Liquid binder for disc granulation of fine iron powder as well as preparation method and application of liquid binder

Abstract

The invention belongs to the technical field of preparation of binders, and particularly relates to a liquid binder for disc granulation of fine iron powder and a preparation method and application of the liquid binder. The invention provides a liquid binder for disc granulation of fine iron powder in order to reduce the use amount of bentonite in the binder for disc granulation of fine iron powder and improve the strength of green iron ore pellets and after roasting. The raw materials comprise a material A and a material B, wherein the material A comprises bisphenol A epoxy resin 6101 type, epoxy resin 711 type, tetrahydrofuran, dibutyl phthalate, dodecylphenol polyoxyethylene ether OP-10 type, polyvinyl alcohol 2488 type, isobutanol, silica fume, sodium carbonate and water; and the material B is polyamide resin 200 type. Through the synergistic effect of cross-linking curing of epoxy resin and high-temperature pore forming of silica fume-sodium carbonate, the use amount of bentonite is reduced, the binding force of a binding agent is increased, the particle size of pellets is made to be uniform, the pelletizing rate and the strength of the pellets after roasting are improved, the iron grade of the pellets after roasting is improved, and the reducibility of the pellets after roasting is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of binder preparation, and in particular relates to a liquid binder for iron ore concentrate disc granulation, a preparation method and an application thereof. Background Art

[0002] Pellets have excellent metallurgical properties. Their spherical shape reduces airflow resistance, improving the permeability of the upper blast furnace and boosting blast furnace productivity. Iron ore pellets are made by mixing iron ore concentrate with a binder and then using a disc pelletizer to create green balls. The green balls are then roasted. Only qualified iron ore pellets can be used in blast furnaces to make iron.

[0003] Binders are a key auxiliary raw material in the disc pelletizing process for producing iron ore pellets. They enhance the bonding between iron ore concentrate particles, improve pelletizing performance, increase the strength and thermal stability of both green and roasted pellets, and improve the metallurgical properties of the pellets. Therefore, their performance is directly related to the quality of the pellets, impacting both the economic and environmental benefits of metallurgical enterprises.

[0004] Currently, there are many binders for iron ore pellets, most of which are based on bentonite. However, for every 1 wt% of bentonite added during the pelletizing process, the iron grade of the pellets decreases by approximately 0.6 wt%, the blast furnace coke ratio increases by 1.2%, the iron content decreases by approximately 7 kg / t, and the yield decreases by 1.8%. Furthermore, high amounts of bentonite lead to low porosity and poor reducibility in the calcined pellets. Furthermore, these binders suffer from low bonding strength, low pellet formation rate, low green pellet strength, poor pellet strength after calcination, increased return material, and increased production costs for pellet production. Therefore, achieving partial or complete replacement of bentonite with binders is an important development direction for metallurgical pelletization. Summary of the Invention

[0005] In order to reduce the usage of bentonite in the binder used for iron ore concentrate disc granulation, improve the green pellet strength and the strength of the calcined pellets, and enhance the reducibility of the calcined pellets, the present invention provides a liquid binder for iron ore concentrate disc granulation, a preparation method and application thereof.

[0006] To achieve the above application objectives, the technical solutions adopted in this application are as follows: In a first aspect, the present invention provides a liquid binder for disc granulation of iron ore concentrate, the raw materials of which include material A and material B; The material A, calculated based on the total weight of the components being 100%, comprises: 10-15% of bisphenol A epoxy resin 6101, 10-15% of epoxy resin 711, 2-3% of tetrahydrofuran, 4-6% of dibutyl phthalate, 0.02-0.03% of dodecylphenol polyoxyethylene ether OP-10, 0.1-0.4% of polyvinyl alcohol 2488, 0.02-0.03% of isobutanol, 3-5% of silica fume, 3-5% of soda ash, and the balance being water; The material B is polyamide resin type 200, and the mass of the material B is 40-50% of the mass of bisphenol A epoxy resin type 6101.

[0007] Preferably, the total amount of the epoxy resin bisphenol A type 6101 + 711 is 20-30%.

