Method for utilizing fly ash

Abstract

The present application belongs to the field of titanium extraction from blast furnace slag, and particularly relates to a method for utilizing dust removal ash, which comprises the following steps: taking a certain amount of dust removal ash generated by carbon thermal reduction smelting of titanium-containing blast furnace slag, and preparing the dust removal ash into slurry; and applying the slurry on a graphite electrode as a protective coating. The present application utilizes the characteristics that the oxidation reaction activity of part of components in the dust removal ash is prior to that of the graphite electrode, and delays the oxidation corrosion of oxygen to the graphite electrode. The present application further utilizes the reduction reaction of part of components in the dust removal ash with the surface of the graphite electrode to generate a carbide protective layer to isolate the graphite electrode from the molten slag and air corrosion. In addition, the dust removal ash can also inhibit the oxidation rate of the graphite electrode by cooling the high-temperature graphite electrode. The present application can effectively slow down the consumption speed of the graphite electrode caused by oxygen corrosion, prolong the service life of the graphite electrode, and reduce the production cost of the electric furnace. At the same time, since the dust removal ash of the electric furnace, a solid waste, is used as the electrode coating material, the waste recycling is realized.

Description

Technical Field

[0001] This invention belongs to the field of titanium extraction from blast furnace slag, and particularly relates to a method for utilizing dust. Background Technology

[0002] Graphite electrodes, characterized by high conductivity and excellent corrosion resistance, are widely used in electric furnace smelting. However, their service life is reduced due to erosion by metallurgical slag, oxidation, and physical wear. Currently, common methods for protecting graphite electrodes include electrode coatings, impregnation layer protection, and smelting atmosphere control. Electrode coating technology, in particular, has a wide range of applications, but its high cost makes the development of low-cost electrode coatings a pressing issue.

[0003] Therefore, existing technologies still need improvement. Summary of the Invention

[0004] To address the challenges of developing and utilizing low-cost electrode coatings, this invention provides a method for utilizing dust collector ash. The method utilizes the characteristic that some components in the dust collector ash exhibit preferential oxidation reactivity compared to the graphite electrode, thus delaying the oxidative erosion of the graphite electrode by oxygen. Furthermore, the method further utilizes the reduction reaction between some components in the dust collector ash and the graphite electrode surface to generate a carbide protective layer, thereby isolating the graphite electrode from slag and air erosion.

[0005] Specifically, an embodiment of the present invention provides a method for utilizing dust, which includes the following steps: S10. Taking a certain amount of dust generated from the carbothermic reduction smelting of titanium-containing blast furnace slag and preparing the dust into a slurry; and S20. Applying the slurry onto a graphite electrode as a protective coating.

[0006] In an embodiment of the present invention, the dust comprises the following components by mass percentage: TiO2: 1.5-3.5%; fixed carbon: 15-45%; TFe: 2-3.5%; TiC: 1-1.5%; the remainder being calcium magnesium aluminum silicon oxide.

[0007] In an embodiment of the present invention, step S10 includes: preparing the dust ash into a first slurry, and step S20 includes pre-spraying the first slurry onto a cold graphite electrode as a protective coating.

[0008] In an embodiment of the present invention, the first slurry is a mixture of dust and water, and the moisture content of the first slurry is 7-9%.

[0009] In an embodiment of the present invention, step S10 includes: preparing the dust ash into a second slurry, and step S20 includes thermally spraying the second slurry onto a hot graphite electrode as a protective coating.

[0010] In an embodiment of the present invention, the second slurry is a mixture of the dust and water, and the moisture content of the second slurry is 3-5%.

[0011] In an embodiment of the present invention, in step S10, the mass percentage content of TiO2 in the titanium-containing blast furnace slag is ≥15%, and the total amount of the titanium-containing blast furnace slag in the dust removal station is 1 to 2%, and the particle size range of the dust removal ash is ≤450 mesh.

[0012] In an embodiment of the present invention, the method for utilizing the dust ash further includes the following steps: S30. Under high temperature conditions, the protective coating is used to consume oxygen in order to delay the oxidative erosion of the graphite electrode by oxygen; and S40. Under high temperature conditions, the protective coating is used to generate a carbide protective layer to isolate the graphite electrode from the erosion of molten slag and air.

