CN115921884B - A method for preparing titanium powder by metal thermal reduction of titanium dioxide - Google Patents

Abstract

The invention relates to a method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide, which is carried out in steps at a low temperature section and a high temperature section respectively: firstly, in a low-temperature section, under the conditions that the pressure is less than 30Pa and the temperature is 800-1000 ℃, the bottom of a graphite crucible mainly reacts with calcium carbide and magnesium oxide to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; after the magnesium oxide is consumed, the atmosphere furnace is heated to 1100-1300 ℃ in the high-temperature section reduction process, the stage mainly comprises the steps of reacting excessive calcium carbide with calcium oxide to generate calcium vapor, and further reducing the product obtained in the low-temperature section by rising the calcium vapor to finally obtain the metallic titanium. The invention takes titanium dioxide as raw material, and prepares the metallic titanium through a direct thermal reduction method, compared with the Kroll method used in the industry at present, the invention shortens the reaction flow, simplifies the reaction steps, and has easy control of the reduction process and simple operation. Meanwhile, a temperature-division reduction method is adopted, so that the preparation cost is reduced, and the energy is saved.

Description

A method for preparing titanium powder by metal thermal reduction of titanium dioxide

Technical Field

The invention belongs to the technical field of metallurgy and metal material preparation, and specifically relates to a method for preparing metallic titanium powder by metal thermal reduction of titanium dioxide.

Background Art

As an important strategic metal resource, titanium is widely used in high-tech fields such as semiconductor integrated circuits, military industry, aerospace, 3D printing, etc. With the continuous mergers, reorganizations and expansions of large domestic titanium sponge manufacturers, my country's titanium sponge production capacity has increased year by year. In 2020, my country's titanium sponge production capacity reached 177,000 tons, an increase of 12% over the previous year. The Kroll method is currently the main process for industrial production of titanium metal, but this process is a semi-continuous process with problems such as long production process, high cost, and low product purity, which restricts the large-scale development of the titanium smelting industry. Therefore, the development of short-process, low-cost new titanium metallurgical technologies is of great significance to the green and sustainable development of my country's titanium industry.

The Kroll method is a typical representative of the metal thermal reduction method and is also the main method for producing titanium metal in industry at present. This process first converts the titanium-rich material into titanium tetrachloride, and then reduces it with magnesium metal to produce sponge titanium. The product has a high impurity content, such as 0.3% to 0.9% of oxygen, carbon and hydrogen, which affects the strength, ductility and impact toughness of the product, and limits the application of sponge titanium in high-end titanium alloys. Compared with the complex process of the Kroll method, the direct reduction of titanium dioxide as a raw material to prepare titanium metal has become one of the important directions for the research and development of short-process and low-cost titanium smelting technology. CN102921953A discloses a method for preparing titanium metal powder using aluminum powder, calcium oxide and titanium dioxide as raw materials. This method uses calcium vapor generated by the reaction of aluminum powder and calcium oxide to directly reduce titanium dioxide, eliminating the condensation and remelting gasification process of calcium, shortening the reaction process and saving energy. CN101628337A discloses a method for producing titanium metal powder using magnesium vapor to reduce titanium dioxide. In the above technology, the reduction of titanium dioxide by calcium vapor requires a higher temperature, but magnesium vapor has a lower reducing ability than calcium vapor, so the oxygen content in the metal calcium product obtained by reduction is higher. Research on more energy-saving and efficient methods for preparing titanium metal is of great significance to the short process, low-cost smelting and high-value utilization of titanium materials.

Summary of the invention

The invention provides a method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide, and the purpose of the method is to realize direct reduction of titanium dioxide to prepare metallic titanium powder with low impurity content.

