Ultrafine magnesium powder preparation device

Abstract

The invention belongs to the field of metal powder manufacturing, and provides a superfine magnesium powder preparation device which comprises a smelting furnace, a vacuum pump, a spraying device, a collecting tower, a liquid storage tank, a first pressure pump and a second pressure pump, the spraying device comprises a venturi tube and a magnesium liquid conveying tube, and the venturi tube comprises an inlet, a throat tube and a spraying opening; the liquid storage tank is connected with an inlet of the venturi tube through a first pipeline, and a first pressure pump is arranged on the first pipeline; the other end of the magnesium liquid conveying pipe is inserted into the throat pipe; a vacuum pump is arranged on the smelting furnace; the smelting furnace is connected with the liquid storage tank through a second pipeline, and a second pressure pump is arranged on the second pipeline. And the venturi tube is connected with the upper end of the collecting tower through the jet orifice. As the venturi tube is adopted to prepare the magnesium powder, the magnesium powder with controllable particle size, small particle size distribution range and high roundness can be obtained; the activity of the magnesium powder is ensured by replacing oxygen in the preparation system with rare gas and controlling the environment humidity; the preparation equipment is simple in structure and free of moving parts, and equipment investment is greatly reduced.

Description

Technical Field

[0001] The invention relates to energetic materials and belongs to the field of metal powder manufacturing, and in particular to a device and method for preparing ultrafine magnesium powder. Background Art

[0002] Ultrafine magnesium powder below 400 mesh (38 microns) has a large specific surface area and strong surface activity. It is an important energetic material and can be used to manufacture chemical products, explosives, fireworks, etc. It can also be used as a reducing agent, desulfurizer, 3D printing raw material, and is widely used in military industry, aerospace industry, steelmaking industry, non-ferrous metal casting and other fields. In view of the process requirements, it is necessary to prepare ultrafine magnesium powder with smaller particle size, smaller particle size distribution range, higher roundness and activity.

[0003] Ultrafine magnesium powder is highly active and can react with water or oxygen at room temperature, releasing heat, leading to combustion and explosion. Therefore, the magnesium powder manufacturing process is relatively complicated.

[0004] Existing methods for preparing magnesium powder include grinding and milling (crushing) method, emulsification method, eddy current crushing method, atomization method and air flow crushing method.

[0005] Patents CN202011059832.2 and CN201510018764.8 use grinding and milling (crushing) methods, which are mechanical crushing methods. Most of the powders produced are diamond-shaped or other irregular shapes, with a particle size of only 20-150 mesh, and the activity and loose density are relatively low.

[0006] Patent No. CN101758224A provides a method for preparing nano magnesium powder by high frequency cutting at low temperature, but this method requires ultra-high speed (5500-6000 rpm) for cutting, which consumes a lot of energy and has low production efficiency.

[0007] Patent 201310082862.9 proposes a pneumatic atomization production method for high-purity fine spherical magnesium powder. Spherical magnesium powder is prepared by argon atomization and nitrogen cooling. This method requires the use of nitrogen, argon and cooling and separation devices, and the equipment is expensive and the process is complicated.

[0008] Patents WO2024040946A1, 201710726429.2, CN102615289A, CN103862060A, CN102615289A, and 202111623596.7 use heating of magnesium raw materials to obtain magnesium vapor, which is then condensed to obtain magnesium powder. The equipment is complex and expensive, the particle size distribution range is large, the energy consumption is high, and large-scale applicability is poor.

[0009] Therefore, there is an urgent need for a simple and efficient method to solve the problems existing in the preparation process of ultrafine magnesium powder, including excessively large particle size, large distribution range, insufficient roundness, low activity, expensive equipment and complex process. Summary of the invention

[0010] In order to solve the problems of large magnesium powder particle size, wide particle size distribution range, low roundness and activity, expensive equipment and complex process, the present invention provides a method for preparing ultrafine magnesium powder.

[0011] To achieve the above purpose, the technical means adopted by the present invention are:

[0012] Provided is a device for preparing ultrafine magnesium powder, comprising a furnace, a vacuum pump, an injection device, a collection tower, a liquid storage tank, a first pressure pump and a second pressure pump, wherein the injection device comprises a venturi and a magnesium liquid delivery pipe, and the venturi comprises an inlet, a throat and an injection port;

[0013] The liquid storage tank is connected to the inlet of the venturi tube through a first pipeline, the diameter of the first pipeline is the same as the diameter of the inlet of the venturi tube, and a first pressure pump is arranged on the first pipeline;

[0014] One end of the magnesium liquid delivery pipe is connected to the furnace, and the other end is inserted into the throat;

[0015] A vacuum pump is provided on the furnace;

[0016] The melting furnace is connected to the liquid storage tank through a second pipeline, and a second pressure pump is arranged on the second pipeline.

[0017] The venturi is connected to the upper end of the collection tower through an injection port.

[0018] Furthermore, a valve is provided on the magnesium liquid delivery pipe.

[0019] Further, the diameter of the inlet of the venturi is 30-100 mm, the diameter of the throat is 3-10 mm, and the diameter of the outlet is 10-80 mm.

[0020] Furthermore, the inner diameter of the magnesium liquid delivery pipe is 2.0 mm.

[0021] Furthermore, a partition is fixed to the inner wall of the furnace chamber of the melting furnace, which divides the furnace chamber into an upper chamber and a lower chamber. The partition has a through hole passing through it, and a float is provided in the lower chamber. The diameter of the float is larger than the diameter of the through hole. The liquid level of the magnesium liquid is maintained within a preset range through the cooperation between the float and the through hole.

[0022] Furthermore, one end of the magnesium liquid delivery pipe is connected to the lower chamber of the furnace.

[0023] Furthermore, the partition is arranged to be inclined, and the center point of the through hole is higher than the center point of the partition.

[0024] Furthermore, a multi-stage vibrating screener is provided inside the collection tower.

