Iron-rich low-silicon composite binder for iron ore pellets and preparation method of iron-rich low-silicon composite binder

Abstract

The invention belongs to the technical field of binders, and particularly relates to an iron-rich low-silicon composite binder for iron ore pellets and a preparation method of the iron-rich low-silicon composite binder. On the basis of the prior art, modified starch is prepared from citric acid cross-linked starch and cyclodextrin, after magnesium-iron hydrotalcite is prepared, the magnesium-iron hydrotalcite is calcined and oxidized, p-hydroxycinnamic acid is added for intercalation, and the modified magnesium-iron hydrotalcite is prepared. A cavity structure of cyclodextrin in the modified starch and carboxyl functional groups of citric acid can be subjected to complex reaction with metal ions on the surface of the iron ore powder, so that the bonding strength of the pellets is enhanced; the p-hydroxycinnamic acid intercalated magnesium-iron hydrotalcite improves the thermal stability and dispersion performance of the magnesium-iron hydrotalcite. The iron-rich low-silicon composite binder for the iron ore pellets, which is obtained by compounding the modified starch, the modified magnesium-iron hydrotalcite, the bentonite, the sodium carboxymethyl cellulose and the dispersing agent, has excellent binding performance, the addition amount of the bentonite is reduced, the iron content of the iron ore pellets is increased, and the green pellet strength and the heat stability of the iron ore pellets are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of binders, and in particular relates to an iron-rich, low-silicon composite binder for iron ore pellets and a preparation method thereof. Background Art

[0002] The ore powder after beneficiation cannot be directly put into the furnace for smelting. The ore powder particle size is too fine. Directly putting it into the blast furnace will reduce the permeability of the material column. Therefore, it is necessary to knead the iron ore powder into iron ore pellets to make fuller use of iron ore resources. The ore powder and the binder are mixed and added to the pelletizing machine. The small particles of ore powder are bonded into large particles in a humid environment. The large particles continuously bond the ore powder during the rolling process to form raw pellets. The raw pellets rely on surface tension and capillary force to maintain them together. The hard pellets formed after calcination and drying are iron ore pellets. At present, bentonite is the most commonly used binder in the production of iron ore pellets, but every 1% of bentonite added will reduce the grade of iron ore pellets by 0.6~0.7%. In addition, since most of the iron ore in my country has a low grade, more bentonite needs to be added to make the iron ore pellets reach the hardness and strength required for production, resulting in a significant increase in the cost of steel smelting. Therefore, it is necessary to develop new binders to reduce the amount of binders while ensuring that the metallurgical properties of the pellets will not be weakened.

[0003] The Chinese invention patent with publication number CN114854984B discloses a preparation method and application method of a composite binder for producing oxidized pellets, belonging to the field of binder technology. Sodium lignin sulfonate and sodium carbonate are mixed evenly to obtain a mixture; the mixture is mixed with water and stirred to dissolve to obtain a mixture solution A; sodium bicarbonate is placed in distilled water to prepare a sodium bicarbonate solution with a concentration of 5-15g / L; then sodium pyrophosphate is added to the sodium bicarbonate solution and stirred until completely dissolved to obtain a mixed solution B; the mixed solution B is added to the mixture solution A, stirred, and then evaporated to obtain a composite binder for producing oxidized pellets. The composite binder acts on limonite powder to form pellets, which can effectively improve the strength of pellets at each stage. The Chinese invention patent with publication number CN110629020B discloses an iron-based composite binder for pellets and its preparation and use methods. The iron-based composite binder for pellets is composed of the following components according to the dry weight percentage: 95% to 97% of converter OG mud, 1% to 2.2% of hydroxypropyl methylcellulose, and 1% to 2.9% of instant sodium carboxymethyl cellulose. The invention uses the converter OG mud that has not been squeezed and dehydrated as the iron-containing raw material, adds the hydroxypropyl methylcellulose solution that has not been dehydrated and dried and the instant sodium carboxymethyl cellulose solution, and obtains the iron-based composite binder for pellets after deep fusion by microwave radiation heating heap leaching reaction. It not only realizes the efficient recycling of converter OG mud, simplifies and shortens the production process of iron-based composite binders, but also helps to improve the quality of pellets and reduce the production cost of steel joint enterprises. However, the prior art has the technical problem of not further compounding the starch structure in the starch composite binder to improve the raw ball strength and pellet grade of iron ore pellets. Summary of the invention

[0004] The object of the present invention is to provide an iron-rich, low-silicon composite binder for iron ore pellets and a preparation method thereof, so as to solve the technical problem that the prior art has not further modified the starch structure in the starch composite binder to improve the green ball strength and pellet grade of iron ore pellets.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The iron-rich and low-silicon composite binder for iron ore pellets is prepared from the following components in parts by weight: 7-13 parts of bentonite, 5-6 parts of sodium carboxymethyl cellulose, 10-15 parts of modified starch, 5-6 parts of modified magnesium iron hydrotalcite and 1-4 parts of dispersant.

