A structural optimization design method for a high-efficiency diesel hydrogen reformer

Abstract

The present invention discloses a method for optimizing the structure of a high-efficiency diesel hydrogen reformer, belonging to the technical field of reformer optimization design. The method comprises the steps of: establishing a multi-physics field model of the reformer in finite element software; determining the main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer; using the multi-physics field model to obtain the reforming conversion rate, H2 output rate, thermal efficiency, and CO output rate of the diesel hydrogen reformer under different structural parameters as performance evaluation indicators of the diesel hydrogen reformer, and selecting structural parameters that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen reformer and / or reduce the CO output rate. Based on the improvement of the heating structure of the existing reformer, the present invention analyzes the main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer, uses finite elements to establish a multi-physics field model, and optimizes the structural parameters of the improved reformer, thereby obtaining a diesel hydrogen reformer with a high reforming conversion rate.

Description

Technical Field

[0001] The present invention relates to the technical field of reformer structural optimization design, and in particular to a structural optimization design method for a high-efficiency diesel hydrogen production reformer. Background Art

[0002] Hydrogen energy is a representative clean energy source, boasting advantages over traditional energy sources such as low greenhouse gas emissions and high energy density. Fuel cells are one of the most efficient ways to utilize hydrogen. Solid oxide fuel cells (SOFCs), a relatively mature type of fuel cell technology, offer advantages such as high efficiency, cleanliness, high power generation efficiency, and fuel flexibility. They are considered a key development direction in the future energy sector. However, a major challenge restricting their application is the source, storage, and transportation of hydrogen. Diesel fuel has a high energy density and is easy to obtain and store. Using diesel fuel carried by the catalytic reaction in a diesel reformer for on-site hydrogen production is one of the most effective ways to obtain hydrogen for fuel cells.

[0003] The operating temperature of diesel hydrogen production is 600~800℃, which is higher than the temperature required by other fossil fuels. Therefore, a more reasonable arrangement of reformer heating tubes is needed to provide heat for the reforming reaction. Existing hydrogen production reformers mostly produce hydrogen by reforming fuels such as methane and propane. However, diesel is an ideal hydrogen production raw material that is more easily available. At present, most reformer designs use fuel combustion to provide heat for the reforming reaction, which will result in a low overall fuel utilization rate. In addition, the heater structure is mostly an external heating method, which has high heat loss and is difficult to meet the diesel reforming temperature requirements, resulting in a decrease in diesel reforming efficiency. The unsatisfactory heating structure of the reformer is the main reason for the reduction in diesel reforming efficiency. In order to improve the reforming efficiency of the diesel hydrogen production reformer, it is necessary to optimize the structure of the reformer, especially the heating structure of the reformer. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for optimizing the structure of a high-efficiency diesel hydrogen reformer.

[0005] The technical solution adopted in the present invention is:

[0006] The present invention provides a method for optimizing the structure of a high-efficiency diesel hydrogen production reformer, comprising the following steps:

[0007] S1. Establish a three-dimensional structural model of the diesel hydrogen reformer and import the three-dimensional structural model into the finite element analysis software. Set the physical parameters and assumptions required for the finite element simulation according to the actual operating conditions, set the governing equations for gas flow and heat transfer as well as the reforming reaction, and establish a multi-physics field model based on the coupling of mass transfer, porous medium heat transfer, and fluid heat transfer.

[0008] S2. Determine the main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer;

[0009] S3. Based on the structural parameters determined in step S2, the multi-physics field model established in step S1 is used to obtain the reforming conversion rate, H2 output rate, thermal efficiency, and CO output rate of the diesel hydrogen reformer under different structural parameters as performance evaluation indicators of the diesel hydrogen reformer; and the reforming conversion rate, H2 output rate, and CO output rate indicators obtained under different structural parameters are analyzed to select structural parameters that can increase the reforming conversion rate and H2 output rate and / or reduce the CO output rate of the diesel hydrogen reformer;

[0010] S4. Based on the three performance evaluation indicators of the diesel hydrogen reformer, namely, reforming conversion rate, H2 output rate, and thermal efficiency, a comprehensive performance evaluation factor is established to verify the comprehensive performance of the diesel hydrogen reformer under the structural parameters determined in step S3.

