Continuous production method and device for high-purity superfine boron carbide

Abstract

The invention relates to the technical field of boron carbide production, in particular to a continuous production method and device for high-purity superfine boron carbide, and the production method comprises the following steps: S1, preparing materials; boric acid, glucose and PVA are prepared and dissolved in water to prepare a boric acid solution, a glucose solution and a PVA solution for standby application; step S2, pulping; adding a glucose solution into the boric acid solution in the stirring process, and stirring and mixing for 3-4 hours to obtain a mixed solution; adding a PVA solution into the mixed solution, stirring and mixing, and injecting into a graphite mold; s3, performing dehydration, carbonization and carbon thermal reduction reaction to generate boron carbide; and S4, boron carbide purification. Compared with the prior art, a complex can be formed between boric acid and glucose to realize molecular-level contact of boron and carbon, the reaction activity is high, the reaction temperature is effectively reduced, the particle size of boron carbide is reduced, other materials are not used for doping, only carbon and boron exist in reactants, and the purity of boron carbide is high.

Description

Technical Field

[0001] The invention relates to the technical field of boron carbide production, and in particular to a method and a device for continuous production of high-purity ultrafine boron carbide. Background Art

[0002] Boron carbide (B4C) has physical and chemical properties such as low density, high hardness, strong wear resistance, high chemical stability, strong acid and alkali corrosion resistance, and excellent neutron absorption ability. It is widely used in abrasive tools, high-performance engineering ceramics, bulletproof materials, cutting tools, nuclear reactor control rods and shielding materials.

[0003] The application field of boron carbide is greatly affected by its purity and particle size. At present, the methods for preparing boron carbide powder at home and abroad mainly include carbon thermal reduction, laser induced chemical vapor deposition, sol-gel, precursor cracking, and self-propagating synthesis. At present, the most commonly used method for industrial production of boron carbide is still the electric arc furnace carbon thermal reduction method. This method uses anhydrous boron oxide or boric acid to provide a boron source, which reacts with a carbon source at high temperature for reduction. It is usually impossible to produce high-purity ultrafine boron carbide powder, and the cost is high, which causes great pollution to the environment.

[0004] The self-propagating synthesis method requires the addition of magnesium to the reactants to achieve a magnesium thermal reaction. The reaction is violent and prone to explosion. It is also easy to introduce impurities and is difficult to remove completely.

[0005] Laser-induced chemical vapor deposition is mainly used to prepare small amounts of boron carbide materials in the laboratory, and the cost is extremely high, making it unsuitable for industrial production.

[0006] In 2011, Zhang Yunfei from Dalian University of Technology used polyvinyl alcohol and boric acid as raw materials in his master's thesis and adopted the sol-gel method to synthesize polyvinyl alcohol borate gel as a precursor for preparing boron carbide. After pyrolysis, boron carbide was synthesized at a lower reaction temperature. However, in the process of replicating the reaction, the inventors found that the polyvinyl alcohol solution was extremely sensitive to boric acid. A white flocculent gel precipitate appeared immediately when it was added dropwise. The gel precipitate would hinder the mixing of the solution in the medium term. The boron carbide produced was larger and had a wider particle size distribution range. It had high requirements on the speed and stability of the operation, and it was difficult to expand to industrial production.

[0007] Therefore, it is a technical problem that those skilled in the art need to solve to find a low-cost, high-purity, ultrafine boron carbide continuous production method suitable for industrial production. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a method and device for continuous production of high-purity ultrafine boron carbide, aiming to provide a low-cost production method suitable for industrial production and realize continuous production of high-purity ultrafine boron carbide.

[0009] The technical solution adopted in this application to solve this technical problem is:

[0010] A method for continuously producing high-purity ultrafine boron carbide comprises the following steps:

[0011] Step S1: preparing materials;

[0012] Prepare boric acid solution, glucose solution and PVA solution and set aside;

[0013] Step S2: beating;

[0014] During the stirring process, glucose solution is added to the boric acid solution, and the mixture is stirred for 3-4 hours to obtain a mixed solution; PVA solution is added to the mixed solution, stirred and mixed, and then injected into the graphite mold;

[0015] Step S3: Dehydration, carbonization, and carbothermal reduction to generate boron carbide;

[0016] Step S4: purification of boron carbide.

[0017] Furthermore, during the pulping process in step S2, sodium hydroxide solution is added to the mixed solution to adjust the pH to 9-12.

