A method for recycling titanium scrap

Abstract

This invention relates to the field of metal recycling technology and discloses a method for recycling titanium scrap, comprising: a mechanical pretreatment stage for crushing and primary magnetic separation of titanium scrap; a cleaning and rinsing stage employing a four-step cleaning process combining ultrasonic waves and spraying with a synergistic chelating agent-biosurfactant-buffer system; water softening pretreatment for hard water environments using a sacrificial-functional double-layer chelating system and a ternary buffer system; a dehydration and drying stage for removing moisture; and a sorting and purification stage using multi-stage magnetic separation and various physical sorting methods to obtain high-purity titanium scrap products. This invention achieves the simultaneous execution of three functions: chelating agent complexation of metal ions, surfactant emulsification of oil contamination, and buffer stabilization of the reaction environment. The cleaning efficiency is 3-5 times higher than that of a single cleaning method, solving the problems of competitive consumption of chelating agents and poor cleaning process stability in hard water environments, thus realizing high-quality recycling of titanium scrap.

Description

Technical Field

[0001] This invention relates to the field of metal recycling technology, and more specifically, to a method for recycling titanium scrap. Background Technology

[0002] Titanium and titanium alloys are widely used in high-end manufacturing fields such as aerospace, chemical industry, and medical devices due to their excellent corrosion resistance, high strength, and lightweight properties. The processing of titanium materials generates a large amount of titanium shavings, which have significant recycling value. However, the cutting fluid, mineral oil, metal dust, and various metal ion impurities adhering to their surfaces severely affect their recycling quality.

[0003] Existing methods for titanium scrap recycling suffer from the following technical drawbacks: First, traditional single-method cleaning (such as simple ultrasonic cleaning or simple spray rinsing) has low cleaning efficiency and is unable to completely remove complex contaminants from the surface of titanium scrap; second, existing cleaning methods are ineffective at removing metal ion contaminants, especially Fe. 3 ⁺、Cu 2 ⁺、Al 3 ⁺ Plasma is difficult to remove effectively; third, the hard water commonly used in industrial production causes a large amount of chelating agents in the cleaning agent to be consumed by calcium and magnesium ions, resulting in high cleaning costs and unstable effects; fourth, pH fluctuations during the cleaning process affect the activity of the cleaning agent, making it difficult to establish standardized process specifications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for recycling titanium scrap, comprising the following steps:

[0005] Step 1: Mechanical pretreatment:

[0006] The titanium chips are crushed by crushing equipment to make the particle size uniform in the range of 3-15mm, and then magnetic separation is performed to remove iron impurities.

[0007] Step 2: Water softening pretreatment:

[0008] The raw water is softened to reduce its hardness to below 50 mg / L;

[0009] Step 3: Preparation of the composite cleaning solution:

[0010] The cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The double-layer chelation system included sodium citrate at a concentration of 0.5-1.0 g / L as a sacrificial chelating agent and EDTA or DTPA at a concentration of 1.0-2.0 g / L as a functional chelating agent. The ternary buffer system was prepared by disodium hydrogen phosphate, sodium carbonate, and triethanolamine in a mass ratio of 2:1:1, with a total concentration of 2.0-4.0 g / L. At the same time, a biosurfactant at a concentration of 0.2-0.8 g / L and a dispersant at a concentration of 0.1-0.3 g / L were added.

[0011] Step 4: Ultrasonic Co-cleaning

[0012] The pretreated titanium shavings were immersed in a composite cleaning solution at a frequency of 20-40 kHz and a power density of 0.8-1.5 W / cm². 2 Clean with ultrasonic waves for 10-20 minutes;

[0013] Step 5: High-pressure spray cleaning:

[0014] The titanium shavings were rinsed and cleaned with a water spray at a pressure of 0.3-0.8 MPa for 5-10 minutes.

[0015] Step 6: Rinsing treatment:

[0016] The cleaning agent is removed by ultrasonic rinsing and spray rinsing in sequence.

[0017] Step 7: Dehydration and drying:

[0018] A three-stage dehydration and drying process is performed;

[0019] Step 8: Multi-level sorting:

[0020] High-purity titanium scrap products are obtained through purification processes such as magnetic separation, gravity separation, color sorting, X-ray sorting, and laser sorting.

[0021] Preferably, the water softening pretreatment adopts a chemical precipitation method, in which sodium carbonate and sodium hexametaphosphate are added to the raw water. Sodium carbonate reacts with calcium ions to form calcium carbonate precipitate, and reacts with magnesium ions under hydrolysis conditions to form magnesium hydroxide precipitate. Sodium hexametaphosphate complexes with the remaining calcium and magnesium ions to form a soluble complex.

[0022] Preferably, the biosurfactant is rhamnolipid or saponin surfactant, and the dispersant is sodium polyacrylate.

[0023] Preferably, the operating conditions for ultrasonic synergistic cleaning are: cleaning fluid temperature 25-45℃, mass ratio of titanium shavings to cleaning fluid 1:3-1:5, and cleaning fluid level 2-5cm above the surface of titanium shavings.

[0024] Preferably, the high-pressure spray cleaning adopts a multi-angle spray system, the spray water temperature is 40-60℃, the distance between the nozzle and the titanium shavings surface is 10-20cm, and multiple nozzles are arranged at a 60° angle.

[0025] Preferably, the rinsing process includes ultrasonic rinsing for 5-8 minutes and secondary spray rinsing for 3-5 minutes, the conductivity of the rinsing water is ≤50μS / cm, and the final residue of cleaning agent on the titanium scrap surface is ≤5mg / kg.

[0026] Preferably, the three-stage dehydration and drying process includes: a cold air dehydration stage using ambient temperature air at a wind speed of 15-25 m / s for 10-15 minutes; a hot air dehydration stage using hot air at a temperature of 80-120℃ and a wind speed of 10-20 m / s for 20-30 minutes; and a drying stage using heat at a temperature of 150-200℃ for 30-60 minutes, resulting in a final titanium scrap moisture content of ≤0.1%.

[0027] Preferably, the multi-stage separation includes: two-stage magnetic separation to remove ferromagnetic impurities, and high-density inclusion separation to remove inclusions with a density greater than 6.0 g / cm³. 3 Heavy metal impurities are removed by color sorting of titanium oxide chips, high-density inclusions are removed by X-ray sorting, and alloy grade laser sorting is used to distinguish pure titanium chips from titanium alloy chips.

[0028] Preferably, the sacrificial chelating agent preferentially complexes with calcium and magnesium ions and iron and manganese ions in water, and the functional chelating agent specifically binds to Fe on the surface of titanium scrap. 3 ⁺、Cu 2 ⁺、Al 3 The functional chelating agent can effectively utilize over 85% of impurity metal ions such as ⁺ to form complexes.

