Coal for blast furnace injection and preparation method thereof

Abstract

The invention belongs to the field of coal, and particularly discloses coal for blast furnace injection and a preparation method thereof. According to the method, the coal for blast furnace injection is obtained by firstly dressing the coal, then dressing the ore and finally blending the coal and the ore, so that the coal for blast furnace injection is produced by adopting the low-rank coal, the content of CaO beneficial minerals in the coal for blast furnace injection is increased, the requirements of an actual blast furnace injection process are met, and the emission of gangue resources is remarkably reduced; the gangue retreatment cost is reduced; and the environmental pressure is reduced.

Description

Technical Field

[0001] This invention belongs to the field of coal, specifically relating to a type of blast furnace injection coal and its preparation method. Background Technology

[0002] Pulverized coal injection in blast furnaces plays an increasingly important role in the iron and steel smelting process. For example, pulverized coal injection in blast furnaces generally includes the following functions: (1) partially replacing metallurgical coke with pulverized coal, thereby reducing the coke ratio in blast furnace ironmaking and lowering the cost of pig iron; (2) adjusting the furnace thermal regime and stabilizing operation; (3) the pulverized coal injected is gasified and burned in front of the blast furnace tuyeres to reduce the theoretical combustion degree, while creating conditions for the use of high-temperature blast and oxygen-enriched blast in the blast furnace. The clean coal separated by low-rank coal preparation plants is conventionally used as pulverized coal for blast furnace injection, but during the separation process, useful minerals beneficial to the blast furnace injection process are lost with gangue. The calcium element in the raw coal has a positive impact on the viscosity improvement of blast furnace slag, the permeability of the feed column, and the desulfurization capacity of the slag. At the same time, with the increase of calcium oxide, the combustion curve tends to shift to the left, indicating that the addition of calcium has a certain catalytic effect on the combustion of pulverized coal. Catalytic combustion can significantly reduce the amount of unburned pulverized coal in the furnace and help to increase the theoretical combustion temperature, saving blast furnace smelting agent. Summary of the Invention

[0003] In view of the problem of loss of useful minerals in the conventional coal preparation process for producing blast furnace injection coal mentioned above, the present invention will provide blast furnace injection coal and its preparation method.

[0004] To achieve the above objectives, the following technical solutions are specifically included: On one hand, the present invention provides a method for preparing blast furnace pulverized coal, comprising the following steps: S1. Low-rank coal and media are separated by a shallow trough to obtain clean coal and gangue 1; S2. The gangue 1 is fed into a desliming screen for desliming to obtain the upper screen material, the lower screen material and the lower screen slurry. S3. The material on the upper screen is crushed, and then the crushed material on the upper screen, the material on the lower screen, and water are put into a hydrocyclone for separation to obtain gangue 2 and gangue 3. S4. The gangue 2 is fed into the desliming screen for desliming to obtain the material on the desliming screen of gangue 2 and the material under the desliming screen of gangue 2. S5. Dehydrate the material on the dewatering screen of the gangue 2, and then mix it with the clean coal to obtain blast furnace injection coal.

[0005] In the method of this invention, low-rank coal is first subjected to shallow trough separation (i.e., coal preparation) to obtain clean coal and gangue. The gangue is then subjected to desliming, crushing, hydrocyclone separation, further desliming, and dewatering to obtain processed gangue material (mineral processing). This processed gangue is then blended with the clean coal to obtain blast furnace injection coal. The further processing of the gangue after shallow trough separation prevents the loss of valuable minerals and reduces the amount of gangue discharged, allowing for the recovery of beneficial inorganic minerals such as CaO from the gangue. The clean coal after shallow trough separation is rich in organic minerals. Blending the clean coal rich in organic minerals with the gangue rich in inorganic minerals improves the quality of the original low-rank coal, particularly increasing its CaO content. This not only enhances the adaptability of low-rank coal for blast furnace injection and increases product value but also helps reduce gangue emissions, providing a new approach to expanding the uses of thermal coal. Therefore, the present invention adopts a method of first beneficiating coal and then beneficiating ore, and finally blending coal and ore to obtain blast furnace injection coal. This method not only produces blast furnace injection coal using low-rank coal and increases the content of beneficial minerals such as CaO in the blast furnace injection coal to meet the requirements of actual blast furnace injection process, but also significantly reduces the emission of gangue resources.

