Pulping method and device for boron carbide production

Abstract

The invention relates to the technical field of boron carbide production, in particular to a pulping method and device for boron carbide production, and the pulping method for boron carbide production comprises the following steps: S1, preparing materials; respectively preparing a saturated solution of boric acid, a glucose solution and a PVA (Polyvinyl Alcohol) solution by using three stirring tanks for later use; step S2, mixing; jointly adding a saturated solution of boric acid and a glucose solution into a mixing tank, and stirring and mixing for 3-4 hours to obtain a mixed solution; and S3, gelatinizing: adding a PVA (Polyvinyl Alcohol) solution into the mixed solution, stirring and mixing, injecting into a graphite mold, and waiting for 1-2 minutes to form a gel state. According to the method, boric acid and glucose are complexed, high-energy-consumption ball milling is omitted, molecular-level contact better than the ball milling effect is achieved, the synthesis temperature can be reduced, and the product purity can be improved.

Description

Technical Field

[0001] The invention relates to the technical field of boron carbide production, and in particular to a pulping method and a device for boron carbide production. 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 and other fields.

[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] During the research and development process of boron carbide production, the inventors found that when boric acid and amorphous carbon achieve molecular-level contact, their synthesis temperature can be greatly reduced and the product purity can be improved. Therefore, it is necessary to adjust the contact between boric acid and carbon to achieve molecular-level contact.

[0005] After searching, Chen Guanting, Li Sanxi, Wang Song, and Li Yang recorded in "Research Progress of Preparation of Boron Carbide Powder by Precursor Conversion Method" that boron carbide powder was prepared by reacting compounds containing hydroxyl functional groups with boric acid. Compared with the traditional carbothermal reduction method, the precursor method makes carbon and boron oxide mix at the molecular level through reaction, which makes the contact closer and changes the kinetic process of the reaction. Therefore, the reaction can occur at a lower temperature, and a smaller boron carbide powder with a higher degree of reaction can be synthesized.

[0006] In order to achieve smaller boron carbide particles, the precursor needs to be gelled, but PVA is extremely sensitive to boric acid. Once boric acid is added, it will immediately gel. Although the gelled material can be easily handled in the experimental stage, considering the actual production, once gelation occurs inside the tank, it will be difficult to achieve good material transfer.

[0007] Moreover, both boric acid and PVA are difficult to dissolve, especially when approaching their solubility upper limits. After the agitator is fed, the materials are deposited downward at the discharge port to form a piled state. This part of the piled material is the most difficult to dissolve. Without sufficient dissolution, large-particle products are easily produced during production, which also affects the product yield. Therefore, the present invention aims to provide a pulping method and device for boron carbide production, which fully treats the raw materials for boron carbide production so that it can achieve molecular-level contact and ensure stable production. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a pulping method and device for boron carbide production. The raw materials for boron carbide production are fully processed so that they can achieve molecular-level contact and ensure stable production.

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

[0010] A pulping method for producing boron carbide, comprising the following steps:

[0011] Step S1: preparing materials;

[0012] Use three stirring tanks to prepare saturated boric acid solution, glucose solution and PVA solution respectively for later use;

[0013] Step S2: mixing;

[0014] Add the saturated boric acid solution and the glucose solution into a mixing tank and stir and mix them for 3-4 hours to obtain a mixed solution;

[0015] Step S3: Gelation

[0016] Add PVA solution to the mixed solution, stir and mix, then inject into the graphite mold and wait for 1-2 minutes to form a gel state.

[0017] Furthermore, in the mixed solution, the molar ratio of boric acid to glucose is 1:1.2-1.5.

[0018] Furthermore, in step S3, the PVA solution is 15 g / L, and the mass of the PVA solution accounts for 3% to 5% of the mass of the mixed solution.

[0019] Furthermore, the saturated boric acid solution, glucose solution and PVA solution are all at 90-95°C.

[0020] A pulping device for boron carbide production comprises at least a boric acid dissolving mechanism, a glucose dissolving mechanism, a PVA dissolving mechanism and a mixing mechanism, wherein the boric acid dissolving mechanism, the glucose dissolving mechanism, the PVA dissolving mechanism and the mixing mechanism all have elements capable of heating internal materials, the discharge element of the boric acid dissolving mechanism and the discharge element of the glucose dissolving mechanism are connected to the feed end of the mixing mechanism, and the discharge element of the mixing mechanism and the discharge element of the PVA dissolving mechanism are connected to a static mixer together.

