A balling process based on strengthening balling by fiberizing bentonite slurry

Abstract

This invention discloses a pellet preparation process based on fibrous bentonite slurry-enhanced pelletizing, belonging to the field of pellet preparation technology in the iron and steel industry. The process includes: wetting iron concentrate to 2.5%~3.5% moisture content; mixing with a first portion of bentonite, followed by sequential high-intensity mixing and milling to obtain pelletizing material; feeding the material into a pelletizer; after the mother pellets are prepared, atomized spraying of fibrous bentonite slurry replaces the addition of water during pelletizing, allowing the pellets to grow to qualified green pellets. The fibrous bentonite slurry is prepared by mixing a second portion of bentonite and water at a mass ratio of 1:5~20, and stirring for 4~6 minutes at a revolution speed of 120~130 r / min and a rotation speed of 280~290 r / min. This invention achieves uniform distribution of bentonite within the pellets through graded moisture control and precise spraying, reducing the total bentonite usage from 1.6% to 1.2% while ensuring pellet quality, significantly reducing bentonite consumption and achieving cost reduction, efficiency improvement, energy conservation, and emission reduction in pellet production.

Description

Technical Field

[0001] This invention relates to the field of pellet preparation technology, specifically to a pellet preparation process based on fibrous bentonite slurry-enhanced pelletizing. Background Technology

[0002] Iron pellets, as an important iron-containing raw material for blast furnace ironmaking, have significant advantages such as high iron grade, low levels of harmful elements, low slag content, and low pollution emissions. Currently, the steel industry is gradually promoting green and low-carbon development, and vigorously developing pelletizing technology and improving pellet quality are crucial for achieving the goals of "carbon neutrality and peak carbon emissions." In pellet production, bentonite is the most widely used binder, characterized by good pelletizing properties, low price, and wide availability. However, bentonite contains 45%-65% SiO2 impurities that remain in the pellets, reducing the iron grade and consequently increasing the fuel ratio and slag volume during ironmaking. Production results show that for every 1% increase in bentonite consumption, the iron grade of the pellets decreases by 0.6-0.7%, resulting in a significant increase in the production cost per ton of iron.

[0003] With the depletion of high-quality bentonite resources and the worsening of bentonite quality, the adverse effects on pellet performance have intensified. To address this problem, metallurgists have long sought new binder materials to replace or partially replace bentonite, but widespread application has yet to be achieved. In actual production, the price advantage of bentonite makes it an irreplaceable binder. Therefore, given that bentonite cannot be replaced, fully utilizing its role in pelletizing, thereby reducing its usage, is one of the effective ways to improve the iron content of pellets and achieve energy conservation and emission reduction.

[0004] In China, bentonite has long been used as a binder in pellet production, with most users exceeding 10 kg·t⁻¹ and even reaching as high as 20 kg·t⁻¹. This is significantly lower than the advanced international level of 5-10 kg·t⁻¹, indicating potential for further reduction. Ripke et al. proposed the bentonite fibrous structure theory: when bentonite is wetted, each layer absorbs water and expands, weakening the electrostatic attraction between the layers. Simultaneously, under mechanical stirring, when the external force exceeds the electrostatic attraction between the bentonite layers, the bentonite layers slide, forming a fibrous structure. This significantly improves the bonding effect and enhances pellet performance. Summary of the Invention

[0005] The purpose of this invention is to provide a pellet preparation process based on fibrous bentonite slurry-reinforced pelletizing to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a pellet preparation process based on fibrous bentonite slurry-reinforced pelletizing, as detailed below:

[0007] (a) Wetting the iron concentrate to a suitable pelletizing moisture content to obtain wetted iron concentrate;

[0008] (b) The wetted iron concentrate is mixed with the first portion of bentonite, and then subjected to high-intensity mixing and grinding in sequence to obtain pelletizing material;

[0009] (c) The pelletizing material is fed into a pelletizing machine for pelletizing, first preparing mother pellets;

[0010] (d) After the preparation of the mother pellets is completed, atomized spraying of fibrous bentonite slurry into the pelletizing machine replaces the addition of water for pelletizing, so that the pellets grow to qualified green pellets; wherein, the fibrous bentonite slurry is a stable, uniform, and sediment-free slurry prepared by mixing the second part of bentonite with water under the action of mechanical stirring force;

[0011] (e) The qualified green pellets are preheated and roasted to obtain finished pellets.

