A composite binder for super iron ore concentrate pellets and methods of making and using

Abstract

The application aims at the problems existing in the super iron concentrate pellet additive technology, and provides a composite binder for super iron concentrate pellets and a preparation and use method thereof.The composite binder of the application is composed of the following components in percentage by mass: binder 20-40 wt%, reinforcing agent 10-20 wt%, and additive 40-70 wt%. The application uses modified carboxymethyl cellulose CMC-TAPOB as the binder, organic macromolecules as the reinforcing agent, and alkaline calcium-containing substances as the additive, without adding bentonite, thereby reducing the introduction of silicon and aluminum components, and improving the quality of the super iron concentrate pellets.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of steel metallurgical pellet production, and particularly relates to a composite binder suitable for preparing pellets from super iron concentrate. BACKGROUND

[0002] Iron ore pellets have good metallurgical properties and can improve the permeability of the blast furnace column. They are considered to be high-quality furnace charges necessary for the optimization of blast furnace charge structure, and their role in the steel industry is becoming increasingly important, and their use is also increasing. Therefore, in recent years, major steel enterprises in China have been working to promote the development of pellets.

[0003] When producing pellets using iron concentrate, in order to improve the balling performance of green balls, improve the quality of pellets, and meet production requirements, a small amount of binder must be added to give the pellets a certain strength, so that they remain intact and do not break during transportation, drying, and roasting, and meet the requirements of blast furnace smelting. Most domestic pellet plants use bentonite as a binder. Since bentonite is an aluminosilicate mineral with montmorillonite as the main component, due to its own composition characteristics, the addition of bentonite also brings in certain harmful impurities and reduces the grade of the pellet.

[0004] Super iron concentrate is a new type of material with broad development prospects, and is an important raw material for powder metallurgy, magnetic materials, super-pure iron, and clean steel base materials. Super iron concentrate can also be used as a pellet raw material to produce high-quality pellets, but it is finely ground and then selected from ordinary iron concentrate, so it has a higher iron content, an iron grade of ≥70%, a lower SiO2 content, and a finer particle size, making it more prone to green ball bursting and unqualified finished ball compression strength.

[0005] Chinese Patent CN 112553460 B, "Composite binder for improving the balling performance of super iron concentrate powder and method of use", provides a composite binder of sodium-based bentonite, coarse particle coal powder, high-multiplying water-absorbing resin, and sodium carboxymethyl cellulose, which improves the bursting problem of super fine concentrate powder in the preparation of pellets and improves the quality of the pellets. However, it still uses sodium-based bentonite as the main component, which introduces silicon, aluminum, and other components into the pellets, which has a certain impact on blast furnace smelting. Using super iron concentrate to produce high-quality pellets, seeking a highly efficient new type of composite binder to completely replace bentonite, can not only reduce the introduction of various impurities that are not needed in the metallurgical process, but also ensure the quality of the pellets, which is of great significance for the quality improvement and energy saving of blast furnaces. SUMMARY

[0006] The present application aims at the problems existing in the super iron concentrate pellet additive technology, and provides a composite binder for super iron concentrate pellets and a preparation and use method thereof.

[0007] One of the technical solutions of the present application is a composite binder for super iron concentrate pellets, which is composed of the following components in percentage by mass:

[0008] Binder 20-40 wt%

[0009] Reinforcing agent 10-20 wt%

[0010] Additive 40-70 wt%

[0011] The binder is N-(1,3,5-tri(4-aminophenoxy)phenyl) carboxymethyl cellulose (CMC-TAPOB);

[0012] The reinforcing agent is one or several of modified starch, puffed starch and gelatinized starch;

[0013] The additive is one or several of limestone, quicklime and slaked lime.

