Method for preparing metal tantalum by adopting calcium thermal reduction method

Abstract

The invention relates to the technical field of rare metal preparation, in particular to a method for preparing metal tantalum by adopting a calcium thermal reduction method, which comprises the following steps: S1, material mixing: mixing tantalum pentoxide, calcium powder and calcium chloride according to a preset proportion to obtain a mixture; s2, synthesizing, namely putting the mixture into a high-temperature reaction device, and carrying out calcium thermal reaction, so that the calcium powder and the tantalum pentoxide react to generate tantalum and calcium oxide; s3, separation: after a product obtained in the synthesis step is cooled to room temperature, tantalum is separated from the eutectic of calcium chloride and calcium oxide, and a tantalum block is obtained; s4, smelting: smelting the tantalum block into a tantalum plate under a preset condition; thus, calcium chloride serving as a fluxing agent is added, calcium oxide generated in the reaction and calcium chloride form a liquid eutectic, a liquid environment is provided, and an ion transmission mode among raw materials is converted into solid-liquid mass transfer, so that the lower temperature limit of effective proceeding of the calcium thermal reaction is reduced, the reaction rate of tantalum pentoxide and calcium powder is greatly increased, and the preparation speed of tantalum is increased; the preparation period is shortened.

Description

Technical Field

[0001] The present invention relates to the technical field of rare metal preparation, and in particular to a method for preparing tantalum metal by using a calcium thermal reduction method. Background Art

[0002] Tantalum is an important rare metal that usually exists in nature in the form of tantalum ores, such as tantalite and niobium-tantalum ore. Due to its excellent properties such as high melting point, high density, high hardness and strong corrosion resistance, it is widely used in electronics, aerospace and defense.

[0003] At present, the main industrial methods for producing tantalum include potassium sodium fluorotantalate reduction method, sodium tantalum oxide / magnesium reduction method, carbon reduction method and aluminothermic reduction method. However, these tantalum preparation methods all have the problem of slow preparation speed. Specifically, the potassium sodium fluorotantalate reduction method requires multiple chemical reactions and repeated separation and purification of intermediate products, and the operation process is cumbersome and time-consuming; the reduction reaction of the sodium tantalum oxide / magnesium reduction method needs to be maintained at a specific high temperature for a long time to be completed, and the effective reaction rate is limited; the carbon reduction method relies on solid-solid phase reaction, and the efficiency of material transfer is low, and it is often necessary to extend the high-temperature reaction time to ensure the reduction effect; although the aluminothermic reduction method has a violent and rapid reaction, the cooling and solidification of the high-temperature molten product obtained after the reaction and the separation process of metallic tantalum and slag are complicated and time-consuming; the process limitations of the above-mentioned existing technologies reduce the preparation speed of tantalum and extend the preparation cycle of tantalum. Summary of the Invention

[0004] In view of this, it is necessary to provide a method for preparing metallic tantalum using a calcium thermal reduction method, which can increase the preparation speed of tantalum and shorten the preparation cycle of tantalum.

[0005] The present invention provides a method for preparing metallic tantalum by using a calcium thermal reduction method, comprising the following steps:

[0006] S1, mixing, mixing tantalum pentoxide, calcium powder and calcium chloride in a predetermined ratio to obtain a mixture;

[0007] S2, synthesis, placing the mixture in a high-temperature reaction device to cause a calcium thermal reaction, causing the calcium powder and tantalum pentoxide to react to produce tantalum and calcium oxide, and causing the products calcium oxide and calcium chloride to form a liquid eutectic, thereby achieving solid-liquid ion mass transfer between the tantalum pentoxide and the calcium powder, lowering the lower temperature limit for the effective calcium thermal reaction, and accelerating the reaction rate of the tantalum pentoxide and calcium powder;

[0008] S3, separation, after the product obtained in the synthesis step is cooled to room temperature, separating the tantalum from the eutectic of calcium chloride and calcium oxide to obtain a tantalum block;

[0009] S4, smelting, smelting the tantalum block into tantalum plates under predetermined conditions.

[0010] Preferably, in step S1, the mixing mass ratio of tantalum pentoxide, calcium powder and calcium chloride is 2.2:1-1.5:2-5; and the mixing time by the mixer is not less than 10 hours.

