A planetary gear system solar thermal reactor for methane reforming reaction

Abstract

The present invention relates to the field of solar heat collection technology, and specifically to a planetary gear system solar heat collection reactor for methane reforming reaction, the heat collection reactor comprising a heat absorption tube and a hollow tube, planetary gears are respectively fixed at both ends of the heat absorption tube, the planetary gears are meshed with a gear ring, and sun gears are respectively fixedly connected at both ends of the hollow tube, the sun gears are meshed with the planetary gears, the sun gear is connected to a servo motor through a rotating shaft, the servo motor drives the sun gear to rotate, and the sun gear drives the planetary gears to rotate inside the gear ring; the present invention adopts a direct radiation heating mode of the heat absorption tube, which greatly improves the thermal efficiency of the system, effectively reduces the axial temperature gradient, and realizes temperature uniformity control by driving the heat absorption tube to move in three dimensions through the planetary gear system; the present invention solves the limitations of existing solar collectors in terms of efficiency, stability and energy conversion diversity, and improves the conversion efficiency of methane and carbon dioxide.

Description

Technical Field

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

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

[0003] Fossil fuel-dominated methane reforming processes (such as steam methane reforming, SMR) face severe environmental pressure due to their high carbon emissions (10-12 tons of CO2 are emitted for every ton of hydrogen produced). According to statistics from the International Energy Agency (IEA), 96% of global hydrogen production in 2023 will rely on fossil fuels, and clean alternative technologies are urgently needed. Solar-driven methane reforming directly provides heat by focusing solar radiation, which can theoretically reduce carbon emissions by more than 80%. However, existing technologies still have the following bottlenecks: (1) Low thermal conversion efficiency: Traditional parabolic trough heat collection systems use thermal oil for secondary heat transfer, and the heat conduction path is long, resulting in an effective energy loss of more than 30%; (2) Significant temperature fluctuations: Frequent temperature changes accelerate catalyst sintering and deactivation, and its deactivation rate is 3 to 5 times higher than that under steady-state conditions; (3) Poor system integration: Existing technologies mostly use a separate design (the heat collection unit is physically isolated from the reactor), with large thermal inertia (response time > 30 minutes), and cannot adapt to transient changes in solar radiation.

[0004] In the existing technology, the patent publication number CN116123741A, entitled "A solar spectrum selective absorption coating for trough-type thermal power generation high-temperature vacuum collector tubes and its preparation method", discloses a coating with a three-layer film structure (infrared reflection layer, absorption layer, anti-reflection layer). The absorption layer is composed of Mo, Al, Si and their nitrides, and is prepared using magnetron sputtering technology. It has a temperature resistance of over 800°C; it achieves high absorptivity (>95%) and low infrared emissivity (<0.15) in the solar band, improving the high-temperature stability of the collector tube; however, the coating still suffers from thermal attenuation (annual efficiency attenuation rate of 7%) under long-term high temperatures, and relies on molten salt working fluid for heat transfer, requiring auxiliary heating at night, resulting in temperature fluctuations of ±50°C.

[0005] In the existing technology, 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. It uses plasmonic photocatalysts (gold / silver nanoparticles) and a multi-stage reactor 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. However, 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 a conical solar methane reforming reactor with patent publication number CN115057410A and titled "Conical Solar Methane Reforming Reactor Based on Enhanced Preheating" discloses a conical porous medium reaction chamber and an inner and outer material preheating structure. The conical baffles enhance heat exchange and porous medium heat absorption, thereby achieving a reaction conversion rate of over 95% at low inlet flow rates. The reactor has high temperature adaptability and optimized heat distribution. However, its conversion rate gradually decreases at higher inlet flow rates, mainly due to the large axial temperature difference. Summary of the Invention

[0007] To overcome the shortcomings of the above-mentioned prior art, the present invention aims to propose a planetary gear system solar thermal collector reactor for methane reforming reactions. By adopting a direct radiation heating mode of the heat absorber tube, secondary heat transfer losses are eliminated and the intermediate heat transfer medium is eliminated, the system thermal efficiency is increased to more than 50%, and the axial temperature gradient is reduced to <10°C / m (traditional systems are >200°C / m). The planetary gear system drives the three-dimensional movement of the heat absorber tube 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 solutions:

[0009] A planetary gear system solar heat collection reactor for methane reforming reaction includes a heat absorption tube 2 and a hollow tube 6. Planetary gears 4 are fixed at both ends of the heat absorption tube 2, and the planetary gears 4 are engaged with a gear ring 5. Sun gears 3 are fixedly connected at both ends of the hollow tube 6, and the sun gear 3 is engaged with the planetary gears 4. The sun gear 3 is connected to the servo motor 7 through a rotating shaft. 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.

