CN114735650B - Self-heating methanol reforming hydrogen production device based on fractal structure and its control method - Google Patents

Abstract

The invention discloses an autothermal methanol reforming hydrogen production device based on a fractal structure and a control method thereof, wherein the autothermal methanol reforming hydrogen production device comprises a shell, a methanol reformer, a methanol solution blending tank, a methanol fuel tank, a water tank and a fuel bubbler; the methanol reformer is connected with the methanol fuel tank through the fuel bubbler, the methanol reformer is respectively connected with the methanol solution preparing tank and the water tank, the methanol solution preparing tank is respectively connected with the methanol fuel tank and the water tank, and the methanol reformer comprises a reformer shell, a methanol catalytic combustion unit, a methanol steam reforming unit and a condensing unit; the control method comprises the steps of system debugging, working condition parameter determination, preheating starting, methanol solution preparation, hydrogen production operation, reaction water recovery, hydrogen production working condition switching, shutdown, system perfection control and the like. The beneficial effects are that: the invention designs the autothermal methanol reformer based on the fractal network structure, and the thermal mass transport characteristic of the autothermal methanol reformer is well suitable for reactions with increased volume such as methanol reforming.

Description

Self-heating methanol reforming hydrogen production device based on fractal structure and its control method

Technical field

The invention relates to a methanol reforming hydrogen production device and a control method thereof, in particular to a self-heating methanol reforming hydrogen production device and a control method based on a fractal structure, and belongs to the technical field of fuel cells.

Background technique

Energy is the driving force and lifeline of the national economy. Energy development and rational and effective utilization are the source of the development of the entire society. At present, the world's political and economic structure has undergone profound adjustments, and the energy supply and demand relationship has undergone profound changes. Energy and resources are becoming increasingly scarce, and ecological and environmental problems are becoming increasingly prominent. The pressure to adjust the economic structure, improve energy efficiency, and ensure energy security has further increased. Energy development is facing a series of new problems and challenges.

From the perspective of energy conservation and ecological protection, fuel cells are regarded as one of the most promising methods of energy generation. However, the high-pressure hydrogen storage and transportation process hinders the widespread application of fuel cells due to its high cost, low safety, and difficulty in commercialization. Therefore, hydrogen storage materials such as methanol are used as the medium for transporting hydrogen. It is most preferred to produce hydrogen from oxygenated fuels such as methanol at relatively low temperatures compared to hydrogen produced from fossil fuels at high temperatures. Methanol reforming hydrogen production technology is a low-cost hydrogen production method and has been widely used in industry. Using high-energy-density liquid low-carbon methanol as a hydrogen carrier and using methanol steam reforming technology for on-site hydrogen production has become one of the preferred methods for mobile hydrogen sources.

The temperature of hydrogen production by methanol reforming is approximately between 220 and 300°C. In the existing technology, electric heating is often used as the reaction heat source, causing a large amount of energy loss and long start-up time. In addition, self-heating methods such as partial oxidation are used. The start-up speed of heating by heating, thermal coupling and other methods is very impressive, but due to the heat and mass transfer limitations of traditional flow channels such as straight flow channels, serpentine flow channels, etc., the energy loss of this method is still large; at the same time, traditional manufacturing methods The hydrogen device requires manual preparation of methanol aqueous solution and then supplies it to the methanol reforming hydrogen production device, resulting in a waste of manpower and redundant processes, which is not conducive to further promotion.

Contents of the invention

Purpose of the invention: In view of the problems existing in the existing technology, provide a fractal structure-based system that can adapt to the hydrogen production needs of different usage scenarios by automatically adjusting the ratio of methanol to water, improve fuel economy, and strengthen the heat and mass transfer process of the methanol reformer. Self-heating methanol reforming hydrogen production device and control method.

Technical solution: a self-heating methanol reforming hydrogen production device based on a fractal structure, including a shell, a methanol reformer, a methanol solution preparation tank, a methanol fuel tank, a water tank and a fuel bubbler; the methanol reformer , methanol solution preparation tank, methanol fuel tank, water tank and fuel bubbler are respectively located inside the shell. The methanol reformer is connected to the methanol fuel tank through the fuel bubbler. The methanol reformer is respectively configured with the methanol solution. The tank and the water tank are connected, the methanol solution preparation tank is connected to the methanol fuel tank and the water tank respectively, and the methanol reformer includes a reformer shell, a methanol catalytic combustion unit, a methanol steam reforming unit and a condensation unit;

The methanol catalytic combustion unit and the methanol steam reforming unit are in a back-to-back stacked structure and are installed inside the condensation unit along the central axis of the reformer housing;

The methanol catalytic combustion unit is provided with a point source fractal network structure flow channel with a central axis diverging in the radial direction; the methanol steam reforming unit is provided with a point source fractal network structure with a central axis diverging in the radial direction. Flow channel; the methanol catalytic combustion unit and the methanol steam reforming unit are not internally connected;

The outlets of the methanol catalytic combustion unit and the methanol steam reforming unit are facing the condensation unit and do not exceed the scope of the condensation unit;

The fuel bubbler is connected to the flow channel inlet of the methanol catalytic combustion unit; the methanol solution preparation box is connected to the flow channel inlet of the methanol steam reforming unit;

A hydrogen output port is provided above the reformer housing, and a water return port is provided at the bottom of the reformer housing. The water return port is connected to the water tank.

