A foam reactor having a hierarchical pore structure

Abstract

The application provides a foam reactor with hierarchical pore structure, which comprises a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores, and a preparation process comprising the following steps: step S1, constructing a physical model of the hierarchical pore foam reactor; step S2, constructing a mathematical model of the reactor based on a reaction type for which the foam reactor is designed; step S3, calculating and studying the influence of the hierarchical pore foam structure on the performance of the reactor by using a fluid mechanics method corresponding to the reaction type; step S4, obtaining optimal structure parameters of the hierarchical pore foam reactor which are suitable for the heat exchange performance required by the reaction type; step S5, performing accurate manufacturing of a hierarchical pore foam structure matrix based on the obtained structure parameters; and step S6, loading a reaction active site to the matrix of the hierarchical pore foam structure. By regulating the skeleton shape and structure parameters, the application realizes the synergistic enhancement of the convection heat transfer and mass transfer process in the reactor, and inhibits the performance decline phenomenon caused by cold spots or hot spots in the reactor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of reactor design, in particular to a foam reactor with hierarchical pore structure. BACKGROUND

[0002] In recent years, greenhouse gases are discharged in large quantities, among which carbon dioxide and methane are the main sources of greenhouse gases, which have a great impact on human health, climate change and other aspects, and the reactions such as dry reforming of methane and carbon dioxide methanation are considered to be a method to solve this problem. At present, the gas reactions such as dry reforming of methane and carbon dioxide methanation mainly use fixed bed reactors in industrial applications, because the internal structure is relatively simple. However, when the fixed bed reactor is used for strong endothermic reactions similar to dry reforming of methane or strong exothermic reactions similar to carbon dioxide methanation, there is often a problem of "cold spot" or "hot spot" caused by the delay of heat transfer, because the random accumulation form of catalyst particles in the reactor will make the void fraction distribution in the bed uneven, forming a heat transfer limited area, which seriously hinders the industrialization application of these technologies. The fluidized bed reactor is difficult to predict the particle flow, heat / mass transfer and reaction process in the reactor due to the violent collision of particles inside and the complex fluidization phenomenon, and the engineering scale-up is hindered. Therefore, developing a new type of reactor with simple structure and uniform temperature distribution is a key problem to be solved.

[0003] The foam reactor is a new type of reactor form, which not only has the simple structure of the fixed bed reactor and the excellent convective heat transfer performance of the fluidized bed reactor, but also has a high porosity and a porous network structure with four-way eight-way, which can strengthen the heat transfer behavior inside the reactor, and the designed foam structure matrix can be accurately printed by a 3D printer. The core part of the foam reactor is the internal foam structure, which can strengthen the heat transfer process in the reactor due to its special structure, and also can improve the mass transfer performance, slow down the generation of "cold spot" or "hot spot", and make the temperature distribution in the reactor uniform. However, most of the foam reactors studied at present are uniform pore structures, which will lead to the performance of the foam reactor being too extreme and unable to meet the requirements of heat transfer and mass transfer synergistic strengthening. SUMMARY

[0004] The present application proposes a foam reactor with hierarchical pore structure, which can realize the synergistic strengthening of convective heat transfer and mass transfer process in the reactor by adjusting the skeleton shape and structure parameters, and inhibit the performance decline of the reactor caused by "cold spot" or "hot spot", and on this basis, the 3D printing technology is used to realize the accurate manufacturing of the hierarchical pore foam reactor.

[0005] The present application adopts the following technical scheme.

[0006] A foam reactor with hierarchical pore structure, the reactor comprising a hierarchical pore foam structure containing a large number of macro-pores and a large number of micro-pores, the macro-pores being used to strengthen the mass transfer process in the reactor, and the micro-pores being used to increase the convective heat transfer area to improve the heat transfer performance in the reactor.

[0007] A method for preparing a foam reactor with hierarchical pore structure, the process for preparing the hierarchical pore foam structure of the foam reactor comprising the following steps:

[0008] Step S1, constructing a physical model of the hierarchical pore foam reactor;

[0009] Step S2, constructing a mathematical model of the reactor based on the reaction type for which the foam reactor is designed;

[0010] Step S3, calculating the influence of the hierarchical pore foam structure on the performance of the reactor using the corresponding fluid mechanics method for the reaction type;

[0011] Step S4, obtaining the optimal structure parameters of the hierarchical pore foam reactor that are suitable for the heat transfer performance required by the reaction type;

[0012] Step S5, based on the obtained structure parameters, accurately manufacturing the hierarchical pore foam structure matrix;

[0013] Step S6, loading the reaction active sites onto the matrix of the hierarchical pore foam structure.