[0025] Furthermore, the multi-stage vibrating screener includes a primary vibrating screener and a secondary vibrating screener, and the mesh aperture of the primary vibrating screener is larger than the mesh aperture of the secondary vibrating screener.

[0026] Furthermore, it also includes a gas circulation system, which includes a gas recovery device, a liquid storage tank and the above-mentioned first pipeline; the gas recovery device includes a dust removal filter, a cooler and a third pressure pump; one end of the dust removal filter is connected to the collection tower, and the other end is connected to the cooler, and a third pressure pump is arranged between the dust removal filter and the cooler; the other end of the cooler is connected to the liquid storage tank.

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

[0028] 1) The turbulence formed by the high-speed flowing gas-liquid mixture in the venturi is used to simultaneously mix, crush and cool the magnesium liquid, and the magnesium powder with controllable particle size and small particle size distribution range is obtained by controlling the injection speed of the gas-liquid mixture; and the magnesium powder with high roundness is obtained by rapid cooling of the magnesium liquid after crushing.

[0029] 2) The gas-liquid mixture uses rare gases that do not react with magnesium, and the environmental humidity in the magnesium powder preparation system is strictly controlled to ensure the activity of the magnesium powder.

[0030] 3) The core component of the magnesium powder preparation system is the injection tube with Venturi effect, which has a simple structure, no moving parts, and greatly reduces equipment investment. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0032] Figure 1 This is a flow chart of the preparation of ultrafine magnesium powder of the present invention;

[0033] Figure 2 This is a front view of the ultrafine magnesium powder preparation device of the present invention;

[0034] Figure 3 It is a right view of the ultrafine magnesium powder preparation device of the present invention;

[0035] Figure 4 It is a top view of the ultrafine magnesium powder preparation device of the present invention;

[0036] Figure 5Schematic diagram of the ultrafine magnesium powder preparation device of the present invention

[0037] Figure 6 It is a cross-sectional view of the ultrafine magnesium powder preparation device of the present invention;

[0038] Figure 7 It is a cross-sectional view of the ultrafine magnesium powder preparation device of the present invention;

[0039] Figure 8 It is a cross-sectional view of the ultrafine magnesium powder preparation device of the present invention;

[0040] Fig. 9 It is a front view of the furnace of the ultrafine magnesium powder preparation device of the present invention;

[0041] Fig.10 A top view of a furnace of the ultrafine magnesium powder preparation device of the present invention;

[0042] Fig.11 A sectional view of a furnace of the ultrafine magnesium powder preparation device of the present invention;

[0043] Fig.12 It is a structural diagram of the injection device of the ultrafine magnesium powder preparation device of the present invention;

[0044] Fig.13 A top view of the injection device of the ultrafine magnesium powder preparation device of the present invention;

[0045] Fig.14 This is a cross-sectional view of the injection device of the ultrafine magnesium powder preparation device of the present invention.

[0046] in:

[0047] 1. Liquid rare gas; 2. First booster pump; 3. Furnace; 4. Molten magnesium liquid; 5. Residue; 6. Float; 7. Injection device; 8. Partition; 9. Atomized nucleated magnesium powder; 10. Vibrating screen; 11. Screen; 12. Ultrafine magnesium powder; 13. Dust filter; 14. Cooler; 15. Liquid storage tank; 16. Throat; 17. Magnesium liquid delivery pipe; 18. Through hole; 19. Collection tower; 20. Vacuum pump; 21. Venturi tube; 22. Second booster pump; 23. Third booster pump; 24. First pipeline; 25. Second pipeline. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] First, refer to the attached Figure 1 and attached Figure 12-14 The present embodiment provides a method for preparing magnesium powder, which is prepared by using a venturi 21; a gas-liquid mixture enters the venturi 21 at a first speed, and magnesium liquid enters the venturi 21 at a second speed, and the gas-liquid mixture and the magnesium liquid are mixed at the throat 16 of the venturi 21 to form magnesium powder; the gas-liquid mixture does not chemically react with magnesium; and the first speed is at least 5 m / s.

[0050] Specifically, the gas-liquid mixture enters the venturi 21 at a first speed, and the magnesium liquid enters the venturi 21 at a second speed. The gas-liquid mixture and the magnesium liquid are mixed at the throat 16 of the venturi 21 to form magnesium droplets with uniform particle size. The magnesium droplets solidify into magnesium powder at the end of the venturi 21.

[0051] The preparation of magnesium powder generally uses inert gas to atomize magnesium liquid, and then the atomized magnesium liquid is cooled by a cooling system to form magnesium powder. The equipment is relatively complicated, and the particle size of the magnesium powder is difficult to control if the magnesium powder is simply atomized by gas, often resulting in magnesium powder with a wide range of particle sizes.

[0052] This embodiment adopts a venturi 21 device to prepare magnesium powder. Specifically, the gas-liquid mixture enters the venturi 21 at a high speed, and forms a turbulent flow at the throat 16. The turbulent flow has the characteristics of disorder and diffusion, and can quickly shear and mix the substances entering the turbulent flow. The magnesium liquid delivery pipe 17 is arranged at the throat 16. After the molten magnesium liquid enters the throat 16 of the venturi 21, the molten magnesium liquid quickly enters the center of the high-speed flowing gas-liquid mixture mixed turbulent flow, and is crushed by the gas-liquid mixture turbulent flow to form magnesium liquid droplets with uniform particle size.

[0053] In this embodiment, the molten magnesium liquid is atomized by using a gas-liquid mixture. Specifically, the gas-liquid mixture enters the venturi 21 at a first speed, and the magnesium liquid enters the venturi 21 at a second speed, and the gas-liquid mixture and the magnesium liquid are mixed at the throat 16 of the venturi 21.