[0008] Preferably, the mass ratio of tetrahydrofuran to isobutanol is (80-125):1.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned liquid binder, including the preparation of material A, the preparation method comprising the following steps: (1) Fully swell and mix bisphenol A epoxy resin 6101 and epoxy resin 711 with tetrahydrofuran and isobutyl alcohol, and stir evenly; then add dibutyl phthalate and dodecylphenol polyoxyethylene ether OP-10 emulsifier, and continue stirring to form an oil phase; (2) Dissolve polyvinyl alcohol 2488 in water, add silica fume and soda ash, and ball mill until D90 ≤ 10 μm to form an aqueous phase; (3) Add the oil phase to the water phase and emulsify to obtain material A.

[0010] Preferably, in step (1), the dissolution temperature of the epoxy resin in tetrahydrofuran and isobutanol is 40-50°C, and the dissolution time is ≥20 min.

[0011] Preferably, the dissolution temperature of polyvinyl alcohol 2488 is 50-60°C.

[0012] Preferably, in step (3), the oil phase is added to the water phase at a rotation speed of 3000 to 5000 rpm.

[0013] In a third aspect, the present invention provides use of the liquid binder in preparing iron ore pellets.

[0014] In the application, iron ore concentrate and bentonite are dry-mixed, material A is first added for disc granulation, and material B is then added for further granulation and solidification to obtain green balls, which are then dried and roasted to obtain finished pellets.

[0015] Preferably, the dry mixing time of the iron ore concentrate and bentonite is greater than 2 minutes.

[0016] Preferably, after adding material A, the disc granulation speed is 25 rpm and the inclination angle is 45-50° to a green ball particle size of 8-12 mm.

[0017] Preferably, after adding material B, granulation is continued until solidification.

[0018] Preferably, the calcination temperature is 1280-1360°C.

[0019] Beneficial effects: The present invention increases the bonding force of the binder, makes the pellet particle size uniform, improves the pelletization rate (over 86%), and significantly improves the drop strength of the green pellet (>6.5 / time 0.5 m drop) and the strength of the pellet after roasting (over 3000 N) through the synergistic effect of epoxy resin cross-linking and curing and silica fume-soda high-temperature pore formation, under the condition that the bentonite dosage is reduced to 1.0-1.5%. It also reduces the amount of bentonite added, the amount of SiO2 and Al2O3 introduced, the amount of slag formation, the iron grade of the pellet ore after roasting, and the reducibility of the pellet after roasting, with the reduction degree RI being over 80%. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by this application more clear, the application is further described in detail below in conjunction with the embodiments. Unless otherwise defined, all scientific and technical terms used herein have the same meanings as understood by ordinary technicians in this field.

[0021] The binder commonly used in existing disc granulation technology is sodium bentonite, an aluminosilicate mineral with a SiO2 content of 55% to 65% and an Al2O3 content of 14% to 24%. Due to its low binding strength, adding too much bentonite can introduce excessive amounts of SiO2 and Al2O3. Silicon and aluminum are materials that must be removed during blast furnace ironmaking. Alkaline solvents such as limestone and dolomite are used to neutralize and remove slag. The addition of one ton of bentonite to one ton of alkaline solvent is equivalent to the amount of iron ore required to smelt one ton of iron. Increasing the amount of alkaline solvent added to the furnace increases the slag-to-iron ratio in the blast furnace and introduces more sulfur, making smelting more difficult, increasing energy consumption, lowering iron grade, and raising pig iron costs.

[0022] According to production experience, high bentonite dosages of 2-3 wt% lead to lower iron grade, a TFe loss of 0.8-1.5%, low calcined ball porosity of <30%, poor reducibility, and an RI <65%. For every 1 wt% of bentonite added, the iron grade of the pellets decreases by 0.6 wt%, the blast furnace coke ratio increases by 1.2%, the iron content decreases by 7 kg / t, and the yield decreases by 1.8%. Furthermore, these factors result in low bonding strength, low pellet formation rate, low green ball strength, and poor pellet strength after calcination, increasing the amount of recycle and the production cost of pellet production. Existing liquid binders, such as asphalt, while having high bonding strength, produce harmful gases such as benzopyrene during high-temperature calcination, polluting the environment and requiring additional exhaust gas treatment equipment, increasing production costs.

