Preparation method of flow guide pipe for hydrogenation powder preparation

Abstract

The invention relates to the field of metal gas atomization pulverization, and discloses a preparation method of a flow guide pipe for hydrogenation pulverization. Comprising the following steps: S1, preparing a dispersion solution from zirconium oxychloride, magnesium chloride, a dispersing agent and water; s2, mixing the dispersion solution with ammonia water to obtain a mixed solution; s3, the mixed solution is atomized, liquid drops obtained through atomization are heated and dried, the heating temperature is lower than 500 DEG C, and mixed powder is obtained; s4, heating the mixed powder to 500-700 DEG C to obtain powder blocks, and dispersing the powder blocks into powder; s5, performing hot-pressing sintering on the powder to obtain a composite ceramic rod; and S6, the composite ceramic rod is machined into the flow guide pipe. The appropriate flow guide pipe is provided for the process for preparing magnesium hydride powder through magnesium metal and magnesium alloy hydrogenation, and the problems that during magnesium-based metal hydrogenation powder preparation, an existing flow guide pipe is not matched and reacts with magnesium or hydrogen, the service life is too short, raw materials are polluted, and the production efficiency is low are solved.

Description

Technical Field

[0001] The present invention relates to the field of metal gas atomization powder making, and particularly relates to a preparation method of a diversion tube for hydrogenation powder making. Background Art

[0002] Magnesium-based hydrogen storage materials are considered to be one of the most promising metal hydrogen storage materials due to their large hydrogen storage capacity, rich resources, and low cost. Magnesium-based hydrogen storage materials can release and absorb hydrogen under certain conditions and can be applied in the fields of new energy, medicine, agriculture, etc. As a reversible "storage" medium for hydrogen, it has excellent hydrogen absorption and desorption performance, and has the advantages of no kinetic decay and capacity loss during long-term cycling, and can achieve large-capacity solid-state hydrogen storage and long-distance transportation at normal temperature and pressure. It can not only reduce the storage and transportation costs and energy consumption of hydrogen, but also be safe and convenient, and is expected to become an important key material in the field of hydrogen storage and transportation, thus promoting the development of the hydrogen energy industry.

[0003] There are currently various preparation methods for magnesium hydride, among which the direct reaction method is particularly prominent. This method directly reacts magnesium-based powder with hydrogen by pressurization and heating to produce high-purity magnesium hydride and can be recycled. It is regarded as the most promising preparation process in the field of hydrogen storage materials. However, due to the high reactivity of magnesium-based powder, it faces insufficient safety and is prone to explosion risk when directly prepared into powder, and the production efficiency is low. In addition, the subsequent hydrogenation process of metal powder takes a long time and the production capacity is limited. These factors significantly hinder the progress of hydrogen storage material technology.

[0004] Based on this, the inventor has studied a safer and more efficient magnesium hydride preparation technology: melting magnesium into a liquid state and then spraying it out under the action of high-pressure gas through a diversion tube to form fine droplets, and the magnesium droplets solidify during the rapid cooling process to obtain magnesium hydride powder with a certain hydrogen content, effectively improving the production efficiency and reducing the risk of deflagration during production.

[0005] As a key component in the magnesium-based metal hydrogenation powder making, the performance of the diversion tube is crucial. The inner side bears the continuous scouring of the molten metal, and it is necessary to ensure that the inner diameter hardly changes during the scouring process; the outer bottom needs to withstand the long-term impact of high-pressure gas of 3-8 MPa to prevent rupture to ensure the continuity of the powder making process. Therefore, there are strict standards for the service life of the diversion tube. However, in the actual production process, it is found that the current diversion tubes mainly use alumina ceramics, boron nitride ceramics, and composite boron nitride ceramic materials, and their service lives are usually limited to one furnace, with a duration of about 3 to 20 minutes. Especially for the magnesium metal hydrogenation powder making process, due to the reaction of alumina and boron nitride with magnesium or hydrogen, these materials are no longer suitable. In view of this situation, there is an urgent need to develop a new diversion tube preparation technology to prepare a diversion tube that meets the specific requirements of hydrogenation powder making. Summary of the Invention

[0006] The present invention aims to provide a preparation method for a flow guide tube used in hydrogenation powder making, so as to solve the problems that the existing flow guide tubes are not adaptable, react with magnesium or hydrogen, and have too short service life during the hydrogenation powder making of magnesium-based metals, resulting in pollution of raw materials and low production efficiency.