[0054] It is understandable that the greater the flow rate of the gas-liquid mixture, the better the crushing effect of the turbulent flow on the molten magnesium liquid, and the smaller the particle size of the formed magnesium powder. In other words, by controlling the injection speed of the gas-liquid mixture, magnesium powder with controllable particle size and small particle size distribution range is obtained. The gas-liquid mixture of this embodiment enters the venturi 21 at a speed of not less than 3 m / s.

[0055] The slower the speed at which the molten magnesium enters the venturi 21, the smaller the amount of magnesium liquid entering the venturi 21, and the smaller the particle size of the magnesium powder formed. In order to obtain magnesium powder with uniform particle size, it is necessary to control the flow rate of the magnesium liquid entering the venturi 21. The magnesium liquid in this embodiment enters the venturi 21 at a speed of 10 g / s-500 g / s, preferably 200-300 g / s.

[0056] It is understandable that the flow rate of the gas-liquid mixture and the flow rate of the magnesium liquid can obtain magnesium powder of the target particle size when they are adapted. Therefore, in actual production, the flow rate of the gas-liquid mixture and the flow rate of the magnesium liquid can be adjusted accordingly.

[0057] After the magnesium liquid enters the throat 16 of the venturi 21, it meets the gas-liquid mixture and is first crushed by the turbulent flow of the gas-liquid mixture to form magnesium liquid droplets with uniform particle size. At the same time, the droplets exchange heat with the liquid rare gas and gaseous rare gas molecules, and the magnesium liquid droplets are rapidly cooled and solidified into magnesium powder at the end of the venturi 21, and then sprayed into the collection tower 19. Since the magnesium liquid is rapidly cooled and solidified after forming droplets, the roundness of the magnesium powder is better.

[0058] That is to say, in this embodiment, the mixing, crushing and cooling of the magnesium liquid can be carried out simultaneously in the venturi 21, which can ensure the formation of magnesium powder with a small particle size range and a standard roundness.

[0059] The gas-liquid mixture does not chemically react with magnesium.

[0060] It is understandable that magnesium is an active metal and is very likely to react chemically with oxygen in the air. Therefore, the preparation process of magnesium powder needs to be isolated from air. In this embodiment, a gas that does not react chemically with magnesium is used to replace the air in the magnesium powder preparation system, and the magnesium liquid is crushed with a gas-liquid mixture, which can effectively prevent the oxidation of magnesium and ensure that the activity of the magnesium powder will not be reduced.

[0061] Further, the gas-liquid mixture is composed of rare gases, including helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). It is understandable that since the outermost electrons of rare gases are fully arranged, they are generally chemically stable and not prone to chemical reactions. The air in the magnesium powder preparation system is replaced by rare gases, and under the protection of the rare gases, the magnesium powder will not be oxidized, thereby obtaining highly active magnesium powder.

[0062] The gas-liquid mixture of the rare gas enters the venturi 21 at a high speed and mixes with the magnesium liquid, absorbs heat and vaporizes, and is subsequently filtered, cooled, and pressurized for recycling.

[0063] It can be understood that the gas-liquid mixture is a combination of liquid helium and gaseous helium, or a combination of liquid helium and gaseous argon. All gas-liquid mixtures composed of rare gases belong to solid-liquid mixtures.

[0064] It is understandable that the gas constituting the gas-liquid mixture, in addition to rare gases, may also be nitrogen and other chemical substances that do not react with magnesium.

[0065] Furthermore, the mass ratio of the gas-liquid mixture is 1:10-1:30, preferably 1:15-1:25.

[0066] It is mainly controlled by adjusting the flow rate of liquid argon entering the venturi 21. The larger the liquid argon flow rate, the smaller the mass ratio of the gas-liquid mixture formed by the liquid argon vaporizing when heated. The smaller the liquid argon flow rate, the larger the mass ratio of the gas-liquid mixture formed by the liquid argon vaporizing when heated. This flow rate is controlled by the first booster pump 2 installed on the first pipeline 24.

[0067] It is understood that the use of a gas-liquid mixture can simultaneously play the following roles:

[0068] 1. Use the high-speed airflow to form the Venturi effect;

[0069] 2. Utilize the latent heat of evaporation of liquid argon to rapidly cool and solidify the crushed magnesium droplets to form ultrafine magnesium powder with good roundness;

[0070] 3. When the liquid argon droplets are vaporized, their volume expands rapidly, further "exploding" the liquid magnesium droplets to form ultrafine magnesium powder.

[0071] Therefore, by reasonably controlling the ratio of liquid and gaseous rare gases, magnesium powder with particle size, particle size range and roundness that meet practical applications can be obtained. The preferred ratio of liquid and gaseous rare gases is 1:23, and the most likely particle size of the magnesium powder is 460nm, the particle size distribution range is 350-510nm, and the roundness is 0.008um.

[0072] For further information, see Attachment Figure 1-8 , further comprising a furnace 33, a collecting tower 19 and a pipeline, a venturi 21, a collecting tower 19 and a pipeline constitute a preparation system, and the preparation system is used to collect magnesium powder, and the steps are as follows:

[0073] 1) After the absolute pressure of the preparation system drops below 100 Pa, the entire preparation system is filled with rare gas;

[0074] 2) The temperature of furnace 3 is raised to above 651°C and maintained at a constant temperature;

[0075] 3) gradually increasing the flow rate of the gas-liquid mixture at the throat 16 to a first speed, the magnesium liquid enters the venturi 21 at a second speed, the gas-liquid mixture is mixed with the magnesium liquid at the throat 16 of the venturi 21 to form magnesium droplets with uniform particle size and the first gas, and the magnesium droplets solidify into magnesium powder in the venturi 21;

[0076] 4) Screening the magnesium powder to obtain ultrafine magnesium powder.

[0077] It is understandable that magnesium is an active metal and can be oxidized by oxygen or water vapor in the air at room temperature. Therefore, the magnesium powder should be avoided from contact with air as much as possible during its preparation. In this embodiment, a rare gas is used to replace the air in the magnesium powder preparation system to avoid oxidation reaction during the magnesium powder preparation process.