[0023] Therefore, in a first aspect, in one embodiment of the present invention, there is provided a liquid binder for iron ore concentrate disc granulation which is environmentally friendly and can reduce the amount of bentonite used, wherein the raw materials thereof include material A and material B; The material A, calculated based on the total weight of the components being 100%, comprises: 10-15% of bisphenol A epoxy resin 6101, 10-15% of epoxy resin 711, 2-3% of tetrahydrofuran, 4-6% of dibutyl phthalate, 0.02-0.03% of dodecylphenol polyoxyethylene ether OP-10, 0.1-0.4% of polyvinyl alcohol 2488, 0.02-0.03% of isobutanol, 3-5% of silica fume, 3-5% of soda ash, and the balance being water; The material B is polyamide resin type 200, wherein the addition amount of the material B is 40-50% of the mass of bisphenol A epoxy resin type 6101.

[0024] First, the specific raw material composition mechanism of the liquid binder of the present invention is as follows: Material A: Bisphenol A epoxy resin 6101 and epoxy resin 711 are used as tackifiers. Bisphenol A epoxy resin 6101 can form a three-dimensional cross-linked skeleton, improve adhesion, and increase pellet forming rate and wet strength. Epoxy resin 711 can adjust the flexibility of the system and reduce brittle cracking. Tetrahydrofuran is used as a solvent, a highly permeable solvent that can penetrate deep into the pores of iron ore concentrate. Dibutyl phthalate is used as a diluent plasticizer to optimize the rheological properties of pelletization, improve pelletizing performance and compressive strength, and increase pellet size uniformity. Dodecylphenol polyoxyethylene ether OP-10 is used as an emulsifier to reduce surface tension while improving wettability and spreadability. Polyvinyl alcohol 2488 is used as a film emulsifier to improve the impact resistance and compressive strength of the green pellets. Isobutanol is used as a defoamer to eliminate bubbles formed by the emulsifier, reducing bubble volume by ≥90%. Silica fume and soda ash form sodium silicate at high temperatures, releasing carbon dioxide to improve the pore structure and the reducibility of the calcined pellets. Water is the continuous phase solvent.

[0025] Material B: Polyamide resin type 200 is used as a room temperature curing agent for epoxy resin. It triggers a cross-linking reaction at room temperature to solidify it and improve the dry ball compressive strength together. Therefore, materials A and B are stored separately. After the bentonite and iron ore powder are mixed evenly, they are added in the order of A first and then B.

[0026] Second, the synergistic mechanism of the various components of the adhesive of the present invention: The binder of the present invention increases the bonding force of the binder through the synergistic effect of epoxy resin cross-linking and curing and silica fume-soda high-temperature pore formation, under the condition that the amount of bentonite is reduced to 1.0-1.5%, makes the particle size of the pellets uniform, improves the pelletizing rate, significantly improves the green pellet strength and the strength of the pellets after roasting, reduces the amount of bentonite added, reduces the amount of SiO2 and Al2O3 introduced, reduces the amount of slag formation, improves the iron grade of the pellets after roasting, and improves the reducibility of the pellets after roasting.

[0027] The adhesive of the present invention is an oil-in-water emulsion system. The OP-10 emulsifier disperses the epoxy resin into micron-sized oil droplets. 50=1~5 μm, a stable aqueous coating layer is formed by polyvinyl alcohol; tetrahydrofuran quickly penetrates the pores of iron ore concentrate particles, and dibutyl phthalate adjusts the rheological properties of the system to promote rolling ball formation and ball formation uniformity.

[0028] Moreover, the binder of the present invention has a dual-stage reinforcement mechanism. It can be cured at room temperature: the amino group (-NH2) of the polyamide resin reacts with the epoxy group to form a dense three-dimensional cross-linked network within 24 hours at room temperature, so that the compressive strength of the green ball is ≥ 1200 N / pellet; it can also form pores at high temperature: in the roasting stage > 800°C, CO2 escapes to form a porous structure with a porosity of 35-45%, thereby improving the reducibility RI of the pellets to ≥ 80%.

[0029] Third, the advantages of limiting the content of each component of the binder of the present invention are: The total amount of two epoxy resins, bisphenol A type 6101 + 711, is 20-30% because the total amount of epoxy resin must meet the following requirements: Adhesion strength: ≥20% can form a continuous cross-linking network, green ball strength>1200 N / particle; Emulsion stability: <30% to avoid excessive oil phase causing demulsification, viscosity <1000 mPa·s.