The present invention is achieved through the following technical solutions:

A method for preparing titanium powder by metal thermal reduction of titanium dioxide, wherein titanium dioxide is used as a raw material, and the reduction steps successively include magnesium vapor vacuum thermal reduction and calcium vapor vacuum thermal reduction, and specifically include the following steps:

(1) titanium dioxide with a particle size range of 100 to 1000 mesh and anhydrous calcium chloride are uniformly mixed in a mass ratio of 1:1 to 3:1, and pressed into a block I at a pressure of 10 MPa;

(2) Magnesium oxide, calcium oxide and calcium carbide with a particle size range of 100 to 1000 mesh are uniformly mixed in a mass ratio of 1:1:1 to 1:1:2, and pressed into a block II at a pressure of 5 to 10 MPa;

(3) placing the block II prepared in step (2) in a molybdenum boat and placing it in the lower layer of a graphite crucible, and placing the block I prepared in step (1) in the upper layer of the graphite crucible, separating the block I and the block II with a porous molybdenum plate, and covering the graphite crucible with a graphite cover;

(4) The graphite crucible obtained in step (3) is heated to 800-1000° C. at a pressure of less than 30 Pa and kept warm for 180-360 min. At this time, the bottom of the graphite crucible is mainly composed of calcium carbide and magnesium oxide reacting to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; then the temperature is raised to 1100-1300° C. and kept warm for 180-360 min. In this stage, the remaining calcium carbide and calcium oxide react to generate calcium vapor, and the calcium vapor rises to further reduce the product of the previous stage, and a reduced bulk material is obtained; after the first reduction process in this step, titanium mainly exists in the form of low-valent titanium oxide and a small amount of metallic titanium; after the second reduction process, titanium mainly exists in the form of metallic titanium;

(5) the block material obtained in step (4) is stirred and leached in a hydrochloric acid solution with a pH of 0.5 to 1 for 4 to 8 hours, wherein the pH of the solution is adjusted to be always within the above range by dropping 1 mol/L hydrochloric acid solution during the stirring process, and the stirring speed is controlled to be 100 to 300 r/min;

(6) The material obtained in step (5) is filtered and separated to obtain a leachate and a solid, and the solid is repeatedly washed with deionized water and anhydrous ethanol until the filtrate is neutral, and the filter cake is dried at 40 to 80° C. for 8 to 16 hours to obtain metallic titanium powder.

The size of the block I in step (1) is Φ15×20～Φ20×20mm.

The size of block II in step (2) is Φ15×10～Φ20×10mm.

The heating rate in step (4) is 10°C/min.

The liquid-to-solid ratio during stirring and leaching in step (5) is greater than 15:1.

Compared with the prior art, the present invention has the following advantages:

(1) Short process. The present invention uses titanium dioxide as a raw material and directly thermally reduces titanium dioxide to prepare titanium sponge; while the Kroll method currently used in industry uses titanium dioxide as a raw material, chlorinates to prepare titanium tetrachloride, and then metal thermally reduces titanium tetrachloride to obtain titanium sponge. Therefore, compared with the Kroll method, the present method simplifies the reaction steps and shortens the reaction process, and the reduction process is easy to control and simple to operate.

(2) High product quality. The present invention proposes a method for preparing metallic titanium by reducing titanium dioxide with magnesium and calcium in a vacuum atmosphere. The reduction process is easy to control, and the metallic titanium powder obtained by the two-step reduction method has a low content of impurities such as oxygen and nitrogen, which is of great significance for the high-value utilization of titanium materials.

(3) Low cost. In the present invention, the reducing agents metal magnesium and metal calcium are generated synchronously by the reaction of calcium carbide with magnesium oxide and calcium oxide, respectively. At the same time, the vacuum reduction process is carried out in steps at a low temperature section and a high temperature section, respectively. While achieving product quality, it also reduces the preparation cost of metal titanium and saves energy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the process flow of the present invention.

DETAILED DESCRIPTION

The present invention will be further described below in conjunction with the embodiments.

Example 1

(1) titanium dioxide with a particle size range of 100 to 200 mesh and anhydrous calcium chloride are uniformly mixed in a mass ratio of 2:1, and pressed into a block I with a size of Φ15×20 mm at a pressure of 10 MPa;

(2) Magnesium oxide, calcium oxide and calcium carbide with a particle size range of 100 to 200 mesh are uniformly mixed in a mass ratio of 1:1:1, and pressed into a block II with a size of Φ15×10 mm at a pressure of 5 MPa;

(3) placing the block II prepared in step (2) in a molybdenum boat and placing it in the lower layer of a graphite crucible, and placing the block I prepared in step (1) in the upper layer of the graphite crucible, separating the block I and the block II with a porous molybdenum plate, and covering the graphite crucible with a graphite cover;

