Chapter 16: Sustainability and Green Manufacturing
Sustainability and green manufacturing of cemented carbide focus on efficient resource utilization and minimized environmental impact. Through recycling and reuse (recovery rates >80%±5%), green processes (energy consumption reduction >20%±3%), and waste reduction (CO₂ emissions reduction >30%±5%), these efforts aim to recycle scarce resources such as tungsten (reserves <0.1%±0.01% of the Earth’s crust) and cobalt (price fluctuation >50%±10%), while maintaining performance comparable to traditional processes (hardness HV 1600-2000±30, wear rate <0.05 mm³ / N · m ± 0.01 mm³ / N · m). This chapter examines the recycling and reuse of cemented carbide, systematically analyzing its resource value, environmental benefits, and technical challenges, providing a theoretical and practical foundation for green manufacturing.
16.1 Recovery and reuse of cemented carbide
Cemented carbide recycling and reuse achieves efficient resource recycling through a variety of advanced processes, primarily chemical (acid and alkaline leaching, with recovery rates >85% ± 5%), physical (crushing and sorting, with purity >99% ± 0.5%), and metallurgical (smelting and reduction, with impurities <0.01% ± 0.001%). These methods effectively recover key elements such as tungsten and cobalt from cemented carbide, significantly reducing reliance on primary minerals (mining reductions >50% ± 5%) and environmental pollution (waste emissions reduced >40% ± 5%). These recycling processes are applicable not only to single waste materials such as used cutting tools and worn molds, but also to complex, multi-source waste materials (such as aviation components and automotive parts). By optimizing process parameters and equipment design, comprehensive recycling is achieved, from microstructure to macroscopic properties. This section examines the significance and challenges of cemented carbide recycling, providing an in-depth analysis combining resource value, environmental benefits, and technical challenges. The latest research findings and industrial practice data are introduced to ensure a professional and forward-looking discussion.
16.1.1 Significance and Challenges of Cemented Carbide Recycling
Cemented carbide recycling has far-reaching significance in terms of resource protection, environmental sustainability and economic benefits, while also facing complex process and technical challenges. The significance is mainly reflected in the following three aspects:
Cemented carbide recycling can alleviate the shortage of rare resources.
Tungsten reserves in the Earth’s crust are extremely limited (<0.1% ± 0.01%), with proven global reserves estimated at 3.1 million tons ± 50,000 tons, primarily distributed in China (approximately 1.8 million tons ± 50,000 tons, accounting for 60% ± 5% of global reserves), Russia (approximately 500,000 tons ± 20,000 tons), and Canada (approximately 300,000 tons ± 10,000 tons). Tungsten’s scarcity makes it a strategic metal, subject to international trade restrictions, mining depths (>500 m ± 50 m), and environmental regulations, resulting in high primary mining costs (>30 USD/kg ± 5 USD/kg). Cobalt reserves are even smaller (<0.01% ± 0.001%), with global reserves estimated at approximately 7 million tons ± 50,000 tons, of which the Democratic Republic of the Congo accounts for 60% ± 5%. Due to geopolitical risks (such as civil unrest and export bans) and supply chain disruptions, prices fluctuate significantly (over 50% fluctuations in the past five years, reaching as high as $80,000 ± 5,000 per ton). By recycling scrap (such as scrap tools, worn dies, and expired coatings), cemented carbide recycling can supplement global tungsten demand by 10% ± 2% (approximately 30,000 tons ± 500 tons) and cobalt demand by 8% ± 1% (approximately 12,000 tons ± 200 tons) annually, effectively alleviating resource shortages, particularly in the new energy battery (electric vehicle demand is growing by 20% ± 2% annually), aerospace (cobalt-based alloy demand is growing by 15% ± 2% annually), and cutting tools (tungsten demand is growing by 10% ± 1% annually).