[0030] Consequences of exceeding the range: Bisphenol A type 6101 + 711 type <20%, insufficient crosslinking density, decreased adhesion, and green ball strength <800 N / pellet; >30%, excessive oil phase proportion, emulsion stratification (T < 24 h), loss of storage stability, and a 30% decrease in ball formation rate.

[0031] The THF content is limited to 2-3% because within this range, it can quickly penetrate the pores of the iron ore concentrate, resulting in a contact angle of less than 20°. When the content is less than 2%, the penetration rate decreases by 50%, resulting in a loose interior of the green pellets. When the content is greater than 3%, rapid evaporation causes surface cracking, with a crack rate greater than 15%.

[0032] A dibutyl phthalate content of 4-6% can adjust the resin's glass transition temperature (Tg) from 80°C to 45°C, improving plasticity. When the content is less than 4%, green balls become more brittle, with drop strength less than 5 times / 0.5 m. When the content is greater than 6%, excessive softening occurs, with green ball deformation greater than 20%.

[0033] OP-10 emulsifier content of 0.02-0.03% can reduce the oil-water interfacial tension to 28-30 mN / m. When the content is less than 0.02%, oil droplets coalesce, D50 is greater than 10 μm, and coating is uneven. When the content is greater than 0.03%, excessive foaming increases foam volume by 300%.

[0034] Polyvinyl alcohol 2488 content of 0.1-0.4% can form a water-phase film, improving drop resistance, with a drop resistance of 10 or more times from a distance of 0.5 m. When the content is less than 0.1%, the water-phase film-forming property is poor, and the surface of the raw balls becomes powdery. However, when the content is greater than 0.4%, the system viscosity is too high, exceeding 1500 mPa·s, causing clogging of the atomizing spray.

[0035] The silica fume content is 3-5%, providing SiO2 to participate in high-temperature pore-forming reactions. When the content is less than 3%, CO2 generation is insufficient, and the porosity is less than 30%, which is within the traditional level. When the content is greater than 5%, excessive oil absorption hinders cross-linking and the green ball strength decreases by 40%.

[0036] A soda ash content of 3-5% can adjust the pH to 8-9, accelerating the curing reaction rate. When the content is less than 3% and the pH is less than 7.5, the polyamide cures slowly, with a surface-free time of more than 8 hours. When the content is greater than 5%, the alkalinity is too strong, causing hydrolysis of the epoxy resin and a 60% decrease in emulsion stability.

[0037] Silica fume: sodium carbonate = (0.5~1.5):1, is to achieve the ideal reaction stoichiometric ratio of SiO2:Na2CO3 = 1:1. If the balance is unbalanced, the silica fume is excessive, the unreacted SiO2 will block the pores, and the porosity will drop by 25%; if the sodium carbonate is excessive, the residual Na + This causes the pellets to absorb moisture, with a moisture content of >5%.

[0038] Tetrahydrofuran:isobutanol = (80-125):1, with a gradient volatilization design. The boiling points of the two are 66°C vs. 108°C. If the isobutanol content is too high, evaporation will be too slow, extending the drying time to >2 hours. If the tetrahydrofuran content is too high, evaporation will be too rapid, causing surface stress cracking.

[0039] Fourth, the selection advantages of each component model in the adhesive of the present invention: 1. Epoxy resin model selection: 1. Bisphenol A epoxy resin 6101 type (E-44): The epoxy value is 0.41-0.47 eq / 100g, and the viscosity is 2500-3500 mPa·s (25°C). Its advantages include: the viscosity characteristics meet the requirements for emulsification shear dispersion, with D50 = 2-5 μm at 5000 rpm. Excessively high viscosity, such as E51 type (>4000 mPa·s), results in a 50% increase in emulsification energy consumption. Its epoxy value forms an ideal crosslinking density with polyamide 200 type (amine value 200-220 mg KOH / g), and the gel time is 25°C / 4 h.

[0040] 2. Epoxy resin 711 type (E-20 modified): The epoxy value is 0.18-0.22 eq / 100g, and the viscosity is 6000-8000 mPa·s (40°C). As a flexibility regulator, its advantages are: compared with unmodified E-20, the long-chain fatty acid modified structure increases the elongation at break by >30%, which can prevent the brittle cracking of green balls; and it has low-temperature compatibility. After blending with 6101, the glass transition temperature (Tg) drops to 45°C (pure 6101 Tg = 80°C).

