技术领域technical field
本发明涉及一种基于康托尔分形的填充床微反应器，属于填充床微反应器技术领域。The invention relates to a packed bed microreactor based on Cantor fractal, belonging to the technical field of packed bed microreactors.
背景技术Background technique
近年来，微流控涉及到生物和化学等领域，由此促进了微反应技术的研究。目前微反应技术激发了世界各地众多学者的兴趣，各式各样的新型微反应器层出叠现，为化学领域的发展带来了深远的影响。In recent years, microfluidics has been involved in the fields of biology and chemistry, thus promoting the research of microreaction technology. At present, micro-reaction technology has aroused the interest of many scholars around the world, and various new micro-reactors have emerged one after another, which has brought a profound impact on the development of the chemical field.
按照不同的分类方法，微反应器有多种类型。首先按照操作模式可分为连续微反应器、半连续微反应器和间歇微反应器。其次按微反应器的用途可分为生产微反应器和实验用微反应器两大类，其中实验用微反应器有对药物进行筛选、测试催化剂性能及工艺开发和优化等优点。从不同相态的反应方程角度出发，也可根据反应过程的不同划分微反应器的类型，反应物不同的相态决定了微反应器的结构，因此按照不同相态的反应类型，微反应器又可分为气固相催化微反应器、液液相微反应器、气液相微反应器和气液固三相催化微反应器等。According to different classification methods, there are many types of microreactors. First of all, according to the operation mode, it can be divided into continuous microreactor, semi-continuous microreactor and batch microreactor. Secondly, according to the use of microreactors, it can be divided into two categories: production microreactors and experimental microreactors. Among them, experimental microreactors have the advantages of screening drugs, testing catalyst performance, and process development and optimization. From the perspective of reaction equations of different phases, the types of microreactors can also be divided according to the different reaction processes. The different phases of reactants determine the structure of microreactors. Therefore, according to the reaction types of different phases, microreactors can be divided into gas-solid phase catalytic microreactors, liquid-liquid phase microreactors, gas-liquid phase microreactors, and gas-liquid-solid three-phase catalytic microreactors.
微反应器及其它微通道设备的微通道特征尺寸数量级是微米级。微反应器相对于大反应器具有反应空间小和非常大的表面积比的特点，在化学合成、化学动力学研究和工艺开发等领域具有广阔的应用前景。但是，现有微反应器的结构较为简单、单一。The microchannel feature size of microreactors and other microchannel devices is on the order of microns. Compared with large reactors, microreactors have the characteristics of small reaction space and very large surface area ratio, and have broad application prospects in the fields of chemical synthesis, chemical kinetics research, and process development. However, the structure of the existing microreactor is relatively simple and single.
发明内容Contents of the invention
本发明的目的是克服现有技术的上述不足，通过对微反应器的微通道进行分形研究，提供一种区别与现有微反应器结构的、基于康托尔分形的微反应器。The purpose of the present invention is to overcome the above-mentioned deficiency of prior art, by carrying out fractal research to the microchannel of microreactor, provide a kind of microreactor based on Cantor fractal that is different from existing microreactor structure.
为实现上述目的，本发明采用下述技术方案：To achieve the above object, the present invention adopts the following technical solutions:
基于康托尔分形的微反应器，包括微型微通道；所述微通道呈长方体形，其长度方向的两端开口，其纵向截面在其长度方向具有第一边和第二边；所述第一边和第二边均采用康托尔一次分形；所述第一边的康托尔一次分形与所述第二边的康托尔一次分形相向、对称、分形参数相同；The microreactor based on Cantor's fractal, comprising miniature microchannel; Described microchannel is cuboid, and the two ends of its length direction are open, and its longitudinal section has first side and second side in its lengthwise direction; Described first side and second side all adopt Cantor's first fractal; The Cantor's first fractal of described first side and the Cantor's first fractal of described second side face, symmetry, fractal parameters are identical;
所述微通道的纵向截面是指沿所述微通道长度方向对所述微通道水平切割形成的截面。The longitudinal section of the microchannel refers to the section formed by cutting the microchannel horizontally along the length direction of the microchannel.