[0006] The bentonite montmorillonite content is 70-80wt%, the expansion volume is 9-10mL / g, the 2h water absorption rate is 300-350%, the blue absorption amount is 30-35g / 100g, and the colloid index is 20-25% / 3g.

[0007] The model of the sodium carboxymethyl cellulose is one or more combinations of CMC-M6, CMC-IH800, and CMC-IH1500.

[0008] The dispersant is one or more combinations of sodium citrate, sodium tripolyphosphate and sodium silicate.

[0009] Preferably, the method for preparing the modified starch comprises the following steps: S11, adding starch to a 2.5-3.5 wt % sodium chloride aqueous solution to obtain a 20-30 wt % starch solution, standing at 30-40° C. for swelling for 1-2 h, and subjecting to microwave activation for 60-120 s to obtain a pretreated starch solution; S12. Add citric acid to deionized water to prepare a 30-40wt% citric acid solution, add sodium hydroxide solution to adjust the pH to 3-3.5, mix 20-30 parts of the pretreated starch solution and 40-50 parts of the citric acid solution, add 20-40 parts of cyclodextrin and 1-3 parts of sodium dihydrogen phosphate, stir at 40-50°C until the cyclodextrin is completely dissolved, let stand at room temperature for 12-18h, react at 120-140°C for 4-6h, after the reaction is completed, filter and collect the precipitate, wash with distilled water, dry at 40-50°C, grind through a 100-160 mesh sieve, and obtain modified starch.

[0010] Preferably, the microwave power in S11 is 300-500W.

[0011] Preferably, the cyclodextrin in S12 is any one of α-cyclodextrin and β-cyclodextrin.

[0012] Preferably, the preparation method of the modified magnesium-iron hydrotalcite comprises the following steps: S21. By mass, 14 to 18 parts of magnesium nitrate and 7 to 9 parts of ferric nitrate are added to 100 to 200 parts of deionized water, and 150 to 200 parts of a mixed solution of sodium hydroxide and sodium carbonate are dripped into the system under stirring, and the pH is maintained between 10.8 and 11.2 during the dripping process. After the dripping is completed, the reaction is carried out at 80 to 90° C. for 8 to 10 hours, and the precipitate is collected by centrifugation and filtration. After washing with deionized water, it is vacuum dried at 40 to 60° C. and ground to obtain magnesium-iron hydrotalcite; S22. According to parts by mass, calcine magnesium iron hydrotalcite at 600-650°C for 10-12 hours to obtain a layered oxide, add 0.3-0.5 parts of p-hydroxycinnamic acid to 50-100 parts of deionized water, mix well, then add 10-15 parts of the layered oxide, react at 70-80°C for 4-6 hours, collect the solid by suction, wash with deionized water, and dry in vacuo at 40-60°C, and grind to obtain modified magnesium iron hydrotalcite.

[0013] Preferably, the mixed solution of sodium hydroxide and sodium carbonate in S21 is prepared by adding 16 to 20 parts of sodium hydroxide and 5.3 to 6.6 parts of sodium carbonate into 130 to 180 parts of deionized water.

[0014] The method for preparing an iron-rich, low-silicon composite binder for iron ore pellets comprises the following steps: S1, pre-treated bentonite: grind the bentonite to remove large impurities and add it to deionized water to prepare a 20-30wt% bentonite suspension, let the bentonite suspension stand for 10-12h, pass through a 100-160 mesh sieve, add it to a hydrocyclone, purify it step by step, dry it at 80-90°C, grind it through a 100-160 mesh sieve to obtain pre-treated bentonite; S2. By weight, 7-13 parts of bentonite, 5-6 parts of sodium carboxymethyl cellulose, 10-15 parts of modified starch, 5-6 parts of modified magnesium iron hydrotalcite and 1-4 parts of dispersant are mixed to prepare an iron-rich and low-silicon composite binder for iron ore pellets.

[0015] Preferably, the hydrocyclone in S1 uses cyclones with inner diameters of 100 mm, 75 mm, 50 mm, and 25 mm for step-by-step purification.