[0011] Furthermore, the three-dimensional structural model of the diesel hydrogen reformer in step S1 includes a reformer shell, a porous medium carrier for loading a catalyst arranged in the reformer shell, a plurality of heating gas pipes passing through the porous medium carrier, and an insulation layer sleeved on the outside of the reformer shell, and the inlet end of the porous medium carrier is used to input a mixed gas of diesel and superheated steam, and the outlet end of the porous medium carrier is used to output H2 and CO.

[0012] Furthermore, the assumptions set in the multi-physics model in step S1 include:

[0013] (a) The diesel fuel and superheated steam mixture is uniformly mixed before entering the reformer, and the superheated steam temperature has been preheated to the same temperature as the diesel fuel. The diesel fuel and superheated steam mixture enters the reformer in a gaseous state;

[0014] (b) The mixed reactant of diesel and superheated steam is an ideal gas, incompressible, and the flow state is steady laminar flow;

[0015] (c) Ignore the effect of gravity;

[0016] (d) Ignoring the effect of catalyst coating on the reforming reaction;

[0017] (e) Ignore thermal radiation during the reaction.

[0018] Furthermore, the main structural parameters affecting the reforming efficiency of the diesel hydrogen reformer in step S2 include:

[0019] The number of heating gas pipes n is used to adjust the heat exchange area of the mixed gas of heating gas, diesel and superheated steam;

[0020] The distribution distance d of the heating gas pipeline from the center of the reformer is used to adjust the heat transfer efficiency of the reformer;

[0021] The length of the heating gas pipeline L is used to adjust the convection heat exchange time of the mixed gas of the heating gas, diesel and superheated steam;

[0022] Whether baffles are installed in the porous medium carrier to adjust the reforming efficiency of the reformer.

[0023] Furthermore, the step S3 specifically includes:

[0024] S31. Setting different numbers of heating gas pipes n, and in the diesel hydrogen production multi-physics field model established in step S1, setting the total heat transfer area of the heating gas pipes to be the same, simulating and calculating the reforming conversion rate, H2 output rate, and CO output rate under different numbers of heating gas pipes, and selecting the number of heating gas pipes n that can improve the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0025] S32, setting different distribution distances d between the heating gas pipeline and the center of the reformer, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate at different distribution distances, and selecting the distribution distance d between the heating gas pipeline and the center of the reformer that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0026] S33, setting different heating gas pipeline lengths L, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate under different lengths L, and selecting a heating gas pipeline length L that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0027] S34. Use the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the diesel hydrogen production reformer with and without baffles, obtain the reforming conversion rate, H2 output rate, and CO output rate when the baffles are set and when the baffles are not set, and perform comparative analysis. If the reforming conversion rate and H2 output rate increase and / or the CO output rate decreases when the baffles are set, it means that the baffles can improve the reforming efficiency of the diesel hydrogen production reformer. Otherwise, there is no need to set the baffles.

[0028] Furthermore, the calculation formula of the comprehensive performance evaluation factor in step S4 is:

[0029] ;

[0030] in:

[0031] ;

[0032] ;

[0033] ;

[0034] Where, is a comprehensive performance evaluation factor, FUR is the reforming conversion rate, HPR is the H2 output rate, TE is the thermal efficiency, 、 、 are the weights of reforming conversion rate, H2 output rate and thermal efficiency in the comprehensive performance evaluation of diesel hydrogen reformer, and ; is the diesel inlet molar concentration, mol / m³; is the diesel outlet molar concentration, mol / m³; is the hydrogen outlet molar concentration, mol / m³; is the outlet molar concentration of carbon monoxide, mol / m³; is the lower heating value of hydrogen, kJ / mol; is the lower heating value of carbon monoxide, kJ / mol; Total heat input for heating gas.