[0041] If replaced with E-51 (high activity): the curing rate is too fast, the gel time is less than 1 hour, and the granulation process cannot be completed; If replaced with E-12 (high molecular weight): the oil droplet size after emulsification is greater than 20 μm, and the coating is uneven.

[0042] 2. Selection of functional additives 1. OP-10 emulsifier (dodecylphenol polyoxyethylene ether-10): Its HLB value is 14.5, and the number of hydrophilic groups EO = 10. Its advantage lies in the adaptability of the HLB value: the water-in-oil system requires HLB>13 (measured interfacial tension 28 mN / m), and the Span type (HLB<6) is only suitable for oil-in-water; alkali resistance: It is stable at pH=8~9 (soda ash environment), compared with Tween-80, whose hydrolysis rate in alkaline environment is>15%.

[0043] 2. Polyvinyl alcohol 2488 type (alcoholysis degree 88%): Its alcoholysis degree is 88±2%, and its polymerization degree is 2400-2500. Its advantage lies in the film-forming-emulsification balance: the partially alcoholyzed structure (containing 12% acetyl groups) has both water solubility (film-forming property) and interfacial activity (emulsification assistance), while the fully alcoholyzed type (such as 1799) only forms a film but has no emulsifying function; strength contribution: the high polymerization degree gives the green ball a drop resistance of >10 times / 2 m (the low polymerization degree 1788 type <5 times).

[0044] If replaced with carboxymethyl cellulose (CMC): flocculation occurs when encountering silica fume / soda ash, and storage stability decreases by 70%.

[0045] 3. Selection of solvent and filler model 1. Silica fume (microsilica fume, SiO2>92%): Particle size D50 = 0.1 ~ 0.3 μm, specific surface area 15 ~ 30 m² / g; advantage lies in high reactivity: amorphous SiO2 starts to react at 800℃, while crystalline quartz sand needs to be >1200℃; particle size matching: ultrafine particle size ensures D90 ≤ 10 μm after ball milling (quartz powder D90 > 50 μm).

[0046] 2. Soda ash (industrial grade light Na2CO3): Bulk density 0.5-0.6 g / cm³, pH=11.2 (1% solution); Advantages include dispersibility: lightweight structure allows for easy ultrafine milling, while grinding time is twice as long as that of heavy soda ash; Reaction efficiency: low bulk density ensures uniform mixing with silica fume, with a molar ratio fluctuation of <5%.

[0047] The binder components of the present invention are precisely proportioned and model-locked. If the components and proportions are not within the specified ranges of the present invention, the imbalance in the proportions will trigger chain failures, and model replacement will lead to interface mismatch. The present invention overcomes the contradiction between strength and quality of traditional binders through molecular-level interface design (resin-solvent-mineral powder) and micro-nanostructure control (emulsion particle size / silica fume filling). Every parameter of the component ratio and model is the result of experimental optimization and mechanism verification.

[0048] In a second aspect, in another embodiment of the present invention, a method for preparing the above-mentioned liquid binder is provided, including the preparation of material A, wherein the preparation method comprises the following steps: (1) Fully swell and mix bisphenol A epoxy resin 6101 and epoxy resin 711 with tetrahydrofuran and isobutyl alcohol, and stir evenly; then add dibutyl phthalate and dodecylphenol polyoxyethylene ether OP-10 emulsifier, and continue stirring evenly to form the oil phase; (2) Dissolve polyvinyl alcohol 2488 in water, add silica fume and soda ash, and ball mill until D90 ≤ 10 μm to serve as the aqueous phase; (3) Add the oil phase to the water phase and emulsify to obtain material A.

[0049] In one specific embodiment of the present invention, the epoxy resin is pre-dissolved in an organic solvent and stirred at 40°C for 30 minutes. This is because the viscosity of bisphenol A epoxy resin type 6101 is 2500-3500 mPa·s, requiring full swelling in tetrahydrofuran. Compared to 25°C, 40°C is closer to the resin's glass transition temperature (Tg≈50°C), enhancing molecular chain mobility and increasing the dissolution rate by 300%.