[0016] The present invention also provides an application of an iron-rich, low-silicon composite binder for iron ore pellets, which is used for the production and preparation of iron ore pellets. The preparation method of iron ore pellets comprises the following steps: S31, pretreatment: drying the iron ore concentrate and iron ore pellets with an iron-rich low-silicon composite binder, a dephosphorizing agent and steel slag through a dryer, and then putting them into a silo for standby use; S32, grinding and compounding: the iron concentrate and iron ore pellets are mixed with an iron-rich low-silicon composite binder, a dephosphorizing agent and steel slag, added into a mill, ground and sieved until more than 90wt% of the powder passes through a 100-120 mesh sieve, to obtain a mixed material; S33, pelletizing: according to the mass proportion, put 2000-3000 parts of the mixture into a disc pelletizing machine, add industrial water dropwise to form mother balls, stop dripping water after the total volume of the mother balls is greater than the total volume of the remaining mixture, add 1000-2000 parts of the mixture into the disc pelletizing machine three times, each time with an interval of 3-5 minutes, and spray water to make the mother balls grow within 10-17 minutes to obtain green balls, stop adding materials after the green balls grow to an average particle size of 10-12 mm, continue rolling and compacting for 2-5 minutes, take out and screen and collect green balls with an average particle size of 10-15 mm; S34, roasting: put the raw balls into the roasting furnace, heat it to 200~300℃ and dry it for 30~40min, then heat it to 600~700℃ and preheat it for 30~40min, finally heat it to 1250~1300℃ and roast it for 20~30min, and after cooling in the furnace, iron ore pellets are obtained.

[0017] Preferably, the chemical compositions of the iron ore concentrate and steel slag in S31 are shown in Table 1: Table 1 Chemical composition of iron ore concentrate and steel slag Components TFe FeO <![CDATA[SiO 2 ]]> P S <![CDATA[Al 2 THE 3 ]]> MgO CaO other Iron Concentrate 63.43 26.69 3.87 0.019 0.92 1.55 0.86 1.23 1.431 Steel slag 80.94 4.88 3.61 0.005 0.35 0.21 1.97 6.99 1.048 Preferably, the dephosphorization agent in S31 is prepared by mixing calcium chloride and coke powder in a mass ratio of 1:5-7.

[0018] Preferably, the mass ratio of the iron concentrate and the iron ore pellets iron-rich and low-silicon composite binder, the dephosphorization agent and the steel slag in the S32 is 100:0.9~1.1:2~5:20~30.

[0019] Preferably, the disc ball making machine in S33 has an inclination angle of 30-50° and a rotation speed of 30-60 r / min.

[0020] Preferably, the total amount of industrial water used in S33 is 9-13% of the total mass of the mixture.

[0021] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. Based on the prior art, the present invention uses citric acid to crosslink starch and cyclodextrin to prepare modified starch, prepares magnesium iron hydrotalcite, and then adds para-hydroxycinnamic acid intercalation to prepare modified magnesium iron hydrotalcite through calcination oxidation. The cavity structure of cyclodextrin in the modified starch and the carboxyl functional group of citric acid can react with the metal ions on the surface of iron ore powder to form chemical bonds, thereby enhancing the bonding strength of the pellets; the para-hydroxycinnamic acid intercalated magnesium iron hydrotalcite improves the thermal stability and dispersibility of magnesium iron hydrotalcite, and can partially replace bentonite in the composite binder. The iron-rich and low-silicon composite binder for iron ore pellets obtained by compounding modified starch, modified magnesium iron hydrotalcite, bentonite, sodium carboxymethyl cellulose and dispersant has excellent bonding properties, reduces the amount of bentonite added, increases the iron content of iron ore pellets, and improves the green ball strength and thermal stability of iron ore pellets.

[0022] 2. The present invention treats starch through microwave activation to improve the degree of depolymerization and hydrophilicity of starch functional groups, and then uses citric acid to cross-link starch and cyclodextrin. The cavity structure of cyclodextrin and the carboxyl functional group of citric acid can react with metal ions on the surface of iron ore powder particles to form chemical bonds, thereby enhancing the bonding strength of the pellets. The raw materials of modified starch are widely available and relatively inexpensive, and the use of modified starch in the preparation of composite binders can improve the green strength of iron ore pellets.

[0023] 3. The present invention prepares magnesium-iron hydrotalcite by reacting ferric nitrate and magnesium nitrate under alkaline conditions, calcines and oxidizes the prepared magnesium-iron hydrotalcite, and then adds p-hydroxycinnamic acid for intercalation to obtain modified magnesium-iron hydrotalcite, thereby improving the thermal stability and dispersibility of the modified magnesium-iron hydrotalcite in iron ore powder, enabling the modified magnesium-iron hydrotalcite to withstand the sintering process of iron ore pellets at high temperatures, and being used in the preparation of a composite binder to improve the green ball strength and thermal stability of iron ore pellets. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Example 1: The iron-rich, low-silicon composite binder for iron ore pellets of this example is prepared from the following components: 9g bentonite, 5.5g sodium carboxymethyl cellulose, 13g modified starch, 5.5g modified magnesium iron hydrotalcite and 3g dispersant.

