A method for preparing titanium metal powder by stepwise reduction of aluminum and magnesium

Abstract

The present invention provides a method for preparing metallic titanium powder by aluminum-magnesium step-by-step reduction. The method includes performing a two-step reduction treatment on titanium dioxide. First, aluminum is used to reduce a titanium oxide source to obtain TiO x (0.167≤x≤0.5) intermediate powder is then deeply reduced with magnesium to obtain metallic titanium powder; the method described in the present invention utilizes aluminum to first remove more than 75wt% of oxygen in titanium dioxide, greatly reducing the use of reducing agent magnesium, thereby effectively reducing the reducing agent cost in the process of preparing metallic titanium; moreover, the method utilizes wet separation technology to dissolve and separate the alumina-enriched by-product phase obtained by aluminum reduction with dilute acid, and no longer uses the conventional high-temperature slag-metal separation method of thermite self-propagating reaction, which not only has higher separation efficiency, but also greatly reduces the temperature requirement of the reaction system, and the reaction is controllable and easier to scale up safely.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical metallurgy, and in particular to a method for preparing metallic titanium powder by stepwise reduction of aluminum and magnesium. Background Art

[0002] Titanium is a rare, active metal with a high melting point and excellent physical and chemical properties. It has become a popular sustainable development material due to its low density, high specific strength, high temperature resistance, strong corrosion resistance and good biocompatibility.

[0003] As another metal with excellent performance and wide applications after iron and aluminum, titanium consumption is 2-3 orders of magnitude lower than aluminum and 5 orders of magnitude lower than steel. This difference in demand is due to the differences in their application areas. Due to cost constraints, titanium in my country is mainly used in high-end fields such as high-end chemical industry, aerospace, and marine engineering, making it difficult to achieve a breakthrough in volume. However, the application of aluminum and steel is closer to civilian fields such as construction, transportation, and home appliances.

[0004] Titanium is a typical chemically active metal. Its high chemical reactivity makes it difficult to fully dissociate the titanium and oxygen in titanium oxide via direct reduction. The preparation of metallic titanium is more difficult and expensive than for more common metals. To reduce titanium smelting costs, researchers worldwide have conducted extensive research on titanium preparation processes, including the ADMA method (a modification of the Kroll method), the Armstrong method (continuous sodium thermal reduction), the PRP method (calcium thermal reduction), the FFC method (electrochemical reduction), and the USTB method. The key to the ADMA method is the introduction of hydrogen into the reduction, phase separation, and cooling steps, integrating the magnesium thermal reduction and hydrogenation processes to directly produce titanium hydride powder, which is expected to reduce titanium powder production costs and energy consumption. The Armstrong method is a typical method for preparing metallic titanium powder or titanium alloy powder based on the continuous sodium reduction of TiCl₄ (or TiCl₄ and alloying element chlorides), requiring further reduction of the oxygen content. The PRP method, also known as the preformed reduction method, preforms TiO₂ with CaO or CaCl₂, a binder, and then produces uniform titanium powder using metallic calcium vapor reduction. The FFC Cambridge process uses TiO2 as the cathode and graphite as the anode to produce titanium metal through electrolysis. However, this method suffers from low current efficiency and the need to replace inert anodes to avoid carbon contamination of the product. The USTB method uses TiO2 carbothermal reduction to prepare a highly conductive titanium carbon oxide as the anode, and then electrolyzes a conductive metal as the cathode to produce titanium metal. However, this method suffers from difficulties in anode preparation and low current efficiency. Currently, thermochemical methods generally suffer from high reducing agent costs, and electrochemical methods generally suffer from low current efficiency.

[0005] Furthermore, the cost of processing titanium metal into forgings / parts is high, with approximately 60% of this cost incurred during the titanium forming process. Currently, forging is the mainstream method for titanium processing, but this is plagued by long processes, complex processing, low metal utilization, and low direct yield, resulting in high prices for titanium parts. This significantly limits the material's application. Directly producing titanium products from titanium metal using powder metallurgy offers a range of advantages, particularly for small titanium and titanium alloy parts. The key lies in obtaining qualified powdered titanium raw materials. There are various methods for preparing titanium metal / titanium alloy powders. The most popular method for producing titanium powder is the hydrogenation-dehydrogenation (HDH) process, which exploits the fact that titanium becomes brittle and easily breakable after hydrogenation, and that titanium hydride readily decomposes and dehydrogenates at high temperatures to convert it into titanium metal. Using titanium sponge or residual titanium as raw materials, HDH produces titanium metal and titanium alloy powders with irregular morphologies through surface purification, hydrogenation, grinding, dehydrogenation, and screening. However, the HDH method does not have the function of purification, and the purity of the powder depends on the purity of the raw materials; and in general, the O / N content of the obtained powder increases too much and is difficult to control.

[0006] The HAMR method is a novel magnesium thermal reduction method for TiO2 proposed in recent years. Its key steps include magnesium reduction in a hydrogen atmosphere, heat treatment, and magnesium deoxidation in a hydrogen atmosphere. This method not only has the potential to reduce the smelting cost of titanium metal, but also directly produces high-quality titanium metal powder with low oxygen content, providing a new development direction for titanium powder metallurgy. However, the cost of the reducing agent is still relatively high.

[0007] Therefore, it is necessary to further reduce the cost proportion of the reducing agent in this method. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for preparing metallic titanium powder by aluminum-magnesium step-by-step reduction. The method can save the cost of reducing agents. Although aluminum is used as the reducing agent, there is no need to adopt a high-temperature slag-metal separation method. Not only is the separation efficiency higher, but the temperature requirement for the reaction system is also greatly reduced. The reaction is controllable and easier to scale up safely, and the industrial application prospect is broad.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction, the method comprising the following steps:

[0011] (1) Mixing a calcium titanium source, a first reducing agent and a first auxiliary agent, and sequentially performing a first reduction and a first wet treatment to obtain TiO x Intermediate powder, wherein 0.167≤x≤0.5; the first reducing agent includes aluminum;

[0012] (2) TiO xThe intermediate powder is subjected to a second reduction by a second reducing agent and then to a second wet process to obtain metallic titanium powder, wherein the second reducing agent includes magnesium.

