Uniform heating solar reactor combining energy flux distribution and absorber coating design

Abstract

The uniform heating solar reactor designed by combining energy flow distribution and absorption coating belongs to the field of solar thermal utilization. The internal temperature of the existing solar reactor is uneven, resulting in low reaction efficiency. The sunlight concentrated by the dish-type solar concentrator is partially irradiated to the surface of the foam ceramic through the quartz window, and the other part passes through the pores in the foam ceramic and is finally received by the ellipsoidal graphite sheet coated with the absorption coating. After absorbing the heat, the ellipsoidal graphite sheet heats the outer spherical surface of the foam ceramic adjacent to the ellipsoidal graphite sheet through heat conduction, so that the temperature of the foam ceramic is uniform; according to the energy flow distribution results of the numerical simulation of computational fluid dynamics, the foam ceramic adopts a double-layer nested "double ellipsoidal surface" geometric structure with long and short axes perpendicular to each other to alleviate the heat concentration in the front area and enhance the uniformity of the circumferential temperature distribution; the raw gas inlet and gas product outlet are respectively opened on the upper and bottom of the ellipsoidal shell, and the raw gas inlet faces the quartz window. It is used to improve the reaction efficiency.

Description

Technical Field

[0001] The invention relates to a uniform heating type solar energy reactor and belongs to the field of solar energy thermal utilization. Background Art

[0002] Solar reactors (collectors) are usually driven by concentrated solar energy. They can convert solar energy into chemical energy (or thermal energy) under low-carbon or zero-carbon conditions and store or directly utilize it. They are an efficient and clean way to utilize renewable energy. According to the heating method of concentrated solar energy, common solar reactors can be divided into two types: direct heating and indirect heating: the front end of the direct heating reactor is usually equipped with quartz glass with good transmittance, which allows concentrated solar energy to directly irradiate the inside of the reactor through the quartz window while ensuring airtightness and heating the reaction medium; the reaction medium in the indirect heating reactor will not be directly exposed to solar energy, but the heat is indirectly transferred by the heat-absorbing material located on the focusing target plane outside the reactor, and at the same time, the raw gas or working fluid forms a flow in the reaction medium to take away the heat. In comparison, due to the large amount of external heat dissipation and internal heat transfer losses in the indirect heating process, the thermal efficiency of the direct heating reactor will be relatively high, but there are also two key factors that limit energy efficiency: first, the reaction medium in the reactor that has been heated to a high temperature will dissipate energy outward through the quartz window in the form of thermal radiation, and the thermal radiation loss will increase significantly with the increase in temperature; second, the target plane of concentrated solar energy is usually located at the front end of the reactor or the medium, which can easily form a local high-temperature overheating area and produce a large temperature gradient in the entire reaction area. This uneven temperature field will not only aggravate the external radiation heat loss of the quartz window, but more importantly, it will have a strong negative impact on the internal chemical reaction, thereby reducing the energy efficiency of the entire reactor.

[0003] With the development of modern computational fluid dynamics, the radiation transmission process, fluid flow process, gas-solid convection heat transfer process, and chemical reaction process inside the solar reactor can be intuitively displayed. If the geometric shape of the reaction medium can be redesigned in combination with the energy flow distribution in the reaction area, the unevenness of the temperature field distribution can be reduced to a great extent. On the other hand, using the optical properties of the reaction medium and the absorption coating to regulate the transmission and absorption process of solar radiation energy can further alleviate the heat concentration phenomenon in the direct heating process of concentrated solar energy, and reheat the lower temperature area, thereby improving the uniformity of the entire temperature field and improving the energy conversion efficiency and reaction rate of the reactor. Summary of the invention

[0004] The purpose of the present invention is to solve the problem of uneven internal temperature of existing solar reactors, which leads to low reaction rate in the solar reactor, and proposes a uniform heating solar reactor combining energy flow distribution and absorption coating design.