[0026] The bentonite montmorillonite content is 77.9wt%, the swelling capacity is 10mL / g, the 2h water absorption rate is 335%, the blue absorption amount is 33g / 100g, and the colloid index is 24% / 3g; the model of the sodium carboxymethyl cellulose is CMC-IH800; and the dispersant is sodium tripolyphosphate.

[0027] The preparation method of the modified starch of this embodiment comprises the following steps: S11, by mass, 7.5 g of starch was added to 22.5 g of a 3 wt % sodium chloride aqueous solution to obtain a 25 wt % starch solution, which was allowed to swell at 35° C. for 1 h, and activated with a microwave power of 300 W for 90 s to obtain a pretreated starch solution; S12. By mass, add 13.5 g of citric acid to 31.5 g of deionized water to prepare a 30 wt% citric acid solution, add sodium hydroxide solution to adjust the pH to 3.5, mix 30 g of the pretreated starch solution and 45 g of the citric acid solution, add 30 g of β-cyclodextrin and 2 g of sodium dihydrogen phosphate, stir at 40°C until the cyclodextrin is completely dissolved, let stand at room temperature for 12 h, react at 120°C for 4 h, after the reaction is completed, filter and collect the precipitate, wash with distilled water, dry at 40°C, grind through a 100 mesh sieve, and obtain modified starch.

[0028] The preparation method of the modified magnesium-iron hydrotalcite of this embodiment comprises the following steps: S21. By mass, 15 g of magnesium nitrate and 8 g of ferric nitrate are added to 200 g of deionized water, 20 g of sodium hydroxide and 6.6 g of sodium carbonate are added to 173.4 g of deionized water to prepare a mixed solution of sodium hydroxide and sodium carbonate, and 200 g of the mixed solution of sodium hydroxide and sodium carbonate is dropped into the system under stirring, and the pH is maintained between 11 during the dropping process. After the dropping is completed, the reaction is carried out at 80° C. for 10 hours, and the precipitate is collected by centrifugation, washed with deionized water, and then dried in vacuo at 50° C., and ground to obtain magnesium-iron hydrotalcite; S22. According to the mass, magnesia iron hydrotalcite was calcined at 650°C for 12 hours to obtain a layered oxide. 0.5 g of p-hydroxycinnamic acid was added to 100 g of deionized water and mixed evenly. Then 15 g of the layered oxide was added and reacted at 80°C for 4 hours. The solid was collected by filtration, washed with deionized water, and dried in a vacuum at 60°C. The modified magnesia iron hydrotalcite was obtained by grinding.

[0029] The method for preparing iron ore pellets using an iron-rich, low-silicon composite binder for iron ore pellets of this embodiment comprises the following steps: S1. Pretreatment of bentonite: Grind the bentonite to remove large impurities and add it to deionized water to prepare a 20-30 wt% bentonite suspension. Let the bentonite suspension stand for 12 hours, pass through a 100-mesh sieve, add it to a hydrocyclone, purify it step by step using cyclones with inner diameters of 100 mm, 75 mm, 50 mm, and 25 mm, dry it at 90° C., grind it through a 100-mesh sieve to obtain pretreated bentonite. S2. According to mass, 9 g of bentonite, 5.5 g of sodium carboxymethyl cellulose, 13 g of modified starch, 5.5 parts of modified magnesium iron hydrotalcite and 3 g of dispersant were mixed to prepare an iron-rich and low-silicon composite binder for iron ore pellets.