[0007] To achieve the above object, the present invention adopts the following technical scheme: A preparation method for a flow guide tube used in hydrogenation powder making, comprising the following steps:

[0008] S1, preparing a dispersion solution by using zirconium oxychloride, magnesium chloride, a dispersant and water;

[0009] S2, mixing the dispersion solution with ammonia water to obtain a mixed solution;

[0010] S3, atomizing the mixed solution and heating the atomized droplets for drying, with the heating temperature being lower than 500 °C, to obtain a mixed powder;

[0011] S4, heating the mixed powder to 500 - 700 °C to obtain a powder block, and dispersing the powder block into powder;

[0012] S5, hot-pressing and sintering the powder into a composite ceramic rod;

[0013] S6, machining the composite ceramic rod into a flow guide tube.

[0014] The beneficial effects of this solution are as follows:

[0015] 1. The flow guide tube prepared by this solution can withstand the continuous erosion of molten metal above 900 °C and a mixed gas of high-pressure hydrogen and argon below 8 MPa and 400 °C for up to 8 hours. During this process, the flow guide tube does not react with magnesium and hydrogen, the inner diameter change is less than 2%, and it does not break. Thus, it enables the realization of a more efficient and safer batch production method for preparing magnesium hydride powder using magnesium-based molten metal, effectively reducing the preparation difficulty and cost of magnesium hydride.

[0016] 2. In the flow guide tube prepared by this solution, magnesium oxide can act as a stabilizer, significantly enhancing the overall structural stability, making the mechanical strength, thermal shock resistance and chemical stability of the flow guide tube stronger. The phase stability effectively avoids the volume expansion and contraction of the flow guide tube caused by temperature changes, thereby improving the durability of the material. Moreover, the distribution of magnesium oxide particles at the zirconia grain boundaries, like "anchor points", enhances the overall strength and toughness of the material under the action of the grain boundary strengthening effect. At the same time, it also has excellent chemical inertness, enabling it to remain stable in extreme environments.

[0017] Secondly, the diversion tube of this solution has excellent thermal stability and will not be damaged when high-temperature molten magnesium and high-pressure gas pass through the diversion tube. At the same time, the diversion tube in the present invention also has excellent toughness: by incorporating magnesium oxide into the zirconia matrix, a phase change occurs in the material, thereby enhancing the ability of zirconia ceramics to resist crack propagation and deformation. Therefore, during the processing, a composite ceramic rod can be prepared by pressing and sintering first, and then the composite ceramic rod can be processed into a diversion tube by machining methods such as milling, turning, and grinding. Compared with directly pressing and sintering to obtain a diversion tube, the diversion tube with a more complex structure and smoother surface can be obtained by machining in this solution. At the same time, the shape and size of the diversion tube will no longer change after machining, resulting in higher machining accuracy, improving the qualification rate of the preparation of the diversion tube, and ensuring that the prepared diversion tube meets the needs of magnesium hydride powder preparation.

[0018] 3. In this solution, zirconium oxychloride and magnesium chloride are first dissolved in a solution so that the zirconium ions and magnesium ions can be fully fused with each other. After the dispersion solution is mixed with ammonia water, a reaction occurs to generate ZrO(OH) 2 and Mg(OH) 2 . After drying, a mixed powder including ZrO(OH) 2 and Mg(OH) 2 is obtained. When the mixed powder is heated in step 4, the solid ammonium chloride in the mixed powder completely decomposes, so that pure zirconia and magnesia can be obtained. Compared with the method of physically mixing zirconia and magnesia powders directly, in the mixed powder obtained in step 3 of the present invention, the components of zirconia and magnesia are more evenly mixed, so the structure of the prepared diversion tube is more stable.