[0005] A uniform heating solar reactor designed by combining energy flow distribution with an absorption coating, the reactor comprising a dish-type solar concentrator, a quartz window, an ellipsoidal shell, an ellipsoidal graphite sheet, an absorption coating and foam ceramics;

[0006] The foam ceramic is a ceramic body having a plurality of through-hole foam structures, the surface of the foam ceramic is coated with a catalytic material, and the foam ceramic is in a semi-ellipsoidal shape;

[0007] The outer spherical surface of the foam ceramic is coated with an absorption coating, the ellipsoidal graphite sheet is wrapped on the outer surface of the absorption coating, the ellipsoidal shell is wrapped on the outer surface of the ellipsoidal graphite sheet, and the axial direction of the ellipsoidal shell is consistent with the long axis direction of the semi-ellipsoidal foam ceramic;

[0008] The quartz window covers the opening of the ellipsoidal shell, and a semi-ellipsoidal groove is dug on the foam ceramic close to the quartz window, and the long axis of the semi-ellipsoidal groove intersects the long axis of the foam ceramic perpendicularly;

[0009] The dish solar concentrator is located outside the quartz window. The dish solar concentrator is used to concentrate sunlight. A portion of the concentrated sunlight passes through the quartz window and irradiates the surface of the foam ceramic. The other portion passes through the pores in the foam ceramic and is finally received by the ellipsoidal graphite sheet coated with an absorption coating. The ellipsoidal graphite sheet absorbs the heat of the sunlight and heats the outer spherical surface of the foam ceramic adjacent to the ellipsoidal graphite sheet through heat conduction, thereby making the temperature of the foam ceramic uniform.

[0010] A plurality of raw gas inlets are arranged on the ellipsoidal shell, and all of the raw gas inlets face the quartz window; a gas product outlet is arranged at the bottom of the ellipsoidal shell.

[0011] Preferably, the reactor further comprises alumina thermal insulation ceramics;

[0012] Alumina thermal insulation ceramics are arranged between the ellipsoidal graphite sheet and the ellipsoidal shell.

[0013] Preferably, the reactor further comprises a flange and fastening bolts with a built-in water cooling pipeline;

[0014] The flange of the built-in water cooling pipeline is set at the edge of the upper surface of the quartz window. The fastening bolts pass through the flange of the built-in water cooling pipeline and the lower reverse edge of the ellipsoidal shell to clamp the quartz window between the flange of the built-in water cooling pipeline and the ellipsoidal shell. The flange of the built-in water cooling pipeline is used to pass cold water to cool the quartz window.

[0015] Preferably, the porosity of the foamed ceramic is greater than 0.9, and the pore density of the foamed ceramic is less than 10 PPI, where PPI represents the average number of pores per unit inch.

[0016] Preferably, the ceramic foam is specifically silicon carbide ceramic foam.

[0017] The catalytic material is a metal catalyst or a non-metal catalyst.

[0018] The beneficial effects of the present invention are:

[0019] This application proposes for the first time a uniform heating solar reactor that combines energy flow distribution with an absorption coating design. The device is designed to overcome the shortcomings of uneven temperature distribution and low reaction efficiency in existing solar reactors. The technical core and advantages of this application are: (1) Based on the numerical simulation results of the solar radiation field and temperature field inside the traditional reactor, the geometric shape of the reaction medium is redesigned according to the contour lines of the above two field distributions, thereby improving the excessive concentration of radiation heat flow and temperature near the focal plane; (2) Using large-pore mesh silicon carbide foam ceramics as the reaction medium, coating the surface of the foam ceramics with catalytic materials can achieve the corresponding thermochemical reaction process. Its high specific surface area, strong light transmittance, and high thermal conductivity are conducive to further balancing the temperature field and increasing the chemical reaction rate; (3) The periphery of the foam ceramic is usually at a lower temperature, and an ellipsoidal graphite sheet covered with an absorption coating is placed there. Its function is to absorb most of the solar radiation that passes through the pores of the foam ceramic, form a high temperature, and uniformly heat the periphery of the foam ceramic reaction medium by heat conduction and heat convection, thereby further balancing the temperature field and increasing the reaction rate inside the reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a uniform heating solar reactor designed for combining energy flux distribution with an absorption coating;

[0021] Figure 2 This is the radiation density distribution diagram inside the traditional cavity solar reactor;

[0022] Figure 3 This is the temperature distribution diagram inside the traditional cavity solar reactor. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0025] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0026] Specific implementation method 1: Combination Figure 1 The present embodiment is described. The uniform heating solar reactor designed by combining energy flux distribution and absorption coating described in the present embodiment comprises a dish-type solar concentrator 2, a quartz window 3, an ellipsoidal shell 5, an ellipsoidal graphite sheet 7, an absorption coating 8 and a foam ceramic 9;