[0035] The beneficial effects of the present invention are:

[0036] The present invention proposes a method for optimizing the structure of a high-efficiency diesel hydrogen production reformer. Based on the improvement of the heating structure of the existing reformer, the main structural parameters affecting the reforming efficiency of the diesel hydrogen production reformer are analyzed, and a multi-physical field model is established using finite elements to optimize the structural parameters of the improved reformer to obtain a diesel hydrogen production reformer with a high reforming conversion rate. In addition, the present invention also proposes a comprehensive performance evaluation factor for evaluating the comprehensive performance of the reformer, which is used to evaluate the comprehensive performance of the diesel hydrogen production reformer structure obtained by finite element simulation, that is, whether it can simultaneously maintain a high reforming conversion rate and a high thermal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 is a flow chart of the present invention;

[0039] Figure 2Schematic diagram of the structure of the reformer of the present invention;

[0040] Figure 3 for Figure 2 sectional view of

[0041] Figure 4 Schematic diagram of setting different numbers of heating gas pipes for the present invention;

[0042] Figure 5 Schematic diagram of the distribution distances of different heating gas pipelines from the center of the reformer according to the present invention;

[0043] Figure 6 The curves showing the change of reforming conversion rate and H2 production rate under different numbers of heating gas pipelines of the present invention are as follows;

[0044] Figure 7 The curves of the reforming conversion rate and H2 production rate at different distribution distances of the heating gas pipeline from the center of the reformer are shown in the present invention;

[0045] Figure 8 The curves showing the change of reforming conversion rate and H2 production rate under different heating gas pipeline lengths of the present invention are as follows;

[0046] Figure 9 This is a schematic diagram of the structure of the baffle plate provided in the reformer according to the present invention;

[0047] Figure 10 The figure shows the change curve of CO production rate when adding baffles or not.

[0048] Note in the figure:

[0049] 1. Reformer shell; 2. Porous medium carrier; 3. Heating gas pipeline; 4. Baffle. DETAILED DESCRIPTION

[0050] The present invention provides a method for optimizing the structure of a high-efficiency diesel hydrogen reformer. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described below. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0051] The present invention will be described in detail below with reference to the accompanying drawings.

[0052] This embodiment provides a method for optimizing the structure design of a high-efficiency diesel-to-hydrogen reformer, and based on this method, a diesel-to-hydrogen reformer structure with good comprehensive performance is determined.

[0053] Reference Figure 1 , the steps of the above optimization design method are as follows:

[0054] S1. Establish a three-dimensional structural model of the diesel hydrogen reformer and import the three-dimensional structural model into the finite element analysis software. Set the physical parameters and assumptions required for finite element simulation according to the actual working conditions, set the control equations for material transfer, heat transfer and reforming reaction, and establish a multi-physics field model based on the coupling of material transfer, porous medium heat transfer and fluid heat transfer.

[0055] Reference Figure 2 and Figure 3 In step S1, the three-dimensional structural model of the diesel hydrogen reformer includes a reformer shell 1, a porous medium carrier 2 for loading a catalyst disposed in the reformer shell 1, a plurality of heating gas pipes 3 penetrating the porous medium carrier, and an insulation layer sleeved on the outside of the reformer shell 1. The inlet end of the porous medium carrier is used to input a reactant mixed gas formed by a mixture of diesel and superheated steam, and the outlet end of the porous medium carrier is used to output H2 and CO. The heating gas pipes are used to introduce heating gas to increase the heat for the reforming reaction. The heating gas pipes and baffles are both made of 316L stainless steel.

[0056] In addition, the physical parameters set in the established multi-physics field model in step S1 mainly include:

[0057] Heating gas inlet temperature and inlet flow rate of the heating gas pipeline;

[0058] The inlet temperature and pressure difference of the reactant mixture gas in the porous medium carrier;

[0059] The substance type of the reactant gas mixture;

[0060] Porosity, heat capacity, and density of porous media carriers;

[0061] Materials of reformer shell and heating gas pipes.

[0062] The assumptions set in the multi-physics model in step S1 include:

[0063] (a) The diesel fuel and superheated steam mixture is uniformly mixed before entering the reformer, and the superheated steam temperature has been preheated to the same temperature as the diesel steam. The diesel fuel and superheated steam mixture enters the reformer in a gaseous state;

[0064] (b) The mixed reactant of diesel and superheated steam is an ideal gas, incompressible, and the flow state is steady laminar flow;

[0065] (c) Ignore the effect of gravity;

[0066] (d) Ignoring the effect of catalyst coating on the reforming reaction;

[0067] (e) Ignore thermal radiation during the reaction.

