Long-life methane reformer and method of use

Abstract

The present invention belongs to the technical field of hydrogen energy, and particularly relates to a methane reformer with a long service life and a usage method. Inside the reformer, a structure formed by combining a main gas path and a branched gas path is arranged. The outside of the gas path is filled with catalyst particles. Conical branched gas paths are installed at intervals along the gas flow direction, and along the gas flow direction, the diameter of the main gas path smoothly decreases. The inside of the gas path is filled with inert particles, and the inside and outside of the gas path have the same porosity. According to the carbon deposition kinetics, the structure evolution theory of the porous catalyst region, and the hydrodynamics theory of the porous medium, the reformer disclosed in the present invention can, without changing the external conditions of the reformer and the conversion rate of the reformer, by installing a main gas path and a branched gas path inside the reformer, after being locally blocked due to carbon deposition, automatically change the air flow direction, reach the next branched gas path, automatically adjust the main occurrence position of the reforming reaction, and extend the service life of the reformer.

Description

[Technical Field]

[0001] The present invention relates to the technical field of hydrogen energy, and more particularly to a methane reformer having a long life and a method for using the same. [Background technology]

[0002] Hydrogen energy is a clean energy source with great potential for development. Currently, hydrogen production methods mainly include hydrocarbon reforming, alcohol reforming, water electrolysis, biomass, and solar energy. Of these, hydrocarbon reforming is characterized by the low cost and easy availability of reactants. Currently, methane-steam reforming hydrogen production accounts for 50% of the world's hydrogen supply, and research into methane reforming technology is of great importance to the development of the hydrogen energy industry.

[0003] In methane steam reforming reactions, regardless of the reaction temperature or intake air flow rate, the reaction occurs intensively at the air inlet of the reformer, resulting in carbon deposition. When the porosity of the air inlet decreases due to carbon deposition, the reaction rate and conversion rate of the reactants in the reformer also decrease. As the reformer's operating time increases, the carbon deposition causes clogging of the front of the reformer, significantly shortening the lifespan of the methane reformer.

[0004] Currently, the most common methods to prevent reformer failure due to carbon deposition during the reaction process are to use precious metal catalysts or replace the catalyst support. New materials offer better carbon deposition prevention, but the manufacturing costs of precious metal catalysts and new supports are high. Increasing the water-to-carbon ratio can also promote the methane reforming reaction and reduce carbon deposition. However, increasing the water-to-carbon ratio increases energy consumption and reduces the concentration of hydrogen produced, making it difficult to meet the requirements for producing high-purity hydrogen. Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above technical problems, the present invention provides a methane reformer with a long life and a method for using the same, which can effectively solve the problems of reformer failure due to carbon deposition at the inlet during the methane reforming process and the decrease in the concentration of hydrogen produced when the water-to-carbon ratio is increased. [Means for solving the problem]

[0006] To achieve the above objectives, the present invention adopts the following technical solutions:

[0007] A methane reformer having a long life includes a reformer body, and a main air passage and a branch air passage provided in the reformer body, the main air passage being disposed on a central axis of the reformer body along a longitudinal direction of the reformer body, and a plurality of branch air passages being provided at intervals on the main air passage; catalyst particles are filled in the reformer body outside the main air passage and the branch air passage, and inert particles are filled in the main air passage and the branch air passage, and the catalyst particles have the same porosity as the inert particles; An intake port is provided on the inner diameter of the main air passage, the inner diameter of the main air passage gradually decreases along a direction away from the intake port, and a plurality of branch air passages are distributed in the main air passage; The branch air passage has a truncated cone structure, with the large end face of the branch air passage communicating with the main air passage and the small end face being an exhaust port. The reaction gas passes through the main air passage, flows out through the branch air passage, reacts with the gas catalyst particles, and finally flows out from the tail of the reformer body.

[0008] In a further preferred embodiment, the length of the main air passage is (LR)≦l≦L 2 / (L+R), the diameter of the air inlet of the main air passage is 2R / 5≦D≦2R / 3, and the diameter of the air outlet of the main air passage is (2R 2 / 5L)≦d≦(2R 2 / 3L), and the number of branch air channels is n = L / R, where L is the length of the reformer body, R is the radius of the reformer body, l is the length of the main air channel, and d is the diameter of the exhaust port of the main air channel.

