Pellet preparation method using iron-containing composite binder as pellet binder

Abstract

The invention discloses a pellet preparation method using an iron-containing composite binder as a pellet binder. The method comprises the following steps: firstly, selecting fine iron powder as a main pelletizing base material, preparing an iron-containing composite binder from bentonite and an iron-containing binder, and then pretreating the iron-containing composite binder, specifically, drying at a specific temperature, and then finely grinding the iron-containing composite binder to a required particle size. And finally, the pretreated iron-containing composite binder is added into the fine iron powder base material according to the proportion, and pelletizing is carried out after even mixing. Aiming at the core problem that the traditional bentonite binder reduces the grade of the pellets, the method provided by the invention improves the iron grade, optimizes the consolidation mechanism and performance, and obviously improves the compressive strength of the finished pellets.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel smelting, and specifically provides a preparation method of oxidized pellet. BACKGROUND

[0002] Pellet is an indispensable high-quality furnace charge for modern blast furnace ironmaking. Binder is one of the core raw materials for pellet production, and its performance directly affects the quality and economic benefits of the pellet. At present, in the production of pellet, bentonite is used as the main binder, which will introduce a large amount of gangue components such as SiO2 and Al2O3, which not only directly reduces the iron grade of the pellet, violates the "precious material policy" of the blast furnace, but also causes the cost and energy consumption to rise in the stage of blast furnace ironmaking. Therefore, developing a new type of binder system that can not only maintain or even improve the physical and metallurgical properties of the pellet, but also effectively improve the iron grade of the pellet and control the cost, has become a technical difficulty and research focus in the field. SUMMARY

[0003] In view of the deficiencies of the prior art, the present application provides a preparation method of pellet using iron-containing composite binder as the binder of the pellet. The iron-containing composite binder is pretreated and finely ground, which can improve the pelletizing effect, improve the iron grade of the pellet, reduce the silicon content of the pellet, and reduce the comprehensive use cost of the pellet binder. The present application is realized by the following technical scheme: a preparation method of pellet using iron-containing composite binder as the binder of the pellet, the iron-containing composite binder is an iron-containing composite binder made by adding iron-containing binder to bentonite as a reference, which aims to replace part of the bentonite to meet the requirements of entering the furnace and reduce the amount of bentonite.

[0004] A preparation method of pellet using iron-containing composite binder as the binder of the pellet, comprising the following steps: Step 1) selecting iron concentrate powder as the pelletizing base material; the mass ratio of the components of the iron concentrate powder is, for example: 65.1%-68.3% TFe, 0.5%-1.2% CaO, 0.6%-1.3% MgO, 0.8%-2.4% SiO2, 0.3%-1.1% Al2O3, 7.5%-9% water, and the proportion of solid components with a particle size of less than 200 mesh is ≥90%; Step 2) pretreating the selected iron-containing composite binder, and then finely grinding; the iron-containing composite binder is made by uniformly mixing bentonite and iron-containing binder, and the mass content of the iron-containing composite binder relative to the pelletizing base material is 1%-2.5%; Step 3) mixing the treated iron-containing binder and the pelletizing base material to pelletize.

[0005] Further, the pretreatment of step 2) is as follows: the iron-containing composite binder is dried in a drying oven, the drying temperature is 105 ± 5℃, and the drying time is 2-4h.

[0006] Further, the fine grinding process of step 2) is as follows: the pretreated iron-containing composite binder is finely ground to 200 mesh, and the proportion of particle size less than 200 mesh is ≥90%, based on the mass content of the pelletizing base material, 0.5-1% bentonite and 1-2.0% iron-containing binder are added and uniformly mixed to form the iron-containing composite binder. Preferably, the iron-containing composite binder contains 0.5% bentonite.

[0007] Further, the pelletizing process of step 3) is as follows: the binder is uniformly mixed with the pelletizing base material, and the pelletizing is carried out on a disc pelletizer, and the moisture content of the green ball is controlled to be >7.5% during the pelletizing process; the green ball is screened, and the 10-12.5mm balls are selected for preheating and roasting. Preferably, the preheating temperature is 900±10℃, the time is 15-20min, the roasting temperature is 1275±5℃, and the time is 30-40min. Preferably, the raw material for pelletizing needs to be uniformly mixed in a mixer for 6h to avoid the aggregation of the binder and cause the performance of the pellets to be inconsistent. The disc pelletizer with a diameter of 1000mm and an inclination angle of 47° is selected for pelletizing. The pellet preparation needs to go through three processes: generation of mother balls (3-5min), growth of mother balls (8-15min), and anhydrous compaction (10-12min).

