Methane reformer having a long lifespan 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 belongs to the technical field of hydrogen energy, and particularly relates to a methane reformer with a long lifespan and a method of use.

Background Art

[0002] Hydrogen energy is a clean energy with great development potential. Currently, the main methods for producing hydrogen mainly include hydrogen production by hydrocarbon reforming, hydrogen production by alcohol reforming, hydrogen production by electrolysis of water, hydrogen production by biomass, and hydrogen production by solar energy. Among them, hydrocarbon reforming has the characteristic that the reactants are inexpensive and easily available. Currently, the hydrogen production method by methane-steam reforming accounts for 50% of the world's hydrogen supply, and the research on methane reforming technology is very important for the development of the hydrogen energy industry.

[0003] In the methane-steam reforming reaction, regardless of the high or low reaction temperature and the amount of intake air flow, the reaction occurs intensively at the air inlet of the reformer, and the phenomenon of carbon deposition occurs. Due to carbon deposition, when the porosity of the air inlet decreases, the reaction rate and the conversion rate of the reactants of the reformer also decrease. As the operating time of the reformer increases, due to the carbon deposition phenomenon, the front part of the reformer is blocked, and the lifespan of the methane reformer is significantly shortened.

[0004] Currently, in order to avoid the failure of the reformer due to carbon deposition in the reaction process, it is common to use noble metal catalysts or to replace the catalyst carrier. Although new materials have a better carbon deposition prevention effect, the manufacturing costs of noble metal catalysts and new carriers are high. Also, by increasing the water-carbon ratio, the progress of the methane reforming reaction can be promoted, and carbon deposition can also be reduced. However, when the water-carbon ratio is increased, the energy consumption increases, and the concentration of the produced hydrogen decreases, making it difficult to meet the requirement of producing high-purity hydrogen.

Summary of the Invention

Problems to be Solved by the Invention

[0005] In view of the above technical problems, the present invention can effectively solve the problems that the reformer fails due to carbon deposition at the inlet in the methane reforming process, and when the water-carbon ratio is increased, the concentration of hydrogen generated decreases, and provides a methane reformer with a long lifespan and a usage method.

Means for Solving the Problems

[0006] To achieve the above object, the present invention adopts the following technical solutions.

[0007] A methane reformer with a long lifespan, comprising a reformer body, and a main gas path and a branched gas path provided in the reformer body, the main gas path is arranged along the length direction of the reformer body on the central axis of the reformer body, and a plurality of branched gas paths are provided at intervals on the main gas path. The inside of the reformer body outside the main gas path and the branched gas paths is filled with catalyst particles, and the inside of the main gas path and the branched gas paths is filled with inert particles. The catalyst particles have the same porosity as the inert particles. There is an air inlet at the inner diameter of the main gas path. The inner diameter of the main gas path gradually decreases along the direction away from the air inlet. A plurality of branched gas paths are distributed in the main gas path. The branched gas path has a frustum of a cone structure. The large end face of the branched gas path communicates with the main gas path, and the small end face is the exhaust port. The reaction gas passes through the main gas path, flows out through the branched gas path, reacts with the gas catalyst particles, and finally flows out from the tail of the reformer body.

[0008] As a further preferred embodiment, the length of the main gas path is (L - R) ≦ l ≦ L 2 / (L + R), the diameter of the air inlet of the main gas path is 2R / 5 ≦ D ≦ 2R / 3, the diameter of the air outlet of the main gas path is (2R 2 / 5L) ≦ d ≦ (2R 2 / 3L), the number of branched gas paths 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 gas path, and d is the diameter of the exhaust port of the main gas path.

[0009] As a further preferred embodiment, the height of the frustum of the branched air passage is 2R / 5 ≦ h ≦ 2R / 3, the diameter of the bottom surface of the branched air passage is h / 3 ≦ D b ≦ h / 2, the diameter of the outlet of the branched air passage is D b / 3 ≦ d b ≦ D b wherein the branched air passage is installed obliquely with respect to the main air passage, the gas outlet of the branched 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 branched air passage and the axis of the main air passage is 30° < θ < 75°, the outlet cross-section of the branched 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 frustum of the branched air passage, and D b is the diameter of the larger end face of the frustum of the branched air passage.

