Foam reactor with hierarchical pore structure

Abstract

The invention provides a foam reactor with a hierarchical pore structure, which comprises a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores. The method comprises the following steps: S1, constructing a hierarchical pore foam reactor physical model; s2, designing a used reaction type based on the foam reactor, and constructing a reactor mathematical model; s3, calculating the influence of the research grade pore foam structure on the performance of the reactor by utilizing a fluid mechanics method corresponding to the reaction type; s4, obtaining the optimal structure parameters of the grade pore foam reactor matched with the heat exchange performance required by the reaction type; s5, based on the obtained structure parameters, the grade hole foam structure base body is precisely manufactured; and step S6, loading the reaction active site to the matrix with the grade hole foam structure. According to the invention, by regulating and controlling the skeleton shape and structure parameters, the collaborative reinforcement of convective heat transfer and mass transfer processes in the reactor is realized, and the performance reduction phenomenon caused by cold points or hot points in the reactor is inhibited.

Description

Technical Field

[0001] The invention relates to the technical field of reactor design, in particular to a foam reactor with a hierarchical pore structure. Background Art

[0002] In recent years, greenhouse gases have been emitted 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. Reactions such as methane dry reforming and carbon dioxide methanation are considered to be solutions to this problem. At present, fixed bed reactors are mainly used in industrial applications for gas reactions such as methane dry reforming and carbon dioxide methanation because their internal structures are relatively simple. However, when fixed bed reactors are used for strongly endothermic reactions similar to methane dry reforming or strongly exothermic reactions similar to carbon dioxide methanation, there are often "cold spots" or "hot spots" caused by untimely heat transfer. This is because the random stacking of catalyst particles inside the reactor will cause uneven distribution of porosity in the bed layer, forming heat transfer restricted areas, which seriously hinders the industrial application of these technologies. Fluidized bed reactors have violent internal particle collisions and complex fluidization phenomena, which makes it difficult to predict the particle flow, heat / mass transfer and reaction process in the reactor, and hinders the scale-up of engineering. Therefore, the development of a new reactor with a simple structure and uniform temperature distribution is a key issue that needs to be solved urgently.

[0003] The foam reactor is a new type of reactor. It not only has the simple structure of a fixed bed reactor and the excellent convective heat transfer performance of a fluidized bed reactor, but also has a high porosity and a porous network structure that extends in all directions. It can enhance 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. Due to its special structure, it can enhance the heat transfer process in the reactor, and at the same time improve the mass transfer performance, slow down the occurrence of "cold spots" or "hot spots", and make the temperature distribution inside the reactor uniform. However, most of the foam reactors currently studied have a uniform pore structure. This uniform pore structure will cause the performance of the foam reactor to be too extreme and cannot meet the requirements for synergistic enhancement of heat and mass transfer. Summary of the invention

[0004] The present invention proposes a foam reactor with a hierarchical pore structure. By regulating its skeleton shape and structural parameters, the synergistic enhancement of the convective heat transfer and mass transfer processes in the reactor is achieved, and the degradation of reactor performance caused by "cold spots" or "hot spots" in the reactor is suppressed. On this basis, 3D printing technology is used to achieve precise manufacturing of the hierarchical pore foam reactor.

[0005] The present invention adopts the following technical solutions.

[0006] A foam reactor with a hierarchical pore structure comprises a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores, wherein the coarse pores are used to enhance the mass transfer process in the reactor, and the fine pores are used to increase the convection heat exchange area to improve the heat transfer performance in the reactor.

[0007] A method for preparing a foam reactor having a hierarchical pore structure, wherein the process for preparing the hierarchical pore foam structure of the foam reactor comprises the following steps;

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

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

[0010] Step S3, using a fluid mechanics method corresponding to the reaction type to calculate and study the influence of the hierarchical pore foam structure on the reactor performance;

[0011] Step S4, obtaining the optimal structural parameters of the graded pore foam reactor that matches the heat exchange performance required by the reaction type;

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

[0013] Step S6: loading the reactive sites onto the matrix of the hierarchical pore foam structure.

[0014] Step S1 includes the following steps:

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

[0016] Step S1.2, connecting adjacent nodes, and using the connecting line as the central axis to generate a polygonal cylinder with a circular, triangular, or square cross section as a solid skeleton of the hierarchical pore foam;

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

[0018] In step S1.2, the coarse pores and fine pores of the hierarchical pore foam structure are integrally formed, and the structure is composed of the skeleton shape of the hierarchical pore foam structure and its rib diameter d rib , aperture ratio d coarse / d fine , pore volume fraction V fine / V tol Parameter control.

