Converter indirect oxidation vanadium extraction and dephosphorization method based on composite calcium ferrite

Abstract

The invention discloses a converter indirect oxidation synchronous vanadium extraction and dephosphorization method based on composite calcium ferrite, which comprises the following steps: crushing and screening the composite calcium ferrite, adding the undersize product into a converter through a top feeding system, stirring a molten pool in cooperation with bottom blowing inert gas, and discharging the molten pool; the compound calcium ferrite is used for exerting the dual functions of an oxidizing agent and a dephosphorizing agent, and efficient and synchronous vanadium extraction and dephosphorizing are achieved in the single converter. According to the method, the oxidizing agent and the dephosphorizing agent are integrated into the composite calcium ferrite, so that the effects of extracting vanadium and dephosphorizing are achieved in the single adding process, synchronous vanadium extraction and dephosphorizing in the single converter are achieved, the process limitation of a traditional duplex converter is broken through, the operation process is simplified, the smelting efficiency is improved, and the advantages of energy conservation and cost are also achieved; and a new technical path is provided for efficient smelting of the vanadium-containing molten iron.

Description

Technical Field

[0001] The present invention relates to the field of iron and steel metallurgy, and particularly to a converter indirect oxidation synchronous vanadium extraction and dephosphorization method based on calcium ferrite. Background Art

[0002] The smelting of Chinese vanadium-titanium magnetite mainly adopts the "blast furnace-converter" process. Among them, the double-converter process is an important technical means to realize vanadium extraction and dephosphorization from hot metal. Vanadium extraction and dephosphorization from hot metal are realized by using the converter for vanadium extraction and the steelmaking converter in series. However, the double-converter configuration leads to an extended overall production cycle, increased operation difficulty, and large energy losses and high energy consumption during the oxygen blowing process. Therefore, the development of a new converter smelting process that can achieve integrated vanadium extraction and dephosphorization is of great significance for process optimization and improving the efficient utilization of resources.

[0003] From a thermodynamic perspective, both vanadium extraction and dephosphorization from hot metal belong to the oxidation smelting process, and there is feasibility for process integration. However, there are differences in the requirements for oxidation conditions between the two. How to achieve their effective coordination is a technical difficulty. Patents CN201210239175.9, CN201510843774.5, and CN201610807157.4 propose technical solutions that use CaO-based slag systems as dephosphorizing agents for vanadium extraction in converters. By adding dephosphorizing agents in the front and back stages of blowing for vanadium extraction, synchronous vanadium extraction and dephosphorization in the converter are achieved, and the dephosphorization process has no obvious effect on the vanadium extraction effect. The examples show that the above methods can all achieve process indexes with a vanadium extraction rate greater than 85% and a dephosphorization rate greater than 30%. Although the above methods have achieved synchronous vanadium extraction and dephosphorization in the converter to a certain extent, the dephosphorization effect is not ideal. On the one hand, because a coolant needs to be added during the vanadium extraction process in the converter to control the molten pool temperature to ensure the oxidation of vanadium, the addition of the coolant will lead to insufficient basicity of the slag, and stable calcium phosphate cannot be formed in the slag, thus affecting the dephosphorization rate. On the other hand, since the dephosphorization reaction mainly occurs at the interface between the hot metal and the slag, the addition of CaO will affect the fluidity of the slag, limit the mass transfer of phosphorus from the hot metal to the slag, and the addition method of CaO may cause uneven slag composition, which will also have a certain impact on the dephosphorization process.

[0004] As a new smelting method, the indirect oxidation technology realizes the oxidation of different elements in the molten bath by regulating the composition of the oxidant. Moreover, the endothermic reaction characteristics avoid the drastic temperature fluctuation of the molten bath, eliminating the need for additional coolant addition. Patent CN201910396813.X uses a mixture of iron ore and lime in the hot metal pretreatment process to remove silicon, sulfur, and phosphorus from the hot metal; Patent CN201510005928.3 uses the method of injecting iron oxides into vanadium-containing hot metal, effectively reducing the oxygen consumption while ensuring the vanadium oxidation rate, verifying the feasibility of using iron oxides for indirect oxidation of vanadium extraction; Patent CN201510006728.X proposes to add iron oxides to the top of the hot metal ladle to oxidize vanadium in the hot metal without oxygen injection, and the vanadium extraction rate in the examples reaches up to 92.14%. However, the reaction rate in the indirect oxidation process is relatively slow. The treatment time in the above examples is usually about 15 minutes, reducing the process efficiency.