[0018] Furthermore, in step S2, the molar ratio of boric acid to glucose in the mixed solution is 1:1.2-1.5; the added PVA solution is 15-50 g / L, and the mass of the added PVA solution accounts for 3% to 5% of the mass of the mixed solution.

[0019] Furthermore, in step S3, the dehydration temperature is 150-200°C; the carbonization temperature is 650-700°C; and the carbothermal reduction reaction temperature is 1250-1300°C.

[0020] Furthermore, in step S4, the boron carbide purification process is as follows: the obtained boron carbide is ground and then calcined in air at 600-800° C. for 2-3 hours.

[0021] Furthermore, in step S3, the dehydration, carbonization and carbon thermal reduction reactions are all completed in a tunnel furnace.

[0022] A high-purity ultrafine boron carbide continuous production device comprises a furnace body, a heating mechanism fixed on the furnace body, a conveyor mesh belt and a graphite boat, wherein a plurality of baffles are arranged in the furnace body, and the baffles divide the internal space of the furnace body into at least three mutually connected chambers, each of which is provided with a heating mechanism and a temperature sensor, an inert gas supply mechanism is arranged at the discharge end of the furnace body, and an adjustable exhaust mechanism is arranged between each two adjacent chambers, and the temperature difference between the two adjacent chambers is controlled by the exhaust mechanism, so that one furnace can be used for three purposes.

[0023] Furthermore, the heating mechanism is only connected to the third chamber along the conveying direction of the conveyor mesh belt.

[0024] Furthermore, the barrier member includes two adjacent baffles, the space between the two baffles is connected to the exhaust mechanism, and the barrier member exhausts air through the exhaust mechanism between the two baffles to control the temperature difference between its two adjacent chambers.

[0025] Furthermore, both baffles of the blocking member are provided with inner holes, and the inner holes allow the conveyor mesh belt and the graphite boat to pass through.

[0026] Furthermore, each of the exhaust mechanisms actively draws air from the furnace body, and the amount of air drawn is associated with the temperature in its adjacent chamber.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Compared with the prior art, the present invention utilizes the complex formed between boric acid and glucose to achieve molecular-level contact between boron and carbon, has high reaction activity, effectively reduces the reaction temperature, and reduces the particle size of boron carbide. In addition, because no other materials are used for doping, there are only carbon and boron in the reactants, and the boron carbide has high purity.

[0029] 2. The present invention uses the amorphous carbon after colloid carbonization and boron to react. The colloid is in a porous bracket state after carbonization, which is different from the arc furnace reaction, reduces the energy consumption of subsequent processing and avoids the introduction of excessive impurities in the subsequent processing process.

[0030] 3. The continuous production device of the present invention divides the temperature inside the furnace into three stages by a partition plate, which are used for different purposes respectively. One device can complete the entire carbon thermal reduction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process flow chart of the present invention;

[0032] Figure 2 It is a structural schematic diagram of the continuous production device of the present invention;

[0033] Figure 3 is a sectional front view of the continuous production device of the present invention;

[0034] Figure 4 It is a positional relationship diagram of the blocking member of the present invention, the conveyor mesh belt and the graphite boat.

[0035] The numbers in the attached drawings are: 1. furnace body; 2. heating mechanism; 3. conveyor mesh belt; 4. graphite boat; 5. blocking member; 6. drying chamber; 7. carbonization chamber; 8. carbon thermal reduction chamber; 9. cooling chamber; 10. inert gas supply mechanism; 11. exhaust mechanism; 12. inner hole. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0037] like Figure 1 As shown, Figure 1 The process flow of the present invention is shown. The present invention aims to utilize the characteristic that boric acid can be complexed with glucose. First, a small amount of glucose and boric acid are complexed, but the boric acid is not completely complexed. Then, PVA is added to graft the complex onto PVA. On the one hand, a heat-resistant stable complex is formed, and on the other hand, the complex is evenly dispersed. After carbonization, the boron and carbon molecules in contact fully react, but the grains are smaller, reducing the problem of grain growth. At the same time, the overall system does not introduce impurity factors, ensuring the high purity of boron carbide.

[0038] Embodiment 1:

[0039] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0040] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0041] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0042] Add 455 ml of boric acid solution and 545 ml of glucose solution into a beaker and age under stirring for 4 hours to form a mixed solution of boric acid, glucose and their complexes. Add 30 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 180 seconds, the mixed solution turns into a jelly-like substance, which gradually becomes stable over time.

[0043] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 23.15 g with a yield of 92.08%, an average particle size of 3-5 microns, and a purity of 99.34%.