[0006] Preferably, in step S1, the CaO mass percentage content in the low-rank coal ash component is greater than 12%, more preferably greater than or equal to 15%, and even more preferably 15-20%.

[0007] Preferably, in step S1, the low-rank coal includes at least one of weakly caking coal, non-caking coal, long-flame coal, or lignite. GB / T18512-2008, "Technical Conditions for Coal Used in Blast Furnace Injection," specifies that the coal categories for blast furnace injection are anthracite, lean coal, semi-lean coal, gas coal, long-flame coal, non-caking coal, and weakly caking coal. Among these, anthracite, lean coal, and semi-lean coal are high-rank coals, while gas coal, long-flame coal, non-caking coal, and weakly caking coal are low-rank coals. Therefore, blast furnace injection coal can be simply divided into high-rank coal and low-rank coal. This invention uses low-rank coals such as weakly caking coal, non-caking coal, long-flame coal, or lignite as raw coal to produce high-Ca content blast furnace injection coal, making it more suitable for blast furnace injection processes.

[0008] Preferably, in step S1, the medium comprises a suspension of magnetite powder and water; the sorting density of the shallow tank sorting is 1-2 kg / L.

[0009] Preferably, in step S2, the desliming screen is a double-layer linear desliming screen, wherein the upper screen aperture is 2-4 mm and the lower screen aperture is 0.5-1.5 mm. The purpose of using a double-layer linear desliming screen with two screening layers is that the lower screen with a smaller aperture can recover heavy media, while the upper screen with a larger aperture can recover large-sized gangue, which needs to be further crushed to further liberate different minerals in the gangue, facilitating subsequent sorting.

[0010] Preferably, step S2 further includes the following step: pumping the lower layer undersize slurry into the hydrocyclone backflushing port.

[0011] Preferably, in step S3, the hydrocyclone is a water-medium hydrocyclone, which includes a cylindrical section and a conical section, the conical section having an obtuse angle, and a tangential backflushing port is provided at the junction of the cylindrical section and the conical section. This configuration enables the water-medium hydrocyclone to achieve the effect of backflushing water, improving the sorting efficiency and accuracy.

[0012] Preferably, in step S3, the crushing equipment includes a hammer crusher, and the particle size of the crushed material on the upper screen is less than or equal to 25 mm. More preferably, the particle size of the crushed material on the upper screen is less than 13-25 mm.

[0013] Preferably, in step S3, the sorting density is 2-3 kg / L.

[0014] Preferably, in step S4, the desliming screen is a linear desliming screen with an aperture of 0.5-1 mm.

[0015] Preferably, the method further includes the following step S6: the undersize materials of the gangue 3 and the gangue 2 are sequentially mixed and magnetically separated to obtain concentrate and tailings; the concentrate is used as the medium in shallow trough separation, and the tailings enter the coal slurry water treatment stage.

[0016] On the other hand, the present invention provides a blast furnace injection coal, which is prepared by the method for preparing blast furnace injection coal, wherein the mass percentage of CaO in the ash component of the blast furnace injection coal is greater than 20%.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention adopts a method of first beneficiating coal and then beneficiating ore, and finally blending coal and ore to obtain blast furnace injection coal. This method not only uses low-rank coal to produce blast furnace injection coal and increases the content of beneficial minerals such as CaO in the blast furnace injection coal to meet the requirements of actual blast furnace injection process, but also significantly reduces the emission of gangue resources, reduces the cost of gangue reprocessing, and reduces environmental pressure. Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation method in Embodiment 1 of the present invention; wherein, A-shallow trough separator, B-double-layer linear desliming screen, C-crusher, D-feeding bucket 1, E-pump, F-feeding bucket 2, G-pump, H-(backwash water medium) hydrocyclone, I-linear desliming screen, J-magnetic separator, K-centrifuge.

