A reaction system and method for producing silicon nitride

Abstract

The present invention provides a reaction system for producing silicon nitride, comprising: a reaction tower and a heat transfer component; the heat transfer component is installed on the reaction tower; a micro-interface unit is arranged in the reaction tower, the micro-interface unit comprises a micro-interface generator and an expansion tube located above the micro-interface generator, the bottom of the expansion tube is connected to the micro-interface generator; the top of the expansion tube is connected to a silicon tetrachloride delivery pipeline, and the micro-interface generator is connected to a liquid ammonia delivery pipeline. The reaction system for producing silicon nitride of the present invention can realize solvent-free production, has low production cost, and produces silicon nitride powder with uniform particle size and high fineness.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon nitride preparation, and in particular to a reaction system and method for producing silicon nitride. Background Art

[0002] Silicon nitride is an inorganic substance with the chemical formula Si3N4. It is an important structural ceramic material with high hardness, lubricity, atomic crystal, wear resistance, and oxidation resistance at high temperatures. It can also resist thermal shocks and will not break even if it is heated to more than 1000°C in the air, cooled rapidly, and then heated rapidly. It is precisely because silicon nitride ceramics have such excellent properties that people often use it to manufacture mechanical components such as bearings, turbine blades, mechanical seal rings, and permanent molds.

[0003] The prior art prepares silicon nitride powder by a low-temperature liquid phase method, that is, liquid ammonia is reacted with an organic solution of silicon tetrachloride at a low temperature of -40°C to obtain an intermediate product, silyl imine, and a by-product, ammonium chloride, which are then filtered, washed, and heat-treated to obtain silicon nitride powder. The reaction process requires controlling heat release so that the system temperature is always maintained at -40°C and the pressure in the reactor is approximately a slight positive pressure.

[0004] However, the existing technology processes are facing the following problems:

[0005] First, the reaction is highly exothermic, with an instantaneous temperature rise of 10 to 20°C, which makes it difficult to stably control the reaction temperature in the tower.

[0006] Second: Although the added organic solvent can dilute silicon tetrachloride and control the reaction rate, it is difficult to separate the required relatively pure product in subsequent operations due to the addition of organic solvent, which increases the cost;

[0007] Third: The conversion rate of this reaction is extremely high and the reaction speed is also very fast, but it is difficult to control the particle size with the current existing technology. One reason is that the particle size distribution is not uniform enough, and the other is that the particle size is not fine enough. It is difficult to achieve the micron scale level, and it is impossible to achieve continuous production of the entire process.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] The first object of the present invention is to provide a reaction system for producing silicon nitride, which realizes solvent-free production of silicon nitride and overcomes the problems of violent reaction exotherm and difficult control of particle size in the prior art.

[0010] The second object of the present invention is to provide a method using the above reaction system, which is simple to operate and can produce silicon nitride with uniform and fine particle size.

[0011] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0012] The present invention provides a reaction system for producing silicon nitride, comprising: a reaction tower and a heat transfer component; the heat transfer component is installed on the reaction tower; a micro-interface unit is arranged in the reaction tower, the micro-interface unit comprises a micro-interface generator and an expansion tube located above the micro-interface generator, the bottom of the expansion tube is connected to the micro-interface generator; the top of the expansion tube is connected to a silicon tetrachloride delivery pipeline, and the micro-interface generator is connected to a liquid ammonia delivery pipeline.

[0013] In the prior art, the production of silicon nitride is highly exothermic, with an instantaneous temperature rise of up to 10 to 20°C, which makes it difficult to stably control the reaction temperature in the tower. At the same time, in order to control the reaction rate, an organic solvent needs to be used, but the organic solvent is difficult to separate in subsequent steps, and the separation process increases the cost. In addition, the silicon nitride produced by the prior art has an uneven particle size distribution and is not fine enough, which affects the quality of the product.

[0014] In order to solve the above technical problems, the present invention provides a reaction system for producing silicon nitride. The reaction system can disperse and break the raw materials into micro droplets at the micron level by setting a micro-interface unit, thereby increasing the mass transfer area between the oil and water phases, thereby enhancing the effect of the reaction; by setting a heat transfer component, the heat released by the reaction can be removed in time, thereby achieving the control of the reaction temperature in the tower, and at the same time providing conditions for the solvent-free production of silicon nitride.

