A microwave tube reaction device

Abstract

The present invention discloses a microwave tube reaction device, comprising a reactor shell and a plurality of horizontal metal partitions evenly spaced inside the reactor shell, wherein the metal partitions divide the internal space of the reactor shell into a plurality of identical reaction chambers, wherein a plurality of reaction tubes and metal tubes are arrayed in the reactor shell, wherein the metal tubes are arranged between the reaction tubes; waveguides are symmetrically arranged on two sides of each reaction chamber, wherein the waveguides are symmetrically distributed on both sides, wherein the waveguides on the same side are connected to a waveguide crack antenna, wherein a microwave generator is connected to the waveguide crack antenna via a circulator, wherein each crack in the waveguide crack antenna is connected to the corresponding reaction chamber via a waveguide. The present invention utilizes the waveguide crack antenna, the metal partition, the metal tube, etc. to achieve uniform temperature distribution inside the microwave tube reactor under large size, reduce the amplification effect, and facilitate the numerical amplification of the microwave tube reactor.

Description

Technical Field

[0001] The invention relates to the field of chemical production, and in particular to a microwave tube reaction device. Background Art

[0002] Tubular reactors have the characteristics of simple structure, convenient operation, low back mixing, and high volumetric efficiency, and are widely used in the chemical industry. Traditional tubular reactors mainly supply heat from the outside to the inside by conduction or convection, which often causes uneven temperature distribution in the reaction tube and a temperature gradient inside the bed of the reaction tube. The use of interlayer heat exchange can reduce the overall temperature change of the catalyst bed, but the radial temperature gradient cannot be reduced. The heat transfer effect is enhanced by reducing the tube diameter, but a small tube diameter will cause a significant wall effect. CN106008188B proposes a new type of microwave tubular reaction device, which utilizes the characteristics of microwave body heating and selective heating to improve the uniformity of the temperature distribution of the catalyst bed in the reaction tube, and effectively improve the product yield and catalyst stability.

[0003] In order to meet the industrial application of microwave tube reaction devices, it is necessary to study the amplification of microwave reactors. Zhang Wencong enlarged the volume of the single-mode reaction cavity by adding a conical waveguide after the standard waveguide. However, only a single reaction tube can be placed in the reaction cavity, and the actual amplification effect is limited (Zhang W, et al., Chemical Engineering Journal, 2022, 472: 131898). CN104667849B and CN210787284U use multiple reaction tubes in series or in parallel to achieve the amplification of the reaction device, but the current research mainly uses the method of improving the structure of the reaction tube or waveguide tube to improve the production capacity of the microwave reaction device. The reactor based on the single-mode cavity structure can improve the production capacity of the device to a certain extent, but it is difficult to use in a tube-in-tube structure due to the limitation of the electromagnetic field distribution mode. CN114904287A proposes a microwave heating tube-in-tube evaporator, which can uniformly heat SiC tubes, but the axial temperature distribution of a single reaction tube is uneven, and there is still a certain temperature gradient in the filler inside the reaction tube. Summary of the invention

[0004] In view of the above technical problems existing in the prior art, the object of the present invention is to provide a microwave tube reaction device.

[0005] The present invention aims to be accomplished through the following technical solutions:

[0006] A microwave tube type reaction device comprises a microwave generator, a circulator, a waveguide crack antenna, a waveguide, an infrared probe, a temperature controller and a reactor shell, wherein a metal tube sheet is respectively arranged at the upper and lower ends of the reactor shell, and a plurality of horizontal metal partitions are evenly arranged in the reactor shell between the two metal tube sheets, and the metal partitions divide the internal space of the reactor shell into a plurality of identical reaction chambers, and waveguides are symmetrically arranged at the middle positions of the side walls on the opposite sides of each reaction chamber, and the waveguides are symmetrically distributed on both sides, and the waveguides on the same side are connected to a waveguide crack antenna, and each crack in the waveguide crack antenna is communicated with the corresponding reaction chamber through the waveguide, and the waveguide crack antenna is connected to the microwave generator through the circulator;

[0007] A plurality of reaction tubes and metal tubes are arranged in an array in the reactor shell, the metal tubes are arranged between the reaction tubes, the reaction tubes and the metal tubes respectively pass through the metal partition plate vertically, and both ends of the reaction tubes and the metal tubes are fixedly arranged on two metal tube plates;

[0008] A temperature measuring port is provided on the side of the reactor shell, and the infrared probe measures the temperature inside the reaction chamber through the temperature measuring port. The infrared probe is then connected to the microwave generator signal through a temperature controller;

[0009] The reaction tube is made of wave-transmitting material.

[0010] Furthermore, the feed type of the reactor shell is gas and / or liquid. When the feed type includes gas, both ends of the reaction tube are set to be openings, a gas inlet is set at the lower end of the reactor shell, and a gas outlet is set at the top. The gas feed is directly sprayed into the cavity at the lower part of the reactor shell through the gas inlet and then enters the reaction tube, and then is collected in the cavity at the upper part of the reactor shell and discharged from the gas outlet; when the feed type includes liquid, a liquid inlet and a liquid outlet are respectively set at the top and bottom of the reactor shell, and the liquid introduced through the liquid inlet can enter the reaction tube and finally be discharged from the liquid outlet.

[0011] Furthermore, the feed type includes liquid, and both ends of the reaction tube are set to be openings. A liquid distributor is arranged inside the upper end of the reactor shell, and the liquid inlet end of the liquid distributor is connected to the liquid inlet. A plurality of drainage pipes are arranged at the bottom of the liquid distributor. The arrangement of the drainage pipes corresponds to the position of the reaction tube. The drainage pipes are arranged directly above the opening at the upper end of the reaction tube, so that the liquid dripping through the liquid distributor can evenly enter each reaction tube.