[0014] Further, the synthetic method of the CMC-TAPOB in the composite binder for super iron concentrate pellets is as follows:

[0015] (1) Dissolve CMC in a phosphate buffer solution, and the concentration of the phosphate buffer solution is 1%~2.5%; the feeding ratio of CMC to the phosphate buffer solution is 1:40~60 g / mL;

[0016] (2) Add a phosphate buffer solution containing 1-ethyl-(3-dimethylaminopropyl) carbonyldiimidazole (EDC) and N-hydroxy succinimide (NHS) dropwise into the CMC phosphate buffer solution, and stir at room temperature for 20~40 minutes; wherein the molar ratio of each raw material is: CMC:EDC=1:2.4~3.0; EDC:NHS=1:5~10;

[0017] (3) Dissolve 1,3,5-tri(4-aminophenoxy) benzene (TAPOB) completely in N,N-dimethylformamide (DMF) to form a TAPOB solution, and then add the reaction solution of step (2) dropwise, and the molar ratio of TAPOB to CMC is 1~5:1;

[0018] (4) After the reaction is carried out at room temperature for 12-24 hours under continuous nitrogen and stirring, the reaction mixture is poured into anhydrous ethanol, and is left until no precipitate is separated out, and then the product CMC-TAPOB is obtained by filtration and drying.

[0019] The second technical solution of the present application is a preparation method of the composite binder, wherein the binder, the reinforcing agent and the additive are mixed uniformly at room temperature to obtain the finished product.

[0020] The particle size specification of the reinforcing agent is-325 mesh content ≥ 90%, and the particle size specification of the additive is-200 mesh content ≥ 90%.

[0021] The third technical solution of the present application is a use method of the composite binder, wherein the composite binder and the super iron concentrate are mixed to form balls, and the adding amount of the composite binder is 0.5%-1% of the total amount of the composite binder and the super iron concentrate.

[0022] Further, the use method of the composite binder comprises the following steps: 0.5-1% of the composite binder is added into 99.0-99.5% of the super iron concentrate with a water content of 8-9%, and the composite binder is uniformly dispersed in the mixture by strong mixing and stirring for 10-15 minutes at room temperature, and then the mixture is left for a certain time; the mixture after the leaving is formed into balls, and the ball forming time is 9-10 minutes; and the subsequent green ball drying, preheating and roasting processes are the conventional methods.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] By using the composite binder provided by the present application, the quality of the green ball of the prepared pellet is significantly improved, and the reduction expansion rate is also improved.

[0025] The binder used in the present application is modified carboxymethyl cellulose CMC-TAPOB. Due to the modification of TAPOB, the molecular structure of carboxymethyl cellulose is changed, so that CMC-TAPOB has a large volume and a complex structure. Moreover, TAPOB is a polyamino group organic substance, and CMC is introduced with polar groups such as amino groups, which is conducive to the combination of CMC-TAPOB with the surface active sites of super iron concentrate powder through van der Waals force, coordination action and other ways, so as to form a high molecular adsorption layer on the surface of super iron concentrate powder particles. The high molecular chains in this adsorption layer can bridge and connect between different iron concentrate powder particles, thereby increasing the adhesion between particles and making the adhesion advantage more obvious. In addition, the molecular chains of CMC-TAPOB will be entangled, and the intermolecular binding force will be further enhanced through hydrogen bonds and other interactions. This action increases the mutual restraint between iron concentrate particles, and the macroscopic performance is that the adhesion between iron concentrate particles is increased. In addition, CMC-TAPOB can bind water molecules inside the ball, avoid local accumulation of water in the ball, reduce the difference in water content between the inside and outside of the ball caused by uneven water migration during drying, and thus reduce the tendency of explosion.

[0026] The main structure of the reinforcing agent used is an organic macromolecule, which has a large number of carboxyl and hydroxyl groups and other organic functional groups. When the reinforcing agent is added to the ball, it can synergistically act with the binder to make the adhesion between iron concentrate powder particles more compact, increase the plasticity of the green ball and the compressive strength of the green ball, and make the ball more solid.