[0078] Specifically, when preparing magnesium powder, after adding magnesium metal blocks to the melting furnace 3, the magnesium powder preparation system is closed, and vacuum is first evacuated to reduce the absolute pressure of the system to below 100 Pa, and then purged with rare gas to remove the air in the system, especially oxygen, to complete the operation of replacing the air with rare gas in the system.

[0079] The melting point of magnesium is 651°C, so the magnesium block must be heated to above 651°C to melt it into liquid magnesium. Specifically, the heating furnace is turned on to ensure that the temperature rises to above 651°C, preferably 720°C, and the temperature is maintained constant to ensure that the magnesium block is fully melted into liquid.

[0080] After the liquid rare gas is fed into the venturi 21, the heat absorbing part is vaporized to become a high-pressure and high-speed gas-liquid mixed gas flow. When the gas-liquid mixed gas flow passes through the throat 16 of the venturi 21 at high speed, according to the Bernoulli equation, a negative pressure is generated at the throat 16, and the molten magnesium is sucked into the throat 16 of the venturi 21. After the molten magnesium enters the throat 16, it is crushed and atomized by the high-speed gas flow, and is quickly condensed by the cold rare gas (a mixture of gaseous and liquid rare gases). The high-quality and high-speed atomization and rapid cooling ensure that the particle size and particle size distribution range of the formed ultrafine magnesium powder meet the production requirements and maintain a high roundness, and then it is collected.

[0081] That is, by adjusting the speed and pressure of the rare gas delivery pump, the rare gas injection speed is adjusted, and then the atomization degree and cooling speed of the metal magnesium melt are adjusted to control the particle size, particle size distribution range and roundness of the magnesium powder, as well as the production efficiency, and prepare magnesium powder with a particle size that meets the requirements. The relationship between the particle size, particle size distribution range and roundness and the flow rate of the gas-liquid mixture and the flow rate of the magnesium liquid has been described in detail above.

[0082] For further information, see Attachment Figure 6-8 The magnesium powder is screened to obtain ultrafine magnesium powder. The magnesium powder is screened by a multi-stage vibrating screener 10, wherein the multi-stage vibrating screener 10 includes a primary vibrating screener and a secondary vibrating screener, wherein the mesh aperture of the primary vibrating screener is larger than the mesh aperture of the secondary vibrating screener.

[0083] In order to further narrow the particle size distribution range of magnesium powder, the present embodiment is provided with a multi-stage vibrating screener 10 for multi-stage screening of magnesium powder. The multi-stage vibrating screener 10 includes a primary vibrating screener and a secondary vibrating screener, and the mesh aperture of the primary vibrating screener is larger than the mesh aperture of the secondary vibrating screener. Preferably, the primary screening uses a 200 mesh screen, and the secondary screening uses a 400 mesh screen.

[0084] It is understood that by setting up a multi-stage vibrating screener 10, magnesium powder is screened according to particle size to obtain magnesium powder with different particle size distribution ranges. The first-stage screening uses a 200-mesh screen to obtain magnesium powder with a particle size range of 33 to 74 um. The second-stage screening uses a 400-mesh screen to obtain magnesium powder with a particle size less than 33 um.

[0085] Furthermore, it also includes magnesium powder passivation.

[0086] The passivation method is: mixing rare gas and oxygen to obtain a mixed gas, slowly passing the mixed gas into a collection tower 19, vibrating or stirring the magnesium powder, so that a dense magnesium oxide film is formed on the surface of the magnesium powder.

[0087] It can be understood that the pre-mixed rare gas and oxygen mixed gas is slowly introduced into the collection tower 19, and under vibration and stirring, the surface of the magnesium powder can be controlled to be oxidized to form a dense magnesium oxide film to prevent further deep oxidation of the magnesium powder.

[0088] Furthermore, the relative humidity of the gas in the preparation system does not exceed 2%. Preferably, the relative humidity of the gas in the system does not exceed 0.5%.

[0089] This is to reduce the moisture content in the magnesium powder preparation system, prevent water from reacting with magnesium powder, and reduce the activity of magnesium powder. During the whole process, the dew point (humidity) of the gas in the system needs to be strictly monitored, and the relative humidity is controlled not to exceed 2%. Preferably, the relative humidity of the gas in the system does not exceed 0.5%. If necessary, an inert desiccant should be added to the system.

[0090] For further information, see Attachment Figure 1 , 2 , 4, 6, also includes the first gas being dedusted, pressurized, cooled to form a liquid, and then recovered and recycled.

[0091] Specifically, after the liquid rare gas enters the venturi 21, it absorbs heat and partially vaporizes, and further vaporizes after contacting the molten magnesium liquid to form a first gas. After the first gas is dust-removed and filtered, it is pressurized to about 10 MPa, sent to the cooler 14 to be cooled to below minus 80° C., and sent back to the liquid storage tank 15 to achieve the recovery and recycling of the rare gas.

[0092] After the magnesium liquid is treated, the rare gas contains ultrafine magnesium powder, which can be put into use again after dust removal and filtration by the dust removal filter 13. Therefore, ultrafine magnesium powder remains in the dust removal filter 13, and the ultrafine magnesium powder can be recovered by regularly cleaning the dust removal filter 13.

[0093] For further information, see Attachment Figure 9-11, also includes a furnace 3 for melting magnesium blocks, an inclined partition 8 is fixed to the inner wall of the furnace chamber of the furnace 3, and the furnace chamber of the furnace 3 is divided into an upper chamber and a lower chamber, the partition 8 has a through hole 18 penetrating therethrough, and a float 6 is provided in the lower chamber, and the diameter of the float 6 is greater than the diameter of the through hole 18. The liquid level of the magnesium liquid is maintained within a preset range through the cooperation of the float 6 and the through hole 18. As a possible implementation method, the preset range can be between 1 / 10 and 1 / 2 of the furnace chamber height; the preset range can also be between 1 / 5 and 1 / 3 of the furnace chamber height, preferably 1 / 4 of the furnace chamber height.