[0009] In a further preferred embodiment, the height of the truncated cone of the branch air passage is 2R / 5≦h≦2R / 3, and the diameter of the bottom surface of the branch air passage is h / 3≦D b ≦h / 2, and the diameter of the branch air passage outlet is D b / 3≦d b ≦D b The branch air passage is installed obliquely with respect to the main air passage, the gas outlet of the branch air passage is closer to the gas outlet of the main air passage than the gas inlet, the included angle between the axis of the branch air passage and the axis of the main air passage is 30°<θ<75°, the outlet cross section of the branch air passage is parallel to the axis of the main air passage, R is the radius of the reformer body, h is the height of the truncated cone of the branch air passage, D b is the diameter of the large end face of the truncated cone of the branch air passage.

[0010] In a further preferred embodiment, the operating temperature range of the reformer body is 400-800°C, and the water-to-carbon ratio of the intake air of the reformer is 1-4.

[0011] In a further preferred embodiment, the catalyst particle material is a nickel-based catalyst, and the total mass of the loaded catalyst is M catalyst and the density is ρ catalyst and the inert particulate material is spherical alumina corundum, and the total mass of the inert particles is M d and the density is ρ d and M catalyst / (ρ catalyst ×V out )=M d / (ρ d ×V out ), the inside and outside of the air passage have the same porosity, and V in is the total internal volume of the main airway and the branch airway, and the total volume V out is the total volume outside the main air passage and the branch air passages in the reformer body, and the material of the main air passage and the branch air passages is heat-resistant quartz glass.

[0012] The method for using a methane reformer having a long life includes the following steps 1 to 3. Step 1: The reactant gas enters through the air inlet of the main air passage. As the diameter of the main air passage gradually decreases and becomes smaller than that of the branch air passages, the pressure drop of the air flow passing through the first row of branch air passages of the main air passage is smaller than that of the other rear branch air passages. According to the fluid mechanics theory of porous media, the air flow will preferentially pass through the first row of branch air passages, which have a smaller flow resistance. Step 2: The reaction between the reactant gas and the catalyst packed outside the air passage begins near the outlet of the first branch air passage. As the reaction progresses, carbon deposition occurs continuously, reducing the porosity of the porous catalyst at the outlet of the first branch air passage. As the air flow passes through the first branch air passage, the flow resistance increases. In addition, the carbon deposits cover the surface of the catalyst, reducing the local reaction rate in the porous catalyst region. The flow of the reactant gas automatically changes direction, and the reactant gas passes through the second branch air passage on the air inlet side of the main air passage. A reaction begins with the catalyst packed outside the second branch air passage near the outlet of the air passage. Step 3: The reactant gas reacts in each row of branch air passages after the main air passage, until carbon deposits occur and blockages occur. When the last row of branch air passages becomes blocked, the reaction finally stops. [Effects of the Invention]

[0013] By installing a main air channel and a branch air channel inside the reformer, the present invention automatically redirects the airflow after local blockage due to carbon deposition to reach the next branch air channel, automatically adjusting the location of the reforming reaction without changing the external reaction conditions or intake air flow rate of the methane reformer, thereby extending the life of the reformer. Generally speaking, this reformer can solve the current problem of carbon deposition and eliminate the negative effects of high costs associated with replacing catalyst materials and low outlet hydrogen concentration associated with increasing the water-to-carbon ratio. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a structural schematic diagram of a methane reformer according to the present invention. [Figure 2] (a) is a schematic diagram of the structure of the main airway, and (b) is a schematic diagram of the structure of the branch airway. [Figure 3] (a) is the geometric structure of a conventional methane reformer, and (b) is the geometric structure of the methane reformer of the present invention. [Figure 4] 1(a) is a schematic diagram of the reaction rate of a branch air channel of the present invention, in which the cross section of the gas outlet is parallel to the axis of the main air channel, and FIG. 1(b) is a schematic diagram of the reaction rate of a normal branch air channel. [Figure 5] 1A and 1B are schematic diagrams showing the change in reaction porosity with reaction time according to the present invention, where (a) is a schematic diagram of the reaction rate of the methane reformer of the present invention at a reaction time of 5×105 s, (b) is a schematic diagram of the average reaction rate at each outlet of the branched air channels of the present invention at a reaction time of 5×105 s, (c) is a schematic diagram of the reaction rate of the methane reformer of the present invention at a reaction time of 1.5×106 s, (d) is a schematic diagram of the average reaction rate at each outlet of the branched air channels of the present invention at a reaction time of 1.5×106 s, (e) is a schematic diagram of the reaction rate of the methane reformer of the present invention at a reaction time of 2.5×106 s, and (f) is a schematic diagram of the average reaction rate at each outlet of the branched air channels of the present invention at a reaction time of 2.5×106 s. [Figure 6] (a) is a schematic diagram of the porosity of a conventional reformer at a reaction time of 1.5×10 6 s, and (b) is a schematic diagram of the porosity of the methane reformer of the present invention at a reaction time of 1.5×10 6 s. [Figure 7] FIG. 1 is a schematic diagram comparing the conversion efficiency of the methane reformer of the present invention with the change in water-to-carbon ratio when L / R=5. [Figure 8] (a) is a comparison diagram of the conversion efficiency of a conventional extended reformer and the extended reformer of the present invention when L / R=10, and (b) is a schematic diagram comparing the increase in aspect ratio between the methane reformer of the present invention and a conventional reformer. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the technical solutions of the embodiments of the present invention will be described clearly and fully with reference to the drawings of the embodiments of the present invention. However, it is obvious that the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0016] Example 1 As shown in Figure 1, in this long-life methane reformer with a new structure, the reformer body 4 has an intake pipe 6 and an exhaust pipe 7. The reformer body 4 is configured with a structure formed by combining a main air passage 2 and a branch air passage 3. The outside of the air passage is filled with catalyst particles 4, and the inside is filled with inert particles 5. The inside and outside of the air passage have the same porosity. The main air passage 2, the branch air passage 3, the catalyst particles 4, and the inert particles 5 are confined between a perforated plate 8 and a baffle 9. The baffle 9 is located on the intake pipe 6 side of the reformer body 4, and the baffle 9 is located on the exhaust pipe 7 side of the reformer body 4. The intake port of the main air passage 2 is the perforated plate 8. The reaction gas can pass through the perforated plate 8, but the inert catalyst particles cannot pass through the perforated plate 8. Conical branch air passages are installed at intervals along the gas flow direction, and the diameter of the main air passage smoothly decreases along the gas flow direction.