[0012] Furthermore, a heat exchange tube can be built into the center of the interior of the reaction tube, and an annular gap space for materials to pass through is formed between the heat exchange tube and the inner wall of the reaction tube. The lower end of the heat exchange tube passes through the lower end opening of the reaction tube and is connected to the heat exchange fluid inlet main pipe. The heat exchange tube passes through the upper end opening of the reaction tube and is connected to the heat exchange fluid outlet main pipe. One end of the heat exchange fluid inlet main pipe and one end of the heat exchange fluid outlet main pipe respectively pass through the side walls of the reactor shell, and the reaction temperature in the reaction tube is controlled by introducing heat exchange fluid into the heat exchange tube.

[0013] Furthermore, the feed type includes liquid, and both ends of the reaction tube are set to be openings, and the openings of multiple reaction tubes are connected in series with each other through pipes. The upper end opening of the first reaction tube is connected to the liquid inlet through a pipe, and the lower end opening of the last reaction tube is connected to the liquid outlet through a pipe, so that the liquid introduced through the liquid inlet can flow from the first reaction tube to the last reaction tube, and finally be discharged from the liquid outlet.

[0014] Furthermore, a metal pin is nailed into the side of the waveguide, and by adjusting the side position and nailing depth of the metal pin on the waveguide, a plurality of evenly distributed strong microwave fields are formed in the corresponding reaction chamber, and a weak microwave field exists between the strong microwave fields, and the strong microwave field and the weak microwave field appear in sequence in the direction where the length of the waveguide extends, and the direction in which the waveguide transmits microwaves is recorded as the direction in which its length extends; wherein the material of the metal pin is stainless steel that can reflect microwaves, and the metal pin is horizontally arranged and perpendicular to the length extension direction of the waveguide.

[0015] Furthermore, the waveguide is a rectangular cavity structure, and the metal pin is arranged at the vertical middle position of the vertical side of the waveguide. By adjusting the horizontal distance of the metal pin compared to the crack of the waveguide crack antenna and its nailing depth, multiple evenly distributed strong microwave fields are formed in the corresponding reaction cavity.

[0016] The electric field distribution in the reaction chamber can be adjusted to be more uniform by setting metal pins. This is because: when the input impedance and output impedance of the microwave system do not match, it will cause reflection and energy loss. The metal pins can adjust the impedance matching by changing the impedance of the system. After inserting the metal pins, the equivalent impedance of the system can be adjusted to be closer to the required matching value, thereby reducing reflection and improving the transmission efficiency of microwave energy. Therefore, by adjusting the insertion depth of the pins between different layers of waveguides, the equivalent impedance of the reaction chambers of different layers is adjusted to remain the same, so that the electric field of each layer is evenly distributed.

[0017] Furthermore, the materials of the reactor shell, metal tube plate, metal partition, metal tube, waveguide slot antenna and waveguide are stainless steel materials that can reflect microwaves.

[0018] Furthermore, the reaction tubes and the metal tubes are arranged in parallel in rows, the straight line where each row of reaction tubes or metal tubes is located is perpendicular to the length direction of the waveguide, and the direction in which the waveguide transmits microwaves is recorded as the direction in which its length extends; the reaction tubes and the metal tubes are arranged in rows in the reactor shell corresponding to the regional position where the strong microwave field is located and the regional position where the weak microwave field is located; the present invention utilizes the property of metal to reflect electromagnetic waves, and by reasonably setting parameters such as the position of the metal tube in the reaction cavity, it can destroy the resonance condition of the interference mode in the reaction cavity, thereby reducing the influence of the interference mode on the electric field distribution in the cavity.

[0019] Furthermore, the reaction tubes are arranged in a tube-in-tube manner and are made of wave-transmitting and high-temperature resistant material such as quartz or polytetrafluoroethylene. Depending on the polarity of the feed material, the interior of the reaction tubes is filled with absorbing material or wave-transmitting material. The absorbing material is silicon carbide, activated carbon or a catalyst with wave-absorbing ability, and the wave-transmitting material is glass or ceramic.

[0020] Furthermore, the height of each reaction cavity is 0.4-0.9 times of a microwave wavelength, and the wavelength of microwaves at 915MHz is about 0.328 m. The higher reaction cavity height provides space for a variety of different electromagnetic field modes, and different modes have different field distribution characteristics. When the reaction cavity height exceeds one microwave wavelength, it is easier to excite multiple modes in the height direction, resulting in uneven electric field distribution.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The novel microwave tube reactor of the present invention uses a metal partition to evenly divide the reaction cavity into a plurality of identical reaction cavities, and uses a waveguide slot antenna with a metal pin to evenly feed microwave energy into each reaction cavity, thereby significantly improving the uniformity of the electromagnetic field distribution in the reaction device and the temperature distribution in the reaction tube. At the same time, the metal tube can reduce the influence of the interference mode, and the metal pin adjusts the electromagnetic field distribution in each reaction cavity by changing the cavity resonant frequency, thereby reducing the influence of the change of operating conditions on the electromagnetic field distribution and the temperature distribution, which is conducive to the industrial amplification of the microwave tube reactor.

[0023] 2. The novel microwave tube reaction device of the present invention sets the reaction tube at a position where the microwave field intensity is high and uniform, thereby improving energy utilization efficiency and achieving reaction process intensification.

[0024] 3. In the novel microwave tube reaction device of the present invention, the interior of the reaction tube can be completely filled with fillers or a heat exchange structure can be built into the fillers, so that the reaction device can be applicable to reaction systems with different thermal effects. In addition, the reaction tubes can be used independently in parallel or in series, so that the reaction device can be applicable to reaction systems with different residence times, thereby improving the versatility of the reaction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of a microwave tube reaction device of the present invention in which different reaction tubes are connected in parallel.

[0026] Figure 2 It is a schematic structural diagram of the microwave tube reaction device of the present invention in which different reaction tubes are connected in series through pipelines.

[0027] Figure 3 This is a schematic diagram of the structure of the heat exchange tube in the center of the reaction tube.