The present invention uses a self-heating method to quickly heat the methanol reformer. The methanol catalytic combustion unit and the methanol steam reforming unit are in a back-to-back stacked structure, and the heat transfer efficiency is higher; among them, the methanol catalytic combustion unit and the methanol steam reforming unit are The reaction channel is set as a point-source fractal network structure flow channel that diverges from the central axis in the radial direction, which improves the thermal coupling between the catalytic combustion of methanol and the steam reforming reaction, strengthens the heat and mass transport process, and greatly improves the heat transfer efficiency. , reduce energy loss and improve startup efficiency; after entering the fractal network flow channel, the fuel first hits and avoids and then radiates and spreads around, showing a gradual expansion trend, which has great advantages for volume increase reactions such as methanol reforming; at the same time, it is set There is a condensation unit, and the heat released during the condensation process can maintain the internal temperature of the methanol reformer; in addition, a water return port is set at the bottom of the shell and connected to the water tank, so that the condensed water generated during the reaction process can be further recycled.

Furthermore, the point source fractal network structure is a "Y" type fractal network structure.

The point source fractal network structure is set to a "Y" shape in order to carry out the catalytic reaction more fully, further expand the heat release effect, and enable the internal temperature of the methanol reformer to quickly increase; for the methanol steam reforming unit, "Y" The fractal network structure can make the evaporation reaction more complete and further improve the hydrogen production efficiency.

Further, the parameters of the "Y" type fractal network structure satisfy the following relationship:

l _k ＝l ₀ α ^k (1)

w _k =w ₀ β ^k (2)

Among them, l _k is the length of the kth stage of the fractal flow channel, l ₀ is the length of the 0th stage of the fractal flow channel, w _k is the width of the kth stage of the fractal flow channel, w ₀ is the 0th level of the fractal flow channel The width of the flow channel, S is the reaction area of the flow channel, α, β, and m are the characteristic parameters of the fractal network structure, which are the length ratio, width ratio and bifurcation series respectively, where α is the k+1th level and the kth level. The ratio of channel lengths, β is the ratio of the k+1-th level to the k-th level channel width, representing the iteration parameters in the growth process of the fractal network, and m represents the growth scale of the fractal network.

Through this fractal network structure, the outer surface area of the reformer can be reduced to 1/3 of the traditional straight flow channel or serpentine flow channel, which greatly reduces the heat dissipation area and can better preserve heat, thereby improving energy utilization. In addition, , due to the unique transport characteristics of the fractal flow channel, the upper limit of the ability of this type of reformer to convert methanol aqueous solution at 100% conversion rate is 2-3 times that of the traditional reformer, and has great engineering application potential.

Further, the methanol catalytic combustion unit and the methanol steam reforming unit have an integral cylindrical structure, and the integral cylindrical structure is installed inside the condensation unit along the central axis of the reformer housing.

Set as a whole, it is easy to install and disassemble, while reducing energy loss during heat transfer, further improving energy utilization and speeding up the device start-up time.

Further, the inlet of the methanol catalytic combustion unit is opposite to the inlet of the methanol steam reforming unit.

The inlets are set in opposite directions to couple the high-temperature area of the methanol catalytic combustion unit with the low-temperature area of the methanol steam reforming unit, thereby increasing the temperature gradient and enhancing heat transfer.

Further, the condensation unit has a spiral baffle structure and is installed on the inner wall of the reformer housing.

A condensation unit with a spiral baffle structure is installed on the inner wall of the methanol reformer shell to further release heat from the high-temperature gas, improve energy utilization and reduce energy loss.

Further, the spiral baffle of the condensation unit is coated with a CO selective oxidation catalyst.

The hydrogen and other gases generated after the methanol solution is evaporated are further oxidized in the condensation unit to purify the reformed gas, remove trace amounts of CO gas, and are finally led to the shell outlet and supplied to the external load.

Further, a methanol servo motor peristaltic pump and a methanol mass flow meter are respectively provided on the pipeline between the methanol solution preparation box and the methanol fuel tank; a servo motor is provided on the pipeline between the methanol solution preparation tank and the water tank. A motor peristaltic water pump and a pure water mass flow meter are provided. A solution servo motor peristaltic pump and a solution mass flow meter are provided between the methanol solution preparation box and the methanol steam reforming unit.

By installing corresponding flow meters in each pipeline, necessary data collection is provided to control the transportation of methanol fuel and the preparation and transportation of methanol solution; the corresponding peristaltic pump is installed to control the transportation of methanol fuel, methanol solution, and condensed water. Provide sufficient power for liquid circulation within the device.

A control method for a self-heating methanol reforming hydrogen production device based on fractal structure. The specific steps are as follows:

Step 1: System debugging, pre-calibrate the MAP diagram of the methanol-water molar ratio, methanol-water volume, and reaction temperature corresponding to the hydrogen production amount according to the hydrogen production amount;

Step 2: Determine the working condition parameters, fit the calibration working condition MAP in step 1 according to the actual hydrogen production demand, and obtain the points close to the calibrated working condition parameters to perform the preheating process and determine the methanol-to-water molar ratio, methanol Water volume and reaction temperature parameters;

Step 3: Preheating start. During cold start, the pure methanol in the methanol fuel tank is supplied to the fuel bubbler at a large flow rate and high pressure to the maximum extent for air mixing, and then supplied to the methanol catalytic combustion unit. Carry out a catalytic exothermic reaction, increase the temperature of the methanol reformer, and quickly reach around the reaction temperature determined in step two. When the reaction temperature determined in step two is reached, control the amount of pure methanol supplied to the methanol catalytic combustion unit to stabilize the reaction at this time. temperature reflex;