[0019] Figure 2 This is the process flow diagram for Comparative Example 1. Detailed Implementation

[0020] To better illustrate the purpose, technical solution, and advantages of this invention, specific embodiments will be used to further explain the invention below. Unless otherwise specified, the test methods used in the embodiments and / or comparative examples are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0021] Example 1 A method for preparing blast furnace injection coal includes the following steps: S1. The existing raw coal (weakly caking coal) and qualified medium (suspension of magnetite powder and water) are fed into the shallow trough separator A to separate clean coal and gangue 1, with an average separation density of 1.5 kg / L. S2. Gangue 1 enters the double-layer linear desliming screen B, where the upper screen aperture is 3mm and the lower screen aperture is 1mm. The deslimed gangue 1 is divided into upper screen oversize material, lower screen oversize material and undersize slurry. The undersize slurry is fed into the feed tank F, and the material in the feed tank F is pumped to the backwash port of the backwash hydrocyclone H. S3. The material on the upper screen enters the crusher C. The crushed material is then combined with the material on the lower screen and the circulating water and fed into the feed hopper D. The material in the feed hopper D is sent to the feed port of the backwash hydrocyclone H by the pump E, and gangue 2 and gangue 3 are separated. The average density of the separated gangue is 2.3 kg / L. S4. Gangue 2 enters the linear desliming screen I and is separated into oversize material and undersize material. The screen aperture of the linear desliming screen I is 0.8mm. The undersize material of gangue 2 is mostly medium, which is mainly magnetite powder with an average diameter of 0.075mm. The desliming screening method can achieve the separation of medium and sorted material. The material on the dewatering screen of S5 and gangue 2 enters centrifuge K for dewatering and is then combined with clean coal to become blast furnace injection coal; S6. The undersize material from the desliming screen of gangue 2 and gangue 3 are combined and fed into magnetic separator J to separate into concentrate and tailings. The magnetic field strength of the magnetic separator is 1000-1500GS. Both the undersize material from the desliming screen of gangue 2 and the material from gangue 3 contain magnetite powder, which is then combined and recovered. The concentrate from the magnetic separator is returned to the qualified medium, and the tailings from the magnetic separator enter the coal slurry water treatment stage.

[0022] Test method: The testing methods for ash content, CaO content, CaO distribution rate, and yield in raw coal, clean coal, and gangue are as follows: Following GB / T 1574-2007, the method for analyzing coal ash composition, wherein the CaO distribution rate in this invention is the ratio of the CaO content in the product to the CaO content in the raw coal; the ash content of coal is calculated on a dry basis, and the ash content consists of chemical components such as CaO, SiO2, and Al2O3; the CaO content in coal ash refers to the CaO content calculated with the ash content of coal as 100%.

[0023] The test results are shown in Table 1.

[0024] Table 1

[0025] Comparative Example 1 A method for preparing blast furnace injection coal includes the following steps: The on-site production process employs shallow heavy media separation of lump coal (raw coal), with clean coal as the product and gangue disposal as the output. A schematic diagram of the process is shown below. Figure 2 As shown; specifically, it includes the following steps: Raw coal and qualified medium (same as in Example 1) are fed into a heavy medium shallow trough separator to separate clean coal and gangue, with the separation density concentrated at 1.5 kg / cm³. 3 The clean coal enters the desliming screen and is separated into oversize and undersize slurry. The oversize is further dewatered by a centrifuge to become clean coal product. The undersize slurry is divided into a qualified medium section and a dilute medium section. The qualified medium is returned to the shallow trough separator, while the dilute medium is fed into a magnetic separator to be separated into qualified medium and magnetic tailings. The qualified medium is returned to the shallow trough separator, while the magnetic tailings enter the coal slurry water treatment stage. The gangue after shallow trough separation is processed in a similar manner to clean coal, except that the oversize material from the gangue desliming screen does not enter the centrifuge and becomes the product directly.