康托尔分形原理最早由德国数学家康托提出。三分康托集是很容易构造的，然而它却显示出许多最典型的分形特征。它是从单位区间出发，再由这个区间不断地去掉部分子区间的过程。图1显示了康托尔分形原理的结构。初级分形为将一段长为L0的线段三等分，每段长度为L1，中间部分高度为h0。二级分形为将两边长度为L1的线段继续三等分，分形长度为L2，高度为h1。Cantor's fractal principle was first proposed by German mathematician Cantor. The three-part Cantor set is easy to construct, yet it shows many of the most typical fractal features. It starts from the unit interval, and then continuously removes some sub-intervals from this interval. Figure 1 shows the structure of Cantor's fractal principle. The primary fractal is to divide a segment of length L0 into three equal parts, each segment has a length of L1 and the height of the middle part is h0 . The second-level fractal is to divide the line segment with length L1 on both sides into thirds, the fractal length is L2 , and the height is h1 .
基于康托尔分形的填充床微反应器，其微通道的相对的两侧面侧采用康托尔一次分形，即可在微通道形成四组分形挡板。相邻两分形挡板之间距离，即分形宽度R，等于康托尔分形原理中每段长度。分形挡板的高度，即分形高度，等于康托尔分形原理中中间部分的高度。For the packed bed microreactor based on the Cantor fractal, the opposite sides of the microchannel adopt the Cantor fractal once to form four-component baffles in the microchannel. The distance between two adjacent fractal baffles, that is, the fractal width R, is equal to the length of each section in Cantor's fractal principle. The height of the fractal baffle, that is, the fractal height, is equal to the height of the middle part in Cantor's fractal principle.
对矩形微通道的两侧面进行基于康托尔初次分形，如图4所示，一共分为相向、同向和相对三种不同的排列方式。在确定分形排列方式的基础上，对比不同分形尺寸对反应结果的影响，采取控制变量法确定分形高度与分形宽度。The two sides of the rectangular microchannel are based on Cantor's primary fractal, as shown in Figure 4, which can be divided into three different arrangements: opposite, same direction and opposite. On the basis of determining the arrangement of fractals, the influence of different fractal sizes on the reaction results was compared, and the control variable method was adopted to determine the fractal height and fractal width.
本发明通过实验研究发现：分形的排列方式、分形参数的改变，会导致微反应器的微通道结构变化，进而会影响反应结果。The present invention finds through experimental research that changes in the arrangement of fractals and fractal parameters will lead to changes in the microchannel structure of the microreactor, which in turn will affect the reaction result.
实验研究发现：相对于采用相对、相同分形排列方式获得的微通道，相向分形排列方式获得微通道对反应结果影响最好。所以，本发明采用相向分形排列方式获得的微通道；即，微通道纵向截面在其长度方向的第一边和第二边均采用康托尔一次分形；所述第一边的康托尔一次分形与所述第二边的康托尔一次分形相向、对称、分形参数相同。The experimental research found that compared with the microchannels obtained by using the opposite and the same fractal arrangement, the microchannels obtained by the opposite fractal arrangement have the best effect on the reaction results. Therefore, the present invention adopts the microchannel obtained by facing the fractal arrangement mode; that is, the first side and the second side of the longitudinal section of the microchannel in its length direction all adopt Cantor's primary fractal; the Cantor's primary fractal of the first side is opposite to the Cantor's primary fractal of the second side, and the symmetry and fractal parameters are the same.
实验研究发现：在采用在相向分形排列方式下，分形尺寸(分形参数)同样对反应结果有着显著影响。分形高度过大阻碍了反应物的流动，促进了逆向反应，分形高度过小导致反应不充分，分形宽度过大不利于反应的进行。当P＝1/2时，出口处H2O浓度最高且生成速度最快，反应结果最好。其中，P＝h/(1/2L)，R为分形宽度，L为微通道的宽度。R＝0.1时，H2O浓度明显高于R为其他尺寸时的浓度。Experimental research has found that: in the case of using the opposite fractal arrangement, the fractal size (fractal parameters) also has a significant impact on the reaction results. Too large fractal height hinders the flow of reactants and promotes the reverse reaction, too small fractal height leads to insufficient reaction, and too large fractal width is not conducive to the progress of the reaction. When P=1/2, the concentration of H2 O at the outlet is the highest and the generation speed is the fastest, and the reaction result is the best. Wherein, P=h/(1/2L), R is the fractal width, and L is the width of the microchannel. When R=0.1, the concentration of H2 O is obviously higher than that when R is other sizes.