[0014] In step S1, the following steps are included:

[0015] Step S1.1, constructing a packing structure of double-sphere-diameter spherical particles, drawing a Voronoi diagram based on the packing structure of spherical particles, and obtaining three-dimensional coordinate data of the sphere centers;

[0016] Step S1.2, connecting adjacent nodes to generate a column with a cross-section of a polygon such as a circle, triangle, or square as the solid skeleton of the hierarchical pore foam, with the connecting line as the central axis;

[0017] Step S1.3, adjusting the structure shape of the structure obtained in step S1.2 to obtain a physical model of the hierarchical pore foam reactor.

[0018] In step S1.2, the macro-pores and micro-pores of the hierarchical pore foam structure are integrally formed, and the structure is controlled by parameters such as the skeleton shape of the hierarchical pore foam structure and its rib diameter d rib , the pore diameter ratio d coarse / d fine , and the micro-pore volume fraction V fine / V tol .

[0019] The skeleton shape of the hierarchical porous foam structure matches the solid skeleton cross-sectional shape, which is circular or polygonal, and the rib diameter of the hierarchical porous foam structure is determined by the diameter of the skeleton column.

[0020] In step S2, the d coarse / d fine The V fine / V tol The volume fraction of the fine holes in step S1.1 is controlled, and the ratio varies in the interval (0, 1].

[0021] In step S3, the parameters of the hierarchical porous foam structure are adjusted to maximize the total heat transfer coefficient in the reactor using the computational fluid dynamics method.

[0022] The total heat transfer coefficient calculation formula is as follows:

[0023]

[0024] Where A w，up is the wall area of the applied heat flux, T in is the inlet flow temperature, (T w ) upper and (T w ) lower are the temperatures of the upper and lower wall surfaces of the sample, is the mass flow rate, C p represents the specific heat capacity of the fluid, T out is the average outlet temperature of the fluid, is the heat transfer rate to the fluid;

[0025] When the fluid mechanics method is calculated, the simulation of the boundary conditions is specifically set as follows: the inlet boundary is controlled by velocity, and the outlet boundary is controlled by pressure to improve the convergence of the model, and the inlet velocity under each structure is further determined by calculating the pump power-flow curve; a predetermined heat flux is applied to the upper wall as a boundary condition; the specific case is shown in Figure 2 .

[0026] After calculation, it is found that when the fine hole diameter is 0.635 mm, the coarse hole diameter is 1.27 mm, the hole volume ratio is 0.5, and the hole diameter ratio is 2, the total heat transfer coefficient is better, and the calculation results are shown in Figure 3 、 4 、5.

[0027] In step S4, the foam reactor is used for DRM reaction, and by adjusting the d coarse / d fine , V fineV tol The parameter obtains the structure parameter of the total heat transfer performance reaching the performance requirement, to avoid the cold spot or hot spot caused by uneven heating in the strong endothermic or strong exothermic reactor, to trigger the performance decline of the reactor;

[0028] In the test of the obtained structure parameter, the preparation of the graded hole foam reactor corresponding to the structure parameter is completed first, and then the performance test is carried out, the reaction temperature is set to 700 DEG C, the inlet velocity is 1.0 m / s, and the molar ratio of the feed is The reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structure parameter is the optimal parameter is determined according to the carbon conversion rate.

[0029] In step S5, the 3D printing technology is used to realize the accurate manufacturing of the graded hole foam structure matrix, the metal oxide material is used for printing, including zirconium oxide and aluminum oxide, after the accurate manufacturing of the structure matrix, the debinding and calcination are carried out, so that the graded hole foam structure with high mechanical strength is obtained.

[0030] In step S6, the reaction active site is loaded on the matrix of the graded hole foam structure by using the impregnation method, and the preparation of the graded hole foam reactor is completed.

[0031] The present application is suitable for the development of the graded hole foam reactor for strong endothermic or strong exothermic reaction, compared with the prior art, has the following advantages:

[0032] (1) Compared with the traditional fixed bed reactor, the foam reactor of the present application can be designed in detail according to the local conditions of the catalyst, providing multiple design freedoms such as diffusion length, reaction parameter configuration, fluid mechanics state, etc., with higher precision and efficiency;

[0033] (2) The foam reactor of the present application has the advantages of simple structure of fixed bed reactor and excellent convective heat transfer performance of fluidized bed reactor, and has high porosity and four-way eight-way porous network structure, which can strengthen the heat transfer behavior in the reactor.