[0013] In an embodiment of the present invention, in step S30, oxygen is consumed by the following oxidation reaction of fixed carbon and TFe in the dust:

[0014] 2C+O2=2CO, 3Fe+2O2=Fe3O4.

[0015] In an embodiment of the present invention, in step S40, the carbide protective layer comprises TiO2 and calcium magnesium aluminum silicon oxide in the dust, which are generated by the reduction reaction with the surface of the graphite electrode to form TiC and SiC.

[0016] This invention provides a low-cost method for developing graphite electrode coatings. The method described in this invention effectively slows down the rate at which graphite electrodes are eroded and consumed by oxygen, thereby extending the lifespan of the graphite electrodes and reducing the production cost of electric furnaces. Furthermore, by using electric furnace dust, a solid waste material, as the electrode coating material, waste recycling is achieved. Attached Figure Description

[0017] Figure 1 A schematic flowchart of a method for utilizing dust provided by the present invention is shown. Detailed Implementation

[0018] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0019] According to the present invention, a method for utilizing dust is provided, such as... Figure 1 As shown, it includes the following steps:

[0020] S10. Take a certain amount of dust generated from the carbothermic reduction smelting of titanium-containing blast furnace slag, and prepare the dust into a slurry; and

[0021] S20. The slurry is applied to the graphite electrode as a protective coating.

[0022] This invention utilizes the characteristic that some components in the dust collector have preferential oxidation reactivity compared to the graphite electrode, thus delaying the oxidative erosion of the graphite electrode by oxygen. Furthermore, this invention utilizes the reduction reaction between some components in the dust collector and the surface of the graphite electrode to generate a carbide protective layer, thereby isolating the graphite electrode from slag and air erosion, as detailed below.

[0023] In embodiments of the present invention, when titanium-containing blast furnace slag (TiO2 content ≥ 15%) is subjected to carbothermic reduction smelting, a large amount of dust (1-2% of the total titanium-containing blast furnace slag) is generated. This dust has a particle size range of ≤ 450 mesh and comprises the following components by mass percentage: TiO2: 1.5-3.5%; fixed carbon: 15-45%; TFe: 2-3.5%; TiC: 1-1.5%; the remainder being calcium, magnesium, aluminum, and silicon oxides. The dust can be prepared into a slurry and pre-sprayed onto a cold graphite electrode or thermally sprayed onto a hot graphite electrode as a protective coating.

[0024] In an embodiment of the present invention, step S10 includes: preparing the dust ash into a first slurry, and step S20 includes pre-spraying the first slurry onto a cold graphite electrode as a protective coating. Before the graphite electrode is put into use, the first slurry can be directly pre-sprayed onto the cold graphite electrode to provide pre-protection.

[0025] In an embodiment of the present invention, the first slurry is a mixture of dust and water, and the moisture content of the first slurry is 7-9%.

[0026] In an embodiment of the present invention, step S10 includes: preparing a second slurry from dust removal ash, and step S20 includes thermally spraying the second slurry onto a hot graphite electrode as a protective coating. After a period of use, the graphite electrode may require repair. In this case, the second slurry prepared from dust removal ash is thermally sprayed onto the hot graphite electrode to provide additional protection. During the thermal spraying operation, the dust removal ash cools the high-temperature graphite electrode, inhibiting the oxidation reaction rate of the graphite electrode at high temperatures.

[0027] In an embodiment of the present invention, the second slurry is a mixture of dust and water, and the moisture content of the second slurry is 3-5%.

[0028] In embodiments of the present invention, further reference is made to Figure 1 The method for utilizing dust ash described in this invention further includes the following steps:

[0029] S30. Under high-temperature conditions, the protective coating consumes oxygen to delay the oxidative corrosion of the graphite electrode by oxygen; and

[0030] S40. Under high temperature conditions, a carbide protective layer is generated using the protective coating to isolate the graphite electrode from slag and air corrosion.