因此，基于康托尔分形的微反应器，其微通道的P＝h/(1/2L)的取值范围为大于等于1/4小于等于3/4；其中，微通道的宽度为L，第一边和第二边均采用康托尔一次分形的分形高度为h。优选的，P＝h/(1/2L)的取值为1/2。Therefore, based on the microreactor of Cantor's fractal, the value range of P=h/(1/2L) of its microchannel is greater than or equal to 1/4 and less than or equal to 3/4; Wherein, the width of microchannel is L, and the fractal height that all adopts Cantor's primary fractal in the first side and the second side is h. Preferably, the value of P=h/(1/2L) is 1/2.
基于康托尔分形的微反应器，其微通道的纵截面的第一边和第二边的分形宽度为R，R大于等于0.1小于等于0.2。优选的，R等于0.1。For the microreactor based on Cantor's fractal, the fractal width of the first side and the second side of the longitudinal section of the microchannel is R, and R is greater than or equal to 0.1 and less than or equal to 0.2. Preferably, R is equal to 0.1.
基于康托尔分形的微反应器，可以用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应。当基于康托尔分形的微反应器用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应时，基于康托尔分形的微反应器内部填充有颗粒。所述颗粒为丙烯与氧气作为反应物生成二氧化碳和水的催化反应的催化剂。The microreactor based on Cantor's fractal can be used for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water. When the Cantor fractal-based microreactor is used for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water, the interior of the Cantor fractal-based microreactor is filled with particles. The particles are catalysts for the catalytic reaction of propylene with oxygen as reactants to form carbon dioxide and water.
本申请还进一步研究了基于康托尔分形的微反应器用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应时，反应条件对反应结果的影响。研究结果表明：研究结果表明：微反应器的微通道内部填充的颗粒的孔隙率在0.2-0.8范围内，孔隙率越小对反应结果越有利；故，优选孔隙率为0.8。C3H6与O2浓度比(反应物浓度比)在1-4:1范围内，3-4的反应物浓度比能达到较好的反应效果；优选的，反应物浓度比为3:1。The present application further studies the effect of reaction conditions on reaction results when the Cantor fractal-based microreactor is used in the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water. The research results show that: the research results show that the porosity of the particles filled in the microchannel of the microreactor is in the range of 0.2-0.8, and the smaller the porosity is, the more favorable the reaction result is; therefore, the preferred porosity is 0.8. The concentration ratio of C3 H6 to O2 (reactant concentration ratio) is in the range of 1-4:1, and a reactant concentration ratio of 3-4 can achieve a better reaction effect; preferably, the reactant concentration ratio is 3:1.
本发明的有益效果是：The beneficial effects of the present invention are:
首次提出基于康托尔分形对微反应器的微通道进行分形。微通道的相对的两侧面采用康托尔一次分形，使得微通道具有对称的、具有特定分布规律的内凹结构。内凹结构在微通道内形成特定分布的分形挡板，从而改变微通道的内部结构，进而改变反应物、生成物在微通道内的流动方向、流动速率，最终实现改变反应速率、产物的产率和转化率。相对于现有的直通形式的微通道，本发明提供的这种具有特定分布规律的内凹结构的微通道能显著提高产物的浓度。尤其是适用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应时，对微通道进行分形处理后反应物流经分形挡板时会产生强烈的混沌对流，从而增加反应物之间的接触面积，通过这种方式可以促进反应物的混合，从而提高反应物的转化率。For the first time, the fractal of the microchannel of the microreactor is proposed based on the Cantor fractal. The opposite sides of the microchannel adopt Cantor primary fractal, so that the microchannel has a symmetrical concave structure with specific distribution rules. The concave structure forms a specific distribution of fractal baffles in the microchannel, thereby changing the internal structure of the microchannel, and then changing the flow direction and flow rate of reactants and products in the microchannel, and finally realizing the change of reaction rate, product yield and conversion rate. Compared with the existing straight-through microchannels, the concave structure microchannels provided by the present invention can significantly increase the product concentration. It is especially suitable for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water. After the fractal treatment of the microchannel, the reactants will generate strong chaotic convection when they pass through the fractal baffle, thereby increasing the contact area between the reactants. In this way, the mixing of the reactants can be promoted, thereby improving the conversion rate of the reactants.
