A fine grinding method for self-produced coke powder

Abstract

This application provides a method for finely grinding self-produced coke fines, comprising the following steps: Step S1, coke produced from the coking process is screened at least twice to obtain coke fines; Step S2, the coke fines are finely ground using a ball mill to obtain coke fines slurry; Step S3, the coke fines slurry is fed into a hydrocyclone for classification, and the overflow of the hydrocyclone is a fine-grained slurry; Step S4, the fine-grained slurry is concentrated and filtered to produce fine coke fines. This method can develop a high-quality pulverized coal resource for blast furnace injection systems and can be applied to industrial production, solving the problem of imbalance between the production and consumption of self-produced coke fines in steel companies.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, and more specifically, to a fine grinding method for self-produced coke powder. Background Technology

[0002] Coking, ironmaking, sintering, and pelletizing are essential processes in large steel plants. For ironmaking, the price difference between coal and coke is significant due to limitations in resource availability and manufacturing processes. In the blast furnace pulverized coal injection process, using a mixture of bituminous and anthracite pulverized coal is currently the most mature technology. Considering cost and social resources, some CDQ powder (dust from the dry quenching system in coking) and semi-coke are also added to reduce the cost of the mixed pulverized coal. However, coke fines, due to their extremely low grindability and tendency to wear down equipment, have not yet been widely used. Coke fines are a byproduct of coking production, mainly used as fuel in sintering production, replacing sintered coal. Generally, coking and sintering production are matched to achieve a balance between coke fine production and consumption. However, some companies use green production systems with a high pellet ratio in their blast furnace burden structure, reducing the proportion of sintered ore and resulting in a large surplus of coke fines that needs to be processed. This creates an imbalance between production and consumption, hinders processing channels, and results in unused coke fines that occupy inventory, capital, and the feed mill. Some companies have attempted to directly use coke dust in blast furnace pulverizing systems for injection; however, this has resulted in a significant reduction in coal mill output and severe wear on the injection lances, failing to meet the demands of ironmaking production. There is an urgent need to develop new processing methods. Summary of the Invention

[0003] The embodiments of this application provide a fine grinding method for self-produced coke fines, which can provide a high-quality pulverized coal resource for blast furnace injection systems; and can be applied to industrial production for use in blast furnace injection, effectively solving the problem of imbalance between the production and consumption of the company's self-produced coke fines.

[0004] This application provides a method for fine grinding of self-produced coke powder, including the following steps:

[0005] Step S1: The coke produced by the coking process is screened at least twice to obtain coke fines;

[0006] Step S2: Finely grind the coke powder using a ball mill to obtain coke powder slurry;

[0007] Step S3: The coke powder slurry enters the hydrocyclone for classification, and the overflow of the hydrocyclone is fine-grained slurry;

[0008] Step S4: Concentrate and filter the fine-grained slurry to produce coke powder.

[0009] In some embodiments of this application, based on the aforementioned scheme, in step S1, the coke produced by the coking process is screened twice, specifically including: the coke produced by the coking process is first screened, the coke on the screen is directly supplied to the blast furnace, and the coke under the screen is dropped to the material yard. Then the coke in the material yard is screened a second time, the coke on the screen is sold externally or used internally, and the coke under the screen is obtained as coke dust.

[0010] In some embodiments of this application, based on the aforementioned scheme, in step S1, both the first screening and the second screening use bar screens. The bar screen used for the first screening has an aperture of 24-26 mm, and the bar screen used for the second screening has an aperture of 7-10 mm.

[0011] In some embodiments of this application, based on the aforementioned scheme, the particle size of the coke is less than 10 mm.

[0012] In some embodiments of this application, based on the foregoing scheme, in step S2, the ball mill is an overflow ball mill, the diameter of the ball mill is greater than or equal to 3.6m, the rotation speed is greater than 19r / min, the cascade angle is greater than 60°, the grinding media of the ball mill is steel balls, the filling rate of the steel balls is greater than 40%, the diameter is 120-130mm, and the total mass of all the filled steel balls is greater than 120t;

[0013] The ball mill has a length of 7.2m or more and a volume concentration of 80% or more. The flow velocity of the coke slurry in the ball mill cylinder is less than 0.035m / s and the grinding time is greater than 3.5min.