[0028] Figure 4 This is a simulation diagram of the electric field distribution according to the actual size of the single-layer reaction chamber in Example 1 of the present invention.

[0029] Figure 5 This is a comparison diagram of the electric field distribution along the axial direction of the tube under the electromagnetic field confinement of a 0.66m high reaction cavity with a single feed inlet excitation, a 0.66m high reaction cavity with multiple feed inlets excitation, and a three-layer 0.22m high reaction cavity in Example 1 of the present invention.

[0030] Figure 6 This is a graph showing the variation of the coefficient of variation of the electric field distribution in different reaction tubes with and without the addition of metal tubes as a function of the side length of the reactor.

[0031] Figure 7 This is a comparison diagram of the electric field distribution along the axial direction of the tube when no metal pins are added and when metal pins are added.

[0032] Figure numerals: reactor shell 1-1, liquid distributor 1-2, metal tube sheet 1-3, metal partition 1-4, reaction tube 1-5, metal tube 1-6, liquid inlet 1-7, liquid outlet 1-8, gas inlet 1-9, gas outlet 1-10, temperature measuring port 1-11, infrared probe 2, temperature controller 3, waveguide slit antenna 4, waveguide 5, metal pin 6, circulator 7, microwave generator 8. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below in conjunction with the accompanying drawings:

[0034] As attached Figure 1-3 As shown, a microwave tube reaction device includes a microwave generator 8, a circulator 7, a waveguide slit antenna 4, a waveguide 5, an infrared probe 2, a temperature controller 3 and a reactor shell 1-1. A temperature measuring port 1-11 is arranged on the side of the reactor shell 1-1, and the infrared probe 2 measures the temperature inside the reaction chamber through the temperature measuring port 1-11. The infrared probe 2 is then connected to the microwave generator 8 through the temperature controller 3.

[0035] A metal tube sheet 1-3 is provided at the upper and lower ends of the reactor shell 1-1, respectively. Multiple horizontal metal partitions 1-4 are evenly spaced in the reactor shell 1-1 between the two metal tube sheets 1-3, and the internal space of the reactor shell 1-1 is divided into a plurality of identical reaction chambers. Waveguides 5 are symmetrically provided at the middle positions of the two opposite side walls of each reaction chamber, and the waveguides 5 are symmetrically distributed on both sides. The waveguides 5 on the same side are connected to a waveguide crack antenna 4, and the waveguide crack antenna 4 has cracks for transmitting microwaves at relative positions to the waveguide 5. Each crack in the waveguide crack antenna 4 is connected to the corresponding reaction chamber through the waveguide 5, and the microwave generator 8 is connected to the waveguide crack antenna 4 through the circulator 7. The microwaves emitted by the microwave generator 8 are transported by the circulator 7 and divided into two paths, enter the two waveguide crack antennas 4, and then enter each reaction chamber through the waveguides 5 on both sides.

[0036] A plurality of reaction tubes 1-5 and metal tubes 1-6 are arranged in an array in the reactor shell 1-1. The reaction tubes 1-5 are arranged in a tube-in-tube manner and are made of quartz or polytetrafluoroethylene wave-transmitting, high-temperature-resistant and wave-transmitting materials. According to the polarity of the feed material, the reaction tubes are filled with absorbing materials or wave-transmitting materials. The absorbing materials are silicon carbide, activated carbon or catalysts with wave-absorbing ability, and the wave-transmitting materials are glass or ceramics. The metal tubes 1-6 are arranged between the reaction tubes 1-5, which is conducive to improving the uniformity of the microwave field in the reaction cavity. The reaction tubes 1-5 and the metal tubes 1-6 respectively pass through the metal partitions 1-4 vertically, and both ends of them are fixedly arranged on the two metal tube plates 1-3.

[0037] The feed type of the reactor shell 1-1 of the present invention is gas and / or liquid.

[0038] When the feed type of the reactor shell 1-1 includes gas, both ends of the reaction tube 1-5 are set to be open, a gas inlet 1-9 is set at the lower end of the reactor shell 1-1, and a gas outlet 1-10 is set at the top. The gas feed is directly sprayed into the cavity of the reactor shell 1-1 through the gas inlet 1-9 and then enters the reaction tube.

[0039] When the feed type of the reactor shell 1-1 includes liquid, the following can be used: Figure 1 The reaction tubes 1-5 of the structure are connected in parallel, or as follows Figure 2 The reaction tubes 1-5 of the structure are connected in series.

[0040] Comparison Figure 1Both ends of the reaction tube 1-5 are set to be open, and a liquid distributor 1-2 is arranged inside the upper end of the reactor shell 1-1. The liquid inlet end of the liquid distributor 1-2 is connected to the liquid inlet 1-7. A plurality of drainage pipes are arranged at the bottom of the liquid distributor 1-2. The arrangement of the drainage pipes corresponds to the position of the reaction tube 1-5. The drainage pipes are arranged directly above the reaction tube 1-5, so that the liquid dripping through the liquid distributor 1-2 can evenly enter each reaction tube 1-5.

[0041] Comparison Figure 2 Both ends of the reaction tube 1-5 are set to be openings, and the openings of multiple reaction tubes 1-5 are connected in series through pipelines. The upper end opening of the first reaction tube 1-5 is connected to the liquid inlet 1-7 through a pipeline, and the lower end opening of the last reaction tube 1-5 is connected to the liquid outlet 1-8 through a pipeline.

[0042] In order to regulate the uniformity of microwave field distribution in each reaction cavity, the present application also nails a metal pin 6 on the waveguide 5. The waveguide 5 is a rectangular cavity structure. The metal pin 6 is vertically nailed into the vertical side of the waveguide 5. By adjusting the position and nailing depth of the metal pin 6 on the waveguide 5, a plurality of uniformly distributed strong microwave fields are formed in the corresponding reaction cavity, and there is a weak microwave field between the strong microwave fields. The strong microwave field and the weak microwave field appear in sequence in the direction where the length of the waveguide 5 extends; wherein the material of the metal pin 6 is a stainless steel material that can reflect microwaves, and the metal pin 6 is horizontally arranged and perpendicular to the length extension direction of the waveguide 5.