[0068] The reforming reactions involved in the multi-physics field model established in step S1 mainly include the following three types, and the specific reaction equations are as follows:

[0069] Reforming reaction (SR):

[0070] ;

[0071] Water Gas Shift (WGS):

[0072] ;

[0073] Methane Steam Reaction (MSR):

[0074] ;

[0075] The governing equations of material transfer and heat transfer involved in the multi-physics model established in step S1 mainly include:

[0076] The flow of gaseous substances through the porous media carrier in the reformer follows Darcy's law, that is:

[0077] ;

[0078] in, represents the gas density, Indicates viscosity, represents the permeability of the porous medium, represents the pressure in the reformer; and the inlet to outlet pressure drop is set to 50Pa; all other boundaries are impermeable;

[0079] For the heated gas flow within the heated gas duct, the Navier-Stokes governing equations and the continuity equation are used:

[0080] ;

[0081] ;

[0082] in, represents the gas velocity vector, represents the gas pressure, represents the fluid dynamic viscosity, represents the diffusion coefficient, Indicates gas density;

[0083] During the reforming reaction, diesel steam reforming follows the energy conservation equation:

[0084] ;

[0085] in, represents the constant pressure specific heat of the mixed gas, represents the thermal conductivity of the mixed gas, Indicates the heat source generated by the chemical reaction, is temperature;

[0086] ;

[0087] in, For the The reaction enthalpy of the reaction, For the The reaction rate of a reaction;

[0088] For reactants and products in porous media, the governing equation for concentrated species transport is used:

[0089] ;

[0090] in, For material The quality score of For material and substances The binary diffusion coefficient, For the The mass fraction of the substance, For the The mole fraction of a substance, is the generalized thermal diffusivity, which is set to 0. For material reaction rate.

[0091] S2. Determine the main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer.

[0092] The main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer in step S2 include:

[0093] The number of heating gas pipes n is used to adjust the heat exchange area of the mixed gas of heating gas, diesel and superheated steam;

[0094] The distribution distance d of the heating gas pipeline from the center of the reformer is used to adjust the heat transfer efficiency of the reformer;

[0095] The length of the heating gas pipeline L is used to adjust the convection heat exchange time of the mixed gas of the heating gas, diesel and superheated steam;

[0096] Whether baffles are installed in the porous medium carrier to adjust the reforming efficiency of the reformer.

[0097] S3. According to the structural parameters determined in step S2, the multi-physics field model established in step S1 is used to obtain the reforming conversion rate, H2 output rate, thermal efficiency, and CO output rate of the diesel hydrogen reformer under different structural parameters as performance evaluation indicators of the diesel hydrogen reformer; and the reforming conversion rate, H2 output rate, and CO output rate indicators under different structural parameters are analyzed to select structural parameters that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen reformer and / or reduce the CO output rate.

[0098] The step S3 specifically includes:

[0099] S31. Setting different numbers of heating gas pipes n, and in the diesel hydrogen production multi-physics field model established in step S1, setting the total heat transfer area of the heating gas pipes to be the same, simulating and calculating the reforming conversion rate, H2 output rate, and CO output rate under different numbers of heating gas pipes, and selecting the number of heating gas pipes n that can improve the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0100] S32, setting different distribution distances d between the heating gas pipeline and the center of the reformer, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate at different distribution distances, and selecting the distribution distance d between the heating gas pipeline and the center of the reformer that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0101] S33, setting different heating gas pipeline lengths L, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate under different lengths L, and selecting a heating gas pipeline length L that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate;

[0102] S34. Use the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the diesel hydrogen production reformer with and without baffles, obtain the reforming conversion rate, H2 output rate, and CO output rate when the baffles are set and when the baffles are not set, and perform comparative analysis. If the reforming conversion rate and H2 output rate increase and / or the CO output rate decreases when the baffles are set, it means that the baffles can improve the reforming efficiency of the diesel hydrogen production reformer. Otherwise, there is no need to set the baffles.

[0103] S4. Based on the three performance evaluation indicators of the diesel hydrogen reformer, namely, reforming conversion rate, H2 output rate, and thermal efficiency, a comprehensive performance evaluation factor is established to verify the comprehensive performance of the diesel hydrogen reformer under the structural parameters determined in step S3.

[0104] The specific steps of step S4 are: respectively calculating the comprehensive performance evaluation factors under the different structural parameters set in step S3, and judging whether the comprehensive performance evaluation factors under the optimal structural parameters determined in step S3 are the maximum value or close to the maximum value in the group; if so, it means that the structural parameters selected in step S3 have passed the verification, and the comprehensive performance of the reformer under the structural parameters is good; otherwise, it means that the structural parameters selected in step S3 have not passed the verification, and if they have not passed the verification, return to step S3 to continue optimizing the parameters.