[0094] It can be understood that after the magnesium block is completely melted, metals with higher melting points (such as iron, copper, etc.) and non-metallic residues will settle at the bottom of the slope of the partition 8 and be collected; and the circular hole of the ball valve is in the middle position, and the residue will not enter the lower part of the furnace chamber through the circular hole, and thus will not enter the injection port, thereby ensuring the purity of the produced magnesium powder.

[0095] It is understandable that the liquid level of the magnesium liquid is maintained in a suitable height range by the cooperation of the float 6 and the through hole 18, that is, after the magnesium block in the upper chamber of the furnace is melted into magnesium liquid, the magnesium liquid flows into the lower chamber through the through hole 18, and the ball float can float on the surface of the magnesium liquid. The amount of magnesium liquid in the lower chamber increases, and the liquid level of the magnesium liquid rises, and the float rises accordingly, until the float blocks the through hole, and the magnesium liquid in the upper chamber cannot continue to flow into the lower chamber, and the liquid level of the magnesium liquid in the lower chamber no longer rises. When the position of the partition and the through hole is fixed, the liquid level of the magnesium liquid in the lower chamber needs to be higher when the float with a small diameter reaches the position of the through hole, and the liquid level of the magnesium liquid in the lower chamber needs to be lower when the float with a large diameter reaches the position of the through hole. Therefore, by selecting floats of different diameters, the height of the liquid level of the magnesium liquid in the lower chamber can be achieved within a preset range.

[0096] When magnesium powder is prepared, the magnesium liquid in the lower chamber of the furnace flows out, the liquid level of the magnesium liquid drops, and the float 6 drops accordingly. The float 6 and the through hole 18 on the partition 8 are separated from the contact state, and the magnesium liquid in the upper chamber flows into the lower chamber through the gap between the through hole 18 and the float 6, so that the liquid level of the magnesium liquid in the lower chamber rises. The float 6 rises accordingly and contacts the through hole 18 again, thereby blocking the through hole 18 and preventing the magnesium liquid in the upper chamber from flowing into the lower chamber, thereby adjusting and controlling the liquid level of the magnesium liquid in the lower chamber to always remain within a preset range.

[0097] The above preset range can ensure the speed at which the magnesium liquid flows out of the pipeline. Figure 1 It can be seen that the first end of the magnesium liquid delivery pipe 17 is arranged in the middle of the lower chamber of the furnace chamber, and the magnesium liquid enters the throat 16 of the venturi tube 21 from the lower chamber of the furnace chamber through the magnesium liquid delivery pipe 17. The flow rate of the magnesium liquid is positively correlated with the pressure of the magnesium liquid at the first end of the magnesium liquid delivery pipe 17, and the pressure of the magnesium liquid at the first end depends on the height of the magnesium liquid level. Therefore, in order to maintain the stability of the magnesium liquid flow rate, the liquid level of the lower layer of magnesium liquid needs to be always kept within a preset range.

[0098] The flow rate of the magnesium liquid is closely related to the particle size of the magnesium powder. Specifically, the slower the speed at which the magnesium liquid enters the venturi 21, the less magnesium liquid enters the venturi 21, and the smaller the particle size of the magnesium powder formed. In order to obtain magnesium powder with uniform particle size, it is necessary to control the flow rate of the magnesium liquid entering the venturi 21.

[0099] In a second aspect, this embodiment also provides a magnesium powder prepared by the above-mentioned magnesium powder preparation method.

[0100] In a third aspect, this embodiment also provides an ammunition made from the above-mentioned magnesium powder.

[0101] The particle size of magnesium powder directly affects the combustion and explosion activity of magnesium powder and the stability of the product.

[0102] The smaller the particle size of magnesium powder, the greater its activity. Specifically, the minimum ignition temperature, minimum ignition energy, and lower explosion limit concentration parameters of magnesium powder decrease as the particle size decreases; the maximum explosion pressure and maximum pressure rise rate parameters of magnesium powder increase as the particle size decreases. Therefore, magnesium powder with a small particle size is needed in the ammunition field.

[0103] However, the smaller the particle size of magnesium powder, the worse the stability. Therefore, the particle size of magnesium powder should also meet the stability requirements to ensure the safety of storage and transportation.

[0104] Therefore, there is an optimal particle size requirement for magnesium powder used in ammunition to take into account both activity (usage requirements) and stability (storage requirements).

[0105] From the perspective of use, the narrower the particle size distribution range, the better the uniformity and homogeneity of the powder, which is more conducive to the loading of ammunition and the full play of its explosive performance.

[0106] The roundness of magnesium powder will affect the quality and performance of ammunition.

[0107] The unevenness of the powder will affect:

[0108] 1) Bulk density and filling density, which in turn affect the size and filling amount of the package; further affect the speed of explosion and the uniformity of explosion temperature;

[0109] 2) If the roundness is not enough or even there are spikes, it may cause local hot spots and non-critical points to detonate.

[0110] The ammunition manufactured by the above method improves the safety during production, assembly and transportation and the controllability of ammunition explosion due to the use of magnesium powder with small particle size, small particle size distribution range and good roundness.

[0111] Specifically, the most probable particle size of the magnesium powder in this embodiment is 480 nm, the particle size distribution range is 330-610 nm, and the roundness is not greater than 0.01 um.

[0112] In a fourth aspect, this embodiment also provides a firework made from the above magnesium powder. The firework includes military flares, flash bombs, jamming bombs and civilian fireworks.