[0027] The main component of the additive after calcination is CaO. After entering the calcination stage, CaO participates in the reaction. Although the affinity of CaO with SiO2 is greater than that with Fe2O3, due to the kinetic reasons, calcium ferrite system is generated preferentially at low temperature. The melting point of the compounds in this system is relatively low, between 1200-1230℃, and liquid phase will be generated at the calcination temperature. The liquid phase can wet the surface of the particles inside the ball, tighten and rearrange them, make the structure of the ball more compact, dissolve the solid particles, promote recrystallization and crystal growth, and enhance the strength of the finished ball. During the reduction of calcium ferrite, a layer of metallic iron is generated on the surface of calcium ferrite, which forms a concentric iron layer around the ferrite particles, inhibits the expansion of the pellet, and also reduces the pulverization rate. DETAILED DESCRIPTION

[0028] A composite binder for super iron concentrate pellets, consisting of the following components by mass percentage:

[0029] Binder 20-40 wt%

[0030] Reinforcing agent 10-20 wt%

[0031] Additive 40-70 wt%

[0032] The binder is N-(1, 3, 5-tri (4-aminophenoxy) phenyl) carboxymethyl cellulose (CMC-TAPOB).

[0033] The reinforcing agent is one or more of modified starch, puffed starch, gelatinized starch, and the -325 mesh content is ≥90%.

[0034] The additive is one or more of limestone, quicklime, slaked lime, and the -200 mesh content is ≥90%.

[0035] The preparation method of the composite binder is that the binder, the reinforcing agent, and the additive are uniformly mixed at room temperature to obtain the finished product.

[0036] The use method of the composite binder is that the composite binder and the super iron concentrate are mixed and pelletized, the addition amount of the composite binder is 0.5%-1% of the total amount of the composite binder and the super iron concentrate, that is, 0.5-1% of the composite binder is added to 99.0-99.5% of the super iron concentrate with a water content of about 8-9%, and the mixture is strongly mixed and stirred at room temperature for 10-15 min to uniformly disperse the composite binder in the mixture. After uniform mixing, the mixture is left to stand for a certain period of time. The mixture after standing is pelletized, and the pelletizing time is 9-10 min. The subsequent green ball drying, preheating, and roasting processes are conventional methods.

[0037] The synthesis method of the binder CMC-TAPOB in the following examples is as follows:

[0038] (1) CMC is dissolved in a phosphate buffer solution, and the concentration of the phosphate buffer solution is 2.0%. The feeding ratio of CMC to the phosphate buffer solution is 1:50 g / mL.

[0039] (2) The phosphate buffer solution containing 1-ethyl-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) is added dropwise to the CMC phosphate buffer solution, and stirred at room temperature for 30 min. The molar ratio of each raw material is: CMC: EDC = 1:2.5; EDC: NHS = 1:7.5.

[0040] (3) 1, 3, 5-tri (4-aminophenoxy) benzene (TAPOB) is completely dissolved in N, N-dimethylformamide (DMF) to form a TAPOB solution, and then added dropwise to the reaction solution of step (2). The molar ratio of TAPOB to CMC is 3:1.

[0041] (4) After 18 hours of reaction at room temperature under continuous nitrogen and stirring, the reaction mixture is poured into anhydrous ethanol until no precipitate is precipitated, filtered, and dried to obtain the product CMC-TAPOB.

[0042] The prepared green balls were tested in the following examples and comparative examples, including drop strength, green ball compressive strength, and burst temperature. If each index of the green balls meets the standard requirements, the roasting test is continued to explore whether the compressive strength and reduction swelling rate of the finished balls meet the standard.

[0043] I. The experimental results of the comparative examples are shown in Table 1.

[0044] Comparative Example 1: Only super iron concentrate was used for balling.

[0045] Comparative Example 2: Only carboxymethyl cellulose was used for balling, and the addition amount of carboxymethyl cellulose: super iron concentrate was 0.5%:99.5%.

[0046] Comparative Example 3: Only the binder was used for balling, and the addition amount of CMC-TAPOB: super iron concentrate was 0.5%:99.5%.

[0047] Comparative Example 4: Only the reinforcing agent was used for balling, and the addition amount of puffed starch: super iron concentrate was 0.5%:99.5%.