Step 4: Prepare the methanol solution, control the proportion and amount of methanol and pure water entering the methanol solution preparation box through the methanol servo motor peristaltic pump and the servo motor peristaltic water pump respectively, and monitor the current methanol and pure water in real time through the methanol mass flow meter and pure water mass flow meter. The proportion and volume of pure water entering the methanol solution preparation box. When the prepared solution volume can be maintained to meet the hydrogen production requirements for 30 seconds, the preparation will be terminated;

Step 5: Hydrogen production operation, supply the prepared solution to the methanol steam reforming unit according to the working condition point in the MAP diagram, monitor the output in real time through the mass flow meter, and monitor the solution quality in the methanol solution preparation box. When 30 seconds are met, hydrogen production Stop the deployment when there is demand, and start the deployment when it is only enough to meet the hydrogen production demand for 15 seconds;

Step 6: Recycle the reaction water. Calculate the current excess water mass based on the reaction parameters, and recycle the water produced by the reaction into the water tank;

Step 7. Switching of hydrogen production working conditions. When the hydrogen production working conditions need to be switched, when the reaction temperature changes, return to step three to re-control the temperature. When the demand for hydrogen production changes, the methanol solution preparation box will no longer reform the methanol steam. The unit supplies methanol solution, and after adjusting the methanol solution components in the methanol solution preparation box, the supply to the methanol steam reforming unit is resumed;

Step 8: Stop the machine, turn off the supply of methanol and pure water, and record the current molar ratio and the quality of the solution in the methanol solution preparation box. The fuel bubbler continues to supply the methanol catalytic combustion unit for 10 seconds, and purges the inside of the methanol catalytic combustion unit. , after the purging is completed, close the fuel bubbler to supply the methanol catalytic combustion unit, and recover the reaction water with high power;

Step 9: Improve the control system, collect and supplement the operating parameters of the above working conditions into the MAP diagram, and refine the working condition points through multiple iterative learning controls.

The complete workflow from solution preparation to hydrogen production can be completed through the above steps. The early process includes system debugging in step one and the determination of working conditions in step two; the mid-term process includes preheating start-up and methanol preparation in step three to step seven. Solution, hydrogen production operation, reaction water recovery, and switching of hydrogen production working conditions; the later process includes the shutdown of step eight and the improvement of the control system of step nine; the effect of rapid start-up of the device and enhanced energy utilization is achieved, and in the mid-term process Achieve working mode switching according to hydrogen production needs to meet working needs under multiple working conditions; in the later process, the working mode operating parameters are collected, and the working mode points are refined through multiple iterative learning controls, which can further improve the hydrogen production efficiency of the device .

Further, the preparation method of the methanol solution in steps four and seven is automatic preparation, and the specific control method is:

First, select position mode as the servo motor control method;

Define the required flow rate of methanol aqueous solution Q ml/min, the single pulse rotation angle θ of the servo motor, and the pump heads of the methanol servo motor peristaltic pump (41) and servo motor peristaltic water pump (51) can supply the flow rate Q _r ml after one rotation, then the single pulse supply The flow rate is Define the molar ratio of methanol solution:

Pulse number k, pulse frequency f, define methanol mass flow meter (42) flow rate Q _{m, ch3oh} g/min,

Pure water mass flow meter (52) flow rate Q _{m, h2o} g/min;

Secondly, establish a mapping model between the methanol solution demand flow Q, the methanol solution molar ratio α, and the pure methanol and water flow rates.

The constraints are:

1. The alcohol solution preparation speed must meet the hydrogen production demand of the hydrogen production device;

2. When the molar ratio of methanol solution is changed, it can respond quickly and prepare the corresponding proportion of fuel;

Establish the volume flow MAP diagram corresponding to the methanol solution demand flow Q, the allocated water flow Q _h2o , the allocated methanol flow Q _ch3oh , the pulse number k, and the pulse frequency f. The MAP diagram is fitted by multiple discrete points, and mass is introduced. Poor flow As the main objective function to control the accuracy of the deployment system, its value should be smaller than the graduation value of the mass flow meter, and PID control is carried out through the number of pulses and pulse frequency;

Then, the external hydrogen production demand is obtained through data collection, and the pulse number k ₃₁ and pulse frequency f ₃₁ of the solution servo motor peristaltic pump (31) are obtained through MAP chart lookup table for control, and the methanol servo motor peristaltic pump (41) and servo motor peristaltic pump (41) are controlled. The pulse number and pulse frequency of the water pump (51) should be 1.3 to 2 times that of the solution servo motor peristaltic pump (31), and according to the methanol solution molar ratio formula α, the methanol servo motor peristaltic pump (41) and servo motor should be adjusted according to the deployment requirements. The peristaltic water pump (51) performs differential control of pulse number and pulse frequency respectively;

Finally, when changing the molar ratio of the methanol solution, integrate the mass flow rates of pure methanol, water, and methanol solution over the running time and make the difference to obtain Δm, which is the current remaining solution volume of the methanol solution preparation box (3);

When determining the target molar ratio of methanol solution, compare the target molar ratio with the current molar ratio, and use the simultaneous molar ratio formula and Δm can be used to obtain the current blended raw materials and their quality that need to be replenished. By controlling the pulse number and pulse frequency of the servo motor, the stable operating point is reached according to the MAP diagram after the raw material replenishment amount is met.