[0010] Furthermore, the outer surface of the heat absorbing tube 2 is coated with a spectrally selective coating, which comprises, 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, and the anti-reflection layer material is Al2O3. The interior of the heat absorbing tube 2 is filled with a Ni / Al2O3 porous medium foam catalyst.

[0011] 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 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, and a methane reforming reaction is carried out in the heat absorption tube 2.

[0012] Furthermore, the solar thermal collection reactor also includes 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.

[0013] Furthermore, 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 control the rotation speed of the sun gear 3.

[0014] Furthermore, 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 .

[0015] Furthermore, the number of the heat absorption tubes 2 is N, where N≥4, and the plurality of planetary gears 4 are evenly distributed around the circumference with the sun gear 3 as the axis.

[0016] Furthermore, the axle ends of the planetary gears 4 use silicon carbide ceramic bearings.

[0017] Furthermore, the solar collector cavity 1 is made of high-purity fused quartz.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention achieves dynamic temperature control of the heat absorption tube through the composite motion of the planetary gear train including the gear ring, planetary gears and sun gear, i.e., the planetary gear train revolves and rotates, thereby solving the defect of large temperature gradient (>150℃ / m) in traditional static reactors. Specifically, the planetary gear train drives the heat absorption tube to rotate three-dimensionally, so that its spot track coverage rate reaches more than 95%, and the axial temperature gradient is reduced to <10℃ / m.

[0020] (2) The present invention integrates the spectrally selective coating on the outer surface of the heat absorbing tube with direct radiation heating, eliminating the intermediate heat transfer medium. The multi-layer coating (emissivity ε < 0.15) directly absorbs the focused sunlight, solving the defect of the traditional tower system with radiation loss > 40% caused by molten salt heat transfer. The thermal efficiency of the methane reforming reaction inside the heat absorbing tube in the present invention is improved by more than 50%.

[0021] (3) The present invention adopts a heat-absorbing tube groove catalytic bed structure, spiral grooves or gear-shaped grooves processed on the inner wall of the heat-absorbing tube, and the specific surface area is increased by 2 to 3 times. The Ni / Al2O3 porous foam catalyst (porosity 85%) is filled, and the methane conversion rate is increased to more than 85%, thereby solving the problem of low mass transfer efficiency of fixed-bed reactors.

[0022] In summary, compared with the traditional complex heating and reaction system, the structure of the present invention is simpler, easier to manufacture and maintain, and reduces production costs and operating difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the solar heat collection reactor of the present invention.

[0024] Figure 2 It is a schematic diagram of the detailed structure of the planetary gear train and transmission of the present invention.

[0025] Figure 3 It is a schematic diagram of the gear-shaped groove structure inside the heat absorption tube of the present invention.

[0026] Figure 4 It is a flow chart of the present invention.

[0027] Figure 5 This is the simulation result diagram of the influence of the absorber tube inlet temperature and wall temperature on the mass fraction.

[0028] Figure 6 This is the simulation result of the effect of the absorption tube inlet flow rate and wall temperature on the methane conversion rate.

[0029] Figure 7 This is the simulation result diagram of the influence of the absorber tube diameter and mass flow rate on the methane conversion rate.

[0030] Figure 8 It is a schematic cross-sectional view of the spiral groove structure inside the heat absorption tube of the present invention.

[0031] In the attached figure, 1. solar collector cavity; 2. heat absorption tube; 3. sun gear; 4. planetary gear; 5. gear ring; 6. hollow tube; 7. servo motor; 8. gear-shaped groove; 9. spiral groove. DETAILED DESCRIPTION

[0032] The following is combined with Figure 1 To the attached Figure 8The present invention is described in further detail:

[0033] 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 the gear ring 5. The two ends of the hollow tube 6 are respectively fixedly connected with sun gears 3. At the same time, the hollow tube 6 is connected to the 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 the servo motor 7 through a rotating shaft. The servo motor 7 initially uses external electrical 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 electrical 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 and the planetary gear 4 form a precise meshing transmission. 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.

