A method for preparing sintered returned ore cold-solidified balls by using retired fan blades

Abstract

The application discloses a method for preparing sintered returned ore cold-solidified balls by using retired fan blades. The method innovatively utilizes the sharp edge of sintered returned ore to efficiently break the fan blades, removes epoxy resin and retains glass fiber structure through phosphoric acid, and then modifies the surface activity through a silane coupling agent, so as to form a composite bonding system by matching liquid sodium silicate and pre-gelatinized cassava starch, thereby strengthening the strength of the pellets from both physical and chemical aspects. The method realizes high-value utilization of the retired fan blade solid waste, solves the problem of recycling of sintered returned ore, and prepares cold-solidified pellets meeting the smelting requirements of blast furnaces or hydrogen-based shaft furnaces, and the process has low energy consumption and low carbon emission, thereby providing an effective way for green and low-carbon transformation of steel enterprises.

Description

Technical Field

[0001] This invention belongs to the field of cold-bonded pellet preparation technology, specifically relating to a method for preparing sintered return ore cold-bonded pellets using decommissioned wind turbine blades. Background Technology

[0002] Sintering is a crucial link in the ironmaking technology chain, producing high-quality sinter that meets over 70% of the total energy demand for blast furnace smelting. However, this process is extremely energy-intensive, accounting for approximately 6-10% of the steel industry's total energy consumption. Sintered return ore, a major byproduct of the sintering process, accounts for 25-40% of the total sintered ore production. Directly using sintered return ore smaller than 5mm as blast furnace charge affects the permeability of the charge column. Currently, the main treatment is recycling it back into the sintering process. However, as the proportion of return ore increases, it leads to a deterioration in sinter quality indicators and an increase in CO2 emissions. Therefore, developing new low-carbon agglomeration technologies is an urgent need for the green transformation of steel enterprises.

[0003] Cold-consolidation pelletizing is a revolutionary pelletizing technology that enables the consolidation and shaping of iron-containing raw materials at temperatures ranging from room temperature to 300°C. It achieves cold-state mechanical strength that meets smelting requirements through the interfacial interaction between the binder and the raw material. Current technologies often employ inorganic-organic composite binders to enhance the strength of cold-consolidated pellets from sintered return ore, but these technologies still suffer from insufficient mechanical strength and low utilization of solid waste resources.

[0004] On the other hand, my country's first batch of wind turbines has entered its peak decommissioning period. Between 2025 and 2030, the annual amount of scrapped wind turbine blades will reach 300,000 to 500,000 tons, mainly composed of 70-80% reinforcing fibers (primarily glass fiber) and 20-30% resin matrix (primarily epoxy resin). Currently, the recycling of decommissioned wind turbine blades mainly focuses on physical crushing to recover glass fiber, lacking high-value-added utilization methods. However, fiber materials have been proven in industry to effectively improve material strength; for example, combining glass fiber with resin plastics can significantly improve the material's strength, stiffness, and impact toughness.

[0005] Among existing patents, CN118950671A discloses a method for physical crushing and recycling retired wind turbine blades, but does not involve high-value-added utilization; CN120060636A enhances pellet strength through modified sintered return ore, but does not involve composite binder strengthening; CN118531208A uses steel slag and dust to prepare cold-bonded pellets, but does not involve the synergistic utilization of sintered return ore and retired wind turbine blades. Therefore, there is an urgent need to develop an integrated technology that can simultaneously solve the problems of recycling sintered return ore, high-value-added recycling of retired wind turbine blades, and strengthening of cold-bonded pellets. Summary of the Invention

[0006] This invention aims to solve three core problems existing in the prior art: First, excessive recycling of sintered ore leads to a decline in sintering quality and an increase in carbon emissions; second, retired fan blades lack high-value-added utilization methods, resulting in waste of solid waste resources; and third, the mechanical strength of cold-bonded pellets from sintered ore is insufficient, making it difficult to meet the smelting requirements of blast furnaces or hydrogen-based vertical shaft furnaces.