[0015] Preferably, a circulation pipeline is arranged outside the reaction tower, the inlet of the circulation pipeline is connected to the side wall of the reaction tower, and the outlet is connected to the top of the expansion tube; and a heat exchanger is arranged on the circulation pipeline.

[0016] Preferably, the heat transfer assembly comprises a coil and an outer jacket, the coil is coiled on the inner wall of the reaction tower, and the outer jacket is sleeved on the outer wall of the reaction tower.

[0017] Preferably, a discharger is provided at the bottom of the reaction tower; the discharger is funnel-shaped, and the reaction product in the reaction tower flows out through the discharger. The reaction product is solid silimide crystals, and the funnel-shaped discharger can prevent the outlet from being blocked.

[0018] Preferably, the diameter of the expansion tube increases gradually from top to bottom, and the bottom of the expansion tube contacts the top wall of the microinterface generator, so that each fluid can be fully mixed here, because the Reynolds number of the fluid in this tube is higher, the turbulence is more intense, and the mixing effect is better.

[0019] The reaction system of the present invention does not need to use a solvent in the process of producing silicon nitride, thereby avoiding the separation problem in subsequent treatment, which is beneficial to ensuring the purity of the product and saving costs. In addition, by setting a heat transfer component composed of a coil and an outer jacket in the reaction tower, the reaction exotherm can be removed in time, thereby ensuring the stability of the reaction temperature in the tower, effectively preventing the system collapse caused by the reaction exotherm, and because real-time heat transfer is achieved, the reaction speed is no longer a constraint on the production of silicon nitride, creating conditions for achieving solvent-free production, the product purity is also greatly improved, and the ammonium chloride by-product can be purified more simply in the follow-up, realizing the collection and reuse of the by-product. The present invention realizes a solvent-free preparation scheme through a specific heat transfer component setting method, greatly reducing production costs, and improving production efficiency.

[0020] The present invention also combines micro-interface technology with the production process of silicon nitride. Specifically, during the reaction, raw liquid ammonia and silicon tetrachloride can enter from the micro-interface unit and be directly sent to the inside of the reaction tower after micro-interface emulsification. In this way, not only the reaction is enhanced by increasing the mass transfer area between the two phases to greatly improve the production efficiency, but also micron-sized silanimide intermediates can be effectively generated in the micron-sized reaction system, and the use of micro-interface technology can also make the particle size distribution of the powder generated by the reaction more uniform.

[0021] The micro-interface unit of the present invention is composed of a micro-interface generator and an expansion tube. Liquid ammonia directly enters the micro-interface generator, and silicon tetrachloride enters the micro-interface generator through the expansion tube. In this way, the two liquid flows can collide in the micro-interface generator. At the same time, under the action of the micro-interface generator, the pressure energy of silicon tetrachloride and liquid ammonia transported into the tower is converted into droplet surface energy and transmitted to silicon tetrachloride and liquid ammonia, so that the two are broken to form a micron-scale oil-water two-phase reaction system to react in the tower, thereby increasing the mass transfer area between the two phases, strengthening the reaction within a preset condition range, and generating micron-scale silanimide powder by reaction.

[0022] The reaction tower of the present invention is also provided with a circulation pipeline outside. On the one hand, the circulation pipeline can continuously circulate the reaction liquid in an external circulation manner, and send the reaction liquid into the expansion tube to be mixed with silicon tetrachloride and enter the micro-interface generator, which is beneficial to the depth of the reaction; on the other hand, the heat of reaction can be removed in time by the heat exchanger arranged on the circulation pipeline, which cooperates with the heat transfer component to achieve a better temperature control effect, which is beneficial to the constant temperature in the tower.

[0023] Those skilled in the art will appreciate that the microinterface generator used in the present invention has been embodied in the inventor's prior patents, such as patents with application numbers CN201610641119.6, CN201610641251.7, CN201710766435.0, CN106187660, CN105903425A, CN109437390A, CN205833127U and CN207581700U. The prior patent CN201610641119.6 describes in detail the specific product structure and working principle of the micron bubble generator (i.e., microinterface generator). The application document states that "the micron bubble generator includes a main body and a secondary crushing member, the main body has a cavity, the main body is provided with an inlet connected to the cavity, the first and second opposite ends of the cavity are open, wherein the cross-sectional area of ​​the cavity decreases from the middle of the cavity to the first and second ends of the cavity; the secondary crushing member is provided at at least one of the first and second ends of the cavity, a portion of the secondary crushing member is provided in the cavity, and an annular channel is formed between the secondary crushing member and the through holes open at both ends of the cavity. The micron bubble generator also includes an air inlet pipe and a liquid inlet pipe." From the specific structure disclosed in the application document, it can be known that its specific working principle is: the liquid enters the micron bubble generator tangentially through the liquid inlet pipe, rotates at ultra-high speed and cuts the gas, so that the gas bubbles are broken into micron-level microbubbles, thereby increasing the mass transfer area between the liquid phase and the gas phase, and the micron bubble generator in the patent belongs to a pneumatic microinterface generator.