[0005] Based on the indirect oxidation process method, in order to achieve the simultaneous extraction of vanadium and dephosphorization from hot metal, an oxidant system mainly composed of CaO and Fe2O3 needs to be used. As a low-melting-point oxidant, calcium ferrite can not only meet the component requirements for vanadium extraction and dephosphorization but also improve the reaction efficiency. Therefore, developing a converter indirect oxidation method for simultaneous vanadium extraction and dephosphorization based on calcium ferrite, which can shorten the reaction time and improve the reaction efficiency, has broad development potential and application prospects. Summary of the Invention

[0006] In view of the above deficiencies, the present invention proposes a converter indirect oxidation method for simultaneous vanadium extraction and dephosphorization based on calcium ferrite. This method utilizes the low melting point of calcium ferrite to reduce the slag formation temperature, thereby increasing the reaction rate. At the same time, it fully exerts the oxidizing property of calcium ferrite to achieve efficient extraction of vanadium and phosphorus through indirect oxidation reactions.

[0007] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0008] The present invention first discloses a converter indirect oxidation method for simultaneous vanadium extraction and dephosphorization based on calcium ferrite, including:

[0009] S1. Load calcium ferrite into a pair-roll crusher for crushing and screening. The screened samples are crushed again to obtain the first intermediate material.

[0010] S2. Pour hot metal into the converter. When maintaining the hot metal at 1300 - 1400 °C, transfer the first intermediate material to the converter, and simultaneously inject inert gas through bottom blowing.

[0011] S3. After the reaction time reaches the requirement, end the blowing and discharge vanadium slag and semi-steel.

[0012] Further, the composition of the calcium ferrite composite in step S1 includes raw materials with the following mass percentages:

[0013] The content of Fe2O3 is 60 - 80 wt%;

[0014] The content of CaO is 10 - 20 wt%;

[0015] The content of SiO2 is 0 - 10 wt%;

[0016] The content of Al2O3 is 0 - 25 wt%,

[0017] The balance is inevitable impurities.

[0018] Further, the screening particle size in step S1 is 1 - 5 mm.

[0019] Further, the time for transferring the first intermediate material to the converter in step S2 is 1 - 3 min; the charging addition amount is 40 - 70 kg / (tFe).

[0020] Further, the time for transferring the first intermediate material to the converter is 3 min; the charging addition amount is 60 kg / (tFe).

[0021] Further, the inert gas in step S2 is nitrogen or argon; the injection intensity of the inert gas is 0.01 - 0.8 m 3 / (min·tFe).

[0022] Further, the inert gas is nitrogen; the injection intensity is 0.7 m 3 / (min·tFe).

[0023] Further, after the reaction time in step S3 reaches 6 - 10 min, the blowing is ended.

[0024] Further, after the reaction time reaches 8 min, the blowing is ended.

[0025] Compared with the prior art, the advantages of the present invention are as follows:

[0026] (1) The present invention integrates the oxidant and dephosphorizer required for vanadium extraction and dephosphorization into the calcium ferrite composite, enabling it to simultaneously play the roles of vanadium extraction and dephosphorization during a single addition process, effectively reducing the types of materials and addition steps, simplifying the operation process, and helping to improve the smelting efficiency;

[0027] (2) While ensuring the vanadium extraction rate and dephosphorization rate, the present invention breaks through the process limitations of traditional double-converter furnaces, realizes simultaneous vanadium extraction and dephosphorization in a single converter, and has energy-saving and cost advantages, providing a new technical path for the efficient smelting of vanadium-containing hot metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the process flow chart of the embodiment of the present invention. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] In the present invention, "kg / (tFe)" represents the mass of a certain substance corresponding to each unit mass of total iron, and the unit is kilograms per (ton of total iron).

[0031] In the present invention: m 3 / (min·tFe)" is a composite unit, representing cubic meters per (ton of total iron) per minute. In the context of the present invention, it means that for every 1 ton of total iron produced, 0.01 - 0.8 m 3 of inert gas participates in the reaction or is consumed, discharged, etc.

[0032] Embodiment 1

[0033] A converter indirect oxidation synchronous vanadium extraction and phosphorus removal method based on calcium ferrite

[0034] S1. Crush the calcium ferrite with a pair-roll crusher, and the roll spacing is 2 mm;

[0035] S2. Screen the product crushed in S1 through a vibrating screen, the screen hole size is 2 mm, and the product on the screen is returned to S1 for secondary crushing;

[0036] S3. Feed the calcium ferrite under the screen in S2 into the storage bin;

[0037] S4. After the hot metal is charged into a 120 t converter, the temperature of the hot metal is measured to be 1310 °C, feed materials from the bin into the converter, the feeding time is 2 min, and the total addition amount is 45 kg / (tFe);

[0038] S5. Inject nitrogen through bottom blowing, and the blowing intensity is 0.7 m 3 / (min·tFe);

[0039] S6. Start timing after the calcium ferrite is added completely. When the reaction reaches 8 min, stop blowing, and discharge vanadium slag and semi-steel.