[0043] When adjusting the penetration depth and position of the metal pin 6 on the waveguide 5, the uniformity of the electric field in the reaction chamber can be determined in two ways: 1) using the multi-physics simulation software COMSOL Multiphysics, modeling is performed according to the actual reactor structure size to simulate the electric field distribution in the reaction chamber. The simulation results are shown in Figure 7 2) The device with the structure as described in 1 is used to determine through experiments that the same mass of silicon carbide is filled in each reaction tube 1-5, and then microwave heating is started to increase the temperature in each reaction tube 1-5 in the reaction chamber, and then water with the same temperature and flow rate is introduced into each reaction tube 1-5, and the outlet water temperature of each reaction tube 1-5 is monitored to indirectly determine whether the microwave field distribution in the reaction chamber is uniform. In this way, the nailing depth and position of the metal pin 6 on the waveguide 5 are regulated, and the difference in the outlet water temperature of each reaction tube 1-5 under each regulation condition is compared, that is, the most suitable parameters of the nailing depth and position of the metal pin 6 on the waveguide 5 can be obtained.

[0044] In the present application, the metal pin 6 is arranged at the vertical middle position of the vertical side of the waveguide 5. By adjusting the horizontal distance of the metal pin 6 compared to the crack of the waveguide crack antenna 4 and its nailing depth, multiple uniformly distributed strong microwave fields are formed in the corresponding reaction cavity.

[0045] In the present invention, the materials of the reactor shell 1-1, the metal tube plate 1-3, the metal partition plate 1-4, the metal tube 1-6, the waveguide slot antenna 4, the waveguide 5 and the metal pin 6 are stainless steel materials that can reflect microwaves.

[0046] In addition Figure 1 In the structure, the reaction tubes 1-5 are arranged in parallel, and the center of the reaction tubes 1-5 can be built with a heat exchanger. Figure 3 An annular space for materials to pass through is formed between the heat exchange tube and the inner wall of the reaction tube 1-5. The lower end of the heat exchange tube passes through the lower end opening of the reaction tube 1-5 and is connected to the heat exchange fluid inlet main pipe. The heat exchange tube passes through the upper end opening of the reaction tube 1-5 and is connected to the heat exchange fluid outlet main pipe. One end of the heat exchange fluid inlet main pipe and one end of the heat exchange fluid outlet main pipe respectively pass through the side wall of the reactor shell 1-1. The heat exchange fluid is introduced into the heat exchange tube to control the reaction temperature in the reaction tube 1-5.

[0047] The metal tubes are arranged between the reaction tubes, which is beneficial to the uniform distribution of the electromagnetic field in the reactor shell.

[0048] The feed of the microwave tube reaction device is gas or liquid. The liquid feed is distributed into the reaction tube by a liquid distributor, and the gas feed is directly sprayed into the cavity by an air inlet pipe and then enters the reaction tube.

[0049] The reaction tube may have a heat exchange tube built in to form an annular gap to control the reaction temperature.

[0050] The reaction tubes are used in parallel or in series to control the reaction residence time. Example 1

[0051] The novel microwave tube reaction device of the present invention comprises a reactor shell 1-1, the cross section of the reactor shell 1-1 is a square, the side length of the square is set in the range of 0.713m-0.721m, the height of the reactor shell 1-1 is 1.2m, and the material thereof is made of stainless steel.

[0052] A metal tube sheet 1-3 is respectively arranged at the upper and lower ends of the interior of the reactor shell 1-1. Four horizontal metal partitions 1-4 are evenly spaced inside the reactor shell 1-1 between the two metal tube sheets 1-3 to divide the internal space of the reactor shell 1-1 into three identical reaction chambers. The metal partitions are made of stainless steel with a thickness of 5 mm. The distance between adjacent metal partitions is 0.22 m, that is, the height of each reaction chamber is 0.22 m.

[0053] Waveguides 5 are symmetrically arranged in the middle of the two opposite side walls of each reaction chamber. The waveguides 5 are rectangular cavity structures. The cross section of the waveguides 5 is rectangular. The side perpendicular to the reactor shell 1-1 is recorded as the long side, and the side parallel to the reactor shell 1-1 is recorded as the wide side. The waveguides 5 are symmetrically distributed on both sides. The waveguides 5 on the same side are connected to a waveguide crack antenna 4. Each crack in the waveguide crack antenna 4 is connected to the corresponding reaction chamber through the waveguide 5. The waveguide crack antenna 4 is then connected to the microwave generator 8 through the circulator 7. The power of the microwave generator 8 is 25 kW. The waveguide crack antenna 4 is used to evenly feed microwave energy into each reaction chamber. The temperature measuring port is set on the middle side of the reactor shell 1-1.

[0054] The waveguide slot antenna 4 is made of metal aluminum. The slot is set on the wide side of the waveguide. The length of the slot is 0.16 m and the width is 0.02 m. There are 3 slots in total on each waveguide slot antenna 4. The 3 slots are connected to the 3 reaction chambers respectively.

[0055] The reaction tubes are arranged in a tube-in-tube manner and vertically pass through metal baffles 1-4. Reaction tubes 1-5 are made of quartz and filled with silicon carbide particles or catalysts with silicon carbide as carriers. The reaction tubes are 0.86 m high and 0.02 m in diameter, and there are 48 of them. Metal tubes 1-6 are arranged at a position with weaker electric field strength and vertically pass through metal baffles and are placed in the reactor shell. Metal tubes 1-6 are made of stainless steel. The metal tubes 1-6 are 0.86 m high and 0.02 m in diameter, and there are 12 of them.