[0113] In a fifth aspect, the present embodiment further provides a device for preparing ultrafine magnesium powder, comprising a furnace 3, a vacuum pump 20, an injection device 7, a collection tower 19, a liquid storage tank 15, a first pressure pump 2 and a second pressure pump 22, the injection device 7 comprising a venturi 21 and a magnesium liquid delivery pipe 17, the venturi 21 comprising an inlet, a throat 16 and an injection port;

[0114] The liquid storage tank 15 is connected to the inlet of the venturi tube 21 through a first pipeline 24. The diameter of the first pipeline 24 is the same as the diameter of the inlet of the venturi tube 21. The first pipeline 24 is provided with a first pressure pump 2.

[0115] One end of the magnesium liquid delivery pipe 17 is connected to the melting furnace 3, and the other end is inserted into the throat pipe 16;

[0116] The furnace 3 is provided with a vacuum pump 20;

[0117] The melting furnace 3 is connected to the liquid storage tank 15 via a second pipeline 25 , and a second pressure pump 22 is provided on the second pipeline 25 .

[0118] The venturi 21 is connected to the upper end of the collection tower 19 through the injection port.

[0119] Specifically, the furnace 3 is used to melt the magnesium block. After the magnesium metal block is added to the furnace 3, the magnesium powder preparation device is closed. The vacuum pump 20 is first used to evacuate the entire magnesium powder preparation device to reduce the absolute pressure of the system to below 100 Pa, and then purged with a rare gas to remove the air in the magnesium powder preparation device, especially oxygen, to complete the operation of replacing the air with the rare gas in the magnesium powder preparation device.

[0120] The melting point of magnesium is 651°C. Turn on the heating furnace to ensure that the temperature rises to above 651°C, preferably 720°C, and maintain a constant temperature to ensure that the magnesium block is fully melted into liquid.

[0121] After the liquid rare gas is fed into the injection device 7, the heat absorbing part is vaporized to become a high-pressure and high-speed gas-liquid mixed gas flow. When the gas-liquid mixed gas flow passes through the throat 16 of the injection device 7 at high speed, according to the Bernoulli equation, a negative pressure is generated at the throat 16, and the molten magnesium is sucked into the throat 16 of the venturi 21. After the molten magnesium enters the throat 16, it is crushed and atomized by the high-speed gas flow, and at the same time, it is quickly condensed by the cold rare gas (a mixture of gaseous and liquid rare gases). The high-quality and high-speed atomization and rapid cooling ensure that the formed ultrafine magnesium powder maintains a high roundness, and then is injected into the collection tower 19 for collection.

[0122] That is to say, by adjusting the speed and pressure of the rare gas delivery pump, the rare gas injection speed is adjusted, and then the atomization degree and cooling rate of the molten magnesium are adjusted to control the particle size and distribution of the magnesium powder, as well as the production efficiency, to prepare magnesium powder with the required particle size.

[0123] Furthermore, the magnesium liquid delivery pipe 17 is provided with a valve, preferably a high-temperature mechanical valve.

[0124] The size of the magnesium powder particle size is related to the speed of the magnesium liquid entering the venturi 21. The smaller the speed of the magnesium liquid entering the venturi 21, the smaller the particle size of the magnesium powder formed. By effectively and stably controlling the speed of the magnesium liquid entering the venturi, the particle size stability of the magnesium powder product is ensured, and the distribution range of the magnesium powder particle size is small.

[0125] The control mode of magnesium liquid entering the venturi 21 can also be controlled by valve control, preferably a high temperature mechanical valve. The high temperature mechanical valve is arranged on the magnesium liquid conveying pipe 17 to adjust the flow rate of magnesium liquid.

[0126] As a possible implementation, the control method of the magnesium liquid entering the venturi 21 can be pressure control. Specifically, the furnace 3 is connected to the liquid storage tank 15 through the second pipeline 25, and the second pipeline 25 is provided with a second booster pump 22. The pump adjusts the pressure of the gas entering the furnace 3 from the liquid storage tank 15 so that the gas pressure in the furnace 3 reaches a set value, at which the flow rate of the magnesium liquid can meet the particle size requirements of the magnesium powder.

[0127] As a possible implementation manner, the control method for the magnesium liquid to enter the venturi 21 can also be controlled by the air flow velocity according to the Venturi effect, that is, the greater the flow velocity of the gas-liquid mixture, the greater the inlet velocity of the magnesium liquid, and the smaller the flow velocity of the gas-liquid mixture, the smaller the inlet velocity of the magnesium liquid.

[0128] For further information, see Attachment Figure 12-14 The diameter of the inlet of the venturi tube 21 is 30-100 mm, the diameter of the throat 16 is 3-10 mm, and the diameter of the outlet is 10-80 mm.

[0129] Furthermore, the inner diameter of the magnesium liquid delivery pipe 17 is 2.0 mm.

[0130] Furthermore, a partition 8 is fixed to the inner wall of the furnace chamber of the melting furnace 3, and the partition 8 divides the furnace chamber into an upper chamber and a lower chamber. The partition 8 has a through hole 18 extending therethrough, and a float 6 is provided in the lower chamber. The diameter of the float 6 is larger than the diameter of the through hole 18. The liquid level of the magnesium liquid is maintained within a preset range through the cooperation between the float 6 and the through hole 18. As a possible implementation method, the preset range may be between 1 / 10 and 1 / 2 of the furnace chamber height; the preset range may also be between 1 / 5 and 1 / 3 of the furnace chamber height, preferably 1 / 4 of the furnace chamber height.

[0131] Furthermore, one end of the magnesium liquid delivery pipe 17 is connected to the lower chamber of the melting furnace 3 .