[0017] The length of the main air passage of the reformer is (LR)≦l≦L 2 / (L+R), and n=L / R branch air channels of the reformer are installed along the main air channel. The diameter of the air inlet of the main air channel is 2R / 5≦D≦2R / 3, and the diameter of the air outlet is (2R 2 / 5L)≦d≦(2R 2 / 3L).

[0018] The height of the branch air passage of the reformer is 2R / 5≦h≦2R / 3, and the diameter of the bottom of the branch air passage is h / 3≦D b ≦h / 2, and the diameter of the branch air passage outlet is D b / 3≦d b ≦D b The cross section of the outlet of the branch air passage 3 is parallel to the axis of the main air passage, and the included angle between the branch air passage and the axis of the main air passage is 30°<θ<75°.

[0019] The cross section of the outlet of the branch air passage of the reformer is parallel to the axis of the main air passage and is inclined at an angle of 30° to 75° in the direction in which the diameter of the main air passage decreases.

[0020] The operating temperature range of the reformer is 400-800°C, and the water-to-carbon ratio of the reformer intake air is 1-4.

[0021] The catalyst is packed on the outside of the air passage of the reformer, and the catalyst material is a nickel-based catalyst. The total mass of the packed catalyst is M catalyst and the density is ρ catalyst The inside of the reformer air passage is filled with inert particles, the material of which is spherical alumina corundum, and the total mass of the inert particles is M d and the density is ρ d and M catalyst / (ρ catalyst ×V out )=M d / (ρ d ×V out ) and the inside and outside of the air passage have the same porosity, and the air passage material is high temperature resistant quartz glass.

[0022] The operating process of the reformer is as follows: As reactants enter the air inlet, the diameter of the main air passage decreases, making it smaller than the diameter of the branch air passages. Therefore, the pressure drop when passing through the first branch air passage is smaller than when passing directly through the main air passage. Therefore, the air preferentially passes through the first branch air passage and begins to react with the catalyst packed outside the first branch air passage near its outlet. As time passes, carbon buildup occurs, causing a blockage. As the air passes through the first branch air passage, the flow resistance increases, automatically redirecting the reactant gas flow. The reactant gas then passes through the second branch air passage, where it begins to react with the catalyst packed outside the second branch air passage near its outlet. The reaction continues in the third, fourth, and fifth branch air passages, stopping when carbon buildup causes a blockage.