[0024] In addition, the prior patent 201610641251.7 records that the primary bubble breaker has a circulating liquid inlet, a circulating gas inlet and a gas-liquid mixture outlet, and the secondary bubble breaker connects the feed port with the gas-liquid mixture outlet, indicating that the bubble breaker requires gas-liquid mixture to enter. In addition, it can be seen from the following figures that the primary bubble breaker mainly uses circulating liquid as power, so the primary bubble breaker is actually a hydraulic micro-interface generator, and the secondary bubble breaker simultaneously passes the gas-liquid mixture into an elliptical rotating ball for rotation, thereby achieving bubble breaking during the rotation process, so the secondary bubble breaker is actually a gas-liquid linkage micro-interface generator. In fact, whether it is a hydraulic micro-interface generator or a gas-liquid linkage micro-interface generator, it is a specific form of a micro-interface generator. However, the micro-interface generator adopted by the present invention is not limited to the above-mentioned forms. The specific structure of the bubble breaker recorded in the prior patent is only one of the forms that the micro-interface generator of the present invention can adopt.

[0025] In addition, the prior patent 201710766435.0 records that "the principle of the bubble breaker is a high-speed jet to achieve mutual collision of gases", and also explains that it can be used in a micro-interface enhanced reactor, verifying the correlation between the bubble breaker and the micro-interface generator itself; and the prior patent CN106187660 also has relevant records on the specific structure of the bubble breaker, see paragraphs

[0031] -

[0041] in the specification, and the attached drawings, which have a detailed description of the specific working principle of the bubble breaker S-2. The top of the bubble breaker is a liquid phase inlet, and the side is a gas phase inlet. The liquid phase coming in from the top provides suction power, thereby achieving the effect of crushing into ultrafine bubbles. It can also be seen in the attached drawings that the bubble breaker has a conical structure, and the diameter of the upper part is larger than the diameter of the lower part, so that the liquid phase can better provide suction power.

[0026] Since the micro-interface generator was just developed in the early stage of the prior patent application, it was named micron bubble generator (CN201610641119.6), bubble breaker (201710766435.0), etc. in the early stage. With the continuous technical improvement, it was later renamed as micro-interface generator. Now the micro-interface generator and micro-interface generator in the present invention are equivalent to the previous micron bubble generator, bubble breaker, etc., but the names are different. In summary, the micro-interface generator of the present invention belongs to the prior art.

[0027] Preferably, the inlet of the circulation pipeline includes a first inlet and a second inlet, and the first inlet is located above the second inlet. During production, different inlets can be selected to realize the circulation of the reaction liquid according to the liquid level in the tower.

[0028] Preferably, a first baffle is provided in the reaction tower, the top of the first baffle is higher than the first inlet in the vertical direction, and the bottom of the first baffle is located between the first inlet and the second inlet in the vertical direction.

[0029] Preferably, a second baffle is provided in the reaction tower, the top of the second baffle is located between the first inlet and the second inlet in the vertical direction, and the bottom of the second baffle is located below the second inlet in the vertical direction.

[0030] The present invention can prevent silimide crystals generated in the tower during the external circulation process from entering the circulation pipeline to block or damage components on the pipeline by respectively arranging the first baffle and the second baffle, thereby improving the overall service life.

[0031] Preferably, a washing filter is further included, the discharger is connected to the washing filter, the filter residue outlet of the washing filter is connected to a silicon nitride output pipeline, and the filtrate outlet of the washing filter is connected to a recovery pipeline.

[0032] Preferably, a screw conveyor is provided in the washing filter, and the filter residue is output through the screw conveyor; and a liquid ammonia washing liquid delivery pipeline is provided above the washing filter.

[0033] Preferably, the silicon nitride output pipeline includes a programmed temperature furnace and a silicon nitride delivery pipeline, and the filter residue is output from the silicon nitride delivery pipeline after being processed by the programmed temperature furnace.