[0044] Embodiment 2:

[0045] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0046] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0047] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0048] Add 500 ml of water, 250 ml of boric acid solution and 250 ml of glucose solution into a beaker and age under stirring for 4 hours to form a mixed solution of boric acid, glucose and their complexes. Add 50 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 210 seconds, the mixed solution turns into a jelly state, which easily loses its jelly state after heating.

[0049] The graphite boat was placed in a drying oven and dried at 200°C for 5 hours to obtain a white dry rubber block with a severely shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 12.43 g with a yield of 89.93%, an average particle size of 5-10 microns, and a purity of 98.62%.

[0050] Embodiment three:

[0051] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0052] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0053] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0054] Add 400 ml of boric acid solution and 600 ml of glucose solution into a beaker and age under stirring for 4 hours to form a mixed solution of boric acid, glucose and their complexes. Add 40 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 165 seconds, the mixed solution turns into a jelly-like substance, which gradually becomes stable over time.

[0055] The graphite boat was placed in a drying oven and dried at 180°C for 4 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 650°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 5 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 2.5 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 20.58 g, with a yield of 93.12%, an average particle size of 3-5 microns, and a purity of 99.19%.

[0056] Embodiment 4:

[0057] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0058] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0059] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0060] Add 435ml of boric acid solution and 565ml of glucose solution into a beaker, add sodium hydroxide while stirring to make the pH around 9-10, age for 4h to form a mixed solution of boric acid, glucose and their complexes, add 30g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer inside. After about 150 seconds, the mixed solution turns into a jelly state.

[0061] As time goes by, the jelly-like substance gradually becomes stable.

[0062] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 650°C for 2-3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 5 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 700°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 22.35 g with a yield of 93.01%, an average particle size of 3-5 microns, and a purity of 99.13%.

[0063] Embodiment five:

[0064] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0065] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0066] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0067] Add 167 ml of water, 347 ml of boric acid solution and 486 ml of glucose solution into a beaker and age under stirring for 2 hours to form a mixed solution of boric acid, glucose and their complexes. Add 50 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 75 seconds, the mixed solution turns into a jelly-like substance, which gradually becomes stable over time.

[0068] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 650°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 17.41 g with a yield of 90.82%, an average particle size of 3-8 microns, and a purity of 98.91%.

[0069] Embodiment six:

[0070] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0071] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0072] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0073] In a beaker, 167 ml of water, 347 ml of boric acid solution and 486 ml of glucose solution were aged for 4 hours under stirring to form a mixed solution of boric acid, glucose and their complexes. After adding 40 g of PVA solution, the solution was quickly transferred to a graphite boat, wherein a graphite cushion layer was provided in the graphite boat. After about 185 seconds, the mixed solution turned into a jelly-like substance, and the jelly-like substance gradually became stable with the extension of time.

[0074] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 650°C for 22 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Free carbon could be removed by calcining at 700°C for 2 hours in an air atmosphere. 17.01 g of boron carbide material was obtained with a yield of 88.73%, an average particle size of 3-5 microns, and a purity of 96.87%.

[0075] Embodiment seven:

[0076] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90℃ to dissolve the boric acid to make a 4mol / L boric acid solution for later use.

[0077] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0078] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0079] Add 455 ml of boric acid solution and 545 ml of glucose solution into a beaker, add sodium hydroxide while stirring to make the pH around 11-12, and age for 2 hours to form a mixed solution of boric acid, glucose and their complexes. Add 30 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 95 seconds, the mixed solution turns into a jelly-like substance, which gradually becomes stable over time.

[0080] The graphite boat was placed in a drying oven and dried at 150°C for 4 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 2 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 700°C for 2 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 22.95 g, with a yield of 91.29%, an average particle size of 3-5 microns, and a purity of 98.54%.

[0081] Comparative Example 1:

[0082] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0083] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0084] 455 ml of boric acid solution and 545 ml of glucose solution were added into a beaker and aged for 4 hours under stirring to form a mixed solution of boric acid, glucose and their complexes, which was then transferred into a graphite boat, wherein a graphite cushion layer was provided inside the graphite boat.

[0085] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry powder with a shrunk volume. The dry powder and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 3 hours. The carbonized material and the graphite boat were then placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 21.92 g, with a yield of 87.19%, an average particle size of 5-15 microns, and a purity of 96.59%.