[0013] The cost of aluminum as a reducing agent is lower than that of magnesium. However, since traditional aluminum reduction generally uses the method of self-propagating aluminum heat, an aluminum phase that is difficult to dissolve in acid or water will be generated during the reduction process. Subsequently, a high-temperature slag-metal separation method is required. Wet treatment cannot be used to separate aluminum and titanium. There is a problem of incomplete separation, and the temperature conditions required for separation are harsh, which to a certain extent reduces the cost advantage of the reducing agent.

[0014] The present invention has found that the combination of calcium-containing substances and a first auxiliary agent, based on aluminum as a reducing agent, can control the reduced aluminum phase to a calcium-aluminum compound soluble in dilute acid. On the one hand, the chemical composition of the reduction by-product phase is changed, especially the generation of substances with more negative Gibbs free energy, and on the premise that no titanium-aluminum alloy phase is generated, the reaction " "The original equilibrium state (when no titanium-aluminum alloy phase is generated, according to the oxygen potential, the reduction reaction can only obtain TiO), and TiO with lower oxygen content is obtained. x On the other hand, the controlled generation of this calcium-aluminum compound that is easily soluble in dilute acid can transform the conventional slag-metal stratification physical separation method caused by self-propagating ultra-high temperature reaction into wet separation, which makes the separation more thorough, significantly improves the subsequent separation cost and operational safety, and obtains higher purity TiO x Compared with the conventional magnesium reduction method, the cost of reducing agent is significantly reduced by more than 60%, which has great value in the field of industrial application.

[0015] In the present invention, the value of x is 0.167≤x≤0.5, for example, it can be 0.167, 0.18, 0.19, 0.20, 0.22, 0.25, 0.28, 0.29, 0.30, 0.32, 0.35, 0.38, 0.40, 0.42, 0.45, 0.47 or 0.5.

[0016] Preferably, the metallic titanium powder of the present invention refers to titanium powder with an oxygen content of ≤0.5wt%, for example, it can be 0.5wt%, 0.45wt%, 0.4wt%, 0.35wt%, 0.3wt%, 0.25wt% or 0.2wt%.

[0017] Preferably, the calcium-containing titanium source in step (1) comprises any one or a combination of at least two of a first titanium source, a second titanium source, a third titanium source or a fourth titanium source; the first titanium source is a mixture of titanium dioxide and calcium oxide, the second titanium source is a mixture of calcium oxide and calcined titanium dioxide, the third titanium source is a mixture of a calcined product obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio of CaTiO3 and calcium oxide, and the fourth titanium source is a mixture obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio exceeding CaTiO3 and calcining.

[0018] Preferably, the calcination temperature of the second titanium source, the third titanium source or the fourth titanium source is independently 1000~1400°C, for example, it can be 1000°C, 1044°C, 1088°C, 1132°C, 1176°C, 1220°C, 1264°C, 1308°C, 1352°C or 1400°C, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] Preferably, the molar ratio of calcium in the calcium-containing titanium source to the first reducing agent in step (1) is 0.6-2:1, for example, it can be 0.6:1, 0.75:1, 0.9:1, 1.05:1, 1.2:1, 1.35:1, 1.5:1, 1.65:1, 1.8:1 or 2:1, etc.

[0020] Preferably, the molar ratio of the first reducing agent to titanium in the calcium titanium source is 1 to 1.33:1, for example, it can be 1:1, 1.04:1, 1.07:1, 1.11:1, 1.14:1, 1.18:1, 1.22:1, 1.25:1, 1.29:1 or 1.33:1, etc.

[0021] The present invention further preferably has the molar ratio of calcium, titanium and the first reducing agent in the first reduction be within the above range, which can ensure that the first reduction reaches the set oxygen content level while avoiding the formation of an insoluble aluminum phase.

[0022] Preferably, in step (1), the first auxiliary agent comprises any one of anhydrous CaCl2, KCl, NaCl, CaCl2-KCl eutectic salt, CaCl2-NaCl eutectic salt, CaCl2-LiCl eutectic salt, KCl-NaCl eutectic salt, LiCl-NaCl eutectic salt, LiCl-KCl eutectic salt, AlCl3-KCl eutectic salt or AlCl3-NaCl eutectic salt, or a combination of at least two thereof, wherein typical but non-limiting combinations are: a combination of CaCl2 and KCl, a combination of CaCl2 and NaCl, a combination of CaCl2 and CaCl2-LiCl eutectic salt, a combination of CaCl2 and CaCl2-NaCl eutectic salt, a combination of CaCl2 and AlCl3-NaCl eutectic salt, a combination of CaCl2-NaCl eutectic salt and CaCl2-LiCl eutectic salt, a combination of CaCl2-NaCl eutectic salt and CaCl2-KCl eutectic salt, and a combination of CaCl2-KCl eutectic salt and AlCl3-NaCl eutectic salt.

[0023] The present invention further prefers calcium-containing substances as the first auxiliary agent, which can better control the formation of aluminum phase that is easily soluble in dilute acid and avoid aluminum in TiO x Residue in the intermediate powder, while ensuring TiO x The oxygen content in the intermediate powder reaches the set level.

[0024] Preferably, the weight ratio of the first auxiliary agent to the titanium in the calcium titanium source calculated as TiO2 is 0.05~3:1, for example, it can be 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 2.8:1 or 3.0:1, etc.