[0034] 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 nitrogen oxide layer, wherein HfNbTaTiZrNO represents nitrogen oxides (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 emissivity of the spectrally selective coating is <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.

[0035] 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.

[0036] The heat absorption 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.

[0037] Furthermore, the solar thermal collection reactor also includes 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 cylindrical solar thermal collector cavity 1, and the solar thermal collector cavity 1 is provided with a transparent window, which is made of a high-transmittance material, such as a high-transmittance quartz window. The solar thermal collector cavity 1 is made of high-purity fused quartz to absorb solar heat.

[0038] Furthermore, the servo motor 7 is a permanent magnet synchronous servo motor, which is powered and driven by the molten salt heat storage power generation system to control the rotation and speed of the sun gear 3.

[0039] Furthermore, the hollow tube 6 is connected to an external heat storage power generation system for circulation, and the interior of the hollow tube 6 can be used to flow through a molten salt material, and the molten salt material collects heat through a solar collector; the molten salt energy storage power generation system applicable to the present invention includes a high-temperature tank and a low-temperature tank, which can achieve 24-hour continuous energy supply. 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, forming a closed-loop energy utilization.

[0040] Furthermore, the number of the heat absorption tubes 2 is N, N≥4, and multiple planetary gears 4 are evenly distributed around the sun gear 3 as the axis, and are evenly distributed at an angle of 360° / N. The number N is selected according to the size of the collector, and motion decoupling is achieved through differential gears.

[0041] Furthermore, the axle end of the planetary gear 4 adopts a silicon carbide ceramic bearing, which has a maximum temperature resistance of 1600°C, ensuring low-friction operation in a high-temperature environment.

[0042] The solar methane reforming reactor of the present invention fully utilizes renewable energy technology, improves the conversion efficiency of methane and carbon dioxide, reduces greenhouse gas emissions, and conforms to the current trend of environmental protection and sustainable development.

[0043] The present invention uses an innovative planetary gear system design to ensure that the mixed gas inside the pipeline is heated evenly, thereby improving the conversion efficiency of methane and carbon dioxide. The grooves and protrusions are designed inside the heat absorption tube to increase the reaction contact area inside the tube and improve the erosion resistance. Compared with traditional technologies, energy utilization is more sufficient and the conversion rate is higher. By absorbing solar heat as the main heat source, the use of traditional fossil fuels is reduced, thereby reducing the energy consumption of the entire system. The present invention realizes the conversion of clean energy through efficient methane reforming reaction, which not only reduces greenhouse gas emissions, but also produces recyclable hydrogen and carbon monoxide, which helps to reduce the environmental burden.

[0044] The feasibility of the present invention is verified by simulation using Example 1 below.

[0045] 1. Compatibility of solar thermal reactors with external tower solar power generation systems

[0046] Existing tower solar thermal power generation systems include a heliostat field with a tracking control transmission mechanism, a heat collection and absorption device, a heat storage device, and a generator set. Their operating principle is as follows: Sunlight is tracked by heliostats with a tracking control transmission mechanism so that it is concentrated onto a heat absorber at the top of the collector tower. In the heat absorber, solar energy is converted into thermal energy from a working fluid, and the high-temperature, high-pressure working fluid drives a steam turbine to generate power. The advantages of tower solar thermal power generation systems are high concentration multiples, high working fluid operating temperatures (1000-1500°C), a large concentration ratio (up to 1:500), and an annual power generation efficiency of 17%-20%. For example, a 10MW molten salt tower solar thermal power station has a maximum annual power generation of 5250 hours, an annual power generation of approximately 52,500MWh, and a rated thermal absorption power of approximately 80MW. th .

[0047] The solar thermal reactor of the present invention is the heat collection and absorption device in the tower solar thermal power generation system. The specific parameters of the solar thermal collector cavity, planetary gear drive module and endothermic reaction integrated component in Example 1 are as follows:

[0048] 1. Solar collector cavity

[0049] Most of the surface area of ​​the solar collector cavity 1 is made of quartz glass. The quartz glass is a window made of high-purity fused quartz (SiO2 content >99.9%), and its transmittance is >92% in the 300-2500nm band, ensuring efficient transmission of the entire solar spectrum. The top and bottom of the solar collector cavity 1 can be fixed with the gear ring 5 through high-precision flanges (tolerance ±0.05mm). The flange material can be Inconel 718, which is temperature-resistant to 1100℃, and forms a precise meshing transmission with the planetary gear 4.