[0105] The calculation formula of the comprehensive performance evaluation factor in step S4 is:

[0106] ;

[0107] in:

[0108] ;

[0109] ;

[0110] ;

[0111] Where, is a comprehensive performance evaluation factor, FUR is the reforming conversion rate, HPR is the H2 output rate, TE is the thermal efficiency, 、 、 are the weights of reforming conversion rate, H2 output rate and thermal efficiency in the comprehensive performance evaluation of diesel hydrogen reformer, and , weights are assigned by entropy method; is the diesel inlet molar concentration, mol / m³; is the diesel outlet molar concentration, mol / m³; is the hydrogen outlet molar concentration, mol / m³; is the outlet molar concentration of carbon monoxide, mol / m³; is the lower heating value of hydrogen, kJ / mol; is the lower heating value of carbon monoxide, kJ / mol; Total heat input for heating gas.

[0112] Specifically in this embodiment, in order to speed up the model calculation time, improve the solution efficiency and simplify the calculation model during the finite element simulation process, 1 / 2 is selected for calculation, and then the reforming condition of the entire reformer can be simulated through symmetrical boundary conditions.

[0113] Specifically in this embodiment, the diesel component is close to n-hexadecane, and n-hexadecane is used as the reactant. The reaction gas is a mixture of n-hexadecane and superheated steam, of which n-hexadecane accounts for 20% and water vapor accounts for 80%. The two are mixed evenly and enter the porous medium carrier after preheating. The inlet temperature is 700K and the pressure difference is 50pa. The inlet temperature of the heating gas in the heating gas pipeline is 900K and the inlet flow rate is 1m / s. The reaction gas and the heating gas flow in opposite directions. The porosity of the porous medium carrier is 0.25, the heat capacity is 2800J / (kg·K), and the density is 2000kg / m 3 The heating gas pipeline and the reformer shell are both made of 316L stainless steel. The diameter of the porous medium carrier is 30 mm, and the length of the porous medium carrier is 100 mm.

[0114] Reference Figure 4 In this embodiment, when determining the number n of heating gas pipes, n is set to 1, 4, 5, 6, or 8. When n is 1, the heating gas pipe is located at the center of the reformer; when n is 4, 5, 6, or 8, the heating gas pipes are evenly distributed around the center of the reformer. The diameter of the reformer is set to 0.3m, and the total heat transfer area of the heating gas pipes is set to be the same. When n is a different number, the diameter of the corresponding heating gas pipe changes. During the simulation process, the heating temperature is kept at 900K, the inlet velocity is 1m / s, and the heating gas and the reaction gas enter from the same side. The structures with five different numbers of pipes are studied respectively, and the distribution curves of the n-hexadecane reforming efficiency and hydrogen production rate under different n values are simulated and calculated to obtain, as shown below. Figure 6 As shown. Figure 6 The optimal channel range for a high-efficiency diesel reformer, chosen for its high diesel reforming efficiency and hydrogen production rate, is 5 to 8 channels. When the optimal number of channels is 5 to 8, the n-hexadecane conversion remains high and stabilizes. A comprehensive performance evaluation factor (FPI) was used to verify the performance of the reformer under different ranges of n. Calculations revealed that the FPI values were 0.648, 0.705, 0.694, 0.715, and 0.715, respectively. A larger FPI indicates better overall performance. When n is 5 to 8, the FPI values fall within a wide range, indicating that the reformer performs well when the number of channels is 5 to 8.

[0115] like Figure 5 As shown in the figure, in this embodiment, when determining the distribution distance d between the heating gas pipeline and the center of the reformer, the number of channels and the heat exchange area are set to remain unchanged, and the value of d is set to 15mm, 17.5mm, 20mm, 22.5mm, and 25mm. The reforming conversion rate and H2 production rate under different distribution distances d are shown as follows: Figure 7 As shown. Figure 7It can be seen that with the increase of d value, the reforming conversion rate and H2 output rate both show a trend of increasing first and then decreasing. When d reaches 17.5~22.5mm, the reforming conversion rate and H2 output rate are both within a large range, among which the n-hexadecane reforming conversion rate reaches more than 90%, and the hydrogen molar concentration is also the highest. The optimal range of d is 17.5~22.5mm. The comprehensive performance evaluation factor is used for verification. Through calculation, the values of the comprehensive performance evaluation factor are 0.698, 0.709, 0.722, 0.711, and 0.704, respectively. Among them, the d value is 17.5~22.5mm. The comprehensive performance evaluation factor values are all within a large range, indicating that the reformer performance under this structure is good.