附图说明Description of drawings
图1是康托尔分形原理图；Fig. 1 is the schematic diagram of Cantor fractal;
图2是本发明实施提供的一种基于康托尔分形的填充床微反应器的结构示意图；Fig. 2 is the structural representation of a kind of packed-bed microreactor based on Cantor fractal provided by the implementation of the present invention;
图3是网格独立性验证图；Figure 3 is a grid independence verification diagram;
图4是基于不同排列方式的康托尔分形的填充床微反应器的结构示意图；Fig. 4 is the structural representation of the packed bed microreactor based on the Cantor fractal of different arrangements;
图5是不同微通道的H2O浓度分布(a)、不同通道微反应器入口至出口中心截止线上H2O和C3H6的浓度(b)、不同通道下分形位置C3H6截面浓度图(c)、不同通道下分形位置H2O截面浓度图(d)；Fig. 5 is the concentration distribution ofH2O in different microchannels (a), the concentration ofH2O andC3H6 on the cut-off line from the entrance to the outlet of microreactors in differentchannels (b ), the cross-sectional concentration diagram ofC3H6 at fractal positions under different channels (c), and the cross-sectional concentration diagram ofH2O at fractal positions under different channels (d);
图6是不同P下出口处H2O浓度随时间变化曲线(a)、不同R下出口处H2O浓度随时间变化曲线(b)、浓度分布图(c)、截面浓度图(d)；Figure 6 is the time-varying curve ofH2O concentration at the outlet under different P (a), the time-varying curve ofH2O concentration at the outlet under different R (b), the concentration distribution diagram (c), and the cross-sectional concentration diagram (d);
图7宏观微观结构中的微观催化剂多孔颗粒；Microscopic catalyst porous particles in the macroscopic microstructure of Fig. 7;
图8不同填充颗粒半径对应的反应物转化率和生成物产率；The reactant conversion rate and product yield corresponding to different filling particle radii of Fig. 8;
图9不同填充颗粒孔隙率对应的反应物转化率和生成物产率；Figure 9 Reactant conversion and product yield corresponding to different filling particle porosity;
图10不同反应物浓度比对应的反应物转化率和生成物产率；The corresponding reactant conversion rate and product yield of Fig. 10 different reactant concentration ratios;
图11不同C3H6与O2浓度比下微反应器中H2O浓度的变化。Fig. 11 Changes of H2 O concentration in the microreactor under different concentration ratios of C3 H6 and O2 .
具体实施方式Detailed ways
下面结合附图和实施例对本发明进一步说明。The present invention will be further described below in conjunction with the accompanying drawings and embodiments.
本说明书附图所绘示的结构、比例、大小等，均仅用以配合说明书所揭示的内容，以供熟悉此技术的人士了解与阅读，并非用以限定本发明可实施的限定条件，故不具技术上的实质意义，任何结构的修饰、比例关系的改变或大小的调整，在不影响本发明所能产生的功效及所能达成的目的下，均应仍落在本发明所揭示的技术内容涵盖的范围内。同时，本说明书中所引用的如“上”、“下”、“左”、“右”、“中间”及“一”等的用语，亦仅为便于叙述的明了，而非用以限定本发明可实施的范围，其相对关系的改变或调整，在无实质变更技术内容下，当亦视为本发明可实施的范畴。The structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification, for those who are familiar with the technology to understand and read, and are not used to limit the conditions for the implementation of the present invention, so they have no technical substantive meaning. Any modification of the structure, change of the proportional relationship or adjustment of the size should still fall within the scope covered by the technical content disclosed in the present invention without affecting the functions and goals that the present invention can produce. At the same time, terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and clarity, and are not used to limit the scope of the present invention. The change or adjustment of their relative relationship should also be regarded as the scope of the present invention without substantive changes in the technical content.
一种基于康托尔分形的微反应器，包括微型微通道；微通道呈长方体形，其长度方向的两端开口，其纵向截面在其长度方向具有第一边和第二边；第一边和第二边均采用康托尔一次分形；第一边的康托尔一次分形与所述第二边的康托尔一次分形相向、对称、分形参数相同；微通道的纵向截面是指沿所述微通道长度方向对微通道水平切割形成的截面。A kind of microreactor based on Cantor fractal, comprising miniature microchannel; Microchannel is rectangular parallelepiped, and its two ends of length direction are open, and its longitudinal section has first side and second side in its length direction; First side and second side all adopt Cantor primary fractal; Cantor primary fractal of first side and described second side Cantor primary fractal opposite, symmetry, fractal parameter are identical; The longitudinal section of microchannel refers to the cross section that microchannel is cut horizontally along the length direction of described microchannel.