[0007] To achieve the above objectives, the present invention provides a method for preparing sintered return ore cold-bonded pellets using decommissioned wind turbine blades, characterized by comprising the following steps: Step 1: Pre-crush the retired wind turbine blades to obtain wind turbine blade particles with a particle size of less than 5mm; Step 2: Mix the wind turbine blade particles with sintered return ore and perform co-grinding treatment. Use the sharp edges of the sintered return ore to shear and crush the epoxy resin and glass fiber in the wind turbine blade particles. Step 3: Add phosphoric acid solution to the co-ground mixture for acid etching to remove epoxy resin. After washing, add silane coupling agent solution to activate and modify the sintered return ore and glass fiber surface in the mixture, followed by drying. After treatment with phosphoric acid solution, the epoxy resin in the wind turbine blade powder is removed, and the glass fiber structure in the blade is uniformly attached and fixed in the porous structure of the sintered return ore, which is more conducive to the uniform distribution of the fiber structure and its reaction with alkaline sodium silicate. The main principle is: the reaction formula of epoxy resin and phosphoric acid is R-epoxy group + H3PO4 → R'-O-PO(OH)2 + R'-OH. Phosphoric acid reacts with the epoxy group of epoxy resin to generate soluble resin-bonded phosphate monoesters and alcohol hydroxyl groups, thereby removing epoxy resin from the decommissioned wind turbine blade powder while retaining the glass fiber structure.

[0008] Physically, the glass fibers retain their fibrous structure after grinding and are uniformly distributed within the cold-bonded pellets, forming a three-dimensional network fiber structure, which significantly improves the compressive strength of the cold-bonded dry pellets. Chemically, liquid sodium silicate is composed of (SiO4). 4- It is composed of tetrahedral units, while glass fiber is essentially composed of active SiO2. When mixed with sodium silicate, the OH groups in the alkaline environment of sodium silicate... - It reacts chemically with glass fiber to form (SiO4). 4- Tetrahedral units, which significantly improve the concentration of (SiO4) in sodium silicate solution. 4- Density can promote (SiO4) 4- It forms Fe-O-Si bonds with sintered return ore and increases (SiO4) content. 4- The strength of the three-dimensional network structure formed after dehydration and condensation. Macroscopically, the addition of glass fiber significantly enhances the compressive strength of the dry pellets in the sintered return ore cold-consolidated pellets.

[0009] Step 4: Mix the modified mixture obtained in Step 3 with inorganic binder, organic binder and water to obtain briquetting mixture, and then press it into cold-bonded green pellets. Step 5: Use industrial low-temperature waste gas to dry and solidify the cold-consolidated green pellets to obtain cold-consolidated dry pellets.

[0010] Furthermore, in step four, the inorganic binder is liquid sodium silicate, the organic binder is pregelatinized cassava starch, and the glass fiber in the modified mixture serves as a reinforcing agent; the amount of the inorganic binder added is 1-5% of the mass of the modified mixture, and the amount of the organic binder added is 0.5-2% of the mass of the modified mixture. The core active ingredient of the liquid sodium silicate is (SiO4). 4- The tetrahedral unit can undergo a dehydration condensation reaction with the Fe-OH groups naturally present on the surface of the sintered return ore to form stable Fe-O-Si covalent bonds (such as...). Figure 2 As shown in the figure, this chemical bond is the core source of the dry pellet compressive strength and hot strength during high-temperature smelting of cold-consolidated pellets, ensuring the structural integrity of the pellets in the high-temperature environment of blast furnaces or hydrogen-based vertical shaft furnaces. When the amount of liquid sodium silicate added is less than 1%, (SiO4) 4- Insufficient tetrahedral unit concentration prevents sufficient bonding with the active sites on the surface of sintered return ore and glass fibers, resulting in a limited number of Fe-O-Si bonds and reduced dry pellet compressive strength. When the addition exceeds 5%, excessive sodium silicate leads to excessive viscosity during pellet forming, causing it to adhere to the roller surface of the briquetting machine and affecting forming efficiency. Simultaneously, excessive sodium silicate generates significant shrinkage stress during drying due to moisture evaporation, leading to microcracks inside the pellets and further reducing compressive strength. In addition, excessive addition increases raw material costs.