[0029] Preferably, the final titanium scrap product has a titanium content of ≥99.5% and an impurity content of ≤0.5%, and the cleaning efficiency is 3-5 times higher than that of traditional single cleaning methods, while the cost of chelating agent is more than 80% lower than that of the unoptimized solution.

[0030] The beneficial effects of this invention are as follows:

[0031] Significantly improved cleaning efficiency: Through the synergistic complexation effect of chelating agents and ultrasonic cavitation, the synergistic emulsification effect of biosurfactants and spray water, and the synergistic effect of a ternary buffer system maintaining pH stability, the triple functions of chelating agents complexing metal ions, surfactants emulsifying oil stains, and buffers stabilizing the reaction environment are achieved simultaneously. This results in a metal ion removal rate of over 95% and an oil stain removal rate of over 98% on the surface of titanium scraps. The cleaning efficiency is 3-5 times higher than that of traditional single cleaning methods, resulting in titanium scrap products with qualified surface cleanliness.

[0032] Economic advantages in hard water environments: The sacrificial-functional dual-layer chelating system effectively addresses the competitive consumption of chelating agents by calcium and magnesium ions in hard water through functional division of labor, increasing the effective utilization rate of functional chelating agents from 40-50% in traditional processes to over 85%. The total consumption of chelating agents only needs to be increased by 10-15% to achieve the cleaning effect of soft water environments in hard water environments, saving more than 80% of chelating agent usage costs compared to unoptimized solutions.

[0033] Significantly improved process stability: The phosphate-organic amine-carbonate ternary buffer system has strong resistance to water quality fluctuations, reducing the fluctuation coefficient of cleaning effect from ±25% in traditional processes to ±5%, and realizing standardized operation of the cleaning process in the range of water hardness of 50-400 mg / L, providing a stable process foundation for the large-scale production and application of titanium scrap recycling.

[0034] Outstanding anti-scaling performance: The addition of sodium polyacrylate dispersant keeps calcium and magnesium salt precipitates in a dispersed state with an average particle size of less than 100 nanometers, preventing the precipitates from accumulating and depositing on the surface of pipes and equipment, effectively avoiding scaling in the cleaning system, reducing equipment maintenance costs by 60%, and extending the continuous operation time of cleaning equipment from 48 hours to more than 168 hours.

[0035] Excellent environmental friendliness: By using bio-derived surfactants such as rhamnolipids and saponins to replace traditional petrochemical-derived synthetic surfactants, the biodegradability of cleaning wastewater is improved from 30 days to less than 7 days, and the chemical oxygen demand (COD) is reduced by 40%, which meets the requirements of green manufacturing and environmental protection, and provides an environmentally friendly technology path for the clean production upgrade of the titanium scrap recycling industry. Attached Figure Description

[0036] Figure 1 These are pH stability comparison curves of different buffer systems of the present invention;

[0037] Figure 2 This is a bar chart comparing the process stability of different buffering systems of the present invention. Detailed Implementation

[0038] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0039] Example 1

[0040] This embodiment proposes a method for recycling titanium scrap, including the following steps:

[0041] Step 1: Mechanical pretreatment:

[0042] The titanium shavings are crushed using a crushing device to make the particle size uniform at 9mm, and then magnetic separation is performed to remove iron impurities.

[0043] Step 2: Water softening pretreatment:

[0044] The raw water is softened to reduce its hardness to below 50 mg / L;

[0045] Step 3: Preparation of the composite cleaning solution:

[0046] The cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The double-layer chelation system included sodium citrate at a concentration of 0.8 g / L as a sacrificial chelating agent and EDTA or DTPA at a concentration of 1.5 g / L as a functional chelating agent. The ternary buffer system was prepared by disodium hydrogen phosphate, sodium carbonate, and triethanolamine in a mass ratio of 2:1:1, with a total concentration of 3.0 g / L. At the same time, a biosurfactant at a concentration of 0.5 g / L and a dispersant at a concentration of 0.2 g / L were added.

[0047] Step 4: Ultrasonic Co-cleaning

[0048] The pretreated titanium scrap was immersed in a composite cleaning solution at a frequency of 30 kHz and a power density of 1.2 W / cm². 2 Clean with ultrasonic waves for 15 minutes;

[0049] Step 5: High-pressure spray cleaning:

[0050] Titanium shavings were rinsed and cleaned for 8 minutes using a spray of water at a pressure of 0.6 MPa.

[0051] Step 6: Rinsing treatment:

[0052] The cleaning agent is removed by ultrasonic rinsing and spray rinsing in sequence.

[0053] Step 7: Dehydration and drying:

[0054] A three-stage dehydration and drying process is performed;

[0055] Step 8: Multi-level sorting:

[0056] High-purity titanium scrap products are obtained through purification processes such as magnetic separation, gravity separation, color sorting, X-ray sorting, and laser sorting.

[0057] in:

[0058] The water softening pretreatment adopts the chemical precipitation method, which adds sodium carbonate and sodium hexametaphosphate to the raw water. Sodium carbonate reacts with calcium ions to form calcium carbonate precipitate, and reacts with magnesium ions under hydrolysis conditions to form magnesium hydroxide precipitate. Sodium hexametaphosphate complexes with the residual calcium and magnesium ions to form soluble complexes.

[0059] The biosurfactant is a rhamnolipid surfactant, and the dispersant is sodium polyacrylate.

[0060] The operating conditions for ultrasonic synergistic cleaning are: cleaning fluid temperature 35℃, mass ratio of titanium shavings to cleaning fluid 1:4, and cleaning fluid level 3cm above the surface of titanium shavings.

[0061] High-pressure spray cleaning uses a multi-angle spray system with a spray water temperature of 50℃, a nozzle distance of 15cm from the titanium shavings surface, and multiple nozzles arranged at a 60° angle.

[0062] The rinsing process includes ultrasonic rinsing for 6 minutes and secondary spray rinsing for 7 minutes. The conductivity of the rinsing water is ≤50μS / cm, and the final residue of cleaning agent on the titanium scrap surface is ≤5mg / kg.

[0063] The three-stage dehydration and drying process includes: a cold air dehydration stage using ambient temperature air at a wind speed of 20 m / s for 12 minutes; a hot air dehydration stage using hot air at a temperature of 100℃ and a wind speed of 15 m / s for 25 minutes; and a drying stage using hot air at a temperature of 180℃ for 45 minutes, resulting in a final titanium scrap moisture content of ≤0.1%.

[0064] Multi-stage separation includes: two-stage magnetic separation to remove ferromagnetic impurities, and high-density inclusion separation to remove inclusions with a density greater than 6.0 g / cm³. 3 Heavy metal impurities are removed by color sorting of titanium oxide chips, high-density inclusions are removed by X-ray sorting, and alloy grade laser sorting is used to distinguish pure titanium chips from titanium alloy chips.