[0031] In an embodiment of the present invention, in step S30, oxygen is consumed by the following oxidation reaction of fixed carbon and TFe in the dust:

[0032] 2C+O2=2CO, 3Fe+2O2=Fe3O4.

[0033] In an embodiment of the present invention, in step S40, the carbide protective layer includes TiO2 in the dust, TiC and SiC generated by the reduction reaction of calcium magnesium aluminum silicon oxide with the surface of the graphite electrode.

[0034] Under high-temperature conditions, such as when graphite electrodes are used in titanium extraction from blast furnace slag, the metallurgical slag will erode, oxidize, and physically degrade them. However, the graphite electrode treated by the method described in this invention has a protective coating. This coating not only slows down the oxidative erosion by oxygen but also generates a carbide protective layer, isolating it from the erosion by the metallurgical slag and air. The protective mechanism of this invention is as follows: the fixed carbon particles in the dust are extremely small and have extremely high reactivity, with oxidation reactions occurring preferentially over the graphite electrode; TFe in the dust acts as a reducing agent, and its oxidation reaction activity is also preferential over the graphite electrode; TiO2 and calcium magnesium aluminum silicon oxides in the dust will undergo reduction reactions with the graphite electrode surface under high-temperature conditions to generate a carbide protective layer such as TiC and SiC, isolating the graphite electrode from further erosion by the slag and air.

[0035] The present invention will be illustrated below through specific embodiments:

[0036] Example 1

[0037] The method for utilizing dust ash described in this invention specifically includes the following steps:

[0038] (1) Take 1% of the dust removal ash from titanium-containing blast furnace slag with a TiO2 content ≥15%. The dust removal ash has a particle size range of ≤450 mesh and includes the following components by mass percentage: TiO2: 1.5%; fixed carbon: 45%; TFe: 3.5%; TiC: 1.5%; the remainder being calcium, magnesium, aluminum, and silicon oxides. Mix the dust removal ash with water to obtain a first slurry with a moisture content of 7%.

[0039] (2) Before the graphite electrode is put into use, the first slurry is applied to the graphite electrode as a protective coating. Specifically, the first slurry can be pre-sprayed onto the graphite electrode. At this time, the graphite electrode is a cold electrode, and the pre-sprayed first slurry will provide pre-protection for the graphite electrode.

[0040] (3) The graphite electrode after the first slurry is applied is used in titanium extraction from blast furnace slag. Under high-temperature conditions, the protective coating consumes oxygen to delay the oxidative erosion of the graphite electrode by oxygen. Specifically, oxygen is consumed through the following oxidation reaction of fixed carbon and TFe in the dust:

[0041] 2C+O2=2CO, 3Fe+2O2=Fe3O4.

[0042] (4) In the titanium extraction process from blast furnace slag, a protective coating is used to generate a carbide protective layer under high-temperature conditions to isolate the graphite electrode from slag and air corrosion. The carbide protective layer includes TiO2 and calcium magnesium aluminum silicon oxides in the dust, which react with the surface of the graphite electrode to form TiC and SiC. TiC and SiC isolate the graphite electrode from further corrosion by slag and air.

[0043] The above methods effectively slow down the rate of graphite electrode erosion by oxygen and minimize further erosion by molten slag and air, thus extending the service life of the graphite electrodes and reducing the production cost of the electric furnace. Furthermore, by using electric furnace dust, a solid waste, as the electrode coating material, waste recycling is achieved.

[0044] Example 2

[0045] The method for utilizing dust ash described in this invention specifically includes the following steps:

[0046] (1) Take 2% of the dust removal ash from titanium-containing blast furnace slag with a TiO2 content ≥15%. The dust removal ash has a particle size range of ≤450 mesh and includes the following components by mass percentage: TiO2: 3.5%; fixed carbon: 15%; TFe: 2%; TiC: 1%; the remainder is calcium, magnesium, aluminum, and silicon oxides. Mix the dust removal ash with water to obtain a first slurry with a moisture content of 9%.

[0047] (2) Before the graphite electrode is put into use, the first slurry is applied to the graphite electrode as a protective coating. Specifically, the first slurry can be pre-sprayed onto the graphite electrode. At this time, the graphite electrode is a cold electrode, and the pre-sprayed first slurry will provide pre-protection for the graphite electrode.