[0021] Furthermore, the boric acid dissolving mechanism, the glucose dissolving mechanism and the PVA dissolving mechanism are all stirring tanks, and the upper end of the discharge element of the stirring tank is located inside the stirring tank with the opening facing downward.

[0022] Furthermore, the discharging mechanism is a discharging pipe, and the upper end of the discharging pipe extends into the mixing tank and bends downward.

[0023] Furthermore, the length of the bent portion of the discharge pipe is 3-5 times the inner diameter of the discharge pipe.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention eliminates high-energy-consuming ball milling by complexing boric acid with glucose, achieves better molecular-level contact than ball milling, can reduce synthesis temperature, and improve product purity.

[0026] The present invention can prevent undissolved materials from entering the mixing tank by adjusting the equipment, thereby meeting the process requirements and reducing the equipment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a layout diagram of a pulping device for producing boron carbide according to the present invention;

[0028] Figure 2 is a cross-sectional view of a stirring tank in Embodiment 2 of the present invention;

[0029] Figure 3 It is a cross-sectional view of the stirring tank in the third embodiment of the present invention.

[0030] The numbers in the attached drawings are: 1, boric acid stirring tank; 2, glucose stirring tank; 3, PVA stirring tank; 4, mixing tank; 5, static mixer; 6, protective cover; 1a, 2a, 3a, 4a are all discharge pipes. DETAILED DESCRIPTION

[0031] 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.

[0032] A pulping method for producing boron carbide, comprising the following steps:

[0033] Step S1: preparing materials;

[0034] Three stirring tanks were used to prepare saturated boric acid solution (250 g / L), glucose solution (750 g / L) and PVA solution (15 g / L) at 90-95° C. for later use;

[0035] Step S2: mixing;

[0036] Add the saturated boric acid solution and the glucose solution into a mixing tank and stir and mix for 3-4 hours to obtain a mixed solution, wherein the molar ratio of boric acid to glucose in the mixed solution is 1:1.2-1.5;

[0037] Step S3: Gelation

[0038] Add 3% to 5% PVA solution by mass of the mixed solution to the mixed solution, stir and mix, then inject into the graphite mold and wait for 1 to 2 minutes to form a gel state.

[0039] Embodiment 1:

[0040] like Figure 1 As shown, a beating device for boron carbide production includes at least two stirring and mixing units, each stirring and mixing unit includes a boric acid stirring tank 1, a glucose stirring tank 2, a PVA stirring tank 3 and a mixing tank 4, the boric acid stirring tank 1, the glucose stirring tank 2, the PVA stirring tank 3 and the mixing tank 4 are tank bodies with jackets and stirring paddles, wherein the lower ends of the boric acid stirring tank 1 and the glucose stirring tank 2 are connected to the mixing tank 4 via a discharge pipe 1a and a discharge pipe 2a respectively, and the lower ends of the PVA stirring tank 3 and the mixing tank 4 are connected to a static mixer 5 via a discharge pipe 3a and a discharge pipe 4a respectively, the static mixer 5 has a main inlet, a main outlet and a side inlet, and the side inlet is connected to the lower end of the discharge pipe of the PVA stirring tank 3.

[0041] Embodiment 1 of the present invention mainly solves the problem that gel-like materials are difficult to transfer. Boric acid and glucose are first mixed to produce a complexation, but the complexation is not complete because insufficient glucose is used to complex the boric acid, which not only reduces the waste of glucose but also reduces the sensitivity of PVA to boric acid. After adding PVA, the solution is still liquid for a short time and can be mixed by a static mixer and injected into a graphite boat calmly, thereby reserving sufficient construction time for the production process, instead of the mixed solution forming a gel immediately after adding PVA, which leads to the problem that the gel material is difficult to transfer.

[0042] Embodiment 2:

[0043] Embodiment 1 Although the gel material is transferred in a fluid state to ensure the smooth progress of the process, the solubility of boric acid in water is low and it cannot be dissolved quickly after adding the material. The undissolved part is extremely easy to fall to the bottom of the boric acid stirring tank 1 and form an accumulation state at the upper end of the discharge pipe. Once the accumulation state is formed, the boric acid will be more difficult to dissolve. This leads to a large amount of boric acid and particles in the first discharge, which are easy to volatilize in the subsequent reaction, resulting in too low yield. In the subsequent discharge, the boric acid concentration is insufficient, which not only affects the product quality but also easily fluctuates due to the boric acid concentration and is inconsistent with the glucose complex state, thereby affecting the sensitive state of PVA. The time for PVA to form gel is different each time the material is discharged, which is easy to affect production and may even require frequent shutdowns for maintenance of the static mixer, which is intolerable in normal production.

