Variable cross-section sleeve type reactor based on reforming reaction characteristics and power mechanism

Abstract

The application discloses a variable cross-section methanol steam reforming hydrogen production reactor based on reaction characteristics and belongs to the technical field of comprehensive performance improvement of reforming hydrogen production reactors. The heating effect is enhanced under the same boundary condition by changing the structure at a place with a large heat demand. The variable cross-section sleeve type reactor comprises an outer pipe and an inner pipe which is coaxially arranged in the outer pipe and penetrates the outer pipe. A reforming channel is formed in the inner pipe, and the reforming channel is filled with a catalytic bed. A heating channel which wraps the inner pipe is formed in the outer pipe. A plurality of wave-shaped ribs are uniformly distributed on the outer wall of the inner pipe and arranged along the length direction of the inner pipe. The pipe openings at the two ends of the inner pipe are a reforming inlet and a reforming outlet respectively. The two ends of the outer pipe are provided with a hot air inlet and a hot air outlet respectively. The variable cross-section methanol steam reforming hydrogen production reactor has the advantages of compact structure, low hydrogen supply pressure, safe operation and the like.

Description

Technical Field

[0001] This invention relates to a variable cross-section methanol-water vapor reforming hydrogen production reactor based on reaction characteristics, belonging to the technical field of comprehensive performance improvement of reforming hydrogen production reactors. Background Technology

[0002] Methanol, as a hydrogen carrier, stands out among many hydrogen production feedstocks due to its advantages such as easy availability and storage, low toxicity, high hydrogen-to-carbon ratio, and sulfur-free nature. With the advent of efficient and low-cost catalysts, methanol steam reforming for hydrogen production has also attracted widespread attention in the industry due to its high hydrogen yield, mild reaction, low reaction temperature (250-300℃), and the ability to utilize industrial waste heat as a heat source.

[0003] A reforming reactor is a device for the methanol-to-hydrogen reforming reaction using steam reforming. Methanol undergoes a strongly endothermic reaction in the reforming reactor, and its reforming efficiency is affected by factors such as catalyst activity. The uniformity and stability of temperature within the reforming reactor are the main factors influencing catalyst activity. To effectively improve the methanol conversion rate, hydrogen yield, and reduce energy consumption in the reforming reactor, it is generally necessary to have a high specific surface area and high heat transfer efficiency, fully utilizing the heat provided by external heat sources to achieve efficient methanol reforming. Therefore, it is necessary to optimize the design of the reforming unit to improve its reforming characteristics.

[0004] Existing methods for optimizing reforming reactor performance can be mainly divided into heating parameter optimization and reactor structure optimization. Heating parameter optimization targets the characteristics of methanol-water vapor reforming reaction and improves reactor performance by changing the heating conditions. Reactor structure optimization, under the same heating conditions, aims to improve the efficiency of methanol reforming for hydrogen production while minimizing energy consumption through optimized reactor design.

[0005] In the current optimization of reforming reactor structures, there are few studies that consider changes to the reactor structure based on reaction characteristics. Current research often focuses on the optimization effects of the type, number, and layout of fins in the channels on the reactor, but lacks in-depth research on the temperature distribution characteristics within the reactor. Summary of the Invention

[0006] To address the above problems, this invention proposes a variable cross-section sleeve reactor and power mechanism based on the characteristics of the reforming reaction. First, the methanol conversion rate and Nusselt number ratio of the reactor are obtained. Then, the optimal rib parameters for reforming and heat exchange performance are predicted by combining response surface methodology. This takes into account factors such as methanol reforming efficiency and efficient utilization of external heat sources. In areas with high heat demand, structural modifications enhance the heating effect under the same boundary conditions, thereby effectively improving the efficiency of methanol reforming for hydrogen production while reducing the energy consumption of the device.

[0007] The technical solution of the present invention is as follows: the variable cross-section sleeve reactor includes an outer tube and an inner tube that runs through the outer tube and is coaxially arranged therewith; a reforming channel is formed in the inner tube and the reforming channel is filled with a catalyst bed; and a heating channel that wraps around the inner tube is formed in the outer tube.

[0008] The outer wall of the inner tube is evenly distributed with multiple wavy ribs arranged along its length. The two ends of the inner tube are respectively the reforming inlet 4 and the reforming outlet 5. The two ends of the outer tube are respectively opened with hot air inlet and hot air outlet.

[0009] The hot air inlet has two parts, namely the first inlet 1 and the second inlet 2; the hot air outlet also has two parts, namely the first outlet 6 and the second outlet 7.

[0010] The reforming channel is divided into an inlet preheating zone, a central catalyst bed, and a product diffusion zone from one end where the reforming inlet 4 is located. The inner wall of the heating channel is an arc-shaped surface that tapers inward from the middle, and the inner diameter of the heating channel is larger at both ends and smaller in the middle.

[0011] The reforming performance of the reactor can be evaluated by obtaining the methanol conversion rate α based on the methanol mass fractions at the reforming inlet and outlet, combined with the following formula.