[0014] In some embodiments of this application, based on the aforementioned scheme, in step S3, the hydrocyclone is a hydraulic hydrocyclone, the model of the hydrocyclone is FX500-GT-Y, the overflow pipe length is 400-500mm, the overflow pipe diameter is greater than 190mm, the sedimentation port diameter is less than 70mm, the underflow volume concentration is greater than 70%, and the operating pressure is 40-45kPa.

[0015] In some embodiments of this application, based on the foregoing scheme, step S3 further includes: the underflow of the hydrocyclone is returned to the ball mill in step S2.

[0016] In some embodiments of this application, based on the aforementioned scheme, step S4 specifically includes: using a composite cone small-diameter hydrocyclone and a deep cone thickener to concentrate the fine-grained slurry, and then filtering it through a vacuum filter to produce coke fine powder;

[0017] The diameter of the composite cone-shaped cyclone separator is less than 200 mm; the settling section of the deep cone-shaped thickener is greater than 3.5 m, and the volume concentration of the settling underflow is greater than 65%.

[0018] In some embodiments of this application, based on the aforementioned scheme, in step S4, the proportion of the amount of coke fine powder with a particle size of less than 0.25 mm to the total amount is greater than 70%, and the moisture content of the coke fine powder is less than 25%.

[0019] In some embodiments of this application, based on the aforementioned scheme, the coke fine powder produced in step S4 is mixed with bituminous coal and anthracite and then fed into a blast furnace coal mill. After being finely ground until the proportion of the mixture with a particle size less than 0.074 mm is greater than 95%, it is injected into the blast furnace for combustion.

[0020] Compared to traditional iron ore, self-produced coke fines are hard, brittle, and light, causing them to "float" during fine grinding in ball mills, resulting in low grinding efficiency. Furthermore, the small density difference between coke fines and water leads to a close separation interface and poor separation effect. Additionally, the finely ground coke fines exhibit strong hydrophilicity and poor hydrophobicity, causing problems such as high moisture content, filter cloth adhesion, and unloading issues during filtration. To address these issues, this application provides a novel method for finely grinding self-produced coke fines, comprising the following steps: Step S1, coke produced from the coking process is screened at least twice to obtain coke fines; Step S2, the coke fines are finely ground using a ball mill to obtain a coke fines slurry; Step S3, the coke fines slurry is entered into a hydrocyclone for classification, with the overflow from the hydrocyclone being a fine-grained slurry; Step S4, the fine-grained slurry is concentrated and filtered to produce fine coke fines. This method can develop a high-quality pulverized coal resource for blast furnace injection systems and can be applied to industrial production, solving the problem of unbalanced production and consumption of self-produced coke fines in steel companies. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0022] Figure 1 A flowchart of a fine grinding method for self-produced coke powder according to an embodiment of this application is shown;

[0023] Figure 2 A schematic diagram of the fine grinding method for self-produced coke powder according to an embodiment of this application is shown. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] The following detailed description of some embodiments of this application will be provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0026] See Figure 1 and Figure 2 This application provides a method for fine grinding of self-produced coke powder, comprising the following steps:

[0027] Step S1: The coke produced by the coking process is screened at least twice to obtain coke fines;

[0028] Step S2: Finely grind the coke powder using a ball mill to obtain coke powder slurry;

[0029] Step S3: The coke powder slurry enters the hydrocyclone for classification, and the overflow of the hydrocyclone is fine-grained slurry;

[0030] Step S4: Concentrate and filter the fine-grained slurry to produce coke powder.

[0031] In some embodiments of this application, taking into account cost requirements, in step S1, the coke produced by the coking process is screened twice. Specifically, the coke produced by the coking process is first screened, the coke on the screen is directly supplied to the blast furnace, and the coke under the screen (referred to as self-produced coke dust) falls to the material yard. Then, the coke in the material yard is screened a second time, the coke on the screen is sold externally or used internally, and the coke under the screen is obtained as coke dust.

[0032] It should be noted that because the Hardgrove Grindability Index (HGI) of the self-produced coke is less than 35 (belonging to the category of difficult-to-grind coal), the coke must undergo at least two screenings in step S1 to ensure that the particle size of the coke that is finally screened out is basically less than 10mm, so that it can meet the standard of being directly fed into the ball mill for fine grinding.