[0050] The solar collector cavity 1 is designed to be 9 m in height and 7.5 m in diameter.

[0051] 2. Planetary gear drive module

[0052] (1) Servo motor and sun gear: A 200kW permanent magnet synchronous servo motor 7 is selected, with an adjustable speed of 1-30rpm and short-term overload capability. 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 of <0.01mm³ / (N·m).

[0053] (2) Planetary gear set: Planetary gears 4 (taking 100 sets as an example) are evenly distributed around the sun gear 3, with a revolution to speed ratio of 1:18. The size of the planetary gear system can be adjusted according to actual needs, and motion decoupling is achieved through differential gears; the shaft ends of planetary gears 4 use silicon carbide ceramic bearings (temperature resistant to 1600°C) to ensure low friction operation in high temperature environments.

[0054] The ring gear (internal gear) drives the planetary gear 4, and the internal gear pitch circle diameter is D ring =7.5m (aligned with the outer wall of the solar collector cavity), the planetary gear 4 pitch circle diameter D p =0.2m (consistent with the outer diameter of the heat absorption tube), module m=10mm, meeting the strength requirements, tooth top height coefficient =1, tooth root height coefficient =1.25, then the number of teeth of the inner ring gear is Z ring =750 teeth; number of planetary gear teeth Z p =20 teeth; meshing center distance =3.65m; The addendum circles of adjacent planetary gears must avoid interference and must meet the following requirements: the chord length from the center ≥ the addendum circle diameter + safety backlash; the addendum circle diameter of the planetary gear: ; The safety side clearance is 5mm, then the minimum allowable center distance C min =0.225m; the circumference of the planetary gear distribution circle L≈23.56m, so the number of planetary gears that can be arranged is n≈104.7, and n=100 is selected in this embodiment.

[0055] Center angle of adjacent planetary gears: ;

[0056] The actual center distance chord length , satisfying C≥C min , no interference.

[0057] (3) Dynamic temperature control mechanism: The planetary gear 4 drives the heat absorbing tube 2 to perform a three-dimensional composite motion with an orbital period of 180 seconds and a rotational period of 10 seconds (corresponding to the orbital and rotation ratio), so that the coverage rate of the focused light spot on the surface of the heat absorbing tube 2 is greater than 95%, which greatly eliminates the local overheating caused by static heating. The coverage rate of the traditional system is only about 65%.

[0058] 3. Endothermic reaction integrated components

[0059] (1) Heat absorption tube structure: The outer wall of the heat absorption tube 2 is coated with a multi-layer spectrally selective coating with a thickness of 200nm. The thermal emissivity of this coating at high temperatures of 800-1000℃ is less than 0.15, significantly reducing radiation heat loss by 65%. The heat absorption tube 2 is made of nickel-based alloy Inconel600 / 601, which is heat-resistant to 1150℃ and resistant to carburization and oxidation. Its material density is 8100kg / m 3, the mass of a single heat absorption tube 2 is 1353 kg. 100 heat absorption tubes 2 are used, each heat absorption tube 2 is 7 m long, 200 mm in outer diameter, and 10 mm in wall thickness. The inner wall is processed with a spiral groove 8 with a depth of 5 mm and a pitch of 9 mm, which increases the specific surface area by 2 to 3 times, while enhancing gas turbulence and promoting mass transfer and heat transfer.

[0060] (2) Catalyst bed: filled with Ni / Al2O3 porous foam, with a porosity of 85% and a pore size of 0.5-1mm. Its specific surface area reaches 320m² / g, and the active site density is 3 times higher than that of traditional particle catalysts.

[0061] (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 pipe 2 through a high-temperature rotary sealing joint. The rotary sealing joint is made of graphite / metal composite material with a leakage rate of <0.01%. A vortex distributor is set at the air inlet of the upper gas collecting box to ensure that the flow rate distribution uniformity deviation of the CH4 and CO2 mixture with a molar ratio of 1:1 is <5%.

[0062] The heat absorption tube is verified by detailed gear design. Considering the 5mm safety side clearance and adjacent conditions, a maximum of 104 heat absorption tubes can be arranged along the outer wall of the cavity, retaining 2% redundancy. If 100 heat absorption tubes are selected, the total load is 1326KN.