Compared to primary mining, the recycling process significantly reduces greenhouse gas emissions (CO₂ reduction > 30
% ± 5%). This is because it avoids high-carbon processes such as ore excavation (energy consumption >2000 MJ/t ± 200 MJ/t, CO₂ emissions of approximately 20-30 t/t ± 2 t/t), transportation (fuel consumption >100 L/t ± 10 L/t, emissions of approximately 0.3 t/t ± 0.03 t/t), and smelting (blast furnace energy consumption >1500 kWh/t ± 100 kWh/t, emissions of approximately 1-2 t/t ± 0.1 t/t). For example, recycling 1000 tons of scrap cemented carbide can reduce CO₂ emissions by approximately 25,000 t ± 2,500 t, equivalent to the annual emissions of 5,000 gasoline-powered vehicles. Recycling also reduces land destruction caused by mining (reducing mining area by >1000 km² ) ± 100 km² ( approximately 0.1% of global arable land), water pollution (e.g., heavy metal leaching reduced by >60% ± 5%, tungsten concentrations reduced from >500 ppm to <50 ppm ± 5 ppm), and tailings accumulation (reduced by >500,000 tons ± 50,000 tons). Through wastewater treatment (acid-base neutralization pH 7 ± 0.2, membrane filtration pore size 0.01 μm ± 0.001 μm, recovery rate >90% ± 2%) and residual waste resource utilization (incineration calorific value >10 MJ/kg ± 1 MJ/kg), the recycling industry further reduces its environmental impact, aligning with international carbon neutrality goals (such as the EU Green Deal) and circular economy policies.
The economic benefits of cemented carbide recycling are typically lower than primary refining costs (<50% ± 10%). For example, primary tungsten refining costs are approximately $30-40 ± $5/kg (including ore mining at $15-20/kg, smelting at $10-15/kg, and transportation at $5/kg), while recycling costs can be reduced to $15-20 ± $2/kg (crushing and sorting at $5-7/kg, chemical treatment at $8-10/kg, and purification at $2-3/kg). The economic benefits of recycling can be further improved through large-scale production (annual processing capacity >10,000 ± 1,000 t) and process optimization (e.g., reducing energy consumption by 10% ± 1%, saving 50 kWh/t ± 5 kWh/t). In addition, recycled materials can be directly used for remanufacturing (e.g., extending cutting tool life by 20% ± 2% and improving wear resistance by 15% ± 2%), reducing raw material procurement expenses (savings > 20% ± 2%), and enhancing corporate competitiveness, especially in major cemented carbide consuming markets such as China (annual demand of 100,000 tons ± 10,000 tons), Germany (annual demand of 50,000 tons ± 5,000 tons), and the United States (annual demand of 40,000 tons ± 4,000 tons).
However, the cemented carbide recycling process also faces the following challenges:
Challenges of cemented carbide recycling – composition complexity
Cemented carbide is usually composed of tungsten carbide (WC, >85% ± 1%) and cobalt (Co, 6%-15% ± 1%), and contains trace additives (such as VC 0.5%-1% ± 0.1%, TaC 0.3%-0.8% ± 0.1%, TiC 0.2%-0.5% ± 0.1%). The different ratios of these additives in different products make recycling and separation more difficult. For example, aerospace-grade cemented carbide may contain TaC 0.5% ± 0.05% to improve high-temperature performance (temperature resistance > 1200°C ± 20°C), while general-purpose cutting tools may contain VC 0.8% ± 0.1% to inhibit grain growth (grain size < 0.5 μm ± 0.05 μm). Targeted adjustments are required for the acid leaching concentration (HNO₃ 25-30 mol/L ± 0.1 mol/L) or electrolysis parameters (current density 50-200 A/m² ). ± 10 A/m² ) .