[0033] Specifically, in step S1, both the first and second screenings use bar screens. The aperture (distance between bars) of the bar screen used in the first screening is 24-26 mm, and the aperture of the bar screen used in the second screening is 7-10 mm.

[0034] In some embodiments of this application, the coke powder can be transported to a ball mill for fine grinding via a feeding system such as a belt or hopper.

[0035] Specifically, in step S2, the ball mill is an overflow ball mill with a diameter greater than or equal to 3.6m, a rotational speed greater than 19r / min, and a cascade angle greater than 60°. The grinding media of the ball mill is steel balls with a filling rate greater than 40%, a diameter of 120-130mm, and a total mass of all filled steel balls greater than 120t.

[0036] The ball mill has a length of 7.2m or more and a volume concentration of 80% or more. The flow velocity of the coke slurry in the ball mill cylinder is less than 0.035m / s and the grinding time is greater than 3.5min.

[0037] It should be noted that, compared to traditional iron ore, coke fines are harder, more brittle, and lighter. During fine grinding in a ball mill, they will inevitably "float" and fail to make proper contact with the grinding media (steel balls), significantly reducing grinding efficiency. For overflow ball mills, larger diameters and higher rotational speeds result in larger cascade angles and longer paths for the steel balls, leading to greater impact on the material. Therefore, in step S2, the ball mill is an overflow type with a diameter greater than or equal to 3.6 m, a rotational speed greater than 19 r / min, and a cascade angle greater than 60°. Furthermore, the more steel balls added to the ball mill, and the larger their diameter and weight, the greater the impact potential energy the material receives, which is more conducive to grinding large-particle materials. Therefore, the steel ball filling rate is greater than 40%, the diameter is 120–130 mm, and the total mass of all filled steel balls is greater than 120 t. In addition, to ensure that the flow velocity of coke slurry in the ball mill cylinder is less than 0.035 m / s and the grinding time is greater than 3.5 min, the length of the ball mill is greater than or equal to 7.2 m and the volume concentration is greater than 80%, thereby improving the fine grinding effect.

[0038] It should also be noted that the bulk density of coke slurry is 0.7 t / m³. 3 The true density is 1.6 t / m³. 3 Unlike iron ore, which has a significant density difference with water, coke ore fines undergo coarse and fine classification using hydrocyclones. This results in a close separation interface between the coke ore fines slurry and water, leading to poor separation and severe overflow of coarse material. Therefore, in step S3, by plotting the movement trajectory of the coke ore fines slurry in the hydrocyclone classification, measures are taken to "reduce the diameter of the settling inlet and increase the diameter of the overflow pipe." Specifically, the hydrocyclone used is a hydrocyclone of model FX500-GT-Y, with an overflow pipe length of 400-500 mm, an overflow pipe diameter greater than 190 mm, a settling inlet diameter less than 70 mm, an underflow volume concentration greater than 70%, and an operating pressure of 40-45 kPa.

[0039] In some embodiments of this application, step S3 further includes: the underflow from the hydrocyclone is returned to the ball mill in step S2. That is, the underflow from the hydrocyclone is returned to the ball mill for re-grinding, i.e., the underflow from the hydrocyclone and the ball mill form a closed loop, while the fine-grained slurry overflowing from the hydrocyclone enters the subsequent concentration and filtration steps.

[0040] Step S4 specifically includes: concentrating the fine-grained slurry using a combination of a small-diameter composite cone hydrocyclone and a deep cone thickener, followed by filtration through a vacuum filter to produce fine coke powder. This combined concentration method results in high concentration efficiency.

[0041] Specifically, the diameter of the composite cone-shaped hydrocyclone is less than 200 mm; the settling section of the deep cone-shaped thickener is greater than 3.5 m; the main rake drive can automatically raise and lower the main rake according to the pressure, reducing pressure-induced shutdowns; and a high-molecular-weight flocculant can be added to the deep cone-shaped thickener to improve concentration efficiency, with a volume concentration of the settling underflow greater than 65%. In some embodiments of this application, the overflow of the deep cone-shaped thickener and the filtrate of the vacuum filter can be recycled, for example, by pumping them back to a ball mill or hydrocyclone for reuse.