[0027] The foam ceramic 9 is a ceramic body having a plurality of through-hole foam structures, the surface of the foam ceramic 9 is coated with a catalytic material, and the foam ceramic 9 is in a semi-ellipsoidal shape;

[0028] The outer spherical surface of the foam ceramic 9 is coated with an absorption coating 8, the ellipsoidal graphite sheet 7 is wrapped on the outer surface of the absorption coating 8, the ellipsoidal shell 5 is wrapped on the outer surface of the ellipsoidal graphite sheet 7, and the axial direction of the ellipsoidal shell 5 is consistent with the long axis direction of the semi-ellipsoidal foam ceramic 9;

[0029] The quartz window 3 covers the opening of the ellipsoidal housing 5, and a semi-ellipsoidal groove is dug on the foam ceramic 9 close to the quartz window 3, and the long axis of the semi-ellipsoidal groove intersects the long axis of the foam ceramic 9 perpendicularly;

[0030] The dish-type solar concentrator 2 is located outside the quartz window 3. The dish-type solar concentrator 2 is used to collect sunlight. A portion of the collected sunlight passes through the quartz window 3 and irradiates the surface of the foam ceramic 9. The other portion passes through the pores in the foam ceramic 9 and is finally received by the ellipsoidal graphite sheet 7 coated with the absorption coating 8. The ellipsoidal graphite sheet 7 absorbs the heat of the sunlight and heats the outer spherical surface of the foam ceramic 9 adjacent to the ellipsoidal graphite sheet 7 through heat conduction, thereby making the temperature of the foam ceramic uniform.

[0031] A plurality of raw gas inlets 11 are provided on the ellipsoidal housing 5 , and all of the raw gas inlets 11 face the quartz window 3 ; a gas product outlet 10 is provided at the bottom of the ellipsoidal housing 5 .

[0032] In this embodiment, the ellipsoidal graphite sheet 7 has high thermal conductivity. After the ellipsoidal graphite sheet 7 absorbs heat, the temperature of the entire ellipsoidal graphite sheet 7 is first made uniform, and then the adjacent foam ceramics are evenly heated; thereby making the temperature of the entire foam ceramic uniform. According to the energy flow distribution results of computational fluid dynamics numerical simulation, the foam ceramic of this application adopts a "double ellipsoidal surface" geometric structure with double-layer nesting and perpendicular long and short axes to alleviate heat concentration in the front end area and enhance the uniformity of circumferential temperature distribution.

[0033] The operating principle of this application is:

[0034] The energy source of the reactor is solar energy. After the sun's rays are gathered by the dish-type solar concentrator 2, they are irradiated into the reactor through the high-temperature resistant quartz window 3, forming a high-temperature environment in the foam ceramic 9 area, and a thermochemical reaction occurs under the action of the catalytic material coated on its surface, such as methane reforming reaction, two-step water cracking reaction, etc. Due to the large pore structure of the foam ceramic 9 coated with catalytic material on the surface, part of the incident light will pass through the entire foam ceramic area, and finally irradiate the surface of the absorption coating 8 and be absorbed and converted into heat. Then, under the heat conduction of the ellipsoidal graphite sheet 7, the heat is reused to heat the outer part of the reticular silicon carbide foam ceramic 9, thereby forming a more uniform temperature field distribution. In addition, raw gas such as methane, carbon dioxide, etc. enters the reaction chamber from the raw gas inlet 11, first purges the quartz window 3 to cool and clean it, and then enters the large pore reticular foam ceramic 9 coated with catalytic material on the surface to undergo a corresponding thermochemical reaction, and the gas product formed will be sent out from the gas product outlet 10. The reason for setting the raw gas inlet 11 at the front section of the reactor is that the raw gas at room temperature can cool the high-temperature area at the front end of the reticulated silicon carbide foam ceramic 9 to a certain extent, thereby alleviating the problem of heat concentration there.