[0026] In this comparative example, the ash content, CaO content in coal ash, and CaO distribution rate were tested in the same way as in Example 1, and the test results are shown in Table 2.

[0027] Table 2

[0028] As shown in Table 2 of Comparative Example 1, the CaO content in the ash of the existing clean coal is only 18.21%, which is difficult to meet the requirements for blast furnace injection coal (>20%). Moreover, most of the CaO is lost in the gangue products. Further processing of the clean coal is required to produce qualified blast furnace injection coal. A large amount of gangue also needs to be further discharged and treated, which increases the production cost.

[0029] As shown in Table 1 of Example 1, the method of this invention, during the production of clean coal from low-rank coal, simultaneously processes the gangue. After passing the processing, the gangue is blended with the clean coal, directly obtaining a coal product that meets the requirements for blast furnace injection. This method can increase the CaO content in the product's coal ash to over 20% and the CaO distribution rate to 91.57%, essentially recovering CaO from the raw coal into the clean coal. This not only meets the requirements of blast furnace injection users for ash content and CaO content in clean coal, increasing its value, but also reduces gangue emissions and improves gangue utilization. The clean coal produced from low-rank coal by this invention directly meets the requirements of a certain thermal coal preparation plant in western China for blast furnace injection coal with an ash content of <8.5wt% and CaO content >20wt%, eliminating the need for additional post-processing and meeting actual market demand. This approach helps reduce production costs and enhances the application value of clean coal. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing pulverized coal for blast furnace injection, characterized in that, Includes the following steps: S1. Low-rank coal and media are separated by a shallow trough to obtain clean coal and gangue 1; S2. The gangue 1 is fed into a desliming screen for desliming to obtain the upper screen material, the lower screen material and the lower screen slurry. S3. The material on the upper screen is crushed, and then the crushed material on the upper screen, the material on the lower screen, and water are put into a hydrocyclone for separation to obtain gangue 2 and gangue 3. S4. The gangue 2 is fed into the desliming screen for desliming to obtain the material on the desliming screen of gangue 2 and the material under the desliming screen of gangue 2. S5. Dehydrate the material on the dewatering screen of the gangue 2, and then mix it with the clean coal to obtain blast furnace injection coal.

2. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S1, the mass percentage of CaO in the low-rank coal ash component is greater than 12%.

3. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S1, the low-rank coal includes at least one of weakly caking coal, non-caking coal, long-flame coal, or lignite.

4. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, The desliming screen mentioned in step S2 is a double-layer linear desliming screen, wherein the upper layer screening aperture is 2-4mm and the lower layer screening aperture is 0.5-1.5mm.

5. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S3, the hydrocyclone is a water medium hydrocyclone, which includes a cylindrical section and a conical section. The cone angle of the conical section is obtuse, and a tangential backflush port is provided at the junction of the cylindrical section and the conical section.

6. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S3, the crushing equipment includes a hammer crusher, and the particle size of the material on the upper screen after crushing is less than or equal to 25 mm.

7. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S4, the desliming screen is a linear desliming screen with an aperture of 0.5-1mm.

8. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, The method also includes the following step S6: the undersize materials of the gangue 3 and the gangue 2 are sequentially mixed and magnetically separated to obtain concentrate and tailings; the concentrate is used as the medium in shallow trough separation, and the tailings enter the coal slurry water treatment stage.

9. The method for preparing blast furnace pulverized coal as described in claim 1, characterized in that, In step S1, the medium comprises a suspension of magnetite powder and water; the sorting density of the shallow tank sorting is 1-2 kg / L. And / or, in step S3, the sorting density is 2-3 kg / L.

10. A type of pulverized coal for blast furnace injection, characterized in that, The blast furnace injection coal is prepared by the method for preparing blast furnace injection coal according to any one of claims 1-9, wherein the mass percentage of CaO in the ash component of the blast furnace injection coal is greater than 20%.

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