[0008] The present application processes low-nickel high-iron material into iron-containing composite binder, partially replaces traditional bentonite, and exhibits significant advantages in pellet preparation: the composite binder can effectively improve the granulation effect and improve the green ball forming efficiency; meanwhile, its high-iron low-silicon characteristics help to reduce the silicon dioxide content of the pellets and improve the iron grade. In terms of economy, the raw material cost of the iron-containing composite binder is significantly lower than that of bentonite, which can effectively reduce the comprehensive production cost of the pellets. The iron-containing composite binder has excellent bonding performance, which not only optimizes the pelletizing mode of the fine powder and speeds up the pelletizing speed, but also provides good technical and economic feasibility for pellet production due to its cost advantage. DETAILED DESCRIPTION

[0009] The present application will be further described in detail below with specific examples.

[0010] Example 1 A method for preparing pellets using an iron-containing composite binder as a pellet binder, the specific steps are as follows: (1) Base material treatment Two different grades of iron concentrate powder A and B are selected, and mixed uniformly according to the ratio of 3:7 as the balling base material. Generally, more than two specifications of iron concentrate powder are used to facilitate the adjustment of the composition, and the performance of different iron concentrate powders will be different. The performance of the balling base material is improved by matching the performance of the balling base material. The composition of the iron concentrate powder is shown in Table 1.

[0011] Table 1 Composition of iron concentrate powder (%)

[0012] (2) Pretreatment of iron-containing composite binder The selected iron-containing composite binder is dried in a drying oven at a temperature of 105°C for 2h, and then finely ground to ensure that the proportion of particle size less than 200 mesh is ≥90%. The iron-containing composite binder is made by adding iron-containing binder to 0.5% bentonite as a reference. The purpose is to replace part of the bentonite pellets, and the physical properties still meet the requirements of the furnace, and the amount of bentonite is reduced. The composition of the binder is shown in Table 2.

[0013] Table 2 Composition of binder (%)

[0014] (3) Mixing Weigh 450g of iron concentrate powder A, 1050g of iron concentrate powder B, 2% (relative to the percentage content of the balling base material) iron-containing composite binder 30g, and mix the iron-containing raw material and the binder in the mixing machine for 6h to avoid the phenomenon of agglomeration of the binder, which causes the performance of the pellets to be inconsistent.

[0015] (4) Balling The balling base material is mixed uniformly, and the balling is carried out on the disc balling machine. The pellet preparation needs to go through three processes: generation of mother ball (3-5min), growth of mother ball (8-15min), and anhydrous compaction (10-12min).

[0016] (5) Green ball drying Because water is added during the preparation of the pellets, the green balls need to be dried in a blast drying oven at a temperature of 200°C for 2h to remove the free water inside. The surface water vapor pressure of the green ball is greater than the water vapor partial pressure in the drying medium, and the water is carried away by the blast air flow in the drying oven to obtain dry balls.

[0017] (6) Dry ball preheating and roasting The green balls prepared in step (4) are sieved, and the 10-12.5mm balls are selected. First, the preheating treatment is carried out in the preheating furnace, and then the roasting is carried out in the roasting furnace. The preheating and roasting parameters are shown in Table 3.

[0018] Table 3 preheating roasting parameters

[0019] (7) Performance detection The green balls prepared in step (4) were subjected to drop compression strength test, and 10 green balls of uniform size and appropriate shape were selected for testing and the average value was taken. The pellets (hard balls) after preheating and roasting in step (6) were subjected to compression strength test, and 10 hard balls of uniform size and appropriate shape were selected for testing and the average value was taken. The test results are shown in Table 4 below.

[0020] Table 4 performance indicators of pellets

[0021] (8) Hard ball iron grade detection The hard balls prepared in step (6) were detected to obtain the iron grade as shown in Table 5 below Table 5 iron grade parameters of pellets

[0022] In this embodiment, balling experiments of ordinary bentonite and balling experiments of iron-containing composite binder were carried out, and performance detection was carried out. Compared with higher content of bentonite, lower content of iron-containing composite binder can improve the physical properties and total iron grade of pellets. After adding 2% iron-containing composite binder, compared with two groups of different proportions of single bentonite, the drop number and green ball compression strength are all enhanced, and the compression strength of the hard balls after roasting is greater than that of the pellets using only bentonite. This is because the pellets using only bentonite have low grade and high silicon content, which makes part of Fe3O4 generate calcium iron olivine mineral, hinders the oxidation of Fe3O4 to Fe2O3, and thus affects the recrystallization connection of Fe2O3. As can be seen from Tables 4 and 5, after roasting using iron-containing composite binder, not only the requirements for entering the furnace are met, but also the iron grade is increased by 1.26% compared with using single bentonite. Compared with 2.5% bentonite, the present steel plant adds bentonite based on this, compared with higher content of bentonite, lower content of iron-containing composite binder can not only improve the total iron grade of pellets, but also improve the physical properties of pellets. The iron-containing composite binder has excellent binding performance, can significantly increase the iron grade of oxidized pellets, replace part of bentonite to reduce the silicon dioxide content, and cooperate with its cost advantage, to provide good technical and economic feasibility for pellet production.

