Oxidation reactor for methanol reforming hydrogen production system

Abstract

The utility model relates to an oxidation reactor for a methanol reforming hydrogen production system, which comprises a gas-liquid mixing end and an oxidation reaction end which are connected with each other, the front end of the gas-liquid mixing end is provided with a gas inlet end cover and a methanol solution atomizing nozzle, and an electric heating net is arranged between the gas-liquid mixing end and the oxidation reaction end. The electric heating net and the inner wall of the oxidation reaction end are coated with an oxidation catalyst. According to the utility model, the evaporator required for atomizing the raw material methanol solution of the oxidation reactor is improved into the methanol solution atomizing nozzle arranged at the front part of the gas-liquid mixing end, so that the problem that a special evaporator needs to be arranged for vaporization is solved, the evaporator does not need to be connected, and the problem of control delay is solved; the electric heating net is arranged at the front end of the oxidation reaction tube, so that the problems of high energy consumption, long starting time and incapability of cold starting of the system in a low-temperature environment in a starting stage are solved through rapid heating.

Description

Technical Field

[0001] The utility model belongs to the technical field of hydrogen production reactors for methanol, and particularly relates to an oxidation reactor used in a methanol reforming hydrogen production system. Background Art

[0002] A methanol reformer is a device used in chemical engineering, especially in the field of fuel cell technology, which produces hydrogen for hydrogen fuel cells by reacting a mixture of methanol and water (steam). Methanol is converted into hydrogen and carbon dioxide by the combined action of pressure, heat and catalysts, and high-purity hydrogen can then be extracted by pressure swing adsorption (PSA) or separation membranes.

[0003] Among them, the tube side of the reforming reaction tube of the methanol reformer needs to input a methanol solution mixture, and the shell side needs to provide a heat source to heat the methanol solution mixture in the tube side to maintain its temperature within the catalyst reaction temperature range for continuous reaction and hydrogen production. In order to save costs and materials, the same methanol aqueous solution as the methanol reforming raw material can be selected to be introduced into the oxidation reactor, heated to form high-temperature hot flue gas and passed to the shell side of the methanol reformer to achieve continuous and stable heat supply to the tube side.

[0004] Currently, the oxidation reactor used as a heating device has the following problems: 1. The variable diameter structure conventionally used to ensure air uniformity causes the mixing distance to be too long; 2. The flow deviation on the flow cross section causes uneven outlet temperature; 3. In order to vaporize the methanol solution, a special evaporator is required; 4. The energy consumption in the startup phase is large and the startup time is long; 5. The system cannot be cold-started in a low-temperature environment; 6. The temperature of the high-temperature flue gas finally generated by the oxidation reactor is related to the state of the vaporized methanol solution provided by the evaporator, and the separate configuration of the evaporator will cause control delays. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide an oxidation reactor for a methanol reforming hydrogen production system, so as to improve the efficiency and controllability of the oxidation reactor in producing hot flue gas.

[0006] The utility model solves the technical problem by adopting the following technical solution: providing an oxidation reactor for a methanol reforming hydrogen production system, comprising a connected gas-liquid mixing end and an oxidation reaction end, the front end of the gas-liquid mixing end being provided with an air inlet end cover and a methanol solution atomizing nozzle, the oxidation reaction end comprising an electric heating net and a metal honeycomb reaction channel connected to the rear end of the gas-liquid mixing end, the electric heating net and the metal honeycomb reaction channel being coated with an oxidation catalyst, a plurality of layers of the wave reaction tubes being stacked longitudinally in a radial cross section of the metal honeycomb reaction channel (8), and the wave crest spacing of the wave reaction tubes being equal in the transverse direction; along the axial direction of the metal honeycomb reaction channel (8), the wave crest spacing of the wave reaction tubes changes, and the oxidation catalyst is coated in the wave reaction tubes.

[0007] Preferably, the gas-liquid mixing end is stepped, including a first step and a second step, the top of the first step is provided with the air inlet end cover, the top of the second step is provided with a plurality of atomizing nozzle mounting seats evenly distributed around the first step, and the atomizing nozzle mounting seat is provided with the methanol solution atomizing nozzle.

[0008] Preferably, the second stage is fixedly connected to the electric heating grid via a connecting flange provided with a sealing gasket, and the tail of the metal honeycomb reaction channel is connected to the reforming reactor via a connecting flange.