In the above steps, by selecting the position mode as the servo motor control method, a mapping model between the methanol solution demand flow Q, the methanol solution molar ratio α and the pure methanol and water flow rates is established, and constraints are added to the model, and the external flow rate is obtained through data collection. According to the demand for hydrogen production, the raw materials and their quality are calculated and obtained, and the raw materials are replenished by controlling the pulse number and pulse frequency of the servo motor until a stable working condition is reached, thereby realizing the automatic blending of the methanol solution.

Beneficial effects:

1. The present invention designs a self-heating methanol reformer based on a fractal network structure. Its unique heat and mass transport characteristics can be well applied to reactions such as methanol reforming that increase the volume. Its outer surface heat dissipation area is only the traditional 1/3 of the type, the upper limit of methanol aqueous solution conversion is also 2-3 times higher, which means that this type of methanol reformer has higher energy utilization and hydrogen production performance. In addition, because of its fractal network structure, it can effectively Avoid problems such as flow channel blockage caused by catalyst falling off.

2. A spiral baffle is designed on the inner wall of the methanol reformer shell, integrating the two functions of CO selective oxidation and reformed gas condensation, reducing CO concentration, reusing condensed water, and improving the quality of exported hydrogen.

3. The present invention uses a servo motor peristaltic pump to realize the automatic deployment of methanol solution in the system, and the control strategy based on the number of pulses and pulse frequency can achieve high-precision control of the molar ratio and volume of methanol to water, reducing human-computer interaction. The process can be run intelligently offline.

4. Use iterative learning control algorithm to control the temperature of the methanol reformer, refine the system temperature control span, and reduce the generation of CO from the root cause.

Description of the drawings

Figure 1 is a schematic diagram of the system of the self-heating methanol reforming hydrogen production device of the present invention;

Figure 2 is a schematic diagram of the internal structure of the self-heating methanol reformer of the present invention;

Figure 3 is a schematic structural diagram of the internal condensation unit of the self-heating methanol reformer of the present invention;

Figure 4 is a schematic structural diagram of the methanol steam reforming unit and methanol catalytic combustion unit inside the self-heating methanol reformer of the present invention;

Figure 5 is a cross-sectional view of the methanol steam reforming unit and the methanol catalytic combustion unit A-A and B-B of the present invention;

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

As shown in Figures 1, 2 and 3, a self-heating methanol reforming hydrogen production device based on a fractal structure includes a shell 1, a methanol reformer 2, a methanol solution preparation tank 3, a methanol fuel tank 4, a water tank 5 and Fuel bubbler 6; the methanol reformer 2, methanol solution preparation tank 3, methanol fuel tank 4, water tank 5 and fuel bubbler 6 are respectively located inside the housing, and the methanol reformer 2 bubbles the fuel through The methanol reformer 6 is connected to the methanol fuel tank 4, the methanol reformer 2 is connected to the methanol solution preparation tank 3 and the water tank 5 respectively, the methanol solution preparation tank 3 is connected to the methanol fuel tank 4 and the water tank 5 respectively, the methanol reformer 2 is connected to the methanol fuel tank 4 and the water tank 5 respectively. The reformer 2 includes a reformer housing 21, a methanol catalytic combustion unit 22, a methanol steam reforming unit 23 and a condensation unit 24;

The methanol catalytic combustion unit 22 and the methanol steam reforming unit 23 are in a back-to-back stacked structure and are installed inside the condensation unit 24 along the central axis direction of the reformer housing 21;

The methanol catalytic combustion unit 22 is provided with a point source fractal network structure flow channel with a central axis diverging in the radial direction; the methanol steam reforming unit 23 is provided with a point source fractal structure with a central axis diverging in the radial direction. Network structure flow channel; the methanol catalytic combustion unit 22 and the methanol steam reforming unit 23 are not connected internally;

The outlets of the methanol catalytic combustion unit 22 and the methanol steam reforming unit 23 are facing the condensation unit 24 and do not exceed the scope of the condensation unit 24;

The fuel bubbler 6 is connected to the flow channel inlet of the methanol catalytic combustion unit 22; the methanol solution preparation box 3 is connected to the flow channel inlet of the methanol steam reforming unit 23;

A hydrogen gas output port 25 is provided above the reformer housing 21 , and a water return port 26 is provided at the bottom of the reformer housing 21 . The water return port 26 is connected to the water tank 5 .

The present invention adopts a self-heating method to quickly heat the methanol reformer. The methanol catalytic combustion unit 22 and the methanol steam reforming unit 23 are in a back-to-back stacked structure, and the heat transfer efficiency is higher; among which the methanol catalytic combustion unit 22 and the methanol steam reforming unit are in a back-to-back stacked structure. The reaction channel in unit 23 is set as a point source fractal network structure flow channel that diverges from the central axis in the radial direction, which improves the thermal coupling between the catalytic combustion of methanol and the steam reforming reaction, strengthens its heat and mass transport process, and significantly Improve heat transfer efficiency, reduce energy loss, and improve start-up efficiency; after entering the fractal network flow channel, the fuel first hits and avoids and then radiates and spreads around, showing a gradual expansion trend, which has a greater impact on volume increase reactions such as methanol reforming. Advantages; a condensation unit 24 is also provided, and the heat released during the condensation process can maintain the internal temperature of the methanol reformer 2; in addition, a water return port 26 is provided at the bottom of the shell 21 and connected to the water tank 5, which can control the heat generated during the reaction. The condensed water is further recycled.

As shown in Figure 4, the point source fractal network structure is a "Y" type fractal network structure.

