Process for the production of low-iron carbonized slag

Abstract

The application discloses a production method of low-iron carbonized slag, comprising the following steps: S1, flowing molten state titanium-containing blast furnace slag from a slag outlet of a blast furnace into a slag tank, and adding carbonaceous reducing agent into the slag tank after flowing the titanium-containing blast furnace slag into the slag tank; S2, transporting a plurality of slag tanks containing the titanium-containing blast furnace slag and the carbonaceous reducing agent from the slag outlet of the blast furnace to a slag pouring place of a carbonization electric furnace, and keeping the molten slag in the slag tank still during the transportation; S3, pouring a predetermined amount of molten slag in the upper part of the plurality of slag tanks into the carbonization electric furnace, adding the carbonaceous reducing agent into the carbonization electric furnace for smelting, and discharging the slag after the smelting is completed, so that the low-iron carbonized slag with the Fe content less than 1.5wt% is obtained. The application can control the total iron content in the carbonized slag to be less than 1.5wt%, meet the requirement of a subsequent low-temperature chlorination process, and has the advantages of high iron removal efficiency, simple process, low cost and the like.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology via the chloride process, specifically to a method for producing low-iron carbide slag. Background Technology

[0002] The Panzhihua-Xichang region of my country is rich in vanadium-titanium magnetite resources, with proven reserves accounting for over 95% of the national total. Titanium resources amount to 870 million tons, representing 90.54% of my country's and 35.17% of the world's total titanium reserves, respectively. In the blast furnace ironmaking process, approximately half of the titanium from the Panzhihua-Xichang vanadium-titanium magnetite ends up in the blast furnace slag, with a TiO2 content of 20-25 wt%. To comprehensively recover and utilize the titanium resources in the blast furnace slag and turn waste into treasure, Panzhihua Iron and Steel Group (Pangang) has independently developed a titanium extraction process using high-temperature carbonization followed by low-temperature chlorination.

[0003] The main principle of high-temperature carbonization of high-titanium blast furnace slag to prepare carbide slag is as follows: using high-titanium blast furnace slag as raw material, and anthracite, coke, or semi-coke as solid reducing agents, smelting is carried out at a high temperature of 1300–1700℃, and the product is carbide slag. The main smelting reactions are:

[0004] TiO2+2C=TiC+2CO 2TiO2+C=Ti2O3+CO FeO+C=Fe+CO

[0005] During the high-temperature carbonization process, TiO2 transforms into TiC, FeO transforms into metallic Fe, and the remaining phases remain essentially unchanged. Therefore, the carbonized slag produced by the carbonization reaction of titanium-containing blast furnace slag often contains 2–4 wt% metallic iron. This iron enters the downstream process—the low-temperature chlorination process—along with the carbonized slag. The metallic Fe in the carbonized slag further reacts with chlorine gas during the low-temperature chlorination process to form ferric chloride, severely affecting the quality of titanium tetrachloride and the stable operation of the chlorination process. Therefore, the process requires the Fe content in the carbonized slag to be less than 1.5 wt%. Summary of the Invention

[0006] The main objective of this invention is to provide a method for producing low-iron carbide slag, in order to solve the technical problem of how to control the Fe content in the carbide slag to be less than 1.5 wt%.

[0007] According to one aspect of the present invention, a method for producing low-iron carbide slag is provided, comprising the following steps:

[0008] S1, molten titanium-containing blast furnace slag is fed into the slag pot from the blast furnace slag outlet, and carbonaceous reducing agent is added to the slag pot after the titanium-containing blast furnace slag is fed into the slag pot;

[0009] S2, multiple slag pots containing titanium-containing blast furnace slag and carbonaceous reducing agent are transported from the blast furnace slag outlet to the slag dumping point of the carbide electric furnace, and the molten slag in the slag pots is kept stationary during transportation;

[0010] S3. A predetermined amount of molten slag from the upper part of multiple slag pots is poured into a carbide electric furnace, and a carbonaceous reducing agent is added to the carbide electric furnace for smelting. After smelting, the slag is discharged to obtain a low-iron carbide slag with an Fe content of less than 1.5wt%.

[0011] According to one embodiment of the present invention, in step S1, after titanium-containing blast furnace slag flows into the slag pot, a carbonaceous reducing agent is injected into the slag pot to ensure that the titanium-containing blast furnace slag and the carbonaceous reducing agent are fully mixed.

[0012] According to one embodiment of the present invention, in step S1, the temperature of the titanium-containing blast furnace slag flowing into the slag pot is 1350-1500℃.

[0013] According to one embodiment of the present invention, in step S1, the total amount of carbonaceous reducing agent added to the slag pot is 5%-10% of the mass of titanium-containing blast furnace slag added to the slag pot.