[0034] Preferably, the recovery pipeline comprises a crude ammonium chloride storage tank, an ammonia evaporator and an ammonia condenser. After the filtrate filtered out by the washing filter is treated by the ammonia evaporator, the obtained ammonia gas enters the ammonia condenser, and the obtained crude ammonium chloride enters the crude ammonium chloride storage tank.

[0035] The present invention also provides a method for producing silicon nitride, and the silicon nitride is produced by applying the above production system.

[0036] The method is simple to operate and can produce silicon nitride powder with uniform and fine particle size.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) Solvent-free: The present invention adopts a solvent-free production method for silicon nitride, which avoids the separation problem in subsequent processing. In addition, the invention adopts a multi-stage heat transfer method, so there is no need to worry about the system collapse due to obvious heat release. The reaction speed is no longer a constraint on the production of silicon nitride, and the product purity is greatly improved. In addition, the ammonium chloride byproduct can be purified more easily in the subsequent process.

[0039] (2) Continuous production: The reaction system of the present invention can achieve continuous production, and the liquid ammonia in the reaction process can be continuously recycled;

[0040] (3) The product has uniform particle size and high fineness: After the present invention changes the traditional silicon nitride preparation process into a micro-interface strengthening process, the raw materials of liquid ammonia and silicon tetrachloride can enter from the micro-interface unit, and then be directly sent to the inside of the reaction tower after micro-interface emulsification. In this way, not only the reaction is enhanced by increasing the mass transfer area between the two phases and greatly improving the production efficiency, but also the micron-sized silanimide intermediate can be effectively generated in the micron-sized reaction system. The use of micro-interface technology can also make the particle size distribution of the powder generated by the reaction more uniform. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0042] Figure 1 A schematic diagram of the structure of a reaction system provided in an embodiment of the present invention. Description of the drawings:

[0044] 1-heat exchanger; 2-silicon tetrachloride delivery pipeline;

[0045] 3- flushing pipeline; 4- expansion tube;

[0046] 5-first baffle; 6-second baffle;

[0047] 7-micro interface generator; 8-coil;

[0048] 9-liquid ammonia delivery pipeline; 10-external jacket;

[0049] 11-discharger; 12-washing filter;

[0050] 13-liquid ammonia washing liquid delivery pipeline; 14-screw conveyor;

[0051] 15-programmed temperature furnace; 16-silicon nitride delivery pipeline;

[0052] 17- reflux pipeline; 18- ammonia condenser;

[0053] 19- ammonia evaporator; 20- crude ammonium chloride storage tank;

[0054] 21- ammonium chloride crude product delivery pipeline; 22- circulation pump;

[0055] 23-nitrogen pressurizing device; 24-reaction tower;

[0056] 25-circulation pipeline; 26-first inlet;

[0057] 27- Second import. DETAILED DESCRIPTION

[0058] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0059] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0060] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] In order to more clearly explain the technical solution of the present invention, it is described in the form of specific embodiments below.

[0062] Example 1

[0063] See also Figure 1 The present embodiment provides a reaction system for producing silicon nitride, comprising: a reaction tower 24 and a heat transfer component, the heat transfer component being installed on the reaction tower 24; a micro-interface unit is arranged in the reaction tower 24, the micro-interface unit comprises a micro-interface generator 7 and an expansion tube 4 located above the micro-interface generator 7, the bottom of the expansion tube 4 is connected to the micro-interface generator 7; the top of the expansion tube 4 is connected to a silicon tetrachloride delivery pipeline 2, and the micro-interface generator 7 is connected to a liquid ammonia delivery pipeline 9. The diameter of the expansion tube 4 of the present embodiment gradually increases from top to bottom, and the bottom of the expansion tube 4 contacts the top wall of the micro-interface generator 7.

[0064] Among them, the heat transfer component includes a coil 8 and an outer jacket 10. The coil 8 is coiled and arranged on the inner wall of the reaction tower 24, and the outer jacket 10 is sleeved on the outer wall of the reaction tower 24. In actual use, low-temperature heat transfer oil is introduced into the coil 8, and -55℃ / -65℃ ethylene glycol aqueous solution or low-temperature heat transfer oil is introduced into the outer jacket 10 for cold preservation.