[0011] Preferably, the mixer is a V-shaped mixer to improve the uniformity of the mixture.

[0012] Preferably, the step S2 includes:

[0013] S201, placing the mixture into a high-temperature reaction device;

[0014] S202, using a scraper to compact the mixture so that the mixture is evenly filled in the high-temperature reaction device without gaps;

[0015] S203, slowly heating the high-temperature reaction device to 1000° C. to meet the conditions for the occurrence of the calcium thermal reaction;

[0016] S204, igniting the fuse on the high-temperature reaction device to initiate a calcium thermal reaction, causing the tantalum pentoxide and calcium powder to react to generate tantalum and calcium oxide.

[0017] Preferably, the step S204 further includes, after the calcium thermal reaction starts, controlling the temperature in the high-temperature reaction device to be not less than 1100° C., so that the reaction can proceed fully.

[0018] Preferably, step S3 includes:

[0019] S301, wait for at least 4 hours after the calcium thermal reaction of the synthesis step is completed to allow the high-temperature reaction device to cool to room temperature;

[0020] S302, removing tantalum generated by the calcium thermal reaction from the bottom of the high-temperature reaction device to obtain a reduced raw material block;

[0021] S303, removing calcium oxide attached to the surface of the reduction raw material block to obtain a tantalum-based block;

[0022] S304, crushing the tantalum base block into a predetermined size by a crusher to reduce the residual calcium oxide on the tantalum base block, thereby obtaining a tantalum block.

[0023] Preferably, the predetermined size is ≤50 mm, so as to facilitate placing the tantalum base block into a horizontal electron beam furnace for melting.

[0024] Preferably, the crusher is a jaw crusher to reduce production costs.

[0025] Preferably, step S4 includes:

[0026] S401, placing the tantalum block obtained in the separation step into a water-cooled copper crucible and then sending it into a horizontal electron beam furnace;

[0027] S402, adjusting the vacuum degree in the horizontal electron beam furnace to ≤0.05 Pa;

[0028] S403, setting the melting power and electron beam energy density of the horizontal electron beam furnace according to preset parameters, and performing directional solidification refining on the tantalum block to volatilize impurities;

[0029] S404, after the directional solidification refining is completed, the electron beam is stopped;

[0030] S405, after the horizontal electron beam furnace has cooled naturally, the horizontal electron beam furnace is opened and the water-cooled copper crucible is taken out;

[0031] S406, taking out the tantalum plate from the water-cooled copper crucible.

[0032] The above-mentioned method for preparing metallic tantalum by calcium thermal reduction comprises the following steps: S1, mixing, mixing tantalum pentoxide, calcium powder and calcium chloride in a predetermined ratio to obtain a mixture; S2, synthesis, placing the mixture in a high-temperature reaction device to cause a calcium thermal reaction, so that the calcium powder and tantalum pentoxide react to generate tantalum and calcium oxide, and the products calcium oxide and calcium chloride form a liquid eutectic, thereby achieving solid-liquid ion mass transfer between tantalum pentoxide and calcium powder, promoting the lower temperature limit for the effective calcium thermal reaction to be lowered, and accelerating the reaction rate of tantalum pentoxide and calcium powder; S3, separation, after the product obtained in the synthesis step is cooled to room temperature , separating tantalum from the eutectic of calcium chloride and calcium oxide to obtain a tantalum block; S4, smelting, smelting the tantalum block into a tantalum plate under predetermined conditions; in this way, the present invention adds calcium chloride as a flux to tantalum pentoxide and calcium powder, so that the calcium oxide produced by the calcium thermal reaction forms a liquid eutectic with the calcium chloride, thereby providing a liquid reaction environment, which changes the ion transmission mode between the tantalum pentoxide and the calcium powder from solid-solid diffusion to solid-liquid ion mass transfer, thereby significantly reducing the lower limit temperature at which the calcium thermal reaction is effective, greatly accelerating the reaction rate of tantalum pentoxide and calcium powder, and ultimately improving the preparation speed of tantalum and shortening the preparation cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the method for preparing metallic tantalum using the calcium thermal reduction method of the present application. DETAILED DESCRIPTION

[0034] The technical solutions and technical effects of the embodiments of the present invention are further elaborated in detail below with reference to the accompanying drawings of the present invention.