[0132] It is understandable that the liquid level of the magnesium liquid is maintained in a suitable height range by the cooperation of the float 6 and the through hole 18, that is, after the magnesium block in the upper chamber of the furnace is melted into magnesium liquid, the magnesium liquid flows into the lower chamber through the through hole 18, and the ball float can float on the surface of the magnesium liquid. The amount of magnesium liquid in the lower chamber increases, and the liquid level of the magnesium liquid rises, and the float rises accordingly, until the float blocks the through hole, and the magnesium liquid in the upper chamber cannot continue to flow into the lower chamber, and the liquid level of the magnesium liquid in the lower chamber no longer rises. When the position of the partition and the through hole is fixed, the liquid level of the magnesium liquid in the lower chamber needs to be higher when the float with a small diameter reaches the position of the through hole, and the liquid level of the magnesium liquid in the lower chamber needs to be lower when the float with a large diameter reaches the position of the through hole. Therefore, by selecting floats of different diameters, the height of the liquid level of the magnesium liquid in the lower chamber can be achieved within a preset range.

[0133] When magnesium powder is prepared, the magnesium liquid in the lower chamber of the furnace flows out, the liquid level of the magnesium liquid drops, and the float 6 drops accordingly. The float 6 and the through hole 18 on the partition 8 are separated from the contact state, and the magnesium liquid in the upper chamber flows into the lower chamber through the gap between the through hole 18 and the float 6, so that the liquid level of the magnesium liquid in the lower chamber rises. The float 6 rises accordingly and contacts the through hole 18 again, thereby blocking the through hole 18 and preventing the magnesium liquid in the upper chamber from flowing into the lower chamber, thereby adjusting and controlling the liquid level of the magnesium liquid in the lower chamber to always remain within a preset range.

[0134] The above preset range can ensure the speed at which the magnesium liquid flows out of the pipeline. Figure 1 It can be seen that the first end of the magnesium liquid delivery pipe 17 is arranged in the middle of the lower chamber of the furnace chamber, and the magnesium liquid enters the throat 16 of the venturi tube 21 from the lower chamber of the furnace chamber through the magnesium liquid delivery pipe 17. The flow rate of the magnesium liquid is positively correlated with the pressure of the magnesium liquid at the first end of the magnesium liquid delivery pipe 17, and the pressure of the magnesium liquid at the first end depends on the height of the magnesium liquid level. Therefore, in order to maintain the stability of the magnesium liquid flow rate, the liquid level of the lower layer of magnesium liquid needs to be always kept within a preset range.

[0135] The flow rate of the magnesium liquid is closely related to the particle size of the magnesium powder. Specifically, the slower the speed at which the magnesium liquid enters the venturi 21, the less magnesium liquid enters the venturi 21, and the smaller the particle size of the magnesium powder formed. In order to obtain magnesium powder with uniform particle size, it is necessary to control the flow rate of the magnesium liquid entering the venturi 21.

[0136] For further information, see Attachment Fig.11 , the partition 8 is arranged tilted, and the center point of the through hole 18 is higher than the center point of the partition 8.

[0137] It can be understood that after the magnesium block is completely melted, metals with higher melting points (such as iron, copper, etc.) and non-metallic residues will settle at the bottom of the slope of the partition 8 and be collected; and the circular hole of the ball valve is in the upper middle position, and the residue will not enter the lower chamber of the furnace 3 through the circular hole, and thus will not enter the injection port, thereby ensuring the purity of the produced magnesium powder.

[0138] For further information, see Attachment Figure 6-8 A multi-stage vibrating screener 10 is provided inside the collecting tower 19 .

[0139] In order to further screen the magnesium powder, sieves with different mesh sizes are provided in this embodiment to further screen the magnesium powder with a smaller particle size range.

[0140] For further information, see Attachment Figure 6-8 The multi-stage vibrating screener 10 includes a primary vibrating screener and a secondary vibrating screener, and the mesh aperture of the primary vibrating screener is larger than the mesh aperture of the secondary vibrating screener.

[0141] The mesh size of the first-stage vibrating screener is 150-300 mesh, preferably 200 mesh, and the second-stage vibrating screener is equipped with a mesh size of 300-500, preferably 400 mesh.

[0142] It can be understood that by providing a multi-stage vibrating screener 10, magnesium powder is screened according to particle size to obtain magnesium powder with different particle size distribution ranges.

[0143] By setting a multi-stage vibrating screener 10, magnesium powder is screened according to particle size to obtain magnesium powder with different particle size distribution ranges. The first-stage screening uses a 200-mesh screen and the second-stage screening uses a 400-mesh screen; two specifications of magnesium powder with a particle size range of 33 to 74 um and a particle size less than 33 um can be obtained.

[0144] For further information, see Attachment Figure 1 , 2 , 4, 6, and also include a gas circulation system, the gas circulation system includes a gas recovery device, a liquid storage tank 15 and the above-mentioned first pipeline 24;

[0145] The gas recovery device includes a dust removal filter 13, a cooler 14 and a third pressure pump 23;

[0146] One end of the dust filter 13 is connected to the collection tower 19, and the other end is connected to the cooler 14. A third pressure pump 23 is provided between the dust filter 13 and the cooler 14.

[0147] The other end of the cooler 14 is connected to the liquid storage tank 15 .

[0148] Specifically, after the liquid rare gas enters the injection device 7, the heat absorbing part is vaporized, and after contacting with the molten magnesium liquid, it is further vaporized to form a first gas in the collection tower 19. The first gas enters the dust removal filter 13, and after dust removal and filtration, it is pressurized to about 10 MPa, sent to the cooler 14 to be cooled to below minus 80°C, and sent back to the liquid storage tank 15 to realize the recovery and recycling of the rare gas.

[0149] After the magnesium liquid is treated, the rare gas contains ultrafine magnesium powder, which can be put into use again after dust removal and filtration by the dust removal filter 13. Therefore, ultrafine magnesium powder remains in the dust removal filter 13, and the ultrafine magnesium powder can be recovered and collected by regularly cleaning the dust removal filter 13.

[0150] Furthermore, the working process of the gas recovery device is as follows: after the gas is dust-removed and filtered by the dust removal filter 13, it is pressurized to 10MPa by the third pressure pump 23, transported into the cooler 14 to be cooled to below -80°C, and transported into the liquid storage tank 15 to achieve gas recovery and recycling.