[0065] The sacrificial chelating agent preferentially complexes with calcium, magnesium, and iron / manganese ions in water, and the functional chelating agent specifically binds to Fe on the surface of titanium scrap. 3 ⁺、Cu 2 ⁺、Al 3 The functional chelating agent can effectively utilize over 85% of impurity metal ions such as ⁺ to form complexes.

[0066] The final titanium scrap product has a titanium content of ≥99.5% and an impurity content of ≤0.5%. The cleaning efficiency is 3-5 times higher than that of traditional single cleaning methods, and the cost of chelating agent is more than 80% lower than that of the unoptimized solution.

[0067] Example 2

[0068] The difference between this embodiment and Embodiment 1 is that:

[0069] The titanium shavings are crushed using a crushing device to make the particle size uniform at 3mm, and then magnetic separation is performed to remove iron impurities.

[0070] The cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The double-layer chelation system included sodium citrate at a concentration of 0.5 g / L as a sacrificial chelating agent and EDTA or DTPA at a concentration of 1.0 g / L as a functional chelating agent. The ternary buffer system was prepared by disodium hydrogen phosphate, sodium carbonate, and triethanolamine in a mass ratio of 2:1:1, with a total concentration of 2.0 g / L. At the same time, a biosurfactant at a concentration of 0.2 g / L and a dispersant at a concentration of 0.1 g / L were added.

[0071] The pretreated titanium scrap was immersed in a composite cleaning solution at a frequency of 20 kHz and a power density of 0.8 W / cm². 2 Clean with ultrasonic waves for 10 minutes;

[0072] The titanium shavings were rinsed and cleaned for 5 minutes using a spray of water at a pressure of 0.3 MPa.

[0073] The biosurfactant is a saponin-based surfactant, and the dispersant is sodium polyacrylate.

[0074] The operating conditions for ultrasonic synergistic cleaning are: cleaning fluid temperature 25℃, mass ratio of titanium shavings to cleaning fluid 1:3, and cleaning fluid level 2cm above the surface of titanium shavings.

[0075] High-pressure spray cleaning uses a multi-angle spray system with a spray water temperature of 40℃, a nozzle distance of 10cm from the titanium shavings surface, and multiple nozzles arranged at a 60° angle.

[0076] The rinsing process includes ultrasonic rinsing for 5 minutes and secondary spray rinsing for 3 minutes. The conductivity of the rinsing water is ≤50μS / cm, and the final residue of cleaning agent on the titanium scrap surface is ≤5mg / kg.

[0077] The three-stage dehydration and drying process includes: a cold air dehydration stage using ambient temperature air at a wind speed of 15 m / s for 10 minutes; a hot air dehydration stage using hot air at a temperature of 80℃ and a wind speed of 10 m / s for 20 minutes; and a drying stage using hot air at a temperature of 150℃ for 30 minutes, resulting in a final titanium scrap moisture content of ≤0.1%.

[0078] Example 3

[0079] The difference between this embodiment and Embodiment 1 is that:

[0080] The titanium chips are crushed using a crushing device to make the particle size uniform at 15mm, and then magnetic separation is performed to remove iron impurities.

[0081] The cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The double-layer chelation system included sodium citrate at a concentration of 1.0 g / L as a sacrificial chelating agent and EDTA or DTPA at a concentration of 2.0 g / L as a functional chelating agent. The ternary buffer system was prepared by disodium hydrogen phosphate, sodium carbonate, and triethanolamine in a mass ratio of 2:1:1, with a total concentration of 4.0 g / L. At the same time, a biosurfactant at a concentration of 0.8 g / L and a dispersant at a concentration of 0.3 g / L were added.

[0082] The pretreated titanium scrap was immersed in a composite cleaning solution at a frequency of 40 kHz and a power density of 1.5 W / cm². 2 Clean with ultrasonic waves for 20 minutes;

[0083] The titanium shavings were rinsed and cleaned for 10 minutes using a spray of water at a pressure of 0.8 MPa.

[0084] The operating conditions for ultrasonic synergistic cleaning are: cleaning fluid temperature 45℃, mass ratio of titanium shavings to cleaning fluid 1:5, and cleaning fluid level 5cm above the surface of titanium shavings.

[0085] High-pressure spray cleaning uses a multi-angle spray system with a spray water temperature of 60℃, a nozzle distance of 20cm from the titanium shavings surface, and multiple nozzles arranged at a 60° angle.

[0086] The rinsing process includes ultrasonic rinsing for 8 minutes and secondary spray rinsing for 5 minutes. The conductivity of the rinsing water is ≤50μS / cm, and the final residue of cleaning agent on the titanium scrap surface is ≤5mg / kg.

[0087] The three-stage dehydration and drying process includes: a cold air dehydration stage using ambient temperature air at a wind speed of 25 m / s for 15 minutes; a hot air dehydration stage using hot air at a temperature of 120℃ and a wind speed of 20 m / s for 30 minutes; and a drying stage using hot air at a temperature of 200℃ for 60 minutes, resulting in a final titanium scrap moisture content of ≤0.1%.

[0088] Example 4

[0089] This embodiment proposes a method for recycling titanium scrap, including the following steps:

[0090] Step 1: Mechanical Pretreatment

[0091] The titanium scraps to be processed are pre-treated by mechanical crushing and magnetic separation equipment in sequence:

[0092] (1) Shredding: Use a twin-shaft shredder (power ≥15 kW), adjust the blade gap to 8-12 mm, feed particle size ≤100 mm, and processing capacity 1-3 t / h. Shred large titanium shavings to a size that is easy to crush later;

[0093] (2) Crushing process: Jaw crusher (feed opening ≥ 200×300 mm), discharge opening adjusted to 3-15 mm, crushing ratio 1:3-1:5, so that the titanium chip particle size is uniform in the range of 3-15 mm, of which 3-5 mm accounts for 30-40%, 5-10 mm accounts for 40-50%, and 10-15 mm accounts for 10-20%;

[0094] (3) Primary magnetic separation: Use a dry magnetic separator (magnetic field strength 0.6-0.8 T) to remove iron impurity particles with a particle size greater than 1 mm. The uniformity of feeding is controlled within ±10%, the belt speed is 0.8-1.5 m / s, and the magnetic impurity removal rate is ≥90%.

[0095] Quality control: The crushed titanium shavings should be free of obvious long strips and flaky particles, with an aspect ratio ≤3:1, particle size distribution within the set range, and magnetic impurity content ≤0.5%. Obtaining pretreated titanium shavings with uniform particle size and low magnetic impurity content provides a suitable material state for subsequent cleaning processes. This step is a conventional technique in the field, but particle size control and magnetic separation for impurity removal lay the foundation for the implementation of subsequent innovative cleaning processes.

[0096] Step 2: Water softening pretreatment

[0097] Before preparing the cleaning solution, the raw water is pretreated by softening to remove calcium and magnesium ions.

