Method for inhibiting ring formation of multi-source metallurgical dust rotary kiln

Abstract

The invention relates to the technical field of metallurgy, in particular to a method for inhibiting ring formation of a multi-source metallurgical dust rotary kiln. The solid burn-off rate (greater than 90%) is optimized by regulating and controlling the rotating speed and the blast volume of the rotary kiln, SiO2 and alkalinity are regulated and controlled, the compressive strength of the briquette is remarkably reduced, and the formation of a low-melting-point silicate liquid phase is effectively inhibited, so that the ring forming tendency is fundamentally reduced.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for suppressing ring formation of multi-source metallurgical dust in rotary kilns. Background Technology

[0002] In the rotary kiln treatment of metallurgical dust, due to the complex composition of raw materials (high Zn, K, and Na content, unburned carbon residue) and special reaction kinetics, rings mainly composed of Fe, FeO, Fe3O4, and low-melting-point silicate phases easily form inside the kiln. These rings severely hinder material transport, interfere with thermal regimes, reduce equipment operating rates, and increase production costs. Existing technologies mostly focus on pellet systems, with insufficient research on the ring formation behavior in the direct treatment of metallurgical dust, and a lack of targeted suppression methods. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a method for suppressing ring formation in rotary kilns containing multi-source metallurgical dust. The method of the present invention can fundamentally reduce the tendency of ring formation.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for suppressing ring formation of multi-source metallurgical dust in rotary kilns, comprising the following steps: The SiO2 and CaO contents in the multi-source metallurgical dust are adjusted; the mass content of SiO2 in the multi-source metallurgical dust is 3-5%; when the mass content of SiO2 in the multi-source metallurgical dust is 3-4%, the mass ratio of CaO to SiO2 is (2-2.5):1; when the mass content of SiO2 in the multi-source metallurgical dust is >4% and ≤5%, the mass ratio of CaO to SiO2 is (1.5-2):1. Then, the multi-source metallurgical dust is placed in a rotary kiln for roasting; During the roasting process, the rotary kiln speed and air volume are adjusted to ensure that the solid burnout rate is >90%. The solid burnout rate is calculated according to formula (1); Equation (1) In formula (1): η Solid carbon burnout rate; C0 represents the percentage of fixed carbon by mass in the raw material before roasting; C1 represents the percentage of fixed carbon in the calcined product by mass.

[0005] Preferably, the rotary kiln rotates at a speed of 0.11-0.2 revolutions per minute.

[0006] Preferably, the blower volume is 105-115 m³ / h. 3 / min.

[0007] Preferably, the multi-source metallurgical dust includes one or more of blast furnace bag dust, gravity dust, converter dry dust, and electric furnace dust.

[0008] Preferably, the roasting temperature is 1180-1220℃.

[0009] Preferably, before being burned, the process further includes pressing the multi-source metallurgical dust into shape.

[0010] Preferably, the method for adjusting the SiO2 and CaO content in the multi-source metallurgical dust includes adding SiO2 and / or CaO to the multi-source metallurgical dust.

[0011] Preferably, the particle size of the multi-source metallurgical dust is 100-160 mesh.

[0012] This invention provides a method for suppressing ring formation in rotary kilns for multi-source metallurgical dust. By adjusting the rotary kiln speed and air volume to optimize the solid burnout rate (>90%), and controlling the SiO2 content and basicity, the compressive strength of the briquettes is significantly reduced, effectively suppressing the formation of low-melting-point silicate liquid phases, thereby fundamentally reducing the tendency to form rings. Attached Figure Description

[0013] Figure 1 XRD patterns of calcined products obtained by changing the silica content (3%, 4%, 5%, 6% or 7%) while maintaining a solid carbon burnout rate of over 90% and a basicity of 2.5. Detailed Implementation

[0014] This invention provides a method for suppressing ring formation of multi-source metallurgical dust in rotary kilns, comprising the following steps: The SiO2 and CaO contents in the multi-source metallurgical dust are adjusted; the mass content of SiO2 in the multi-source metallurgical dust is 3-5%; when the mass content of SiO2 in the multi-source metallurgical dust is 3-4%, the mass ratio of CaO to SiO2 is (2-2.5):1; when the mass content of SiO2 in the multi-source metallurgical dust is >4% and ≤5%, the mass ratio of CaO to SiO2 is (1.5-2):1. Then, the multi-source metallurgical dust is placed in a rotary kiln for roasting; During the roasting process, the rotary kiln speed and air volume are adjusted to ensure that the solid burnout rate is >90%. The solid burnout rate is calculated according to formula (1); Equation (1) In formula (1): η Solid carbon burnout rate; C0 represents the percentage of fixed carbon by mass in the raw material before roasting; C1 represents the percentage of fixed carbon in the calcined product by mass.