The parameters of the "Y" type fractal network structure satisfy the following relationship:

l _k ＝l ₀ α ^k (1)

w _k =w ₀ β ^k (2)

Among them, l _k is the length of the kth stage of the fractal flow channel, l ₀ is the length of the 0th stage of the fractal flow channel, w _k is the width of the kth stage of the fractal flow channel, w ₀ is the 0th level of the fractal flow channel The width of the flow channel, S is the reaction area of the flow channel, α, β, and m are the characteristic parameters of the fractal network structure, which are the length ratio, width ratio and bifurcation series respectively, where α is the k+1th level and the kth level. The ratio of channel lengths, β is the ratio of the k+1-th level to the k-th level channel width, representing the iteration parameters in the growth process of the fractal network, and m represents the growth scale of the fractal network.

Through this fractal network structure, the outer surface area of the reformer can be reduced to 1/3 of the traditional straight flow channel or serpentine flow channel, which greatly reduces the heat dissipation area and can better preserve heat, thereby improving energy utilization. In addition, , due to the unique transport characteristics of the fractal flow channel, the upper limit of the ability of this type of reformer to convert methanol aqueous solution at 100% conversion rate is 2-3 times that of the traditional reformer, and has great engineering application potential.

As shown in Figure 3, the methanol catalytic combustion unit 22 and the methanol steam reforming unit 23 have an integral cylindrical structure, and the integral cylindrical structure is installed inside the condensation unit 24 along the central axis of the reformer housing 21. .

Set as a whole, it is easy to install and disassemble, while reducing energy loss during heat transfer, further improving energy utilization and speeding up the device start-up time.

As shown in FIG. 2 , the inlet of the methanol catalytic combustion unit 22 is opposite to the inlet of the methanol steam reforming unit 23 .

The inlets are set in opposite directions to couple the high-temperature area of the methanol catalytic combustion unit 22 with the low-temperature area of the methanol steam reforming unit 23, thereby increasing the temperature gradient and enhancing heat transfer.

As shown in FIG. 5 , the condensation unit 24 has a spiral baffle structure and is installed on the inner wall of the reformer housing 21 .

A condensation unit 24 with a spiral baffle structure is provided on the inner wall of the methanol reformer housing 21 to further dissipate heat from the high-temperature gas, thereby improving energy utilization and reducing energy loss.

The spiral baffle of the condensation unit 24 is coated with a CO selective oxidation catalyst.

The hydrogen and other gases generated after the methanol solution is evaporated are further oxidized in the condensation unit to purify the reformed gas, remove trace amounts of CO gas, and are finally led to the shell outlet and supplied to the external load.

As shown in Figure 1, a methanol servo motor peristaltic pump 41 and a methanol mass flow meter 42 are respectively provided on the pipeline between the methanol solution preparation tank 3 and the methanol fuel tank 4; the methanol solution preparation tank 3 and the water tank 5 A servo motor peristaltic water pump 51 and a pure water mass flow meter 52 are respectively provided on the pipelines between them. A solution servo motor peristaltic pump 31 and a solution mass flow meter are provided between the methanol solution preparation box 3 and the methanol steam reforming unit 23. 32.

By installing corresponding flow meters in each pipeline, necessary data collection is provided to control the transportation of methanol fuel and the preparation and transportation of methanol solution; the corresponding peristaltic pump is installed to control the transportation of methanol fuel, methanol solution, and condensed water. Provide sufficient power for liquid circulation within the device.

A control method for a self-heating methanol reforming hydrogen production device based on fractal structure. The specific steps are as follows:

Step 1: System debugging, pre-calibrate the MAP diagram of the methanol-water molar ratio, methanol-water volume, and reaction temperature corresponding to the hydrogen production amount according to the hydrogen production amount;

Step 2: Determine the working condition parameters, fit the calibration working condition MAP in step 1 according to the actual hydrogen production demand, and obtain the points close to the calibrated working condition parameters to perform the preheating process and determine the methanol-to-water molar ratio, methanol Water volume and reaction temperature parameters;

Step 3: Preheating start. During cold start, the pure methanol in the methanol fuel tank 4 is supplied to the fuel bubbler 6 at a large flow rate and high pressure to the greatest extent for air mixing, and then is supplied to the catalytic combustion of methanol. A catalytic exothermic reaction is carried out in the unit 22 to increase the temperature of the methanol reformer 2 and quickly reach around the reaction temperature determined in step 2. When the reaction temperature determined in step 2 is reached, the amount of pure methanol supplied to the methanol catalytic combustion unit 22 is controlled. To stabilize the reaction temperature at this time;

Step 4: Prepare the methanol solution, control the proportion and amount of methanol and pure water entering the methanol solution preparation box 3 through the methanol servo motor peristaltic pump 41 and the servo motor peristaltic water pump 51 respectively, and use the methanol mass flow meter 42 and the pure water mass flow meter 52 Monitor the current proportion and volume of methanol and pure water entering the methanol solution preparation box 3 in real time. When the prepared solution volume can maintain the hydrogen production requirement for 30 seconds, the preparation will be terminated;

Step 5: Hydrogen production operation, supply the prepared solution to the methanol steam reforming unit 23 according to the working condition point in the MAP diagram, monitor the output in real time through the mass flow meter, and monitor the solution quality in the methanol solution preparation box 3. When 30 seconds are met, Stop the deployment when there is demand for hydrogen production, and start the deployment when it is only enough to meet the demand for hydrogen production for 15 seconds;