(4) placing the graphite crucible obtained in step (3) in a vacuum atmosphere furnace, and performing the vacuum thermal reduction process in a low temperature section and a high temperature section in steps: first, at a pressure of less than 30 Pa, heating the atmosphere furnace at a heating rate of 10°C/min to 800°C, and keeping the temperature at the reaction temperature for 360 min. At this time, the bottom of the graphite crucible is mainly calcium carbide reacting with magnesium oxide to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; then heating the atmosphere furnace at a heating rate of 10°C/min to 1100°C, and keeping the temperature at the same temperature for 360 min. In this stage, the remaining calcium carbide reacts with calcium oxide to generate calcium vapor, and the calcium vapor rises to further reduce the product of the previous stage, and obtains a reduced bulk material; after the first reduction process in this step, titanium mainly exists in the form of low-valent titanium oxide and a small amount of metallic titanium; after the second reduction process, titanium mainly exists in the form of metallic titanium;

(5) the block material obtained in step (4) was stirred and leached in a hydrochloric acid solution with a pH of 0.5 for 6 hours, with a liquid-to-solid ratio of 16:1, wherein the pH of the solution was adjusted to be always within the above range by dropping 1 mol/L hydrochloric acid solution during the stirring process, and the stirring speed was controlled to be 200 r/min;

(6) The material obtained in step (5) is filtered and separated to obtain a leachate and a solid, and the solid is repeatedly washed with deionized water and anhydrous ethanol until the filtrate is neutral. The filter cake is placed in a vacuum drying oven and dried at 60° C. for 12 h to obtain metallic titanium powder.

Example 2

(1) titanium dioxide with a particle size range of 300 to 500 mesh and anhydrous calcium chloride are uniformly mixed in a mass ratio of 1:1, and pressed into a block I with a size of Φ20×20 mm at a pressure of 10 MPa;

(2) Magnesium oxide, calcium oxide and calcium carbide with a particle size range of 300 to 500 mesh are uniformly mixed in a mass ratio of 1:1:1, and pressed into a block II with a size of Φ20×10 mm at a pressure of 6 MPa;

(3) placing the block II prepared in step (2) in a molybdenum boat and placing it in the lower layer of a graphite crucible, and placing the block I prepared in step (1) in the upper layer of the graphite crucible, separating the block I and the block II with a porous molybdenum plate, and covering the graphite crucible with a graphite cover;

(4) placing the graphite crucible obtained in step (3) in a vacuum atmosphere furnace, and performing the vacuum thermal reduction process in a low temperature section and a high temperature section in steps: first, at a pressure of less than 30 Pa, heating the atmosphere furnace at a heating rate of 10°C/min to 900°C, and keeping the temperature at the reaction temperature for 240 min. At this time, the bottom of the graphite crucible is mainly calcium carbide reacting with magnesium oxide to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; then heating the atmosphere furnace at a heating rate of 10°C/min to 1200°C, and keeping the temperature at the same temperature for 240 min. In this stage, the remaining calcium carbide reacts with calcium oxide to generate calcium vapor, and the calcium vapor rises to further reduce the product of the previous stage, and obtains a reduced bulk material; after the first reduction process in this step, titanium mainly exists in the form of low-valent titanium oxide and a small amount of metallic titanium; after the second reduction process, titanium mainly exists in the form of metallic titanium;

(5) the block material obtained in step (4) was stirred and leached in a hydrochloric acid solution with a pH of 1 for 8 h, with a liquid-to-solid ratio of 18:1, wherein the pH of the solution was adjusted to be always within the above range by dropping 1 mol/L hydrochloric acid solution during the stirring process, and the stirring speed was controlled to be 300 r/min;

(6) The material obtained in step (5) is filtered and separated to obtain a leachate and a solid, and the solid is repeatedly washed with deionized water and anhydrous ethanol until the filtrate is neutral. The filter cake is placed in a vacuum drying oven and dried at 80° C. for 8 h to obtain metallic titanium powder.