[0025] Preferably, the first reducing agent is in the form of powder, chips or granules, or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of powder and chips, a combination of granules and chips, and a combination of powder and granules.

[0026] Preferably, the temperature of the first reduction in step (1) is 700-1400°C, for example, 700°C, 777°C, 855°C, 932°C, 1010°C, 1087°C, 1165°C, 1242°C, 1320°C or 1400°C, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0027] Preferably, the first reduction time is 0.25 to 24 hours, for example, 0.25 hours, 3.0 hours, 5.6 hours, 8.2 hours, 10.7 hours, 13.5 hours, 16.1 hours, 18.8 hours, 21.5 hours or 24 hours, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0028] Preferably, the first reducing atmosphere comprises a vacuum or protective atmosphere.

[0029] Preferably, the first reducing protective atmosphere comprises any one or a combination of at least two of argon, hydrogen or helium, wherein typical but non-limiting combinations are: a combination of argon and hydrogen, a combination of argon and helium, a combination of hydrogen and helium, and a combination of argon, hydrogen and helium.

[0030] Preferably, the first wet treatment in step (1) comprises: slurrying the product of the first reduction with water and / or acid solution to obtain a slurry; the slurry is successively subjected to pH adjustment and solid-liquid separation, and the obtained solid phase is successively washed and dried to obtain TiO x (0.167≤x≤0.5) intermediate powder.

[0031] Preferably, the second wet treatment in step (2) includes: slurrying the product of the second reduction with water and / or acid solution to obtain a slurry; the slurry is successively pH-adjusted and solid-liquid separated, and the obtained solid phase is successively washed and dried to obtain metallic titanium powder.

[0032] Preferably, the pH of the acid solution in the first wet treatment and the second wet treatment is independently ≥0.5, for example, it can be 0.5, 0.7, 0.9, 1, 1.2, 1.4, 1.5, 1.7, 1.9 or 2, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0033] Preferably, the liquid-to-solid ratio of the slurry in the first wet treatment and the second wet treatment is independently 1 to 100:1 mL / g, for example, it can be 1:1 mL / g, 12:1 mL / g, 23:1 mL / g, 34:1 mL / g, 45:1 mL / g, 56:1 mL / g, 67:1 mL / g, 78:1 mL / g, 89:1 mL / g or 100:1 mL / g, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0034] Preferably, the acid used for pH adjustment in the first wet treatment and the second wet treatment is independently hydrochloric acid.

[0035] Preferably, the pH of the slurry is independently controlled to be ≥ 0.8 in the pH adjustment in the first wet treatment and the second wet treatment, for example, it can be 0.8, 1.1, 1.3, 1.6, 1.8, 2.1, 2.3, 2.6, 2.8 or 3, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0036] Preferably, the pH of the slurry after pH adjustment in the first wet treatment and the second wet treatment is independently 1.5 to 3.0, for example, it can be 1.5, 1.7, 1.9, 2, 2.2, 2.4, 2.5, 2.7, 2.9 or 3.0, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0037] In the present invention, in order to prevent TiO x (0.167≤x≤0.5) The intermediate powder and the titanium metal powder undergo a dissolution reaction with the acid during the pH adjustment process. The pH value of the slurry in the pH adjustment process is preferably controlled to be above 0.8. The pH adjustment is considered to be completed when the pH value stabilizes between 1.5 and 3.0 and no longer changes.

[0038] Preferably, the washing temperature in the first wet treatment and the second wet treatment is independently 0~60℃, for example, it can be 0℃, 7℃, 14℃, 20℃, 27℃, 34℃, 40℃, 47℃, 54℃ or 60℃, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the washing comprises washing with water.

[0040] Preferably, the drying temperature in the first wet treatment and the second wet treatment is independently ≤60°C, for example, 40°C, 43°C, 45°C, 47°C, 49°C, 52°C, 54°C, 56°C, 58°C or 60°C, etc., but is not limited to the listed values, and other values ​​not listed in this range are also applicable. The drying method is one of atmospheric pressure or vacuum drying at no more than 60°C, or freeze drying. Controlling the drying temperature in the present invention can effectively prevent excessive oxidation of the titanium powder surface, which is more conducive to controlling the oxygen content level of the final metallic titanium powder.

[0041] Preferably, in step (2), the second reducing agent and TiO x The mass ratio of the intermediate powder is 0.08~0.64:1, for example, it can be 0.08:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.6:1 or 0.64:1.

[0042] Preferably, the second reducing agent is in the form of powder, chips or granules, or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of powder and chips, a combination of granules and chips, and a combination of powder and granules.

[0043] Preferably, a second auxiliary agent is added during the second reduction.

[0044] Preferably, the second auxiliary agent includes any one of anhydrous MgCl2, MgCl2-CaCl2 eutectic salt, MgCl2-NaCl eutectic salt or MgCl2-KCl eutectic salt, or a combination of at least two thereof, wherein typical but non-limiting combinations are: a combination of MgCl2 and a MgCl2-CaCl2 eutectic salt, a combination of MgCl2 and a MgCl2-NaCl eutectic salt, a combination of MgCl2 and a MgCl2-KCl eutectic salt, a combination of a MgCl2-KCl eutectic salt and a MgCl2-NaCl eutectic salt, and a combination of a MgCl2-KCl eutectic salt and a MgCl2-CaCl2 eutectic salt.

[0045] Preferably, the second auxiliary agent is x The weight ratio of the intermediate powder is 0.05~3:1, for example, it can be 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 2.8:1 or 3.0:1.