[0034] (3) Compared with the traditional foam structure, the graded hole foam structure in the present application can synergistically strengthen the heat transfer and mass transfer process in the reactor by adjusting its skeleton shape and structural parameters such as rib diameter (d rib ), pore diameter ratio (d coarse / d fine ), fine pore volume fraction (V fine / V tol );

[0035] (4) The present application uses the 3D printing technology which is relatively mature at present, and can quickly realize the accurate manufacturing of the graded hole foam structure from theoretical design. BRIEF DESCRIPTION OF DRAWINGS

[0036]

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0037] Appendix Figure 1 This is a schematic diagram of the construction process of a foam structure;

[0038] Appendix Figure 2 These are diagrams showing the generation of foam structures and the boundary conditions of foam structures.

[0039] Appendix Figure 3 This is a schematic diagram showing the convective heat transfer results under different orifice volume ratios and the convective heat transfer results under the same pump power.

[0040] Appendix Figure 4 This is a schematic diagram illustrating the effect of different pore diameter ratios on convective heat transfer results under the same pore volume ratio;

[0041] Appendix Figure 5 This is a schematic diagram of convective heat transfer results with different orifice ratios under the same pump power and the same orifice volume ratio.

[0042] Appendix Figure 6 This is a schematic diagram showing the carbon conversion rate of the DRM reaction under different reactor structures, calculated based on experimental results.

[0043] Appendix Figure 7 This is a schematic diagram of the internal structure of the foam reactor of the present invention. Detailed Implementation

[0044] As shown in the figure, a foam reactor with a hierarchical pore structure is disclosed. The reactor includes a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores. The coarse pores are used to enhance the mass transfer process in the reactor, and the fine pores are used to increase the convective heat transfer area to improve the heat transfer performance in the reactor.

[0045] A method for preparing a foam reactor with a hierarchical pore structure, the process of preparing the hierarchical pore foam structure of the foam reactor includes the following steps;

[0046] Step S1: Construct a physical model of a hierarchical pore foam reactor;

[0047] Step S2: Based on the reaction type for which the foam reactor is designed, construct a mathematical model of the reactor;

[0048] Step S3: Calculate the effect of hierarchical pore foam structure on reactor performance using the fluid dynamics method corresponding to the reaction type;

[0049] Step S4: Obtain the optimal structural parameters of the graded porous foam reactor that are compatible with the heat exchange performance required for the reaction type.

[0050] Step S5: Based on the obtained structural parameters, precisely manufacture the hierarchical pore foam structure matrix;

[0051] Step S6, loading the reaction active sites to the matrix of hierarchical porous foam structure.

[0052] In step S1, the following steps are included;

[0053] Step S1.1, constructing the packing structure of double-sphere diameter spherical particles, drawing a Voronoi diagram based on the packing structure of spherical particles, and obtaining the three-dimensional coordinate data of the sphere centers;

[0054] Step S1.2, connecting adjacent nodes to generate a column with a circular, triangular, or square cross-section as the solid skeleton of the hierarchical porous foam, with the connecting line as the central axis;

[0055] Step S1.3, adjusting the structure shape of the structure obtained in step S1.2 to obtain a physical model of the hierarchical porous foam reactor.

[0056] In step S1.2, the macro-pores and micro-pores of the hierarchical porous foam structure are integrally formed, and the structure is determined by the skeleton shape of the hierarchical porous foam structure and the rib diameter d rib , the pore diameter ratio d coarse / d fine , and the micro-pore volume fraction V fine / V tol .

[0057] The skeleton shape of the hierarchical porous foam structure matches the cross-sectional shape of the solid skeleton, which is circular or polygonal, and the rib diameter of the hierarchical porous foam structure is determined by the diameter of the skeleton column.

[0058] In step S2, the d coarse / d fine of the hierarchical porous foam structure is controlled by the ratio of the two sphere diameters of the spherical particles in step S1.1, which varies in the interval [1, ∞), and the V fine / V tol of the hierarchical porous foam structure is controlled by the volume fraction of the micro-pores in step S1.1, which varies in the interval (0, 1].

[0059] In step S3, the computational fluid dynamics method is used to control the parameters of the hierarchical porous foam structure to determine the optimal structure parameters, with the maximum total heat transfer coefficient in the reactor as the target.