[0035] Please refer to Figure 1 The present invention provides a method for preparing metallic tantalum by using a calcium thermal reduction method, comprising the following steps:

[0036] S1, mixing, mixing tantalum pentoxide, calcium powder and calcium chloride in a predetermined ratio to obtain a mixture;

[0037] S2, synthesis, placing the mixture in a high-temperature reaction device to cause a calcium thermal reaction; causing the calcium powder and tantalum pentoxide to react to generate tantalum and calcium oxide, and causing the calcium chloride and calcium oxide to form a liquid eutectic, thereby achieving solid-liquid ion mass transfer between the tantalum pentoxide and the calcium powder, lowering the lower temperature limit for the effective calcium thermal reaction, and accelerating the reaction rate of the tantalum pentoxide and the calcium powder; specifically, the chemical reaction equation of the calcium powder and tantalum pentoxide is as follows:

[0038] Ta2O5+5Ca=2Ta+5CaO

[0039] ΔH=-1196kJ / mol at 1223K

[0040] S3, separation, after the product obtained in the synthesis step is cooled to room temperature, separating the tantalum from the eutectic of calcium chloride and calcium oxide to obtain a tantalum block;

[0041] S4, smelting, smelting the tantalum block into tantalum plates under predetermined conditions.

[0042] The present invention adds calcium chloride as a flux to tantalum pentoxide and calcium powder, so that calcium oxide produced by the calcium thermal reaction and calcium chloride form a liquid eutectic, which has the following beneficial effects:

[0043] 1. The liquid eutectic formed by calcium oxide and calcium chloride can provide a liquid environment for the reaction process of tantalum pentoxide and calcium powder, changing the contact mode between tantalum pentoxide and calcium powder from solid-solid diffusion to solid-liquid ion mass transfer, thereby significantly reducing the lower limit of the effective temperature for the reduction reaction and greatly accelerating the reaction rate. Specifically, the essence of calcium powder reducing tantalum pentoxide is that calcium captures oxygen from tantalum pentoxide, thereby generating a replacement reaction between metallic tantalum and calcium oxide. In the traditional solid-solid reaction mode, solid calcium powder is in direct contact with solid tantalum pentoxide particles, resulting in an extremely small effective reaction interface between the two, and the diffusion efficiency of calcium ions and oxygen ions in the solid is extremely slow, and the reaction generates Solid calcium oxide will wrap around the surface of unreacted substances to form a dense passivation layer, which seriously hinders the diffusion path of ions and forces the calcium thermal reaction to rely on high temperature conditions for difficult progress. The present invention introduces calcium chloride to form a liquid eutectic with calcium oxide, changing the reaction mechanism to solid-liquid ion mass transfer. Calcium powder is ionized in a liquid environment to provide freely migrating calcium ions. These calcium ions quickly diffuse to the surface of tantalum pentoxide particles through the high-speed ion channel of the liquid eutectic to undergo a reduction reaction. The calcium oxide generated during the reaction dissolves in the liquid eutectic, making it difficult to form a dense passivation layer that hinders the reaction, thereby reducing the temperature required for the calcium thermal reaction and allowing the calcium thermal reaction to proceed rapidly.

[0044] 2. The liquid eutectic formed by calcium oxide and calcium chloride can absorb part of the heat released by the calcium thermal reaction, avoiding local overheating and making the calcium thermal reaction more gentle and uniform;

[0045] 3. The liquid eutectic formed by calcium oxide and calcium chloride as a liquid medium can reduce the collision of metal tantalum particles in the melt, thereby inhibiting the growth of metal tantalum particles, avoiding excessive aggregation of metal tantalum particles, and further avoiding the formation of clusters, making the obtained tantalum block more uniform.

[0046] Furthermore, in step S1, the mixing mass ratio of tantalum pentoxide, calcium powder and calcium chloride is 2.2:1-1.5:2-5; the mixing time by the mixer is not less than 10 hours to ensure that the tantalum pentoxide, calcium powder and calcium chloride are evenly mixed to obtain a mixture.