Step 6: Recycle the reaction water. Calculate the current excess water mass according to the reaction parameters, and recycle the water produced by the reaction into the water tank 5;

Step 7: Switching of hydrogen production working conditions. When the hydrogen production working conditions need to be switched, return to step 3 to re-control the temperature when the reaction temperature changes. When the demand for hydrogen production changes, the methanol solution preparation box 3 will no longer reheat the methanol steam. The whole unit 23 supplies methanol solution, and after adjusting the methanol solution components in the methanol solution preparation box 3, the supply to the methanol steam reforming unit 23 is resumed;

Step 8: Stop the machine, turn off the supply of methanol and pure water, and record the current molar ratio and the quality of the solution in the methanol solution preparation box 3. The fuel bubbler 6 continues to supply the methanol catalytic combustion unit 22 for 10 seconds, and the methanol catalytic combustion unit 22 is The interior is purged, and after the purging is completed, the fuel bubbler 6 is closed to supply the methanol catalytic combustion unit 22, and the reaction water is recovered with high power;

Step 9: Improve the control system, collect and supplement the operating parameters of the above working conditions into the MAP diagram, and refine the working condition points through multiple iterative learning controls.

The complete workflow from solution preparation to hydrogen production can be completed through the above steps. The early process includes system debugging in step one and the determination of working conditions in step two; the mid-term process includes preheating start-up and methanol preparation in step three to step seven. Solution, hydrogen production operation, reaction water recovery, and switching of hydrogen production working conditions; the later process includes the shutdown of step eight and the improvement of the control system of step nine; the effect of rapid start-up of the device and enhanced energy utilization is achieved, and in the mid-term process Achieve working mode switching according to hydrogen production needs to meet working needs under multiple working conditions; in the later process, the working mode operating parameters are collected, and the working mode points are refined through multiple iterative learning controls, which can further improve the hydrogen production efficiency of the device .

The preparation method of the methanol solution in steps four and seven is automatic preparation, and the specific control method is:

First, select position mode as the servo motor control method;

Define the demand flow rate of methanol aqueous solution Q ml/min, the single pulse rotation angle of the servo motor θ, the pump head of the methanol servo motor peristaltic pump 41 and the servo motor peristaltic water pump 51 can supply the flow rate Q _r ml after one rotation, then the single pulse supply flow rate is Define the molar ratio of methanol solution:

The pulse number k and pulse frequency f define the methanol mass flowmeter as 42 flow rate Q _{m, ch3oh} g/min, and the pure water mass flow meter as 52 flow rate Q _{m, h2o} g/min;

Secondly, establish a mapping model between the methanol solution demand flow rate Q, the methanol solution molar ratio α, and pure methanol and water flow rates. The constraints are:

1. The alcohol solution preparation speed must meet the hydrogen production demand of the hydrogen production device;

2. When the molar ratio of methanol solution is changed, it can respond quickly and prepare the corresponding proportion of fuel;

Establish the volume flow MAP diagram corresponding to the methanol solution demand flow Q, the allocated water flow Q _h2o , the allocated methanol flow Q _ch3oh , the pulse number k, and the pulse frequency f. The MAP diagram is fitted by multiple discrete points, and mass is introduced. Poor flow As the main objective function to control the accuracy of the deployment system, its value should be smaller than the graduation value of the mass flow meter, and PID control is carried out through the number of pulses and pulse frequency;

Then, the external hydrogen production demand is obtained through data collection, and the pulse number k ₃₁ and pulse frequency f ₃₁ of the solution servo motor peristaltic pump 31 are obtained through MAP chart lookup table for control, and the pulses of the methanol servo motor peristaltic pump 41 and the servo motor peristaltic water pump 51 are obtained The number and pulse frequency should be 1.3 to 2 times that of the solution servo motor peristaltic pump 31, and according to the methanol solution molar ratio formula α, the pulse number and pulse frequency of the methanol servo motor peristaltic pump 41 and the servo motor peristaltic water pump 51 are determined according to the deployment requirements. differential control;

Finally, when the molar ratio of the methanol solution is changed, the mass flow rates of pure methanol, water, and methanol solution are integrated over the running time and the difference is Δm, which is the current remaining solution volume of the methanol solution preparation box 3;

When determining the target molar ratio of methanol solution, compare the target molar ratio with the current molar ratio, and use the simultaneous molar ratio formula and Δm can be used to obtain the current blended raw materials and their quality that need to be replenished. By controlling the pulse number and pulse frequency of the servo motor, the stable operating point is reached according to the MAP diagram after the raw material replenishment amount is met.

The methanol fuel tank 4 includes two outlets, which provide methanol fuel to the fuel bubbler 6 and the methanol solution preparation tank 3 respectively. An electronic peristaltic pump close to the fuel bubbler 6 pressurizes the methanol and sends it to the fuel bubbler. Bubbler 6, after mixing air into the methanol fuel, sends it to the methanol catalytic combustion unit 22 in the methanol reformer 2 for exothermic reaction, and another methanol outlet supplies pure methanol to the methanol solution preparation box 3 in a regular and quantitative manner for preparation. Methanol solution; the water tank 5 includes a water tank outlet and a water recovery inlet. The water tank outlet pressurizes water through a servo motor peristaltic water pump 51 and then supplies it regularly and quantitatively to the methanol solution preparation box 3 to prepare the methanol solution. The water recovery inlet is In order to realize the recovery and reuse of the condensed water in the methanol reformer 2, the condensed water is pressurized through the servo motor peristaltic water pump 51 and then connected to the water recovery inlet of the water tank; the methanol solution preparation box 3 includes a water inlet, a methanol inlet and a methanol solution supply. Outlet, wherein the methanol solution supply outlet is the only pipeline supplied to the reaction fuel of the methanol reformer 2, which is connected to the methanol solution supply inlet via a solution servo motor peristaltic pump and a solution mass flow meter;

The above-described embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-described implementations. Without departing from the essence of the present invention, any obvious improvements, substitutions or modifications that can be made by those skilled in the art can be made without departing from the essence of the present invention. All modifications belong to the protection scope of the present invention.