[0060] The total heat transfer coefficient calculation formula is as follows:

[0061]

[0062] where A w，up is the wall area of the applied heat flux, T in is the inlet flow temperature, and (T w )upper and (T w ) lower are the temperature of the upper and lower wall of the sample, respectively, is the mass flow rate, C p represents the specific heat capacity of the fluid, T out is the average outlet temperature of the fluid, is the heat transfer rate to the fluid;

[0063] When the fluid mechanics method is calculated, the simulation of the boundary conditions is specifically set as follows: the inlet boundary is controlled by velocity, and the outlet boundary is controlled by pressure, so as to improve the convergence of the model, and the inlet velocity under each structure is further determined by calculating the pump power-flow curve; a predetermined heat flux is applied to the upper wall as a boundary condition; and specific conditions are shown in Figure 2 .

[0064] In this example, it is found through calculation that when the fine hole diameter is 0.635 mm, the coarse hole diameter is 1.27 mm, the hole volume ratio is 0.5, and the hole diameter ratio is 2, the total heat transfer coefficient is better, and the calculation results are shown in Figure 3 、 4 , and 5.

[0065] In this example, taking the DRM reaction as an example, a foam structure with integrated coarse and fine holes is designed, and by adjusting d coarse / d fine , V fine / V tol and other parameters, a structure with relatively suitable total heat transfer performance is obtained. When the DRM reaction is carried out at high temperature (> 700℃), at a temperature < 700℃, the reaction formula is as follows:

[0066]

[0067]

[0068] In step S4, the foam reactor is used for DRM reaction, and by adjusting d coarse / d fine , V fine / V tol parameters, a structure parameter with total heat transfer performance reaching the performance requirement is obtained, so as to avoid the performance decline of the reactor caused by cold spots or hot spots due to uneven heating in the strong endothermic or strong exothermic reactor;

[0069] When the obtained structure parameters are tested, first, the preparation of the graded hole foam reactor corresponding to the structure parameters is completed, and then the performance test is carried out, the reaction temperature is set to 700℃, the inlet velocity is 1.0 m / s, and the feed mole ratio The reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structure parameter is the optimal parameter is determined according to the carbon conversion rate.

[0070] In step S5, the 3D printing technology is used to realize the accurate manufacturing of the hierarchical pore foam structure substrate. The printing uses metal oxide materials, including zirconium oxide and aluminum oxide. After the structure substrate is accurately manufactured, the substrate is subjected to debinding and calcination to obtain the hierarchical pore foam structure with high mechanical strength.

[0071] In step S6, the impregnation method is used to load the reaction active sites to the substrate of the hierarchical pore foam structure to complete the preparation of the hierarchical pore foam reactor.

[0072] In this example, according to the simulation results above, the hierarchical pore foam reactor with the coarse pore diameter of 1.27 mm, the fine pore diameter of 0.635 mm, d coarse / d fine = 2, and V fine / V tol = 0.5 is designed. The aluminum oxide is used as the substrate, and the 3D printing technology is used to accurately manufacture the structure substrate. Then, the substrate is subjected to debinding and calcination to obtain the hierarchical pore foam structure with high mechanical strength. The impregnation method is used to load the reaction active sites to the structure substrate to complete the preparation of the hierarchical pore foam reactor. The performance test is performed on the reactor, the reaction temperature is set to 700°C, the inlet velocity is set to 1.0 m / s, and the molar ratio of the feed is set to 1.0. The gas at the outlet of the reactor is collected and analyzed to calculate the carbon conversion rate. The results are shown in Figure 6 When the fine pore diameter is 0.635 mm, the coarse pore diameter is 1.27 mm, the pore volume ratio is 0.5, and the pore diameter ratio is 2, the carbon conversion rate of the hierarchical pore foam reactor is 79%, which is significantly higher than that of the fixed bed reactor and the uniform pore foam reactor.