[0047] In this embodiment, the ratio of tantalum pentoxide, calcium powder and calcium chloride is calculated according to a chemical equation, so as to enable the raw materials to react fully and reduce the waste of raw materials during the reaction process.

[0048] Furthermore, the mixer is a V-type mixer to improve the uniformity of the mixture. Specifically, the V-type mixer is provided with a double-barrel V-shaped structure, which can cause two-way convection mixing of the raw materials during the rotation process, so that powders of different densities and particle sizes can achieve a high degree of uniformity after long-term mixing; at the same time, compared with trough-type or single-barrel mixers, the dead-angle-free mixing characteristics of the V-type structure avoid local agglomeration or stratification, and meet the requirements of the calcium thermal reaction for uniform mixing of raw materials.

[0049] Furthermore, step S2 includes:

[0050] S201, placing the mixture into a high-temperature reaction device;

[0051] S202, using a scraper to compact the mixture so that the mixture is evenly filled in the high-temperature reaction device without gaps;

[0052] S203, slowly heating the high-temperature reaction device to 1000° C. to meet the conditions for the occurrence of the calcium thermal reaction;

[0053] S204, igniting the fuse on the high-temperature reaction device to initiate a calcium thermal reaction, causing the tantalum pentoxide and calcium powder to react to generate tantalum and calcium oxide.

[0054] In this embodiment, the temperature for producing tantalum by calcium thermal reaction (1000°C) is significantly lower than that of tantalum reduction method (1800-2200°C) and aluminum thermal reduction method (2200-2400°C), and the calcium thermal reaction is an exothermic reaction, and no external heat is required during the reaction process, thereby reducing the energy required for preparation and thus reducing the preparation cost.

[0055] Furthermore, step S204 also includes, after the calcium thermal reaction begins, controlling the temperature in the high-temperature reaction device to not less than 1100° C. to allow the reaction to proceed fully, for example, by adjusting the power of the heating device or controlling the valve to control the reaction temperature; specifically, when the temperature is lower than 1100° C., the reaction rate of the calcium thermal reaction is slow, and the calcium thermal reaction is difficult to proceed thoroughly, resulting in the inability of tantalum pentoxide to react completely.

[0056] In this embodiment, the reasons for not controlling the reaction temperature in the later stage of the calcium thermal reaction are: 1. The nature of the calcium thermal reaction is a strongly exothermic reaction. Once the reaction starts, the large amount of heat released will rapidly heat the unreacted raw materials, forming a "self-propagating" effect, so that the calcium thermal reaction continues to advance on its own, and it is difficult to intervene manually; 2. The temperature in the later stage of the calcium thermal reaction can reach 2000-3000°C, far exceeding the tolerance limit of conventional temperature control equipment. For example, thermocouples, heating elements, and temperature control equipment will fail due to high temperature; 3. The rapid temperature rise of the calcium thermal reaction makes the temperature field uneven, and traditional temperature control means are difficult to respond in real time; 4. The high temperature released by the calcium thermal reaction can make the by-product calcium oxide in a molten state, and the difference in density and surface tension between tantalum and calcium oxide can be used to naturally separate calcium oxide and solid tantalum; therefore, there is neither a means nor a need for temperature control in the later stage of the calcium thermal reaction.

[0057] Furthermore, step S3 includes:

[0058] S301, after the calcium thermal reaction of the synthesis step is completed, wait for at least 4 hours to allow the high-temperature reaction device to cool to room temperature. Specifically, since the subsequent steps involve manual operation, the temperature of the high-temperature reaction device must be low to ensure the personal safety of the operators;

[0059] S302, removing the tantalum generated by the calcium thermal reaction from the bottom of the high-temperature reaction device to obtain a reduced material block; specifically, when the temperature in the high-temperature reaction device is higher than the melting point of calcium, due to different densities, the lighter calcium chloride, calcium oxide and unreacted calcium powder are suspended in the upper part of the high-temperature reaction device, while the heavier tantalum is precipitated in solid form at the bottom of the high-temperature reaction device. After the high-temperature reaction device is cooled to room temperature, the operator needs to remove the tantalum from the bottom of the high-temperature reaction device.