[0098] Method 1: Ion exchange resin softening method, using 001×7 strong acid cation exchange resin, resin layer height 60-100 cm, water flow rate 8-15 m / h, softening is stopped when the hardness of the effluent is ≤50 mg / L.

[0099] Method 2: Chemical precipitation softening method, adding industrial-grade sodium carbonate to the raw water.

[0100] Chemical softening operation: First, determine the hardness of the raw water (using EDTA titration method, GB / T 5750.4-2006), and add sodium carbonate at 1.1-1.3 times the theoretical dosage. The dosage calculation formula is: Sodium carbonate dosage (mg / L) = 0.94 × total hardness (mg / L CaCO3).

[0101] The reaction is stirred at room temperature for 30-60 minutes, followed by a precipitation softening reaction: sodium carbonate reacts with calcium ions to form calcium carbonate precipitate; sodium carbonate reacts with magnesium ions under hydrolysis conditions to form magnesium hydroxide precipitate. After settling for 60-120 minutes, 5-15 mg / L of sodium hexametaphosphate is added to the supernatant. Through multidentate coordination complexation, it combines with residual calcium and magnesium ions (balance ≤ 50 mg / L) to form a stable soluble complex. Water quality testing: The calcium content in the treated water is measured using an atomic absorption spectrophotometer. 2 ⁺ and Mg 2⁺ content, calculate total hardness, and require that the treated water hardness ≤50 mg / L (as CaCO3), pH value 7.5-8.5, and turbidity ≤5 NTU. Obtain softened water that meets the requirements for subsequent cleaning solution preparation for the compound cleaning solution.

[0102] Step 3: Preparation of the composite cleaning solution

[0103] The cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The specific component specifications and addition methods are as follows:

[0104] (1) Addition of sacrificial chelating agent: Add analytical grade sodium citrate to softened water at a concentration of 0.5-1.0 g / L, preferably 0.7-0.8 g / L. Stir with an electromagnetic stirrer at 300-500 rpm for 5-10 minutes until completely dissolved. The stability constants lgK of this chelating agent with calcium and magnesium ions are 3.2 and 2.9, respectively, and it preferentially reacts with residual Ca in the water. 2 ⁺、Mg 2 ⁺ and Fe 2 ⁺、Mn 2 Interfering ion complexation (e.g., ⁺);

[0105] (2) Addition of functional chelating agent: Add analytical grade disodium ethylenediaminetetraacetate or diethylenetriaminepentaacetic acid, with the concentration controlled at 1.0-2.0 g / L, preferably 1.3-1.7 g / L. Continue stirring for 10-15 minutes until completely dissolved. This chelating agent reacts with Fe... 3 ⁺、Cu 2 ⁺、Al 3 The stability constants lgK of ⁺ are 25.1, 18.8, and 16.5, respectively, and it specifically complexes with impurity metal ions on the surface of titanium chips;

[0106] (3) Addition of biosurfactants: Add biosynthetic rhamnolipid (molecular formula C 26 H 48 O9, molecular weight 520.66, purity ≥95%, surface tension ≤30 mN / m) or saponin surfactants (such as tea saponin, molecular formula C 57 H 90 O 26 (Molecular weight 1221.33, purity ≥90%), concentration controlled at 0.2-0.8 g / L, preferably 0.4-0.6 g / L. Stir at room temperature for 15-20 minutes until the solution is uniform and transparent, used to emulsify cutting fluid and mineral oil on the surface of titanium chips into droplets with a diameter of 1-10 micrometers;

[0107] (4) Construction of a ternary buffer system: Analytical grade disodium hydrogen phosphate, anhydrous sodium carbonate, and triethanolamine were added sequentially in a mass ratio of 2:1:1, with the total concentration controlled at 2.0-4.0 g / L, preferably 2.5-3.5 g / L. After stirring and dissolving, the pH of the cleaning solution was measured and adjusted using a pH meter to stabilize it within the range of 7.0-8.5, preferably 7.5-8.0.

[0108] (5) Addition of dispersant: Add sodium polyacrylate (molecular weight 5000-15000, solid content ≥90%), with the concentration controlled at 0.1-0.3 g / L, preferably 0.15-0.25 g / L. Finally, stir for 5-8 minutes to prevent the calcium and magnesium salt precipitate from agglomerating into particles with a diameter greater than 100 nanometers.

[0109] After the above components are added in sequence and thoroughly mixed, a composite cleaning solution with a clear appearance, stable pH, and containing a double-layer chelating agent, a biosurfactant, a ternary buffer, and a dispersant is obtained. The surface tension of the cleaning solution is 25-35 mN / m, and the conductivity is 2-8 mS / cm.

[0110] Step 4: Ultrasonic Co-cleaning

[0111] The pretreated titanium shavings are immersed in a prepared composite cleaning solution and then cleaned using a multi-frequency ultrasonic cleaning device. Equipment requirements: ultrasonic cleaning tank volume ≥ 10L, equipped with dual-frequency or tri-frequency ultrasonic transducers (20-40 kHz adjustable), total power ≥ 300W, power density controlled between 0.8-1.5 W / cm³. 2 The preferred value is 1.0-1.2 W / cm². 2 Operating conditions: The temperature of the cleaning solution should be controlled at 25-45℃, preferably 30-40℃; the mass ratio of titanium shavings to cleaning solution should be 1:3-1:5, preferably 1:4; the level of the cleaning solution should be 2-5 cm above the surface of the titanium shavings.

[0112] Cleaning process: After the ultrasonic equipment is started, the cavitation phenomenon generated by the ultrasound in the cleaning fluid (i.e., the formation, growth, and collapse of tiny bubbles in the liquid) produces microjets with a diameter of 1-5 micrometers and local high-pressure shock waves with a pressure of 10-50 MPa on the surface of the titanium shavings. This causes the chelating agent molecules to quickly penetrate into the micropores and cracks on the surface of the titanium shavings with a depth of 1-20 micrometers, and react with Fe. 3 ⁺、Cu 2 ⁺、Al 3 ⁺ and other metal ions undergo a complexation reaction to form stable water-soluble complexes. The reaction equation is EDTA. 4 ⁻ + Fe 3 ⁺ → [Fe-EDTA]⁻、EDTA 4 ⁻ + Cu 2⁺ → [Cu-EDTA] 2 ⁻, EDTA 4 ⁻ + Al 3 ⁺ → [Al-EDTA]⁻. Simultaneously, the acoustic flow generated by ultrasound (flow rate 1-10 cm / s) and the periodic oscillation of cavitation bubbles promote the rearrangement of biosurfactant molecules at the oil-water interface, reducing the interfacial tension from 72 mN / m in pure water to 20-35 mN / m, emulsifying the adhering cutting fluid and mineral oil into stable droplets with a diameter of 1-10 micrometers. The cleaning time is controlled at 10-20 minutes, preferably 15 minutes. Intermediate product detection: Samples are taken every 5 minutes to detect the metal ion concentration (using atomic absorption spectrometry) and surface tension (using a surface tension meter) in the cleaning solution. When Fe... 3 A concentration ≥10 mg / L and a surface tension ≤35 mN / m indicate that the cleaning was sufficient. The final product was moist titanium shavings with water-soluble metal complexes and emulsified oil droplets adhering to the surface. The titanium shavings had a silvery-gray luster, and no obvious oil residue was visually observed.