Example 3

(1) titanium dioxide with a particle size range of 800-1000 mesh and anhydrous calcium chloride are uniformly mixed in a mass ratio of 3:1, and pressed into a block I with a size of Φ18×18 mm at a pressure of 10 MPa;

(2) Magnesium oxide, calcium oxide and calcium carbide with a particle size range of 800 to 1000 mesh are uniformly mixed in a mass ratio of 1:1:2, and pressed into a block II with a size of Φ18×18 mm at a pressure of 5 MPa;

(3) placing the block II prepared in step (2) in a molybdenum boat and placing it in the lower layer of a graphite crucible, and placing the block I prepared in step (1) in the upper layer of the graphite crucible, separating the block I and the block II with a porous molybdenum plate, and covering the graphite crucible with a graphite cover;

(4) placing the graphite crucible obtained in step (3) in a vacuum atmosphere furnace, and performing the vacuum thermal reduction process in a low temperature section and a high temperature section in steps: first, at a pressure of less than 30 Pa, heating the atmosphere furnace at a heating rate of 10°C/min to 1000°C, and keeping the temperature at the reaction temperature for 180 min. At this time, the bottom of the graphite crucible is mainly calcium carbide reacting with magnesium oxide to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; then heating the atmosphere furnace at a heating rate of 10°C/min to 1300°C, and keeping the temperature at the same temperature for 180 min. In this stage, the remaining calcium carbide reacts with calcium oxide to generate calcium vapor, and the calcium vapor rises to further reduce the product of the previous stage, and obtains a reduced bulk material; after the first reduction process in this step, titanium mainly exists in the form of low-valent titanium oxide and a small amount of metallic titanium; after the second reduction process, titanium mainly exists in the form of metallic titanium;

(5) the block material obtained in step (4) was stirred and leached in a hydrochloric acid solution with a pH of 1 for 4 hours, with a liquid-to-solid ratio of 20:1, wherein the pH of the solution was adjusted to be always within the above range by dropping 1 mol/L hydrochloric acid solution during the stirring process, and the stirring speed was controlled to be 100 r/min;

(6) The material obtained in step (5) is filtered and separated to obtain a leachate and a solid, and the solid is repeatedly washed with deionized water and anhydrous ethanol until the filtrate is neutral. The filter cake is placed in a vacuum drying oven and dried at 40° C. for 16 h to obtain metallic titanium powder.

Example 4

(1) titanium dioxide with a particle size range of 500 to 1000 mesh and anhydrous calcium chloride are uniformly mixed in a mass ratio of 2:1, and pressed into a block I with a size of Φ20×20 mm at a pressure of 10 MPa;

(2) Magnesium oxide, calcium oxide and calcium carbide with a particle size range of 500 to 1000 mesh are uniformly mixed in a mass ratio of 1:1:1, and pressed into a block II with a size of Φ20×10 mm at a pressure of 10 MPa;

(3) placing the block II prepared in step (2) in a molybdenum boat and placing it in the lower layer of a graphite crucible, and placing the block I prepared in step (1) in the upper layer of the graphite crucible, separating the block I and the block II with a porous molybdenum plate, and covering the graphite crucible with a graphite cover;

(4) placing the graphite crucible obtained in step (3) in a vacuum atmosphere furnace, and performing the vacuum thermal reduction process in a low temperature section and a high temperature section in steps: first, at a pressure of less than 30 Pa, heating the atmosphere furnace at a heating rate of 10°C/min to 1000°C, and keeping the temperature at the reaction temperature for 180 min. At this time, the bottom of the graphite crucible is mainly calcium carbide reacting with magnesium oxide to generate magnesium vapor, and the magnesium vapor rises to reduce the titanium dioxide on the upper layer; then heating the atmosphere furnace at a heating rate of 10°C/min to 1300°C, and keeping the temperature at the same temperature for 240 min. In this stage, the remaining calcium carbide reacts with calcium oxide to generate calcium vapor, and the calcium vapor rises to further reduce the product of the previous stage, and obtains a reduced bulk material; after the first reduction process in this step, titanium mainly exists in the form of low-valent titanium oxide and a small amount of metallic titanium; after the second reduction process, titanium mainly exists in the form of metallic titanium;

(5) the block material obtained in step (4) was stirred and leached in a hydrochloric acid solution with a pH of 1 for 5 h, with a liquid-to-solid ratio of 16:1, wherein the pH of the solution was adjusted to be always within the above range by dropping 1 mol/L hydrochloric acid solution during the stirring process, and the stirring speed was controlled to be 300 r/min;

(6) The material obtained in step (5) is filtered and separated to obtain a leachate and a solid, and the solid is repeatedly washed with deionized water and anhydrous ethanol until the filtrate is neutral. The filter cake is placed in a vacuum drying oven and dried at 80° C. for 10 h to obtain metallic titanium powder.