[0046] Preferably, the temperature of the second reduction is 650-900°C, for example, 650°C, 677°C, 705°C, 732°C, 760°C, 787°C, 815°C, 842°C, 868°C or 900°C, etc., but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0047] Preferably, the second reduction time is 0.25 to 48 hours, for example, 0.25 hours, 1.0 hours, 5.0 hours, 10.5 hours, 15 hours, 21 hours, 28 hours, 35 hours, 40 hours or 48 hours, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0048] Preferably, the second reducing atmosphere includes a hydrogen-argon mixed atmosphere or a pure hydrogen atmosphere.

[0049] Preferably, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 5 to 100%, for example, it can be 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 80% or 100%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0050] Preferably, the method further comprises: between the first wet treatment and the second reduction, x The intermediate powder is sintered or melted and solidified.

[0051] The oxygen content on the surface of the titanium metal particles decreases as the specific surface area decreases. After the first reduction and the first wet treatment, the TiO obtained by the present invention x (0.167≤x≤0.5) The intermediate powder has a porous morphology, and sintering or melting and solidification treatment can obtain a denser intermediate, which is more conducive to controlling the surface oxygen content, and thus is conducive to controlling the oxygen content in the final titanium powder.

[0052] In the present invention, if the temperature of the first reduction is high, for example, reaching 1400° C., the reduction product is relatively dense and can be directly deoxidized to a lower oxygen content level without sintering or melting and solidification treatment.

[0053] Preferably, the temperature of the sintering treatment is 1000~1500°C, for example, it can be 1000°C, 1045°C, 1090°C, 1135°C, 1180°C, 1225°C, 1270°C, 1315°C, 1360°C, 1400°C or 1500°C, but is not limited to the listed values, and other values ​​not listed within this range are also applicable.

[0054] Preferably, the sintering treatment time is 0.25~24h, for example, it can be 0.25h, 0.5h, 1h, 2.8h, 5.5h, 8.1h, 10.8h, 13.4h, 16.1h, 18.7h, 21.4h or 24h, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0055] Preferably, the atmosphere of the sintering process includes vacuum or protective atmosphere.

[0056] Preferably, the protective atmosphere of the sintering treatment includes any one of hydrogen, argon or helium, or a combination of at least two of them, wherein typical but non-limiting combinations are: a combination of argon and hydrogen, a combination of argon and helium, a combination of hydrogen and helium, and a combination of argon, hydrogen and helium.

[0057] Preferably, the melting and solidification treatment method includes vacuum induction melting.

[0058] Preferably, the method further comprises: subjecting the metallic titanium powder obtained by the second wet treatment in step (2) to dehydrogenation treatment.

[0059] Hydrogen regulates the thermodynamic stability of the Ti-O solid solution. With the help of interstitial hydrogen, oxygen in the Ti-O solid solution can be efficiently removed by magnesium. However, the second deep reduction process also results in hydrogen in the titanium powder. When the application scenario of the titanium powder product has limitations on hydrogen content, dehydrogenation treatment is performed.

[0060] Preferably, the temperature of the dehydrogenation treatment is 500-1000°C.

[0061] Preferably, the atmosphere of the dehydrogenation treatment includes vacuum or protective atmosphere.

[0062] Preferably, the protective atmosphere of the dehydrogenation treatment includes argon and / or helium.

[0063] As a preferred technical solution of the present invention, the method comprises the following steps:

[0064] (1) mixing a calcium-containing titanium source, a first reducing agent, and a first auxiliary agent, wherein the molar ratio of calcium in the calcium-containing titanium source to the first reducing agent is 0.6-2:1, the molar ratio of the first reducing agent to titanium in the calcium-containing titanium source is 1-1.33:1, and the weight ratio of the first auxiliary agent to titanium in the calcium-containing titanium source as TiO2 is 0.05-3:1, and sequentially subjecting the mixture to a first reduction at 700-1400°C for 0.25-24h in vacuum or protective atmosphere to obtain a first reduced product;

[0065] The product of the first reduction is slurried with water and / or an acid solution with a pH value of ≥0.5, with a liquid-solid ratio of 1-100:1 mL / g, to obtain a slurry; the slurry is successively pH-adjusted, wherein the pH of the slurry is controlled to be ≥0.8 during the pH adjustment, and the pH of the slurry after pH adjustment is stabilized at 1.5-3.0, and solid-liquid separation is performed, and the obtained solid phase is successively washed at 0-60°C and dried at ≤60°C to obtain TiO x Intermediate powder, where 0.167≤x≤0.5;

[0066] (2) TiO x The intermediate powder is first sintered at 1000-1500°C for 0.25-24h under vacuum or protective atmosphere or the TiO x The intermediate powder is first subjected to electromagnetic induction melting treatment, and then subjected to a second reduction with a second reducing agent and a second auxiliary agent in a hydrogen-argon mixed atmosphere or a pure hydrogen atmosphere at 650-900°C for 0.25-48h. x The mass ratio of the intermediate powder is 0.08~0.64:1, the second auxiliary agent and TiO x The weight ratio of the intermediate powder is 0.05~3:1, and the second reduced product is obtained;

[0067] The product of the second reduction is slurried with water and / or an acid solution with a pH ≥ 0.5, with a liquid-solid ratio of 1-100:1 mL / g, to obtain a slurry; the slurry is successively pH-adjusted, and the pH of the slurry is controlled to be ≥ 0.8 during the pH adjustment. The pH of the slurry after pH adjustment is stabilized at 1.5-3.0, and solid-liquid separation is performed. The obtained solid phase is successively washed at 0-60°C and dried at ≤ 60°C to obtain metallic titanium powder.

[0068] The present invention has no particular limitation on the solid-liquid separation in the above process. Any device and method for solid-liquid separation known to those skilled in the art can be used, and can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0069] The present invention has no particular limitation on the drying process. Any drying device and method known to those skilled in the art can be used. The drying method can also be adjusted according to the actual process. For example, it can be air drying, vacuum drying, oven drying or freeze drying, or a combination of different methods.