[0019] 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.

[0020] In step S2, the d of the graded pore foam structure coarse / d fine The V of the hierarchical pore foam structure is controlled by the diameter ratio of the two spheres of the spherical particles in step S1.1, which varies in the interval [1, ∞). fine / V tol The volume fraction of the pores in step S1.1 is controlled, and the ratio varies in the interval (0, 1].

[0021] In step S3, computational fluid dynamics methods are used to adjust the structural parameters of the hierarchical pore foam with the goal of maximizing the total heat transfer coefficient in the reactor to determine the optimal structural parameters.

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

[0023]

[0024] Among them A w，up is the wall area to which the heat flux is applied, T in is the inlet flow temperature, (T w ) upper and (T w ) lower are the temperatures of the upper and lower walls 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 calculating with the fluid mechanics method, the simulation settings of its 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; the specific situation is as follows Figure 2 shown.

[0026] After calculation, it was found that when the fine pore diameter is 0.635mm, the coarse pore diameter is 1.27mm, the pore volume ratio is 0.5, and the pore diameter ratio is 2, the overall heat transfer coefficient is better. The calculation results are as follows: Figure 3 , 4 , as shown in Figure 5.

[0027] In step S4, the foam reactor is used for DRM reaction, by regulating d coarse / d fine 、V fine / V tol The parameters are used to obtain the structural parameters whose total heat transfer performance meets the performance requirements, so as to avoid the degradation of reactor performance caused by cold spots or hot spots in the reactor with strong endothermic or exothermic properties due to uneven heating;

[0028] When testing the obtained structural parameters, the preparation of the graded pore foam reactor corresponding to the structural parameters was completed first, and then the performance was tested, the reaction temperature was set to 700 ° C, the inlet velocity was 1.0 m / s, and the feed molar ratio was The reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structural parameters are optimal parameters is determined based on the carbon conversion rate.

[0029] In step S5, 3D printing technology is used to achieve precise manufacturing of the hierarchical pore foam structure matrix. Metal oxide materials, including zirconium oxide and aluminum oxide, are used for printing. After the structural matrix is ​​precisely manufactured, it is degreased and calcined to obtain a hierarchical pore foam structure with high mechanical strength.

[0030] In step S6, the reaction active sites are loaded onto the matrix of the hierarchical pore foam structure by an impregnation method, thereby completing the preparation of the hierarchical pore foam reactor.

[0031] The present invention is suitable for the development of hierarchical pore foam reactors for strong endothermic or exothermic reactions, and has the following advantages compared with the prior art:

[0032] (1) Compared with the traditional fixed bed reactor, the foam reactor of the present invention 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 accuracy and efficiency;

[0033] (2) The foam reactor of the present invention combines the simple structure of a fixed bed reactor and the excellent convective heat transfer performance of a fluidized bed reactor, and at the same time has a high porosity and a porous network structure that extends in all directions, which can enhance the heat transfer behavior inside the reactor.

[0034] (3) Compared with the traditional foam structure, the hierarchical cell foam structure of the present invention can be obtained by adjusting its skeleton shape and rib diameter (d rib ), aperture ratio (d coarse / d fine ), pore volume fraction (V fine / V tol ) and other structural parameters can synergistically enhance the heat and mass transfer processes in the reactor;

[0035] (4) The present invention utilizes the relatively mature 3D printing technology at this stage, which can quickly realize the hierarchical pore foam structure from theoretical design to precise manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0038] Attached Figure 2 It is a schematic diagram of the foam structure generation diagram and the boundary conditions of the foam structure;

[0039] Attached Figure 3 It is a schematic diagram of the convective heat transfer results at different pore volume ratios and the convective heat transfer results at the same pump power;

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

[0041] Attached Figure 5 This is a schematic diagram of convective heat transfer results with different pore diameter ratios under the same pump work and the same pore volume ratio;

[0042] Attached Figure 6 This is a schematic diagram of the carbon conversion rate of the DRM reaction in reactors with different structures calculated based on experimental results;

[0043] Attached Figure 7 It is a schematic diagram of the internal structure of the foam reactor of the present invention. DETAILED DESCRIPTION

[0044] As shown in the figure, a foam reactor with a hierarchical pore structure is shown, wherein 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 exchange area to improve the heat transfer performance in the reactor.