[0063] The moment of inertia of the heat absorption tube around the central axis (considered as a mass point): ; If the rotation speed is 30rpm, the angular velocity is ; When the start time is 60s, the angular acceleration Starting torque ; then the starting efficiency Considering actual losses, when the transmission efficiency is 90%, Pactual≈348kW;

[0064] When the speed is 30 rpm, the motor power required to drive 100 heat absorption tubes is about 313.2 kW (at the start-up stage). After considering the transmission loss, the actual power required is 348 kW. In steady-state operation, the power is mainly used to overcome friction and air resistance, and the power consumption is about 150-300 kW depending on the working conditions. The power generation per unit area of ​​the mirror field is 200 W / m 2 To achieve this power requirement, a mirror field area of ​​approximately 1500m is required. 2 The waste heat from the molten salt drives the Stirling engine to generate 4.65MWe of electricity, which is used to power the servo motor in the present invention, far exceeding the 348kW power requirement of the gear system.

[0065] 4. Waste heat power generation

[0066] The molten salt heat storage power generation system connected externally in the present invention can use a 60% NaNO3 + 40% KNO3 mixed molten salt with a melting point of 220°C and an operating 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 1.5MW / m 2 The molten salt heat storage power generation system includes a high-temperature tank (optimal operating temperature 565°C) and a low-temperature tank (290°C). The heat storage tank has a diameter of 20m, a height of 10m, and a volume of 2660m 3 , thermal storage capacity 500MWh th The heat storage and release duration is 15 hours; the temperature difference of the molten salt waste heat is 290-350°C, which can drive the Stirling engine to generate electricity, with a thermoelectric conversion efficiency of 16%, corresponding to the generated electricity of 4.65MWe. The generated electricity is supplied to the servo motor 7 in the present invention to form a closed-loop energy utilization; the surplus electricity is incorporated into the power grid or used by other equipment, such as control systems, pumps and valves.

[0067] In this embodiment, the power generation capacity of the tower power station is matched to 10MW. In actual projects, the mirror area of ​​the tower system is usually tens of thousands to hundreds of thousands of square meters (for example, the total lighting area of ​​the 10MW molten salt tower solar thermal power station in Dunhuang is 175,000m 2 ), far exceeding demand, and the power supply is fully redundant.

[0068] 2. Compatibility of the heat collection temperature in the solar thermal reactor with the methane reforming reaction

[0069] 1. Methane reforming reaction model assumptions

[0070] The present invention uses FLUENT software in ANSYS for numerical simulation. In the process of studying methane reforming hydrogen production under concentrated irradiation, the software's multi-component transport model, porous medium model, energy exchange model, radiation heat transfer model, and chemical reaction model are used for simulation calculations. Since the calculation area of ​​the heat absorber used in the present invention is axisymmetric, it can be simplified to a two-dimensional model. During the simulation process, the gas inlet adopts a mass flow inlet. The reaction process of this simulation study is assumed as follows:

[0071] (1) The mixed gas is an incompressible ideal gas and is mixed evenly before entering the reactor;

[0072] (2) The catalyst is evenly distributed in the heat absorbing tube, so the reaction occurs in the heat absorbing tube, and the reactants react on the surface of the heat absorbing tube;

[0073] (3) Ignore radiation heat transfer during the reaction process;

[0074] (4) The catalytic reaction of CO2 reforming to CH4 only considers one-step overall reaction.

[0075] Methane conversion rate:

[0076]

[0077] Where: ——Methane conversion rate, %;

[0078] ——methane mole fraction at the reactor inlet;

[0079] ——Methane mole fraction at the reactor outlet.

[0080] 2. Simulation Setup and Result Analysis

[0081] The present invention adopts a two-dimensional axisymmetric steady-state 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 a polynomial fitting is used for each individual component to consider the influence of temperature on the specific heat capacity. The inlet is the velocity inlet boundary, the outlet is the pressure outlet boundary, and the tube wall is the no-slip constant wall temperature boundary (T wall = 800ºC), the reaction area is a simple isotropic porous medium, and the volume reaction is used to consider the influence of catalyst and structural parameters on the reaction in the tube. The computational model uses quadrilateral meshing, and the near-wall area and porous medium area are densified. The pressure-velocity coupling adopts the Simple algorithm, the pressure discretization is Standard, and all other control equations are discretized using the second-order upwind scheme. The residual of the energy equation is ≤10 -8 , the residuals of other control equations are ≤10 -6 .