[0030] The application of the iron-rich and low-silicon composite binder for iron ore pellets in this embodiment is used for the production and preparation of iron ore pellets. The preparation method of iron ore pellets includes the following steps: S31, pretreatment: calcium chloride and coke powder are mixed in a mass ratio of 1:5 to prepare a dephosphorization agent, and the iron ore concentrate and iron ore pellets are dried by a dryer with an iron-rich low-silicon composite binder, a dephosphorization agent and steel slag, and then placed in a silo for standby use; S32, grinding and compounding: 5 kg of iron concentrate, 45 g of iron ore pellets with iron-rich low-silicon composite binder, 100 g of dephosphorization agent and 1 kg of steel slag are added into a mill, and ground and sieved until more than 90 wt % of the powder passes through a 100 mesh sieve to obtain a mixed material; S33, pelletizing: according to the mass, 3kg of the mixture is placed in a disc pelletizing machine with an inclination angle of 40° and a rotation speed of 50r / min, and industrial water is added dropwise to form mother balls. When the total volume of the mother balls is greater than the total volume of the remaining mixture, the dripping of water is stopped. 2kg of the mixture is added to the disc pelletizing machine three times, each time with an interval of 4 minutes, and water is sprayed to make the mother balls grow within 15 minutes to obtain green balls. When the green balls grow to an average particle size of 10mm, the addition of materials is stopped. The total amount of industrial water used is 11% of the total mass of the mixture. Continue rolling and compacting for 3 minutes, take out and screen and collect green balls with an average particle size of 13mm; S34, roasting: put the raw balls into the roasting furnace, heat it to 200℃ and dry it for 30min, then heat it to 600℃ and preheat it for 30min, finally heat it to 1250℃ and roast it for 30min, and after cooling in the furnace, iron ore pellets are obtained.

[0031] Example 2: The iron-rich, low-silicon composite binder for iron ore pellets of this example is prepared from the following components: 7g bentonite, 5g sodium carboxymethyl cellulose, 10g modified starch, 5g modified magnesium iron hydrotalcite and 1g dispersant.

[0032] The bentonite montmorillonite content is 71wt%, the swelling capacity is 9.9mL / g, the 2h water absorption rate is 312%, the blue absorption amount is 31.3g / 100g, and the colloid index is 23% / 3g; the model of the sodium carboxymethyl cellulose is CMC-M6; and the dispersant is sodium silicate.

[0033] The method for preparing the iron-rich and low-silicon composite binder for iron ore pellets of this embodiment comprises the following steps: S1. Pretreatment of bentonite: Grind the bentonite to remove large impurities and add it to deionized water to prepare a 20 wt% bentonite suspension. Let the bentonite suspension stand for 10 hours, pass through a 120-mesh sieve, add it to a hydrocyclone, purify it step by step using cyclones with inner diameters of 100 mm, 75 mm, 50 mm, and 25 mm, dry it at 85° C., grind it through a 120-mesh sieve to obtain pretreated bentonite. S2. According to mass, 7 g of bentonite, 5 g of sodium carboxymethyl cellulose, 10 g of modified starch, 5 g of modified magnesium iron hydrotalcite and 1 g of dispersant were mixed to prepare an iron-rich and low-silicon composite binder for iron ore pellets.

[0034] The method for preparing iron ore pellets using an iron-rich, low-silicon composite binder for iron ore pellets of this embodiment comprises the following steps: S31, pretreatment: calcium chloride and coke powder are mixed in a mass ratio of 1:6 to prepare a dephosphorization agent, and the iron ore concentrate, iron ore pellets, iron-rich low-silicon composite binder, dephosphorization agent and steel slag are dried by a dryer respectively, and then put into a silo for standby use; S32, grinding and compounding: adding 3 kg of iron concentrate, 28 g of iron ore pellets with iron-rich low-silicon composite binder, 60 g of dephosphorization agent and 0.9 kg of steel slag into a mill, grinding and sieving until more than 90 wt % of the powder passes through a 120-mesh sieve to obtain a mixed material; S33, pelletizing: according to the mass, put 2kg of the mixture into a disc pelletizing machine with an inclination angle of 30° and a rotation speed of 30r / min, add industrial water dropwise to form mother balls, and stop dripping water after the total volume of the mother balls is greater than the total volume of the remaining mixture, add 1kg of the mixture three times, each time with an interval of 3min, and slowly add water to the disc pelletizing machine, and spray water to make the mother balls grow within 10min to obtain green balls, and stop adding materials after the green balls grow to an average particle size of 10mm. The total amount of industrial water used is 9% of the total mass of the mixture, continue rolling and compacting for 2min, take out and screen and collect green balls with an average particle size of 11mm; S34, roasting: put the raw balls into the roasting furnace, heat to 250℃ and dry for 35min, then heat to 650℃ and preheat for 30min, finally heat to 1260℃ and roast for 25min, and after cooling in the furnace, iron ore pellets are obtained.

[0035] The difference between the modified starch of this embodiment and that of embodiment 1 is that cyclodextrin is replaced by α-cyclodextrin.

[0036] The preparation method of the modified magnesium-iron hydrotalcite of this embodiment is the same as that of the modified magnesium-iron hydrotalcite of Example 1.

[0037] Example 3: The iron-rich, low-silicon composite binder for iron ore pellets of this example is prepared from the following components: 13g bentonite, 6g sodium carboxymethyl cellulose, 15g modified starch, 6g modified magnesium iron hydrotalcite and 4g dispersant.