[0048] (3) The graphite electrode after the first slurry is applied is used in titanium extraction from blast furnace slag. Under high-temperature conditions, the protective coating consumes oxygen to delay the oxidative erosion of the graphite electrode by oxygen. Specifically, oxygen is consumed through the following oxidation reaction of fixed carbon and TFe in the dust:

[0049] 2C+O2=2CO, 3Fe+2O2=Fe3O4.

[0050] (4) In the titanium extraction process from blast furnace slag, a protective coating is used to generate a carbide protective layer under high-temperature conditions to isolate the graphite electrode from slag and air corrosion. The carbide protective layer includes TiO2 and calcium magnesium aluminum silicon oxides in the dust, which react with the surface of the graphite electrode to form TiC and SiC. TiC and SiC isolate the graphite electrode from further corrosion by slag and air.

[0051] (5) Due to a period of use, the graphite electrode may be corroded to a certain extent. In order to further protect it, the above dust removal ash is mixed with water to obtain a second slurry with a moisture content of 5%.

[0052] (6) The second slurry is applied to the graphite electrode as a protective coating. Specifically, the second slurry can be thermally sprayed onto the graphite electrode. During thermal spraying, the graphite electrode remains at a high temperature, and the thermally sprayed second slurry provides further protection for the graphite electrode. Moreover, during the thermal spraying operation, the dust remover cools the high-temperature graphite electrode, inhibiting the oxidation reaction rate of the graphite electrode at high temperatures.

[0053] (7) After the graphite electrode is thermally sprayed with the second slurry, the graphite electrode is used at high temperature, similar to (3) and (4) above. The specific details will not be repeated.

[0054] This embodiment can achieve similar technical effects as Embodiment 1.

[0055] Example 3

[0056] The method for utilizing dust ash described in this invention specifically includes the following steps:

[0057] (1) Take 1.5% of the dust removal ash from titanium-containing blast furnace slag with a TiO2 content ≥15%. The dust removal ash has a particle size range of ≤450 mesh and includes the following components by mass percentage: TiO2: 2%; fixed carbon: 30%; TFe: 2.5%; TiC: 1.2%; the remainder being calcium, magnesium, aluminum, and silicon oxides. Mix the dust removal ash with water to obtain a first slurry with a moisture content of 8%.

[0058] (2) Before the graphite electrode is put into use, the first slurry is applied to the graphite electrode as a protective coating. Specifically, the first slurry can be pre-sprayed onto the graphite electrode. At this time, the graphite electrode is a cold electrode, and the pre-sprayed first slurry will provide pre-protection for the graphite electrode.

[0059] (3) The graphite electrode after the first slurry is applied is used in titanium extraction from blast furnace slag. Under high-temperature conditions, the protective coating consumes oxygen to delay the oxidative erosion of the graphite electrode by oxygen. Specifically, oxygen is consumed through the following oxidation reaction of fixed carbon and TFe in the dust:

[0060] 2C+O2=2CO, 3Fe+2O2=Fe3O4.

[0061] (4) In the titanium extraction process from blast furnace slag, a protective coating is used to generate a carbide protective layer under high-temperature conditions to isolate the graphite electrode from slag and air corrosion. The carbide protective layer includes TiO2 and calcium magnesium aluminum silicon oxides in the dust, which react with the surface of the graphite electrode to form TiC and SiC. TiC and SiC isolate the graphite electrode from further corrosion by slag and air.

[0062] (5) Due to a period of use, the graphite electrode may be corroded to a certain extent. In order to further protect it, the above dust removal ash is mixed with water to obtain a second slurry with a moisture content of 4%.

[0063] (6) The second slurry is applied to the graphite electrode as a protective coating. Specifically, the second slurry can be thermally sprayed onto the graphite electrode. During thermal spraying, the graphite electrode remains at a high temperature, and the thermally sprayed second slurry provides further protection for the graphite electrode. Moreover, during the thermal spraying operation, the dust remover cools the high-temperature graphite electrode, inhibiting the oxidation reaction rate of the graphite electrode at high temperatures. As an alternative to step (6), the graphite electrode can be pre-coated again with the aforementioned first slurry after the temperature of the used graphite electrode has returned to room temperature, i.e., it becomes a cold graphite electrode.