[0009] Preferably, a hot flue gas outlet is provided at the tail of the oxidation reaction end, and a temperature sensor is provided at the hot flue gas outlet.

[0010] Beneficial Effects

[0011] The utility model improves the evaporator required for atomizing the raw material methanol solution of the oxidation reactor into a methanol solution atomizing nozzle arranged in front of the gas-liquid mixing end, thereby solving the problem that a special evaporator is required for vaporization and solving the control delay problem without connecting the evaporator; by arranging an electric heating network at the front end of the oxidation reaction tube, rapid heating solves the problems of high energy consumption and long startup time in the startup stage and the inability of the system to cold start in a low temperature environment.

[0012] The metal honeycomb reaction channel of the utility model adopts an alternating wave reaction tube, which changes the methanol-water vapor flow characteristics of the conventional original reaction channel, can effectively improve the temperature uniformity in the reactor, increase the contact time between the raw material and the catalyst, and improve the utilization rate of the raw material. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a three-dimensional diagram of an oxidation reactor used in a methanol reforming hydrogen production system.

[0014] Figure 2 A cross-sectional view of an oxidation reactor used in a methanol reforming hydrogen production system.

[0015] Figure 3 for Figure 1 Cross-sectional view of the metal honeycomb reaction channel.

[0016] Figure 4 for Figure 1 Stereoscopic view of the metal honeycomb reaction channel.

[0017] Among them, 1-inlet end cover; 2-first stage; 3-atomizing nozzle mounting seat; 4-methanol solution atomizing nozzle; 5-second stage; 6-connecting flange; 7-electric heating net; 8-metal honeycomb reaction channel; 9-temperature sensor; 10-gas-liquid mixing end; A-air inlet; B-methanol solution inlet; C-atomizing nozzle power interface; D-electric heating power interface; E-hot flue gas outlet. The same symbols in each figure represent the same component. DETAILED DESCRIPTION

[0018] The present invention is further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

[0019] like Figure 1 , 2 As shown, the utility model provides an oxidation reactor for a methanol reforming hydrogen production system, comprising a connected gas-liquid mixing end 10 and an oxidation reaction end, the front end of the gas-liquid mixing end 10 is provided with an air inlet end cover 1 and a methanol solution atomizing nozzle 4, the oxidation reaction end comprises an electric heating mesh 7 and a metal honeycomb reaction channel 8 connected to the rear end of the gas-liquid mixing end 10, and the electric heating mesh 7 and the metal honeycomb reaction channel 8 are coated with an oxidation catalyst.

[0020] The gas-liquid mixing end 10 is stepped, including a first step 2 for improving air divergence and uniform flow and a second step 5 for fully mixing air with methanol spray. The top of the first step 2 is provided with the air inlet cover 1, and the top center of the air inlet cover 1 is an air inlet A. The diameter of the first step 2 is larger than the diameter of the air inlet cover 1 and smaller than the diameter of the second step 5. The multi-step diameter change can quickly diffuse the air entering from the air inlet cover 1 into the large-diameter cross-section. After entering the second step 5, the air is further diffused so as to be fully mixed with the methanol spray. The first step 2 as a whole adopts a metal wire woven mesh composed of multiple layers of uniform twisted corrugated structure in the prior art to improve the diffusion efficiency.

[0021] The top of the second stage 5 is surrounded by a plurality of atomizing nozzle mounting seats 3 evenly distributed outside the first stage 2, and the methanol solution atomizing nozzle 4 is fixed to the atomizing nozzle mounting seat 3 by bolt connection, and the tail end of the methanol solution atomizing nozzle 4 is a methanol solution inlet B. In a specific embodiment, the methanol solution atomizing nozzle 4 can be further adjusted by adjusting the atomizing nozzle frequency parameter. An atomizing nozzle power supply interface C is provided on one side of the methanol solution atomizing nozzle 4 to provide power and signal transmission. The methanol solution atomizing nozzle 4 is made of a material resistant to methanol corrosion, and a pressure stabilizing chamber is provided at the front end of the methanol solution atomizing nozzle 4. The pressure stabilizing chamber can ensure that the input amount of each injection is the same while controlling the atomizing pressure, and can be used to accurately measure the amount of methanol inlet.