[0035] It should be noted that the geometric design of the foam ceramic 9 coated with catalytic material in the present application is one of the key conditions for achieving uniform temperature distribution. Its double-layer nested "double ellipsoid" design with long and short axes perpendicular to each other is derived from the radiation density field inside the traditional cavity solar reactor ( Figure 2 ) and temperature field ( Figure 3 ) The contour distribution in the numerical simulation results. This phenomenon is common in similar solar reactor structures. The basic simulation conditions of the relevant examples in this design are: the reaction area length is 82mm, the diameter is 60mm; the thickness of the alumina thermal insulation ceramic is 40mm, and the thermal conductivity is 12W / (mK); the incident solar energy distribution q = 1.5×10 6 exp(-2500×r 2 ), r represents the radius; the inlet flow rate is 0.25m / s, and the working fluid is air at room temperature and pressure; the pores in silicon carbide foam ceramics are macropores, the porosity of silicon carbide foam ceramics is 0.9, and the density is 3200kg / m 3 , specific heat capacity is 750J / (kgK), thermal conductivity is 80W / (mK). The advantages of this geometric design are mainly two points: first, it can significantly improve the excessive concentration of radiation heat flux and temperature distribution near the focal plane ( Figure 2 Reference numeral 12 in the figure indicates an area where the radiant heat flux is excessively concentrated. Figure 3The reference numeral 13 in the figure indicates an area where the temperature is excessively concentrated), which effectively reduces the temperature gradient at the front end of the reaction area; secondly, the geometric shape formed along the contour lines can ensure the consistency of the temperature in the circumferential direction to a large extent. After reheating of the absorption coating and the ellipsoidal graphite sheet outside the reaction area, the consistency of the temperature in the radial direction can be further achieved, thereby forming a uniform temperature field distribution.

[0036] right Figure 2 To explain: Figure 2 The radiation density of the area marked with reference numeral 12 in the figure is 1776, and the radiation density from the area marked with reference numeral 12 to the outside is 2.3×10 6 to 0.

[0037] right Figure 3 To explain: Figure 3 The reaction temperature of the region 13 in the figure is 2.3×10 6 , the reaction temperatures from the area marked 13 in the figure to the outside are 1776 to 378 respectively.

[0038] Specific embodiment 2: This embodiment further limits the uniform heating solar reactor designed by combining energy flow distribution and absorption coating described in specific embodiment 1. In this embodiment, the reactor further includes alumina thermal insulation ceramics 6;

[0039] Alumina thermal insulation ceramic 6 is arranged between the ellipsoidal graphite sheet 7 and the ellipsoidal housing 5 .

[0040] In this embodiment, the ellipsoidal shell 5 is made of stainless steel and plays a supporting role. The alumina thermal insulation ceramic 6 has a heat-insulating effect.

[0041] Specific embodiment 3: This embodiment further defines the uniform heating solar reactor designed by combining energy flow distribution and absorption coating described in specific embodiment 1. In this embodiment, the reactor further includes a flange 4 with a built-in water cooling pipeline and a fastening bolt 1;

[0042] The flange 4 with built-in water cooling pipeline is set at the edge of the upper surface of the quartz window 3, and the fastening bolt 1 passes through the flange 4 with built-in water cooling pipeline and the lower reverse edge of the ellipsoidal shell 5 to clamp the quartz window 3 between the flange 4 with built-in water cooling pipeline and the ellipsoidal shell 5. The flange 4 with built-in water cooling pipeline is used to pass cold water to cool the quartz window 3.

[0043] In this embodiment, the quartz window 3 is a high temperature resistant quartz window 3 .

[0044] Specific embodiment four: This embodiment further limits the uniform heating solar reactor designed by combining energy flow distribution and absorption coating described in specific embodiment one. In this embodiment, the porosity of foam ceramic 9 is greater than 0.9, and the pore density of foam ceramic 9 is less than 10PPI, where PPI represents the average number of pores per unit inch of length.

[0045] Specific embodiment 5: This embodiment further limits the uniform heating solar reactor combining energy flux distribution and absorption coating design described in specific embodiment 2. In this embodiment, the foam ceramic 9 is specifically silicon carbide foam ceramic.

[0046] In the present embodiment, the silicon carbide foam ceramic is a ceramic body having a porous foam structure after firing silicon carbide powder.

[0047] Specific embodiment six: This embodiment further limits the uniform heating solar reactor combining energy flow distribution and absorption coating design described in specific embodiment five. In this embodiment, the catalytic material is a metal catalyst or a non-metal catalyst.

[0048] In this embodiment, the catalytic material can be a metal catalyst or a non-metal catalyst, depending on the reaction type of the relevant thermochemical process.