[0060] S303, removing the calcium oxide attached to the surface of the raw material block to obtain a tantalum-based block; specifically, since calcium oxide has brittle fracture characteristics and weak adhesion, the calcium oxide on the surface of the raw material block can be removed by knocking.

[0061] S304, crushing the tantalum base block into a predetermined size by a crusher to reduce the residual calcium oxide on the tantalum base block, thereby obtaining a tantalum block.

[0062] In this embodiment, the crusher uses mechanical force to break the tantalum-based block containing calcium oxide, utilizing the brittle fracture characteristics of calcium oxide to break it into small pieces, while destroying the interfacial bonding force between calcium oxide and the tantalum-based block, making it easier for calcium oxide to detach, thereby reducing the residual calcium oxide in the tantalum-based block and further improving the purity of the tantalum block.

[0063] Furthermore, the predetermined size is ≤50 mm, so as to facilitate placing the tantalum base block into a horizontal electron beam furnace for melting.

[0064] Furthermore, the crusher is a jaw crusher to reduce production costs. This is because compared with other crushers, the jaw crusher has a simpler structure and lower maintenance costs.

[0065] Furthermore, step S4 includes:

[0066] S401, placing the tantalum block obtained in the separation step into a water-cooled copper crucible and then sending it into a horizontal electron beam furnace;

[0067] S402, adjusting the vacuum degree in the horizontal electron beam furnace to ≤0.05 Pa;

[0068] S403, setting the melting power and electron beam energy density of the horizontal electron beam furnace according to predetermined parameters, and performing directional solidification refining on the tantalum block to volatilize the impurities; specifically, the melting power of the horizontal electron beam furnace is 400kW, and the electron beam energy density is 3×10 3 J / m 2 ;

[0069] S404, after the directional solidification refining is completed, the electron beam is stopped;

[0070] S405, after the horizontal electron beam furnace has cooled naturally, the horizontal electron beam furnace is opened and the water-cooled copper crucible is taken out;

[0071] S406, taking out the tantalum plate from the water-cooled copper crucible.

[0072] In this embodiment, the water-cooled copper crucible refers to a copper rectangular container with a size of 2000 mm×300 mm×50 mm.

[0073] In this embodiment, the parameters of the horizontal electron beam furnace are adjusted to fully volatilize impurities to further improve the purity of the tantalum plate; the impurities are calcium oxide, carbon, nitrogen, hydrogen, tungsten, iron, silicon, chromium, nickel, molybdenum, titanium and niobium, among which tungsten, iron, silicon, chromium, nickel, molybdenum, titanium and niobium are all derived from tantalum ore.

[0074] Example 1: Preparation of tantalum plates using raw materials in different proportions

[0075] Material preparation: Prepare three groups of raw materials respectively, with the mass ratio of tantalum pentoxide, calcium powder and calcium chloride as follows: Group 1, 2.2:1:2; Group 2, 2.2:1:5; Group 3, 2.2:1.5:2;

[0076] Preparation steps:

[0077] Step 1: The raw materials are charged into a V-type mixer at a rotation speed of 60 to 120 rpm for 10 hours to obtain a mixture;

[0078] Step 2: Place the mixture into a high-temperature reaction device that is resistant to high temperatures and corrosion, and compact the mixture using a scraper or vibrator to ensure that the mixture is evenly filled in the high-temperature reaction device without gaps;

[0079] Step 3: After the high-temperature reaction device is placed in a heating device, the high-temperature reaction device is slowly heated to 1000° C. by the heating device;

[0080] Step 4: Ignite the fuse on the high-temperature reaction device to initiate a calcium thermal reaction, and adjust the power of the heating device or control the valve so that the temperature in the high-temperature reaction device is not less than 1100° C. during the calcium thermal reaction;

[0081] Step 5: After the calcium thermal reaction is completed, cool for 4 hours and remove the high-temperature reaction device from the heating equipment;

[0082] Step 6: After the high-temperature reaction device is cooled to room temperature, the reduced material blocks are taken out from the bottom of the high-temperature reaction device;