[0056] According to the structural dimensions of the novel microwave tube reactor of Example 1, when the cross-sectional side length of the reactor shell 1-1 is 0.715 m, if the height of the reaction chamber is increased to 0.66 m (that is, two horizontal metal partitions 1-4 are arranged in the reactor shell 1-1 to divide the internal space of the reactor shell 1-1 into a reaction chamber with a height of 0.66 m), the electric field distribution in the reaction chamber will be uneven, such as Figure 5 The single feed inlet excitation in is shown in Figure 1. Common methods to improve uniformity include increasing the number of feed inlets, such as Figure 5 As shown in the multi-feed inlet excitation in the embodiment 1 of the present invention, it is still difficult to meet the electric field distribution requirements of the tubular reactor. Therefore, in Example 1 of the present invention, four metal partitions 1-4 are added to evenly divide the reaction chamber into three layers by electromagnetic field confinement, as shown in FIG. Figure 5 As shown in the electromagnetic field confinement, the electric field distribution in the cavity is uniform, which is suitable for tubular reactors. The reaction tube is added with waveguide slit antenna and metal partition to improve the electric field distribution of the reaction tube. Figure 5The electric field distribution diagram with different numbers of feed-in ports and after adding metal partitions. The electromagnetic field confinement of the metal partitions can achieve the same electric field distribution in different reaction chambers, thereby increasing the length of the reaction tube.

[0057] In Example 1, the microwave power of the microwave generator 8 is set to 25 kW, and the microwave frequency is set to 915 MHz.

[0058] In addition, according to the structural dimensions of the novel microwave tube reactor of Example 1, when the cross-sectional length of the reactor shell 1-1 is 0.715 m, two horizontal metal partitions 1-4 are arranged in the reactor shell 1-1 to divide the internal space of the reactor shell 1-1 into a reaction chamber with a height of 0.22 m. The electric field distribution in the reaction chamber with a single-layer height of 0.22 m is simulated by using the multi-physics simulation software COMSOL Multiphysics. The electric field distribution in the single-layer reaction chamber is uniform. The results are shown in FIG. Figure 4 As shown in the control Figure 4 In the reaction chamber, multiple uniformly distributed strong microwave fields are formed ( Figure 4 The yellow area in the middle shows that there are weak microwave fields between the strong microwave fields ( Figure 4 As shown in the middle blue area, the reaction tubes 1-5 are arranged in the area where the strong microwave field is located, and the metal tubes 1-6 are arranged in the area where the weak microwave field is located. The reaction tubes 1-5 and the metal tubes 1-6 are arranged in parallel in rows, and the straight line where each row of reaction tubes 1-5 or metal tubes 1-6 is located is perpendicular to the length direction of the waveguide 5.

[0059] In addition, the metal tube placed in a place with weak electric field strength can play a role in reducing the influence of interference mode. According to the structural dimensions of the novel microwave tube reactor of Example 1, the cross-sectional side length of the reactor shell 1-1 is in the range of 0.713m-0.721m, and two horizontal metal partitions 1-4 are arranged in the reactor shell 1-1 to separate the internal space of the reactor shell 1-1 into a reaction chamber with a height of 0.22m. The electric field distribution coefficient of the single-layer 0.22m high reaction chamber with and without the metal tube added varies with the reactor side length as shown in the figure. Figure 6 Compared with the case without metal tube, the coefficient of variation of electric field distribution in reaction chambers of different sizes after adding metal tube COV (the ratio of the standard deviation to the mean) has been significantly reduced. Figure 6 As shown in the figure, after adding the metal tube, within a certain range of reactor side length, the COV of the electric field distribution between different reaction tubes decreases to a certain extent. The smaller the coefficient of variation of the electric field strength between different reaction tubes (COV, a dimensionless parameter representing the ratio of the sample standard deviation to the sample mean), the closer the electric field strength between different reaction tubes. Figure 6By examining the side length of the reactor, it can be seen that after adding the metal tube, the processing requirements of the reactor structure are significantly reduced, greatly reducing the processing cost of the reactor.

[0060] The coefficient of variation of the electric field distribution COV The calculation method is as follows: 1) According to the simulation obtained by using the multi-physics simulation software COMSOL Multiphysics Figure 4 The electric field distribution results are used to arrange the reaction tubes 1-5, set probe points in the reaction tubes 1-5 and use the multi-physics simulation software COMSOL Multiphysics to read the electric field data; 2) Calculate the coefficient of variation of the electric field distribution with reference to existing literature COV , such as formula 16 in the document "Microwave heating properties of steel slagasphalt mixture using acoupled electromagnetic and heat transfer model".

[0061] In addition, according to the structural dimensions of the novel microwave tube reactor of Example 1, when the cross-sectional side length of the reactor shell 1-1 is 0.715 m, the reaction chamber is evenly divided into three layers of reaction chambers with a height of 0.22 m by adding four metal partitions 1-4. The multi-physics simulation software COMSOL Multiphysics is used to model the actual reactor structure dimensions, and the BJ-9 standard waveguide is used. The microwave power of the microwave generator 8 is set to 25 kW and the microwave frequency is 915 MHz. The electric field distribution in the reaction chamber is simulated, and the results are as follows: 1) The electric field distribution in the horizontal axial direction of the reaction chamber without adding metal pins is shown in FIG. Figure 7 2) A horizontally mounted metal pin 6 is vertically nailed into the vertical side of the waveguide 5. The metal pin 6 is set in the vertical middle position of the vertical side of the waveguide 5. The multi-physics simulation software COMSOL Multiphysics is used to simulate that by adjusting the horizontal distance of the metal pin 6 relative to the crack of the waveguide crack antenna 4 and its nailing depth, multiple uniformly distributed strong microwave fields are formed in the corresponding reaction cavity. The electric field distribution in the horizontal axial direction of the reaction cavity with the metal pin added is shown in FIG. Figure 7 Right picture. Figure 7 This is a comparison of the electric field distribution of the reaction tube in the axial direction without and with the addition of metal pins. The addition of metal pins improves the uniformity of the electric field distribution between different tubes and also increases the operating range of the microwave tubular reactor.