[0048] Comparative Example 5: Only the additive was used for balling, and the addition amount of limestone: super iron concentrate was 0.5%:99.5%.

[0049] Comparative Example 6: The composite additive was composed of 70% of the binder CMC-TAPOB and 30% of the reinforcing agent puffed starch by mass percentage, and the addition amount of the composite additive: super iron concentrate was 0.5%:99.5%.

[0050] Comparative Example 7: The composite additive was composed of 30% of the binder CMC-TAPOB and 70% of the additive limestone by mass percentage, and the addition amount of the composite additive: super iron concentrate was 0.5%:99.5%.

[0051] Comparative Example 8: The composite additive was composed of 20% of the reinforcing agent puffed starch and 80% of the additive limestone by mass percentage, and the addition amount of the composite additive: super iron concentrate was 0.5%:99.5%.

[0052] Comparative Example 9: The composite additive was composed of 30% of the binder CMC, 15% of the reinforcing agent puffed starch, and 55% of the additive limestone by mass percentage, and the addition amount of the composite additive: super iron concentrate was 0.5%:99.5%.

[0053] Table 1, the performance of the green balls and finished balls of Comparative Examples 1-9

[0054]

[0055] From Table 1, when using super iron concentrate, binder, reinforcing agent and additive alone to ball, the green ball indexes are unqualified; when using the composite binder compounded by the binder and additive and the composite binder compounded by the additive and reinforcing agent, the green ball indexes are unqualified; when using the composite binder compounded by the binder and reinforcing agent, the green ball indexes meet the standard, but after roasting, the compressive strength and reduction swelling rate of the finished ball do not meet the requirements.

[0056] II. Experimental results of examples, data are shown in Table 2.

[0057] In Example 1, the mass percentage of each component of the composite binder is 20% of the binder, 10% of the reinforcing agent and 70% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.5%:99.5%;

[0058] In Example 2, the mass percentage of each component of the composite binder is 25% of the binder, 12% of the reinforcing agent and 63% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.5%:99.5%;

[0059] In Example 3, the mass percentage of each component of the composite binder is 30% of the binder, 15% of the reinforcing agent and 55% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.5%:99.5%;

[0060] In Example 4, the mass percentage of each component of the composite binder is 35% of the binder, 18% of the reinforcing agent and 47% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.5%:99.5%;

[0061] In Example 5, the mass percentage of each component of the composite binder is 40% of the binder, 20% of the reinforcing agent and 40% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.5%:99.5%;

[0062] In Example 6, the mass percentage of each component of the composite binder is 30% of the binder, 15% of the reinforcing agent and 55% of the additive, and the adding amount of the composite binder to the super iron concentrate is 0.75%:99.25%;

[0063] In Example 7, the mass percentage of each component of the composite binder is 30% of the binder, 15% of the reinforcing agent and 55% of the additive, and the adding amount of the composite binder to the super iron concentrate is 1.0%:99.0%.

[0064] The reinforcing agent is gelatinized starch, and the -325 mesh content is ≥90%; the additive is slaked lime, and the -200 mesh content is ≥90%.

[0065] The preparation method of the composite binder is that the binder, reinforcing agent and additive are uniformly mixed at room temperature to obtain the finished product.

[0066] The method for using the composite binder comprises the following steps: taking the composite binder and the super concentrate according to the proportions of the above examples, wherein the water content of the super concentrate in the above examples is 8.64%, and the composite binder is uniformly dispersed in the mixture by stirring at room temperature for 12 min; after the mixture is uniformly mixed, the mixture is left for a period of time, and then the mixture after the leaving is balling, and the balling time is 9 min; and the subsequent green ball drying, preheating and roasting processes are the conventional methods.