[0011] Pregelatinized cassava starch has undergone pre-gelatinization and dissolves rapidly in water at room temperature, forming a highly viscous colloidal solution. This eliminates the need for additional heating for gelatinization, perfectly suited to the low-temperature molding process of cold solidification. It avoids the energy loss associated with high-temperature activation of ungelatinized starch. Unlike liquid sodium silicate, which focuses on dry pellet compressive strength and hot strength, the core function of pregelatinized cassava starch is to enhance the drop strength of green pellets through liquid bridging and polymer film solidification. The dissolved starch colloid forms flexible liquid bridges between sintered return ore and glass fiber particles, initially binding loose particles through adhesion and hydrogen bonds. After green pellet formation, low-temperature flue gas drying causes the starch colloid to gel and solidify, forming a rigid polymer film that fills the tiny gaps between particles, enhancing the compressive strength of the dry pellets. When the amount of pregelatinized cassava starch added is less than 0.5%, the number of liquid bridges and polymer films formed by the starch colloid is insufficient, resulting in weak adhesion between green pellet particles and substandard drop strength, failing to meet the requirements for pellet transportation. When the amount added exceeds 2%, excessive starch will leave a lot of organic components inside the pellets. During blast furnace smelting, these organic materials will burn rapidly to produce a large amount of gas, causing pores to form inside the pellets and reducing their hot strength.

[0012] Furthermore, in step three, the silane coupling agent is KH-550. The core of the modification of the silane coupling agent in the sintered return ore-glass fiber system lies in its bidirectional reactive molecular structure, which establishes chemical bridges and increases the density of surface active sites on the surfaces of the sintered return ore and glass fiber. This lays the foundation for the subsequent strong bonding effect with the composite binder. For details on the principle, please refer to [link / reference needed]. Figure 3The molecular structure of KH-550 contains two types of functional groups: one end is a hydrolyzable alkoxy group, and the other end is an amino group containing active hydrogen. The three alkoxy groups in the KH-550 molecule undergo hydrolysis in an aqueous medium, generating silanol groups (-Si-OH) and ethanol (a byproduct). Some of the silanol groups generated by hydrolysis undergo slight self-condensation to form oligomeric siloxanes (still retaining a large number of unreacted silanol groups). Their molecular chain structure makes them more readily interact with the hydroxyl groups on the surface of sintered return ore and glass fibers. After phosphoric acid treatment, the surface state of the sintered return ore and glass fibers provides a reaction basis for modification. The surface of the sintered return ore mainly consists of iron oxides, and naturally contains a large number of hydroxyl groups (Fe-OH). Phosphoric acid treatment does not destroy these hydroxyl groups; instead, due to the increased particle surface area, it exposes more Fe-OH active sites. Phosphoric acid on the glass fiber surface completely removes the epoxy resin, fully exposing the core active SiO2 component. The SiO2 surface forms silanol groups (Si-OH) due to the adsorption of water molecules. At this point, the hydrolyzed KH-550 achieves a strong bond with both through bidirectional bonding: bonding with the sintered return ore: the silanol groups (-Si-OH) generated by the hydrolysis of KH-550 undergo a dehydration condensation reaction with the Fe-OH on the surface of the sintered return ore to form stable Si-O-Fe covalent bonds; bonding with the glass fiber: similarly, the silanol groups of KH-550 undergo a dehydration condensation reaction with the Si-OH on the surface of the glass fiber to form Si-O-Si covalent bonds. Through this process, the KH-550 molecule acts as a chemical bridge, firmly connecting the sintered return ore particles and the glass fiber. At the same time, the amino groups at the end of its molecules introduce new polar groups into the system, further enhancing surface activity.