[0070] Compared with the prior art, the present invention has at least the following beneficial effects:

[0071] (1) The method for preparing titanium powder by aluminum-magnesium stepwise reduction provided by the present invention is to first reduce the TiO2 raw material with aluminum, and then obtain TiO2 by the first wet treatment of the reduction product. x (0.167≤x≤0.5) intermediate powder, which is then subjected to deep reduction with a second reducing agent, magnesium, and a second wet process to obtain metallic titanium powder. This method can reduce the cost of the reducing agent by up to 183,380 yuan per ton of metallic titanium powder, saving more than 54% of the reducing agent cost compared to the full magnesium reduction process of oxygen in titanium dioxide;

[0072] (2) The method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction provided by the present invention obtains an easily acid-soluble aluminum oxide-enriched by-product phase by adding CaO and a first auxiliary agent and controlling an appropriate ratio. The separation of the titanium product and the by-product phase is more thorough, and the temperature requirement for the reduction process is greatly reduced;

[0073] (3) The method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction provided by the present invention can ensure that the oxygen content in the prepared titanium powder is low, the oxygen content is less than 0.5wt%, and under optimal conditions, the oxygen content is ≤0.28wt%. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 It is a schematic flow chart of a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction provided in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0075] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0076] The present invention is further described in detail below. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0077] As a specific embodiment of the present invention, a method for preparing titanium powder by stepwise reduction of aluminum and magnesium is provided. The flow chart of the method is as follows: Figure 1 As shown, the specific steps include:

[0078] (1) mixing a calcium titanium source (calcined or uncalcined titanium dioxide and calcium oxide), a first reducing agent, and a first auxiliary agent, performing a first reduction, and obtaining a first reduced product;

[0079] The product of the first reduction is subjected to a first wet treatment, wherein the first wet treatment comprises slurrying the product of the first reduction with water and / or an acid solution with a pH value of ≥ 0.5 to obtain a slurry; the slurry is successively pH-adjusted and subjected to solid-liquid separation, and the obtained solid phase is successively washed and dried to obtain TiO x Intermediate powder, where 0.167≤x≤0.5;

[0080] (2) TiO x The intermediate powder is first sintered or subjected to electromagnetic induction melting (the dotted line in the figure indicates that this is an optional step), and then subjected to a second reduction with a second reducing agent and a second auxiliary agent to obtain a second reduced product;

[0081] The second reduced product is subjected to a second wet treatment, which includes slurrying the second reduced product with water and / or an acid solution with a pH ≥ 0.5 to obtain a slurry; the slurry is successively pH-adjusted and solid-liquid separated, and the obtained solid phase is successively washed and dried. Optionally, the dried product is subjected to a dehydrogenation treatment to obtain metallic titanium powder.

[0082] Example 1

[0083] This embodiment provides a method for preparing metallic titanium powder by stepwise reduction of aluminum and magnesium, the method comprising the following steps:

[0084] (1) mixing a calcium titanium source (a mixture of calcium oxide and calcined titanium dioxide), aluminum powder and a CaCl2-KCl eutectic salt, wherein the molar ratio of calcium in the calcium titanium source to aluminum powder is 1.0:1, the molar ratio of aluminum powder to titanium in the calcium titanium source is 1.11:1, and the weight ratio of the CaCl2-KCl eutectic salt to titanium in the calcium titanium source as TiO2 is 1.5:1, and subjecting the mixture to a first reduction at 1200°C for 2h in a helium atmosphere to obtain a first reduced product;

[0085] The product of the first reduction was slurried with hydrochloric acid at a pH of 1.0, with a liquid-solid ratio of 50:1 mL / g, to obtain a slurry; the slurry was successively pH-adjusted, and the pH of the slurry was controlled to be ≥ 0.8 during the pH adjustment. The pH of the slurry after pH adjustment was stabilized at 2.2, and filtered. The obtained solid phase was successively washed with water at 50°C and dried at 45°C to obtain TiO x middle powder;

[0086] (2) TiO x The intermediate powder was first sintered at 1400°C for 1h under vacuum conditions, and then reduced at 850°C for 2h with magnesium powder and MgCl2 molten salt in a pure hydrogen atmosphere. x The mass ratio of the intermediate powder is 0.3:1, MgCl2-KCl eutectic salt and TiO x The weight ratio of the intermediate powder is 2.0:1, and the second reduced product is obtained;

[0087] The product of the second reduction was slurried with hydrochloric acid solution at a pH of 1.5 at a liquid-to-solid ratio of 3:1 mL / g to obtain a slurry; the slurry was successively pH-adjusted, and the pH of the slurry was controlled to be ≥0.8 during the pH adjustment. The pH of the slurry after pH adjustment was stabilized at 1.5, and filtered. The obtained solid phase was successively washed with water at 40°C and dried at 40°C. The dried product was dehydrogenated at 800°C under an argon atmosphere to obtain metallic titanium powder.