[0012] Preferably, the suitable pelletizing moisture content in step (a) is 2.5% to 3.5% of the iron concentrate mass, and the total moisture content of the green pellets is controlled at 8% to 9%.

[0013] Preferably, the time for vigorous mixing in step (b) is 8 to 12 minutes, and the time for wet grinding is 15 to 20 minutes.

[0014] Preferably, the pelletizing machine in step (c) is a disc pelletizing machine with a diameter of 1000 mm, a side height of 200 mm, an inclination angle of 45°, and a rotation speed of 17 r / min; the total pelletizing time is 12 minutes, of which 2 minutes are for preparing the mother pellet, 8 minutes are for growing the mother pellet, and 2 minutes are for compacting the green pellet.

[0015] Preferably, the preparation process of the fibrous bentonite slurry in step (d) is as follows: the second part of bentonite and water are mixed at a mass ratio of 1:5 to 20, and stirred in a mixer for 4 to 6 minutes. The revolution speed of the mixer is 120 to 130 r / min, and the rotation speed is 280 to 290 r / min.

[0016] Preferably, the spraying pressure of the fibrous bentonite slurry in step (d) is 0.3 to 0.5 MPa, and the spraying angle is 60° to 80° with the surface of the pelletizing machine.

[0017] Preferably, the diameter of the qualified green balls in step (d) is 12-16 mm.

[0018] Preferably, in step (e), the preheating temperature is 950°C, the preheating time is 8 minutes, the calcination temperature is 1250°C, and the calcination time is 12 minutes.

[0019] The present invention also proposes a pellet prepared based on the above-described preparation process.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The preparation process of fibrous bentonite slurry does not add organic additives such as CMC. By optimizing mechanical shear parameters (mixer revolution speed 120-130r / min, rotation speed 280-290r / min, time 4-6min), bentonite is efficiently fibrosed in water to form a stable, uniform, and sediment-free slurry.

[0022] 2. Graded Moisture Control and Precise Spraying: The moisture content of the green pellets is stably controlled at 8-9%. First, the iron concentrate is dried and then pre-wetted to 2.5-3.5% moisture content to provide conditions for nucleation and mother pellet formation. The remaining 5.5-6.5% moisture required for pellet formation is mixed with a certain mass fraction of bentonite according to the slurry ratio (bentonite:water = 1:5-20). Under the action of mechanical stirring, fibrous bentonite slurry is prepared. When the mother pellet preparation is completed and the mother pellets begin to grow, it is atomized and sprayed to ensure that the fibrous bentonite is evenly distributed inside the pellets and maximizes its effectiveness.

[0023] 3. Optimization of bentonite usage structure: The bentonite required for pelleting is divided into two parts: basic premix and slurry spraying. By optimizing the ratio of basic premix and slurry spraying, the total amount of bentonite used is reduced. Attached Figure Description

[0024] Figure 1 This is a flowchart of the pellet preparation process. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention proposes a pellet preparation process based on fibrous bentonite slurry-reinforced pelletizing, specifically including the following steps:

[0027] (1) The moisture content of the green pellets is controlled at 8-9%. The iron concentrate is moistened to a suitable pelletizing moisture content of 2.5-3.5%, leaving a moisture space of 5.5-6.5% for subsequent spraying of bentonite slurry;

[0028] (2) The moistened iron concentrate and bentonite of a certain mass ratio are put into a high-power mixer and mixed for 8-12 minutes;

[0029] (3) Place the mixed material into a grinding mill and grind for 15-20 minutes;

[0030] (4) Make pellets on a disc pelletizer with parameters of φ1000mm, side height 200mm, inclination angle 45° and rotation speed 17r / min. After the preparation of the mother pellets is completed (2min), spray fibrous bentonite slurry at a pressure of 0.3-0.5MPa and an angle of 60-80° to replace the addition of water for pelletizing, so that the pellets grow to qualified green pellets with a diameter of 12-16mm. The green pellet growth time is 8min and the compaction time is 2min.

[0031] (5) Use a round hole sieve to screen out green balls of qualified particle size and test the drop strength and compressive strength of green balls. The preheating and roasting test is carried out in a two-end horizontal furnace with a preheating temperature of 950℃ and a preheating time of 8min, a roasting temperature of 1250℃ and a roasting time of 12min. Use an intelligent briquetting machine to determine the compressive strength of the finished pellets.