[0022] The methanol solution atomizing nozzle 4 is provided with an inclination angle. In a specific embodiment, the angle between the axis of the methanol solution atomizing nozzle 4 and the axis of the oxidation reactor is 30°, which improves the mixing efficiency of the methanol solution mist and the air entering the air inlet A.

[0023] The electric heating net 7 is a metal honeycomb structure made of iron, chromium and aluminum, which has good overall thermal conductivity and heat resistance, and is convenient for rapid heating through electric heating to approach the temperature required for the oxidation reaction and meet the needs of cold start in a cold environment; in addition, the oxidation catalyst matrix is ​​aluminum oxide, which ensures a tight structure between the catalyst and the iron, chromium and aluminum material of the electric heating net 7, and increases the coating strength and service life of the catalyst; when power is turned on, multiple points of the entire metal honeycomb structure cross-section are heated simultaneously, and the heating surface area is large, which can quickly and evenly heat the methanol solution-air mixture flowing through; the metal honeycomb structure has a larger specific surface area, which can increase the effective active area of ​​the catalyst and improve the oxidation reaction and efficiency.

[0024] The metal honeycomb reaction channel 8 is provided with an array of wave reaction tubes, and the wave reaction tubes with different wave crest spacings are connected in sequence, and the oxidation catalyst is coated in the wave reaction tubes. The wave reaction tubes are molded using a metal sheet with a thickness of 0.05 to 0.2, and are formed by curling and welding after multi-layer stacking, which greatly increases the surface area that can be coated with the catalyst per unit volume. At the same time, the wave reaction tubes with different wave crest spacings are connected, so that the incoming mixed fluid generates turbulence, reduces the unevenness between the channels, and improves the reaction rate and controllability. The wave reaction tube includes an upper tube wall and a lower tube wall arranged in parallel, and a wavy partition is provided between the upper tube wall and the lower tube wall. Among them, the array arrangement refers to a plurality of layers of the wave reaction tubes stacked longitudinally in the radial cross section of the metal honeycomb reaction channel 8, and the wave crest spacing of the wave reaction tubes is equal in the transverse direction; along the axial direction of the metal honeycomb reaction channel 8, the wave crest spacing of the wave reaction tubes varies. The upper tube wall in the stacked wave reaction tubes can be shared with the lower tube wall of the upper wave reaction tube. Figure 3 , 4As shown, in a specific embodiment, 5 sections of the wave reaction tubes are arranged along the axial direction of the metal honeycomb reaction channel 8, and the wave reaction tubes with wider wave crest spacing and the wave reaction tubes with narrower wave crest spacing are arranged alternately. The figure only shows 5 layers of wave reaction tubes arranged in a rectangular matrix. In actual use, the outer edge can be cut into a circle so that its shape matches the inner edge of the metal honeycomb reaction channel 8.

[0025] The second stage 5 is fixedly connected to the electric heating network 7 by a connection flange 6 provided with a sealing gasket, and the tail of the metal honeycomb reaction channel 8 is connected to the reforming reactor by the connection flange 6. In other embodiments, the utility model can also be applied to a fuel cell heat exchanger or other systems requiring a heat source. The sealing gasket is a metal-graphite composite gasket, and the connection flange 6 is a V-shaped flange and is fixedly connected by a V-shaped flange special clamp.

[0026] A hot flue gas outlet E is provided at the tail of the oxidation reaction end, and a temperature sensor 9 is provided at the hot flue gas outlet E. In the oxidation reaction end, the oxidation reaction of methanol is rapid and violent, and can generate instantaneous high temperature. By controlling the spray flow of air and methanol solution, the temperature control of the oxidation reactor is achieved. The overall air-fuel ratio range of the utility model is 15:1 to 24:1, and the temperature can be stably controlled within the range of 100-650±5°C, meeting the subsequent temperature requirements of 200-550°C for catalysts of different types of methanol reformers.