[0082] The numerical model uses a small-scale model, a smooth quartz tube with an inner diameter of d = 0.01m, L = 0.7m, and a porous medium length L catalyst =0.4m, Ni / Al2O3 is used as the reaction catalyst; the reaction gas of CH4 / CO2=1:1 enters from one end of the heat absorption tube with an inflow velocity of 0.2m / s and flows out from the other end after the reaction; in the numerical model, the constant wall temperature approximation is used to treat the thermal boundary of the tube wall, and the effect of the tube wall thickness on heat transfer is ignored; Table 1 shows the numerical simulation results of the shear conversion rate under different working conditions.

[0083] Table 1 Methane conversion under different reaction conditions

[0084]

[0085] In Table 1, T wall (K): Temperature of the heat absorbing tube wall; T in (K): Inlet temperature of heat absorption tube; S / V (m -1 ): surface-to-volume ratio; λ catalys Thermal conductivity of porous media; CH4in : molar fraction of methane at the inlet of the heat absorption tube; CH 4out : mole fraction of methane at the outlet of the heat absorption tube; X CH4 (%): Methane conversion rate.

[0086] The fluid inlet temperature is room temperature 25℃ and preheated to 600℃, and the wall temperature is 600℃, 800℃, and 1000℃. The effects of inlet temperature and heating temperature on thermochemical reaction are studied. Figure 5 As shown, the initial reaction rate is very high, the methane mass fraction decreases rapidly, and the conversion rate exceeds 95% within the catalytic section length. The curves can be divided into a 25°C curve family and a 600°C curve family. The curves at the same inlet temperature are close, while the curves at different inlet temperatures are far apart. At the same inlet temperature, as the wall temperature increases, the reaction rate accelerates, the reaction proceeds faster, and the methane conversion rate increases.

[0087] The inlet fluid is preheated to T in When the temperature is 600℃ and the wall temperature is 1000℃, the effect of flow rate on the thermochemical reaction is studied under different inlet flow rates; Figure 6 As shown in the figure, it is found that the effect of inlet flow rate on the reaction is relatively complex, which is mainly reflected in three aspects: 1. Residence time. Increasing the flow rate shortens the residence time of the reactants, which is not conducive to sufficient reaction; 2. Reaction temperature. Too fast a flow rate will lead to a low temperature in the center of the reaction tube, which is not conducive to the reaction; 3. Local concentration of reactants. When the tube diameter remains unchanged, increasing the flow rate can increase the concentration of reactants accordingly, 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 From the analysis, we can see that changing the wall temperature has little effect on the conversion rate at a low flow rate, but at a higher flow rate, increasing the wall temperature can significantly increase the conversion rate.

[0088] The effects of pipe diameter and inlet mass flow rate on the thermochemical reaction were studied under the conditions of preheating the inlet fluid to 600℃, the wall temperature to 1000℃ and different inlet mass flow rates; Figure 7 As shown in the figure, the combined effect of the reaction tube diameter and mass flow rate on the reaction is more complicated, and the analysis is as follows: observing the two curves, the trend is to increase first and then decrease. With the increase of the tube diameter, the temperature distribution becomes more uneven, and the center temperature is lower, which is not conducive to the reaction; but the speed gradually decreases. According to the above analysis, a small speed is conducive to improving the conversion rate. The trend of the curve is the result of the combined effect of the two.

[0089] Comparing the two curves, the conversion rate is higher for small flow rate under small diameter, and higher for large flow rate under large diameter. This is because under small diameter, the velocity is relatively high, and factors 1 and 2 that hinder the reaction play a major role, so the conversion rate is higher for the one with lower velocity; while under large diameter, the velocity is very low, and factor 3 that promotes the reaction plays a major role, so the conversion rate is higher for the one with higher velocity.

[0090] 3. Simulation results support the feasibility of the present invention

[0091] (1) Matching of high temperature stability and reaction efficiency

[0092] Simulation results show that when the wall temperature is 1000°C (1273K) and the inlet is preheated to 600°C (873K), the methane conversion rate can reach 99.54%, proving that under high-temperature conditions, the absorber tube can achieve near-complete conversion; the tower solar collector in this embodiment can provide a stable heat source of 800-1000°C (verified previously), which is highly matched with the optimal reaction temperature (1000°C) in the simulation, verifying the synergy between solar heating and the absorber tube design; in the simulation, temperature uniformity is achieved through constant wall temperature boundary conditions, and the rotation and revolution of the absorber tube driven by the planetary gear train in the present invention can further enhance heat transfer, avoid local overheating or cold zones, and ensure catalytic efficiency.