[0151] The following is a comparison of magnesium powders obtained by different preparation methods and under different preparation conditions.

[0152] Examples 1, 2, 3, 4, and 5 were used to prepare magnesium powder according to the preparation conditions in Table 1. The specific operation steps were as follows:

[0153] 1. Cut the purchased magnesium bars or blocks into small magnesium blocks less than 10 cm square and put them into the heating furnace;

[0154] 2. With the argon valve closed, evacuate the entire system; after the absolute pressure of the system drops below 100Pa, keep evacuating for more than 10 minutes, slowly open the argon valve, and fill the entire system with argon;

[0155] 3. Turn on the heating furnace, raise the temperature to 720°C at a rate of 10°C per minute, and keep the temperature constant for more than 30 minutes;

[0156] 4. Adjust the speed of the first argon booster pump 2 connected to the injection port, gradually increase the flow rate of the injection port to the set speed, and the gas-liquid mixture ratio (gas: liquid) reaches the set value;

[0157] 5. Open the valve of the magnesium liquid delivery pipe 17;

[0158] 6. The multi-stage vibrating screener in the collection tower 19 screens the fallen metal magnesium powder;

[0159] 7. Collect high-purity and high-roundness magnesium powder at the bottom of the collection tower 19;

[0160] 8. After the argon gas is dust-removed and filtered, it is pressurized to about 10 MPa, sent to the cooler 14 for cooling to below -80°C, and then sent back to the liquid argon tank for recovery and recycling;

[0161] 9. Close all valves connected to the collection tower 19 and proceed to the next step of magnesium powder passivation (if necessary), collection, packaging and other post-processing steps.

[0162] Comparative Examples 1 and 2 are prior art, and magnesium powder is prepared according to conventional conditions and steps.

[0163] Table 1. Comparison of performance parameters of magnesium powder obtained by different preparation methods and conditions

[0164]

[0165] As can be seen from Table 1, the most probable particle size, particle size distribution range, roundness and high activity of the magnesium powder prepared by the venturi in Examples 1, 2, 3, 4 and 5 are superior to those prepared by the mechanical method and the ordinary atomization method.

[0166] It can be seen from Examples 1, 2, and 3 that the greater the injection speed of the gas-liquid mixture, the smaller the particle size of the magnesium powder obtained, the narrower the particle size distribution range, and the better the roundness. By setting the injection speed of the gas-liquid mixture, magnesium powders of different specifications can be obtained.

[0167] It can be seen from Examples 1, 4, and 5 that when the gas-liquid mixture ratio (gas: liquid) is 23:1, the obtained magnesium powder has the smallest possible particle size of 460nm, the narrowest particle size distribution range of 350-510nm, the best roundness, no more than 0.008um, which is the optimal value of the gas-liquid mixture ratio. At this optimal value, the parameters of the obtained magnesium powder are optimal.

[0168] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0169] It is not difficult for those skilled in the art to understand that the present invention includes any combination of the invention content and specific implementation methods of the above specification and the various parts shown in the drawings. Due to the limited space and to make the specification concise, the various schemes composed of these combinations are not described one by one. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0170] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for preparing ultrafine magnesium powder, comprising a furnace, a vacuum pump, an injection device, a collection tower, a liquid storage tank, a first pressure pump and a second pressure pump, characterized in that: The injection device comprises a venturi and a magnesium liquid delivery pipe, wherein the venturi comprises an inlet, a throat and an injection port; The liquid storage tank is connected to the inlet of the venturi tube through a first pipeline, the diameter of the first pipeline is the same as the diameter of the inlet of the venturi tube, and a first pressure pump is arranged on the first pipeline; One end of the magnesium liquid delivery pipe is connected to the furnace, and the other end is inserted into the throat; A vacuum pump is provided on the furnace; The furnace is connected to the liquid storage tank via a second pipeline, and a second pressure pump is arranged on the second pipeline; The venturi is connected to the upper end of the collection tower through an injection port.

2. The preparation device according to claim 1, characterized in that: A valve is provided on the magnesium liquid delivery pipe.

3. The preparation device according to claim 1, characterized in that: The diameter of the venturi tube at the inlet is 30-100mm, the diameter at the throat is 3-10mm, and the diameter at the outlet is 10-80mm.

4. The preparation device according to claim 1, characterized in that: The inner diameter of the magnesium liquid delivery pipe is 2.0 mm.

5. The preparation device according to claim 1, characterized in that: A partition is fixed on the inner wall of the furnace chamber, which divides the furnace chamber into an upper chamber and a lower chamber. The partition has a through hole passing through it. A float is provided in the lower chamber. The diameter of the float is larger than the diameter of the through hole. The float and the through hole cooperate to keep the liquid level of the magnesium liquid within a preset range.

6. The preparation device according to claim 5, characterized in that: One end of the magnesium liquid delivery pipe is connected to the lower chamber of the furnace.

7. The preparation device according to claim 5, characterized in that: The partition is tilted, and the center point of the through hole is higher than the center point of the partition.

8. The preparation device according to claim 1, characterized in that: A multi-stage vibrating screener is arranged inside the collection tower.

9. The preparation device according to claim 8, characterized in that: The multi-stage vibrating screener comprises a primary vibrating screener and a secondary vibrating screener, wherein the mesh aperture of the primary vibrating screener is larger than the mesh aperture of the secondary vibrating screener.

10. The preparation device according to claim 1, characterized in that: It also includes a gas circulation system, which includes a gas recovery device, a liquid storage tank and the first pipeline; The gas recovery device includes a dust removal filter, a cooler and a third pressure pump; One end of the dust removal filter is connected to the collection tower, and the other end is connected to the cooler, and a third pressure pump is arranged between the dust removal filter and the cooler; The other end of the cooler is connected to the liquid storage tank.

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