[0116] In this embodiment, based on the determination of the optimal number of heating gas pipelines n and the optimal distribution distance d, the heating gas pipeline length L is further determined. The values of pipeline L are set to 0.1m, 0.125m, 0.15m, 0.175m, and 0.2m respectively. The reforming conversion rate and H2 output rate under different length values L are shown as follows: Figure 8 As shown. Figure 8 It can be seen that with the increase of L value, the reforming conversion rate and H2 output rate both show a trend of gradual increase. When the length reaches 0.15m, the n-hexadecane reforming rate reaches more than 98%. However, as the channel distance continues to increase, the reforming conversion rate does not change significantly. The optimal value range of the pipeline length L is 0.15~0.2m. The comprehensive performance evaluation factor is used for verification. Through calculation, the values of the comprehensive performance evaluation factor are 0.610, 0.683, 0.722, 0.723, and 0.723 respectively. Among them, when the pipeline length is 0.15~0.2m, the values of the comprehensive performance evaluation factor are all within a large range, indicating that the reformer performance under this structure is good.

[0117] like Figure 9 As shown, in this embodiment, a baffle structure is set in the reformer, specifically, two semicircular baffles 4 parallel to the end face of the reformer are set on the above-mentioned porous medium carrier, and the two baffles are arranged symmetrically about the center of the reformer. In order to verify the effect of adding baffles on the reforming performance of the diesel hydrogen reformer, this embodiment also selects a group of heating gas pipelines n, distribution distance d and length L within the optimal range determined above, and then only adds baffles, simulates and calculates the reforming conversion rate and H2 output rate. After simulation, whether or not to set the baffle has little effect on the reforming conversion rate and H2 output rate, so the CO output rate curve is obtained by simulation and compared, as shown Figure 10 As shown. Figure 10As can be seen from the figure, the CO concentration dropped from 2.7497 mol / m³ to 1.772 mol / m³ after adding the baffles, a 36% decrease. This indicates that adding baffles can effectively reduce carbon deposits in the reformer, improve reforming performance, and extend the reformer's service life. This was verified using a comprehensive performance evaluation factor. Calculations show that the comprehensive performance evaluation factors for the reformer without and with baffles are 0.722 and 0.731, respectively. The higher comprehensive performance evaluation factor with baffles indicates better reformer performance.

[0118] The molar concentration of CO above represents the degree of carbon deposition in the reformer. CO is a precursor to the formation of carbon. CO can form carbon (carbon deposits) through the mutual conversion between CO2 and carbon. Carbon dioxide does not directly form carbon, so high CO content is more likely to cause carbon deposition. Excessive carbon deposition can affect the heat and mass transfer of the reactor, reduce reaction efficiency, and even cause equipment damage. Therefore, during the diesel reforming process, the CO content must be controlled to reduce carbon deposition.

[0119] Based on the above simulation analysis, the structural parameters of the diesel hydrogen reformer, mainly the geometric parameters of the heating gas pipeline, are determined as follows:

[0120] The number n of heating gas pipes ranges from 5 to 8;

[0121] The distribution distance d between the heating gas pipeline and the center of the reformer is 17.5~22.5mm;

[0122] The length L of the heating gas pipeline is 0.15~0.2m;

[0123] Baffles are provided in the reformer.

[0124] Based on the above simulation analysis, the range of structural parameters that can achieve better comprehensive performance of the reformer has been screened out. In order to further determine the most specific values of the structure and seek the optimal solution of geometric parameters that can achieve the best performance of the reformer, on the basis of the above simulation analysis, the multi-objective optimization method is used to continue the simulation analysis to obtain the optimal structural parameters.