[0050] Moreover, due to the strong polarity of tetrahydrofuran (dipole moment 1.75D), it can disassemble the hydrogen bonds between epoxy molecules, thus preventing undissolved particles from causing the oil droplets to coarsen to >10 μm after emulsification.

[0051] If the dissolution temperature is greater than 50°C, tetrahydrofuran will evaporate too quickly (boiling point 66°C) and the resin will be partially solidified. If the dissolution time is less than 20 min, the dissolution is incomplete and the particle size distribution becomes wider after emulsification (Span value > 1.2).

[0052] In one specific embodiment of the present invention, the aqueous phase must be ultrafinely dispersed, ball-milled to a particle size of D90 ≤ 10 μm. This is because silica fume (primary particle size 0.1-0.3 μm) easily agglomerates into particles larger than 50 μm. Limiting the particle size to D90 ≤ 10 μm ensures high-temperature reaction rates (specific surface area > 5 m² / g), ensuring complete reaction within the specified calcination temperature and time. The dispersion medium used is an aqueous solution of polyvinyl alcohol 2488, which provides steric hindrance and prevents reagglomeration.

[0053] If D90 > 15 μm, the reaction will be delayed and the porosity will drop to 28% (target ≥ 35%). If there is no ball milling process, the silica fume / soda ash distribution will be uneven and the local pH > 10 will lead to epoxy hydrolysis.

[0054] In one specific embodiment of the present invention, gradient emulsification is employed, with the oil phase added to the water phase at 5000 rpm. This avoids phase inversion (O / W → W / O), as OP-10, with an HLB of 14.5, is well-suited for O / W systems. 5000 rpm corresponds to a Weber number (We) > 10, allowing oil droplet breakup to overcome interfacial tension (28 mN / m), resulting in an emulsion with a D50 of 2-5 μm. Controlling the temperature at 60°C reduces the viscosity of the water phase, from 35 to 15 mPa·s, improving emulsification efficiency.

[0055] If the water phase is added to the oil phase, a W / O emulsion will form, with a conductivity of less than 5 μS / cm, and adhesion failure. If the rotation speed is less than 3000 rpm and the oil droplet D50 is greater than 10 μm, uneven coating will cause the green ball strength to drop by 40%.

[0056] In another embodiment of the present invention, there is provided use of the above-mentioned liquid binder in preparing iron ore pellets.

[0057] In the application, iron ore concentrate and bentonite are dry-mixed, material A is first added for disc granulation, and material B is then added for further granulation and solidification to obtain green balls, which are then dried and roasted to obtain finished pellets.

[0058] In one embodiment of the present invention, iron ore concentrate and bentonite are dry-mixed for 3 minutes. Bentonite, comprising 1.0-1.5% of the iron ore concentrate, acts as a "skeleton agent" to pre-coat the iron ore concentrate, improving the wettability of Material A, increasing the contact angle from 85° to 35°. Dry-mixing for >2 minutes ensures uniform dispersion (coefficient of variation <5%) and prevents localized clumping. Skipping dry mixing results in rapid absorption of Material A by the iron ore concentrate, resulting in insufficient surface resin concentration and a green pellet strength of <800 N / pellet.

[0059] In one specific embodiment of the present application, A material is added first, and granulation is performed for 8 minutes, which has the advantages of wet penetration: tetrahydrofuran (boiling point 66°C) penetrates into the pores of the iron concentrate (penetration depth > 50 μm) within 2 minutes; and rolling nucleation: the plasticizing effect of dibutyl phthalate reduces the plastic viscosity, so that the "mother ball" particle size quickly reaches 8-12 mm. 8 minutes corresponds to the optimum rolling period (green ball density > 0.85 g / cm³) at a disc inclination angle of 50°.

[0060] In one specific embodiment of the present application, B material is added later, and granulation is continued for 10-15 minutes until solidification, which has the advantages that the primary amine group (-NH2) of polyamide resin 200 type reacts with the epoxy group, and the gel time is 25°C / 4 h.

[0061] The step-by-step design has the advantages that if A / B material is premixed, the pot life is < 20 minutes (viscosity doubles), and granulation cannot be completed. 15 minutes guarantees diffusion of the amine group to the resin interface (diffusion coefficient 10 -10 m² / s), and the crosslinking degree is > 80%.