[0014] According to one embodiment of the present invention, the particle size of the carbonaceous reducing agent in steps S1 and S3 is between 100 and 300 mesh.

[0015] According to one embodiment of the present invention, the carbonaceous reducing agent in steps S1 and S3 is one or more of coke powder, semi-coke, anthracite, and graphite, wherein the fixed carbon content is ≥80%.

[0016] According to one embodiment of the present invention, in step S3, the predetermined amount is 3 / 4 of the total amount of molten slag in the slag pot.

[0017] According to one embodiment of the present invention, in step S3, the mass of the carbonaceous reducing agent added to the carbonization furnace is 10%-20% of the total weight difference before and after the molten slag is poured into the carbonization furnace from multiple slag pots.

[0018] According to one embodiment of the present invention, in step S3, the smelting time is 90-120 min.

[0019] According to one embodiment of the present invention, in step S3, the molten slag is water-quenched during the slag removal process to obtain water-quenched slag; and the water-quenched slag is dried and ground to obtain the low-iron carbide slag.

[0020] In the technical solution of this invention, molten titanium-containing blast furnace slag flows from the blast furnace slag outlet into the slag pot. The blast furnace slag's own heat and carbonaceous reducing agent undergo a reduction reaction within the slag pot, reducing FeO in the blast furnace slag to metallic Fe. Since metallic Fe has a higher specific gravity than blast furnace slag, the molten slag inside the slag pot remains generally stationary during transport, and metallic Fe deposits at the bottom of the slag pot. When the slag pot reaches the slag dumping point (e.g., the slag turning bridge) of the carbide electric furnace, a predetermined amount of molten slag from the top of the slag pot (this portion of molten slag contains less Fe) is poured into the carbide electric furnace for continued carbide smelting to produce low-iron carbide slag. This yields carbide slag with a total iron content ≤1.5wt%, meeting the requirements of subsequent low-temperature chlorination processes. This method has advantages such as high iron removal efficiency, simple process, and low cost. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0022] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0023] As mentioned in the background section above, the inventors of this application recognize that the carbonized slag produced by the carbonization reaction of titanium-containing blast furnace slag often contains 2-4 wt% metallic iron. This iron, carried along with the carbonized slag into the downstream low-temperature chlorination process, will further react with chlorine gas during the low-temperature chlorination process to form ferric chloride, seriously affecting the quality of titanium tetrachloride and the stable operation of the chlorination process. To solve this technical problem, this application adopts one or more embodiments as described below to reduce the iron content in the carbonized slag to less than 1.5 wt%, ensuring the stable operation of the subsequent low-temperature chlorination process.

[0024] This invention proposes a method for producing low-iron carbide slag, comprising the following steps:

[0025] S1, molten titanium-containing blast furnace slag is fed into the slag pot from the blast furnace slag outlet, and carbonaceous reducing agent is added to the slag pot after the titanium-containing blast furnace slag is fed into the slag pot;

[0026] S2, multiple (e.g., 3 to 4) slag pots containing titanium-containing blast furnace slag and carbonaceous reducing agent are transported from the blast furnace slag outlet (e.g., by smooth rail transport) to the slag dumping point of the carbide electric furnace, during which the molten slag in the slag pots is generally kept still;

[0027] S3, pour a predetermined amount of molten slag from the upper part of multiple slag pots into (e.g., through a chute) a carburizing electric furnace, add a carbonaceous reducing agent into the carburizing electric furnace for smelting, and after smelting, remove the slag to obtain a low-iron carburizing slag with an Fe content of less than 1.5 wt%.

[0028] In an embodiment of the present invention, molten titanium-containing blast furnace slag flows from the blast furnace slag outlet into a slag pot. The blast furnace slag's inherent heat reacts with a carbonaceous reducing agent within the slag pot, reducing FeO in the blast furnace slag to metallic Fe. Since metallic Fe has a higher specific gravity than blast furnace slag, the molten slag in the slag pot remains generally stationary during transport, and metallic Fe deposits at the bottom of the slag pot. When the slag pot reaches the slag dumping point (e.g., the slag turning bridge) of the carbide furnace, a predetermined amount of molten slag from the upper part of the slag pot (this portion of molten slag contains less Fe) is poured into the carbide furnace for continued carbide smelting to produce low-iron carbide slag. This yields carbide slag with a total iron content of less than 1.5 wt%, meeting the requirements of subsequent low-temperature chlorination processes. This method has advantages such as high iron removal efficiency, simple process, and low cost.

[0029] In some embodiments, the titanium-containing blast furnace slag comprises, by weight percentage: 22.66% TiO2, 28.25% CaO, 13.69% Al2O3, 7.15% MgO, 24.80% SiO2, 0.27% V2O5, and 2.03% TFe.