[0013] Furthermore, in step two, the mixing mass ratio of the fan blade particles to the sintered return ore is (10-30):(970-990).

[0014] Furthermore, in step two, the co-grinding process is carried out in a rotating drum with a diameter of 30-50 cm, a grinding speed of 10-50 r / min, and a grinding time of 50-90 min. After co-grinding, the epoxy resin and glass fiber in the mixture are broken down to below 0.1 mm.

[0015] Furthermore, in step three, the concentration of the phosphoric acid solution is 40-50%; the amount of phosphoric acid solution added per kilogram of co-ground mixture is 50-150 mL, the stirring speed during acid etching is 200-500 r / min, and the stirring time is 10-60 min.

[0016] Furthermore, in step three, the silane coupling agent solution is prepared by mixing the silane coupling agent, anhydrous ethanol, and deionized water in a volume ratio of 1:1:3; the amount of silane coupling agent added is 20 mL per kilogram of the mixture after co-grinding and acid etching and washing.

[0017] Furthermore, in step three, the drying temperature is 60-150℃.

[0018] Furthermore, in step four, the pressing and forming process uses a double-roller briquetting machine with a forming pressure of 20-50 MPa.

[0019] Furthermore, in step five, the industrial low-temperature waste gas is sintering flue gas or sintering ring-cooled flue gas; the temperature of the waste gas is 100-180℃, and the flow velocity is 20000-50000 m / s. 3 The drying and consolidation time is 2-6 hours, with a moisture content of 1-5 wt%.

[0020] The beneficial effects of this invention are: High-value synergistic utilization of solid waste breaks the industry's disposal dilemma: sintering return ore, which accounts for 25-40% of the total sintering output, is converted into qualified blast furnace feed, and retired fan blades are converted into pellet strength enhancers. The utilization rate of these two types of solid waste is significantly improved, completely changing the current situation of deteriorating sintering return ore recycling and low-value recycling of retired fan blades, and achieving a high-value-added breakthrough in solid waste resource utilization.

[0021] The strength of cold-bonded pellets is significantly improved, meeting the core requirements of smelting: Through the synergistic effect of physical support, chemical consolidation and toughness supplementation, the comprehensive performance of the prepared cold-bonded pellets is significantly better than the compressive strength of existing technologies, solving the core pain point of insufficient strength of traditional cold-bonded pellets.

[0022] Its low-carbon and environmentally friendly advantages are prominent, which helps green transformation: the solidification temperature ranges from room temperature to 300℃, which significantly reduces energy consumption and CO2 emissions compared with the traditional sintering and pelletizing process; at the same time, it reuses industrial low-temperature waste gas as a drying heat source, which reduces waste gas emissions and requires no additional energy input, meeting the core needs of steel companies for green and low-carbon transformation.

[0023] It has strong process adaptability and industrial promotion value: all raw materials (including iron resources and binders) are widely available and inexpensive; the process steps are simple and do not require special high-end equipment. Roller briquetting machines, spiral dryers and other equipment are conventional equipment already in use by steel companies. The forming pressure and drying parameters are easy to control and can be directly integrated into the existing production process. The promotion cost is low and the feasibility is high.

[0024] Excellent smelting compatibility ensures stable ironmaking process: Pregelatinized cassava starch is used as an organic binder, which can be completely burned without residue during smelting. The solidified structure formed by the inorganic binder and glass fiber is stable at high temperature, avoiding pellet breakage that affects the permeability of the blast furnace charge. At the same time, the pellet size is uniform, meeting the process requirements of automated batching and blast furnace smelting, ensuring the stability and efficiency of the ironmaking process. Attached Figure Description

[0025] Figure 1 This invention describes the process of crushing, removing impurities, and modifying retired wind turbine blades.

[0026] Figure 2 This invention describes the adsorption mechanism of sodium silicate on the surface of sintered return ore.