[0062] The following specific embodiments will be listed to explain the scheme of the present application. Those skilled in the art will understand that the following examples are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. If the specific technology or conditions are not specified in the examples, the technology or conditions described in the literature in the art or according to the product manual are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be obtained by purchase. Examples

[0063] The raw materials were weighed according to the ingredients and proportions in Table 1, and the binder was prepared according to the following steps: 1. A material preparation: (1) A material bisphenol A epoxy resin 6101 type, epoxy resin 711 type, tetrahydrofuran, isobutyl alcohol were mixed, stirred at 40°C for 30 minutes; dibutyl phthalate, dodecyl phenol polyoxyethylene ether OP-10 type emulsifier was added, and stirring was continued until uniform, as an oil phase; (2) Polyvinyl alcohol 2488 type was dissolved in 60°C water, silica ash, soda ash was added, and ball milling was performed until D90≤10 μm, as an aqueous phase; (3) The oil phase was added to the aqueous phase under 5000 rpm, and emulsification was performed for 20 minutes to obtain A material.

[0064] 2. B material preparation: Polyamide resin 200 type was directly packaged.

[0065] Table 1 Raw material ingredients and proportions of the binder (wt%)

[0066] 3. Use materials A and B for iron ore concentrate disc granulation: Iron ore concentrate indicators: TFe 62.5%, SiO2 4.8%, moisture 8.5%, -200 mesh accounting for 87%; Sodium bentonite specifications: colloidal value 366 mL / 15g, expansion capacity 18 mL / g, viscosity at 10% concentration at room temperature is 450 mPa·s. Sodium bentonite addition amount: 1.2 wt% of iron ore concentrate; Total addition amount of material A: 7.0 wt% of dry iron ore concentrate; The amount of material B added: the mass ratio of bisphenol A epoxy resin 6101 in material A, as shown in Table 1; The thermal system is shown in Table 2 below. The preferred equipment is a belt roaster: Table 2 Thermal parameters of disc granulation

[0067] The reference standard for iron pellets produced from iron concentrate or iron ore fines is GB / T 27692-2024 Iron Pellets for Blast Furnaces. The specific disc pelletizing steps are as follows: Dry mix the iron ore concentrate and sodium bentonite for 3 minutes; then spray material A, with the disc granulation speed at 25 rpm and the inclination angle at 45-50° until the green pellet size reaches 8-12 mm; add material B, and continue granulation for 15 minutes to trigger curing; the green pellets are dried, preheated, and roasted to obtain finished pellets.

[0068] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the conventional bentonite process is adopted, and the pellets are prepared according to 2.5% sodium bentonite and 8% water in the iron ore concentrate. The preparation method is the same as that in Example 1.

[0069] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the binder contains only material A and no material B, and the other operations are the same as those of Example 1.

[0070] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that material A does not contain silica fume and soda ash, and the other operations are the same as those in Example 1.

[0071] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that during the iron ore concentrate disc granulation, materials A and B are added simultaneously, and the other operations are the same as those in Example 1.

[0072] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that 2% anhydrous ethanol is used to replace 2.8% tetrahydrofuran in material A, and the other operations are the same as those in Example 1.

[0073] Comparative Example 6 Comparative Example 6 differs from Example 1 in that the silica fume accounts for 2% of the A material and the soda ash accounts for 6% of the A material, and the rest of the operations are consistent with Example 1.

[0074] Comparative Example 7 Comparative Example 7 differs from Example 1 in that the total amount of epoxy resin in the A material is 18%, and the rest of the operations are consistent with Example 1.

[0075] Performance Test The green balls and baked pellets prepared in the examples and comparative examples were tested for performance according to the reference standard GB / T 27692-2024 "Iron Ore Pellets for Blast Furnace".

[0076] Table 3 Effect of binder on production of green balls and baked pellets

[0077] As can be seen from Table 3, when the proportion of bisphenol A epoxy resin type 6101 is increased, it is more conducive to improving the strength, and when the silica fume / soda ash = 5:3.8, the porosity and strength of the baked pellets are in the best balance, as described in the results of Example 3.

[0078] Comparative Example 1 is a traditional process, with bentonite accounting for 2.5%, and the defect is that there is a lot of slag phase, and the grade is 62.8%.

