Method for reducing the content of titanium tetrachloride in the wall of the titanium sponge

Abstract

The present application relates to the field of titanium sponge production, and particularly relates to a method for reducing the wall-climbing titanium chloride content of titanium sponge. The process optimization method based on secondary distillation significantly reduces the chlorine content of wall-climbing titanium while ensuring that the quality of the main titanium lump is not affected, thereby improving the overall consistency and quality of the titanium sponge product. The specific steps are as follows: complete the conventional distillation: first, complete the entire conventional distillation cycle (100-150 hours), at which time the Cl content of the lower part of the main titanium lump has reached a controlled and qualified level; maintain high temperature in the upper section: without ending the distillation process, the temperature of the upper section of the reactor corresponding to the wall-climbing titanium region is maintained at a high temperature of 1000-1100 DEG C; reduce the temperature of the lower section: at the same time, the temperature of the lower section of the reactor corresponding to the main titanium lump region is reduced to below 900 DEG C; perform secondary distillation: under the above differentiated temperature field, continue to implement secondary distillation, and the duration is strictly controlled within 50 hours.

Description

Technical Field

[0001] This invention relates to the field of sponge titanium production, and more particularly to a method for reducing the titanium chloride content in sponge titanium due to wall climbing. Background Technology

[0002] In the titanium industry chain, sponge titanium, as a core raw material for titanium material processing, has impurity content that directly determines the mechanical properties and application safety of downstream titanium alloys. Chlorine (Cl) content is a key quality indicator—if the residual chlorine is too high, volatile chloride gases will be generated during the subsequent electric arc furnace melting process, leading to defects such as porosity and looseness in the titanium ingots, and even affecting the reliability of titanium components in high-end fields such as aerospace. Therefore, one of the core objectives of the "reduction-distillation" process in sponge titanium production is to remove residual chlorine and chlorides (such as TiCl4, MgCl2, etc.) from the titanium ingot through high-temperature vacuum distillation.

[0003] The conventional distillation process typically follows magnesiothermal reduction and is carried out in a vertical stainless steel reactor. Process parameters are controlled as follows: temperature 800-950℃, vacuum degree ≤5×10⁻²Pa, duration 100-150 hours. Under these conditions, the main titanium mass at the bottom of the reactor, due to its dense packing and uniform heating (short heat conduction path, temperature deviation ≤30℃), allows residual chlorine between titanium particles to rapidly escape as Cl₂ or chloride vapor in the vacuum environment and be condensed and collected. According to GB / T2524-2019 "Sponge Titanium" standard, after this distillation cycle, the chlorine content of the main titanium mass can typically be reduced to ≤0.12%, meeting the quality requirements for Grade I sponge titanium (Grade I chlorine content limit ≤0.15%).

[0004] However, the "climbing titanium" formed on the upper part of the reactor's inner wall has a significant problem of excessive chlorine content. The formation of climbing titanium originates in the early stages of the reduction reaction. Titanium crystal nuclei adhere to the inner wall of the reactor with the reaction gas flow, gradually accumulating to form a loose layer of uneven thickness (5-20 mm). Its location and structural characteristics directly lead to a significant decrease in distillation efficiency: In terms of location, the upper part of the reactor inner wall is far from the heating source (the heating device is usually located at the bottom of the reactor), resulting in low heat conduction efficiency. The actual temperature is 60-90°C lower than that of the main titanium mass at the bottom. Since the chlorine volatilization rate is positively correlated with temperature (the volatilization rate decreases by about 40% for every 50°C decrease in temperature), the amount of chlorine released in the same distillation cycle is only 1 / 3 to 1 / 2 of that in the main titanium mass. In terms of structure, the porosity between climbing titanium particles is as high as 25%-35%, and the pores are mostly closed or semi-closed. The chlorine gas generated by volatilization is difficult to break through the dense surface pores and easily forms a "retention zone" inside. The final residual chlorine content can reach 0.3%-0.5%, far exceeding the qualified standard.