[0062] Through the method described above of simulating with the multi-physics simulation software COMSOL Multiphysics and measuring the uniformity of the outlet water temperature of different reaction tubes in actual experiments, the position of the metal pin 6 is 12 cm relative to the horizontal distance of the crack of the waveguide crack antenna, and the nailing depth of the metal pin 6 does not exceed 6 cm. Specifically in Example 1 of the present invention, a metal pin 6 is nailed into each waveguide 5, and the diameter of the metal pin 6 is 0.05 m. Compared with the horizontal distance of the crack of the waveguide crack antenna being 12 cm, when the nailing depth is 1 cm, the electric field distribution in the reaction chamber is relatively uniform.

[0063] In summary, the structural parameters of the reactor shell 1-1 optimized in Example 1 of the present invention are as follows: the cross-sectional side length of the reactor shell 1-1 is set to 0.715m, and the reactor shell 1-1 is divided into three reaction chambers with a height of 0.22m. Waveguides 5 are symmetrically arranged in the middle of the side walls on both sides of each reaction chamber, and a metal pin 6 is nailed into each waveguide 5. The diameter of the metal pin 6 is 0.05m, and the horizontal distance of the crack of the waveguide crack antenna is 12cm, and the nailing depth is 1cm. The arrangement of the reaction tubes 1-5 and the metal tubes 1-6 in each reaction chamber, refer to Figure 4 The simulation results are arranged. When the uniformity of the microwave field distribution in the reaction chamber is determined by the water temperature measuring method mentioned above, after obtaining the most suitable parameters of the nailing depth and position of the metal pin 6 on the waveguide 5, the reaction tube 1-5 with a lower water outlet temperature can be replaced by the metal tube 1-6, so that the metal tube 1-6 is arranged between the reaction tubes 1-5, and the reaction tubes 1-5 and the metal tubes 1-6 are respectively arranged in rows in the reactor shell 1-1 corresponding to the regional positions of the strong microwave field and the regional positions of the weak microwave field. Example 2

[0064] The reaction device with optimized structural parameters in Example 1 was used, the power of microwave generator 8 was 25 kW, the microwave frequency was 915 MHz, and the reaction of glycerol dehydration to acrolein was carried out: 20wt% glycerol aqueous solution was used as raw material to carry out gas phase glycerol dehydration reaction to produce acrolein, and the reaction tubes 1-5 were filled with tungsten oxide-supported microwave absorbing catalysts with silicon carbide as carriers. The experimental conditions were: the temperature of the temperature controller was set at 300 °C, the microwave generator power was turned on, and the catalyst bed reached the set temperature and maintained for a period of time. The raw material was dehydrated at the set temperature to generate product acrolein and water, the feed rate was 15 kg / h, and the liquid hourly space velocity of the raw material through the catalyst bed was 0.8h -1 The product enters the subsequent step through the outlet. The reaction results are as follows: When the experiment runs stably for 1 hour, the yield of liquid product of microwave heating glycerol dehydration reaction is 96%, the glycerol conversion rate is 99%, the acrolein yield is 72%, and the glycerol conversion rate can still reach 92% after 20 hours of reaction.

[0065] The microwave absorbing catalyst with tungsten oxide loaded on silicon carbide as a carrier is prepared by an excess impregnation method, wherein the carrier powder is poured into a solution of ammonium metatungstate and stirred thoroughly, and the solution is placed under an infrared lamp and heated at 50°C for 24 hours until dry, and then the temperature is raised to 600°C in a muffle furnace for 3 hours and calcined for 6 hours to obtain a microwave absorbing catalyst loaded with tungsten oxide, wherein the loading amount of tungsten oxide is 15% of the carrier mass, and the preparation is completed.

[0066] In comparison, under the same reaction conditions, a single feed port is used instead of a waveguide slot antenna to feed microwave energy into the entire reaction chamber, that is, the cross-sectional side length of the reactor shell 1-1 is 0.715 m, and the height of the reaction chamber is increased to 0.66 m (that is, two horizontal metal partitions 1-4 are arranged in the reactor shell 1-1 to divide the internal space of the reactor shell 1-1 into a reaction chamber with a height of 0.66 m). The electric field distribution is as follows: Figure 5 The single feed inlet excitation in the reactor structure corresponding to that shown in the figure was used to excite the reaction. The reaction of glycerol dehydration to produce acrolein was carried out under the above conditions. Except for the reactor structure and the microwave introduction method, the other experimental conditions remained unchanged. The experimental results were as follows: when the experiment ran stably for 1 hour, the yield of the liquid product of the microwave-heated glycerol dehydration reaction was 95%, the glycerol conversion rate was 90%, the acrolein yield was 35%, and the glycerol conversion rate was 40% after 20 hours of reaction.

[0067] A waveguide crack antenna is used to feed microwave energy into the entire reaction chamber, and no metal partition and metal pin are set, that is, the structure of the reactor shell 1-1 defined in Example 1 is used, the cross-sectional side length of the reactor shell 1-1 is set to 0.715m, and the reactor shell 1-1 is divided into a reaction chamber with a height of 0.66m. Three waveguides 5 are evenly spaced on one side of the reaction chamber, and three waveguides 5 are also evenly spaced on the other side. The waveguides 5 are symmetrically distributed on both sides, and the waveguides 5 on the same side are connected to a waveguide crack antenna 4. Each crack in the waveguide crack antenna 4 communicates with the corresponding reaction chamber through the waveguide 5. According to the above conditions, the reaction of glycerol dehydration to acrolein is carried out, except that the metal partition and metal pin are not set, and the other experimental conditions remain unchanged. The experimental results are: when the experimental operation is stable for 1h, the yield of liquid product of microwave heating glycerol dehydration reaction is 96%, the glycerol conversion rate is 92%, the acrolein yield is 50%, and the glycerol conversion rate is 68% after 20 hours of reaction.