[0065] In this embodiment, a circulation pipeline 25 is arranged outside the reaction tower 24 , the inlet of the circulation pipeline 25 is connected to the side wall of the reaction tower 24 , and the outlet is connected to the top of the expansion tube 4 ; the circulation pipeline 25 is provided with a heat exchanger 1 and a circulation pump 22 .

[0066] Specifically, the inlet of the circulation pipeline 25 includes a first inlet 26 and a second inlet 27, and the first inlet 26 is located above the second inlet 27. During production, the outlet of the circulation pipeline 25 can select different inlets according to the liquid level in the tower to realize the circulation of the reaction liquid.

[0067] The top of the reaction tower 24 is also connected to a flushing pipeline 3, which is used to prevent blockage inside the reaction tower 24. When blockage occurs in the reaction tower 24, an organic solvent can be introduced through the flushing pipeline 3 to clear the blockage.

[0068] In order to prevent the silyl imine crystals generated during the circulation process from entering the circulation pipeline 25, a first baffle 5 and a second baffle 6 are provided in the reaction tower 24, wherein the top of the first baffle 5 is higher than the first inlet 26 in the vertical direction, and the bottom is located between the first inlet 26 and the second inlet 27 in the vertical direction. The top of the second baffle 6 is located between the first inlet 26 and the second inlet 27 in the vertical direction, and the bottom is located below the second inlet 27 in the vertical direction.

[0069] Since the product silyl imine obtained by the reaction in the reaction tower 24 is crystallized into a solid state, a discharger 11 is provided at the bottom of the reaction tower 24 for easy collection; the discharger 11 is funnel-shaped, and the reaction product in the reaction tower 24 flows out through the discharger 11.

[0070] The reaction system of this embodiment further includes a washing filter 12, the discharger 11 is connected to the washing filter 12, the residue outlet of the washing filter 12 is connected to a silicon nitride output pipeline, and the filtrate outlet of the washing filter 12 is connected to a recovery pipeline.

[0071] A screw conveyor 14 is provided in the washing filter 12, and the filter residue is output through the screw conveyor 14 and enters the silicon nitride output pipeline; a liquid ammonia washing liquid delivery pipeline 13 is provided above the washing filter 12. In addition, in order to improve the filtering efficiency in the washing filter 12, a nitrogen pressurizing device 23 can also be provided to increase the filtering pressure.

[0072] The silicon nitride output pipeline includes a programmed temperature furnace 15 and a silicon nitride delivery pipeline 16 . The filter residue is processed by the programmed temperature furnace 15 to generate the final product silicon nitride, and the generated silicon nitride is output from the silicon nitride delivery pipeline 16 .

[0073] The recovery pipeline includes a crude ammonium chloride storage tank 20, an ammonia evaporator 19 and an ammonia condenser 18. After the filtrate filtered out by the washing filter 12 is treated by the ammonia evaporator 19, the obtained ammonia gas enters the ammonia condenser 18, and the obtained crude ammonium chloride enters the crude ammonium chloride storage tank 20. After the ammonia gas is cooled into liquid ammonia in the ammonia condenser 18, the liquid ammonia is sent to the liquid ammonia delivery pipeline 9 through the reflux pipeline 17 thereon. The crude ammonium chloride storage tank 20 is connected to a crude ammonium chloride delivery pipeline 21 for outputting the crude ammonium chloride.

[0074] The method for producing silicon nitride by the reaction system of this embodiment is as follows:

[0075] Before the reaction, the whole system is replaced with nitrogen, and the silicon tetrachloride and liquid ammonia are cooled to -35°C to -45°C and then fed into the micro-interface unit; the silicon tetrachloride and liquid ammonia are dispersed and crushed into micro-droplets in the micro-interface unit and then fed into the reaction tower 24 for reaction, and the generated product is fed into the washing filter 12, sprayed with liquid ammonia for washing 4-5 times until the ammonium chloride is completely dissolved in the liquid ammonia filtrate, and the obtained filter residue is fed into the programmed temperature furnace 15 to obtain the product silicon nitride and output through the silicon nitride output pipeline; the filtrate obtained by washing is fed into the ammonia evaporator 19, and the ammonia gas obtained by evaporation is cooled into liquid ammonia in the ammonia condenser 18 and then fed into the liquid ammonia delivery pipeline 9 for reuse, and the crude ammonium chloride obtained after evaporation enters the crude ammonium chloride storage tank 20 and is output to the purification process through the crude ammonium chloride delivery pipeline 21.