[0005] The hazards of high chlorine residue are cascading: Firstly, the chlorine content of the sponge titanium itself exceeds the standard, making it unsuitable for direct use as a qualified raw material in titanium alloy smelting. If collected separately, it requires additional secondary distillation, increasing the production cost by approximately 300-500 yuan per ton of sponge titanium. Secondly, improper handling (such as mixing with the main titanium mass during crushing) will directly raise the overall chlorine impurity level of the product. When the proportion of chlorinated sponge titanium reaches 5%-8%, the overall chlorine content will rise from 0.12% to over 0.18%, causing the product to be downgraded from Grade I to Grade II, resulting in a decrease in market price of 1500-2000 yuan per ton. More seriously, if high-chlorine sponge titanium is used in high-end fields such as aero-engine blades and deep-sea titanium alloy components, the porosity generated during smelting will reduce the tensile strength of the titanium material by 8%-12% and shorten its fatigue life by more than 30%, potentially causing significant safety hazards. Summary of the Invention

[0006] Purpose of the invention: To provide a more effective method for reducing the titanium chloride content on the walls of sponge titanium, the specific purpose of which is described in the detailed implementation section for several substantial technical effects.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for reducing the titanium chloride content in sponge titanium wall climbing is characterized by, The process optimization method based on double distillation significantly reduces the chlorine content of the climbing titanium while ensuring that the quality of the main titanium agglomerate is not affected, thereby improving the overall consistency and quality of sponge titanium products. The specific steps are as follows: Complete conventional distillation: First, complete a full conventional distillation cycle (100-150 hours), at which point the Cl content in the lower part of the main titanium block has reached a controlled and qualified level; Maintain high temperature in the upper section: Without ending the distillation process, maintain the temperature of the titanium region corresponding to the climbing wall in the upper section of the reactor at a high temperature of 1000-1100℃; Lowering the temperature of the lower section: At the same time, the temperature of the main titanium block region in the lower section of the reactor is reduced to below 900℃; Secondary distillation: Under the aforementioned differentiated temperature field, secondary distillation is carried out again, with the duration strictly controlled within 50 hours.

[0008] A further technical solution of the present invention is as follows: For climbing titanium: maintaining a high temperature of 1000-1100℃ in the upper section provides a stronger thermal driving force for the climbing titanium region, effectively promoting the continuous evaporation and removal of residual chlorides such as MgCl2, thereby significantly reducing its Cl content.

[0009] A further technical solution of the present invention is as follows: protecting the titanium agglomerate: reducing the temperature of the lower section that has already met the standard to below 900°C, which crucially inhibits excessive distillation inside and on the surface of the titanium agglomerate; this effectively avoids the risk of activation and migration of metallic impurities Fe and Cr into titanium due to prolonged high temperature, ensuring that the content of metallic impurity elements in the titanium agglomerate is stable and controllable and will not exceed the standard.

[0010] A further technical solution of the present invention is to limit the secondary distillation cycle to within 50 hours, thereby achieving the best balance between fully purifying the climbing titanium and protecting the quality of the main titanium agglomerate, while avoiding excessive increase in energy consumption.

[0011] The present invention, which adopts the above technical solution, has the following beneficial effects compared with the prior art: effectively reducing the Cl content of climbing titanium: through targeted high-temperature treatment, the Cl content of climbing titanium can be reduced to a level comparable to that of the main titanium agglomerate, solving the problem of its high residual content.

[0012] Ensuring the quality of the main titanium agglomerate: The reliable cooling measures in the lower stage prevent the introduction of new metal impurities during the secondary distillation process, ensuring the stability of the purity of the titanium agglomerate.

[0013] Improved overall product quality and consistency: The impurity content of both the climbing titanium and the main titanium agglomerate was effectively controlled, significantly improving the uniformity and quality grade of the entire furnace of sponge titanium products.