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

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

[0012] A method of using a long-life methane reformer, comprising the following steps 1 to 3. Step 1: The reaction gas enters through the air inlet of the main gas path. Since the diameter of the main gas path gradually decreases and becomes smaller than that of the branch gas path, the pressure drop of the air flow passing through the first row of branch gas paths in the main gas path is smaller than that of the other subsequent branch gas paths. According to the hydrodynamic theory of the porous medium, the air flow preferentially passes through the first row of branch gas paths with lower flow resistance. Step 2: The reaction gas and the catalyst filled outside the gas path start to react near the outlet of the first row of branch gas paths. As the reaction progresses, carbon deposition continuously occurs, the porosity of the porous catalyst at the outlet of the first row of branch gas paths decreases, and when the air flow passes through the first row of branch gas paths, the flow resistance increases. Also, since the carbon deposition covers the surface of the catalyst, the local reaction rate in the porous catalyst region decreases, and the flow direction of the reaction gas automatically changes. The reaction gas passes through the second row of branch gas paths on the air inlet side of the main gas path and starts to react with the catalyst filled outside the second row of branch gas paths near the outlet of the gas path. Step 3: The reaction gas reacts in the branch gas paths of each subsequent row in the main gas path in turn, and carbon deposition occurs and blocks the paths. When the last row of branch gas paths is blocked, the reaction finally stops.

Effect of the Invention

[0013] In the present invention, by installing the main gas path and the branch gas path inside the reformer, without changing the external reaction conditions and intake air flow rate of the methane reformer, after being locally blocked due to carbon deposition, the flow direction of the air flow is automatically changed to reach the next branch gas path, and the occurrence position of the reforming reaction is automatically adjusted to extend the life of the reformer. Generally speaking, the reformer can solve the current problem of carbon deposition, and can eliminate the adverse effects that the cost increases when the catalyst material is replaced and the hydrogen concentration at the outlet decreases when the water-carbon ratio is increased.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0015] Hereinafter, while referring to the drawings of the embodiments of the present invention, the technical solution means of the embodiments of the present invention will be clearly and fully described. 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 Fig. 1, in a long-life methane reformer with a novel structure, the reformer body 4 has an intake pipeline 6 and an exhaust pipeline 7. Inside the reformer body 4, a structure formed by combining a main gas path 2 and a branch gas path 3 is arranged. The outside of the gas path is filled with catalyst particles 4, and the inside is filled with inert particles 5. The inside and outside of the gas path have the same porosity. The main gas path 2, the branch gas path 3, the catalyst particles 4, and the inert particles 5 are restricted between a porous plate 8 and a baffle 9. The baffle 9 is located on the intake pipeline 6 side of the reformer body 4, and the baffle 9 is located on the exhaust pipeline 7 side of the reformer body 4. The intake port of the main gas path 2 is the porous plate 8. The reaction gas can pass through the porous plate 8, and the inert catalyst particles cannot pass through the porous plate 8. Conical branch gas paths are installed at intervals along the gas flow direction, and along the gas flow direction, the diameter of the main gas path gradually decreases smoothly.

[0017] The length of the main gas path of the above reformer satisfies (L - R) ≤ l ≤ L 2 / (L + R). Along the main gas path, n = L / R branch gas paths of the reformer are installed. The diameter of the air inlet of the main gas path satisfies 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 gas path of the above reformer satisfies 2R / 5 ≤ h ≤ 2R / 3. The diameter of the bottom surface of the branch gas path satisfies h / 3 ≤ D b ≤ h / 2. The diameter of the outlet of the branch gas path satisfies D b / 3 ≤ d b ≤ D b The cross-section of the outlet of the branch gas path 3 is parallel to the axis of the main gas path, and the branch gas path forms an angle of 30° < θ < 75° with the axis direction of the main gas path.