[0038] The bentonite montmorillonite content is 79.6wt%, the swelling capacity is 9.8mL / g, the 2h water absorption rate is 340%, the blue absorption amount is 35g / 100g, and the colloid index is 25% / 3g; the model of the sodium carboxymethyl cellulose is CMC-IH1500; and the dispersant is sodium citrate.

[0039] The method for preparing the iron-rich and low-silicon composite binder for iron ore pellets of this embodiment comprises the following steps: S1, pre-treated bentonite: grind the bentonite to remove large impurities and add it to deionized water to prepare a 30wt% bentonite suspension, let the bentonite suspension stand for 12h, pass through a 160-mesh sieve, add it to a hydrocyclone, purify it step by step using cyclones with inner diameters of 100mm, 75mm, 50mm, and 25mm, dry it at 90°C, grind it through a 160-mesh sieve to obtain pre-treated bentonite; S2. According to mass, 13 g of bentonite, 6 g of sodium carboxymethyl cellulose, 15 g of modified starch, 6 g of modified magnesium iron hydrotalcite and 4 g of dispersant were mixed to prepare an iron-rich and low-silicon composite binder for iron ore pellets.

[0040] The method for preparing iron ore pellets using an iron-rich, low-silicon composite binder for iron ore pellets of this embodiment comprises the following steps: S31, pretreatment: calcium chloride and coke powder are mixed in a mass ratio of 1:7 to prepare a dephosphorization agent, and the iron ore concentrate and iron ore pellets are dried by a dryer with an iron-rich low-silicon composite binder, a dephosphorization agent and steel slag, and then placed in a silo for standby use; S32, grinding and compounding: adding 4 kg of iron concentrate, 44 g of iron ore pellets with iron-rich low-silicon composite binder, 150 g of dephosphorization agent and 1.2 kg of steel slag into a mill, grinding and sieving until more than 90 wt % of the powder passes through a 120-mesh sieve to obtain a mixed material; S33, pelletizing: according to the mass, put 2.5kg of the mixture into a disc pelletizing machine with an inclination angle of 50° and a rotation speed of 40r / min, add industrial water dropwise to form mother balls, and stop dripping water after the total volume of the mother balls is greater than the total volume of the remaining mixture, add 1.5kg of the mixture three times, each time with an interval of 5min, and slowly add water to the disc pelletizing machine, and spray water to make the mother balls grow within 17min to obtain green balls, and stop adding materials after the green balls grow to an average particle size of 12mm. The total amount of industrial water used is 13% of the total mass of the mixture, continue rolling and compacting for 5min, take out and screen and collect green balls with an average particle size of 15mm; S34, roasting: put the raw balls into the roasting furnace, heat to 300℃ and dry for 40min, then heat to 700℃ and preheat for 40min, finally heat to 1300℃ and roast for 20min, and after cooling in the furnace, iron ore pellets are obtained.

[0041] The difference between the modified magnesium-iron hydrotalcite of this example and that of Example 1 is that the modified magnesium-iron hydrotalcite is prepared by modifying 10 g of layered oxide with 0.3 g of p-hydroxycinnamic acid.

[0042] The preparation method of the modified starch in this example is the same as that of the modified starch in Example 1.

[0043] Comparative Example 1: The difference between this comparative example and Example 1 is that modified starch is not added to the binder.

[0044] Comparative Example 2: The difference between this comparative example and Example 1 is that the modified starch is replaced by corn starch.

[0045] Comparative Example 3: The difference between this comparative example and Example 1 is that no dephosphorization agent is added in the preparation of the iron ore pellets.

[0046] Performance Testing According to YB / T4848-2020 "Physical Test Method for Roasted Green Balls", the green balls prepared in each embodiment and comparative example were repeatedly dropped from a height of 0.5 m until they broke. The average of the number of times the 20 green balls did not break was taken as the green ball drop strength.

[0047] According to YB / T4848-2020 "Physical Test Method for Roasted Green Balls", a compressive strength tester was used to test the compressive strength of the green balls prepared in each embodiment and comparative example, and the average value of the maximum force of 20 green balls was taken as the compressive strength.

[0048] According to GB / T14201-93 "Determination of compressive strength of iron ore pellets", the compressive strength of the iron ore pellets prepared in each embodiment and comparative example was tested using a compressive strength tester, and the average value of the maximum force of 20 iron ore pellets was taken as the compressive strength.