[0086] Comparative Example 2:

[0087] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0088] Take 100g PVA1799 and add water to make up to 1L, heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0089] Add 455 ml of boric acid solution and 545 ml of PVA solution into a beaker, and the mixed solution immediately turns into a jelly after stirring. The mixed solution is quickly transferred into a graphite boat and allowed to stand for 2 hours. A graphite cushion layer is provided in the graphite boat.

[0090] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 23.03 g, with a yield of 91.61%, an average particle size of 3-10 microns, and a purity of 98.86%.

[0091] Comparative Example 3:

[0092] Take 247.2g of boric acid and add water to make up to 1L. Heat the water bath to 90°C to dissolve the boric acid to prepare a 4mol / L boric acid solution for later use.

[0093] Take 720.6g of glucose and add water to make the volume to 1L, making it 4mol / L, and set aside.

[0094] Take 15g PVA1799 and add water to make up to 1L. Heat the water bath to 95℃ to make a 15g / L PVA solution for later use.

[0095] Add 333 ml of boric acid solution and 667 ml of glucose solution into a beaker and age under stirring for 4 hours to form a mixed solution of boric acid, glucose and their complexes. Add 50 g of PVA solution and quickly transfer to a graphite boat with a graphite cushion layer. After about 10 minutes, the mixed solution turns into a jelly state and is unstable. It is easy to liquefy and flow when heated.

[0096] The graphite boat was placed in a drying oven and dried at 150°C for 5 hours to obtain a white dry rubber block with a shrunk volume. The dry rubber block and the graphite boat were placed in a muffle furnace and carbonized at 700°C for 3 hours to obtain a black block. The block and the graphite boat were placed in an atmosphere furnace and reacted at 1250-1300°C for 3 hours to obtain a boron carbide material. The material was mixed with carbon. Sintering at 800°C for 3 hours in an air atmosphere could significantly remove free carbon. The obtained boron carbide material was 16.39 g with a yield of 89.08%, an average particle size of 5-10 microns, and a purity of 97.10%.

[0097] like Figure 2 and Figure 3 As shown, a high-purity ultrafine boron carbide continuous production device comprises a furnace body 1, a heating mechanism 2 fixed on the furnace body 1, a conveyor mesh belt 3 and a graphite boat 4 rotating in the furnace body, wherein the furnace body 1, the heating mechanism 2 and the conveyor mesh belt 3 constitute a tunnel furnace, the left end of the furnace body 1 is a feeding end, and the right end is a discharging end, and a plurality of blocking members 5 are arranged in the furnace body 1, such as Figure 3 As shown in the figure, the barrier 5 divides the internal space of the furnace body 1 into four chambers, which are the drying chamber 6 ( Figure 3 The first chamber from the left), carbonization chamber 7 ( Figure 3 The second chamber from the left), carbon thermal reduction chamber 8 ( Figure 3 The third chamber from the left) and cooling chamber 9 ( Figure 3 The fourth chamber from the left), each of which is provided with a heating mechanism 2 and a temperature sensor (not shown in the figure), for heating the chamber and measuring the temperature in each chamber, an inert gas supply mechanism 10 is provided at the discharge end of 1, for supplying inert gas into the furnace body 1 to achieve an inert atmosphere in the furnace body 1, argon gas in this embodiment to avoid the production of boron nitride, an adjustable exhaust mechanism 11 is provided between each two adjacent chambers, the temperature difference between the two adjacent chambers is controlled by the exhaust mechanism 11, so as to achieve three uses of one furnace, achieve staged heating, and reduce energy consumption.

[0098] By adjusting the length ratio of the drying chamber 6, the carbonization chamber 7, the carbon thermal reduction chamber 8 and the cooling chamber 9 and the running speed of the conveyor mesh belt 3, the change of the heating time in each stage can be achieved. For example, in a 15-meter tunnel furnace, the drying chamber 6, the carbonization chamber 7, the carbon thermal reduction chamber 8 and the cooling chamber 9 are 6 meters, 3 meters, 4 meters and 2 meters respectively, and the running speed of the conveyor mesh belt 3 is 20 mm / min, so that the material can be dried for 5 hours in the drying chamber 6, cracked for 2.5 hours in the carbonization chamber 7, reacted for 3.3 hours in the carbon thermal reduction chamber 8, and cooled for 1.7 hours in the cooling chamber 9, which fully meets the process parameters required by the present invention.

[0099] In the furnace body, no matter in the drying stage, carbonization stage or carbon thermal reduction stage, gas is discharged and discharged outward from the furnace body 1, and the exhaust temperature increases from left to right. Exhausting to the left can heat up the adjacent chamber on the left, achieve energy saving and emission reduction, and make full use of the energy of the heating mechanism. Therefore, the heating mechanism can also be connected only in the carbon thermal reduction chamber.

