Foamed ceramic filling type thermochemical reactor with bionic leaf structure

Abstract

The invention discloses a foamed ceramic filling type thermochemical reactor with a bionic leaf structure, and belongs to the field of solar thermochemical energy storage. The device comprises a reactor cavity, a foamed ceramic matrix, a shell, a light incidence window, an air inlet pipe and an air outlet pipe, the reactor cavity is installed in the shell, the light incidence window is formed in the top of the reactor cavity, the foamed ceramic matrix is arranged in the reactor cavity, and the air inlet pipe communicated with the outside is arranged at the top of the reactor cavity; a gas outlet pipe communicated with the outside is arranged at the bottom of the reactor cavity, the problems of large radiation heat loss, large temperature gradient and energy-flow mismatching generally existing in an existing reactor are solved, and the reactor cavity following the principle that bullets penetrate through an object to release energy to the maximum degree is provided. And meanwhile, the foamed ceramic matrix with a bionic leaf type foam porous structure is filled, so that more light rays can enter the reactor cavity and are efficiently absorbed, transmitted and converted.

Description

Technical Field

[0001] The invention relates to a foam ceramic filled thermochemical reactor with a bionic leaf structure, belonging to the field of solar thermochemical energy storage. Background Art

[0002] Solar thermochemical reactors can significantly affect the performance of methane reforming. The principle is that according to the mechanism of solar heat transfer to the reaction fluid, the reactor can be divided into two categories: indirect reactors and direct reactors. Among them, the most direct and effective method is to directly heat the fluid by concentrating sunlight, thereby reducing heat losses in the intermediate process. Direct reactors usually reach temperatures above 1000K due to the influence of highly concentrated solar radiation, which places higher requirements on the reactor. The direct reactor based on ceramic foam structure is the most reported reactor at present, and it has received increasing attention due to its better heat and mass transfer performance.

[0003] Highly concentrated solar radiation is absorbed by the solid medium in the foam ceramic filled solar thermochemical reactor and converted into high-temperature thermal energy, which in turn drives the thermochemical reaction to convert solar energy into the chemical energy of the fuel. Since the operating temperature in the solar thermochemical reactor is relatively high, which can reach about 1000K, radiation heat exchange is the main form of energy transmission in the high-temperature photothermal conversion of solar energy. Therefore, the radiation transmission process in the reactor is the primary factor affecting the spatial distribution of temperature and the energy conversion efficiency in the high-temperature thermochemical reactor. However, in the existing high-temperature photo-thermal-chemical conversion process, the radiation field is out of balance in the spatial direction, resulting in the spatial distribution of temperature in the high-temperature solar reactor not matching the temperature required for thermochemical conversion, and it is impossible to establish an effective regulation method to effectively improve the energy conversion efficiency.

[0004] The geometric structure of the reactor affects the absorption, transmission, conversion and flow field distribution of solar radiation energy. At the same time, the geometric structure of the porous foam ceramic matrix has an important influence on physical fields such as radiation field and temperature field. Both affect the overall energy conversion efficiency of the system. Therefore, it is necessary to optimize the design of the foam ceramic reactor cavity and improve the solar-chemical energy conversion efficiency by regulating the radiation transmission characteristics.

[0005] Therefore, it is urgent to propose a foam ceramic filled thermochemical reactor with a bionic leaf structure to solve the above technical problems. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of large radiation heat loss, large temperature gradient and energy-flow mismatch commonly found in existing reactors. A brief summary of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this summary is not an exhaustive summary of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention.

[0007] The technical solution of the present invention:

[0008] A foam ceramic filled thermochemical reactor with a bionic leaf structure comprises a reactor cavity, a foam ceramic matrix, an outer shell, a light incident window, an air inlet pipe and an air outlet pipe, wherein the reactor cavity is installed inside the outer shell, a light incident window is provided on the top of the reactor cavity, a foam ceramic matrix is ​​provided inside the reactor cavity, an air inlet pipe connected to the outside is provided on the top of the reactor cavity, and an air outlet pipe connected to the outside is provided on the bottom of the reactor cavity, highly concentrated solar radiation enters the reactor cavity through the light incident window, is absorbed by the foam ceramic matrix, and is subjected to thermal radiation transmission to reach a reaction temperature, gas enters the reactor cavity from the air inlet pipe, chemical reaction occurs under the action of the reaction temperature, and the reacted gas is discharged from the air outlet pipe, the foam ceramic matrix is ​​a foam porous structure, and the foam porous structure is a bionic leaf-shaped foam porous structure.