[0014] High feasibility of the process: Based on existing distillation equipment, it can be achieved simply by optimizing the temperature control strategy and adding a controlled short-cycle secondary distillation stage, without the need for major equipment modifications, and the implementation cost is controllable. Attached Figure Description

[0015] To further illustrate the present invention, the following description is provided in conjunction with the accompanying drawings: Figure 1 The flowchart is for the invention. Detailed Implementation

[0016] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] Example 1: Combining Figure 1 The core of this invention lies in implementing a staged, differentiated temperature-controlled double distillation process, the specific steps of which are as follows: Complete conventional distillation: First, complete a full conventional distillation cycle (100-150 hours), at which point the Cl content of the main titanium agglomerate (lower part) has reached a controlled and qualified level.

[0018] Maintain high temperature in the upper section: Without ending the distillation process, maintain the temperature of the upper section of the reactor (corresponding to the climbing titanium region) at a high temperature of 1000-1100℃.

[0019] Lowering the temperature of the lower section: At the same time, the temperature of the lower section of the reactor (the main titanium bulk region) is lowered to below 900°C.

[0020] Secondary distillation: Under the aforementioned differentiated temperature field, secondary distillation is carried out again, with the duration strictly controlled within 50 hours.

[0021] For climbing titanium: Maintaining a high temperature of 1000-1100℃ in the upper section provides a stronger thermal driving force for the climbing titanium region, effectively promoting the continuous evaporation and removal of residual chlorides (such as MgCl2), thereby significantly reducing its Cl content.

[0022] Protecting the titanium agglomerate: Lowering the already compliant lower section temperature to below 900℃ critically suppresses excessive distillation inside and on the surface of the titanium agglomerate. This effectively avoids the risk of activation and migration of metallic impurities (such as Fe and Cr) into the titanium due to prolonged high temperatures, ensuring that the content of metallic impurity elements in the titanium agglomerate remains stable and controllable, and does not exceed the standard.

[0023] Efficiency and balance: By limiting the secondary distillation cycle to within 50 hours, the optimal balance was achieved between fully purifying the climbing titanium and protecting the quality of the main titanium agglomerate, while avoiding excessive energy consumption.

[0024] Defect 1: Under conventional distillation, the temperature of the climbing titanium is low, and the chloride volatilization rate is much lower than that of the main titanium mass, resulting in insufficient chloride removal. The chloride content of the climbing titanium exceeds the standard by 0.3%~0.5%. Existing technical defects: The conventional distillation heating device is located at the bottom of the reactor. The climbing titanium at the top of the reactor is far from the heat source, resulting in low heat transfer efficiency. The actual temperature of the climbing titanium is 60-90℃ lower than that of the main titanium mass at the bottom. The chlorine volatilization rate is positively correlated with temperature. For every 50℃ decrease in temperature, the chloride volatilization rate decreases by about 40%. Under the same distillation time, the amount of chlorine released from the climbing titanium is only 1 / 3 to 1 / 2 of that from the main titanium mass. The residual chlorine in the climbing titanium is 0.3%~0.5%, which exceeds the GB / T 2524-2019 standard of ≤0.15% for Grade I sponge titanium.

[0025] The corresponding solution logic of this invention Compared with the shortcomings of existing technologies, conventional distillation maintains a uniform temperature of 800-950℃ throughout the process, which cannot compensate for the natural low temperature limitation of climbing titanium. This patent innovatively introduces a differentiated segmented temperature-controlled secondary distillation process into the distillation process of sponge titanium. After the conventional distillation is completed in 100-150 hours and the main titanium mass reaches the chlorine standard, the vacuum distillation system is not terminated. Instead, the climbing titanium region in the upper part of the reactor is maintained at a high temperature of 1000-1100℃.