[0027] The workflow of the utility model is described in detail below:

[0028] 1. The air enters the air inlet end cover from the air inlet A, and continues to pass through the first stage 2 and the second stage 5, where it mixes with the methanol spray and completes the flow, and continues to flow backward in a uniform form;

[0029] 2. Turn on the electric heating power supply, the metal honeycomb electric heating net 7 starts to heat up, the air is evenly heated when passing through the area of ​​the electric heating net 7, and continues to flow evenly backward. When passing through the metal honeycomb structure coated with oxidation catalyst and with different mesh sizes, the heat is transferred to the oxidation catalyst, so that the temperature of the oxidation catalyst gradually increases to the starting reaction temperature point;

[0030] 3. After the oxidation catalyst reaches the starting reaction temperature point, the methanol solution atomizing nozzle 4 is turned on. The atomizing nozzle sprays the methanol solution into the mixing cavity in the form of a mist of micron-sized particles, fully mixes it with the evenly flowing air, and enters the electric heating network 7 structure with the air, starts to vaporize in a very short time, continues to flow through the variable mesh metal honeycomb reaction channel 8, and quickly starts the oxidation exothermic reaction (flameless combustion). The variable mesh metal honeycomb structure makes the mixed fluid form turbulence. When reaching the flue gas outlet, it is ensured that each area of ​​the outlet cross section is in a state of uniform flow and uniform temperature;

[0031] 4. When the flue gas outlet temperature reaches 60°C, turn off the electric heating power supply. At this time, the methanol vaporization heat absorption and oxidation heat release in this area will gradually reach a balance state. At this time, the cold start of the oxidation reactor is completed, and there is no need for electric heating to continue to supply heat. In addition, this balance state has a certain redundancy, which can ensure that under rated conditions, when switching between different liquid inlet steps, the temperature of the overall area will not drop suddenly due to the increase in liquid inlet, causing the temperature to be lower than the starting reaction temperature required by the oxidation catalyst, thereby ensuring continuous and stable operation;

[0032] 5. After the cold start is completed, increase the air intake and liquid intake in proportion according to the calibrated setting steps, gradually and quickly increase the heat release power of the oxidation reactor to the designed power state, and maintain stable operation to provide heat for subsequent use ends;

[0033] 6. According to the changes in the actual demand for hot flue gas at the back end, based on the set basic values ​​of air flow and methanol inlet volume, the control system is precisely adjusted to maintain the stable state of the user end;

[0034] 7. When starting the shutdown, follow the calibrated shutdown procedure air-fuel ratio, gradually reduce the air intake and liquid intake, and gradually reduce the heat supply. When the temperature drops to a specific state, close the atomizing nozzle, increase the air intake, and make the oxidation reactor enter the rapid cooling stage, quickly cool down to a safe temperature range and shut down all components;

[0035] 8. In an emergency, quickly close the atomizing nozzle, stop the liquid intake, and quickly turn on the fan to the maximum flow rate to allow the entire reactor to quickly enter a safe temperature range.

Claims

1. An oxidation reactor for a methanol reforming hydrogen production system, characterized in that: The invention comprises a gas-liquid mixing end (10) and an oxidation reaction end connected to each other. The front end of the gas-liquid mixing end (10) is provided with an air inlet end cover (1) and a methanol solution atomizing nozzle (4). The oxidation reaction end comprises an electric heating net (7) and a metal honeycomb reaction channel (8) connected to the rear end of the gas-liquid mixing end (10). The electric heating net (7) and the metal honeycomb reaction channel (8) are coated with an oxidation catalyst. In the radial cross section of the metal honeycomb reaction channel (8), a plurality of layers of wave reaction tubes are stacked longitudinally, and the wave crest spacing of the wave reaction tubes is equal in the transverse direction. Along the axial direction of the metal honeycomb reaction channel (8), the wave crest spacing of the wave reaction tubes changes, and the oxidation catalyst is coated in the wave reaction tubes.

2. The oxidation reactor for a methanol reforming hydrogen production system according to claim 1, characterized in that: The gas-liquid mixing end (10) is in a stepped shape, comprising a first step (2) and a second step (5); the first step (2) is provided with the air inlet end cover (1) at the top; the second step (5) is provided with a plurality of atomizing nozzle mounting seats (3) evenly distributed around the first step (2); the atomizing nozzle mounting seats (3) are provided with the methanol solution atomizing nozzle (4).

3. The oxidation reactor for a methanol reforming hydrogen production system according to claim 2, characterized in that: The second stage (5) and the electric heating network (7) are fixedly connected via a connecting flange (6) provided with a sealing gasket, and the tail of the metal honeycomb reaction channel (8) is connected to the reforming reactor via the connecting flange (6).

4. The oxidation reactor for a methanol reforming hydrogen production system according to claim 1, characterized in that: A hot flue gas outlet is provided at the tail of the oxidation reaction end, and a temperature sensor (9) is provided at the hot flue gas outlet.

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