[0079] Comparative Example 2 has only A material without B material, and the defect is that it does not solidify at room temperature, and the structure of the green balls is loose and the strength collapses.

[0080] Comparative Example 3 has no silica fume / soda ash, and the defect is that there is no pore formation at high temperature, and the reducibility drops sharply.

[0081] Comparative Example 4 has both A and B materials added, and the defect is that premature solidification leads to uneven coating.

[0082] Comparative Example 5 is a replacement of tetrahydrofuran with ethanol, and the defect is that the solvent has insufficient permeability and weak bonding, with a balling rate of 79.3%.

[0083] Comparative Example 6 is that the silica fume accounts for 2% of the A material and the soda ash accounts for 6% of the A material, and the defect is that the silica fume is insufficient, which reduces the particle bonding force, and the excess soda ash makes the green balls absorb moisture and soften, and the structural stability deteriorates, the excess soda ash generates low-melting-point sodium silicate, which reduces the strength, and the excess CO2 escapes, which makes the opening rate too high and the pore size too large (>100 μm), which makes the reduction insufficient.

[0084] Comparative Example 7 has a total amount of epoxy resin in the A material of 18%, and the defect is that the total amount of resin is insufficient, which makes the particle coating layer thin, the crosslinking network density insufficient, which reduces the structural toughness, and the overall bonding force decreases, and the green ball compression strength decreases.

Claims

1. Liquid binder for disc granulation of iron ore concentrate, characterized by: The raw materials include A material and B material; The material A, calculated based on the total weight of the components being 100%, comprises: 10-15% of bisphenol A epoxy resin 6101, 10-15% of epoxy resin 711, 2-3% of tetrahydrofuran, 4-6% of dibutyl phthalate, 0.02-0.03% of dodecylphenol polyoxyethylene ether OP-10, 0.1-0.4% of polyvinyl alcohol 2488, 0.02-0.03% of isobutanol, 3-5% of silica fume, 3-5% of soda ash, and the balance being water; The material B is polyamide resin type 200, and the mass of the material B is 40-50% of the mass of bisphenol A epoxy resin type 6101.

2. The liquid binder for disc granulation of iron ore concentrate according to claim 1, characterized in that: The total amount of the epoxy resin bisphenol A type 6101 + 711 is 20-30%; the mass ratio of tetrahydrofuran to isobutanol is (80-125):

1.

3. The method for preparing the liquid adhesive according to claim 1 or 2, characterized in that: The preparation method includes the following steps: (1) Fully swell and mix bisphenol A epoxy resin 6101 and epoxy resin 711 with tetrahydrofuran and isobutyl alcohol, and stir evenly; then add dibutyl phthalate and dodecylphenol polyoxyethylene ether OP-10 emulsifier, and continue stirring to form an oil phase; (2) Dissolve polyvinyl alcohol 2488 in water, add silica fume and soda ash, and ball mill until D90 ≤ 10 μm to form an aqueous phase; (3) Add the oil phase to the water phase and emulsify to obtain material A.

4. The method for preparing a liquid adhesive according to claim 3, wherein: In step (1), the dissolution temperature of the epoxy resin in tetrahydrofuran and isobutanol is 40-50°C, and the dissolution time is ≥20 min.

5. The method for preparing the liquid adhesive according to claim 3, wherein: In step (3), the oil phase is added to the water phase at a rotation speed of 3000 to 5000 rpm.

6. Use of the liquid binder according to claim 1 or 2 in the preparation of iron ore pellets.

7. The use according to claim 6, characterized in that: The iron ore pellets are prepared by dry-mixing iron ore concentrate with bentonite, first adding material A for disc granulation, then adding material B for further granulation and solidification to obtain green balls, and then drying and roasting the green balls to obtain finished pellets.

8. The use according to claim 7, characterized in that: The dry mixing time of iron ore concentrate and bentonite is more than 2 min.

9. The use according to claim 7, characterized in that: After adding material A, the disc granulation speed is 25 rpm and the inclination angle is 45-50° to the size of the green balls 8-12 mm. After adding material B, granulation is continued until solidification.

10. The use according to claim 7, characterized in that: The calcination temperature is 1280-1360°C.

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