[0100] like Figure 3 As shown, the blocking member 5 includes two adjacent baffles, and a blocking space is formed between the two baffles. The blocking space is connected to the exhaust mechanism, and the blocking space is connected to the exhaust mechanism 11 for exhausting air to control the temperature difference between the two adjacent chambers.

[0101] like Figure 4 Both baffles of the blocking member 5 are provided with inner holes 12 , and the inner holes 12 allow the conveyor mesh belt 3 and the graphite boat 4 to pass through.

[0102] Each of the exhaust mechanisms 11 actively draws air from the furnace, and the amount of air drawn is related to the temperature in the adjacent chamber.

[0103] The present invention realizes the partitioning of the furnace body 1 by setting a baffle 5, and then uses the internal space of the baffle 5 for exhaust to control the hot air transfer between two adjacent chambers, so that it can satisfy the requirement that the hot air is discharged to the left to heat the adjacent chamber, and has sufficient control means to achieve temperature stability in the partitioned area. Based on the carbon thermal reduction reaction and drying, the exhaust mechanism is used to achieve temperature stability of carbonization. One furnace has three uses, and continuous production of boron carbide is realized.

[0104] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

Claims

1. A method for continuous production of high-purity ultrafine boron carbide, characterized in that: The following steps are involved: Step S1: preparing materials; Prepare boric acid solution, glucose solution and PVA solution and set aside; Step S2: beating; During the stirring process, add the glucose solution to the boric acid solution, and stir and mix for 3-4 hours to obtain a mixed solution; Add PVA solution to the mixed solution, stir and mix, and then inject into the graphite mold; Step S3: Dehydration, carbonization, and carbothermal reduction to generate boron carbide; Step S4: purification of boron carbide.

2. The method for continuous production of high-purity ultrafine boron carbide according to claim 1, characterized in that: During the pulping process in step S2, sodium hydroxide is also added to the mixed solution to adjust the pH to 9-12.

3. The method for continuous production of high-purity ultrafine boron carbide according to claim 1, characterized in that: In step S2, the molar ratio of boric acid to glucose in the mixed solution is 1:1.2-1.5; the added PVA solution is 15-50 g / L, and the mass of the PVA solution accounts for 3% to 5% of the mass of the mixed solution.

4. The method for continuous production of high-purity ultrafine boron carbide according to claim 1, characterized in that: In step S3, the dehydration temperature is 150-200°C; the carbonization temperature is 650-700°C; and the carbothermal reduction reaction temperature is 1250-1300°C.

5. The method for continuous production of high-purity ultrafine boron carbide according to claim 1, characterized in that: In step S4, the boron carbide purification process is as follows: the obtained boron carbide is ground and then calcined in air at 600-800° C. for 2-3 hours.

6. The method for continuous production of high-purity ultrafine boron carbide according to claim 1, characterized in that: In step S3, the dehydration, carbonization and carbon thermal reduction reactions are all completed in a tunnel furnace.

7. A continuous production device for high-purity ultrafine boron carbide, comprising a furnace body (1), a heating mechanism (2) fixed to the furnace body (1), a conveyor mesh belt (3) and a graphite boat (4), characterized in that: A plurality of baffles (5) are provided in the furnace body (1), and the baffles (5) divide the internal space of the furnace body (1) into at least three interconnected chambers, each of which is provided with a heating mechanism (2) and a temperature sensor, an inert gas supply mechanism (10) is provided at the discharge end of the furnace body (1), and an adjustable exhaust mechanism (11) is provided between each two adjacent chambers.

8. The continuous production device for high-purity ultrafine boron carbide according to claim 7, characterized in that: The barrier member (5) comprises two adjacent baffles, the space between the two baffles is connected to the exhaust mechanism (11), and the barrier member (5) exhausts air through the exhaust mechanism (11) between the two baffles, thereby controlling the temperature difference between two adjacent chambers.

9. The continuous production device for high-purity ultrafine boron carbide according to claim 8, characterized in that: Both baffles of the blocking member (5) are provided with inner holes (12), and the inner holes (12) allow the conveyor mesh belt and the graphite boat (4) to pass through.

10. The continuous production device for high-purity ultrafine boron carbide according to claim 7, characterized in that: The heating mechanism (2) is only connected to the third chamber along the conveying direction of the conveyor mesh belt (3).

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