[0042] Specifically, in step S4, the proportion of the produced coke fine powder with a particle size of less than 0.25 mm is greater than 70% of the total, and the moisture content of the produced coke fine powder is less than 25%.

[0043] In some embodiments of this application, the coke powder produced in step S4 is mixed with bituminous coal and anthracite and then fed into a blast furnace coal mill. After being finely ground until the proportion of particles smaller than 0.074 mm in the mixture is greater than 95%, it is injected into the blast furnace for combustion.

[0044] In summary, this application provides a method for fine grinding of self-produced coke fines. Through a series of steps including screening, fine grinding, grading, concentration, and filtration, highly efficient fine grinding of self-produced coke fines can be achieved. The proportion of coke fine powder with a particle size less than 0.25 mm in the total output is greater than 70%. Therefore, the produced coke fine powder can be mixed with bituminous coal and anthracite, finely ground, and injected into the blast furnace for combustion. This provides a high-quality pulverized coal resource for the blast furnace injection system, applicable to industrial production and used for blast furnace injection, effectively solving the problem of imbalance between the production and consumption of self-produced coke fines in steel companies.

[0045] Other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the embodiments disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that this application is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A method for fine grinding of self-produced coke dust, characterized in that, Includes the following steps: Step S1: The coke produced by the coking process is screened at least twice to obtain coke fines; Step S2: Finely grind coke powder using a ball mill to obtain coke powder slurry; wherein the ball mill is an overflow ball mill, the diameter of the ball mill is greater than or equal to 3.6m, the rotation speed is greater than 19r / min, the cascade angle is greater than 60°, the grinding media of the ball mill is steel balls, the filling rate of the steel balls is greater than 40%, the diameter is 120~130mm, and the total mass of all filled steel balls is greater than 120t; the length of the ball mill is greater than or equal to 7.2m, the volume concentration is greater than 80%, the flow velocity of the coke powder slurry in the ball mill cylinder is less than 0.035m / s, and the grinding time is greater than 3.5min; Step S3: The coke slurry enters a hydrocyclone for classification. The overflow of the hydrocyclone is a fine-grained slurry. The hydrocyclone is a hydraulic hydrocyclone with an overflow pipe length of 400-500 mm, an overflow pipe diameter greater than 190 mm, a sand settling port diameter less than 70 mm, an underflow volume concentration greater than 70%, and an operating pressure of 40-45 kPa. Step S4: The fine-grained slurry is concentrated using a combination of a small-diameter composite cone hydrocyclone and a deep cone thickener, and then filtered through a vacuum filter to produce coke fine powder; the diameter of the small-diameter composite cone hydrocyclone is less than 200 mm; the settling section of the deep cone thickener is greater than 3.5 m, and the volume concentration of the underflow is greater than 65%; In step S1, the coke produced by the coking process undergoes two screenings. Specifically, the coke produced by the coking process undergoes a first screening. The coke that passes through the screen is directly supplied to the blast furnace, while the coke that falls through the screen is dropped into the material yard. The coke in the material yard then undergoes a second screening. The coke that passes through the screen is sold externally or used internally, while the coke that falls through the screen is coke dust. Both the first and second screenings use bar screens. The bar screen used for the first screening has an aperture of 24-26 mm, and the bar screen used for the second screening has an aperture of 7-10 mm.

2. The fine grinding method for self-produced coke powder according to claim 1, characterized in that, The particle size of the coke dust is less than 10 mm.

3. The fine grinding method for self-produced coke powder according to claim 1, characterized in that, In step S3, the model of the hydrocyclone is FX500-GT-Y.

4. The fine grinding method for self-produced coke powder according to claim 1, characterized in that, Step S3 further includes: the underflow from the hydrocyclone is returned to the ball mill in step S2.

5. The fine grinding method for self-produced coke powder according to claim 1, characterized in that, In step S4, the proportion of the produced coke fine powder with a particle size of less than 0.25 mm is greater than 70% of the total, and the moisture content of the produced coke fine powder is less than 25%.

6. The fine grinding method for self-produced coke powder according to claim 1, characterized in that, The coke powder produced in step S4 is mixed with bituminous coal and anthracite and then fed into a blast furnace coal mill. After being finely ground until the proportion of particles smaller than 0.074 mm in the mixture is greater than 95%, it is injected into the blast furnace for combustion.

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