[0030] In some embodiments, in step S1, the temperature of the titanium-containing blast furnace slag flowing into the slag pot is 1350-1500°C, to ensure that the titanium-containing blast furnace slag and the carbonaceous reducing agent can undergo a reduction reaction at this temperature, reducing FeO in the blast furnace slag to metallic Fe.

[0031] In some embodiments, in step S1, after the titanium-containing blast furnace slag flows into the slag pot, a carbonaceous reducing agent is injected into the slag pot to ensure thorough mixing between the titanium-containing blast furnace slag and the carbonaceous reducing agent. By providing the carbonaceous reducing agent from the top and injecting it, it is ensured that the titanium-containing blast furnace slag and the carbonaceous reducing agent are thoroughly mixed and a reduction reaction occurs. An inert gas (e.g., nitrogen) can be used to inject the carbonaceous reducing agent into the molten slag. Adding the carbonaceous reducing agent after adding the titanium-containing blast furnace slag facilitates the calculation of the mass of carbonaceous reducing agent added to the slag pot.

[0032] In some embodiments, in step S1, the total amount of carbonaceous reducing agent added to the slag pot is 5%-10% of the mass of the titanium-containing blast furnace slag added to the slag pot, ensuring that the carbonaceous reducing agent added to the slag pot is sufficient to reduce FeO in the blast furnace slag. The mass of the titanium-containing blast furnace slag added to the slag pot can be obtained by weighing a single empty pot and a full pot after adding the titanium-containing blast furnace slag using a weighing device, and then subtracting the two. The mass of carbonaceous reducing agent added to the slag pot is then determined according to a predetermined dosage ratio.

[0033] In some embodiments, the carbonaceous reducing agent in steps S1 and S3 is in powder form with a particle size between 100 and 300 mesh. Fine-grained carbonaceous reducing agents ensure a more convenient and complete reaction. In some embodiments, the carbonaceous reducing agent in steps S1 and S3 is one or more of coke powder, semi-coke, anthracite, and graphite, wherein the fixed carbon content is ≥80%. Preferably, semi-coke is used as the carbonaceous reducing agent. Semi-coke, also known as semi-coke, is made from high-quality Jurassic coal lumps and has high resistivity, high chemical activity, and low sulfur and phosphorus content. It has significant advantages in electric arc furnace smelting of titanium-containing blast furnace slag, mainly: semi-coke has a higher resistivity than conventional metallurgical coke, which facilitates deeper electrode insertion into the molten blast furnace slag during smelting; semi-coke has better chemical activity than coke powder, which can increase the carbonization reaction rate and improve the smelting level of titanium-containing blast furnace slag. In some embodiments, the semi-coke used has a volatile matter content of 4.61%, a fixed carbon content of 84.35%, and an ash content of 11.04%.

[0034] In some embodiments, in step S3, the predetermined amount is 3 / 4 of the total amount of molten slag in the slag pot, ensuring that the molten slag added to the carburizing furnace has a low Fe content.

[0035] In some embodiments, in step S3, the mass of the carbonaceous reducing agent added to the carbonization furnace is 10%-20% of the total weight difference before and after the molten slag is poured into the carbonization furnace from multiple slag pots, ensuring a sufficient carbonization reaction in the carbonization furnace. The total weight difference before and after the slag is poured from multiple slag pots can be calculated by weighing the weights of the multiple slag pots before and after pouring the slag using a weighing device.

[0036] In some embodiments, in step S3, the smelting time is 90-120 minutes, and the active power of the electric furnace is controlled at, for example, 22 MW during the smelting period.

[0037] In some embodiments, in step S3, the molten slag is water-quenched during the slag removal process (e.g., by directly impacting the molten slag with high-pressure water) to obtain water-quenched slag; and the water-quenched slag is dried and ground (e.g., ground to 100-400 mesh) to obtain the low-iron carbide slag, which is used in downstream processes (e.g., low-temperature chlorination process for the production of titanium tetrachloride).

[0038] In summary, this invention proposes a method for preparing low-iron carbide slag. Molten titanium-containing blast furnace slag flows from the blast furnace slag outlet into a slag pot. Utilizing the inherent heat of the blast furnace slag, a reduction reaction occurs between the slag and fine-grained carbonaceous materials within the slag pot, reducing FeO in the blast furnace slag to metallic Fe. Because metallic Fe has a higher specific gravity than blast furnace slag, it will deposit at the bottom of the slag pot during railway transportation. Upon reaching the slag dumping point of the electric carbide furnace, the upper 3 / 4 of the molten slag (containing less Fe) is poured into the electric furnace via a chute for continued carbide smelting to produce low-iron carbide slag. This yields carbide slag with a total iron content of less than 1.5 wt%, offering advantages such as simple process, low cost, and high iron removal efficiency. By controlling the total iron content in the carbide slag to less than 1.5 wt%, it is possible to avoid system malfunctions, low output, and forced shutdowns caused by iron accumulation in low-temperature chlorination processes, demonstrating its feasibility.