[0088] Example 2

[0089] This embodiment provides a method for preparing metallic titanium powder by stepwise reduction of aluminum and magnesium, the method comprising the following steps:

[0090] (1) mixing a calcium titanium source (a mixture of a calcined product obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio of CaTiO3 and calcium oxide), aluminum powder, and anhydrous CaCl2, wherein the molar ratio of calcium in the calcium titanium source to aluminum powder is 2.0:1, the molar ratio of aluminum powder to titanium in the calcium titanium source is 1.22:1, and the weight ratio of anhydrous CaCl2 to titanium in the calcium titanium source as TiO2 is 0.05:1, and performing a first reduction at 1400°C for 0.25h under vacuum conditions to obtain a first reduced product;

[0091] The product of the first reduction was slurried with hydrochloric acid at a pH of 0.5, with a liquid-solid ratio of 100:1 mL / g, to obtain a slurry; the slurry was successively pH-adjusted, and the pH of the slurry was controlled to be ≥1.0 during the pH adjustment. The pH of the slurry after pH adjustment was stabilized at 3.0, and filtered. The obtained solid phase was successively washed with water at 40°C and dried at 50°C to obtain TiO x middle powder;

[0092] (2) TiO xThe intermediate powder was first subjected to electromagnetic induction melting treatment at 1600°C in an argon atmosphere for 0.25h, and then subjected to a second reduction treatment at 900°C in a hydrogen-argon mixed atmosphere (hydrogen volume fraction of 85%) for 0.25h. x The mass ratio of the intermediate powder is 0.2:1, MgCl2-CaCl2 eutectic salt and TiO x The weight ratio of the intermediate powder is 3.0:1, and the second reduced product is obtained;

[0093] The product of the second reduction is slurried with hydrochloric acid solution with a pH of 1.0, and the liquid-solid ratio is 100:1 mL / g to obtain a slurry; the slurry is successively pH-adjusted, and the pH of the slurry is controlled to be ≥1.0 during the pH adjustment. The pH of the slurry after pH adjustment is stabilized at 2.0, and is filtered. The obtained solid phase is successively washed with water at 30°C and dried at 45°C. The dried product is dehydrogenated at 1000°C under vacuum conditions to obtain metallic titanium powder.

[0094] Example 3

[0095] This embodiment provides a method for preparing metallic titanium powder by stepwise reduction of aluminum and magnesium, the method comprising the following steps:

[0096] (1) mixing a calcium titanium source (a mixture of a calcined product obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio of CaTiO3 and calcium oxide), aluminum powder, and a CaCl2-NaCl eutectic salt, wherein the molar ratio of calcium in the calcium titanium source to aluminum powder is 0.6:1, the molar ratio of aluminum powder to titanium in the calcium titanium source is 1.33:1, and the weight ratio of the CaCl2-NaCl eutectic salt to titanium in the calcium titanium source as TiO2 is 3.0:1, and sequentially subjecting the mixture to a first reduction at 1100°C for 4 hours in a helium atmosphere to obtain a first reduced product;

[0097] The product of the first reduction was slurried with hydrochloric acid at a pH of 1.0, with a liquid-solid ratio of 20:1 mL / g, to obtain a slurry; the slurry was successively pH-adjusted, and the pH of the slurry was controlled to be ≥1.2 during the pH adjustment. The pH of the slurry after pH adjustment was stabilized at 2.5, and filtered. The obtained solid phase was successively washed with water at 20°C and dried at 60°C to obtain TiO x middle powder;

[0098] (2) TiO x The intermediate powder was first sintered at 1200°C for 12 h in a hydrogen atmosphere, and then subjected to a second reduction treatment at 650°C for 48 h in a hydrogen-argon mixed atmosphere (hydrogen volume fraction is 5%). x The mass ratio of the intermediate powder is 0.08:1, MgCl2-CaCl2 eutectic salt and TiO xThe weight ratio of the intermediate powder is 3.0:1, and the second reduced product is obtained;

[0099] The product of the second reduction is slurried with hydrochloric acid solution with a pH of 1.0, and the liquid-solid ratio is 80:1 mL / g to obtain a slurry; the slurry is successively pH-adjusted, and the pH of the slurry is controlled to be ≥1.0 during the pH adjustment. The pH of the slurry after pH adjustment is stabilized at 2.5, and is filtered. The obtained solid phase is successively washed with water at 45°C and dried at 40°C. The dried product is dehydrogenated at 500°C under vacuum to obtain metallic titanium powder.

[0100] Example 4

[0101] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of embodiment 1 except that the CaCl2-KCl eutectic salt is replaced by AlCl3-KCl eutectic salt in step (1).

[0102] Example 5

[0103] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of Example 1, except that in step (1), the weight ratio of the CaCl2-KCl eutectic salt to the titanium in the calcium-titanium source calculated as TiO2 is 3.5:1.

[0104] Example 6

[0105] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of Example 1, except that in step (1), the weight ratio of the CaCl2-KCl eutectic salt to the titanium in the calcium-titanium source calculated as TiO2 is 0.01:1.

[0106] Example 7

[0107] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of embodiment 1 except that the MgCl2 molten salt is replaced by CaCl2 molten salt in step (2).

[0108] Example 8

[0109] This embodiment provides a method for preparing metallic titanium powder by stepwise reduction of aluminum and magnesium. The method is the same as that of embodiment 1 except that the pure hydrogen atmosphere in step (2) is replaced by a helium atmosphere.

[0110] Example 9

[0111] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of embodiment 1 except that the molar ratio of calcium to aluminum powder in the calcium-titanium source in step (1) is 0.4:1.

[0112] Example 10

[0113] This embodiment provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as that of embodiment 1 except that the molar ratio of calcium to aluminum powder in the calcium-titanium source in step (1) is 3:1.

[0114] Example 11

[0115] This embodiment provides a method for preparing titanium powder by stepwise reduction of aluminum and magnesium. The method is the same as that of embodiment 1 except that the sintering step (2) is not performed, that is, TiO x The intermediate powder is subjected to a second reduction and the parameters and conditions of the second reduction degree are the same as those in Example 1.

[0116] Comparative Example 1

[0117] This comparative example provides a method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction. The method is the same as Example 1 except that the calcium-containing titanium source in step (1) is replaced by a non-calcined titanium source, that is, calcined titanium dioxide is directly used.