[0019] The cross-section of the outlet of the branch gas path of the above reformer is parallel to the axis of the main gas path and is inclined at 30° - 75° in the direction of the decreasing diameter of the main gas path.

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

[0021] A catalyst is filled outside the gas path of the reformer, the catalyst material is a nickel-based catalyst, and the total mass of the filled catalyst is M catalyst and the density is ρ catalyst In addition, inert particles are filled inside the gas path of the reformer. The material is spherical alumina corundum, and the total mass of the inert particles is M d and the density is ρ d where M catalyst / (ρ catalyst ×V out ) = M d / (ρ d ×V out ). The inside and outside of the gas path have the same porosity, and the gas path material is high-temperature resistant quartz glass.

[0022] The operation process of the reformer is as follows. When the reactant enters from the air inlet, the diameter of the main gas path decreases and becomes smaller than the diameter of the branch gas path. Therefore, the pressure drop when passing through the first branch gas path is smaller than the pressure drop when passing directly through the main gas path, and the air flow preferentially passes through the first branch gas path and starts to react with the catalyst filled outside the first branch gas path near the outlet of the gas path. After carbon deposition occurs and blocks the path as time increases, when the air flow passes through the first branch gas path, the flow resistance increases, automatically changing the flow direction of the reaction gas to pass through the second branch gas path and starting to react with the catalyst filled outside the second branch gas path near the outlet of the gas path. The reaction proceeds in the third, fourth, and fifth branch gas paths in sequence, and when carbon deposition occurs and blocks the path, the reaction stops.

[0023] As shown in Figure 3, to further understand the essence of the present invention, based on the methane reforming reaction, a carbon deposition prevention methane reforming reactor composite structure is established with COMSOL software to study the carbon deposition prevention effect. In the model, the length of the new reformer is L = 0.25 m, the radius is R = 0.05 m, the length of the main gas path is l = 0.2 m, the diameter of the air inlet is D = 0.02 m, and the diameter of the outlet is d = 0.004 m. In the axial direction, branch gas paths 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 height of the branch gas path is h = 0.04 m, and the diameter of the bottom surface of the branch gas path is D b= 0.02 m, the diameter of the outlet is d b = 0.01 m, the total area of the gas path is 0.006875 m 2 It is. The reformer usually measures the methane gas flow corresponding to the catalyst mass. In order to compare the catalytic effects of the reformer of the present invention and the normal reformer at the same intake air flow rate, it is compared with a normal methane reformer model filled with the same volume (same mass) of catalyst. The filling area of the normal methane reformer is 0.25×0.1 - 0.006875 = 0.018125 m 2 It is, the length is Lp = 0.25 m, and the radius is Rp = 0.03625 m. The two types of reformers have the same intake air flow rate of 5.5876×10 -6 m 3 / s, the reaction temperature is 973 K, and the molar ratio of water to methane is 2:1 (0.65:0.32).

[0024] As shown in Figure 4, the reaction rates at two points on the back of the normal conical branch gas path are 0.16349 m / s and 0.24176 m / s respectively, and the reaction rates at two points on the back of the branch gas path with a cross-section parallel to the axis of the main gas path are 0.33326 m / s and 0.59395 m / s respectively. Compared with the normal conical branch gas path, the two points increased by 103.84% and 145.68% respectively. Due to the structure that the cross-section of the branch gas path is parallel to the axis of the main gas path, the utilization of the catalyst on the back is more sufficient.

[0025] As shown in Figure 5, when the reaction proceeds for 5×10 5 s, in the methane reformer of the present invention, the reaction rate in the first branch gas path is the maximum, and the porosity gradually decreases. When the reaction proceeds for 1.5×10 6 s, due to the influence of carbon deposition, the reaction rate in the first branch gas path decreases, and in the methane reformer of the present invention, the reaction rate in the fourth branch gas path is the maximum. When the reaction proceeds for 2.5×10 6 s, due to the influence of carbon deposition, the reaction rate in the fourth branch gas path decreases, and in the methane reformer of the present invention, the reaction rate in the fifth branch gas path is the maximum. That is, when the first branch gas path of the new reformer is blocked due to the reaction, the reaction gas can move to other branch gas paths and proceed with the subsequent reaction.