[0068] A waveguide crack antenna is used to feed microwave energy into the entire reaction chamber, and no metal pins are set, that is, the structure of the reactor shell 1-1 defined in Example 1, the cross-sectional side length of the reactor shell 1-1 is set to 0.715m, and the reactor shell 1-1 is divided into three reaction chambers with a height of 0.22m. Waveguides 5 are symmetrically arranged at the middle position of the opposite side walls of each reaction chamber, and the waveguides 5 are symmetrically distributed on both sides. The waveguides 5 on the same side are connected to a waveguide crack antenna 4, and each crack in the waveguide crack antenna 4 is connected to the corresponding reaction chamber through the waveguide 5. The waveguide crack antenna is used to feed microwave energy uniformly into each reaction chamber, and no metal pins are nailed into the waveguide. According to the above conditions, the reaction of glycerol dehydration to acrolein is carried out, and the other experimental conditions remain unchanged except that the metal pins are not set. The experimental results are: when the experimental operation is stable for 1h, the yield of liquid products of microwave heating glycerol dehydration reaction is 96%, the glycerol conversion rate is 95%, the acrolein yield is 65%, and the glycerol conversion rate is 84% ​​after 20 hours of reaction. Example 3

[0069] The reaction device with optimized structural parameters of Example 1 was used, the power of microwave generator 8 was 25 kW, the microwave frequency was 915 MHz, 25% phosphoric acid aqueous solution was used as raw material for concentration, silicon carbide particles were filled inside reaction tubes 1-5, and the experimental conditions were: the heating temperature was set at 150 °C, the microwave generator power was turned on, the reaction tube bed reached the set temperature and maintained for a period of time, the feed rate of 25% phosphoric acid aqueous solution was 30 kg / h, and the residence time of the raw material in the silicon carbide particle bed was 0.43 h. The raw material was concentrated at the set temperature to obtain a high-concentration phosphoric acid aqueous solution, and the concentrated liquid was discharged from the liquid outlet at the bottom of the reactor shell. The results of the embodiment are as follows: Microwave heating phosphoric acid dehydration concentration can concentrate 25% dilute phosphoric acid into 78% concentrated phosphoric acid. Example 4

[0070] The reaction device with optimized structural parameters in Example 1 was used, the power of microwave generator 8 was 25 kW, the microwave frequency was 915 MHz, soybean oil and methanol were used as raw materials for transesterification reaction under KOH catalyst, wherein the molar ratio of soybean oil:methanol was 1:5, the amount of KOH was 1% of the mass of soybean oil, the reaction tubes 1-5 were filled with silicon carbide particles, and the openings of the reaction tubes were connected in series through pipelines, and the structure was as follows: Figure 2 As shown in the figure, the experimental conditions are: the heating temperature is set at 60 °C, the microwave generator power is turned on, the reaction tube bed reaches the set temperature and maintains it for a period of time, and the residence time of the raw material in the silicon carbide particle bed is 1.6 h. The raw material undergoes an ester exchange reaction at the set temperature to obtain biodiesel, and the product is discharged through the liquid outlet at the bottom of the reactor shell. The results of the embodiment are as follows: the soybean oil feed rate is 8 kg / h, and the biodiesel yield is 95%. Example 5

[0071] A reaction device with optimized structural parameters in Example 1 was used, the power of microwave generator 8 was 25 kW, the microwave frequency was 915 MHz, fatty acid methyl ester (iodine value 100), formic acid and hydrogen peroxide were used as raw materials for epoxidation reaction to prepare epoxy fatty acid methyl ester, the molar ratio of fatty acid methyl ester: hydrogen peroxide: formic acid was 1:1.5:0.23, the reaction tubes 1-5 were filled with silicon carbide particle fillers, and the fillers were built with heat exchange tubes, and the structure was as follows Figure 3 As shown in the figure, the experimental conditions are: the heating temperature is set at 80 °C, the microwave generator power is turned on, the temperature of the bed of the reaction tube reaches the set temperature and is maintained for a period of time, and the residence time of the raw material in the silicon carbide particle bed is 0.85 h. While feeding, the cooling water is turned on to allow the cooling water to pass into the heat exchange tube, and the temperature of the entire bed of the reaction tube is maintained between 75 °C and 80 °C. The raw material is epoxidized at the set temperature to obtain epoxy fatty acid methyl ester, and the product enters the subsequent step from the outlet. The results of the embodiment are as follows: the feed rate of fatty acid methyl ester is 15 kg / h, the conversion rate of fatty acid methyl ester in the epoxidation reaction is 96%, and the selectivity of epoxy fatty acid methyl ester is 81%.

[0072] It is understandable that for those skilled in the art, any equivalent replacement or change to the technical solution and inventive concept of the present invention should fall within the protection scope of the claims attached to the present invention.