[0049] The following is an example of a catalyst material being a metal catalyst: For example, the catalyst material in the foam ceramic 9 is a metal-based oxygen carrier MO x When sunlight shines on the catalytic material on the surface of the foam ceramic 9, MO x Part of the oxygen atoms are separated to form reduced metal oxide MO x-δ , and release a small amount of oxygen. The specific reduction chemical formula is: MO x →MO x-δ +0.5δO 2 When the raw gas (such as methane, carbon dioxide, etc.) is introduced into the raw gas inlet 11, MO x-δ Seize CO 2 The oxygen atoms in the raw materials generate gaseous products CO. The specific oxidation steps are: MO x-δ +δCO 2 →MO x +δCO, M represents a metal element, δ is CO 2 The stoichiometric coefficient of , x is a positive integer.

[0050] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A uniform heating solar reactor combining energy flux distribution and absorption coating design, characterized in that: The reactor comprises a dish-type solar concentrator (2), a quartz window (3), an ellipsoidal housing (5), an ellipsoidal graphite sheet (7), an absorption coating (8) and foam ceramics (9); The foam ceramic (9) is a ceramic body having a plurality of through-hole foam structures, the surface of the foam ceramic (9) is coated with a catalytic material, and the foam ceramic (9) is in a semi-ellipsoidal shape; The outer spherical surface of the foam ceramic (9) is coated with an absorption coating (8), the ellipsoidal graphite sheet (7) is wrapped around the outer surface of the absorption coating (8), the ellipsoidal shell (5) is wrapped around the outer surface of the ellipsoidal graphite sheet (7), and the axial direction of the ellipsoidal shell (5) is consistent with the long axis direction of the semi-ellipsoidal foam ceramic (9); The quartz window (3) covers the opening of the ellipsoidal housing (5), and a semi-ellipsoidal groove is dug on the foam ceramic (9) close to the quartz window (3), and the long axis of the semi-ellipsoidal groove intersects the long axis of the foam ceramic (9) perpendicularly; The dish-type solar concentrator (2) is located outside the quartz window (3). The dish-type solar concentrator (2) is used to concentrate sunlight. A portion of the concentrated sunlight passes through the quartz window (3) and irradiates the surface of the foam ceramic (9). The other portion passes through the pores in the foam ceramic (9) and is finally received by the ellipsoidal graphite sheet (7) coated with an absorption coating (8). After absorbing the heat of the sunlight, the ellipsoidal graphite sheet (7) heats the outer spherical surface of the foam ceramic (9) adjacent to the ellipsoidal graphite sheet (7) through heat conduction, thereby making the temperature of the foam ceramic uniform. A plurality of raw gas inlets (11) are provided on the ellipsoidal housing (5), and the plurality of raw gas inlets (11) are all directed toward the quartz window (3); a gas product outlet (10) is provided at the bottom of the ellipsoidal housing (5).

2. The uniform heating solar reactor according to claim 1, characterized in that: The reactor also includes alumina thermal insulation ceramics (6); Alumina heat insulating ceramics (6) are arranged between the ellipsoidal graphite sheet (7) and the ellipsoidal outer shell (5).

3. The uniform heating solar reactor according to claim 1, characterized in that: The reactor further comprises a flange (4) with a built-in water cooling pipeline and fastening bolts (1); The flange (4) of the built-in water cooling pipeline is arranged at the edge of the upper surface of the quartz window (3), and the fastening bolts (1) pass through the flange (4) of the built-in water cooling pipeline and the lower reverse edge of the ellipsoidal shell (5) to clamp the quartz window (3) between the flange (4) of the built-in water cooling pipeline and the ellipsoidal shell (5). The flange (4) of the built-in water cooling pipeline is used to pass cold water to cool the quartz window (3).

4. The uniform heating solar reactor according to claim 1, characterized in that: The porosity of the foam ceramic (9) is greater than 0.9, and the pore density of the foam ceramic (9) is less than 10 PPI, where PPI represents the average number of pores per unit inch.

5. The uniform heating solar reactor according to claim 1, characterized in that: The foam ceramic (9) is specifically silicon carbide foam ceramic.

6. The uniform heating solar reactor according to claim 1, characterized in that: The catalytic material is a metal catalyst or a non-metal catalyst.

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