[0015] In this invention, the multi-source metallurgical dust preferably includes one or more of blast furnace baghouse dust, gravity dust, converter dry process dust, and electric furnace dust; in this invention, "multi-source metallurgical dust" means that this invention is applicable to a variety of metallurgical dusts. The particle size of the multi-source metallurgical dust is preferably 100-160 mesh (under 100 mesh and over 160 mesh). In this invention, the blast furnace baghouse dust comes from blast furnace ironmaking, the converter dry process dust comes from converter steelmaking, the electric furnace dust comes from electric arc furnace steelmaking, and the gravity dust is a type of dust-like solid waste collected by gravity settling during the blast furnace ironmaking process, mainly originating from core stages such as raw material processing, furnace operation, and iron and slag tapping in blast furnace ironmaking. The electric furnace dust can specifically be zinc-containing dust.

[0016] In an embodiment of the present invention, the multi-source metallurgical dust specifically refers to blast furnace bag dust and zinc-containing dust, wherein blast furnace bag dust is the main carbon source and zinc-containing dust is the main source of zinc; the carbon-oxygen molar ratio (C / O) of the blast furnace bag dust and zinc-containing dust is preferably 0.9:1.

[0017] In a specific embodiment, the mass content of SiO2 in the multi-source metallurgical dust can be 3%, 3.5%, 4%, 4.5%, or 5%.

[0018] In this invention, when the mass content of SiO2 in the multi-source metallurgical dust is 3-4%, the mass ratio of CaO to SiO2 is (2-2.5):1. In specific embodiments, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5:1. In this invention, when the mass content of SiO2 in the multi-source metallurgical dust is >4% and ≤5%, the mass ratio of CaO to SiO2 is (1.5-2):1. In specific embodiments, it can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1.

[0019] In this invention, the preferred method for adjusting the SiO2 and CaO content in multi-source metallurgical dust includes adding SiO2 and / or CaO to the multi-source metallurgical dust.

[0020] In this invention, SiO2 and / or CaO are added to mix the materials evenly.

[0021] In this invention, prior to burning, it is preferable to further compress the multi-source metallurgical dust into a molded shape. This invention does not have special requirements for the molding process; a molding process well-known in the art can be used. In an embodiment of this invention, specifically, the multi-source metallurgical dust is pressed into a cylindrical sample with a diameter of Φ10mm × 10mm under a pressure of 15MPa.

[0022] In this invention, the rotary kiln speed and air volume are adjusted during the roasting process to ensure that the solid burnout rate is >90%.

[0023] In this invention, the rotational speed of the rotary kiln is preferably 0.11-0.2 revolutions / min, and in specific embodiments, it can be 0.11, 0.12, 0.13, 0.15, 0.16, 0.18, or 0.2 revolutions / min. By controlling the rotational speed of the rotary kiln within the above range, this invention ensures that the material has sufficient residence time (approximately 120 minutes) in the kiln to complete the reaction, while avoiding excessive residence time leading to over-sintering. Furthermore, it prevents excessively high rotational speeds from causing material agglomeration and forming pellets, which would hinder internal carbon reduction, and also prevents excessively low rotational speeds from significantly reducing material transport efficiency and affecting overall production capacity.

[0024] In this invention, the blower volume is preferably 105-115 m³ / h. 3 / min, which in a specific embodiment can be 105, 110, or 115m. 3 / min. This invention, by controlling the air volume within the above range, can prevent excessive air volume from exacerbating dust loss and disrupting the material balance within the kiln; at the same time, it can also avoid insufficient air volume from failing to meet the oxygen supply required for combustion, leading to a decrease in solid burnout rate. This invention optimizes the air volume to balance reaction efficiency and material stability while ensuring sufficient reaction.

[0025] In this invention, the roasting temperature is preferably 1180-1220℃, and in specific embodiments it can be 1180, 1190, 1200, 1210 or 1220℃.

[0026] This invention controls the solid burnout rate (>90%), the SiO2 mass content in multi-source metallurgical dust, and the CaO to SiO2 mass ratio, which can significantly reduce the compressive strength of the briquettes and effectively suppress the formation of low-melting-point silicate liquid phases, thereby fundamentally reducing the tendency for ring formation. In the embodiments of this invention, the solid burnout rate is specifically controlled by simulating the rotary kiln process in a laboratory experiment and by controlling the roasting time.

[0027] This invention uses compressive strength as a key indirect indicator of ring formation tendency. Samples with significantly increased compressive strength indicate excessive formation of low-melting-point silicate liquid phase and severe adhesion, resulting in a high tendency for ring formation. Through extensive experiments, this invention sets the critical value of compressive strength of the calcined product at 500 N; below this value, the tendency for ring formation is considered to be effectively suppressed.

[0028] The following detailed description of the method for suppressing ring formation of multi-source metallurgical dust in rotary kilns provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0029] Example 1 S1. Pretreatment of blast furnace bag filter ash and zinc-containing dust: The blast furnace bag filter ash and zinc-containing dust were dried at 105℃ to constant weight to eliminate the influence of moisture on mixing uniformity and proportioning accuracy. Subsequently, the raw materials were ground using a ball mill and uniformly passed through a 100-160 mesh sieve (below 100 mesh and above 160 mesh) to control the particle size distribution and ensure consistent physical properties, laying the foundation for subsequent uniform mixing. Then, precise proportioning was performed. The mixture was stirred for 1-2 hours using a mixer to ensure uniform mixing of the blast furnace bag filter ash and zinc-containing dust, fixing the carbon-oxygen molar ratio (C / O) of blast furnace bag filter ash and zinc-containing dust at 0.9. The SiO2 content and alkalinity (i.e., the mass ratio of CaO to SiO2) of the mixture were adjusted by adding pure reagents SiO2 and CaO. Specifically, the SiO2 content was set to 3.0%, and the alkalinity was set to 2.5. Uniformity of the mixture was ensured in all experimental groups.