Claims

1. A microwave tube reaction device, characterized in that The invention comprises a microwave generator (8), a circulator (7), a waveguide slit antenna (4), a waveguide (5), an infrared probe (2), a temperature controller (3) and a reactor shell (1-1), wherein a metal tube plate (1-3) is respectively arranged at the upper and lower ends of the reactor shell (1-1), a plurality of horizontal metal partitions (1-4) are evenly spaced in the reactor shell (1-1) between the two metal tube plates (1-3), the metal partitions (1-4) divide the internal space of the reactor shell (1-1) into a plurality of identical reaction chambers, waveguides (5) are symmetrically arranged at the middle positions of the two opposite side walls of each reaction chamber, the waveguides (5) are symmetrically distributed on both sides, the waveguides (5) on the same side are connected to a waveguide slit antenna (4), each slit in the waveguide slit antenna (4) is connected to the corresponding reaction chamber through the waveguide (5), and the waveguide slit antenna (4) is further connected to the microwave generator (8) through the circulator (7); A plurality of reaction tubes (1-5) and metal tubes (1-6) are arranged in an array in the reactor shell (1-1); the metal tubes (1-6) are arranged between the reaction tubes (1-5); the reaction tubes (1-5) and the metal tubes (1-6) respectively pass through the metal partition plate (1-4) vertically, and both ends of the reaction tubes (1-5) and the metal tubes (1-6) are fixedly arranged on the two metal tube plates (1-3); A temperature measuring port (1-11) is provided on the side of the reactor shell (1-1), and an infrared probe (2) measures the temperature inside the reaction chamber through the temperature measuring port (1-11). The infrared probe (2) is then connected to the microwave generator (8) through a temperature controller (3). The reaction tubes (1-5) are made of wave-transmitting material; A metal pin (6) is nailed into the side of the waveguide (5). By adjusting the side position and nailing depth of the metal pin (6) on the waveguide (5), a plurality of evenly distributed strong microwave fields are formed in the corresponding reaction chamber, and a weak microwave field exists between the strong microwave fields. The strong microwave field and the weak microwave field are arranged in sequence in the direction where the length of the waveguide (5) extends. The reaction tubes (1-5) and the metal tubes (1-6) are arranged in rows in the reactor shell (1-1) corresponding to the area where the strong microwave field is located and the area where the weak microwave field is located. The direction in which the waveguide (5) transmits microwaves is recorded as the direction in which its length extends. The metal pin (6) is made of stainless steel that can reflect microwaves. The metal pin (6) is arranged horizontally and perpendicular to the direction in which the length of the waveguide (5) extends. The height of each reaction cavity is 0.4-0.9 times of one microwave wavelength.

2. A microwave tube reaction device as claimed in claim 1, characterized in that The feed type of the reactor shell (1-1) is gas and / or liquid. When the feed type includes gas, both ends of the reaction tube (1-5) are arranged to be open. The lower end of the reactor shell (1-1) is provided with a gas inlet (1-9), and the top is provided with a gas outlet (1-10). The gas feed is directly sprayed into the cavity at the lower part of the reactor shell (1-1) through the gas inlet (1-9) and then enters the reaction tube. It is then collected in the cavity at the upper part of the reactor shell (1-1) and then discharged from the gas outlet (1-10). When the feed type includes liquid, the top and bottom of the reactor shell (1-1) are respectively provided with a liquid inlet (1-7) and a liquid outlet (1-8). The liquid introduced through the liquid inlet (1-7) can enter the reaction tube (1-5) and finally be discharged from the liquid outlet (1-8).

3. A microwave tube reaction device as claimed in claim 2, characterized in that The feed type includes liquid, both ends of the reaction tube (1-5) are arranged as openings, a liquid distributor (1-2) is arranged inside the upper end of the reactor shell (1-1), the liquid inlet end of the liquid distributor (1-2) is connected to the liquid inlet (1-7), a plurality of drainage pipes are arranged at the bottom of the liquid distributor (1-2), the arrangement of the drainage pipes corresponds to the position of the reaction tube (1-5), and the drainage pipes are arranged directly above the upper opening of the reaction tube (1-5), so that the liquid dripping down through the liquid distributor (1-2) can evenly enter each reaction tube (1-5).

4. A microwave tube reaction device as claimed in claim 3, characterized in that The center of the reaction tube (1-5) can contain a heat exchange tube, and an annular space for materials to pass through is formed between the heat exchange tube and the inner wall of the reaction tube (1-5). The lower end of the heat exchange tube passes through the lower end opening of the reaction tube (1-5) and is connected to the heat exchange fluid inlet main pipe. The heat exchange tube passes through the upper end opening of the reaction tube (1-5) and is connected to the heat exchange fluid outlet main pipe. One end of the heat exchange fluid inlet main pipe and one end of the heat exchange fluid outlet main pipe respectively pass through the side wall of the reactor shell (1-1). The heat exchange fluid is introduced into the heat exchange tube to control the reaction temperature in the reaction tube (1-5).

5. A microwave tube reaction device as claimed in claim 2, characterized in that The feed type includes liquid, both ends of the reaction tube (1-5) are arranged to be openings, the openings of the plurality of reaction tubes (1-5) are connected in series via pipelines, the upper end opening of the first reaction tube (1-5) is connected to the liquid inlet (1-7) via a pipeline, and the lower end opening of the last reaction tube (1-5) is connected to the liquid outlet (1-8) via a pipeline, so that the liquid introduced through the liquid inlet (1-7) can flow from the first reaction tube (1-5) to the last reaction tube (1-5) and finally be discharged from the liquid outlet (1-8).

6. A microwave tube reaction device as claimed in claim 1, characterized in that The waveguide (5) is a rectangular cavity structure, and the metal pin (6) is arranged at a vertical middle position of a vertical side surface of the waveguide (5). By adjusting the horizontal distance of the metal pin (6) relative to the crack of the waveguide crack antenna (4) and the depth of its insertion, a plurality of evenly distributed strong microwave fields are formed in the corresponding reaction cavity.

7. A microwave tube reaction device as claimed in claim 1, characterized in that The shell (1-1), the metal tube plate (1-3), the metal partition plate (1-4), the metal tube (1-6), the waveguide slot antenna (4) and the waveguide (5) are made of stainless steel that can reflect microwaves.

8. A microwave tube reaction device as claimed in claim 1, characterized in that The reaction tubes (1-5) and the metal tubes (1-6) are arranged in parallel in a row, and the straight line where each row of reaction tubes (1-5) or metal tubes (1-6) is located is perpendicular to the length direction of the waveguide (5), and the direction in which the waveguide (5) transmits microwaves is recorded as the direction in which its length extends; The reaction tubes (1-5) are arranged in a tube-in-tube manner and are made of a wave-transmitting and high-temperature-resistant material such as quartz or polytetrafluoroethylene. Depending on the polarity of the feed material, the reaction tubes are filled with a wave-absorbing material or a wave-transmitting material. The wave-absorbing material is silicon carbide, activated carbon, or a catalyst with wave-absorbing ability, and the wave-transmitting material is glass or ceramic.

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