Challenges of cemented carbide recycling – impurity control
. Impurities such as iron (Fe, >50% ± 5% from equipment wear, such as ball mill balls), nickel (Ni, <0.005% ± 0.0005% from the oxide layer on the surface of scrap), copper (Cu, <0.002% ± 0.0002% from electrolysis by-products), and silicon (Si, <0.001% ± 0.0001% from sorting equipment) may be introduced during the recycling process. If the content exceeds <0.01% ± 0.001%, the performance of the recycled material will be degraded (e.g., hardness <2200 HV ± 50 HV, wear rate >0.05 mm³ / N · m ± 0.005 mm³ / N · m, fracture toughness K₁c <10 MPa·m¹ / ² ± 0.5 MPa·m¹ / ² ) . Impurity sources also include surface oxidation of waste materials (O content >0.2% ± 0.05%, affecting sintering density) and secondary contamination (particle surface adsorption >0.1% ± 0.01%), requiring multi-stage purification to ensure product quality.
The recycling process consumes high amounts of energy (> 500 kWh/t ± 50 kWh/t), primarily in pickling (heating energy >200 kWh/t ± 20 kWh/t, 60-110°C ± 5°C), melting (>250 kWh/t ± 30 kWh/t, 1600-1800°C ± 50°C), and sorting (>50 kWh/t ± 5 kWh/t, airflow 5-10 m/s ± 0.5 m/s). This high energy consumption increases operating costs (approximately 40% ± 5% of total costs) and poses challenges to carbon footprint management (CO₂ emissions >0.5 t ± 0.05 t per tonne). Energy-saving technologies (e.g., high-efficiency electrolyzers with energy conversion efficiency >85% ± 2%) and process optimization (e.g., shortening pickling time by 10% ± 2%, lowering temperature by 5°C ± 1°C, saving 20 kWh/t ± 2 kWh/t) are needed to reduce energy consumption.
This section discusses in detail the three aspects of recycled resource value, environmental benefits and technical challenges.
16.1.1.1 Resource Value of Cemented Carbide Recycling: Tungsten and Cobalt
Tungsten (WC content >85% ± 1%) and cobalt (Co content 6%-15% ± 1%) in cemented carbide are high-value resources, and their recovery is of significant strategic importance. Tungsten reserves in the Earth’s crust are extremely rare (<0.1% ± 0.01%), with proven global reserves estimated at 3.1 million tons ± 50,000 tons, primarily distributed in China (1.8 million tons ± 50,000 tons, accounting for 60% ± 5% of global reserves), Russia (500,000 tons ± 20,000 tons), and Canada (300,000 tons ± 10,000 tons). Tungsten’s scarcity makes it a strategic metal, subject to international trade restrictions (such as the EU Critical Raw Materials Directive), mining depths (>500 m ± 50 m), and environmental regulations. This results in high primary mining costs (>30 USD/kg ± 5 USD/kg, including 15-20 USD/kg for ore extraction, 10-15 USD/kg for smelting, and 5 USD/kg for transportation). Cobalt reserves are even lower (<0.01% ± 0.001%), with global reserves estimated at approximately 7 million tons ± 50,000 tons, of which the Democratic Republic of the Congo accounts for 60% ± 5%. Affected by geopolitical risks (such as civil unrest and export bans) and supply chain disruptions, prices fluctuate significantly (over the past five years, the fluctuation range has been >50%, reaching a maximum of 80,000 USD/t ± 5,000 USD/t, and the average price fluctuation range from 2020 to 2025 is 30,000-80,000 USD/t ± 2,000 USD/t). The recycling process separates tungsten and cobalt using the following methods:
Cemented Carbide Recovery – Acid Leaching
The acid leaching method for cemented carbide recycling is a metal recovery process based on chemical dissolution. It is widely used to extract valuable metal components such as tungsten, cobalt, and nickel from scrap cemented carbide materials. Cemented carbide is primarily composed of a sintering process using a high-hardness, high-wear-resistant tungsten carbide (WC) skeleton and cobalt (Co) or nickel (Ni) as a binder phase. Its unique properties make it widely used in cutting tools, molds, and wear-resistant components. However, at the end of its useful life, if these waste materials are not recycled, they will result in resource waste and environmental pollution. The acid leaching method uses an acidic solution (such as nitric acid HNO₃ , sulfuric acid H₂SO₄ , or hydrochloric acid HCl) to chemically react with the metal binder phase, dissolving it into soluble salts (such as cobalt sulfate CoSO₄ ) , thereby achieving metal separation and extraction. The specific process involves pre-treating the scrap carbide, such as crushing and cleaning to remove surface oil and impurities. The treated material is then placed in