[0012]

[0013] In the formula C CH3 OH ,in C represents the mass fraction of imported methanol. CH3 OH ,out This indicates the mass fraction of methanol exported;

[0014] The heat transfer performance of the variable cross-section shell-and-tube reactor can be calculated based on the flow parameters of the outer wall of the reforming channel, using the following formula to determine the overall heat transfer coefficient PEC:

[0015]

[0016]

[0017]

[0018] In the formula, Nu is the Nusselt number, f is the coefficient of friction, d is the pipe diameter, λ is the thermal conductivity, and d e ρ is the hydraulic diameter of the heat exchange channel, u is the fluid density, l is the fluid velocity, and l is the pipe length.

[0019] The number and spacing of the corrugated ribs are adjusted as follows: Considering the enhanced heat exchange requirements of the methanol steam reforming hydrogen production reactor, eight sets of corrugated ribs of the same size are arranged at equal intervals in the circumferential direction on the outer wall of the reforming channel.

[0020] The outer radius R1 at the reforming inlet of the heating channel, the radius R2 at the minimum cross section, and the distance D from the minimum cross section to the catalyst bed are adjusted as follows: A multi-parameter study table is designed using the Box-Behnken method in response surface methodology. First, values ​​are selected within a reasonable range based on the reactor structural characteristics. The three parameters R1, R2, and D are used as influencing factors. The methanol conversion rate α and the comprehensive heat transfer coefficient PEC described in claim 4 are used as response results. Simulation calculations are performed under the same heating parameters. Finally, the values ​​of R1, R2, and D that make the reactor performance better are predicted using the response surface model.

[0021] The variable cross-section sleeve reactor is housed in a power mechanism, which includes an engine and a fuel cell for powering the engine; the reforming inlet is connected to the engine's exhaust pipe, and the reforming outlet is connected to the fuel cell via a processor.

[0022] Compared to traditional reforming hydrogen production reactors, the outstanding advantages of this invention are as follows: First, it utilizes the waste heat of engine exhaust gas to reform hydrogen production, reducing waste heat from exhaust gas; second, the reformed rich gas can be used for engine in-engine blending, improving engine combustion performance, reducing fuel consumption, and improving emissions; third, the reformed gas can be used in hydrogen fuel cells to provide auxiliary power to aircraft or ships, improving the overall energy utilization efficiency of the device and improving the operational energy efficiency index; fourth, this invention has advantages such as compact structure, low hydrogen supply pressure, and safe operation. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the case.

[0024] Figure 2 This is a schematic diagram of the internal structure of this case.

[0025] Figure 3 This is a schematic diagram illustrating the improved reforming performance in this embodiment.

[0026] In the diagram, 1 is the first inlet, 2 is the second inlet, 3 is the wavy rib, 4 is the reforming inlet, 5 is the reforming outlet, 6 is the first outlet, and 7 is the second outlet. Detailed Implementation

[0027] To clearly illustrate the technical features of this patent, the following detailed description is provided through specific embodiments and in conjunction with the accompanying drawings.

[0028] like Figure 1As shown, one embodiment of the present invention is provided: the main body of the dual-tube reforming hydrogen production reactor consists of a reforming channel and a heating channel, and the outer wall of the reforming channel is also provided with multiple corrugated fins to enhance heat exchange; the reactor is heated by hot air flowing in from the first inlet 1 and the second inlet 2, and after heat exchange with the wall of the reforming channel, it flows out from the first outlet 6 and the second outlet 7; the corrugated fins 3 to enhance heat exchange conduct the received high-temperature waste gas to the wall of the heating channel to heat the reforming reaction; the reforming reaction occurs in the reforming channel, and the superheated vapor mixture of methanol and water enters the reforming channel from the reforming inlet 4, is heated in the preheating section, contacts the catalyst bed and undergoes a reforming reaction, and then flows out from the reforming outlet 5.

[0029] When a variable cross-section sleeve reactor is installed in a power unit, the reforming inlet can be connected to the engine's exhaust pipe, and the reforming outlet can be connected to a fuel cell via a processor. In this way, the reactor receives hot air from the high-temperature exhaust gas from the engine. The hydrogen-rich gas produced after reforming the reaction gas is treated and then enters the fuel cell. Finally, the hydrogen fuel cell powers the equipment.

[0030] The reforming performance of the reactor can be evaluated by obtaining the methanol conversion rate α based on the methanol mass fractions at the reforming inlet and outlet, combined with the following formula.

[0031]

[0032] In the formula C CH3OH,in C represents the mass fraction of imported methanol. CH3OH,out This indicates the mass fraction of methanol exported.

[0033] The heat transfer performance of the variable cross-section double-tube methanol steam reforming hydrogen production reactor based on reaction characteristics can be calculated using the flow parameters on the outer wall of the reforming channel, combined with formulas (2)-(4), to obtain the comprehensive heat transfer coefficient PEC.

[0034]

[0035]

[0036]

[0037] In the formula, Nu is the Nusselt number, f is the coefficient of friction, d is the pipe diameter, λ is the thermal conductivity, de is the hydraulic diameter of the heat exchange channel, ρ is the fluid density, u is the fluid velocity, and l is the pipe length.