[0044] The key to solving this type of problem is to keep the boric acid in the boric acid stirring tank 1 so that it can be stirred, that is, to prevent the boric acid from falling into the discharge pipe before dissolving, that is, the discharge mechanism of each stirring tank is located inside the stirring tank and the opening faces downward.

[0045] Therefore, the inventor changed the structure of the discharge pipe, such as Figure 2 As shown, the discharge pipe extends upward into the interior of the stirring tank to form a tubular body protruding from the inner wall of the tank body. The outer cover of the discharge pipe is provided with a protective cover 6. The lower end opening of the protective cover 6 is lower than the upper end of the discharge pipe, so that the opening of the discharge mechanism is downward. In this way, after the boric acid is added, it can only fall on the protective cover 6 and the inside of the tank body, and will not directly enter the discharge pipe to accumulate. The boric acid can always be contacted by the flow of the liquid inside the stirring tank, so that it can be dissolved, thereby ensuring the quality stability of the solution in the whole tank and ensuring the quality of the product.

[0046] Embodiment 2:

[0047] The present invention also has another structure, such as Figure 3 As shown, the discharge pipe extends upward into the interior of the mixing tank to form a tubular body protruding from the inner wall of the tank, and the protruding portion is bent downward so that the upper end of the discharge pipe opens downward.

[0048] The length of the bent portion of the discharge pipe is 3-5 times the inner diameter of the discharge pipe to prevent the solution flowing inside the stirring tank from throwing undissolved boric acid into the main body of the discharge pipe.

[0049] The advantages of this arrangement are that the structure is simpler, the equipment cost is lower, and the bent portion can also interfere with the flow of the fluid, causing it to flow disorderly, thereby promoting the mixing of the fluid with the undissolved boric acid and accelerating the dissolution of the boric acid.

[0050] 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 pulping method for producing boron carbide, characterized in that: The following steps are involved: Step S1: preparing materials; Use three stirring tanks to prepare saturated boric acid solution, glucose solution and PVA solution respectively for later use; Step S2: mixing; Add the saturated boric acid solution and the glucose solution into a mixing tank and stir and mix them for 3-4 hours to obtain a mixed solution; Step S3: Gelation Add PVA solution to the mixed solution, stir and mix, then inject into the graphite mold and wait for 1-2 minutes to form a gel state.

2. The pulping method for producing boron carbide according to claim 1, characterized in that: In the mixed solution, the molar ratio of boric acid to glucose is 1:1.2-1.

5.

3. The pulping method for producing boron carbide according to claim 1, characterized in that: In step S3, the PVA solution is 15 g / L, and the mass of the PVA solution accounts for 3% to 5% of the mass of the mixed solution.

4. The pulping method for producing boron carbide according to claim 1, characterized in that: The saturated boric acid solution, glucose solution and PVA solution are all at 90-95°C.

5. A pulping device for boron carbide production, characterized in that: It at least includes a boric acid dissolving mechanism, a glucose dissolving mechanism, a PVA dissolving mechanism and a mixing mechanism, wherein the boric acid dissolving mechanism, the glucose dissolving mechanism, the PVA dissolving mechanism and the mixing mechanism all have elements that can heat the internal materials, the discharge element of the boric acid dissolving mechanism and the discharge element of the glucose dissolving mechanism are connected to the feed end of the mixing mechanism, and the discharge element of the mixing mechanism and the discharge element of the PVA dissolving mechanism are commonly connected to a static mixer.

6. The beating device for boron carbide production according to claim 5, characterized in that: The boric acid dissolving mechanism, the glucose dissolving mechanism and the PVA dissolving mechanism are all stirring tanks, and the upper end of the discharge element of the stirring tank is located inside the stirring tank, and the opening faces downward.

7. The beating device for boron carbide production according to claim 6, characterized in that: The discharging mechanism is a discharging pipe, the upper end of which extends into the mixing tank and bends downward.

8. The beating device for producing boron carbide according to claim 5, characterized in that: The length of the bent portion of the discharge pipe is 3-5 times the inner diameter of the discharge pipe.

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