[0027] Figure 3 This is the modification mechanism between the silane coupling agent and the sintered recycled ore-glass fiber in this invention. Detailed Implementation

[0028] The technical solution of the present invention will be described in detail below through specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0029] Example 1: Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 100 mL of 45% phosphoric acid solution to the co-ground mixture, stir at 300 r / min for 30 min, and after the epoxy resin is fully dissolved, wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0030] Example 2: Raw material preparation: Weigh 10g of decommissioned fan blade particles pre-crushed to less than 5mm and 990g of sintered return ore at a mass ratio of 10:990, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 30cm and ground at a speed of 10r / min for 50min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 50 mL of 40% phosphoric acid solution to the co-ground mixture, stir at 200 r / min for 10 min to fully dissolve the epoxy resin, and then wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 80°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 1% of liquid sodium silicate (50% solid content), 0.5% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green briquettes under a molding pressure of 20 MPa. Drying and consolidation: The cold-consolidated green pellets are placed in a spiral dryer and purged with air at a temperature of 120℃ and a flow rate of 20,000 m / s. 3 Cold flue gas with a moisture content of 1 wt% and a sintering ring of 1 h was dried and solidified for 2 h to obtain cold-solidified pellets.

[0031] Example 3: Raw material preparation: Weigh 30g of decommissioned fan blade particles pre-crushed to less than 5mm and 970g of sintered return ore at a mass ratio of 30:970, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 50cm and ground at a speed of 50r / min for 90min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 150 mL of 50% phosphoric acid solution to the co-ground mixture, stir at 500 r / min for 60 min to fully dissolve the epoxy resin, and then wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 150°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 5% of liquid sodium silicate (50% solid content), 2% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green briquetting pellets under a molding pressure of 50MPa. Drying and consolidation: The cold-consolidated green pellets are placed in a spiral dryer and purged with air at a temperature of 180℃ and a flow rate of 50,000 m / s. 3 Sintering flue gas with a moisture content of 5wt% was dried and solidified for 6 hours to obtain cold-solidified pellets.

[0032] Example 4: Raw material preparation: Weigh 30g of decommissioned fan blade particles pre-crushed to less than 5mm and 970g of sintered return ore at a mass ratio of 30:970, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 100 mL of 45% phosphoric acid solution to the co-ground mixture, stir at 300 r / min for 30 min, and after the epoxy resin is fully dissolved, wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Cold flue gas with a sintering ring and a moisture content of 3wt% was dried and solidified for 4 hours to obtain cold-solidified pellets.

[0033] Example 5: Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 100 mL of 45% phosphoric acid solution to the co-ground mixture, stir at 300 r / min for 30 min, and after the epoxy resin is fully dissolved, wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and consolidation: The cold-consolidated green pellets are placed in a spiral dryer and purged with air at a temperature of 180℃ and a flow rate of 50,000 m / s. 3 Sintering flue gas with a moisture content of 5wt% was dried and solidified for 6 hours to obtain cold-solidified pellets.