使微通道的长度方向沿水平方向地放置微反应器，微通道的开口(进口、出口)分别位于微通道的左右两端。微通道的前、后两侧面均采用康托尔一次分形，即，微通道水平截面的前后两边缘采用康托尔一次分形；微通道的前、后侧面的分形相向排列、对称分布(以微通道长度方向的中心线为对称轴)，且微通道的前、后侧面的分形参数形同；分形参数包括分形宽度、分形高度；分形宽度等于康托尔分形原理中每段长度，分形高度等于康托尔分形原理中中间部分的高度。The microreactor is placed so that the length direction of the microchannel is along the horizontal direction, and the openings (inlet and outlet) of the microchannel are respectively located at the left and right ends of the microchannel. The front and rear sides of the microchannel all adopt Cantor’s primary fractal, that is, the front and rear two edges of the horizontal section of the microchannel adopt Cantor’s primary fractal; the fractals of the front and rear sides of the microchannel are arranged in opposite directions and distributed symmetrically (with the centerline of the length direction of the microchannel as the axis of symmetry), and the fractal parameters of the front and rear sides of the microchannel are the same; fractal parameters include fractal width and fractal height; height.
基于康托尔分形的填充床微反应器，如图2所示，其微通道的相对的两侧面侧采用康托尔一次分形，即可在微通道形成四组分形挡板。相邻两分形挡板之间距离，即分形宽度R。分形挡板的高度，即分形高度。The packed bed microreactor based on Cantor fractal, as shown in Figure 2, can form four-component baffles in the microchannel by using Cantor fractal on the opposite sides of the microchannel. The distance between two adjacent fractal baffles is the fractal width R. The height of the fractal baffle, that is, the fractal height.
对长方体形微通道的两侧面进行基于康托尔初次分形(一次分形)，如图4所示，一共分为相向、同向和相对三种不同的分形排列方式。三种微通道出入口面积、微通道长度、一次分形的高度与宽度等参数均保持一致。其中，采用相向分形排列方式形成的基于康托尔分形的填充床微反应器结构如图2所示，主通道总长度为4mm，入口长度为0.4mm，高度为0.2mm。在主通道有4组分形挡板，相邻两挡板之间距离为0.9mm。The two sides of the cuboid microchannel are based on Cantor's primary fractal (primary fractal), as shown in Figure 4, which can be divided into three different fractal arrangements: opposite, same direction and relative. The parameters such as the area of the entrance and exit of the three microchannels, the length of the microchannel, and the height and width of the primary fractal are all consistent. Among them, the structure of the packed bed microreactor based on Cantor fractal formed by opposing fractal arrangement is shown in Figure 2. The total length of the main channel is 4mm, the entrance length is 0.4mm, and the height is 0.2mm. There are 4 sets of shaped baffles in the main channel, and the distance between two adjacent baffles is 0.9mm.
采基于康托尔分形的填充床微反应器进行丙烯与氧气作为反应物生成二氧化碳和水的催化反应。通过基于康托尔分形的填充床微反应器出口C3H6、O2、CO2和H2O的浓度判断分形排列方式、分形参数对反应结果的影响。A packed bed microreactor based on Cantor fractal is used for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water. Based on the concentration of C3 H6 , O2 , CO2 and H2 O at the outlet of the packed bed microreactor based on Cantor fractal, the influence of fractal arrangement and fractal parameters on the reaction results was judged.
丙烯与氧气作为反应物生成二氧化碳和水的催化反应如下所示：The catalytic reaction of propylene with oxygen as reactants to form carbon dioxide and water is shown below:
2C3H6+9O2→6H2O+6CO2 (1)2C3 H6 +9O2 →6H2 O+6CO2 (1)
采用COMSOL Multiphysics 5.5软件进行数值模拟分析。该软件可以计算用于物理模拟的偏微分方程。选择好的网格数可以保证计算结果的准确性。反应物在微通道中输运的模拟由稀物质传递模块实现。The numerical simulation analysis was carried out by COMSOL Multiphysics 5.5 software. The software can calculate partial differential equations for physical simulations. Choosing a good number of grids can ensure the accuracy of the calculation results. The simulation of reactant transport in microchannels is implemented by the Diluted Species Transport module.
填充床微反应器内部有大量反应颗粒，颗粒的反应由稀物质传递替代。针对选用的催化反应，建立了球形扩散/反应方程如下所示。我们可以看出球形微丸的扩散由颗粒半径，每单位床体积的颗粒数和有效扩散系数等因素影响。There are a large number of reactive particles inside the packed bed microreactor, and the reaction of the particles is replaced by dilute mass transfer. For the selected catalytic reactions, a spherical diffusion/reaction equation was established as shown below. We can see that the diffusion of spherical pellets is affected by factors such as particle radius, number of particles per unit bed volume and effective diffusion coefficient.