[0113] Step 5: High-pressure spray cleaning

[0114] A multi-angle high-pressure spray system is used to rinse and clean the wet titanium shavings after ultrasonic cleaning. Equipment requirements: The high-pressure washer has a pressure ≥1.0 MPa, equipped with fan-shaped nozzles (spray angle 90-120°) and direct current nozzles, with a flow rate ≥20 L / min; the spray tank is equipped with a screen separation device and a return water circulation system. Operating conditions: The spray pressure is set to 0.3-0.8 MPa, preferably 0.5-0.6 MPa; the spray water temperature is controlled at 40-60℃, preferably 45-55℃; the distance between the nozzle and the titanium shaving surface is maintained at 10-20 cm, preferably 12-15 cm; multiple nozzles are arranged at a 60° angle to ensure full coverage rinsing of the titanium shaving surface.

[0115] Cleaning process: First, use a fan-shaped nozzle to rinse a large area for 2-3 minutes to remove loose adhering substances. Then, use a direct current nozzle to finely rinse key areas for 3-5 minutes. The mechanical scouring force (shear stress 10-100 Pa) generated by the spray water flow peels off and carries away the loosely adhering metal complexes and emulsified oil droplets from the titanium shavings surface, preventing contaminants from redepositing onto the clean surface. During the spraying process, the shear force of the water flow further reduces the size of the emulsified oil droplets to 0.5-5 micrometers, causing them to be stably dispersed in the wastewater and carried away by the water flow, thus completing the complete separation of oil from the surface of the titanium shavings.

[0116] Cleaning time should be controlled between 5-10 minutes, preferably 7 minutes. Intermediate product detection: Wastewater samples are collected during the cleaning process, and the turbidity is measured using a turbidimeter. When the wastewater turbidity is ≤10 NTU, it indicates that surface contaminants have been basically removed. Quality judgment: Visually inspected, the titanium shavings surface should exhibit a uniform silvery-white metallic luster, with no obvious oil spots or color differences. The final product should be clean titanium shavings with a surface metal ion and oil removal rate of over 95%, and a surface roughness Ra ≤3.2 μm.

[0117] Step Six: Ultrasonic Rinse

[0118] After spray cleaning, the titanium shavings are immersed in clean, softened water at a temperature of 25-35℃ for ultrasonic rinsing to remove residual cleaning agent components such as chelating agents, surfactants, and buffers from the surface of the titanium shavings. Rinsing water requirements: conductivity ≤50μS / cm, pH 6.5-7.5, suspended solids ≤10 mg / L. Equipment parameters: ultrasonic frequency and power density are the same as in step four (20-40 kHz, 0.8-1.5 W / cm²). 2 The mass ratio of titanium scrap to rinsing water is 1:2-1:3, preferably 1:2.5.

[0119] Rinsing procedure: Perform the rinsing process in two stages. The first rinse lasts 3-4 minutes. After draining the titanium shavings for 30 seconds, rinse again with fresh water for 2-4 minutes. Stir the titanium shavings every 2 minutes during the rinsing process to ensure even rinsing. Rinse water replacement standard: Replace the water when the conductivity is ≥100 μS / cm or the pH value deviates from 7.0±1.0.

[0120] Residue detection: Take a sample of rinsed titanium scrap, extract surface residues with deionized water, and determine the chelating agent content using ion chromatography and the surfactant content using spectrophotometry. The requirements are: chelating agent residue ≤ 5 mg / kg, surfactant residue ≤ 3 mg / kg, and total residue ≤ 10 mg / kg. Rinsedated titanium scrap with acceptable surface cleanliness and cleaning agent residue should be obtained.

[0121] Step 7: Secondary spray rinsing

[0122] A second spray rinse is performed on the rinsed titanium shavings using deionized water at a temperature of 25-35℃ and a conductivity ≤20 μS / cm to further remove residual cleaning agent components from the surface of the titanium shavings. Equipment requirements: low-pressure spray system equipped with atomizing nozzles (atomized particle size 50-200 μm), water flow rate 10-15 L / min.

[0123] Operating conditions: Spray pressure is controlled at 0.2-0.5 MPa, preferably 0.3 MPa; the distance between the nozzle and the titanium chips is 8-15 cm, preferably 10 cm; reciprocating spraying is used to cover each part of the titanium chip surface ≥ 2 times; the spraying time is controlled at 3-5 minutes, preferably 4 minutes.

[0124] Water quality monitoring: Wastewater is collected during the spraying process, and its conductivity is monitored in real time using a conductivity meter. A conductivity ≤ 30 μS / cm indicates thorough rinsing. Final testing: Total residual cleaning agent on the titanium scrap surface ≤ 5 mg / kg, pH 6.8-7.2, and moisture content 15-25%. The resulting clean, moist titanium scrap has a uniform silvery-white metallic luster and meets cleanliness standards.

[0125] Step 8: Three-stage dehydration and drying

[0126] The washed and rinsed wet titanium shavings are then subjected to a three-stage dehydration and drying process:

[0127] (1) Cold air dehydration stage: A centrifugal fan (power ≥ 3 kW) is used to generate ambient temperature air (20-30℃) with a wind speed of 15-25 m / s to blow the titanium shavings. The thickness of the titanium shavings layer is ≤ 5 cm, and the blowing time is 10-15 minutes, preferably 12 minutes. The free moisture attached to the surface of the titanium shavings is removed by forced convection. The moisture removed in this stage accounts for about 60-70% of the total moisture content.

[0128] (2) Hot air dehydration stage: Use hot air circulating drying equipment, set the temperature to 80-120℃, preferably 90-110℃, the wind speed to 10-20 m / s, preferably 15 m / s, and the relative humidity to ≤60%. Spread the titanium shavings evenly in a perforated tray, with a thickness ≤3 cm, and process for 20-30 minutes, preferably 25 minutes. Remove the bound moisture from the internal capillaries and surface micro-recesses of the titanium shavings through hot convection. This stage removes approximately 25-35% of the total moisture content.

[0129] (3) Drying stage: Use a forced circulation oven or fluidized bed dryer, set the temperature to 150-200℃, preferably 170-180℃, and the drying time to 30-60 minutes, preferably 45 minutes. Lay titanium chips in a single layer to ensure uniform heating and remove residual bound moisture and deep internal moisture.