[0026] The temperature of 1000~1100℃ is much higher than the highest temperature of 950℃ in conventional distillation, which greatly enhances the thermal driving force of the titanium region climbing the wall and greatly increases the saturated vapor pressure of residual chlorides such as MgCl2, thus accelerating the evaporation of chlorides from a thermodynamic perspective. It compensates for the natural low-temperature defects of climbing titanium, offsets the heat transfer disadvantage at the top of the reactor, and eliminates the difference in volatilization rate caused by the natural temperature difference of 60~90℃ between climbing titanium and the main titanium mass. Under continuous vacuum, chloride vapor rapidly escapes from the closed / semi-closed pore retention zone of the climbing titanium, significantly reducing the residual Cl content of the climbing titanium, making the chloride index of the climbing titanium equal to that of the main titanium mass, and directly solving the core defect of excessive chloride in climbing titanium.

[0027] Defect 2: The porous structure of the titanium used for climbing walls (porosity 25%~35%) traps chloride vapor in closed / semi-closed pores, forming chlorine retention zones. Conventional distillation cannot completely remove chlorine impurities from these pores. Existing technical defects: Climbing titanium is a loosely packed layer formed by titanium crystal nuclei carried by reducing gas flow and adhering to the inner wall of the reactor. It is 5-20 mm thick and has a porosity of 25%-35%. A large number of the pores are closed or semi-closed structures. The conventional distillation temperature is too low, the volatilization power of chloride is insufficient, and the steam has difficulty penetrating the surface pores to escape. It remains inside the climbing titanium, which ultimately causes serious excess of chlorine residue.

[0028] The corresponding solution logic of this invention In contrast to the shortcomings of existing technologies, conventional distillation temperatures are limited to a maximum of 950°C, which is insufficient to drive chlorides deep within the pores to break through the pore barrier and diffuse outwards. This patent innovatively and non-obviously applies a zoned high-temperature enhanced desorption mechanism to the purification of porous titanium structures, with the upper section's high temperature of 1000~1100°C providing a dual effect: High temperature increases the thermal kinetic energy of chloride molecules inside the pores, reduces the adsorption force of chloride vapor on the pore wall, and allows MgCl2 and TiCl4 trapped in the closed pores to fully vaporize. High temperature creates a vapor partial pressure gradient from the top of the reactor downwards. The vaporized chloride vapor diffuses outwards along the pore channels and is rapidly extracted and condensed under continuous vacuum. By combining it with a continuous vacuum distillation system, the chlorine impurity discharge channel inside the porous climbing titanium is opened from a kinetic perspective, eliminating the chlorine retention zone in the pores and completely solving the structural defect of difficult dechlorination of loose climbing titanium.

[0029] Defect 3: The separate recovery of high-chlorine climbing titanium requires additional distillation, increasing production costs by 300-500 yuan per ton of sponge titanium; mixing it into the main titanium mass lowers the overall product grade, resulting in a loss of 1500-2000 yuan per ton in selling price. Existing technical defects: Excessive titanium chloride content in the wall-climbing process makes it unusable for direct recycling. Separate collection and reprocessing would increase processing costs by 300-500 yuan / ton. If the proportion of wall-climbing titanium chloride mixed in the crushing process is 5%-8%, the titanium chloride content in the entire furnace of sponge will increase from 0.12% to over 0.18%, and the product will be downgraded from Grade I to Grade II, resulting in a price reduction of 1500-2000 yuan per ton, leading to significant economic losses.

[0030] The corresponding solution logic of this invention: Compared to the shortcomings of existing technologies, current processes can only ensure the quality of the main titanium mass, while the titanium that climbs the walls must be sorted and processed separately, resulting in multiple costs such as manual sorting, energy consumption for secondary distillation, and equipment occupation. This patent innovatively and non-obviously integrates the integrated secondary purification in the same furnace into the end of the original distillation cycle, eliminating the need for separate separation of the titanium that climbs the walls and the need for additional independent secondary distillation equipment. The purification of the main titanium mass and the deep dechlorination of the climbing titanium are completed simultaneously in the vacuum system of the same reactor. After the chlorine index of the climbing titanium meets the standard, it can be mixed and crushed with the main titanium mass, eliminating the need for climbing titanium sorting and separate secondary distillation process, thus eliminating an additional processing cost of 300-500 yuan per ton. The impurity levels of sponge titanium climbing the wall and the main titanium mass are uniform throughout the furnace, with no local high chlorine impurity sources. This avoids the overall chlorine exceeding the standard caused by crushing and mixing materials, and maintains the grade of first-class products. It avoids the loss of 1,500 to 2,000 yuan per ton due to the grade difference, and simultaneously improves product consistency and production economic efficiency.