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

[0046] Step S1, constructing a physical model of a hierarchical pore foam reactor;

[0047] Step S2, constructing a reactor mathematical model based on the reaction type for which the foam reactor is designed;

[0048] Step S3, using a fluid mechanics method corresponding to the reaction type to calculate and study the influence of the hierarchical pore foam structure on the reactor performance;

[0049] Step S4, obtaining the optimal structural parameters of the graded pore foam reactor that matches the heat exchange performance required by the reaction type;

[0050] Step S5, based on the obtained structural parameters, accurately manufacturing the hierarchical pore foam structure matrix;

[0051] Step S6: loading the reactive sites onto the matrix of the hierarchical pore foam structure.

[0052] Step S1 includes the following steps:

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

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

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

[0056] In step S1.2, the coarse pores and fine pores of the hierarchical pore foam structure are integrally formed, and the structure is composed of the skeleton shape of the hierarchical pore foam structure and its rib diameter d rib , aperture ratio d coarse / d fine , pore volume fraction V fine / V tol Parameter control.

[0057] 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.

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

[0059] In step S3, computational fluid dynamics methods are used to adjust the structural parameters of the hierarchical pore foam with the goal of maximizing the total heat transfer coefficient in the reactor to determine the optimal structural parameters.

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

[0061]

[0062] Among them A w，up is the wall area to which the heat flux is applied, T in is the inlet flow temperature, (T w )upper and (T w ) lower are the temperatures of the upper and lower walls 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;

[0063] When calculating with the fluid mechanics method, the simulation settings of its 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; the specific situation is as follows Figure 2 shown.

[0064] In this case, after calculation, it is found that when the fine pore diameter is 0.635mm, the coarse pore diameter is 1.27mm, the pore volume ratio is 0.5, and the pore diameter ratio is 2, the overall heat transfer coefficient is good. The calculation results are as follows: Figure 3 , 4 , as shown in Figure 5.

[0065] In this case, taking the DRM reaction as an example, a foam structure with coarse and fine pores is designed. coarse / d fine 、V fine / V tol The parameters are the same to obtain a structure with a more suitable overall heat transfer performance. When the DRM reaction is carried out at high temperature (>700℃), when the temperature is <700℃, the reaction formula is as follows:

[0066]

[0067]

[0068] In step S4, the foam reactor is used for DRM reaction, by regulating d coarse / d fine 、V fine / V tol The parameters are used to obtain the structural parameters whose total heat transfer performance meets the performance requirements, so as to avoid the degradation of reactor performance caused by cold spots or hot spots in the reactor with strong endothermic or exothermic properties due to uneven heating;

[0069] When testing the obtained structural parameters, the preparation of the graded pore foam reactor corresponding to the structural parameters was completed first, and then the performance was tested, the reaction temperature was set to 700 ° C, the inlet velocity was 1.0 m / s, and the feed molar ratio was The reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structural parameters are optimal parameters is determined based on the carbon conversion rate.

[0070] In step S5, 3D printing technology is used to achieve precise manufacturing of the hierarchical pore foam structure matrix. Metal oxide materials, including zirconium oxide and aluminum oxide, are used for printing. After the structural matrix is ​​precisely manufactured, it is degreased and calcined to obtain a hierarchical pore foam structure with high mechanical strength.

[0071] In step S6, the reaction active sites are loaded onto the matrix of the hierarchical pore foam structure by an impregnation method, thereby completing the preparation of the hierarchical pore foam reactor.

[0072] In this case, based on the above simulation results, the coarse hole diameter is 1.27mm, the fine hole diameter is 0.635mm, and the d coarse / d fine =2, V fine / V tol =0.5 hierarchical pore foam reactor. Using alumina as the substrate, the structural matrix was precisely manufactured using 3D printing technology, and then after degreasing and calcination, a hierarchical pore foam structure with high mechanical strength was obtained. The reactive active sites were loaded onto the structural matrix using the impregnation method to complete the preparation of the hierarchical pore foam reactor, and its performance was tested. The reaction temperature was set to 700℃, the inlet velocity was 1.0m / s, and the feed molar ratio was Collect the reactor outlet gas and analyze it to calculate the carbon conversion rate. The results are as follows: Figure 6 When the fine pore size is 0.635 mm, the coarse pore size is 1.27 mm, the pore volume ratio is 0.5, and the pore size 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 foam reactor with a hierarchical pore structure, characterized in that: The reactor comprises a hierarchical pore foam structure containing a large number of coarse pores and a large number of fine pores, wherein the coarse pores are used to enhance the mass transfer process in the reactor, and the fine pores are used to increase the convection heat exchange area to improve the heat transfer performance in the reactor.