[0130] Moisture content testing: Samples were taken and weighed after each stage. The weight change was measured using an electronic balance (accuracy 0.1 mg), and the moisture content was calculated using the formula: Moisture content (%) = (Wet weight - Dry weight) / Dry weight × 100%. The final requirement is that the titanium scrap has a moisture content ≤ 0.1%, with no visible water marks on the surface, and exhibits a dry, silvery-white metallic luster. Dry titanium scrap meeting storage and sorting requirements is obtained.

[0131] Step Nine: Multi-stage sorting and purification

[0132] The dried titanium shavings are then purified through the following sorting process:

[0133] (1) Secondary magnetic separation process: A high-intensity magnetic separator (magnetic field strength ≥ 0.8 T) is used to remove ferromagnetic impurity particles with a particle size greater than 0.5 mm. The feeding speed is controlled at 1-3 t / h, the belt speed is 0.5-1.2 m / s, and the separation efficiency is ≥ 95%.

[0134] (2) High-density inclusion separation process: Heavy medium separation or shaking table separation is adopted to remove inclusions with a density greater than 6.0 g / cm³ by utilizing density differences. 3 Heavy metal impurities (titanium density is 4.5 g / cm³) 3 For heavy dielectrics, ferrosilicon powder is used, and the dielectric density is controlled at 5.5-6.0 g / cm³. 3 Sorting accuracy ≥90%;

[0135] (3) Oxide scrap color sorting process: A photoelectric color sorter equipped with an RGB+near-infrared spectral detection system is used to separate silvery-white metallic titanium scraps from grayish-black titanium oxide scraps based on color differences. Light source power ≥1000 W, scanning frequency ≥2000 Hz, recognition accuracy ≥0.5 mm 2 The accuracy rate for elimination is ≥98%;

[0136] (4) High-density inclusion X-ray sorting process: A dual-energy X-ray transmission sorting machine is used to remove heavy metal impurities (such as Cu, Zn, Pb, etc.) with atomic numbers greater than titanium (atomic number 22) by utilizing the difference in atomic number. The X-ray tube voltage is 80-160 kV, the current is 0.5-3 mA, the detection resolution is ≤1 mm, and the sorting accuracy is ≥95%.

[0137] (5) Alloy grade laser sorting process: Laser-induced breakdown spectroscopy (LIBS) sorting equipment is used to classify pure titanium chips (Ti≥99.5%) and titanium alloy chips containing alloying elements such as vanadium and aluminum according to differences in elemental composition. Laser power ≥10 mJ, pulse frequency ≥20 Hz, detected elements include V, Al, Sn, Mo, etc., and the composition detection accuracy is ≤0.1%;

[0138] (6) Manual sorting process: On a sorting table with light intensity ≥1000 lux, skilled operators remove titanium chips with abnormal shape (length-to-diameter ratio >10:1) and obvious surface defects (cracks, pits, etc.). The sorting speed is ≤50 kg / h·person.

[0139] (7) Three-stage magnetic separation process: High gradient magnetic separator (magnetic field strength ≥ 1.5 T) is used to remove fine ferromagnetic impurities with a particle size of less than 0.5 mm. The medium is steel wool or steel wire mesh, and the processing capacity is 1-5 t / h.

[0140] (8) Weighing and packaging process: Separate according to different specifications (3-5 mm, 5-10 mm, 10-15 mm) using a vibrating screen, then weigh using an electronic scale (accuracy ≤10 g), and pack into moisture-proof woven bags, each bag weighing 25±0.5 kg.

[0141] Quality Inspection: Randomly selected samples are subjected to component analysis (using ICP-OES or XRF). The titanium content is required to be ≥99.5%, and the main impurity contents are: Fe≤0.2%, C≤0.08%, N≤0.03%, O≤0.15%, H≤0.012%. High-purity titanium scrap products that meet the requirements of national standard GB / T 3620.1-2016 are obtained.

[0142] Experimental verification

[0143] Experiment 1: Comparison of Cleaning Efficiency

[0144] 1. Experimental Objective

[0145] The effectiveness of the ultrasonic-spray combined cleaning method of the present invention, which uses a synergistic chelating agent-biosurfactant-buffer system, in improving the cleaning efficiency of removing metal ions and oil stains from titanium scrap surfaces compared to traditional single cleaning methods was verified.

[0146] 2. Preparation of experimental samples

[0147] Titanium shavings generated from the machining of TC4 titanium alloy were selected as test samples. Following the requirements of Example 4, the particle size of the titanium shavings was controlled within the range of 3-15 mm, with 5-10 mm shavings used for testing. The shavings were coated with cutting fluid and metal ion impurities. The titanium shavings were divided into four groups, each containing 500 g.

[0148] Control group 1: Traditional ultrasonic cleaning (using deionized water only);

[0149] Control group 2: Traditional spray cleaning (using only deionized water);

[0150] Control group 3: Traditional chemical cleaning (using 2.0 g / L EDTA solution);

[0151] Experimental group: The method of the present invention (using a composite cleaning solution).

[0152] 3. Experimental conditions

[0153] Experimental environment temperature: 25±2℃, cleaning solution temperature: 35±2℃, relative humidity: 50±5% Experimental water: deionized water, conductivity ≤10 μS / cm Testing equipment: atomic absorption spectrometer (AAS), infrared spectrophotometer, electronic balance (accuracy 0.1mg).

[0154] 4. Experimental Procedure

[0155] (1) Sample pretreatment: Degrease the titanium scrap sample with acetone, rinse with deionized water, dry at 120°C for 2 hours, and weigh and record the initial weight.

[0156] (2) Artificial contamination: Immersing clean titanium shavings in a solution containing Fe 3 ⁺ (50 mg / L), Cu 2 ⁺ (30mg / L), Al 3 Immerse in a mixed solution of ⁺ (20 mg / L) for 30 minutes, then coat with mineral oil (approximately 5 ml / 100 g titanium shavings), forming a surface with a metal ion content of Fe. 3 ⁺ (80-120 mg / kg), Cu 2 ⁺ (50-80mg / kg), Al 3 Standard contaminated samples with ⁺ (30-50 mg / kg).

[0157] (3) Cleaning treatment:

[0158] Control group 1: Ultrasonic cleaning (40kHz, 1.0W / cm) 2 (15 minutes)

[0159] Control group 2: High-pressure spray cleaning (0.5MPa, 50℃, 10 minutes);

[0160] Control group 3: Soaked in 2.0 g / L EDTA solution for 30 minutes, then ultrasonically cleaned for 15 minutes;

[0161] Experimental group: The complete cleaning process was carried out according to Example 4;

[0162] (4) Detection and analysis: After cleaning, samples were taken to analyze the residual metal ions and oil on the surface of the titanium scrap.