[0049] The test results are shown in Table 2: Table 2 Test results Serial number Green ball drop strength (times) Green ball compressive strength (N) Iron ore pellet compressive strength (N) Example 1 3.6 21.5 1845 Example 2 3.4 21.3 1836 Example 3 3.4 21.6 1841 Comparative Example 1 3.2 20.1 1833 Comparative Example 2 3.1 21.3 1632 Comparative Example 3 3.1 20.4 1624 It can be seen from the data in Table 1 that the drop strength of the green balls obtained in Examples 1 to 3 is 3.4 to 3.6 times, and the compressive strength is 21.3 to 21.6 N. The green ball binder of Comparative Example 1 does not add modified starch, resulting in a drop strength of 3.2 times and a compressive strength of 20.1 N for the green balls, which are slightly lower than the drop strength and compressive strength of the green balls obtained in the example, indicating that the iron-rich, low-silicon composite binder for iron ore pellets prepared by the present invention has excellent bonding strength; the compressive strength of the iron ore pellets prepared in Examples 1 to 3 is 1836 to 1845 N. No dephosphorization agent is added in the preparation of the iron ore pellets in Comparative Example 3, and the phosphorus content in the pellets is too high, resulting in increased cold brittleness. Therefore, the compressive strength of the iron ore pellets in Comparative Example 3 is 1624 N, which is lower than the compressive strength of the iron ore pellets obtained in the example, indicating that the iron-rich, low-silicon composite binder for iron ore pellets prepared by the present invention has excellent high-temperature bonding performance when used to prepare iron ore pellets.

[0050] The chemical composition of the iron ore pellets prepared in each embodiment and comparative example was tested by a chemical composition analyzer, and the test results are shown in Table 3: Table 3 Chemical composition Components TFe FeO <![CDATA[SiO 2 ]]> P other Example 1 66.93 0.96 2.52 0.006 29.484 Example 2 67.48 1.01 2.51 0.007 28.893 Example 3 67.52 0.88 2.55 0.006 28.904 Comparative Example 1 66.67 1.23 2.61 0.009 29.481 Comparative Example 2 66.86 1.16 2.54 0.008 29.432 Comparative Example 3 66.90 1.36 2.53 0.012 29.188 From the data in Table 3, it can be seen that the TFe content of Examples 1 to 3 is 66.93% to 67.52%, and the SiO 2 The content is 2.51~2.55%, the P content is 0.006~0.007%, which improves the iron grade of iron ore pellets and reduces SiO 2 The content of P is less than 1%, and no excessive P element is added, indicating that the iron-rich and low-silicon composite binder for iron ore pellets prepared by the present invention has the performance of being rich in iron and low in silicon when used to prepare iron ore pellets.

[0051] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0052] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. An iron-rich, low-silicon composite binder for iron ore pellets, characterized in that: It is prepared from the following ingredients in parts by weight: 0.7-1.5 parts of bentonite, 0.5-0.6 parts of sodium carboxymethyl cellulose, 1-1.5 parts of modified starch, 0.5-0.6 parts of modified magnesium iron hydrotalcite and 0.1-0.4 parts of dispersant; The bentonite montmorillonite content is 70-80wt%, the expansion volume is 9-10mL / g, the 2h water absorption rate is 300-350%, the blue absorption amount is 30-35g / 100g, and the colloid index is 20-25% / 3g.

2. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 1, characterized in that: The model of the sodium carboxymethyl cellulose is one or more combinations of CMC-M6, CMC-IH800, and CMC-IH1500; the dispersant is one or more combinations of sodium citrate, sodium tripolyphosphate, and sodium silicate.

3. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 1, characterized in that: The preparation method of the modified starch comprises the following steps: S11, adding starch to a 2.5-3.5 wt % sodium chloride aqueous solution to obtain a 20-30 wt % starch solution, standing at 30-40° C. for swelling for 1-2 h, and subjecting to microwave activation for 60-120 s to obtain a pretreated starch solution; S12. Add citric acid to deionized water to prepare a 30-40wt% citric acid solution, add sodium hydroxide solution to adjust the pH to 3-3.5, mix 20-30 parts of the pretreated starch solution and 40-50 parts of the citric acid solution, add 20-40 parts of cyclodextrin and 1-3 parts of sodium dihydrogen phosphate, stir at 40-50°C until the cyclodextrin is completely dissolved, let stand at room temperature for 12-18h, react at 120-140°C for 4-6h, after the reaction is completed, filter and collect the precipitate, wash with distilled water, dry at 40-50°C, grind through a 100-160 mesh sieve, and obtain modified starch.

4. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 3, characterized in that: The microwave power in S11 is 300-500W, and the cyclodextrin in S12 is any one of α-cyclodextrin and β-cyclodextrin.

5. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 1, characterized in that: The preparation method of the modified magnesium-iron hydrotalcite comprises the following steps: S21. By mass, 14 to 18 parts of magnesium nitrate and 7 to 9 parts of ferric nitrate are added to 100 to 200 parts of deionized water, and 150 to 200 parts of a mixed solution of sodium hydroxide and sodium carbonate are dripped into the system under stirring, and the pH is maintained between 10.8 and 11.2 during the dripping process. After the dripping is completed, the reaction is carried out at 80 to 90° C. for 8 to 10 hours, and the precipitate is collected by centrifugation and filtration. After washing with deionized water, it is vacuum dried at 40 to 60° C. and ground to obtain magnesium-iron hydrotalcite; S22. According to parts by mass, calcine magnesium iron hydrotalcite at 600-650°C for 10-12 hours to obtain a layered oxide, add 0.3-0.5 parts of p-hydroxycinnamic acid to 50-100 parts of deionized water, mix well, then add 10-15 parts of the layered oxide, react at 70-80°C for 4-6 hours, collect the solid by suction, wash with deionized water, and dry in vacuo at 40-60°C, and grind to obtain modified magnesium iron hydrotalcite.

6. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 5, characterized in that: The mixed solution of sodium hydroxide and sodium carbonate in S21 is prepared by adding 16 to 20 parts of sodium hydroxide and 5.3 to 6.6 parts of sodium carbonate into 130 to 180 parts of deionized water.

7. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 1, characterized in that: The method for preparing iron ore pellets with the iron-rich and low-silicon composite binder comprises the following steps: S31, pretreatment: drying the iron ore concentrate and iron ore pellets with an iron-rich low-silicon composite binder, a dephosphorizing agent and steel slag through a dryer, and then putting them into a silo for standby use; S32, grinding and compounding: the iron concentrate and iron ore pellets are mixed with an iron-rich low-silicon composite binder, a dephosphorizing agent and steel slag, added into a mill, ground and sieved until more than 90wt% of the powder passes through a 100-120 mesh sieve, to obtain a mixed material; S33, pelletizing: according to the mass proportion, put 2000-3000 parts of the mixture into a disc pelletizing machine, add industrial water dropwise to form mother balls, stop dripping water after the total volume of the mother balls is greater than the total volume of the remaining mixture, add 1000-2000 parts of the mixture into the disc pelletizing machine three times, each time with an interval of 3-5 minutes, and spray water to make the mother balls grow within 10-17 minutes to obtain green balls, stop adding materials after the green balls grow to an average particle size of 10-12 mm, continue rolling and compacting for 2-5 minutes, take out and screen and collect green balls with an average particle size of 10-15 mm; S34, roasting: put the raw balls into the roasting furnace, heat it to 200~300℃ and dry it for 30~40min, then heat it to 600~700℃ and preheat it for 30~40min, finally heat it to 1250~1300℃ and roast it for 20~30min, and after cooling in the furnace, iron ore pellets are obtained.

8. The iron-rich, low-silicon composite binder for iron ore pellets according to claim 1, characterized in that: The dephosphorization agent in S31 is prepared by mixing calcium chloride and coke powder in a mass ratio of 1:5-7; the mass ratio of the iron concentrate and iron ore pellets using an iron-rich and low-silicon composite binder, a dephosphorization agent and steel slag in S32 is 100:0.9-1.1:2-5:20-30; the inclination angle of the disc pelletizing machine in S33 is 30-50°, the rotation speed is 30-60r / min, and the total industrial water consumption is 9-13% of the total mass of the mixture.

9. A method for preparing an iron-rich, low-silicon composite binder for iron ore pellets, characterized in that: The steps include: S1, pre-treated bentonite: grind the bentonite to remove large impurities and add it to deionized water to prepare a 20-30wt% bentonite suspension, let the bentonite suspension stand for 10-12h, pass through a 100-160 mesh sieve, add it to a hydrocyclone, purify it step by step, dry it at 80-90°C, grind it through a 100-160 mesh sieve to obtain pre-treated bentonite; S2. By weight, 7-13 parts of bentonite, 5-6 parts of sodium carboxymethyl cellulose, 10-15 parts of modified starch, 5-6 parts of modified magnesium iron hydrotalcite and 1-4 parts of dispersant are mixed to prepare an iron-rich and low-silicon composite binder for iron ore pellets.

10. The method for preparing the iron-rich and low-silicon composite binder for iron ore pellets according to claim 9, characterized in that: The hydrocyclones in S1 are purified step by step using cyclones with inner diameters of 100 mm, 75 mm, 50 mm, and 25 mm.