an acidic solution, where reaction conditions, such as temperature (typically between 50-90°C), acid concentration (10%-20%), and immersion time (1-6 hours), are controlled to optimize metal dissolution efficiency. The metal ion-containing solution and the incompletely dissolved tungsten carbide residue are then separated by filtration. Finally, metal compounds (such as ammonium tungstate or cobalt salts) are purified and recovered through precipitation, solvent extraction, or electrolysis. The resulting acidic wastewater is neutralized to meet environmental emission standards. This method is favored for its relative simplicity, low equipment requirements, and ability to effectively recover precious metals (such as cobalt) from the binder phase, particularly in China, where tungsten resources are relatively scarce. However, acid leaching also has limitations. For example, the recovery rate of tungsten carbide is typically only 60%-70%, and the reaction generates a considerable amount of acidic wastewater. Improper handling can pollute the environment and increase wastewater treatment costs. In addition, modern technologies such as ultrasonic-assisted acid leaching are being introduced to improve reaction efficiency and recovery rate, thereby further optimizing the sustainability of the process. Overall, acid leaching, as a mainstream technology for cemented carbide recycling, plays an important role in resource recycling and industrial production. It is particularly suitable for processing large amounts of waste tool and abrasive materials. This method continues to develop and be applied in the industry.
Alkali leaching method for cemented carbide recovery
The alkaline leaching method for cemented carbide recycling is a recycling process based on a chemical reaction in an alkaline solution. It aims to extract the main metal components, such as tungsten, cobalt, and nickel, from scrap cemented carbide materials to achieve resource recycling. Cemented carbide is typically made by high-temperature sintering of tungsten carbide (WC) as a hard phase and cobalt (Co) or nickel (Ni) as a binder phase. Due to its excellent hardness and wear resistance, it is widely used in cutting tools, molds, and wear-resistant parts. However, at the end of its life cycle, if these waste materials are not recycled, they will lead to resource waste and environmental burden. The alkaline leaching method mainly uses a strong alkaline solution (such as sodium hydroxide NaOH) to react with tungsten carbide under high temperature and pressure conditions, decomposing it into soluble tungstates (such as sodium tungstate Na₂WO₄ ) . At the same time, the binder phase metal (such as cobalt) partially dissolves or remains in the solid phase. The specific process involves pre-treating the scrap carbide, such as mechanically crushing and cleaning to remove surface oil and impurities. The treated material is then placed in an alkaline solution, typically at 100-200°C and 1-2 MPa for several hours, to promote the decomposition of tungsten carbide. The tungsten-containing alkaline solution and undissolved metal residue are then separated by filtration. High-purity tungsten compounds (such as ammonium metatungstate) are then recovered from the solution through acidification, ion exchange, or evaporative crystallization, while the residue can be further processed to extract cobalt or nickel. Finally, the resulting wastewater is neutralized and treated to meet environmental standards. This method offers significant advantages in tungsten resource recovery due to its efficient decomposition of tungsten carbide, with tungsten recovery rates reaching 80%-90%, making it particularly suitable for major tungsten-producing countries such as China. However, alkaline leaching also faces challenges, such as requiring high reaction conditions (high temperature and pressure), high equipment investment and operating costs, and relatively low binder metal recovery efficiency (typically less than 50%). Furthermore, the wastewater generated is difficult to handle and may have potential environmental impacts. In recent years, combined with the development of microwave heating or ultrasonic-assisted technologies, alkaline leaching is being optimized to improve efficiency and reduce energy consumption. Overall, as an important technical path for cemented carbide recycling, alkaline leaching has performed well in the efficient recovery of tungsten, especially in the treatment of complex multiphase waste.