[0023] To further understand the essence of the present invention, a carbon deposition prevention methane reformer composite structure was established using COMSOL software based on the methane reforming reaction, as shown in Figure 3. The new reformer model has a length of L = 0.25 m, a radius of R = 0.05 m, a main air channel length of l = 0.2 m, an air inlet diameter of D = 0.02 m, and an outlet diameter of d = 0.004 m. In the axial direction, branch air channels are installed at positions 0.02 m, 0.06 m, 0.1 m, 0.14 m, and 0.18 m from the air inlet. The branch air channel height is h = 0.04 m, and the bottom diameter of the branch air channel is D = 0.004 m. b= 0.02m, outlet diameter is d b = 0.01m, total airway area is 0.006875m 2 The reformer usually measures the methane gas flow rate corresponding to the catalyst mass, and in order to compare the catalytic effect of the reformer of the present invention and a conventional reformer at the same intake flow rate, a comparison was made with a conventional methane reformer model packed with catalyst of the same volume (same mass). The packing area of the conventional methane reformer was 0.25 × 0.1 - 0.006875 = 0.018125 m 2 The length is Lp = 0.25 m and the radius is Rp = 0.03625 m. The two reformers have the same intake flow rate of 5.5876 × 10 -6 m 3 / s, the reaction temperature was 973 K, and the molar ratio of water to methane was 2:1 (0.65:0.32).

[0024] As shown in Figure 4, the reaction rates at two points on the back of the conventional conical branching air channel were 0.16349 m / s and 0.24176 m / s, respectively, while the reaction rates at two points on the back of the branching air channel with a cross section parallel to the axis of the main air channel were 0.33326 m / s and 0.59395 m / s, respectively, an increase of 103.84% and 145.68% compared to the conventional conical branching air channel. The branching air channel cross section parallel to the axis of the main air channel allows for more efficient utilization of the catalyst on the back.

[0025] As shown in Figure 5, 5 x 10 5 As the reaction progresses, the reaction rate in the first branch channel of the methane reformer of the present invention becomes maximum, and the porosity gradually decreases. 6 As the reaction progresses, the reaction rate in the first branch passage decreases due to the influence of carbon deposition, and in the methane reformer of the present invention, the reaction rate in the fourth branch passage is the highest. 6 As the reaction progresses, the reaction rate in the fourth branch passage slows down due to carbon deposition, and in the methane reformer of the present invention, the reaction rate in the fifth branch passage is maximized. In other words, when the first branch passage of the new reformer becomes blocked due to a reaction, the reaction gas moves to the other branch passages and can continue the subsequent reaction.

[0026] Methane reforming efficiency

number

[0027] As shown in Figure 7, the reformer of the present invention has a higher reformer efficiency when the water-to-carbon ratio is 2:1 than when the water-to-carbon ratio is increased to 3:1, and the concentration of hydrogen at the outlet of the methane reformer of the present invention is higher than when the water-to-carbon ratio is 3:1. 6 Taking the case where the s reaction proceeds as an example, the hydrogen concentration at the outlet of the methane reformer of the present invention is 0.35273, which is 2.5 times the hydrogen concentration at the outlet of 0.13838 when the water-to-carbon ratio is increased to 3:1, and the lifespan can be extended without reducing the hydrogen concentration at the outlet.

[0028] As shown in FIG. 8, when the reformer of the present invention is applied under a larger L / R condition, the same volume of catalyst is loaded and the same intake flow rate of 5.5876×10 -6 m 3 / s, the reaction temperature was 973 K, and the molar ratio of water to methane was 2:1 (0.65:0.32).6 As the reaction progresses, the reforming efficiency of a conventional reformer drops to 50%, while the methane reformer of the present invention remains at 80%. 6 As the reaction progresses, the efficiency of a typical methane reformer drops to 20%, or 3.5 × 10 6 When the s reaction proceeds, the methane reforming efficiency of the present invention decreases to 20%, and the lifespan is extended by 1.75 times. Therefore, when applied under large L / R conditions, the present invention can achieve better optimization results.

[0029] The above are only preferred specific embodiments of the present invention, and the protection scope of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed in the present invention should fall within the protection scope of the present invention. [Explanation of symbols]

[0030] 1 Reformer body 2 Main airway 3 Branching airways 4. Catalyst particles 5 Inert particles 6 Intake pipe 7 Exhaust pipe 8 Perforated plate 9 Baffles

Claims

1. A methane reformer having a long life includes a reformer body (1), a main air passage (2) and a branch air passage (3) provided in the reformer body (1), the main air passage (2) is arranged on a central axis of the reformer body (1) along the length direction of the reformer body (1), and a plurality of branch air passages (3) are provided at intervals in the main air passage (2); Catalyst particles (4) are filled in the reformer body (1) outside the main air passage (2) and the branch air passage (3), and inert particles (5) are filled in the main air passage (2) and the branch air passage (3), and the catalyst particles have the same porosity as the inert particles; The main air passage (2) has an intake port on its inner diameter, the inner diameter of the main air passage (2) gradually decreases in a direction away from the intake port, and a plurality of branch air passages (3) are distributed in the main air passage (2); The branch air passage (3) has a truncated cone structure, the large end face of the branch air passage (3) communicates with the main air passage (2), and the small end face is an exhaust port, and the reaction gas passes through the main air passage (2), flows out through the branch air passage (3), reacts with the gas catalyst particles (4), and finally flows out from the tail of the reformer body (1).