2. A method for preparing a foam reactor having a hierarchical pore structure, characterized in that: The process for preparing the hierarchical cell foam structure of the foam reactor comprises the following steps; Step S1, constructing a physical model of a hierarchical pore foam reactor; Step S2, constructing a reactor mathematical model based on the reaction type for which the foam reactor is designed; Step S3, using a fluid mechanics method corresponding to the reaction type to calculate and study the influence of the hierarchical pore foam structure on the reactor performance; Step S4, obtaining the optimal structural parameters of the graded pore foam reactor that matches the heat exchange performance required by the reaction type; Step S5, based on the obtained structural parameters, accurately manufacturing the hierarchical pore foam structure matrix; Step S6: loading the reactive sites onto the matrix of the hierarchical pore foam structure.

3. The method for preparing a foam reactor having a hierarchical pore structure according to claim 2, characterized in that: In step S1, The steps include: Step S1.1, constructing a stacking structure of spherical particles with double spherical diameters, drawing a Voronoi diagram based on the stacking structure of the spherical particles, and obtaining three-dimensional coordinate data of the center of the sphere; Step S1.2, connecting adjacent nodes, and using the connecting line as the central axis to generate a polygonal cylinder with a circular, triangular, or square cross section as a solid skeleton of the hierarchical pore foam; Step S1.3, adjusting the structural shape of the structure obtained in step S1.2 to obtain a physical model of a graded pore foam reactor.

4. The method for preparing a foam reactor having a hierarchical pore structure according to claim 3, characterized in that: In step S1.2, the coarse pores and fine pores of the hierarchical pore foam structure are integrally formed, and the structure is composed of the skeleton shape of the hierarchical pore foam structure and its rib diameter d rib , aperture ratio d coarse / d fine , pore volume fraction V fine / V tol Parameter control.

5. The method for preparing a foam reactor having a hierarchical pore structure according to claim 4, 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.

6. The method for preparing a foam reactor having a hierarchical pore structure according to claim 3, characterized in that: In step S2, the d of the graded pore foam structure coarse / d fine The V of the hierarchical pore foam structure is controlled by the diameter ratio of the two spheres of the spherical particles in step S1.1, which varies in the interval [1, ∞). fine / V tol The volume fraction of the pores in step S1.1 is controlled, and the ratio varies in the interval (0, 1].

7. The method for preparing a foam reactor having a hierarchical pore structure according to claim 6, characterized in that: In step S3, computational fluid dynamics methods are used to adjust the structural parameters of the hierarchical pore foam with the goal of maximizing the total heat transfer coefficient in the reactor to determine the optimal structural parameters. The total heat transfer coefficient is calculated as follows: Among them A w，up is the wall area to which the heat flux is applied, T in is the inlet flow temperature, (T w ) upper and (T w ) lower are the temperatures of the upper and lower walls 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; When calculating with the fluid mechanics method, the simulation settings of 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.

8. The method for preparing a foam reactor having a hierarchical pore structure according to claim 6, characterized in that: In step S4, the foam reactor is used for DRM reaction, by regulating d coarse / d fine 、V fine / V tol The parameters are used to obtain the structural parameters whose total heat transfer performance meets the performance requirements, so as to avoid the degradation of reactor performance caused by cold spots or hot spots in the reactor with strong endothermic or exothermic properties due to uneven heating; When testing the obtained structural parameters, first complete the preparation of the graded hole foam reactor corresponding to the structural parameters, and then perform performance testing on it, setting the reaction temperature, inlet velocity, feed molar ratio Afterwards, the reactor outlet gas is collected and analyzed, the carbon conversion rate is calculated, and whether the structural parameters are optimal parameters is determined based on the carbon conversion rate.

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

10. The method for preparing a foam reactor having a hierarchical pore structure according to claim 6, characterized in that: In step S6, the reaction active sites are loaded onto the matrix of the hierarchical pore foam structure by an impregnation method, thereby completing the preparation of the hierarchical pore foam reactor.

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