Electrochemical method for cemented carbide recovery
The electrochemical method for recycling cemented carbide is an advanced process that utilizes electrochemical reactions to extract metal components (such as tungsten, cobalt, and nickel) from scrap cemented carbide materials. It is widely used in resource recycling. Cemented carbide is primarily manufactured by sintering tungsten carbide (WC) as a hard phase and cobalt (Co) or nickel (Ni) as a binder phase. Due to its exceptional hardness, wear resistance, and high-temperature performance, it is widely used in cutting tools, molds, and wear-resistant components. However, at the end of its useful life, unrecycled cemented carbide waste leads to resource waste and environmental pressure. The electrochemical method applies an electric field to an electrolyte solution, causing the scrap cemented carbide to act as electrodes for a redox reaction, thereby achieving selective dissolution and separation of the metals. The specific process involves pre-treating the cemented carbide scrap, such as mechanical crushing and cleaning to remove oil and impurities to ensure a clean surface. The scrap is then placed in an electrolytic cell containing an electrolyte (such as sulfuric acid or sodium chloride solution) as the anode. The cathode is typically made of an inert material (such as graphite or stainless steel). Electrolysis is carried out at a constant current or voltage (typically 1-5V, with a current density of 0.1-1 A/cm² ) . The reaction temperature is typically controlled between 20-60°C. During this process, the binder metal (such as cobalt) is preferentially oxidized and dissolved into the solution, while tungsten carbide, due to its chemical stability and low solubility, is partially retained or requires subsequent treatment. After the electrolysis is completed, the metal ions in the solution are separated by filtration, and high-purity metals (such as cobalt salts or tungstates) are recovered by precipitation, extraction, or electrolysis. The electrolytic wastewater is also treated to meet environmental standards. This method has the advantages of high selectivity, relatively controllable energy consumption and low environmental impact. The cobalt recovery rate can reach 70%-90%, and the tungsten recovery rate can be increased to 60%-80% through optimization. It also avoids the generation of large amounts of acid and alkali waste liquid in traditional acid leaching or alkaline leaching methods. However, the electrochemical method also has some limitations, such as the high initial investment in equipment, the need for precise control of parameters during the electrolysis process to avoid side reactions, and is only suitable for small and medium-scale waste recycling. The processing efficiency of complex multiphase alloys may be limited. In recent years, combined with pulsed electric field or ultrasonic assisted technology, the electrochemical method is being further improved to increase recovery rates and reduce costs.
The combined application of these methods ensures effective resource recovery and alleviates pressure on primary resource supply. By 2024, global tungsten recycling will reach approximately 30,000 tonnes ± 500 tonnes, accounting for 10% ± 1% of total demand, and cobalt recycling will reach approximately 12,000 tonnes ± 200 tonnes, accounting for 8% ± 1% of total demand. This significantly reduces reliance on primary mining (mining reduction >50% ± 5%) and supports the cemented carbide industry’s transition to sustainable development.
16.1.1.2 Environmental Benefits: Reducing Mining and Waste Emissions
Cemented carbide recycling significantly reduces the environmental burden. Traditional primary mining involves large-scale mining and ore processing, generating significant amounts of waste and greenhouse gas emissions. For example, tungsten mining produces approximately 20-30 t ± 2 t of CO₂ per ton of ore ( excavation: 10-15 t/t ± 1 t/t, transportation: 5-7 t/t ± 0.5 t/t, and smelting: 5-8 t/t ± 0.5 t/t). Waste slag emissions are >50 t ± 5 t (containing >1000 ppm ± 100 ppm of heavy metals), and tailings accumulation accounts for 5% ± 0.5% of global industrial solid waste. Recycling cemented carbide waste (such as used tools, worn dies, and failed coatings) can reduce mining volume (>50% ± 5%, equivalent to reducing the mining of 1 million tonnes ± 100,000 tonnes of ore annually), thereby reducing land destruction (reducing the mining area by >1000 km² ). ± 100 km² , about 0.1% of the world’s arable land area) and water pollution (such as heavy metal leakage reduced by >60% ± 5%, tungsten concentration reduced from >500 ppm to <50 ppm ± 5 ppm, and cobalt concentration reduced from >200 ppm to <20 ppm ± 2 ppm).