Claims (8)

1. A self-heating methanol reforming hydrogen production device based on a fractal structure, including a shell (1), a methanol reformer (2), a methanol solution preparation tank (3), a methanol fuel tank (4), and a water tank ( 5) and fuel bubbler (6); the methanol reformer (2), methanol solution preparation tank (3), methanol fuel tank (4), water tank (5) and fuel bubbler (6) are located respectively Inside the casing, the methanol reformer (2) is connected to the methanol fuel tank (4) through the fuel bubbler (6), and the methanol reformer (2) is connected to the methanol solution preparation tank (3) and the water tank respectively. (5) connection, the methanol solution preparation tank (3) is connected to the methanol fuel tank (4) and the water tank (5) respectively, characterized in that: the methanol reformer (2) includes a reformer housing (21 ), methanol catalytic combustion unit (22), methanol steam reforming unit (23) and condensation unit (24); The methanol catalytic combustion unit (22) and the methanol steam reforming unit (23) are in a back-to-back stacked structure and are installed inside the condensation unit (24) along the central axis of the reformer housing (21); The methanol catalytic combustion unit (22) is provided with a point source fractal network structure flow channel with a central axis diverging in the radial direction; the methanol steam reforming unit (23) is provided with a central axis diverging in the radial direction. Point source type fractal network structure flow channel; the methanol catalytic combustion unit (22) and the methanol steam reforming unit (23) are not connected internally; The outlets of the methanol catalytic combustion unit (22) and the methanol steam reforming unit (23) are facing the condensation unit (24) and do not exceed the scope of the condensation unit (24); The fuel bubbler (6) is connected to the flow channel inlet of the methanol catalytic combustion unit (22); the methanol solution preparation box (3) is connected to the flow channel inlet of the methanol steam reforming unit (23); A hydrogen output port (25) is provided above the reformer housing (21), and a water return port (26) is provided at the bottom of the reformer housing (21). The water return port (26) is connected to the water tank. (5) Connected; The point source fractal network structure is a "Y" type fractal network structure; The parameters of the "Y" type fractal network structure satisfy the following relationship: l _k ＝l ₀ α ^k (1) w _k =w ₀ β ^k (2) Among them, l _k is the length of the kth stage of the fractal flow channel, l ₀ is the length of the 0th stage of the fractal flow channel, w _k is the width of the kth stage of the fractal flow channel, w ₀ is the 0th level of the fractal flow channel The width of the flow channel, S is the reaction area of the flow channel, α, β, and m are the characteristic parameters of the fractal network structure, which are the length ratio, width ratio and bifurcation series respectively, where α is the k+1th level and the kth level. The ratio of channel lengths, β is the ratio of the k+1-th level to the k-th level channel width, representing the iteration parameters in the growth process of the fractal network, and m represents the growth scale of the fractal network. 2. The autothermal methanol reforming hydrogen production device based on fractal structure according to claim 1, characterized in that: the methanol catalytic combustion unit (22) and the methanol steam reforming unit (23) are integral cylinders structure, the integral cylindrical structure is installed inside the condensation unit (24) along the central axis direction of the reformer housing (21). 3. The autothermal methanol reforming hydrogen production device based on fractal structure according to claim 1 or 2, characterized in that: the inlet of the methanol catalytic combustion unit (22) and the methanol steam reforming unit (23) Entrances are set up relative to each other. 4. The self-heating methanol reforming hydrogen production device based on fractal structure according to claim 1, characterized in that: the condensation unit (24) has a spiral baffle structure and is installed in the reformer housing ( 21) On the inner wall. 5. The autothermal methanol reforming hydrogen production device based on fractal structure according to claim 4, characterized in that: the spiral baffle of the condensation unit (24) is coated with a CO selective oxidation catalyst. 6. The self-heating methanol reforming hydrogen production device based on fractal structure according to claim 1, characterized in that: the pipelines between the methanol solution preparation box (3) and the methanol fuel tank (4) are respectively equipped with There is a methanol servo motor peristaltic pump (41) and a methanol mass flow meter (42); the pipelines between the methanol solution preparation box (3) and the water tank (5) are respectively equipped with a servo motor peristaltic water pump (51) and a pure water pump (51). Water mass flow meter (52). A solution servo motor peristaltic pump (31) and a solution mass flow meter (32) are provided between the methanol solution preparation box (3) and the methanol steam reforming unit (23). 7. The control method of the autothermal methanol reforming hydrogen production device based on fractal structure according to claim 6, characterized in that the specific steps are as follows: Step 1: System debugging, pre-calibrate the MAP diagram of the methanol-water molar ratio, methanol-water volume, and reaction temperature corresponding to the hydrogen production amount according to the hydrogen production amount; Step 2: Determine the working condition parameters, fit the calibration working condition MAP in step 1 according to the actual hydrogen production demand, and obtain the points close to the calibrated working condition parameters to perform the preheating process and determine the methanol-to-water molar ratio, methanol Water volume and reaction temperature parameters; Step 3: Preheating start. During cold start, the pure methanol in the methanol fuel tank (4) is supplied to the fuel bubbler (6) at a large flow rate and high pressure to the maximum extent, and is then mixed with air. to the methanol catalytic combustion unit (22) to perform a catalytic exothermic reaction, increase the