相比于传统的釜式设备或管式设备，由于堆叠式微通道反应器微小流道内的流体受壁面的影响较大，而受重力的影响相对较小，所以其中重组分和轻组分之间或气液之间混合程度更好。图1是常规反应器与堆叠式微通道反应器的传热传质效率对比，堆叠式微通道反应器主要通过通道微型化来实现常规反应釜无法达到的传热传质效率。

Figure 1 shows the comparison of heat and mass transfer efficiency between conventional reactors and stacked microchannel reactors. Stacked microchannel reactors mainly achieve heat and mass transfer efficiency that conventional reactors cannot achieve through channel miniaturization.

Compared to traditional kettle or tube equipment, the fluid in the microchannel of a stacked microchannel reactor is more affected by the wall surface and less affected by gravity, resulting in better mixing between heavy and light components or between gas and liquid.

图1 常规反应器与堆叠式微通道反应器的传热传质效率对比

Fig. 1 Comparison between conventional reactor and microchannel reactor

图2中根据流体的物理性质和流速的不同，将流动形式分为三种，例如，在水和油这两种互不溶解的液体中，在流速较低的区域出现段塞流，在流速较高的区域出现两层流。

In Fig. 2, the flow forms are classified into three types depending on the physical properties of the fluid and the flow rate, e.g., in water and oil, which are mutually insoluble fluids, segmental plug flow occurs in the region of lower flow rate, and two-layer flow occurs in the region of higher flow rate.

图2 微通道中的流型示例

Fig. 2  Example of flow pattern in microchannel

图3是段塞流的图片及示意图。例如，流体的亲水性导致其在壁面（不锈钢或玻璃材质）处流动停止。此时，油相就被水相包围。所以，段塞流会在流体界面产生比层流更大的接触面积。此外，壁面处的流动停止也会引起油相/水相的内循环流动。所以选择性地利用段塞流优化传质效率。

Figure 3 shows a picture and a schematic diagram of a segment plug flow. For example, the hydrophilicity of the fluid causes its flow to stop at a wall (stainless steel or glass). The oil phase is surrounded by the water phase. Therefore, segment plugging produces a larger contact area at the fluid interface than laminar flow. In addition, the stoppage of flow at the wall causes an internal circulation of the oil/water phase. So selective use of segment plug flow optimises the mass transfer efficiency.

图3 微通道内的段塞流

Fig. 3  Slug flow in microchannel

堆叠板式微通道反应器

stacked plate microchannel reactor

图4 二维反应器和三维反应器的基本结构

Fig. 4  Basic construction of two-dimensional reactor and three-dimensional reactor

如图4上方所示，堆叠板式微通道反应器内的流道基本上由多个管组成，每个通道汇流的形式为Y形或T形。如果此工艺用于产能扩大时，由于液体的进料方式不同，该通道结构布置将会受限。尽管在堆叠方向上可以通过增加反应板的方式实现工艺放大，但在水平方向上难以有效地排列多个流体通道，所以该结构不适合大容量的堆叠板式微通道反应器。因此，如图4下方所示，将微通道反应板的两侧设计为三维布置的流道则很好的解决了这个问题。

The flow channel within a stacked plate microchannel reactor essentially consists of multiple tubes, each having a Y shape or a T shape, as shown in Fig. 4 top. If this process is used to increase production capacity, the arrangement of the channel structure will be limited due to different liquid feeding methods. Although process amplification can be achieved by adding reaction plates in the stacking direction, it is difficult to effectively arrange multiple fluid channels in the horizontal direction, so this structure is not suitable for high-capacity stacked plate microchannel reactors. Therefore, as shown in the lower part of Fig. 4, designing the two sides of the microchannel reaction plate as a three-dimensional arrangement of flow channels is a good solution to this problem..

图5 堆叠板式微通道反应器的基本结构

Fig. 5  Basic construction of stacked plate microchannel reactor

图6 堆叠板式微通道反应器的内部结构

Fig. 6 Internal structure of stacked plate microchannel reactor

如图5和图6所示，这种结构可以通过每个板的流道数量与堆叠板的数量相乘得到总流道数量。可以在堆叠板中间设置温控层，实现对反应温度的精确控制。此外，我们可以通过在入口处设置封头来讲进料物料均匀的分配至每个金属板中。

As shown in FIGS. 5 and 6, this structure allows the total number of runners to be obtained by multiplying the number of runners per plate with the number of stacked plates. A temperature control layer can be set in the middle of the stacked plates to achieve precise control of the reaction temperature. In addition, we can set up a header at the inlet to evenly distribute the feed material into each plate.