[0064] (7) After the graphite electrode is thermally sprayed with the second slurry or pre-coated with the first slurry again, the graphite electrode is used at high temperature, similar to (3) and (4) above. The specific details will not be repeated.

[0065] This embodiment can achieve similar technical effects as Embodiment 1.

[0066] To address the challenges in developing and utilizing low-cost electrode coatings in existing technologies, this invention leverages the preferential oxidation reactivity of fixed carbon and TFe in furnace dust compared to that of graphite electrodes, thus slowing down the oxidative erosion of graphite electrodes by oxygen. Furthermore, the TiO2 and calcium magnesium aluminum silicon oxides in the furnace dust undergo a reduction reaction with the graphite electrode surface, generating a protective layer of carbides such as TiC and SiC to isolate the graphite electrode from slag and air erosion. Additionally, the furnace dust cools the high-temperature graphite electrode, further inhibiting its oxidation rate. Therefore, this invention effectively slows down the rate at which graphite electrodes are consumed by oxygen erosion, extending their service life and reducing electric furnace production costs. Simultaneously, by using furnace dust—a solid waste—as the electrode coating material, waste recycling is achieved.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Any modifications or equivalent substitutions made to the present invention without departing from the spirit and scope thereof should be covered within the protection scope of the claims of the present invention.

Claims

1. A method for utilizing fly ash, characterized by, The method comprises the following steps: S10. A certain amount of dust removal ash produced by carbon thermal reduction smelting of titanium-containing blast furnace slag is taken and the dust removal ash is made into a slurry, wherein the mass percentage content of TiO2 in the titanium-containing blast furnace slag is ≥15%, and the dust removal ash accounts for 1-2% of the total amount of the titanium-containing blast furnace slag, the particle size of the dust removal ash is ≤450 mesh, and the dust removal ash comprises the following mass percentage components: TiO2: 1.5-3.5%; Fixed carbon: 15-45%; TFe: 2-3.5%; TiC: 1-1.5%; and the rest is calcium-magnesium-aluminum-silicon oxide, wherein TFe is used as a reducing agent, and the method consumes oxygen by fixed carbon and TFe under high temperature conditions; and S20. The slurry is applied on a graphite electrode as a protective coating.

2. The method for utilizing the fly ash according to claim 1, characterized by, Step S10 comprises: the dust removal ash is made into a first slurry, and step S20 comprises: the first slurry is pre-sprayed on a cold graphite electrode as a protective coating.

3. The method for utilizing the fly ash according to claim 2, characterized by, The first slurry is a mixture of the dust removal ash and water, and the moisture content of the first slurry is 7-9%.

4. The method for utilizing the fly ash according to claim 1, characterized by, Step S10 comprises: the dust removal ash is made into a second slurry, and step S20 comprises: the second slurry is hot-sprayed on a hot graphite electrode as a protective coating.

5. The method for utilizing the fly ash according to claim 4, characterized by, The second slurry is a mixture of the dust removal ash and water, and the moisture content of the second slurry is 3-5%.

6. The method for utilizing the fly ash according to any one of claims 1 to 5, characterized by, Further comprising the following steps: S30. Under high temperature conditions, the protective coating is used to consume oxygen to delay the oxidative corrosion of the graphite electrode by oxygen; And S40. Under high temperature conditions, the protective coating is used to generate a carbide protective layer to isolate the graphite electrode from the corrosion of molten slag and air.

7. The method according to claim 6, wherein In step S30, oxygen is consumed by the following oxidation reactions of fixed carbon and TFe in the dust removal ash: 2C+O2=2CO, 3Fe+2O2=Fe3O4.

8. The method according to claim 6, wherein In step S40, the carbide protective layer comprises TiC and SiC generated by the reduction reaction of TiO2, calcium-magnesium-aluminum-silicon oxide in the dust removal ash and the surface of the graphite electrode.

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