst and structural parameters on the reaction in the tube. The grid division of the calculation model uses quadrilateral grids, and the near-wall region and the porous medium region are encrypted. The pressure-velocity coupling adopts the Simple algorithm, the pressure discretization is Standard, and the other governing equations are discretized using the second-order upwind scheme. The residual of the energy equation ≤ 10 -8 , and the residuals of the other governing equations ≤ 10 -6 .

[0060] The numerical model uses a small-size model, a smooth quartz tube with an inner diameter d = 0.01 m and L = 0.7 m. The length of the porous medium L catalyst = 0.4 m, and Ni / Al2O3 is used as the reaction catalyst. The reaction gas with CH4 / CO2 = 1:1 enters from one end of the endothermic tube, the inflow velocity is 0.2 m / s, and flows out from the other end after the reaction. In the numerical model, the tube wall thermal boundary is approximately treated with a constant wall temperature, and the influence of the tube wall thickness on heat transfer is ignored. Table 1 shows the numerical simulation results of the conversion rate under different working conditions.

[0061] Table 1 Methane conversion rates under different reaction conditions In Table 1, T wall (K): the wall temperature of the endothermic tube; T in (K): the inlet temperature of the endothermic tube; S / V (m -1 ): surface-volume ratio; λ catalys thermal conductivity of the porous medium; CH 4in : methane mole fraction at the inlet of the endothermic tube; CH 4out : methane mole fraction at the outlet of the endothermic tube; X CH4 (%): methane conversion rate.

[0062] Discussions are carried out for the fluid inlet temperature at normal temperature 25 °C and preheated to 600 °C, and the wall temperature at 600 °C, 800 °C, and 1000 °C to study the influence of the inlet temperature and the heating temperature on the thermochemical reaction; such as Figure 5As shown, the initial reaction rate is very high, and the mass fraction of methane decreases rapidly. The conversion rate exceeds 95% at the length of the catalytic section. The curves can be divided into a 25°C curve family and a 600°C curve family. Curves with the same inlet temperature are close, while curves with different inlet temperatures are far apart. At the same inlet temperature, as the wall temperature increases, the reaction rate speeds up, the reaction proceeds faster, and the methane conversion rate increases. When the inlet fluid is preheated to T in of 600°C and the wall temperature is 1000°C, the influence of flow rate on the thermochemical reaction is studied under different inlet flow rates. As Figure 6 shown, it is found that the influence of inlet flow rate on the reaction is relatively complex, mainly reflected in three aspects: 1. Residence time. An increase in flow rate leads to a shortening of the residence time of the reactants, which is not conducive to sufficient reaction. 2. Reaction temperature. Too fast a flow rate will result in a lower temperature at the center of the reaction tube, which is not conducive to the reaction. 3. Local concentration of reactants. Under the condition of constant pipe diameter, increasing the flow rate can correspondingly increase the concentration of reactants, which can appropriately increase the reaction rate. At low flow rates, factor 3 plays a major role; at high flow rates, factors 1 and 2 play a major role. From Figure 6 the analysis, it can be seen that changing the wall temperature has little effect on the conversion rate at low flow rates, while at high flow rates, increasing the wall temperature can significantly increase the conversion rate.

[0063] When the inlet fluid is preheated to 600°C, the wall temperature is 1000°C, and the inlet mass flow rate is different, the influence of pipe diameter and inlet mass flow rate on the thermochemical reaction is studied. As Figure 7 shown, the combined effect of reaction pipe diameter and mass flow rate on the reaction is relatively complex, and the analysis is as follows: Observing the two curves, the trend is to increase first and then decrease. As the pipe diameter increases, the temperature distribution becomes more uneven, and the center temperature is lower, which is not conducive to the reaction. However, the velocity gradually decreases. According to the above analysis, a low velocity is conducive to increasing the conversion rate at low velocities. The trend of the curve is the result of the combined action of the two.

[0064] Comparing the two curves, the conversion rate is higher at low flow rates with a small pipe diameter, and the conversion rate is higher at high flow rates with a large pipe diameter. This is because at a small pipe diameter, the velocity is relatively large, and factors 1 and 2 that hinder the reaction play a major role, so the conversion rate is higher for the lower velocity; while at a large pipe diameter, the velocity is very small, and factor 3 that promotes the reaction plays a major role, and the conversion rate is higher for the higher velocity.

[0065] 3. Verification of the Feasibility of the Present Invention by Simulation Results (1) Matching of High-Temperature Stability and Reaction Efficiency The simulation results show that when the wall temperature is 1000 °C (1273 K) and the inlet is preheated to 600 °C (873 K), the methane conversion rate can reach 99.54%, proving that the endothermic tube can achieve near-complete conversion under high-temperature conditions; in the first embodiment of the present invention, the tower-type solar collector can provide a stable heat source of 800 - 1000 °C (verified above), which highly matches the optimal reaction temperature (1000 °C) in the simulation, verifying the synergy between solar heating and the design of the endothermic tube; in the simulation, the temperature distribution uniformity is achieved through the constant wall temperature boundary condition, while in the present invention, the rotation and revolution of the endothermic tube driven by the planetary gear train can further enhance heat transfer, avoid local overheating or cold zones, and ensure the catalytic efficiency.