[0039] The following description is based on specific embodiments.

[0040] Example 1

[0041] In this embodiment at a factory, molten titanium-containing blast furnace slag flowed from the blast furnace slag outlet into a slag pot. The weight of a single empty pot and a full pot was weighed using a weighing device, and the difference was the actual weight of titanium-containing blast furnace slag added. The actual amount of blast furnace slag added to a single slag pot was found to be 21.4 tons. 2140 kg of semi-coke powder with a particle size of 100-300 mesh was injected into the slag pot using nitrogen gas, ensuring thorough mixing of the blast furnace slag and carbonaceous material, and reducing the FeO in the blast furnace slag to metallic Fe.

[0042] Three to four slag pots were transported by rail to the slag dumping area of ​​the electric carbide furnace. After the shells were broken with a hammer, the top three-quarters of the molten slag (containing low Fe content) was added to the furnace via a chute. The weight of each of the three to four slag pots before and after dumping was measured, and the total difference was calculated to be 55 tons. Then, 6000 kg of semi-coke powder with a particle size of 100-300 mesh was added, and the furnace was continuously smelted for 120 minutes to obtain low-iron carbide slag. During this period, the active power of the electric furnace was controlled at 22 MW. After the low-iron carbide smelting was completed, slag removal began. High-pressure water was used to directly impact the molten slag during the removal process to obtain water-quenched slag. The water-quenched slag was dried and ground to 100-400 mesh to obtain low-iron carbide slag. Analysis showed that the total iron content in the low-iron carbide slag was 1.25 wt%, and the TiC content was 13.80 wt%.

[0043] The main components of the titanium-containing blast furnace slag in this embodiment are shown in Table 1:

[0044] Table 1. Main components of titanium-containing blast furnace slag (wt%)

[0045]

[0046] The industrial analysis composition of the semi-coke used in this embodiment is shown in Table 2:

[0047] Table 2. Industrial analysis composition of semi-coke (%)

[0048]

[0049] daf: dry ash-free basis; d: dry basis.

[0050] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for producing low-iron carbide slag, characterized in that, Includes the following steps: S1, molten titanium-containing blast furnace slag is fed into the slag pot from the blast furnace slag outlet, and carbonaceous reducing agent is added to the slag pot after the titanium-containing blast furnace slag is fed into the slag pot; S2, multiple slag pots containing titanium-containing blast furnace slag and carbonaceous reducing agent are transported from the blast furnace slag outlet to the slag dumping point of the carbide electric furnace, and the molten slag in the slag pots is kept stationary during transportation; S3, pour the predetermined amount of molten slag from the upper part of multiple slag pots into the carbide electric furnace, and add carbonaceous reducing agent into the carbide electric furnace for smelting. After smelting, the slag is discharged to obtain low iron carbide slag with Fe content of less than 1.5wt%. In step S3, the predetermined amount is 3 / 4 of the total amount of molten slag in the slag pot.

2. The method according to claim 1, characterized in that, In step S1, after titanium-containing blast furnace slag flows into the slag pot, a carbonaceous reducing agent is injected into the slag pot to ensure that the titanium-containing blast furnace slag and the carbonaceous reducing agent are fully mixed.

3. The method according to claim 1, characterized in that, In step S1, the temperature of the titanium-containing blast furnace slag flowing into the slag pot is 1350-1500℃.

4. The method according to claim 1, characterized in that, In step S1, the total amount of carbonaceous reducing agent added to the slag pot is 5%-10% of the mass of titanium-containing blast furnace slag added to the slag pot.

5. The method according to claim 1, characterized in that, The particle size of the carbonaceous reducing agent in steps S1 and S3 is between 100 and 300 mesh.

6. The method according to claim 1, characterized in that, The carbonaceous reducing agent in steps S1 and S3 is one or more of coke powder, semi-coke, anthracite, and graphite, wherein the fixed carbon content is ≥80%.

7. The method according to claim 1, characterized in that, In step S3, the mass of the carbonaceous reducing agent added to the carbonization furnace is 10%-20% of the total weight difference of the molten slag before and after it is poured into the carbonization furnace from multiple slag pots.

8. The method according to claim 1, characterized in that, In step S3, the smelting time is 90-120 minutes.

9. The method according to claim 1, characterized in that, In step S3, the molten slag is water-quenched during the slag removal process to obtain water-quenched slag; and the water-quenched slag is dried and ground to obtain the low-iron carbide slag.

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