[0031] Defect 4: When high-chlorinated sponge titanium is used in high-end components for aerospace and deep-sea applications, the smelting process generates chloride gas, resulting in porous ingots and a significant deterioration in the material's mechanical properties, posing a safety hazard. Existing technical defects: High-chlorinated sponge titanium releases volatile chloride gas during electric arc melting, forming pores and porosity defects inside the titanium ingot. When used in aero-engine blades and deep-sea titanium alloy components, the tensile strength of the material decreases by 8% to 12%, and the fatigue life is shortened by more than 30%, posing significant safety hazards for use in high-end equipment.

[0032] The corresponding solution logic of this invention: Compared to the shortcomings of existing technologies, current processes cannot simultaneously purify the wall-climbing titanium, resulting in a continuous presence of high-chlorine materials within the furnace, large fluctuations in overall chlorine impurities in the finished product, and an inability to guarantee the stability of raw materials for high-end products. This patent innovatively and non-obviously applies a process for preparing homogeneous sponge titanium with low chlorine throughout the entire process to the end of the reduction-distillation step, uniformly reducing the chlorine content of all materials in the furnace through differentiated temperature-controlled secondary distillation. The chlorine content of the climbing titanium and the main titanium mass is simultaneously controlled to ≤0.12% in the first grade range, ensuring uniform and stable chlorine impurities in the raw materials throughout the furnace, and completely eliminating the source of large amounts of chloride gas evolution during the smelting process; Eliminating porosity and looseness defects in ingots from the raw material end ensures that the tensile strength and fatigue performance of downstream titanium materials meet the standards, avoids safety risks in the service of high-end titanium components, and meets the high reliability requirements of aerospace, deep-sea equipment and other applications.

[0033] Defect 5: If the uniform high-temperature distillation time of the entire furnace is directly extended to remove the climbing titanium chloride, the long-term high temperature of the main titanium agglomerate in the lower section will cause the activation and migration of Fe and Cr equipment impurities, resulting in excessive metal impurities and damaging the quality of the main titanium agglomerate. Existing technologies have inherent flaws (drawbacks of conventional improvement approaches). The industry's conventional approach to improvement is to extend the uniform high-temperature distillation time to enhance the dechlorination effect of the climbing titanium. However, the main titanium mass in the lower section of the reactor is kept at a high temperature of ≥950℃ for a long time. The Fe and Cr elements on the inner wall of the reactor stainless steel are activated by heat and diffuse into the interior of the titanium mass, resulting in excessive impurities in the sponge titanium metal and damage to the quality of the main titanium mass. It is impossible to balance the dechlorination of climbing titanium and the purity of the main titanium mass.

[0034] The corresponding solution logic of this invention Compared to the shortcomings of existing technologies, conventional overall high-temperature extended distillation schemes suffer from the contradiction of being unable to simultaneously achieve dechlorination and purity preservation; this patent innovatively and non-obviously combines the use of upper and lower sections with reversed differential temperature control coupled with short-cycle secondary distillation to form a complementary and balancing process: While the upper section of the climbing titanium is heated to 1000~1100℃ to enhance dechlorination, the lower section of the main titanium mass is simultaneously cooled to below 900℃. The low temperature below 900℃ can significantly suppress the activation and diffusion kinetics of Fe and Cr metal elements in the stainless steel reactor, block the migration path of impurities to the titanium mass, and stably control the content of metal impurities in the main titanium mass to not exceed the standard. The duration of the second distillation is strictly limited to within 50 hours. The short cycle further compresses the high-temperature exposure time of the main titanium agglomerate, balancing the relationship between the deep dechlorination of the climbing titanium, the protection of the purity of the main titanium agglomerate, and the production energy consumption. This avoids the double problems of energy consumption surge and impurity contamination caused by unlimited extension of distillation, and achieves simultaneous compliance of both, thus solving the core contradiction of traditional processes that suffer from one problem while another is addressed.