[0026] Methane reforming efficiency

Number

[0027] As shown in Fig. 7, the reformer of the present invention has higher efficiency when the water-to-carbon ratio is 2:1 than when the water-to-carbon ratio increases to 3:1. The hydrogen concentration at the outlet of the methane reformer of the present invention is higher than when the water-to-carbon ratio is 3:1. Taking the case where the reaction proceeds for 1.5×10 6 s 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 increases to 3:1. The service life 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 larger L / R conditions, the same volume of catalyst is filled, the same intake air flow rate of 5.5876×10 -6 m 3 / s is used, the reaction temperature is 973K, and the molar ratio of water to methane is 2:1 (0.65:0.32). When the reaction proceeds for 1.5×106 When the s reaction proceeds, the reforming efficiency of a normal reformer decreases to 50%, while the methane reformer of the present invention remains at 80%. 2×10 6 When the s reaction proceeds, the efficiency of a normal methane reformer decreases to 20%, and 3.5×10 6 When the s reaction proceeds, the methane reforming efficiency of the present invention decreases to 20%, and the service life is extended by 1.75 times. Therefore, when applied under large L / R conditions, the present invention can obtain better optimization results.

[0029] The above is only a preferred specific embodiment of the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions and modifications made by those skilled in the art based on the technical solution and the inventive concept of the present invention within the technical scope disclosed by the present invention should belong to the protection scope of the present invention.

Explanation of Reference Numerals

[0030] 1 Reformer body 2 Main gas path 3 Branch gas path 4 Catalyst particles 5 Inert particles 6 Intake pipeline 7 Exhaust pipeline 8 Perforated plate 9 Baffle

Claims

1. A methane reformer having a long life includes a reformer body (1), and a main air passage (2) and a branch air passage (3) provided in the reformer body (1), the main air passage (2) is disposed on a central axis of the reformer body (1) along a longitudinal 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 duct (2) has an intake port on its inner diameter, the inner diameter of the main air duct (2) gradually decreases along a direction away from the intake port, and a plurality of branch air ducts (3) are distributed in the main air duct (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 2. The methane reformer having a long life as claimed in claim 1, characterized in that the number of branch air passages (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 passage (2), and d is the diameter of the exhaust port of the main air passage (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 wherein the branch air passage (3) is disposed at an angle 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), and D ｂ 2. A methane reformer having 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 branching air passage (3).

4. The methane reformer with long life as claimed in claim 1, characterized in that the working 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 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 passages have the same porosity, and V ｉｎ is the total internal volume of the main air passage (2) and the branch air passage (3), and the total volume V ｏｕｔ is a 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), and the diameter of the main air passage (2) gradually decreases and becomes smaller than the diameter of the branch air passage (3), so that 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 other rear branch air passages (3). According to the fluid mechanics theory of porous media, the air flow will preferentially pass through the first row of branch air passages (3) which have smaller flow resistance; Step 2: The reaction gas and the catalyst filled outside the air passage start to react near the outlet of the first row of branch air passages (3). As the reaction proceeds, carbon deposition occurs constantly. According to the theory of carbon deposition kinetics and local structure evolution of porous catalyst, the porosity of the porous catalyst at the outlet of the first row of branch air passages (3) is reduced due to carbon deposition. When the air flow passes through the first row of branch air passages (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 its flow direction. The reaction gas passes through the second row of branch air passages (3) on the air inlet side of the main air passage (2), and starts to react with the catalyst filled outside the second row of branch air passages (3) near the outlet of the air passage. Step 3: The reaction gas reacts in turn in the branch air passages (3) of each row after the main air passage (2), carbon deposits occur and cause blockage, and when the branch air passage (3) of the last row is blocked, the reaction finally stops.

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