[0019] Furthermore, the concentration of zirconium ions in the dispersion solution described in step 1 is 0.1 - 0.5 mol / L, and the concentration of magnesium ions is 0.02 - 0.2 mol / L.

[0020] The beneficial effects of this solution are as follows: the raw material component ratio in this solution significantly enhances the overall structural stability of the finished product, making the mechanical strength, thermal shock resistance, and chemical stability of the diversion tube stronger. The phase stability effectively avoids the volume expansion and contraction of the diversion tube caused by temperature changes, thereby improving the durability of the material.

[0021] Furthermore, when preparing the dispersion solution, the solution is heated to 40 - 80 °C.

[0022] The beneficial effects of this solution are as follows: heating the dispersion solution can increase the ion solubility, make the zirconium ions and magnesium ions fully dissolve, and thus ensure that the zirconia and magnesia in the prepared diversion tube are more evenly mixed.

[0023] Further, in the mixed solution described in Step 2, the volume fraction of the dispersion solution is 10 - 20 parts, and the volume fraction of ammonia water is 80 - 90 parts.

[0024] The beneficial effect of this solution is that the ratio of the dispersion solution to ammonia water can ensure a full reaction, and the prepared ZrO(OH) 2 and Mg(OH) 2 powders have accurate and uniform compositions.

[0025] Further, in Step 3, high-temperature gas is used to dry the droplets, and the high-temperature gas uses air or inert gas.

[0026] The beneficial effect of this solution is that the high-temperature gas can ensure instant drying of the droplets, avoiding the adhesion of droplets to the inner wall of the equipment and causing waste of raw materials.

[0027] Further, in Step 3, a centrifugal spray dryer is used to atomize the dispersion solution, and the rotational speed of the centrifugal atomizer of the centrifugal spray dryer is 12000 - 18000 rpm / min.

[0028] The beneficial effect of this solution is that by controlling the rotational speed of the centrifugal atomizer, the powder particle size is controlled: avoiding the formation of dust and explosion due to too fine particle size, and the finer the powder, the greater the stress, which is not conducive to hot pressing; at the same time, avoiding too coarse powder which is not conducive to later sintering.

[0029] Further, in Step 4, in the atmospheric environment, the temperature is raised to the heating decomposition temperature of 500 - 700 °C at a heating rate of 10 - 20 °C / min, and held for 1 - 3 h. After the holding is completed, it is naturally cooled to room temperature.

[0030] The beneficial effect of this solution is that pure zirconia and magnesia are prepared by heating decomposition. The principle is: under the condition of heating, ZrO(OH)2 → ZrO2 + H2O, Mg(OH)2 → MgO + H2O. The design of this process enables the complete volatilization of the residual solid ammonium chloride, ensuring the purity of the powder.

[0031] Further, in Step 5, the sintering temperature during hot press sintering is 1600 - 1800 °C.

[0032] The beneficial effect of this solution is to improve the density of the ceramic. Densification can significantly improve the compressive strength, flexural strength and fracture toughness of the ceramic, making it show better mechanical properties in various applications.

[0033] Further, before sintering, it is first heated to 600 - 800 °C for pre-sintering and held for 0.5 - 1 h, and then heated to the sintering temperature for sintering; after reaching the sintering temperature, pressure is applied to the solid raw materials, the pressure is 100 - 150 tons, and after holding the pressure for 1 - 3 h, it is cooled with the furnace to obtain a composite ceramic rod.

[0034] The beneficial effects of this solution are as follows: During hot-press sintering, pressure is applied while heating, and the powder is in a thermoplastic state, which helps the processes of contact diffusion and mass transfer by flow of particles, thus promoting sintering densification. Due to the synergistic effect of pressure and heat, hot-press sintering can reduce the sintering temperature, shorten the sintering time, and effectively resist grain growth, obtaining products with fine grains, high density, and good mechanical properties.