[0023] Example 2 Take 450 g of iron concentrate A, 1050 g of iron concentrate B, 1.5% (percentage content relative to the balling base) iron-containing composite binder 22.5 g, wherein the fixed bentonite content is 0.5%, the iron-containing base is treated in the same way as in Example 1, the preheating and roasting system is the same as in Example 1, only the content of the iron-containing composite binder is changed, and the balling performance index is shown in Table 6.

[0024] Table 6: Performance index of the ball

[0025] (8) Detection of the iron grade of the sintered ball The sintered ball prepared in step (6) is detected to obtain the iron grade as shown in Table 7 Table 7: Iron grade parameters of the ball

[0026] In this embodiment, balling experiments of ordinary bentonite and iron-containing composite binder are respectively carried out, and performance detection is carried out. As can be seen from Table 6, after adding 1.5% iron-containing composite binder, compared with adding 2.5% single bentonite, the falling number of green ball and the green ball crushing strength are reduced, and the crushing strength of the sintered ball after roasting is also slightly decreased, but the iron grade of the ball is increased; after adding 2.5% iron-containing composite binder, compared with adding single bentonite, the falling number of green ball, green ball crushing strength, sintered ball crushing strength and iron grade of the ball are all improved.

[0027] 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 method for preparing pellets using an iron-containing composite binder as a pellet binder, characterized in that, Includes the following steps: Step 1) Select iron concentrate as the pelletizing base material; the iron concentrate has the following composition by mass ratio: 65.1-68.3% TFe, 0.5-1.2% CaO, 0.6-1.3% MgO, 0.8-2.4% SiO2, 0.3-1.1% Al2O3, 7.5-9% water, and the proportion of solid components with a particle size smaller than 200 mesh is ≥90%; Step 2) Pre-treat the selected iron-containing composite binder and then finely grind it; wherein the iron-containing composite binder is prepared by mixing bentonite and iron-containing binder, and the mass content of the iron-containing composite binder relative to the pelletizing base material is 1%-2.5%; Step 3) Mix the treated iron-containing binder with the pelletizing base material to form pellets; The iron-containing binder has the following composition by mass: 54.31% TFe, 12.47% Al2O3, 0.17% CaO, 1.11% MgO, 2.33% SiO2, 0.068% K2O, 0.212% TiO2, 0.018% S, 0.018% P, and 0.86% NiO.

2. The preparation method according to claim 1, characterized in that, Step 1) describes a pelletizing base material that is a mixture of two or more iron concentrates of different specifications to achieve an optimized raw material ratio.

3. The preparation method according to claim 1, characterized in that, Step 2) The pretreatment is as follows: the iron-containing composite adhesive is dried in a drying oven at a temperature of 105±5℃ for 2-4 hours.

4. The preparation method according to claim 1, characterized in that, Step 2) The fine grinding process is as follows: the pretreated iron-containing composite binder is finely ground to 200 mesh, and the proportion of particles smaller than 200 mesh is ≥90%. Based on the mass content of the pelletizing base material, 0.5-1% bentonite and 1-2.0% iron-containing binder are added and mixed to prepare the iron-containing composite binder.

5. The preparation method according to claim 4, characterized in that, Based on the mass content of the pelletizing base material, the iron-containing composite binder contains 0.5% bentonite.

6. The preparation method according to claim 1, characterized in that, Step 3) The pelletizing process is as follows: the binder and pelletizing base are mixed evenly, and pellets are made on a disc pelletizer. During the pelletizing process, the moisture content of the green pellets is controlled to be >7.5%. The green pellets are sieved, and pellets with a diameter of 10-12.5 mm are selected and preheated and calcined.

7. The preparation method according to claim 6, characterized in that, In step 3), the raw materials for pelletizing need to be mixed in a mixer for 6 hours; a disc pelletizer with a diameter of 1000 mm and an inclination angle of 47° is selected for pelletizing.

8. A method for preparing pellets using an iron-containing composite binder as a pellet binder according to claim 6, characterized in that, The preheating temperature is 900±10℃ and the time is 15-20 min, and the calcination temperature is 1275±10℃ and the time is 30-40 min.

9. The preparation method according to claim 1, characterized in that, The composition of bentonite by mass is as follows: 1.80% TFe, 17.11% Al2O3, 4.44% CaO, 0.81% MgO, 68.33% SiO2, 0.016% K2O, 1.63% Na2O, 1.83% TiO2, 0.081% S, and 0.114% P.

10. Pelletizing pellets prepared by a method for preparing pellets using an iron-containing composite binder as a pellet binder according to any one of claims 1-9.

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