[0067] Table 2, performance of green balls and finished balls in examples 1-7

[0068]

[0069] It can be seen from the data that the composite binder prepared by the application is used in production, the average drop strength of the green balls is ≥4.5 times·0.5 m -1 , and the average compressive strength of the green balls is ≥11.0 N. In the balling process, it is found that the surface of the green balls becomes smooth after the addition of the organic binder, and the burr phenomenon is obviously reduced. By selecting the formula of the composite binder of the application, the balling explosion in the heating process is avoided. When the amount of the binder component in the composite binder is increased, the average drop strength of the green balls is significantly improved, which shows that CMC-TAPOB has a certain positive effect on the drop strength of the green balls; the increase of the amount of the reinforcing agent significantly improves the compressive strength of the green balls; the increase of the amount of the additive increases the compressive strength of the finished balls and reduces the reduction swelling rate. The composite binder of the application can be used to prepare high-quality super concentrate pellets meeting the standard requirements.

[0070] Example 8

[0071] A composite binder for super concentrate pellets, the mass percentage of each component is: binder 20%, modified starch 10%, limestone 70%; the addition amount: composite binder: super concentrate is 0.75%: 99.25%.

[0072] The preparation method of the composite binder in this example is the same as that in example 1.

[0073] The use method of the composite binder in this example is the same as that in example 1, and the difference lies in that the water content of the super concentrate is 8.87%, the mixing and stirring time is 10 min, and the balling time is 10 min.

[0074] Example 9

[0075] A composite binder for super concentrate pellets, the mass percentage of each component is: binder 20%, puffed starch 5%, modified starch 5%, limestone 10%, and quicklime 60%; the addition amount: composite binder: super concentrate is 0.75%: 99.25%.

[0076] The preparation method of the composite binder in this example is the same as that in example 1.

[0077] The composite binder of the example is used in the same way as in example 1, except that the moisture content of the super concentrate is 8.12%, the mixing and stirring time is 15 min, and the balling time is 9 min.

[0078] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite binder for super iron ore concentrate pellets, characterized in that, Consists of the following components by mass percentage: Binder 20-40 wt% Reinforcing agent 10-20 wt% Additive 40-70 wt% Among them, the binder is N-(1,3,5-tri(4-aminophenoxy)phenyl) carboxymethyl cellulose, namely CMC-TAPOB; The reinforcing agent is one or several of modified starch, puffed starch, gelatinized starch; The additive is one or several of limestone, quicklime, slaked lime.

2. The composite binder for super iron ore concentrate pellets according to claim 1, characterized in that, The synthesis method of CMC-TAPOB is: (1) Dissolve CMC in phosphate buffer solution, the concentration of phosphate buffer solution is 1%~2.5%; the feeding ratio of CMC to phosphate buffer solution is 1:40~60g / mL; (2) Add the phosphate buffer solution containing EDC and NHS drop by drop into the CMC phosphate buffer solution, stir at room temperature for 20~40 minutes; wherein the molar ratio of each raw material is: CMC:EDC=1:2.4~3.0; EDC:NHS=1:5~10; (3) Dissolve TAPOB completely in DMF to form a TAPOB solution, then add it drop by drop into the reaction solution of step (2), the molar ratio of TAPOB to CMC is 1~5:1; (4) After continuous nitrogen and stirring at room temperature for 12-24 hours, pour the reaction mixture into anhydrous ethanol, place until no precipitate is precipitated, filter and dry to obtain the product CMC-TAPOB.

3. The method of claim 1, wherein the composite binder is prepared by the steps of: Mix the binder, reinforcing agent and additive in proportion at room temperature to obtain the finished product; Among them, the particle size specification of the reinforcing agent is-325 mesh content ≥90%; The particle size specification of the additive is-200 mesh content ≥90%.

4. The method of using the composite binder of claim 1, characterized by, Mix the composite binder and super iron concentrate, and the addition amount of the composite binder is 0.5%-1% of the total amount of the composite binder and the super iron concentrate.

5. The method of using a composite binder of claim 4, wherein, Add 0.5-1% of the composite binder to 99.0-99.5% of the super iron concentrate with a water content of 8~9%, mix and stir at room temperature for 10~15 minutes, make the composite binder uniformly dispersed in the mixture, then stand for a certain time; then ball the mixture after standing, the balling time is 9~10 minutes; the subsequent green ball drying, preheating and roasting process is the conventional method.

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