[0163] 5. Experimental Results

[0164] Table 1. Comparison of cleaning effects of different cleaning methods

[0165]

[0166] 6. Analysis and Summary

[0167] Experimental results show that the synergistic cleaning method of the chelating agent-biosurfactant-buffer system of the present invention is significantly superior to traditional single cleaning methods in both metal ion removal and oil stain removal. 3 ⁺、Cu 2 ⁺、Al 3 The removal rates of ⁺ reached 97.3%, 95.8%, and 94.2%, respectively, while the oil removal rate reached 98.1%, with an overall cleaning efficiency of 96.4%, which is 3.8 to 4.7 times higher than traditional methods, verifying the high efficiency of the technical solution. The advantages of synergistic cleaning are mainly reflected in the fact that chelating agents can effectively complex metal ions, biosurfactants can efficiently emulsify oil stains, and the buffer system ensures the stability of the cleaning process.

[0168] Experiment 2: Utilization rate test of chelating agents in hard water environment

[0169] 1. Experimental Objective

[0170] The effective utilization rate of the chelating agent in the sacrificial-functional bilayer chelating system of the present invention under different water hardness conditions was verified, proving that the system can effectively solve the problem of competitive consumption of chelating agents by calcium and magnesium ions in hard water environments, and achieve significant cost savings for chelating agents.

[0171] 2. Preparation of experimental samples

[0172] Preparation of simulated water samples with different hardness:

[0173] Soft water: Hardness ≤50 mg / L (calculated as CaCO3);

[0174] Medium hard water: 150 mg / L hardness - Hard water: 300 mg / L hardness;

[0175] Extremely hard water: hardness 500 mg / L, prepared using CaCl2·2H2O and MgSO4·7H2O, Ca 2 ⁺:Mg 2 The molar ratio is 3:2.

[0176] 3. Experimental conditions

[0177] Experimental temperature: 25±1℃, pH value: 7.5±0.5; Testing equipment: ion chromatograph, complexometric titration apparatus, UV-Vis spectrophotometer; Standard titanium scrap samples: 8-12mm size selected within the 3-15mm particle size range, surface containing Fe. 3 ⁺ (20mg / kg), Cu 2 ⁺ (15mg / kg), Al 3 ⁺ (10 mg / kg).

[0178] 4. Experimental Procedure

[0179] (1) Preparation of control group: 2.0 g / L EDTA solution was prepared in water with different hardness using the traditional single chelating agent method.

[0180] (2) Preparation of experimental group: The double-layer chelation system cleaning solution was prepared according to Example 4, with sodium citrate 0.8 g / L and EDTA 1.5 g / L.

[0181] (3) Cleaning test: Standard titanium chip samples were treated with the control group and experimental group cleaning solutions for 15 minutes respectively.

[0182] (4) Analysis of chelating agent consumption: The change in chelating agent concentration before and after cleaning was determined by complexometric titration.

[0183] (5) Evaluation of cleaning effect: The amount of residual metal ions on the surface of titanium scrap after treatment is measured.

[0184] (6) Utilization rate calculation: Effective utilization rate of chelating agent (%) = (chelating dose used to complex impurities on the surface of titanium scrap / total added chelating dose) × 100%

[0185] 5. Experimental Results

[0186] Table 2 Comparison of chelating agent utilization rates under different water hardness conditions

[0187]

[0188] 6. Analysis and Summary

[0189] Experimental results confirm the significant advantages of the double-layer chelation system of this invention. Under soft water conditions, the utilization rates of the chelating agents in both methods are similar, around 90%. However, as water hardness increases, the utilization rate of the chelating agent in the traditional method drops sharply, reaching only 28.4% under extremely hard water (500 mg / L), while the method of this invention still maintains a high utilization rate of 84.8%. Under hard water (300 mg / L) conditions, the chelating agent saving of the method of this invention reaches 102.1%, meaning that the amount of chelating agent used is reduced by more than half while still achieving better cleaning results. This is mainly due to the preferential consumption of calcium and magnesium ions by the sacrificial chelating agent (sodium citrate), protecting the effectiveness of the functional chelating agent (EDTA), achieving precise utilization of the chelating agent and significant cost savings.

[0190] Experiment 3: pH stability and process stability test

[0191] 1. Experimental Objective

[0192] The effectiveness of the phosphate-organic amine-carbonate ternary buffer system of the present invention in maintaining pH stability during the cleaning process, as well as its process stability under different water quality conditions and operating environments, were verified. This demonstrates that the buffer system can significantly reduce the fluctuation of cleaning effect and achieve process standardization.

[0193] 2. Preparation of experimental samples

[0194] Preparation of washing solutions with different buffer systems:

[0195] Control group 1: Unbuffered system (using only chelating agents and surfactants);

[0196] Control group 2: Single phosphate buffer system (Na2HPO4 / NaH2PO4);

[0197] Control group 3: Diphosphate-carbonate buffer system (Na2HPO4 / Na2CO3);

[0198] Experimental group: ternary buffer system (Na2HPO4 / Na2CO3 / triethanolamine, mass ratio 2:1:1, total concentration 3.0 g / L).

[0199] 3. Experimental conditions

[0200] Water quality tested: 5 different water samples with hardness ranging from 50 to 400 mg / L. Ambient temperature: 20-40℃. Cleaning time: 8 hours of continuous dynamic testing. Testing equipment: online pH meter, conductivity meter, turbidity meter, spectrophotometer.

[0201] 4. Experimental Procedure

[0202] (1) pH stability test:

[0203] Each group of cleaning solutions was prepared in different water qualities, and the initial pH was adjusted to 7.5 to simulate the actual cleaning process. Titanium shavings samples were added for dynamic cleaning.

[0204] pH changes were recorded every 30 minutes for 8 consecutive hours.

[0205] (2) Anti-interference capability test:

[0206] Add Ca gradually to the cleaning solution 2 ⁺、Mg 2 ⁺、Fe 3 Interfering ions such as ⁺;

[0207] The effect of different concentrations of interfering ions on pH stability was tested.

[0208] (3) Stability test of cleaning effect:

[0209] The cleaning experiment was repeated 20 times under different temperature and water quality conditions;

[0210] The coefficient of variation of the cleaning effect was statistically analyzed to evaluate the stability of the process;

[0211] (4) Long-term stability test: Store cleaning solutions with different buffer systems for 30 days and test their pH retention capacity.

[0212] 5. Experimental Results

[0213] Table 3 Comparison of pH stability and process stability of different buffer systems

[0214]

[0215] Figure 1 Comparison curves of pH stability for different buffer systems;

[0216] Figure 2 A bar chart comparing the process stability of different buffer systems.