[0009] Preferably, the reactor cavity is a light funnel structure.

[0010] Preferably, the light incident window is a high-transmittance quartz glass window.

[0011] Preferably, the air inlet pipes are arranged on the left and right sides of the reactor cavity, enter the reactor cavity from both sides thereof, and form an annular counter-flow inside the reactor cavity.

[0012] The present invention has the following beneficial effects:

[0013] 1. The present invention proposes a reactor cavity that follows the principle of maximizing the energy released when a bullet penetrates an object, and is filled with a foam ceramic matrix with a bionic leaf-shaped foam porous structure, so that more light can enter the reactor cavity and be efficiently absorbed, transmitted and converted, providing a new technology and method for solving the problems of large radiation heat loss, large temperature gradient, and energy-flow mismatch in the reactor;

[0014] 2. The present invention enables the heat-absorbing front end of the reactor chamber to have a strong solar absorption rate and a strong forward scattering effect, as well as a strong backscattering effect at the outlet tail end of the reactor chamber, thereby achieving an ideal coordination between the temperature field distribution in the reactor chamber and the thermodynamic temperature requirements, effectively enhancing the absorption, transmission and conversion of incident sunlight, and also having a positive impact on improving the thermochemical performance of the foam ceramic reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a foam ceramic filled thermochemical reactor with a bionic leaf structure;

[0016] Figure 2 is a schematic diagram of the structure of the leaf level hole structure according to a specific embodiment of the present invention;

[0017] Figure 3 is a schematic structural diagram of the foam ceramic matrix according to a specific embodiment of the present invention;

[0018] Figure 4 is a structural schematic diagram of the bionic leaf-shaped foam porous structure according to a specific embodiment of the present invention;

[0019] Figure 5 Schematic diagram of the effect of pore structure on thermochemical properties in Example 2 of the present invention, wherein (a) is a curve diagram of the effect of foam ceramic pore structure on methane conversion rate, and (b) is a curve diagram of thermal performance change when the porosity is 0.9;

[0020] Figure 6 Schematic diagram of the effect of temperature on pore structure in Example 2 of the present invention, wherein (a) is an effect curve diagram of porosity, and (b) is an effect curve diagram of pore size;

[0021] Figure 7 Schematic diagram of the effect of porosity on the mole fraction of components in Example 2 of the present invention, wherein (a) is a schematic diagram of the effect of small porosity structure on the mole fraction of components, and (b) is a schematic diagram of the effect of large porosity structure on the mole fraction of components;

[0022] Figure 8 Schematic diagram of the effect of the double-layer graded porosity on the thermochemical performance in Example 2 of the present invention, wherein (a) is the methane conversion rate, and (b) is the mole fraction along the axis;

[0023] Fig. 9 Schematic diagram of the effect of the double-layer graded pore size on the thermochemical performance in Example 2 of the present invention, wherein (a) is the methane conversion rate, and (b) is the mole fraction along the axis;

[0024] Fig.10 Schematic diagram of the effect of multi-layer graded pore size on methane conversion rate in Example 2 of the present invention, wherein d1=1.0 in (a), d1=2.0 in (b), d1=3.0 in (c), d1=4.0 in (d), and d1=5.0 in (e);

[0025] Fig.11The methane conversion rate and solar-to-chemical energy storage conversion efficiency of different structures in the second embodiment of the present invention are shown, wherein (a) is a traditional structure and (b) is a foam ceramic matrix structure in the second embodiment of the present invention.

[0026] In the figure: 1-reactor cavity, 2-foam ceramic matrix, 3-insulation layer, 4-shell, 5-light incident window, 6-inlet pipe, 7-outlet pipe, 8-highly concentrated solar radiation. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is described below by the specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0028] The connection mentioned in the present invention is divided into fixed connection and detachable connection. The fixed connection is a non-detachable connection including but not limited to conventional fixed connection methods such as folding connection, rivet connection, bonding connection and welding connection. The detachable connection includes but not limited to conventional detachable methods such as threaded connection, snap connection, pin connection and hinge connection. When the specific connection method is not clearly defined, it is assumed that at least one connection method can always be found in the existing connection methods to achieve the function. Those skilled in the art can choose according to their needs. For example: a fixed connection is selected as a welding connection, and a detachable connection is selected as a hinge connection.