式中：r是从0(中心)到1(颗粒表面)的无量纲径向坐标，rpe是颗粒半径，N是每单位床体积的颗粒数量。在无量纲的几何中，粒子半径可以在不改变的情况下改变几何极限。Dpe是有效扩散系数(单位:m2/s)，rpe，i是反应源项[单位:mol/(m3·s)]。where r is the dimensionless radial coordinate from 0 (center) to 1 (particle surface),rpe is the particle radius, and N is the number of particles per unit bed volume. In dimensionless geometry, the particle radius can change the geometric limit without changing it. Dpe is the effective diffusion coefficient (unit: m2 /s), rpe, i is the reaction source item [unit: mol/(m3 ·s)].
考虑到颗粒与流体之间薄膜的作用。反应颗粒的输运可能受流体界面传递阻力的影响。流体穿过薄膜进入颗粒界面的流量用如下方程表示。Consider the effect of the thin film between the particle and the fluid. The transport of reactive particles may be affected by the transfer resistance at the fluid interface. The flow of fluid through the film into the particle interface is expressed by the following equation.
Ni,inward＝hd,i(ci-cpc,i) (3)Ni,inward ＝hd,i (ci -cpc,i ) (3)
式中：Ni,inward是从自由流体进入颗粒的摩尔流量，单位为mol/(m2·s)。In the formula: Ni,inward is the molar flow rate from the free fluid into the particle, and the unit is mol/(m2 ·s).
对甲烷在微反应器中的催化反应进行模拟，通过比较反应物的转化率和产率分析不同的结果。其表示如下所示：The catalytic reaction of methane in a microreactor was simulated, and the different results were analyzed by comparing the conversion and yield of reactants. Its representation looks like this:
式中：和/>分别是C3H6转化率和O2消耗率。/>和/>是CO2和H2O的产率。和/>分别是入口处C3H6和O2的浓度。/>和/>分别是出口C3H6、O2、CO2和H2O的浓度。In the formula: and /> are C3 H6 conversion and O2 consumption, respectively. /> and /> are the yields ofCO2 andH2O . and /> are the concentrations ofC3H6 andO2 at the inlet, respectively. /> and /> are the concentrations of C3 H6 , O2 , CO2 and H2 O at the outlet, respectively.
对不同分形排列方式形成的微通道结构内部的反应进行仿真分析后，图5(a)展示了4种不同微通道中生成物H2O浓度分布。从颜色变化来看，可以清晰地看出第一种微通道在出口处的H2O浓度更高。为了进一步探索H2O浓度在微通道中的变化，在入口与出口之间取一条三维截线，H2O与C3H6浓度随三维截线长度变化曲线如图5(b)所示，在各种微通道中反应物浓度呈现不规则变化趋势是由于分形挡板的阻碍造成逆反应的进行。在入口处H2O浓度迅速上升，随后缓慢增加。直微通道出口处H2O浓度最少，第二种微通道对反应结果的影响优于第三种微通道，向微通道内侧分形的矩形缺口微通道中生成的H2O浓度最高。因此第一种分形排列方式(两侧面的分形相向、对称)形成的微通道对反应结果的影响最好。从图5(c)-(d)中可以发现，直通道下微通道中流体浓度分布比较均匀，而对微通道进行分形处理后，微通道中流体浓度出现波动，这是因为反应物在分形挡板作用下发生紊乱，产生涡流，浓度梯度越大，反应物的混合越充分，从而提高微反应器的反应性能。After the simulation analysis of the reaction inside the microchannel structure formed by different fractal arrangements, Figure 5(a) shows the concentration distribution of product H2 O in four different microchannels. From the color change, it can be clearly seen that the H2 O concentration at the outlet of the first microchannel is higher. In order to further explore the change of H2 O concentration in the microchannel, a three-dimensional intercept line was taken between the inlet and the outlet. The curves of H2 O and C3 H6 concentrations changing with the length of the three-dimensional intercept line are shown in Fig. 5(b). The irregular change trend of the reactant concentration in various microchannels is due to the obstruction of the fractal baffle that causes the reverse reaction to proceed. The H2 O concentration rises rapidly at the inlet, followed by a slow increase. The H2 O concentration at the outlet of the straight microchannel was the least, the influence of the second microchannel on the reaction result was better than that of the third microchannel, and the concentration of H2 O generated in the rectangular notched microchannel fractal to the inner side of the microchannel was the highest. Therefore, the microchannels formed by the first fractal arrangement (the fractals on both sides face each other and are symmetrical) have the best influence on the reaction results. From Figure 5(c)-(d), it can be found that the distribution of fluid concentration in the microchannel under the straight channel is relatively uniform, but after the fractal treatment of the microchannel, the fluid concentration in the microchannel fluctuates. This is because the reactants are turbulent under the action of the fractal baffle, generating eddy currents. The larger the concentration gradient, the more fully the reactants are mixed, thereby improving the reaction performance of the microreactor.