[0030] S2. Load the uniformly mixed raw materials from S1 into a mold and press them into a cylindrical sample with a diameter of 10mm × 10mm under a pressure of 15MPa.

[0031] S3. Place the compressed briquettes prepared in S2 into a high-temperature furnace and calcine them at 1200°C by introducing nitrogen gas (the purpose is to maintain a reducing environment and prevent oxidation; industrial rotary kilns use limited air). Control the calcine time to ensure that the solid burnout rate of the sample reaches and is maintained above 90%.

[0032] After calcination, the sample was cooled to room temperature and its compressive strength was tested using a compressive strength tester. The compressive strength was 391 N.

[0033] Examples 2-5 The only difference from Example 1 is the solid burnout rate, SiO2 content, or alkalinity, as detailed in Table 1.

[0034] Comparative Examples 1-10 The only difference from Example 1 is the solid burnout rate, SiO2 content, or alkalinity, as detailed in Table 1.

[0035] Comparative Example 10 The only difference from Example 1 is that the solid burnout rate is 67.8%, and the compressive strength is significantly higher than that when the solid carbon burnout rate is >90%.

[0036] Table 1. Operating conditions and compressive strength of calcined products in the examples and comparative examples.

[0037] This invention uses compressive strength as a key indirect indicator of ring formation tendency: samples with significantly increased compressive strength indicate excessive formation of low-melting-point silicate liquid phase and severe adhesion, resulting in a high tendency for ring formation. As shown in Table 1, this invention significantly reduces ring formation tendency by controlling the SiO2 mass content, maintaining a suitable CaO to SiO2 mass ratio, and achieving a solid burnout rate >90%. In contrast, Comparative Examples 1-10 exhibited a significant ring formation tendency due to lower burnout rates or unsuitable CaO to SiO2 mass contents.

[0038] XRD analysis was performed on some of the calcined products, and the phase composition of the calcined products was analyzed as follows: Figure 1 As shown. Figure 1 XRD patterns of calcined products obtained by changing the silica content (3%, 4%, 5%, 6% or 7%) while maintaining a solid carbon burnout rate of over 90% and a basicity of 2.5.

[0039] Depend on Figure 1 It is evident that the increase in SiO2 content drives the evolution of the phase system from "metallic iron + a small amount of silicate binder phase" to "calcium iron pyroxene / diopside + encapsulated metallic iron". During the cooling process, these increasingly numerous and high-strength calcium silicate crystals intertwine to form an increasingly continuous and robust framework, which is the fundamental reason why the macroscopic compressive strength of the compact increases monotonically with the increase of SiO2 content.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for suppressing ring formation of multi-source metallurgical dust in a rotary kiln, characterized in that, Includes the following steps: The SiO2 and CaO contents in the multi-source metallurgical dust are adjusted; the mass content of SiO2 in the multi-source metallurgical dust is 3-5%; when the mass content of SiO2 in the multi-source metallurgical dust is 3-4%, the mass ratio of CaO to SiO2 is (2-2.5):1; when the mass content of SiO2 in the multi-source metallurgical dust is >4% and ≤5%, the mass ratio of CaO to SiO2 is (1.5-2):

1. Then, the multi-source metallurgical dust is placed in a rotary kiln for roasting; During the roasting process, the rotary kiln speed and air volume are adjusted to ensure that the solid burnout rate is >90%. The solid burnout rate is calculated according to formula (1); Equation (1) In formula (1): η Solid carbon burnout rate; C0 represents the percentage of fixed carbon by mass in the raw material before roasting; C1 represents the percentage of fixed carbon in the calcined product by mass.

2. The method according to claim 1, characterized in that, The rotary kiln rotates at a speed of 0.11-0.2 revolutions per minute.

3. The method according to claim 2, characterized in that, The blower volume is 105-115m³. 3 / min.

4. The method according to claim 1, characterized in that, The multi-source metallurgical dust includes one or more of the following: blast furnace bag dust, gravity dust, converter dry dust, and electric furnace dust.

5. The method according to claim 1, characterized in that, The roasting temperature is 1180-1220℃.

6. The method according to claim 1, characterized in that, Before being burned, the process also includes pressing the multi-source metallurgical dust into shape.

7. The method according to claim 1, characterized in that, The method for adjusting the SiO2 and CaO content in multi-source metallurgical dust includes adding SiO2 and / or CaO to the multi-source metallurgical dust.

8. The method according to claim 1, characterized in that, The particle size of the multi-source metallurgical dust is 100-160 mesh.

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