Specifically, the recycling process reduces CO₂ emissions by >30% ± 5% compared to primary refining. For example, recycling 1,000 tons of scrap cemented carbide reduces CO₂ emissions by approximately 25,000 tons ± 2,500 tons, equivalent to the annual emissions of 5,000 gasoline-powered vehicles (5 tons ± 0.5 tons per vehicle). This reduction is due to the avoidance of high-carbon processes such as ore mining (energy consumption >2,000 MJ/t ± 200 MJ/t), transportation (fuel consumption >100 L/t ± 10 L/t, emissions approximately 0.3 tons/t ± 0.03 tons/t), and smelting (blast furnace energy consumption >1,500 kWh/t ± 100 kWh/t, emissions approximately 1-2 tons/t ± 0.1 tons/t). Waste emissions decreased by >40% ± 5%, reducing the risk of heavy metal migration into soil and water. For example, the tungsten content in waste liquid decreased from >500 ppm to <50 ppm ± 5 ppm, the cobalt content decreased from >200 ppm to <20 ppm ± 2 ppm, and the solid waste volume decreased from >50 t/t to <30 t/t ± 3 t/t.
The use of a closed recycling system and wastewater recycling technology further reduces environmental pollution. Through acid-base neutralization (pH 7 ± 0.2, reaction time 1-2 h ± 0.1 h) and membrane filtration (pore size 0.01 μm ± 0.001 μm, flux 50-100 L/m² · h ± 5 L/m² · h ), wastewater recovery rates exceed 90% ± 2%, and residual waste incineration yields a usable calorific value (>10 MJ/kg ± 1 MJ/kg, thermal efficiency >80% ± 2%), achieving resource recovery. By 2024, the global cemented carbide recycling industry will reduce waste emissions by approximately 2 million tons ± 200,000 tons, representing 10% ± 1% of total industrial solid waste. This represents a reduction of 50,000 hectares ± 5,000 hectares of land occupation, aligning with international circular economy policies (such as the EU’s Circular Economy Action Plan) and the carbon neutrality goal (net zero emissions by 2050).
16.1.1.3 Technical Challenges: Ingredient Complexity and Impurity Control (<0.01%)
The technical challenges facing cemented carbide recycling primarily lie in compositional complexity and impurity control. Cemented carbide has a diverse composition. In addition to WC (>85% ± 1%) and Co (6%-15% ± 1%), it often contains trace additives (such as VC 0.5%-1% ± 0.1%, TaC 0.3%-0.8% ± 0.1%, and TiC 0.2%-0.5% ± 0.1%). The varying proportions of these additives in different products increase the difficulty of recovery and separation. For example, aerospace-grade cemented carbide may contain TaC 0.5% ± 0.05% to improve high-temperature performance (temperature resistance > 1200°C ± 20°C, oxidation resistance > 90% ± 2%), while general-purpose cutting tools may contain VC 0.8% ± 0.1% to inhibit grain growth (grain size < 0.5 μm ± 0.05 μm, hardness > 2400 HV ± 50 HV). Targeted adjustments are required for pickling concentration (HNO₃ 25-30 mol/L ± 0.1 mol/L) or electrolysis parameters (current density 50-200 A/m² ). ± 10 A/m² , voltage 2-5 V ± 0.2 V).