相向分形排列方式下，基于康托尔分形的填充床微反应器结构如图2所示。然后对，接下来针对第一种微通道，对比不同分形尺寸对反应结果的影响。如图4(a)所示，令P＝h/(1/2L)。R为分形宽度。通过改变P与R的值对微反应器的结构优化，从而达到更佳的反应效果。Under the arrangement of opposite fractals, the structure of the packed bed microreactor based on Cantor fractal is shown in Fig. 2 . Then, for the first microchannel, compare the effects of different fractal sizes on the reaction results. As shown in Fig. 4(a), let P=h/(1/2L). R is the fractal width. By changing the value of P and R, the structure of the microreactor is optimized, so as to achieve a better reaction effect.
P取3个不同值(P＝3/4,P＝1/2,P＝1/4),不同P下出口处H2O浓度随时间变化曲线如图6(a)所示。可以看出入口处生成物浓度迅速上升，随后趋于稳定。P＝1/2时，出口处H2O浓度最高且生成速度最快，P＝3/4时，生成的H2O浓度最低。因此分形高度过大阻碍了反应物的流动，促进了逆向反应，分形高度过小导致反应不充分。P takes three different values (P=3/4, P=1/2, P=1/4), and the H2 O concentration at the outlet varies with time under different P values, as shown in Figure 6(a). It can be seen that the product concentration at the inlet rises rapidly and then tends to be stable. When P=1/2, the concentration of H2 O at the outlet is the highest and the generation speed is the fastest, and when P=3/4, the concentration of H2 O generated is the lowest. Therefore, too large fractal height hinders the flow of reactants and promotes the reverse reaction, while too small fractal height leads to insufficient reaction.
图6(b)展示了4种不同R值(R＝0.1，R＝0.14，R＝0.18，R＝0.2)下出口处H2O浓度随时间变化曲线。R＝0.1时，H2O浓度明显高于另外三种情况。R＝0.2时，产物浓度最低。因此分形宽度过大不利于反应的进行。为了进一步探索微反应器中的反应，在通道通道不同部位取4个截面，截面浓度图如图6(c)-(d)所示，可以看出截面两边浓度比中间浓度高，因为分形使反应物产生横向分流，这使得两侧的反应更充分，因此两边浓度高于中间浓度。Fig. 6(b) shows the curves of H2 O concentration at the outlet with time for four different R values (R=0.1, R=0.14, R=0.18, R=0.2). When R=0.1, the concentration of H2 O is obviously higher than that of the other three cases. When R=0.2, the product concentration is the lowest. Therefore, too large fractal width is not conducive to the reaction. In order to further explore the reaction in the microreactor, four cross-sections were taken at different parts of the channel. The concentration diagrams of the cross-sections are shown in Figure 6(c)-(d). It can be seen that the concentration on both sides of the cross-section is higher than the middle concentration, because the fractal causes the reactant to generate a lateral shunt, which makes the reaction on both sides more complete, so the concentration on both sides is higher than the middle concentration.
基于康托尔分形的微反应器，可以用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应。当基于康托尔分形的微反应器用于丙烯与氧气作为反应物生成二氧化碳和水的催化反应时，基于康托尔分形的微反应器的微通道内部填充有颗粒。所述颗粒为丙烯与氧气作为反应物生成二氧化碳和水的催化反应的催化剂；工业上以金属氧化物(如Cu2O)为催化剂，用空气氧化丙烯。The microreactor based on Cantor's fractal can be used for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water. When the Cantor fractal-based microreactor is used for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water, the microchannel of the Cantor fractal-based microreactor is filled with particles. The particles are catalysts for the catalytic reaction of propylene and oxygen as reactants to generate carbon dioxide and water; industrially, metal oxides (such as Cu2 O) are used as catalysts to oxidize propylene with air.