[0083] Step 7: After removing the calcium oxide on the surface of the reduced block by tapping, the block is crushed into 50 mm by a jaw crusher to obtain a tantalum block;

[0084] Step 8: Place the tantalum block into a water-cooled copper crucible and place it into a horizontal electron beam furnace, and adjust the vacuum level in the horizontal electron beam furnace to ≤0.05 Pa;

[0085] Step 9: The melting power of the horizontal electron beam furnace is 400 kW and the electron beam energy density is 3×10 3 J / m 2 Directional solidification refining of tantalum blocks under conditions of

[0086] Step 10: After the directional solidification refining is completed, the electron beam is stopped;

[0087] Step 11, after the horizontal electron beam furnace is naturally cooled, the horizontal electron beam furnace is opened, the water-cooled copper crucible is taken out, and the tantalum plate is taken out from the water-cooled copper crucible;

[0088] Step 12, the main element composition of the tantalum plate is analyzed by instrument, wherein the C analysis instrument is a carbon sulfur instrument, O and N analysis is performed by an oxygen nitrogen analyzer, and other metals are analyzed by inductively coupled plasma atomic emission spectrometry; the impurity data is shown in Table 1 as follows:

[0089] Table 1

[0090] Serial number C O N H W Fe Si Cr Ni Mo Ti Nb Ca Group 1 0.0006 0.025 0.01 0.0002 0.0005 0.0003 0.0005 0.0005 0.0003 0.0001 0.0001 0.0154 0.07 Group 2 0.0006 0.055 0.02 0.0002 0.0005 0.0003 0.0005 0.0005 0.0003 0.0001 0.0001 0.0176 0.08 Group 3 0.0006 0.031 0.02 0.0002 0.0005 0.0003 0.0005 0.0005 0.0003 0.0001 0.0001 0.0151 0.07

[0091] Wherein, the data corresponding to each element represents the percentage of its content in the tantalum plate;

[0092] The analysis of the experimental results of the three groups respectively shows that the impurity content of the first group of tantalum plates is less than 0.13%; the impurity content of the second group of tantalum plates is less than 0.18%; and the impurity content of the third group of tantalum plates is less than 0.14%, the purity of the three groups of tantalum plates is higher than 99.8%, which meets the purity requirements of industrial tantalum in the national standard; wherein, the impurities refer to the total content of C, O, N, H, W, Fe, Si, Cr, Ni, Mo, Ti, Nb and Ca in the tantalum plate.

[0093] Example 2, influence of calcium chloride on the calcium thermal reaction rate

[0094] 1. Experimental grouping

[0095] The raw material ratio of the control group is: tantalum pentoxide: calcium powder = 2.2: 1.5 (mass ratio)

[0096] The raw material ratio of the experimental group is: tantalum pentoxide: calcium powder: calcium chloride = 2.2: 1.5: 5 (mass ratio)

[0097] 2. Experimental process

[0098] Step 1, mixing, two groups of raw materials are respectively loaded into a V-type mixer, the mixing time is 10 hours, and two groups of mixed materials are obtained;

[0099] Step 2, loading, the two groups of mixed materials are respectively loaded into the same size reaction device, and the scraper is used to compact without gap;

[0100] Step 3, preheating, the reaction devices of the two groups are synchronously and slowly heated to 1000℃;

[0101] Step 4, synthesis, the ignition line of the two groups of reaction devices is synchronously ignited, and the temperature of the two groups of reaction devices is ensured to be not lower than 1100℃ during the calcium thermal reaction process;

[0102] Step 5, recording, the time and temperature of the calcium thermal reaction of the two groups are respectively recorded, wherein the reaction temperature is recorded by the thermocouple installed in the reaction device;

[0103] The above experiment is repeated three times, and the data shown in Table 2 is obtained:

[0104] Table 2

[0105]

[0106] Analysis of the experimental data in Table 2 shows that, compared with the control group without calcium chloride, the average reaction temperature of the experimental group with the addition of calcium chloride is reduced from 1398-1480°C to 1150-1283°C; the reaction time is reduced from 60-66 min to 45-50 min. It can be concluded that the addition of calcium chloride can effectively reduce the temperature required for the calcium thermal reaction between tantalum pentoxide and calcium powder, and effectively shorten the time for the calcium thermal reaction between tantalum pentoxide and calcium powder.