图7 化学蚀刻制造的微通道

Fig. 7 Microchannel manufactured by chemical etching

图8 通道和扩散键合界面的截面图

Fig. 8 Cross-sectional observation of channels anddiffusion bonded interface

堆叠板式微通道反应器的制作过程如下:首先，在金属板(如不锈钢板)上进行化学蚀刻，形成如图7所示的流道。接下来，根据设计的通道的数量将金属板与导热油层交替堆叠。然后在真空炉中加热和压制堆叠的板，通过扩散焊使其连接起来，形成流动通道。

图8所示为不锈钢扩散焊的截面。流动通道无变形，且能观测到晶粒在结合界面之外生长，可以保证焊接强度等于或高于母材的强度。

因此，可以仅基于流道尺寸的强度计算来估计耐压性能。可以使不同的耐腐蚀、耐温或耐压材料来制作，这使得设计和生产具有高度的自由度。

The stacking plate microchannel reactor is made as follows: First, a metal plate (such as a stainless steel plate) is chemically etched to form the flow channel shown in Figure 7. Next, the metal plate is alternately stacked with the thermal oil layer according to the number of designed channels. The stacked plates are then heated and pressed in a vacuum furnace and joined by diffusion welding to form a flow channel.

Figure 8 shows the cross section of stainless steel diffusion welding. There is no deformation in the flow channel, and the growth of grains can be observed outside the bonding interface, which can ensure that the welding strength is equal to or higher than the strength of the base material.

Therefore, the pressure resistance can be estimated based on strength calculations of the flow channel size alone. Different corrosion, temperature or pressure resistant materials can be made, which allows a high degree of freedom in design and production.

图9 萃取用微通道反应器

Fig. 9 Microchannel reactor for extraction

萃取作为化学品生产中的一个重要步骤。使用堆叠板式微通道反应器对物质进行萃取有如下四个方面的优势。第一，大幅度缩短提取时间。第二，减小萃取设备的尺寸。第三，萃取溶剂用量更小，降低萃取溶剂的损耗。第四，尤其适用于需要多级萃取的工艺流程。

Extraction is an important step in chemical production.The use of stacked plate microchannel reactor for material extraction has the following four advantages.First, the extraction time is greatly shortened. Second, reduce the size of the extraction equipment. Third, the amount of extraction solvent is smaller, reducing the loss of extraction solvent. Fourth, it is especially suitable for the process flow requiring multistage extraction.

进行混合萃取测试，将萃取进料和萃取溶剂各100ml倒入200ml烧杯中，使用磁力搅拌器搅拌。分析萃取进料中的苯酚浓度以确定萃取速率。结果如图10所示。

在该混合萃取测试中，增加转数能缩短萃取所需的时间；但是转速高于400rpm会使萃取进料在萃取溶剂中分散，分离困难。混合萃取需要大约100分钟才能达到平衡萃取，而微通道反应器中在0.1到1分钟内达到了相同的结果，缩短了大约1/100。一旦流体排出，就将它们分离成萃取进料和萃取溶剂的两相。这是因为混合部分不是剧烈混合，而是形成段塞流或油和水的双层流，可以轻易分离。

Conduct a mixed extraction test, pour 100ml of extraction feed and 100ml of extraction solvent into a 200ml beaker, and stir using a magnetic stirrer. Analyze the concentration of phenol in the extraction feed to determine the extraction rate. The result is shown in Figure 10.

In this mixed extraction test, increasing the number of rotations can shorten the extraction time required; However, a speed higher than 400rpm will cause the extraction feed to disperse in the extraction solvent, making separation difficult. Mixed extraction takes about 100 minutes to reach equilibrium extraction, while microchannel reactor achieved the same result within 0.1 to 1 minute, shortening by approximately 1/100. Once the fluid is discharged, they are separated into two phases of extraction feed and extraction solvent. This is because the mixing part is not violently mixed, but forms a slug flow or a double-layer flow of oil and water, which can be easily separated.

图10 萃取用测试结果（微通道反应器与混合器）

Fig.10 Test results for extraction use (Microchannel Reactor vs. Mixer)

        在传统的萃取装置中，混合罐也用作分离罐，如图11所示。在这样的罐中，分批进行多个萃取步骤，每个步骤之后是分离步骤。在一些提取应用中，萃取操作本身仅持续几分钟；然而，分离需要几个小时，需要大量的时间和劳动力才能达到目标萃取率。另一方面，当微通道反应器用于多级萃取时，可以堆叠和集成多个萃取单元，如图12所示。此外，萃取后具有优异的可分离性，可实现连续工艺：原料通过沉降器快速分离，连续送入微通道反应器。这消除了传统类型工艺所需的耗时的分离和溶液充电和放电的切换操作，从而使微通道反应器能够进行有效的萃取。

        In a conventional extraction unit, the mixing tank serves also as a separation tank as shown in Fig.11. In such a tank, multiple steps of extraction, each followed by a separation step, were performed in batches. In some extraction applications, the extraction operation itself lasts for only several minutes; however, the separation takes several hours, requiring much time and labor to achieve the target extraction rate. On the other hand, when the Microchannel Reactor is used for multistage extraction, more than one extraction unit can be stacked and integrated as shown in Fig.12. Furthermore, the excellent separability after extraction enables a continuous process: the raw material, rapidly separated by settlers, is continuously fed into the Microchannel Reactor.

图11 使用萃取器的常规萃取装置

Fig11 Conventional extraction unit using mixer

图12 采用微通道反应器的多级萃取装置

Fig12 Multi-stage extraction unit using Microchannel Reactor

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