除了结构对反应结果的影响外，还需考虑颗粒半径、颗粒孔隙率的影响。图7显示了反应颗粒在通道中的排列方式及单个颗粒的内部浓度图。可以看出颗粒表面和颗粒中心的浓度是不同的。In addition to the influence of structure on the reaction results, the influence of particle radius and particle porosity also needs to be considered. Figure 7 shows the arrangement of reacting particles in the channel and the internal concentration map of individual particles. It can be seen that the concentration at the surface of the particle is different from that at the center of the particle.
图8显示了4种不同大小的颗粒半径对反应结果的影响。颗粒半径分别为600纳米、900纳米、1500纳米、2000纳米。从表中数据可以看出：4组数据中C3H6和O2的转化率大致相同。因此可以得出结论：反应结果不受反应颗粒半径影响。Figure 8 shows the effect of 4 different sizes of particle radii on the reaction results. The particle radii are 600 nm, 900 nm, 1500 nm, and 2000 nm, respectively. It can be seen from the data in the table that the conversion rates of C3 H6 and O2 in the four sets of data are roughly the same. Therefore, it can be concluded that the reaction result is not affected by the radius of the reaction particle.
不同颗粒孔隙率对反应结果的影响如图9所示，颗粒孔隙率分别为0.2、0.6、0.8。从表中可以看出随着孔隙率的增加，C3H6与O2的转化率降低，生成物的产率也降低。因此在此填充床微反应器中，颗粒孔隙率越小，对反应结果越有利。The influence of different particle porosities on the reaction results is shown in Figure 9, and the particle porosities are 0.2, 0.6, and 0.8, respectively. It can be seen from the table that as the porosity increases, the conversion rate of C3 H6 and O2 decreases, and the yield of products also decreases. Therefore, in this packed bed microreactor, the smaller the particle porosity, the more favorable the reaction result.
图10显示了不同的反应物浓度比对反应结果的影响。C3H6与O2浓度比分别为1:1、2:1、3:1、4:1。从表中数据可以看出反应物浓度比增加，C3H6转化率降低，O2转化率增加，CO2和H2O的产率也随之增加。但这样并不意味着反应物浓度比越大，对反应结果的影响越好。在一定范围内，特定的反应物浓度比才能达到最好的反应效果。Figure 10 shows the effect of different reactant concentration ratios on the reaction results. The concentration ratios of C3 H6 and O2 are 1:1, 2:1, 3:1, and 4:1, respectively. It can be seen from the data in the table that the concentration ratio of the reactants increases, the conversion rate of C3 H6 decreases, the conversion rate of O2 increases, and the yields of CO2 and H2 O increase accordingly. But this does not mean that the greater the reactant concentration ratio, the better the effect on the reaction result. Within a certain range, the specific reactant concentration ratio can achieve the best reaction effect.
为了探索微反应器中反应物与生成物浓度具体的变化。在入口与出口之间取一三维截线，图11显示了不同C3H6与O2浓度比下微反应器中H2O浓度随微反应器长度的变化。在入口处，H2O浓度迅速增加。当C3H6与O2浓度比为4:1时，反应速率最快。随着通道长度的增加，其浓度呈缓慢变化趋势。在出口处，反应物浓度比小的两组生成H2O浓度差距较大。反之，当和当/>时，出口处H2O浓度较接近。因此反应物浓度比过大时对反应结果的影响不大反而会造成反应物的浪费。In order to explore the specific changes in the concentration of reactants and products in the microreactor. Taking a three-dimensional cross-section between the inlet and the outlet, Fig. 11 shows the variation of the H2 O concentration in the microreactor with the length of the microreactor under different concentration ratios of C3 H6 and O2 . At the inlet, theH2O concentration increases rapidly. When the concentration ratio of C3 H6 to O2 is 4:1, the reaction rate is the fastest. With the increase of the channel length, its concentration showed a slow trend. At the outlet, the difference in H2 O concentration between the two groups with smaller reactant concentration ratio is larger. Conversely, when and when /> When , the concentration of H2 O at the outlet is relatively close. Therefore, when the reactant concentration ratio is too large, it has little effect on the reaction result but will cause waste of reactant.
上述虽然结合附图对本发明的具体实施方式进行了描述，但并非对本发明保护范围的限制，所属领域技术人员应该明白，在本发明的技术方案的基础上，本领域技术人员不需要付出创造性劳动即可作出的各种修改或变形仍在本发明的保护范围以内。Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or deformations that those skilled in the art can make without creative labor are still within the protection scope of the present invention.
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