[0118] TiO was measured by inductively coupled plasma atomic emission spectrometry followed by subtraction and X-ray diffraction analysis. x The value of x in the intermediate powder is obtained, and the oxygen content of the final metal titanium powder is measured using an ONH analyzer. The cost of the reducing agent consumed for each ton of metal titanium powder produced is calculated, where the average market price of magnesium is RMB 40,000 per ton and that of aluminum is RMB 20,000 per ton.

[0119] The test and calculation results of the above embodiments and comparative examples are shown in Tables 1 and 2.

[0120] Table 1

[0121]

[0122] Table 2

[0123]

[0124] “ / ” in the table indicates that there is no relevant data.

[0125] From Tables 1 and 2, we can see the following points:

[0126] (1) Based on Examples 1 to 3, it can be seen that the method for preparing titanium metal powder by aluminum-magnesium stepwise reduction provided by the present invention can produce titanium metal powder with an oxygen content of ≤0.28%, and the cost of the reducing agent can be reduced by RMB 183,380 per ton of titanium metal powder, which is more than 54% lower than the original magnesium reduction process.

[0127] (2) From Example 1 and Examples 5-6, it can be seen that the present invention can reduce the waste of the first auxiliary agent and avoid the formation of a weakly acid-insoluble aluminum phase by controlling the weight ratio of the first auxiliary agent to the titanium in the calcium-containing titanium source in terms of TiO2 within a specific range, which is beneficial to the subsequent wet separation.

[0128] (3) From Example 1 and Examples 7-8, it can be seen that the magnesium reduction in Example 1 uses a second auxiliary agent containing magnesium and is carried out in a hydrogen-containing atmosphere. Compared with Example 7 using CaCl2 molten salt as the second auxiliary agent and Example 8 using a hydrogen-free atmosphere, the oxygen content of the final metal titanium powder in Example 1 is only 0.28wt%, while the oxygen contents in Examples 7-8 are as high as 0.88wt% and 2.45wt%, respectively. This shows that the present invention improves the reduction effect and reduces the oxygen content in the metal titanium powder by carrying out the magnesium reduction step in a hydrogen-containing atmosphere and using a second auxiliary agent containing magnesium;

[0129] (4) From Example 1, Examples 9-10, and Comparative Example 1, it can be seen that the molar ratio of calcium to aluminum powder in the calcium titanium source in Example 1 is 1.0:1, compared with 0.4:1 and 3:1 in Examples 9-10, respectively. In Comparative Example 1, which does not contain a calcium source, the first reduced product in Example 1 can be wet-processed to obtain TiO with x=0.5. x The intermediate powder, while in Comparative Example 1 and Example 9, due to the formation of weakly acid-insoluble aluminum phase, subsequent wet separation is difficult, and in Example 10, there is excess CaO ineffective consumption. This shows that the present invention can effectively ensure that the reduction by-products are soluble in weak acid by controlling the molar ratio of calcium to aluminum powder within a specific range;

[0130] (5) From Example 1 and Example 11, it can be seen that Example 11 does not perform the sintering step, and it is difficult to form a dense structure, resulting in the oxygen content in the final metal titanium powder being as high as 1.75wt%. This shows that the present invention preferably uses sintering or electromagnetic induction melting treatment to further reduce the oxygen content in the metal titanium powder.

[0131] While the present invention is described through the above-described embodiments to illustrate the detailed structural features of the present invention, the present invention is not limited to these detailed structural features, nor does it necessarily rely on these detailed structural features for implementation. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for selected components, additions of auxiliary components, and selection of specific embodiments, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing metallic titanium powder by aluminum-magnesium stepwise reduction, characterized in that: The method comprises the following steps: (1) Mixing a calcium titanium source, a first reducing agent and a first auxiliary agent, and sequentially performing a first reduction and a first wet treatment to obtain TiO x intermediate powder, wherein 0.167≤x≤0.5, and the first reducing agent comprises aluminum; (2) The TiO x The intermediate powder is subjected to a second reduction with a second reducing agent, and then subjected to a second wet process to obtain metallic titanium powder, wherein the second reducing agent includes magnesium; The molar ratio of calcium in the calcium-titanium source to the first reducing agent is 0.6 to 2:1; The molar ratio of the first reducing agent to titanium in the calcium-containing titanium source is 1 to 1.33:1; In step (1), the first auxiliary agent includes any one of anhydrous CaCl2, KCl, NaCl, CaCl2-KCl eutectic salt, CaCl2-NaCl eutectic salt, CaCl2-LiCl eutectic salt, KCl-NaCl eutectic salt, LiCl-NaCl eutectic salt, LiCl-KCl eutectic salt, AlCl3-KCl eutectic salt or AlCl3-NaCl eutectic salt, or a combination of at least two thereof; The weight ratio of the first auxiliary agent to the titanium in the calcium titanium source calculated as TiO2 is 0.05 to 3:1; The first wet treatment in step (1) includes: slurrying the product of the first reduction with water and / or acid solution to obtain slurry; the slurry is successively pH-adjusted and solid-liquid separated, and the obtained solid phase is successively washed and dried to obtain TiO x middle powder; In step (2), the second reducing agent and TiO x The mass ratio of the intermediate powder is 0.08~0.64:

1.

2. The method according to claim 1, characterized in that The calcium-containing titanium source in step (1) includes any one or a combination of at least two of a first titanium source, a second titanium source, a third titanium source, or a fourth titanium source. The first titanium source is a mixture of titanium dioxide and calcium oxide, the second titanium source is a mixture of calcium oxide and calcined titanium dioxide, the third titanium source is a mixture of a calcined product obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio of CaTiO3 and calcium oxide, and the fourth titanium source is a mixture obtained by mixing calcium oxide and titanium dioxide in a stoichiometric ratio exceeding CaTiO3 and calcining.