[0076] After testing, the produced silicon nitride powder has uniform particle size, ranging from 1 μm to 3 μm.

[0077] Example 2

[0078] The only difference between this example and Example 1 is that in this example the bottom of the expansion tube 4 penetrates deep into the micro-interface generator 7 .

[0079] After testing, the produced silicon nitride powder has uniform particle size, with a particle size between 2μm and 6μm.

[0080] Comparative Example 1

[0081] The only difference between this example and Example 1 is that the micro-interface unit is not used.

[0082] After testing, the produced silicon nitride powder has a relatively uniform particle size, ranging from 5μm to 20μm.

[0083] By comparing the silicon nitride powder produced in Example 1 with that produced in Example 2, it can be seen that although the minimum particle size of the silicon nitride powder in Example 1 is basically the same as that in Example 2, the particle size distribution of the silicon nitride powder in Example 1 is narrower, and the overall particle size performance is finer. This may be because the expansion tube directly penetrates into the micro-interface generator, affecting the residence time of silicon tetrachloride and the circulating liquid itself in the micro-interface generator, and at the same time affecting the hedging effect between silicon tetrachloride and the circulating liquid and liquid ammonia. This shows that the best quality silicon nitride can only be obtained when the bottom of the expansion tube is directly in contact with the top wall of the micro-interface generator.

[0084] Compared with the silicon nitride powder produced in Example 1, it can be seen that the silicon nitride powder in Example 1 has a finer particle size, a narrower particle size distribution, and better uniformity, indicating that the use of micro-interface technology can improve the uniformity of silicon nitride and make the generated silicon nitride powder finer.

[0085] In summary, compared with the prior art, the reaction system for producing silicon nitride of the present invention can achieve solvent-free production, has low production cost, and produces silicon nitride powder with uniform particle size and high fineness.

[0086] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reaction system for producing silicon nitride, It is characterized in that include: A reaction tower and a heat transfer component, wherein the heat transfer component is installed on the reaction tower; a micro-interface unit is arranged in the reaction tower, wherein the micro-interface unit comprises a micro-interface generator and an expansion tube located above the micro-interface generator, wherein the bottom of the expansion tube is connected to the micro-interface generator; a silicon tetrachloride delivery pipeline is connected to the top of the expansion tube, and a liquid ammonia delivery pipeline is connected to the micro-interface generator; The heat transfer assembly comprises a coil and an outer jacket, wherein the coil is wound around the inner wall of the reaction tower, and the outer jacket is sleeved on the outer wall of the reaction tower; The diameter of the expansion tube gradually increases from top to bottom, and the bottom of the expansion tube contacts the top wall of the micro-interface generator.

2. The reaction system according to claim 1, It is characterized in that A circulation pipeline is arranged outside the reaction tower, the inlet of the circulation pipeline is connected to the side wall of the reaction tower, and the outlet is connected to the top of the expansion tube; a heat exchanger is arranged on the circulation pipeline.

3. The reaction system according to claim 1, It is characterized in that A discharger is provided at the bottom of the reaction tower; the discharger is in the shape of a funnel, and the reaction products in the reaction tower flow out through the discharger.

4. The reaction system according to claim 2, It is characterized in that The inlet of the circulation pipeline includes a first inlet and a second inlet, and the first inlet is located above the second inlet.

5. The reaction system according to claim 4, It is characterized in that A first baffle is arranged in the reaction tower, wherein the top of the first baffle is higher than the first inlet in the vertical direction, and the bottom of the first baffle is located between the first inlet and the second inlet in the vertical direction.

6. The reaction system according to claim 5, It is characterized in that A second baffle is arranged in the reaction tower, wherein the top of the second baffle is located between the first inlet and the second inlet in the vertical direction, and the bottom of the second baffle is located below the second inlet in the vertical direction.

7. The reaction system according to claim 3, It is characterized in that It also includes a washing filter, the discharger is connected to the washing filter, the filter residue outlet of the washing filter is connected to a silicon nitride output pipeline, and the filtrate outlet of the washing filter is connected to a recovery pipeline.

8. The reaction system according to claim 7, It is characterized in that A screw conveyor is arranged inside the washing filter, and the filter residue is output through the screw conveyor; a liquid ammonia washing liquid conveying pipeline is arranged above the washing filter.

9. A method for producing silicon nitride, It is characterized in that Silicon nitride is produced using the reaction system described in any one of claims 1 to 8.

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