[0035] Further, during the entire heating process in Step 5, the heating rate is controlled at 10 - 20 °C / min.

[0036] The beneficial effects of this solution are as follows: If the heating rate is too fast, the temperature gradient and stress inside the ceramic will be too large, and the ceramic body will be difficult to withstand the internal pressure and crack. If the heating rate is too slow, the grain growth rate will slow down, but the grain sizes will be uneven and abnormal grain growth will occur, affecting the mechanical properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a flowchart of the preparation method of the diversion tube for hydrogenation powder making of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] The following is a further detailed description through specific embodiments:

[0039] Embodiment

[0040] A preparation method of a diversion tube for hydrogenation powder making, in combination with Figure 1 as shown, includes the following steps:

[0041] S1. Mix the dispersant with deionized water, then add zirconium oxychloride and magnesium chloride to the solution and stir to prepare a dispersion solution until the zirconium ion concentration in the dispersion solution is 0.1 - 0.5 mol / L and the magnesium ion concentration is 0.02 - 0.2 mol / L; and heat the dispersion solution to 40 - 80 °C; the dispersant is an organic solvent with a boiling point lower than 80 °C. Specifically, the dispersant is an alcohol. In this embodiment, the dispersant uses absolute ethanol, and the volume of absolute ethanol is 8% - 12% of the volume of the dispersion solution;

[0042] S2. Preheat the raw material tank of the centrifugal spray dryer to 40 - 80°C, add the dispersion solution to the raw material tank of the centrifugal spray dryer and stir; add ammonia water to the auxiliary material tank of the centrifugal spray dryer, mix the dispersion solution and ammonia water, and the volume fractions of the dispersion solution and ammonia water are 10 - 20 parts and 80 - 90 parts respectively to obtain a mixed solution. During this process, keep the temperature of the raw material tank at 40 - 80°C; in actual implementation, stir the dispersion solution before entering the centrifugal atomizer during atomization, and repeat step 1 again, adding the newly prepared dispersion solution and ammonia water to the raw material tank and the auxiliary material tank respectively; specifically, the concentration of ammonia water is 25%.

[0043] S3. Use the centrifugal spray dryer to atomize the dispersion solution. When atomizing, the centrifugal spray dryer sprays out the mixed solution at a speed of 12000 - 18000 rpm / min to form fine droplets of the mixed solution, and use drying air or inert gas with a temperature of 150 - 300°C to dry the droplets generated by atomization to obtain mixed powder.

[0044] S4. Spread the mixed powder, and use a muffle furnace in the atmospheric environment to heat it evenly at a heating rate of 10 - 20°C / min to 500 - 700°C and keep it warm for 1 - 3 h for decomposition. After the heat preservation ends, cool it naturally to room temperature to obtain a powder block; carry out ball milling and pulverization on the powder block to disperse it into powder.

[0045] S5. Hot press and sinter the powder obtained in step 4 into a composite ceramic rod. The sintering temperature is 1600 - 1800°C. Before sintering, first heat it to 600 - 800°C for pre-sintering and keep it warm for 0.5 - 1 h, then heat it to the sintering temperature for sintering. Control the heating rate at 10 - 20°C / min during the whole heating process and control the temperature to rise evenly; apply pressure to the powder after reaching the sintering temperature, the pressure is 100 - 150 tons, keep it warm and under pressure for 1 - 3 h and then cool it with the furnace to obtain a composite ceramic rod.

[0046] S6. Machine process the composite ceramic rod into a diversion tube.

[0047] The present invention discloses Example 1 and Example 2. Both Example 1 and Example 2 adopt the above preparation steps, and in step 4, heat it evenly at a speed of 10°C / min to 500°C and keep it warm for 1 h; the specific parameters of the rest are shown in the following table:

[0048]

[0049]

[0050] The present invention prepares three flow guide tubes with an inner diameter of 5 mm each, the same wall thickness and length, and numbers them 1-3 in sequence by the method of Example 1; prepares three flow guide tubes with an inner diameter of 4.5 mm, the same wall thickness and length by the method of Example 2, and numbers them 4-6 in sequence; detects the density of the 6 flow guide tubes, the integrity and inner diameter of the flow guide tubes after 8 hours of hydrogenation powder production using molten magnesium under the same conditions. The detection results are shown in the following table:

[0051]

[0052]

[0053] It can be seen from the above detection results that:

[0054] 1. Whether the inner diameter is 5 mm or 4.5 mm, the density of the flow guide tube exceeds 98%. The greater the density, the better the mechanical properties of the flow guide tube, the smaller the inner diameter change during use, and the longer the service life.