[0034] Comparative Example 1 Raw material preparation: Weigh 1000g of sintered return ore, without adding any decommissioned fan blades; No co-grinding: The sintered return ore is directly used in subsequent steps; Phosphoric acid-free purification: No need to add phosphoric acid solution for acid etching; No activation modification treatment: No modification with silane coupling agent KH-550 is performed; Preparation of briquetting mixture: Take 1000g of sintered return ore, add 3% of liquid sodium silicate (50% solid content) of sintered return ore by mass, 1% of pregelatinized cassava starch and appropriate amount of water, stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0035] Comparative Example 2 Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture, without co-grinding treatment, and add directly; Phosphoric acid purification treatment: Add 100 mL of 45% phosphoric acid solution to the mixture, stir at 300 r / min for 30 min to fully dissolve the epoxy resin, and then wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0036] Comparative Example 3 Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid-free purification treatment: Direct activation and modification are performed without adding phosphoric acid solution to dissolve the epoxy resin; Activation and modification treatment: Add 20 mL of silane coupling agent KH-550 per kilogram of co-ground mixture to prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3. Mix the solution thoroughly with the mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0037] Comparative Example 4 Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification treatment: Add 100 mL of 45% phosphoric acid solution to the co-ground mixture, stir at 300 r / min for 30 min to fully dissolve the epoxy resin, wash with deionized water until neutral, place in an oven and dry at 100℃ to constant weight to obtain unmodified mixture without silane coupling agent treatment. Preparation of briquetting mixture: Take 1000g of unmodified mixture, add 3% of liquid sodium silicate (50% solid content), 1% of pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0038] Comparative Example 5 Raw material preparation: Weigh 20g of decommissioned fan blade particles pre-crushed to less than 5mm and 980g of sintered return ore at a mass ratio of 20:980, mix them evenly to obtain 1kg of mixture; Co-grinding treatment: The mixture is placed in a cylindrical drum with a diameter of 40cm and ground at a speed of 20r / min for 60min to break the epoxy resin and glass fiber in the mixture to below 0.1mm; Phosphoric acid purification: Add 100 mL of 45% phosphoric acid solution to the co-ground mixture, stir at 300 r / min for 30 min, and after the epoxy resin is fully dissolved, wash with deionized water until neutral. Activation and modification treatment: Prepare a mixed solution of silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3 by adding 20 mL of silane coupling agent KH-550 per kilogram of washed mixture. Mix the solution thoroughly with the washed mixture and dry it in an oven at 100°C until constant weight to obtain the modified mixture. Preparation of briquetting mixture: Take 1000g of modified mixture, add 5% cement to replace liquid sodium silicate, 2% ordinary starch to replace pregelatinized cassava starch and appropriate amount of water, and stir evenly to obtain briquetting mixture; Compression molding: A double-roller briquetting machine is used to compress the briquetting mixture into uniformly sized cold-bonded green balls under a molding pressure of 30MPa. Drying and Consolidation: The cold-consolidated green pellets are placed in a spiral dryer and slurry is introduced at a temperature of 160℃ and a flow rate of 30,000 m / s. 3 Sintering flue gas with a moisture content of 3wt% and a volume of 0.5h was dried and solidified for 4h to obtain cold-solidified pellets.

[0039] Example and comparative experimental data: Table 1 Performance test data of the examples and comparative examples

[0040] The experimental data above show that, in Comparative Example 1, without fan blades, the dry-bulb compressive strength is only 1574.2 N / Pellet, far below the smelting requirement (>2000 N / Pellet); while in Example 1, due to the addition of modified glass fiber, the dry-bulb strength is increased by 47.2%. This demonstrates that the three-dimensional network structure of the glass fiber provides physical support, while the active SiO2 reacts with liquid sodium silicate to generate additional (SiO4). 4- Tetrahedral units promote the formation of Fe-O-Si bonds, achieving both physical and chemical strengthening.

[0041] In Comparative Example 2, without co-grinding, the dry ball compressive strength was 1841.6 N / Pellet, which did not meet the smelting requirements. In Example 1, co-grinding increased the strength by 25.8%. It can be seen that co-grinding utilizes the sharp edges of the sintered ore to shear the glass fibers to below 0.1 mm, increasing the specific surface area and ensuring uniform fiber dispersion. In contrast, in Comparative Example 2, the wind turbine blades were only broken to 5 mm, the fiber structure was not fully disintegrated, and the agglomeration phenomenon was obvious, making it impossible to form an effective support network.

[0042] In Comparative Example 3, without phosphoric acid for impurity removal, the prepared green pellets had a drop strength of only 3.6 times / Pellet and a dry pellet strength of 1363.4 N / Pellet, failing to meet all performance standards. In Example 1, the strength was significantly improved due to the removal of epoxy resin. It is evident that the remaining epoxy resin coats the glass fibers and the surface of the sintered return ore, hindering the contact between the binder and the active sites, leading to consolidation failure. Phosphoric acid directionally removes the epoxy resin through a reaction, preserving the glass fiber structure.