[0032] The pellets prepared by the above method were subjected to the following tests:

[0033] With a total bentonite content of 1.6% (percentage of iron concentrate mass), the ratios of the first part of bentonite (conventional addition) and the second part of bentonite (fiberized slurry spraying) were adjusted respectively, and the test results are shown in Table 1.

[0034] Table 1. Effect of fiberized bentonite dosage on pellet performance

[0035] 1.6 1.6 0 3.6 12.9 2730 1.6 0.4 1.2 3.8 12.8 2777 1.6 0.6 1.0 4.1 13.2 2791 1.6 1.0 0.6 4.8 13.5 2855 1.6 1.2 0.4 5.3 14.1 2977 1.6 1.3 0.3 4.7 13.2 2789

[0036] As shown in Table 1, when the amount of fiberized bentonite slurry is 0.4% (i.e. 25% of the total amount), the overall performance of the pellets is optimal, and the drop strength, compressive strength and finished pellet strength of the green pellets are significantly better than those of the conventional process (when the amount of fiberized slurry is 0%).

[0037] Table 2. Effects of fiberized bentonite on bentonite consumption reduction

[0038] 1.6 1.6 0 3.6 12.9 2730 1.3 0.9 0.4 3.9 13.4 2822 1.2 0.8 0.4 3.6 12.8 2736 1.1 0.7 0.4 3.0 11.7 2504

[0039] As shown in Table 2, spraying with 0.4% fiberized bentonite slurry can reduce the total amount of bentonite used from 1.6% to 1.2%, saving 25%, and the quality of the pellets is almost the same as that obtained by conventional methods (total amount of bentonite used is 1.6%).

[0040] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pellet preparation process based on fibrous bentonite slurry-reinforced pelletizing, characterized in that: (a) Wetting the iron concentrate to a suitable pelletizing moisture content to obtain wetted iron concentrate; (b) The wetted iron concentrate is mixed with the first portion of bentonite, and then subjected to high-intensity mixing and grinding in sequence to obtain pelletizing material; (c) The pelletizing material is fed into a pelletizing machine for pelletizing, first preparing mother pellets; (d) After the preparation of the mother pellets is completed, atomized spraying of fibrous bentonite slurry into the pelletizing machine replaces the addition of water for pelletizing, so that the pellets grow to qualified green pellets; wherein, the fibrous bentonite slurry is a stable, uniform, and sediment-free slurry prepared by mixing the second part of bentonite with water under the action of mechanical stirring force; (e) The qualified green pellets are preheated and roasted to obtain finished pellets.

2. The process according to claim 1, characterized in that: The suitable pelletizing moisture content in step (a) is 2.5% to 3.5% of the iron concentrate mass, and the total moisture content of the green pellets is controlled at 8% to 9%.

3. The process according to claim 1, characterized in that: The vigorous mixing time in step (b) is 8 to 12 minutes, and the wet grinding time is 15 to 20 minutes.

4. The process according to claim 1, characterized in that: The pelletizing machine mentioned in step (c) is a disc pelletizing machine with a diameter of 1000mm, a side height of 200mm, an inclination angle of 45°, and a rotation speed of 17r / min; the total pelletizing time is 12 minutes, of which 2 minutes are for preparing the mother pellet, 8 minutes are for growing the mother pellet, and 2 minutes are for compacting the green pellet.

5. The process according to claim 1, characterized in that: The preparation process of the fiberized bentonite slurry in step (d) is as follows: the second part of bentonite and water are mixed at a mass ratio of 1:5 to 20, and stirred in a mixer for 4 to 6 minutes. The revolution speed of the mixer is 120 to 130 r / min, and the rotation speed is 280 to 290 r / min.

6. The process according to claim 1, characterized in that: The spraying pressure of the fibrous bentonite slurry in step (d) is 0.3 to 0.5 MPa, and the spraying angle is 60° to 80° with the surface of the pelletizing machine.

7. The pellet preparation process according to claim 1, characterized in that, The diameter of the qualified green balls mentioned in step (d) is 12-16 mm.

8. The pellet preparation process according to claim 1, characterized in that, In step (e), the preheating temperature is 950°C and the preheating time is 8 minutes. The calcination temperature is 1250°C and the calcination time is 12 minutes.

9. A pellet, characterized in that, It is prepared using the preparation process described in any one of claims 1-8.

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