Comparative Example 1: Kroll method of prior art.

Comparative Example 2: Hunter method of prior art.

Comparative Example 3: The method in patent application CN102921953A was used.

Comparative Example 4: The method in patent application CN101628337A was used.

Comparative Example 5: Same as Example 2, except that the low-temperature reduction period of step (4) is replaced with 8 hours, and the high-temperature reduction period is deleted, that is, the graphite crucible obtained in step (3) is placed in a vacuum atmosphere furnace, and the vacuum thermal reduction process is carried out in the low-temperature section: at a pressure of less than 30 Pa, the atmosphere furnace is heated to 900°C at a heating rate of 10°C/min, and the reaction temperature is kept at this temperature for 480 minutes to obtain a reduced bulk material.

Table 1 Comparison of the preparation methods of titanium sponge materials disclosed in the examples and some patents

As can be seen from the above table, compared with the Kroll method and the Hunter method, the present application uses _TiO2 as a titanium source for direct reduction to prepare sponge titanium, which simplifies the preparation process in terms of the operation flow, that is, the process of preparing _TiCl4 by chlorination _{of TiO2} is omitted; at the same time, the use of harmful gas chlorine is avoided, which is in line with the concept of green production; finally, the sponge titanium product prepared by the method used in the present application has a higher purity. In addition, with respect to the direct reduction method of _TiO2 to prepare sponge titanium, the present application proposes a segmented reduction method compared to the several methods mentioned in the comparative example. The low-temperature stage reduction helps to reduce energy consumption and obtain crude sponge titanium. The high-temperature stage deoxidation can further remove oxygen from the sponge titanium, thereby achieving better product quality.

Claims (5)

1. The method for preparing the metallic titanium powder by metallothermic reduction of titanium dioxide is characterized by comprising the following steps of:

(1) Uniformly mixing titanium dioxide with the granularity ranging from 100 meshes to 1000 meshes with anhydrous calcium chloride in a mass ratio of 1:1-3:1, and pressing the mixture into a block body I under the pressure of 10 MPa;

(2) Uniformly mixing magnesium oxide, calcium oxide and calcium carbide with the granularity range of 100-1000 meshes in a mass ratio of 1:1:1-1:1:2, and pressing the mixture into a block II under the pressure of 5-10 MPa;

(3) Placing the block II prepared in the step (2) in a molybdenum boat, placing the molybdenum boat in the lower layer of a graphite crucible, placing the block I prepared in the step (1) in the upper layer of the graphite crucible, separating the block I from the block II by a porous molybdenum plate, and covering a graphite cover above the graphite crucible;

(4) Heating the graphite crucible obtained in the step (3) to 800-1000 ℃ under the pressure of less than 30Pa, and preserving heat for 180-360 min; then heating to 1100-1300 ℃, and preserving heat for 180-360 min to obtain a reduced massive material;

(5) Stirring and leaching the block material obtained in the step (4) in hydrochloric acid solution with the pH value of 0.5-1 for 4-8h, wherein the pH value of the solution is always within the range by dropwise adding 1mol/L hydrochloric acid solution in the stirring process, and the stirring speed is controlled to be 100-300 r/min;

(6) Filtering and separating the material obtained in the step (5) to obtain a leaching solution and a solid, repeatedly washing the solid with deionized water and absolute ethyl alcohol until the filtrate is neutral, and drying the filter cake at 40-80 ℃ for 8-16 h to obtain the metallic titanium powder.

2. The method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide according to claim 1, wherein: the size of the block I in the step (1) is phi 15 multiplied by 20 to phi 20 multiplied by 20mm.

3. The method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide according to claim 1, wherein: the size of the block II in the step (2) is phi 15 multiplied by 10 to phi 20 multiplied by 10mm.

4. The method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide according to claim 1, wherein: the temperature rising rate in the step (4) is 10 ℃/min.

5. The method for preparing metallic titanium powder by metallothermic reduction of titanium dioxide according to claim 1, wherein: and (3) the liquid-solid ratio in the stirring leaching in the step (5) is more than 15:1.