[0029] Embodiment 1: Combination Figure 1-Figure 11 The present embodiment is described. A foam ceramic filled thermochemical reactor with a bionic leaf structure in the present embodiment comprises a reactor cavity 1, a foam ceramic matrix 2, a heat preservation layer 3, a shell 4, a light incident window 5, an air inlet pipe 6 and an air outlet pipe 7. The shell 4 is provided with the reactor cavity 1, the heat preservation layer 3 is filled between the reactor cavity 1 and the shell 4, the top of the reactor cavity 1 is provided with a light incident window 5, the inside of the reactor cavity 1 is provided with a foam ceramic matrix 2, the top of the reactor cavity 1 is provided with an air inlet pipe 6 connected to the outside, and the bottom of the reactor cavity 1 is provided with an air outlet pipe 7 connected to the outside;

[0030] The basic working principle of this embodiment is as follows Figure 1 As shown, the solar-driven methane reforming process is mainly divided into three stages: absorption, transfer and conversion. Specifically, highly concentrated solar radiation 8 enters the reactor cavity 1 through the light incident window 5, is absorbed by the foam ceramic matrix 2, and is thermally transmitted under the multiple scattering of the foam ceramic matrix 2 to reach the reaction temperature. The gas enters the reactor cavity 1 from the inlet pipe 6, and a chemical reaction occurs under the action of the reaction temperature to convert solar energy into chemical energy. The reacted gas is discharged from the outlet pipe 7;

[0031] The foam ceramic matrix 2 is used to load the catalyst to absorb, transmit and transform the highly concentrated solar radiation 8. The foam ceramic matrix 2 is a foam porous structure, which is a bionic leaf-shaped foam porous structure. A partial structure thereof is shown in FIG. Figure 3 The bionic leaf-shaped foam porous structure has a unique hierarchical pore structure, which has certain advantages in increasing the optical penetration depth and reducing the occurrence of side reactions, and optimizes the thermochemical performance by expanding the high-temperature area.

[0032] The bionic leaf-shaped foam porous structure is based on the principle of minimizing Gibbs free energy and is inspired by the hierarchical structure of bionic leaves. It is optimized from the perspective of enhancing the front-end forward scattering and rear-end backward scattering capabilities of the porous structure. Figure 2 As shown, leaves have a unique layered structure, which can manage and regulate photons well, creating conditions for efficient solar energy utilization. Specifically, the bionic leaf-shaped foam porous structure of this embodiment imitates the palisade cells in the leaves to guide the transmission of light, and at the same time imitates the cavities between the palisade cells in the leaves to strongly scatter light, such as Figure 4 As shown, the light absorption efficiency is improved. In addition, the hierarchical porous structure of leaves, as a highly efficient nutrient transport system selected by nature, has unique advantages in material transport and energy transfer. The foam ceramic matrix 2 of this embodiment is inspired by the hierarchical pore structure of leaves, and introduces a bionic leaf-shaped foam porous structure to regulate radiation transmission characteristics, meet the dual requirements of efficient light capture and rapid diffusion of components in solar thermal chemical conversion, and optimize the temperature field in the reactor cavity 1 to achieve efficient conversion of solar energy to chemical energy.

[0033] Since the front end of the reactor cavity 1 is directly irradiated by the highly concentrated solar radiation 8, the uneven radiation distribution leads to a large temperature gradient. A foam ceramic matrix 2 with a bionic leaf-shaped foam porous structure is proposed to meet the dual requirements of efficient light capture and rapid diffusion of components in solar thermochemical conversion. The multiple scattering and absorption of photons are regulated by a combination of three-dimensionally connected non-uniform channels, so that the heat-absorbing front end of the foam ceramic matrix 2 has a strong solar light absorptivity and a strong forward scattering effect, as well as a strong backscattering effect at the outlet tail of the foam ceramic matrix 2, achieving an ideal synergy between the temperature field distribution in the reactor and the thermodynamic temperature (obtained by the Gibbs free energy minimization method, which is ~1050K), effectively enhancing the absorption, transmission, and conversion of incident sunlight. The front porosity of the bionic leaf-shaped foam porous structure is 60%, and the rear porosity is 45%.

[0034] The reactor cavity 1 is a light funnel structure, which is used for the flow of methane gas, the guidance of radiation light, and the mounting of the foam ceramic matrix 2 .

[0035] The thermal insulation layer 3 is an alumina lightweight fiber layer, and alumina lightweight fibers with low thermal conductivity are used to reduce heat loss.

[0036] The housing 4 is made of stainless steel 316L with a polished surface.

[0037] The light incident window 5 is a high light transmittance quartz glass window.

[0038] The air inlet pipe 6 is arranged on the left and right sides of the reactor cavity 1, enters the reactor cavity 1 from both sides, and forms an annular counter-flow inside, adopting a two-side annular air inlet method to uniform the airflow. The air outlet pipe 7 is used for the gas to flow out after the reaction. The highly concentrated solar radiation 8 is used to provide the energy required for the methane reforming reaction.