[0125] Specifically, this example utilizes a multi-objective optimization genetic algorithm to establish a multi-objective optimization model, primarily optimizing the structural parameters within the ranges of n = 5-8, d = 17.5-22.5 mm, and L = 0.15-0.2 m. The reforming conversion rate (FUR), H2 production rate (HPR), and thermal efficiency (TE) are used as evaluation indicators. This example employs three levels for each independent variable within the specified range, and the overall variance of the multiple independent variable combinations is set to 0.995, which indicates that the results of this combination design are reliable. The reforming conversion rate (FUR), H2 production rate (HPR), and thermal efficiency (TE) are then calculated for each group, along with the reformer comprehensive performance evaluation factor η, to comprehensively evaluate the reformer's heat exchange performance.

[0126] Through optimization, it is found that when η is the largest, the corresponding values are n=6, d=20mm, and L=0.2m.

[0127] The above results were simulated using a multi-physics model developed using finite element software developed in this example to verify the accuracy of the optimal structural parameters predicted by the multi-objective optimization model. Comparing the calculated results, the error in reforming conversion was 2.35%, the error in H₂ yield was 0.931%, and the error in thermal efficiency was 0.771%, indicating that the prediction model is accurate. The final determination was that the number of heating gas pipes, n, for the high-efficiency diesel reformer was 6, the distance d from the center of the pipes was 20.0 mm, and the heating gas pipe length, L, was 0.15 m.

[0128] Furthermore, when comparing the optimized internally heated reformer with a conventional externally heated reformer, η increased by 37.21%. By optimizing the reformer channel structure, not only did the diesel reforming conversion rate and hydrogen yield of the diesel reformer increase, but thermal efficiency was also significantly improved. This effectively addresses the low hydrogen production efficiency and low energy utilization efficiency of conventional reformers, significantly enhancing the overall performance of the reformer.

[0129] It should be noted that the parts not described in the present invention can be implemented by adopting or drawing on existing technologies.