[0055] 2. All the flow guide tubes are intact after 8 hours of use, without rupture and shedding, which proves that the service life of the flow guide tube prepared by the present invention exceeds 8 hours, far exceeding the existing service life of only 3-20 minutes for the flow guide tube. Therefore, there is no need to frequently stop the machine to replace the flow guide tube, providing hardware support for the large-scale and efficient production of magnesium hydride.

[0056] 3. After 8 hours of use, the inner diameter change of the flow guide tube is extremely small, ensuring the consistency of the preparation process when using the flow guide tube in the present invention for magnesium-based metal hydrogenation powder production, making the quality of the prepared products more uniform. Secondly, after 8 hours of use, the inner diameter change rate of the flow guide tube is still far less than 2%. Therefore, the flow guide tube can still be used, that is, the service life of the flow guide tube prepared by the present invention far exceeds 8 hours, much higher than the service life of the existing flow guide tube.

[0057] The above are only the embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A method for preparing a flow guide tube for hydrogenation powder making, characterized in that: The following steps are involved: S1, preparing a dispersion solution using zirconium oxychloride, magnesium chloride, a dispersant and water; S2, mixing the dispersed solution with aqueous ammonia to obtain a mixed solution; S3, atomizing the mixed solution and heating the atomized droplets to dry them, the heating temperature being lower than 500° C. to obtain a mixed powder; S4, heating the mixed powder to 500-700° C. to obtain a powder block, and dispersing the powder block into powder; S5, hot pressing and sintering the powder into a composite ceramic rod; S6, machining the composite ceramic rod into a flow guide tube.

2. The method according to claim 1, characterized in that: In step 1, the zirconium ion concentration in the dispersed solution is 0.1-0.5 mol / L, and the magnesium ion concentration is 0.02-0.2 mol / L.

3. The method according to claim 2, characterized in that: When preparing the dispersion solution, heat the solution to 40-80°C.

4. The method according to claim 1, characterized in that: In step 2, the volume fraction of the dispersed solution in the mixed solution is 10 to 20 parts, and the volume fraction of the ammonia water is 80 to 90 parts.

5. The method according to claim 1, characterized in that: In step 3, high temperature gas is used to dry the droplets, and the high temperature gas is air or an inert gas.

6. The method according to claim 5, characterized in that: In step 3, a centrifugal spray dryer is used to atomize the dispersed solution, and the rotation speed of the centrifugal atomizer of the centrifugal spray dryer is 12000-18000 rpm / min.

7. The method according to claim 1, characterized in that: Step 4: In an atmospheric environment, the temperature is increased to a thermal decomposition temperature of 500 to 700° C. at a heating rate of 10 to 20° C. / min, and the mixture is kept at this temperature for 1 to 3 hours. After the temperature is kept at this temperature, the mixture is naturally cooled to room temperature.

8. The method according to claim 1, characterized in that: In step 5, the sintering temperature during hot pressing sintering is 1600-1800°C.

9. The method according to claim 8, characterized in that: Before sintering, the raw material is first heated to 600-800°C for pre-sintering and kept warm for 0.5-1h, and then heated to the sintering temperature for sintering; after reaching the sintering temperature, the solid raw material is pressurized at a pressure of 100-150 tons, kept warm and pressurized for 1-3h, and then cooled with the furnace to obtain a composite ceramic rod.

10. The method according to claim 9, characterized in that: During the entire heating process of step 5, the heating rate is controlled to be 10-20°C / min.

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