temperature of the methanol reformer (2), and quickly reach around the reaction temperature determined in step two. When the reaction temperature determined in step two is reached, pure methanol is controlled The amount supplied to the methanol catalytic combustion unit (22) is to stabilize the reaction temperature at this time; Step 4: Prepare the methanol solution. Control the proportion and amount of methanol and pure water entering the methanol solution preparation box (3) through the methanol servo motor peristaltic pump (41) and the servo motor peristaltic water pump (51). The methanol mass flow meter (42 ) and the pure water mass flow meter (52) monitor the current ratio and volume of methanol and pure water entering the methanol solution preparation box (3) in real time. When the prepared solution volume can be maintained to meet the hydrogen production requirements for 30 seconds of working time, the preparation is terminated; Step 5: Hydrogen production operation, supply the prepared solution to the methanol steam reforming unit (23) according to the working condition point in the MAP diagram, monitor the output in real time through the mass flow meter, and monitor the solution quality in the methanol solution preparation box (3) , stop the deployment when the hydrogen production demand is met for 30 seconds, and start the deployment when it is only enough to meet the hydrogen production demand for 15 seconds; Step 6: Recycle the reaction water, calculate the current mass of excess water according to the reaction parameters, and recycle the water produced by the reaction into the water tank (5); Step 7. Switching of hydrogen production working conditions. When the hydrogen production working conditions need to be switched, when the reaction temperature changes, return to step 3 to perform temperature control again. When the demand for hydrogen production changes, the methanol solution preparation box (3) will no longer supply methanol. The steam reforming unit (23) supplies methanol solution, and after adjusting the methanol solution components in the methanol solution preparation box (3), the supply to the methanol steam reforming unit (23) is resumed; Step 8. Stop the machine, turn off the supply of methanol and pure water, and record the current molar ratio and the quality of the solution in the methanol solution preparation box (3). The fuel bubbler (6) continues to supply the methanol catalytic combustion unit (22) for 10 seconds. Purge the inside of the methanol catalytic combustion unit (22), and after the purging is completed, close the fuel bubbler (6) to supply the methanol catalytic combustion unit (22), and recover the reaction water with high power; Step 9: Improve the control system, collect and supplement the operating parameters of the above working conditions into the MAP diagram, and refine the working condition points through multiple iterative learning controls. 8. The control method of the autothermal methanol reforming hydrogen production device based on the fractal structure according to claim 7, characterized in that the preparation method of the methanol solution in the step four and step seven is automatic preparation, and the specific control method is The method is: First, select position mode as the servo motor control method; Define the required flow rate of methanol aqueous solution Q ml/min, the single pulse rotation angle θ of the servo motor, and the pump heads of the methanol servo motor peristaltic pump (41) and servo motor peristaltic water pump (51) can supply the flow rate Q _r ml after one rotation, then the single pulse supply The flow rate is ml, define the molar ratio of methanol solution: Pulse number k, pulse frequency f, define methanol mass flow meter (42) flow rate Q _{m, ch3oh} g/min, Pure water mass flow meter (52) flow rate Q _{m, h2o} g/min; Secondly, establish a mapping model between the methanol solution demand flow Q, the methanol solution molar ratio α, and the pure methanol and water flow rates. The constraints are: 1. The alcohol solution preparation speed must meet the hydrogen production demand of the hydrogen production device; 2. When the molar ratio of methanol solution is changed, it can respond quickly and prepare the corresponding proportion of fuel; Establish the volume flow MAP diagram corresponding to the methanol solution demand flow Q, the allocated water flow Q _h2o , the allocated methanol flow Q _ch3oh , the pulse number k, and the pulse frequency f. The MAP diagram is fitted by multiple discrete points, and mass is introduced. Poor flow As the main objective function to control the accuracy of the deployment system, its value should be smaller than the graduation value of the mass flow meter, and PID control is carried out through the number of pulses and pulse frequency; Then, the external hydrogen production demand is obtained through data collection, and the pulse number k ₃₁ and pulse frequency f ₃₁ of the solution servo motor peristaltic pump (31) are obtained through MAP chart lookup table for control, and the methanol servo motor peristaltic pump (41) and servo motor peristaltic pump (41) are controlled. The pulse number and pulse frequency of the water pump (51) should be 1.3 to 2 times that of the solution servo motor peristaltic pump (31), and according to the methanol solution molar ratio formula α, the methanol servo motor peristaltic pump (41) and servo motor should be adjusted according to the deployment requirements. The peristaltic water pump (51) performs differential control of pulse number and pulse frequency respectively; Finally, when changing the molar ratio of the methanol solution, integrate the mass flow rates of pure methanol, water, and methanol solution over the running time and make the difference to obtain Δm, which is the current remaining solution volume of the methanol solution preparation box (3); When determining the target molar ratio of methanol solution, compare the target molar ratio with the current molar ratio, and use the simultaneous molar ratio formula and Δm can be used to obtain the current blended raw materials and their quality that need to be replenished. By controlling the pulse number and pulse frequency of the servo motor, the stable operating point is reached according to the MAP diagram after the raw material replenishment amount is met.