[0130] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for optimizing the structure of a high-efficiency diesel hydrogen reformer, characterized in that: Including steps: S1. Establish a three-dimensional structural model of the diesel hydrogen reformer and import the three-dimensional structural model into the finite element analysis software. Set the physical parameters and assumptions required for the finite element simulation according to the actual operating conditions, set the governing equations for gas flow and heat transfer as well as the reforming reaction, and establish a multi-physics field model based on the coupling of mass transfer, porous medium heat transfer, and fluid heat transfer. S2. Determine the main structural parameters that affect the reforming efficiency of the diesel hydrogen reformer; S3. Based on the structural parameters determined in step S2, the multi-physics field model established in step S1 is used to obtain the reforming conversion rate, H2 output rate, thermal efficiency, and CO output rate of the diesel hydrogen reformer under different structural parameters as performance evaluation indicators of the diesel hydrogen reformer; and the reforming conversion rate, H2 output rate, and CO output rate indicators obtained under different structural parameters are analyzed to select structural parameters that can increase the reforming conversion rate and H2 output rate and / or reduce the CO output rate of the diesel hydrogen reformer; S4. Based on the three performance evaluation indicators of the diesel hydrogen reformer, namely, reforming conversion rate, H2 production rate, and thermal efficiency, a comprehensive performance evaluation factor is established to verify the comprehensive performance of the diesel hydrogen reformer under the structural parameters determined in step S3; The three-dimensional structural model of the diesel hydrogen reformer in step S1 includes a reformer shell, a porous medium carrier for supporting a catalyst disposed in the reformer shell, a plurality of heating gas pipes penetrating the porous medium carrier, and an insulation layer sleeved on the outside of the reformer shell, wherein the inlet end of the porous medium carrier is used to input a mixed gas of diesel and superheated steam, and the outlet end of the porous medium carrier is used to output H2 and CO; The governing equations of material transfer and heat transfer involved in the multi-physics field model established in step S1 mainly include: The flow of gaseous substances through the porous media carrier in the reformer follows Darcy's law, that is: Where ρ represents the gas density, η0 represents the viscosity, κ represents the permeability of the porous medium, and psr represents the pressure in the reformer. The pressure drop from the inlet to the outlet is set to 50 Pa. All other boundaries are impermeable. For the heated gas flow within the heated gas duct, the Navier-Stokes governing equations and the continuity equation are used: Where u represents the gas velocity vector, p represents the gas pressure, μ represents the fluid dynamic viscosity, I represents the diffusion coefficient, and ρ represents the gas density; During the reforming reaction, diesel steam reforming follows the energy conservation equation: Among them, C p represents the constant pressure specific heat of the mixed gas, f represents the thermal conductivity of the mixed gas, Q represents the heat source generated by the chemical reaction, and T is the temperature; Q=∑(-ΔH i ·r i ); Where ΔH i is the reaction enthalpy of the ith reaction, r i is the reaction rate of the i-th reaction; For reactants and products in porous media, the governing equation for concentrated species transport is used: Among them, ω j is the mass fraction of substance j; D j,k is the binary diffusion coefficient of species j and species k, ω k is the mass fraction of the kth substance, x k is the mole fraction of the kth substance, D T is the generalized thermal diffusion coefficient, which is set to 0, R j is the reaction rate of substance j; The main structural parameters affecting the reforming efficiency of the diesel hydrogen reformer in step S2 include: The number of heating gas pipes n is used to adjust the heat exchange area of the mixed gas of heating gas, diesel and superheated steam; The distribution distance d of the heating gas pipeline from the center of the reformer is used to adjust the heat transfer efficiency of the reformer; The length of the heating gas pipeline L is used to adjust the convection heat exchange time of the mixed gas of the heating gas, diesel and superheated steam; Whether baffles are provided in the porous medium carrier to adjust the reforming efficiency of the reformer; The step S3 specifically includes: S31. Setting different numbers of heating gas pipes n, and in the diesel hydrogen production multi-physics field model established in step S1, setting the total heat transfer area of the heating gas pipes to be the same, simulating and calculating the reforming conversion rate, H2 output rate, and CO output rate under different numbers of heating gas pipes, and selecting the number of heating gas pipes n that can improve the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate; S32, setting different distribution distances d between the heating gas pipeline and the center of the reformer, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate at different distribution distances, and selecting the distribution distance d between the heating gas pipeline and the center of the reformer that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate; S33, setting different heating gas pipeline lengths L, using the diesel hydrogen production multi-physics field model established in step S1 to simulate and calculate the reforming conversion rate, H2 output rate, and CO output rate under different lengths L, and selecting a heating gas pipeline length L that can increase the reforming conversion rate and H2 output rate of the diesel hydrogen production reformer and / or reduce the CO output rate; S34. Using the diesel hydrogen production multi-physics field model established in step S1, simulate and calculate the diesel hydrogen production reformer with and without baffles, obtain the reforming conversion rate, H2 output rate, and CO output rate when the baffles are provided and when the baffles are not provided, and perform a comparative analysis. If the reforming conversion rate and H2 output rate increase and / or the CO output rate decreases when the baffles are provided, it means that the baffles can improve the reforming efficiency of the diesel hydrogen production reformer. Otherwise, the baffles are not required. The simulation shows that adding baffles can effectively reduce carbon deposition in the reformer. The calculation formula of the comprehensive performance evaluation factor in step S4 is: η=α×FUR+β×HPR+γ×TE; in: Where η is the comprehensive performance evaluation factor, FUR is the reforming conversion rate, HPR is the H2 output rate, TE is the thermal efficiency, α, β, and γ are the weights of the reforming conversion rate, H2 output rate, and thermal efficiency in the comprehensive performance evaluation of the diesel hydrogen reformer, and α+β+γ=1. The weights are assigned by the entropy method. 柴油,in is the diesel inlet molar concentration; F 柴油,out is the diesel outlet molar concentration; is the molar concentration of hydrogen outlet; F CO,out is the outlet molar concentration of carbon monoxide; is the lower calorific value of hydrogen; Q CO,LHV is the lower calorific value of carbon monoxide; Q in Total heat input for heating gas.

2. The method for optimizing the structure of a high-efficiency diesel hydrogen reformer according to claim 1, characterized in that: The assumptions set in the multi-physics model in step S1 include: (a) The diesel fuel and superheated steam mixture is uniformly mixed before entering the reformer, and the superheated steam temperature has been preheated to the same temperature as the diesel fuel. The diesel fuel and superheated steam mixture enters the reformer in a gaseous state; (b) The mixed reactants of diesel and superheated steam are ideal gases, incompressible, and the flow state is steady laminar flow; (c) Ignore the effect of gravity; (d) Ignore the effect of catalyst coating on the reforming reaction; (e) Ignore thermal radiation during the reaction.

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