3. The method according to claim 1, characterized in that The calcination temperature of the second titanium source, the third titanium source or the fourth titanium source is independently 1000-1400°C.

4. The method according to claim 1, wherein The first reducing agent may be in a powdery, crumbly or granular form, or in a combination of at least two of the forms.

5. The method according to claim 1, wherein The temperature of the first reduction in step (1) is 700-1400°C; The first reduction time is 0.25~24h; The first reducing atmosphere includes vacuum or protective atmosphere; The first reducing protective atmosphere includes any one of argon, hydrogen or helium, or a combination of at least two of them.

6. The method according to claim 1, characterized in that The second wet treatment in step (2) includes: the product of the second reduction is slurried with water and / or acid solution to obtain a slurry; the slurry is successively pH-adjusted and solid-liquid separated, and the obtained solid phase is successively washed and dried to obtain metallic titanium powder.

7. The method according to claim 6, characterized in that The pH of the acid solution in the first wet treatment and the second wet treatment is independently ≥ 0.5; The liquid-to-solid ratio of the slurry in the first wet treatment and the second wet treatment is independently 1 to 100:1 mL / g; The acid used for pH adjustment in the first wet treatment and the second wet treatment is independently hydrochloric acid; The pH of the slurry is independently controlled to be ≥ 0.8 during the pH adjustment in the first wet treatment and the second wet treatment; The pH of the slurry after pH adjustment in the first wet treatment and the second wet treatment is independently 1.5 to 3.0; The washing temperatures in the first wet treatment and the second wet treatment are each independently 0 to 60°C; The drying temperatures in the first wet treatment and the second wet treatment are each independently ≤ 60°C.

8. The method according to claim 1, characterized in that The second reducing agent may be in a powdery, crumbly or granular form, or in a combination of at least two of the forms.

9. The method according to claim 1, characterized in that Adding a second auxiliary agent during the second reduction; The second auxiliary agent includes any one or a combination of at least two of anhydrous MgCl2, MgCl2-CaCl2 eutectic salt, MgCl2-NaCl eutectic salt or MgCl2-KCl eutectic salt; The second auxiliary agent and TiO x The weight ratio of the intermediate powder is 0.05~3:

1.

10. The method according to claim 1, characterized in that The temperature of the second reduction is 650-900° C.; The second reduction time is 0.25~48h; The second reducing atmosphere includes a hydrogen-argon mixed atmosphere or a pure hydrogen atmosphere; The volume fraction of hydrogen in the hydrogen-argon mixed atmosphere is 5-100%.

11. The method according to claim 1, wherein The method further comprises: between the first wet treatment and the second reduction, x The intermediate powder is sintered or melted and solidified.

12. The method according to claim 11, characterized in that The sintering temperature is 1000-1500°C; The sintering time is 0.25~24h; The sintering atmosphere includes vacuum or protective atmosphere; The protective atmosphere of the sintering treatment includes any one of hydrogen, argon or helium, or a combination of at least two of them; The melting and solidification treatment method includes electromagnetic induction melting.

13. The method according to claim 1, wherein The method further comprises: subjecting the metallic titanium powder obtained by the second wet treatment in step (2) to a dehydrogenation treatment.

14. The method according to claim 13, characterized in that The temperature of the dehydrogenation treatment is 500-1000°C; The atmosphere of the dehydrogenation treatment includes vacuum or protective atmosphere; The protective atmosphere of the dehydrogenation treatment includes argon and / or helium.

15. The method according to claim 1, wherein The method comprises the following steps: (1) mixing a calcium-containing titanium source, a first reducing agent, and a first auxiliary agent, wherein the molar ratio of calcium in the calcium-containing titanium source to the first reducing agent is 0.6-2:1, the molar ratio of the first reducing agent to titanium in the calcium-containing titanium source is 1-1.33:1, and the weight ratio of the first auxiliary agent to titanium in the calcium-containing titanium source as TiO2 is 0.05-3:1, and sequentially subjecting the mixture to a first reduction at 700-1400°C for 0.25-24h in vacuum or protective atmosphere to obtain a first reduced product; The product of the first reduction is slurried with water and / or an acid solution with a pH value of ≥0.5, with a liquid-solid ratio of 1-100:1 mL / g, to obtain a slurry; the slurry is successively pH-adjusted, wherein the pH of the slurry is controlled to be ≥0.8 during the pH adjustment, and the pH of the slurry after pH adjustment is stabilized at 1.5-3.0, and solid-liquid separation is performed, and the obtained solid phase is successively washed at 0-60°C and dried at ≤60°C to obtain TiO x Intermediate powder, where 0.167≤x≤0.5; (2) The TiO x The intermediate powder is first sintered at 1000-1500°C for 0.25-24h under vacuum or protective atmosphere or the TiO x The intermediate powder is first subjected to electromagnetic induction melting treatment, and then subjected to a second reduction with a second reducing agent and a second auxiliary agent in a hydrogen-argon mixed atmosphere or a pure hydrogen atmosphere at 650-900°C for 0.25-48h. x The mass ratio of the intermediate powder is 0.08~0.64:1, the second auxiliary agent and TiO x The weight ratio of the intermediate powder is 0.05~3:1, and the second reduced product is obtained; The product of the second reduction is slurried with water and / or an acid solution with a pH ≥ 0.5, with a liquid-solid ratio of 1-100:1 mL / g, to obtain a slurry; the slurry is successively pH-adjusted, and the pH of the slurry is controlled to be ≥ 0.8 during the pH adjustment. The pH of the slurry after pH adjustment is stabilized at 1.5-3.0, and solid-liquid separation is performed. The obtained solid phase is successively washed at 0-60°C and dried at ≤ 60°C to obtain metallic titanium powder.

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