[0107] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing tantalum metal by calcium thermal reduction, characterized in that: The following steps are involved: S1, mixing, mixing tantalum pentoxide, calcium powder and calcium chloride in a predetermined ratio to obtain a mixture; S2, synthesis, placing the mixture in a high-temperature reaction device to cause a calcium thermal reaction, causing the calcium powder and tantalum pentoxide to react to produce tantalum and calcium oxide, and causing the products calcium oxide and calcium chloride to form a liquid eutectic, thereby achieving solid-liquid ion mass transfer between the tantalum pentoxide and the calcium powder, lowering the lower temperature limit for the effective calcium thermal reaction, and accelerating the reaction rate of the tantalum pentoxide and calcium powder; S3, separation, after the product obtained in the synthesis step is cooled to room temperature, separating the tantalum from the eutectic of calcium chloride and calcium oxide to obtain a tantalum block; S4, smelting, smelting the tantalum block into tantalum plates under predetermined conditions.

2. The method for preparing tantalum metal by calcium thermal reduction according to claim 1, wherein: In step S1, the mixing mass ratio of tantalum pentoxide, calcium powder and calcium chloride is 2.2:1-1.5:2-5; and the mixing time in the mixer is not less than 10 hours.

3. The method for preparing tantalum metal by calcium thermal reduction according to claim 2, characterized in that: The mixer is a V-shaped mixer to improve the uniformity of the mixing of the mixture.

4. The method for preparing tantalum metal by calcium thermal reduction according to claim 1, wherein: The step S2 comprises: S201, placing the mixture into a high-temperature reaction device; S202, using a scraper to compact the mixture so that the mixture is evenly filled in the high-temperature reaction device without gaps; S203, slowly heating the high-temperature reaction device to 1000° C. to meet the conditions for the occurrence of the calcium thermal reaction; S204, igniting the fuse on the high-temperature reaction device to initiate a calcium thermal reaction, causing the tantalum pentoxide and calcium powder to react to generate tantalum and calcium oxide.

5. The method for preparing tantalum metal by calcium thermal reduction according to claim 4, characterized in that: The step S204 further includes, after the calcium thermal reaction starts, controlling the temperature in the high temperature reaction device to be not less than 1100° C. to allow the reaction to proceed fully.

6. The method for preparing tantalum metal by calcium thermal reduction according to claim 1, wherein: Preferably, step S3 includes: S301, wait for at least 4 hours after the calcium thermal reaction of the synthesis step is completed to allow the high-temperature reaction device to cool to room temperature; S302, removing tantalum generated by the calcium thermal reaction from the bottom of the high-temperature reaction device to obtain a reduced raw material block; S303, removing calcium oxide attached to the surface of the reduction raw material block to obtain a tantalum-based block; S304, crushing the tantalum base block into a predetermined size by a crusher to reduce the residual calcium oxide on the tantalum base block, thereby obtaining a tantalum block.

7. The method for preparing tantalum metal by calcium thermal reduction according to claim 6, characterized in that: The predetermined size is ≤50 mm, so as to facilitate placing the tantalum base block into a horizontal electron beam furnace for smelting.

8. The method for preparing tantalum metal by calcium thermal reduction according to claim 6, characterized in that: The crusher is a jaw crusher to reduce production costs.

9. The method for preparing tantalum metal by calcium thermal reduction according to claim 1, wherein: The step S4 comprises: S401, placing the tantalum block obtained in the separation step into a water-cooled copper crucible and then sending it into a horizontal electron beam furnace; S402, adjusting the vacuum degree in the horizontal electron beam furnace to ≤0.05 Pa; S403, setting the melting power and electron beam energy density of the horizontal electron beam furnace according to preset parameters, and performing directional solidification refining on the tantalum block to volatilize impurities; S404, after the directional solidification refining is completed, the electron beam is stopped; S405, after the horizontal electron beam furnace has cooled naturally, the horizontal electron beam furnace is opened and the water-cooled copper crucible is taken out; S406, taking out the tantalum plate from the water-cooled copper crucible.

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