[0043] In Comparative Example 4, without KH-550 modification, the compressive strength of the prepared dry balls was 1987.9 N / Pellet, close to but not meeting the smelting requirements; in Example 1, due to modification treatment, the strength increased by 16.6%. It can be seen that the silanol groups generated by the hydrolysis of KH-550 form Si-O-Fe and Si-O-Si covalent bonds with the Fe-OH of the sintered return ore and the Si-OH of the glass fiber, increasing the density of surface active sites and making the interfacial interaction between the binder and the raw materials stronger; while the surface hydroxyl density of Comparative Example 4 is insufficient, and the number of chemical bonds is limited.

[0044] In Comparative Example 5, the binder was replaced, and the drop strength of the prepared green balls was 5.2 times / Pellet, which just met the transportation requirements. The dry ball strength was 1763.8 N / Pellet, which did not meet the smelting requirements. In Example 1, because liquid sodium silicate and pregelatinized cassava starch were used, the performance fully met the standards.

[0045] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing sintered return ore cold-bonded pellets using decommissioned wind turbine blades, characterized in that, Includes the following steps: Step 1: Pre-crush the retired wind turbine blades to obtain wind turbine blade particles with a particle size of less than 5mm; Step 2: Mix the wind turbine blade particles with sintered return ore and perform co-grinding treatment. Use the sharp edges of the sintered return ore to shear and crush the epoxy resin and glass fiber in the wind turbine blade particles. Step 3: Add phosphoric acid solution to the co-ground mixture for acid etching to remove epoxy resin. After washing, add silane coupling agent solution to activate and modify the sintered return ore and glass fiber surface in the mixture, and then dry it. Step 4: Mix the modified mixture obtained in Step 3 with inorganic binder, organic binder and water to obtain briquetting mixture, and then press it into cold-bonded green pellets. Step 5: Use industrial low-temperature waste gas to dry and solidify the cold-consolidated green pellets to obtain cold-consolidated dry pellets.

2. The method according to claim 1, characterized in that, In step four, the inorganic binder is liquid sodium silicate, the organic binder is pregelatinized cassava starch, and the glass fiber in the modified mixture is used as a reinforcing agent; the amount of inorganic binder added is 1-5% of the mass of the modified mixture, and the amount of organic binder added is 0.5-2% of the mass of the modified mixture.

3. The method according to claim 1, characterized in that, In step three, the silane coupling agent is KH-550.

4. The method according to claim 1, characterized in that, In step two, the mixing mass ratio of the fan blade particles to the sintered return ore is (10-30):(970-990).

5. The method according to claim 1 or 4, characterized in that, In step two, the co-grinding process is carried out in a rotating drum with a diameter of 30-50 cm, a grinding speed of 10-50 r / min, and a grinding time of 50-90 min. After co-grinding, the epoxy resin and glass fiber in the mixture are broken down to below 0.1 mm.

6. The method according to claim 1, characterized in that, In step three, the concentration of the phosphoric acid solution is 40-50%; the amount of phosphoric acid solution added per kilogram of co-ground mixture is 50-150 mL, the stirring speed during acid etching is 200-500 r / min, and the stirring time is 10-60 min.

7. The method according to claim 1 or 3, characterized in that, In step three, the silane coupling agent solution is prepared by mixing silane coupling agent, anhydrous ethanol and deionized water in a volume ratio of 1:1:3; the amount of silane coupling agent added is 20 mL per kilogram of the mixture after co-grinding and acid etching and washing.

8. The method according to claim 1, characterized in that, In step three, the drying temperature is 60-150℃.

9. The method according to claim 1, characterized in that, In step four, the pressing and forming process uses a double-roller briquetting machine with a forming pressure of 20-50 MPa.

10. The method according to claim 1, characterized in that, In step five, the industrial low-temperature waste gas is sintering flue gas or sintering ring-cooled flue gas; the temperature of the waste gas is 100-180℃, and the flow velocity is 20000-50000 m / s. 3 The drying and consolidation time is 2-6 hours, with a moisture content of 1-5 wt%.

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