[0039] Embodiment 2: Combination Figure 1-Figure 11 This embodiment is described. In this embodiment, a foam ceramic filled thermochemical reactor with a bionic leaf structure is used. When the size of the "light funnel" at the front end of the thermochemical reactor and the cavity size are determined in the early stage, the size parameters of the foam ceramic matrix 2 are studied and determined. The specific steps are as follows:

[0040] Step 1, designing the size of the foam ceramic substrate 2;

[0041] The foam ceramic substrate 2 is a cylinder with a high-porosity porous structure, and its diameter is defined as D and its length is defined as L.

[0042] The axial line is the central axis along the length direction, and the radial line is defined as the line along the radius direction. The geometric structure parameters of the foam ceramic are listed in Table 1-1. As shown in Table 1-1, a total of 9 working conditions of foam ceramics were optimized by combination to determine the optimal foam ceramic geometry.

[0043] Table 1-1 Foam ceramic geometric structure parameters

[0044]

[0045] By comparing the energy absorbed by the reactor, methane conversion rate, conversion rate per unit volume, methane conversion rate per unit volume, mole fraction distribution of each component, and reaction temperature parameters of the reaction area, foam ceramics with D = 60 mm, L = 60 mm were finally selected as the subsequent research object.

[0046] Step 2, designing the foam ceramic pore structure of the foam ceramic substrate 2;

[0047] The inlet ratio of methane and carbon dioxide was set to 2:3 to study the effect of pore structure on thermochemical properties. Figure 5 As shown in (a), a larger porosity is beneficial to the methane dry reforming reaction. Figure 5As shown in (b), when the porosity is 0.9, the methane conversion rate reaches the peak when d = 1.5 mm.

[0048] Temperature is a very important factor affecting the progress of chemical reactions. Figure 6 The solid temperature and fluid temperature of the reaction zone along the axial direction (R=0mm) under different pore structures are given.

[0049] according to Figure 6 As shown in (a), under the same pore size, the solid temperature and fluid temperature of the large porosity structure are generally higher than those of the small porosity structure. The porosity is proportional to the optical penetration depth and inversely proportional to the momentum dissipation. As the porosity increases, the high-temperature area of ​​the fluid moves backward. The difference between the outlet temperature and the peak temperature of the fluid is reduced by 37.5K, the temperature gradient is smaller, and the uniformity of the temperature field is improved.

[0050] according to Figure 6 As shown in (b), with the increase of pore size, the solid temperature and fluid temperature both decrease to varying degrees. The smaller pore size structure has more sufficient convective heat transfer, making the temperature difference between the solid and fluid phases smaller. The methane dry reforming reaction mainly occurs at the front end of the reactor. Therefore, the small pore size promotes the conversion of methane due to the higher temperature at the front end. In addition, the larger pore size has a lower convective heat transfer coefficient, resulting in a lower fluid temperature at the front end of the reaction area, but because of the larger optical penetration depth, the temperature at the back end is higher, resulting in the phenomenon of backward shift of the high temperature area.

[0051] Experimental verification shows that the methane dry reforming reaction is mainly concentrated in the first half of the reaction area. Figure 7 The effect of porosity on the molar fraction of the components. The small porosity structure reacts better at the front end of the reaction area due to the higher fluid temperature. However, as the length L increases, the advantages of the large porosity structure gradually emerge. Compared with the small porosity structure, the molar fractions of hydrogen and carbon monoxide at the outlet of the larger porosity increased by 4.5% and 3.7%, respectively.

[0052] Step 3, designing the hierarchical pore structure of the foam ceramic matrix 2;

[0053] Step 3.1, designing a double-layer hierarchical porosity porous structure;

[0054] When φ1 is in a porous structure with large porosity, the change of φ2 has a significant effect on the thermochemical performance. The reaction rate of the reactor with a filling grade porosity structure shows certain advantages after L>20mm, but its overall contribution to the improvement of methane conversion rate is limited.

[0055] Step 3.2, designing a double-layer hierarchical pore size porous structure;

[0056] Under the premise that the foam ceramic has a large porosity to ensure a good optical penetration depth, the hierarchical porous structure with increased pore size has a higher conversion rate than the hierarchical porous structure with reduced pore size. The small pore size has the characteristics of large surface area and strong disturbance, which is conducive to the interaction between the reactants and the catalyst and promotes the chemical reaction. The large pore size allows the product to flow to the reactor outlet as quickly as possible, reducing the occurrence of side reactions.