Impurity control is another key challenge. During the recycling process, impurities such as iron (Fe, >50% ± 5% from equipment wear, such as ball mill Fe release rate >0.1% ± 0.01%/h), nickel (Ni, <0.005% ± 0.0005% from the oxide layer on the surface of the waste, NiO formation rate >0.05% ± 0.005%), copper (Cu, <0.002% ± 0.0002% from residual CuSO₄, a by-product of electrolysis ) , and silicon (Si, <0.001% ± 0.0001% from SiO₂ contamination in the sorting equipment ) may be introduced. If the content exceeds <0.01% ± 0.001%, the performance of the recycled material will be degraded (such as hardness <2200 HV ± 50 HV, wear rate >0.05 mm³ / N · m ± 0.005 mm³ / N · m , fracture toughness K₁c <10 MPa·m ¹ / ² ± 0.5 MPa·m ¹ / ² , thermal stability <800°C ± 20°C. Impurities also include waste surface oxidation (O content >0.2% ± 0.05%, affecting sintering density <99% ± 0.5%) and secondary contamination (particle surface adsorption >0.1% ± 0.01%, such as residual organic matter).
To address these challenges, a multi-stage purification process is required:
Physical sorting
Iron impurities were removed by magnetic separation (magnetic field strength 0.5-1 T ± 0.1 T, separation efficiency >95% ± 2%, magnetic field gradient >100 T/m ± 10 T/m), and large particles were removed by air flow separation (speed 5-10 m/s ± 0.5 m/s, pressure 0.05 MPa ± 0.01 MPa, particle settling time 1-2 s ± 0.1 s). The purity was improved to >99% ± 0.5%, and the residual Fe content was <0.005% ± 0.0005%.
Chemical purification
Ion exchange resin (exchange capacity 2-3 meq/g ± 0.1 meq/g, flow rate 5-10 mL/min ± 0.5 mL/min, resin regeneration cycle 50 h ± 5 h) was used to remove trace metal ions such as Fe ³ ⁺ (removal efficiency >98% ± 1%) and Ni ² ⁺ (removal efficiency >97% ± 1%); combined with solvent extraction (organic phase such as P507, extraction efficiency >98% ± 1%, phase ratio 1:1 ± 0.1), further purification was carried out, and the impurity content was reduced to <0.01% ± 0.001%, and the O content was <0.1% ± 0.01%.
Vacuum melting
at 1600-1800°C ± 50°C, pressure <10 ⁻³ Pa ± 10 ⁻ ⁴ Pa, and holding time is 2-3 h ± 0.2 h to volatilize impurities (such as Zn boiling point 907°C ± 10°C, Pb boiling point 1749°C ± 20°C) and improve material uniformity (grain deviation <0.05 μm ± 0.01 μm, grain boundary energy <1 J/m² ). ± 0.1 J/m² ) , ensuring the crystalline purity of the recycled material (XRD impurity <0.1% ± 0.01%).
In addition, the economic feasibility of recycling is limited by process energy consumption (>500 kWh/t ± 50 kWh/t), including acid leaching heating energy consumption of >200 kWh/t ± 20 kWh/t (temperature 60-110°C ± 5°C, thermal efficiency <70% ± 5%), smelting energy consumption of >250 kWh/t ± 30 kWh/t (arc power 100-150 kW ± 10 kW), and sorting energy consumption of >50 kWh/t ± 5 kWh/t (blower power 10-20 kW ± 1 kW). Energy consumption must be reduced through energy-saving equipment (such as high-efficiency electrolytic cells with energy conversion efficiencies >85% ± 2%, reducing power consumption by 20% ± 2%) and process optimization (such as shortening pickling time by 10% ± 2% to 1.8-3.6 h ± 0.2 h and lowering temperature by 5°C ± 1°C to 55-75°C ± 5°C, saving 20 kWh/t ± 2 kWh/t). China Tungsten Intelligent Manufacturing’s optimized vacuum melting technology (introducing induction heating, increasing efficiency by 10% ± 1%) and electrochemical parameters (increasing current efficiency by 5% ± 0.5%) have reduced total energy consumption by 8% ± 1% (to 460 kWh/t ± 50 kWh/t), setting a benchmark for the industry.
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