[0066] (2) Controllability of flow rate and residence time The simulation shows that within the flow rate range of 0.1 - 1 m / s, by adjusting the wall temperature (800 - 1000 °C), the methane conversion rate can be maintained at 90% - 97%, proving that the endothermic tube has strong adaptability to flow rate fluctuations; in the present invention, the servo motor can indirectly control the rotation speed of the endothermic tube by adjusting the rotation speed of the sun gear, thereby optimizing the gas residence time and flow rate distribution (such as extending the residence time at low speed and enhancing turbulent mixing at high speed).

[0067] (3) Structural scalability and engineering adaptability When the pipe diameter in the simulation is enlarged from 0.01 m to 0.1 m, by adjusting the inlet mass flow rate (0.1 - 0.2 g / s), the conversion rate can still be maintained > 90%, indicating that the design of the endothermic tube has good scalability; in the large-scale design of the present invention, 100 endothermic tubes are used in a circular array, combined with the uniform distribution characteristics of the porous medium catalyst in the simulation, which can ensure that the reaction efficiency of each pipeline in the large-scale reactor is consistent.

[0068] The above supplementary materials combine actual engineering parameters and simulation to fully verify the feasibility and technical advantages of the present invention.

[0069] The working principle of the present invention is as follows: As Figure 4As shown in the figure, the external heliostat field reflects sunlight to the solar collector cavity 1, focusing to form a high-density light spot (energy density > 1000 W / m²). The light spot penetrates the high-transmission quartz window and is absorbed by the spectral selective coating on the outer surface of the heat absorption tube 2, quickly heating up to over 850°C. The servo motor 7 drives the sun gear 3 to rotate, driving the planet gear 4 to revolve and rotate. The heat absorption tube 2 rotates synchronously with the planetary gear train, enabling the focused light spot to fully cover the tube surface (coverage rate > 95%), and the axial temperature gradient of the heat absorption tube 2 is reduced to < 10°C / m. The CH4 and CO2 mixed gas inside the heat absorption tube 2 uniformly enters the heat absorption tube 2 through the eddy current distributor of the upper gas collector. The mixed gas undergoes a reforming reaction under the action of the Ni / Al2O3 porous foam catalyst. The groove structure on the inner wall of the heat absorption tube 2 enhances the turbulence intensity, and the methane conversion rate reaches over 90%. The H2 and CO generated by the methane reforming reaction are output through the rotary seal joint of the lower gas collector. The molten salt circulating inside the hollow tube 6 absorbs heat and supplies the molten salt thermal energy storage power generation system to maintain continuous power generation operation. The reaction waste heat drives the external Stirling engine to convert the molten salt waste heat into electrical energy (efficiency 16%), supplying the servo motor 7 to form an energy self-circulation.

Claims

1. A planetary gear train solar collector reactor for methane reforming reaction, characterized in that, The invention comprises a heat absorbing tube (2) and a hollow tube (6), wherein planetary gears (4) are respectively fixed at both ends of the heat absorbing tube (2), wherein the planetary gears (4) mesh with a gear ring (5), and wherein sun gears (3) are respectively fixedly connected at both ends of the hollow tube (6), wherein the sun gear (3) meshes with the planetary gears (4), wherein the sun gear (3) is transmission-connected to a servo motor (7) via a rotating shaft, wherein the servo motor (7) drives the sun gear (3) to rotate, and the sun gear (3) drives the planetary gears (4) to rotate inside the gear ring (5).

2. The solar heat collection reactor according to claim 1, wherein, The outer surface of the heat absorbing tube (2) is coated with a spectrally selective coating, the spectrally selective coating comprising, from the outside to the inside, an infrared reflection layer, an absorption layer, and an anti-reflection layer, the infrared reflection layer material is tungsten, the absorption layer material is HfNbTaTiZrNO, the anti-reflection layer material is Al2O3, and the interior of the heat absorbing tube (2) is filled with a Ni / Al2O3 porous medium foam catalyst.

3. The solar heat collection reactor according to claim 1, characterized in that, The inner wall of the heat absorption tube (2) is provided with a gear-shaped groove (8) or a spiral groove (9), and the heat absorption tube (2) is respectively connected to an upper gas collecting box and a lower gas collecting box of an external methane reforming reaction system through a rotary sealing joint, and a methane reforming reaction is carried out in the heat absorption tube (2).

4. The solar heat collection reactor according to claim 1, characterized in that, The solar thermal collection reactor further comprises a solar thermal collector cavity (1), the heat absorption tube (2) and the hollow tube (6) are located inside the solar thermal collector cavity (1), the gear ring (5) is fixed at both ends of the solar thermal collector cavity (1), and the solar thermal collector cavity (1) is provided with a transparent window.

5. The solar heat collection reactor according to claim 1, characterized in that, The servo motor (7) is a permanent magnet synchronous servo motor, and the servo motor (7) is powered by an external molten salt heat storage power generation system to drive and control the rotation speed of the sun wheel (3).

6. The solar heat collection reactor according to claim 1, wherein, The hollow tube (6) is connected to an external molten salt heat storage power generation system, and molten salt material flows inside the hollow tube (6).

7. The solar heat collection reactor according to claim 1, wherein The number of the heat absorption tubes (2) is N, where N is greater than or equal to 4, and the plurality of planetary gears (4) are evenly distributed around the circumference of the sun gear (3) with the sun gear (3) as the axis.

8. The solar heat collection reactor according to claim 1, characterized in that, The wheel shaft end of the planetary wheel (4) adopts a silicon carbide ceramic bearing.

9. The solar heat collection reactor according to claim 4, wherein, The solar collector cavity (1) is made of high-purity fused quartz.

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