[0057] like Fig. 9 As shown in (b), the smaller pore structure has more complete convective heat transfer, which makes the temperature difference between the solid and fluid phases smaller. The larger pore size has a larger optical penetration depth, which makes the rear temperature higher, resulting in the backward shift of the high-temperature area. The larger pore size at the front end of the reactor is not conducive to the convective heat transfer and radiation heat transfer between the fluid and the solid. Compared with the reactor with a single-layer porous structure, the methane conversion rate of the double-layer graded pore porous reactor is increased by 3.9%.

[0058] Step 3.3, design a multi-layer hierarchical pore size porous structure

[0059] The principle of the multi-layer hierarchical pore structure is to construct a double-layer structure along the radial direction at the front end of the foam ceramic to achieve a hierarchical pore structure in both the length and radial directions.

[0060] like Fig.10 As shown in the figure, since d1 is located at the front axis of the foam ceramic, it is the position that receives the most solar radiation and is the core position that affects the thermochemical performance. The methane conversion rate is significantly higher under the multi-layer aperture combination of d1 = 2.0 mm, and the maximum methane conversion rate is 85.0%. When d1 and d2 are constant, when d3 is greater than d1 and d2, the methane conversion rate is higher. Compared with the reactor with a single-layer porous structure, the methane conversion rate of the multi-layer graded aperture porous reactor is increased by 4.2%.

[0061] Step 4, regulating the radiation characteristics of the bionic leaf-shaped foam porous structure of the foam ceramic substrate 2;

[0062] The hierarchical porous structure of leaves, as a naturally selected efficient nutrient transport system, has unique advantages in material transport and energy transfer. Inspired by the hierarchical pore structure of leaves, the present invention proposes an innovative three-dimensional connected structure in the internal structure of the foam matrix, and utilizes a combination of three-dimensional connected non-uniform channels to regulate the multiple scattering and absorption of photons, so that the heat-absorbing front end of the reactor has a strong solar absorption rate and a strong forward scattering effect, as well as a strong backscattering effect at the outlet tail of the reactor, thereby achieving an ideal synergy between the temperature field distribution in the reactor and the thermodynamic temperature requirements, and effectively enhancing the absorption, transmission and conversion of incident sunlight.

[0063] Fig.11(b) is a comparison of the methane conversion rate and solar-to-chemical energy conversion efficiency of the bionic structure and the traditional structure. Compared with the traditional structure, the designed bionic structure has a maximum increase of 6.6% in methane conversion rate.

[0064] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be arranged and combined, and those skilled in the art can exhaust all possibilities based on the mathematical knowledge of arrangement and combination. Therefore, the present invention will no longer describe the technical solutions after arrangement and combination one by one, but it should be understood that the technical solutions after arrangement and combination have been disclosed by the present invention.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A foam ceramic filled thermochemical reactor with a bionic leaf structure, characterized in that: The invention comprises a reactor cavity (1), a foam ceramic matrix (2), an outer shell (4), a light incident window (5), an air inlet pipe (6) and an air outlet pipe (7); the reactor cavity (1) is installed inside the outer shell (4); a light incident window (5) is arranged at the top of the reactor cavity (1); a foam ceramic matrix (2) is arranged inside the reactor cavity (1); an air inlet pipe (6) connected to the outside is arranged at the top of the reactor cavity (1); an air outlet pipe (7) connected to the outside is arranged at the bottom of the reactor cavity (1); highly concentrated solar radiation (8) enters the reactor cavity (1) through the light incident window (5), is absorbed by the foam ceramic matrix (2), and is subjected to heat radiation transmission to reach a reaction temperature; gas enters the reactor cavity (1) from the air inlet pipe (6), undergoes a chemical reaction under the action of the reaction temperature, and the reacted gas is discharged from the air outlet pipe (7); the foam ceramic matrix (2) is a foam porous structure, which is a bionic leaf-shaped foam porous structure.

2. The foam ceramic filled thermochemical reactor with a bionic leaf structure according to claim 1, characterized in that: The reactor cavity (1) is a light funnel structure.

3. The foam ceramic filled thermochemical reactor with a bionic leaf structure according to claim 1, characterized in that: The light incident window (5) is a high-light-transmittance quartz glass window.

4. The foam ceramic filled thermochemical reactor with a bionic leaf structure according to claim 1, characterized in that: The air inlet pipe (6) is arranged on the left and right sides of the reactor cavity (1), enters the interior of the reactor cavity (1) from both sides, and forms an annular counter-flow inside.

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