Claims

1. A method for the production of a foam reactor with a hierarchical pore structure, characterized in that: The process of preparing a hierarchical pore foam structure for a foam reactor includes the following steps; Step S1: Construct a physical model of a hierarchical pore foam reactor; Step S2: Based on the reaction type for which the foam reactor is designed, construct a mathematical model of the reactor; Step S3: Calculate the effect of hierarchical pore foam structure on reactor performance using the fluid dynamics method corresponding to the reaction type; Step S4: Obtain the optimal structural parameters of the graded porous foam reactor that are compatible with the heat exchange performance required for the reaction type. Step S5: Based on the obtained structural parameters, precisely manufacture the hierarchical pore foam structure matrix; Step S6: Load reactive sites onto the hierarchical porous foam matrix; In step S1.2, the macro- and micro-pores of the hierarchical porous foam structure are integrally formed, and the structure is controlled by the parameters of the skeleton shape of the hierarchical porous foam structure and its rib diameter d rib , the pore diameter ratio d coarse / d fine , and the micro-pore volume fraction V fine / V tol ; In step S4, the foam reactor is used for the DRM reaction, and the d coarse / d fine , V fine / V tol The structure parameters are obtained to achieve the total heat transfer performance to meet the performance requirements, so as to avoid the cold spot or hot spot caused by uneven heating in the strong endothermic or exothermic reactor, thereby triggering the performance decline of the reactor. In the test of the obtained structure parameters, the preparation of the graded pore foam reactor corresponding to the structure parameters is completed first, and then performance test is carried out, the reaction temperature, the inlet velocity and the molar ratio of the feed are set Then, the reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structure parameters are the optimal parameters is determined according to the carbon conversion rate.

2. The method for preparing a foam reactor with a hierarchical pore structure according to claim 1, characterized in that: In step S1, Includes the following steps; Step S1.1: Construct the stacking structure of spherical particles with double diameters, draw the Volonoi diagram based on the stacking structure of the spherical particles, and obtain the three-dimensional coordinate data of the center of the spheres; Step S1.2: Connect adjacent nodes and generate polygonal columns with circular, triangular, or square cross-sections using the connecting lines as the central axis to serve as the solid skeleton of the graded pore foam; Step S1.3: Adjust the structural shape of the structure obtained in step S1.2 to obtain the physical model of the graded pore foam reactor.

3. The method for preparing a foam reactor with a hierarchical pore structure according to claim 1, characterized in that: The skeleton shape of the hierarchical pore foam structure matches the cross-sectional shape of the solid skeleton, which is circular or polygonal. The rib diameter of the hierarchical pore foam structure is determined by the diameter of the skeleton column.

4. The method for preparing a foam reactor with a hierarchical pore structure according to claim 2, characterized in that: In step S2, the d coarse / d fine By controlling the ratio of the diameters of the two spheres of the spherical particles in step S1.1, which varies in the interval [1,∞), the V fine / V tol By controlling the volume fraction of the fine pores in step S1.1, which varies in the interval (0,1], the V 5. The method for preparing a foam reactor with a hierarchical pore structure according to claim 4, characterized in that: In step S3, computational fluid dynamics is used to adjust the structural parameters of the graded pore foam with the goal of maximizing the total heat transfer coefficient in the reactor, and the optimal structural parameters are determined. The formula for calculating the overall heat transfer coefficient is as follows: Where A w，up It is the wall area to which the heat flux is applied, T in It is the inlet flow temperature, (T) w ) upper and (T) w ) lower These are the temperatures of the upper and lower walls of the sample, respectively. It is the mass flow rate, C p T represents the specific heat capacity of a fluid. out It is the average outlet temperature of the fluid. It is the heat transfer rate reaching the fluid; In the fluid dynamics calculation, the specific settings for the boundary conditions are as follows: the inlet boundary is controlled by velocity, and the outlet boundary is controlled by pressure to improve the convergence of the model. The inlet velocity under each structure is further determined by calculating the pump power-flow curve. A predetermined heat flux is applied to the upper wall as a boundary condition.

6. The method for preparing a foam reactor with a hierarchical pore structure according to claim 4, characterized in that: In step S5, 3D printing technology is used to precisely manufacture the hierarchical porous foam structure matrix. Metal oxide materials, including zirconium oxide and alumina, are used for printing. After the structural matrix is ​​precisely manufactured, it is degreased and calcined to obtain a hierarchical porous foam structure with high mechanical strength.

7. The method for preparing a foam reactor with a hierarchical pore structure according to claim 4, characterized in that: In step S6, the reactive sites are loaded onto the matrix of the hierarchical porous foam structure using an impregnation method to complete the preparation of the hierarchical porous foam reactor.

8. The method for preparing a foam reactor with a hierarchical pore structure according to claim 1, characterized in that: The preparation method uses a foam reactor with a hierarchical pore structure. The reactor includes a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores. The coarse pores are used to enhance the mass transfer process in the reactor, and the fine pores are used to increase the convective heat transfer area to improve the heat transfer performance in the reactor.

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