[0038] After that;

[0039] To enhance heat exchange in the methanol steam reforming hydrogen production reactor, corrugated ribs are added to the outer wall of the reforming channel, and these ribs are evenly distributed on the outer wall of the reforming channel.

[0040] The reforming channel is divided into three parts: an inlet preheating zone, a central catalyst bed, and a product diffusion zone. The hot air inlet and outlet are located at both ends of the heating channel. The inner wall of the heating channel is an arc-shaped surface that tapers inward from the middle, and the inner diameter of the heating channel is larger at both ends and smaller in the middle.

[0041] like Figure 2 As shown, the variable cross-section structural parameters of the heating channel are determined by the outer radius R1 at the reforming inlet of the heating channel, the radius R2 at the minimum cross-section, and the distance D from the minimum cross-section to the catalyst bed.

[0042] In the optimization of the variable cross-section reactor, the Box-Behnken method in response surface methodology was used to design a multi-parameter study table. First, values ​​were selected within a reasonable range based on the reactor's structural characteristics. R1, R2, and D were used as influencing factors, and the methanol conversion rate α and the comprehensive heat transfer coefficient PEC as described in claim 4 were used as the response results. Simulation calculations were performed under the same heating parameters. To improve the conversion rate and reduce energy consumption, α and PEC should be as large as possible. The values ​​of R1, R2, and D that would optimize reactor performance were predicted using the response surface model.

[0043] like Figure 3 As shown, α represents the methanol conversion rate, β represents the outlet hydrogen flow rate, and other conditions remain constant. The inlet hot air temperature is used as a given value, gradually increasing from 553 K to 673 K, for CFD simulation calculations. It can be seen that the reforming performance of the reactor gradually increases as the inlet hot air temperature gradually rises. The reactor optimized with variable cross-section exhibits better reforming performance under all boundary conditions.

[0044] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A variable cross-section shell-and-tube reactor based on the characteristics of reforming reaction, characterized in that, The variable cross-section sleeve reactor includes an outer tube and an inner tube that runs through the outer tube and is coaxially arranged therewith; a reforming channel is formed in the inner tube and the reforming channel is filled with a catalyst bed; a heating channel is formed in the outer tube to wrap around the inner tube. The outer wall of the inner tube is evenly distributed with multiple wavy ribs arranged along its length. The pipe openings at both ends of the inner tube are respectively the reforming inlet (4) and the reforming outlet (5). The two ends of the outer tube are respectively opened with hot air inlet and hot air outlet. The reforming channel is divided into an inlet preheating zone, a middle catalyst bed and a product diffusion zone from one end where the reforming inlet (4) is located. The inner wall of the heating channel is an arc-shaped surface that tightens inward from the middle, and the inner diameter of the heating channel is large at both ends and small in the middle. The reforming performance of the reactor is determined by the methanol conversion rate based on the methanol mass fractions at the reforming inlet and outlet, using the following formula. α To evaluate the reforming performance of the reactor; (1) In the formula This indicates the mass fraction of imported methanol. This indicates the mass fraction of methanol exported; The heat transfer performance of the variable cross-section shell-and-tube reactor is calculated based on the flow parameters of the outer wall of the reforming channel, using the following formula to determine the overall heat transfer coefficient PEC: (2) (3) (4) In the formula, Nu is the Nusselt number. f It is the coefficient of friction. d It is the pipe diameter. λ It is the thermal conductivity. d e It is the hydraulic diameter of the heat exchange channel. ρ It is fluid density. u It is the fluid velocity. l It is the length of the pipe; The outer radius R1 at the reforming inlet of the heating channel, the radius R2 at the minimum cross-section, and the distance D from the minimum cross-section to the catalyst bed are adjusted as follows: A multi-parameter study table is designed using the Box-Behnken method in response surface methodology. Values ​​are first selected within a reasonable range based on the reactor structural characteristics. R1, R2, and D are used as influencing factors, with methanol conversion rate as the determining factor. α Using the comprehensive heat transfer coefficient PEC as the response result, simulation calculations were performed under the same heating parameters. Finally, the values ​​of R1, R2, and D that would improve reactor performance were predicted using the response surface model.

2. The variable cross-section shell-and-tube reactor based on reforming reaction characteristics according to claim 1, characterized in that, The hot air inlet has two parts, namely a first inlet (1) and a second inlet (2); the hot air outlet also has two parts, namely a first outlet (6) and a second outlet (7).

3. A variable cross-section sleeve reactor based on reforming reaction characteristics according to claim 1, characterized in that, Eight sets of wave-shaped ribs of the same size are arranged at equal intervals along the circumference of the outer wall of the reforming channel.

4. A power mechanism comprising the variable cross-section sleeve reactor based on the reforming reaction characteristics as described in claim 1, characterized in that, The variable cross-section sleeve reactor is housed in a power mechanism, which includes an engine and a fuel cell for powering the engine; the reforming inlet is connected to the engine's exhaust pipe, and the reforming outlet is connected to the fuel cell via a processor.

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