[0217] 6. Analysis and Summary

[0218] Experimental results fully validated the superior performance of the ternary buffer system of this invention. During 8 hours of continuous cleaning, the pH fluctuation range of the unbuffered system reached 5.82-8.95, significantly deviating from the optimal cleaning pH range, resulting in a cleaning effect variation coefficient as high as ±28.5%. Although the single phosphate buffer system showed improvement, the pH still fluctuated within the range of 6.85-8.20, indicating limited process stability. The binary buffer system further improved stability, but still had shortcomings under strong interference conditions.

[0219] The ternary buffer system of this invention exhibits superior performance, maintaining a stable pH within a narrow range of 7.42-7.61, with a cleaning effect variation coefficient of only ±4.6%, representing a 6.2-fold improvement in stability compared to traditional unbuffered methods. The addition of triethanolamine not only enhances the buffering capacity but also functions as a cleaning aid, achieving a dual guarantee of pH stability and cleaning effectiveness, thus laying a solid foundation for the standardization of titanium scrap recycling processes.

[0220] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for recycling titanium scrap, characterized in that, Includes the following steps: Step 1: Mechanical pretreatment: The titanium chips are crushed by crushing equipment to make the particle size uniform in the range of 3-15mm, and then magnetic separation is performed to remove iron impurities. Step 2: Water softening pretreatment: The raw water is softened to reduce its hardness to below 50 mg / L; Step 3: Preparation of the composite cleaning solution: A cleaning solution was prepared using a double-layer chelation system and a ternary buffer system. The sacrificial chelating agent, functional chelating agent, biosurfactant, ternary buffer system, and dispersant were added sequentially. The double-layer chelation system consisted of sodium citrate (0.5-1.0 g / L) as a sacrificial chelating agent and EDTA or DTPA (1.0-2.0 g / L) as a functional chelating agent. The ternary buffer system was prepared by disodium hydrogen phosphate, sodium carbonate, and triethanolamine in a mass ratio of 2:1:1, with a total concentration of 2.0-4.0 g / L. Simultaneously, a biosurfactant (0.2-0.8 g / L) and a dispersant (0.1-0.3 g / L) were added. After stirring and dissolving, the pH of the cleaning solution was adjusted to stabilize it within the range of 7.0-8.

5. Step 4: Ultrasonic Co-cleaning The pretreated titanium shavings are immersed in a composite cleaning solution and cleaned for 10-20 minutes using ultrasonic waves with a frequency of 20-40 kHz and a power density of 0.8-1.5 W / cm². Step 5: High-pressure spray cleaning: A multi-angle spray system is used to rinse and clean titanium shavings with a spray water flow of 0.3-0.8 MPa for 5-10 minutes. The spray water temperature is 40-60℃, the distance between the nozzle and the surface of the titanium shavings is 10-20cm, and multiple nozzles are arranged at a 60° angle. Step 6: Rinsing treatment: The titanium shavings are subjected to ultrasonic rinsing and spray rinsing in sequence to remove residual cleaning agent. The ultrasonic rinsing is performed in two steps. The first rinsing lasts for 3-4 minutes. After the titanium shavings are removed and drained for 30 seconds, the second rinsing is performed with fresh rinsing water for 2-4 minutes. The rinsing water is replaced when the conductivity is ≥100μS / cm or the pH value deviates from 7.0±1.

0. The spray rinsing uses deionized water with a temperature of 25-35℃ and a conductivity ≤20μS / cm. It is equipped with atomizing nozzles with a particle size of 50-200μm and uses a reciprocating spray to cover each part of the titanium shavings surface ≥2 times. The rinsing is completed when the conductivity of the wastewater is ≤30μS / cm. Step 7: Dehydration and drying: A three-stage dehydration and drying process is performed; Step 8: Multi-level sorting: High-purity titanium scrap is obtained through purification processes including magnetic separation, gravity separation, color sorting, X-ray separation, laser separation, manual separation, and three-stage magnetic separation. Manual separation removes titanium scrap with abnormal shape and obvious surface defects on a sorting table with a light intensity of ≥1000 lux. The three-stage magnetic separation uses a high-gradient magnetic separator with a magnetic field strength of ≥1.5T to remove fine ferromagnetic impurities with a particle size of less than 0.5mm.

2. The titanium scrap recycling method according to claim 1, characterized in that, The water softening pretreatment adopts a chemical precipitation method, in which sodium carbonate and sodium hexametaphosphate are added to the raw water. Sodium carbonate reacts with calcium ions to form calcium carbonate precipitate, and reacts with magnesium ions under hydrolysis conditions to form magnesium hydroxide precipitate. Sodium hexametaphosphate complexes with the remaining calcium and magnesium ions to form soluble complexes.

3. The titanium scrap recycling method according to claim 1, characterized in that, The biosurfactant is rhamnolipid or saponin surfactant, and the dispersant is sodium polyacrylate.

4. The titanium scrap recycling method according to claim 1, characterized in that, The operating conditions for ultrasonic synergistic cleaning are as follows: cleaning fluid temperature 25-45℃, mass ratio of titanium shavings to cleaning fluid 1:3-1:5, and cleaning fluid level 2-5cm above the surface of titanium shavings.

5. The titanium scrap recycling method according to claim 1, characterized in that, The rinsing process includes ultrasonic rinsing for 5-8 minutes and secondary spray rinsing for 3-5 minutes. The conductivity of the rinsing water is ≤50μS / cm, and the final residue of cleaning agent on the titanium scrap surface is ≤5mg / kg.

6. The titanium scrap recycling method according to claim 1, characterized in that, The three-stage dehydration and drying process includes: a cold air dehydration stage using ambient temperature air at a wind speed of 15-25 m / s for 10-15 minutes; a hot air dehydration stage using hot air at a temperature of 80-120℃ and a wind speed of 10-20 m / s for 20-30 minutes; and a drying stage using hot air at a temperature of 150-200℃ for 30-60 minutes, resulting in a final titanium scrap moisture content of ≤0.1%.

7. The titanium scrap recycling method according to claim 1, characterized in that, The multi-stage sorting includes: two-stage magnetic separation to remove ferromagnetic impurities, high-density inclusion sorting to remove heavy metal impurities with a density greater than 6.0 g / cm³, color sorting of oxide chips to separate titanium oxide chips, high-density inclusion X-ray sorting to remove high-density metal impurities, and alloy grade laser sorting to distinguish pure titanium chips from titanium alloy chips.

8. The titanium scrap recycling method according to claim 1, characterized in that, The sacrificial chelating agent preferentially complexes with calcium, magnesium, iron, and manganese ions in water, while the functional chelating agent specifically complexes with Fe³⁺, Cu²⁺, and Al³⁺ impurity metal ions on the surface of titanium scrap.

9. The titanium scrap recycling method according to claim 1, characterized in that, The final titanium scrap product has a titanium content of ≥99.5% and an impurity content of ≤0.5%.

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