[0035] Defect 6: Conventional improvement solutions require the addition of independent wall-climbing titanium treatment equipment, resulting in significant investment in equipment modification, complex changes to the process route, and high difficulty in implementation. Existing technologies have inherent drawbacks: processing climbing titanium separately requires the addition of a small vacuum distillation furnace, a matching vacuum unit, and a temperature control system, resulting in high investment in equipment upgrades. After the production line processes are split, the material transfer and sorting processes increase, the complexity of on-site operations increases, and the cost of large-scale promotion is high.

[0036] The solution proposed in this invention addresses the shortcomings of existing technologies, which rely on adding new equipment and restructuring production lines, resulting in high costs and poor process compatibility. This patent innovatively and non-obviously utilizes a core improvement method: zoned modification of the existing distillation equipment's temperature control system combined with short-cycle secondary distillation at the rear end. It optimizes the temperature control system of the upper and lower sections of the reactor by creating independent zoned temperature controls, eliminating the need for adding an entire new distillation system. All processes can be completed using existing reduction-distillation vertical reactors and vacuum units, requiring minimal equipment modification and low initial investment. The process is integrated after the existing 100-150 hour conventional distillation cycle, without the need to modify the front-end magnesium thermal reduction process. The production cycle is minimally altered, the on-site operation process is simple, and the feasibility for industrialization is strong. It simultaneously solves all derivative defects caused by excessive titanium chloride on the wall with extremely low modification costs.

[0037] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims.

Claims

1. A method for reducing the titanium chloride content in sponge titanium wall climbing, characterized in that, The process optimization method based on double distillation significantly reduces the chlorine content of the climbing titanium while ensuring that the quality of the main titanium agglomerate is not affected, thereby improving the overall consistency and quality of sponge titanium products. The specific steps are as follows: Complete conventional distillation: First, complete a full conventional distillation cycle (100-150 hours), at which point the Cl content in the lower part of the main titanium block has reached a controlled and qualified level; Maintain high temperature in the upper section: Without ending the distillation process, maintain the temperature of the titanium region corresponding to the climbing wall in the upper section of the reactor at a high temperature of 1000-1100℃; Lowering the temperature of the lower section: At the same time, the temperature of the main titanium block region in the lower section of the reactor is reduced to below 900℃; Secondary distillation: Under the aforementioned differentiated temperature field, secondary distillation is carried out again, with the duration strictly controlled within 50 hours.

2. The method for reducing the titanium chloride content of sponge titanium wall climbing as described in claim 1, characterized in that, For climbing titanium: Maintaining a high temperature of 1000-1100℃ in the upper section provides a stronger thermal driving force for the climbing titanium region, effectively promoting the continuous evaporation and removal of residual chlorides such as MgCl2, thereby significantly reducing its Cl content.

3. The method for reducing the titanium chloride content of sponge titanium wall climbing as described in claim 1, characterized in that, Protecting the titanium agglomerate: Lowering the already qualified lower section temperature to below 900℃ is crucial to suppressing excessive distillation inside and on the surface of the titanium agglomerate; this effectively avoids the risk of activation and migration of metallic impurities Fe and Cr into the titanium due to prolonged high temperature, ensuring that the content of metallic impurity elements in the titanium agglomerate is stable and controllable and will not exceed the standard.

4. The method for reducing the titanium chloride content of sponge titanium wall climbing as described in claim 1, characterized in that, By limiting the secondary distillation cycle to within 50 hours, the optimal balance was achieved between fully purifying the climbing titanium and protecting the quality of the main titanium agglomerate, while avoiding excessive energy consumption.

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