[0093] (2) Controllability of flow rate and residence time

[0094] Simulations show that within the flow rate range of 0.1 to 1 m / s, a methane conversion rate of 90% to 97% can be maintained by adjusting the wall temperature (800 to 1000°C), demonstrating the heat absorber's strong adaptability to flow fluctuations. The servo motor in the present invention can indirectly control the rotation speed of the heat absorber by adjusting the sun gear speed, thereby optimizing the gas residence time and flow velocity distribution (e.g., extending the residence time at low speeds and enhancing turbulent mixing at high speeds).

[0095] (3) Structural scalability and engineering adaptability

[0096] When the tube diameter in the simulation was expanded from 0.01 m to 0.1 m, the conversion rate could still be maintained at >90% by adjusting the inlet mass flow rate (0.1-0.2 g / s), indicating that the heat absorber design has good scalability. The large-scale design of the present invention uses a ring array of 100 heat absorber tubes, combined with the uniform distribution characteristics of the porous medium catalyst in the simulation, to ensure consistent reaction efficiency in each tube within the large-scale reactor.

[0097] The above supplementary materials fully verify the feasibility and technical advantages of the present invention by combining actual engineering parameters with simulation.

[0098] The working principle of the present invention is as follows:

[0099] like Figure 4As shown, the external heliostat field reflects sunlight into the solar collector cavity 1, focusing it to form a high-density light spot (energy density > 1000 W / m²). The light spot penetrates the highly transparent quartz window and is absorbed by the spectrally selective coating on the outer surface of the heat absorber tube 2, rapidly heating it to above 850°C. The servo motor 7 drives the sun gear 3 to rotate, driving the planetary gears 4 to revolve and rotate. The heat absorber tube 2 rotates synchronously with the planetary gear train, ensuring that the focused light spot fully covers the tube surface (coverage rate > 95%), and the axial temperature gradient of the heat absorber tube 2 is reduced to <10°C / m. The CH4 and CO2 mixture inside the heat absorber tube 2 enters the heat absorber tube 2 evenly through the vortex distributor of the upper gas collecting box. 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 more than 90%. The H2 and CO generated by the methane reforming reaction are output through the rotary sealing joint of the lower gas collecting box; the molten salt circulating in the hollow tube 6 absorbs heat to supply the molten salt thermal storage power generation system to maintain continuous power generation operation. The waste heat of the reaction drives the external Stirling engine to convert the waste heat of the molten salt into electrical energy (efficiency 16%), which is supplied to the servo motor 7 to form an energy self-circulation.

Claims

1. A planetary gear system solar thermal 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 fixed to both ends of the heat absorbing tube (2), and the planetary gears (4) are meshed with a gear ring (5), and the sun gears (3) are fixed to both ends of the hollow tube (6), and the sun gears (3) are meshed with the planetary gears (4). The sun gear (3) is 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 gears (4) to rotate inside the gear ring (5); the outer surface of the heat absorbing tube (2) is coated with a spectral selective coating, and the spectral selective coating comprises, from the outside to the inside, an infrared reflection layer, an absorption layer, and an anti-reflection layer, wherein the infrared reflection layer material is tungsten, the absorption layer material is HfNbTaTiZrNO, and 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.

2. The solar thermal reactor according to claim 1, wherein: The inner wall of the heat absorption tube (2) is provided with a gear-shaped groove (8) or a spiral groove (9); 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).

3. The solar thermal reactor according to claim 1, wherein: 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.

4. The solar thermal reactor according to claim 1, wherein: 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 gear (3).

5. The solar thermal 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).

6. The solar thermal reactor according to claim 1, wherein: The number of the heat absorbing tubes (2) is N, where N is greater than or equal to 4. The plurality of planetary gears (4) are evenly distributed around the circumference of the sun gear (3) as the axis. The inner diameter of the heat absorbing tube (2) is 0.01 m to 0.1 m.

7. The solar thermal reactor according to claim 1, wherein: The wheel shaft end of the planetary wheel (4) adopts a silicon carbide ceramic bearing.

8. The solar thermal reactor according to claim 3, wherein: The solar heat collector cavity (1) is made of high-purity fused quartz.

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