2. The length of the main air passage (2) is (L-R)≦l≦L ２ / (L+R), the diameter of the air inlet of the main air passage (2) is 2R / 5≦D≦2R / 3, and the diameter of the air outlet of the main air passage (2) is (2R ２ / 5L)≦d≦(2R ２ / 3L), the number of branch air channels (3) is n=L / R, L is the length of the reformer body (1), R is the radius of the reformer body (1), l is the length of the main air channel (2), and d is the diameter of the outlet of the main air channel (2).

3. The height of the truncated cone of the branch air passage (3) is 2R / 5≦h≦2R / 3, and the diameter of the bottom surface of the branch air passage (3) is h / 3≦D ｂ ≦h / 2, and the diameter of the outlet of the branch air passage (3) is D ｂ / 3≦d ｂ ≦D ｂ the branch air passage (3) is installed obliquely with respect to the main air passage (2), the gas outlet of the branch air passage (3) is closer to the gas outlet of the main air passage (2) than the gas inlet, the included angle between the axis of the branch air passage (3) and the axis of the main air passage (2) is 30°<θ<75°, the outlet cross section of the branch air passage (3) is parallel to the axis of the main air passage (2), R is the radius of the reformer body (1), h is the height of the truncated cone of the branch air passage (3), D ｂ 2. A methane reformer with a long life as claimed in claim 1, characterized in that: is the diameter of the large end face of the truncated cone of the branch air channel (3).

4. The methane reformer with long life as claimed in claim 1, characterized in that the operating temperature range of the reformer body (1) is 400-800°C, and the water-to-carbon ratio of the intake air of the reformer is 1-4.

5. The catalyst particle material is a nickel-based catalyst, and the total mass of the packed catalyst is M ｃａｔａｌｙｓｔ and the density is ρ ｃａｔａｌｙｓｔ and the inert particulate material is spherical alumina corundum, and the total mass of the inert particles is M ｄ and the density is ρ ｄ and M ｃａｔａｌｙｓｔ / (ρ ｃａｔａｌｙｓｔ ×V ｏｕｔ ) = M ｄ / (ρ ｄ ×V ｏｕｔ ), the inside and outside of the air passages have the same porosity, and V ｉｎ is the total internal volume of the main airway (2) and the branch airway (3), and the total volume V ｏｕｔ is the total volume outside the main air passage (2) and the branch air passage (3) in the reformer body (1), and the material of the main air passage (2) and the branch air passage (3) is heat-resistant quartz glass.

6. A method for using the methane reformer having a long life according to any one of claims 1 to 5, comprising the following steps 1 to 3: Step 1: The reaction gas enters through the air inlet of the main air passage (2). The diameter of the main air passage (2) gradually decreases and becomes smaller than the diameter of the branch air passage (3). Therefore, the pressure drop of the air flow passing through the first row of branch air passages (3) of the main air passage (2) is smaller than the pressure drop of the other rear branch air passages (3). According to the fluid dynamics theory of porous media, the air flow will preferentially pass through the first row of branch air passages (3) with smaller flow resistance. Step 2: The reaction gas and the catalyst filled outside the air channel begin to react near the outlet of the first row of branch air channels (3). As the reaction progresses, carbon deposition occurs continuously. According to the theory of carbon deposition kinetics and local structure evolution of porous catalysts, carbon deposition reduces the porosity of the porous catalyst at the outlet of the first row of branch air channels (3). When the air flow passes through the first row of branch air channels (3), the flow resistance increases. In addition, the carbon deposits cover the surface of the catalyst, which reduces the local reaction rate in the porous catalyst region. Due to the carbon deposition, the flow of the reaction gas automatically changes direction. The reaction gas passes through the second row of branch air channels (3) on the air inlet side of the main air channel (2). The reaction gas and the catalyst filled outside the second row of branch air channels (3) begin to react near the outlet of the air channel. Step 3: The reaction gas reacts in turn in each row of branch air passages (3) after the main air passage (2), carbon deposits occur and blockages occur, and when the last row of branch air passages (3) becomes blocked, the reaction finally stops.

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