[0040] After detection, the hot metal contains [V] 0.320%, [P] 0.099%, [C] 4.430%; the semi-steel obtained from vanadium extraction contains [V] 0.046%, [P] 0.016%, [C] 3.530%. The total iron content of the vanadium slag is 40.00 wt%, the V2O5 content is 11.65 wt%, the CaO content is 13.11 wt%, the SiO2 content is 7.40 wt%, the Al2O3 content is 6.57 wt%, the TiO2 content is 2.28 wt%, the MnO content is 2.31 wt%, the Cr2O3 content is 2.07 wt%, the P content is 1.34 wt%, and the balance is inevitable impurities.

[0041] Example 2

[0042] A converter indirect oxidation synchronous vanadium extraction and dephosphorization method based on calcium ferrite

[0043] S1. Crush the calcium ferrite with a pair-roll crusher, and the roll spacing is 2 mm;

[0044] S2. Screen the product crushed in S1 through a vibrating screen, the screen hole size is 1 mm, and the product on the screen is returned to S1 for secondary crushing;

[0045] S3. Feed the undersize calcium ferrite in S2 into the storage bin;

[0046] S4. After the hot metal is charged into a 90 t converter, the hot metal temperature is measured at 1350 °C, feed materials from the bin into the converter, the feeding time is 3 min, and the total addition amount is 60 kg / (tFe);

[0047] S5. Inject nitrogen through bottom blowing, and the blowing intensity is 0.6 m 3 / (min·tFe);

[0048] S6. Start timing after the calcium ferrite is added completely. When the reaction reaches 8 min, stop blowing and discharge the vanadium slag and semi-steel.

[0049] After detection, the hot metal contains [V] 0.311%, [P] 0.071%, [C] 4.350%; the semi-steel obtained from vanadium extraction contains [V] 0.032%, [P] 0.010%, [C] 3.390%. The total iron content of the vanadium slag is 34.12 wt%, the V2O5 content is 13.38 wt%, the CaO content is 10.64 wt%, the SiO2 content is 10.69 wt%, the Al2O3 content is 7.21 wt%, the TiO2 content is 5.30 wt%, the MnO content is 3.60 wt%, the Cr2O3 content is 2.31 wt%, the P content is 0.92 wt%, and the balance is inevitable impurities.

[0050] Example 3

[0051] A method for simultaneous vanadium extraction and phosphorus removal by indirect oxidation in a converter based on calcium ferrite composite

[0052] S1. Crush the calcium ferrite composite with a pair-roll crusher, and the roll spacing is 2 mm;

[0053] S2. Screen the product crushed in S1 through a vibrating screen, the screen hole size is 1 mm, and the product on the screen is returned to S1 for secondary crushing;

[0054] S3. Feed the undersize calcium ferrite composite in S2 into the storage bin;

[0055] S4. After the hot metal is charged into a 90 t converter, the temperature of the hot metal is measured to be 1340 °C, feed materials from the bin into the converter, the feeding time is 3 min, and the total addition amount is 50 kg / (tFe);

[0056] S5. Inject nitrogen through bottom blowing, and the blowing intensity is 0.8 m 3 / (min·tFe);

[0057] S6. Start timing after the addition of the calcium ferrite composite is completed. When the reaction reaches 8 min, stop blowing, and tap vanadium slag and semi-steel.

[0058] After detection, the hot metal contains [V] 0.300%, [P] 0.086%, [C] 4.350%; in the semi-steel obtained from vanadium extraction, [V] is 0.032%, [P] is 0.020%, [C] is 3.530%. The total iron content of the vanadium slag is 34.49 wt%, the V2O5 content is 12.21 wt%, the CaO content is 12.73 wt%, the SiO2 content is 10.49 wt%, the Al2O3 content is 5.43 wt%, the TiO2 content is 5.80 wt%, the MnO content is 4.61 wt%, the Cr2O3 content is 1.94 wt%, the P content is 1.28 wt%, and the balance is inevitable impurities.

[0059] Example 4

[0060] A method for simultaneous vanadium extraction and phosphorus removal by indirect oxidation in a converter based on calcium ferrite composite

[0061] S1. Crush the calcium ferrite composite with a pair-roll crusher, and the roll spacing is 2 mm;

[0062] S2. Screen the product crushed in S1 through a vibrating screen, the screen hole size is 1 mm, and the product on the screen is returned to S1 for secondary crushing;

[0063] S3. Feed the undersize calcium ferrite composite in S2 into the storage bin;

[0064] S4. After the hot metal is charged into the 120t converter, the temperature of the hot metal is measured to be 1350°C. Materials are fed into the converter from the storage bin, the feeding time is 3 min, and the total addition amount is 65 kg / (tFe).

[0065] S5. Nitrogen is blown in through bottom blowing, and the blowing intensity is 0.5 m 3 / (min·tFe);

[0066] S6. After the addition of calcium ferrite is completed, timing starts. When the reaction reaches 6 min, the blowing is stopped, and vanadium slag and semi-steel are tapped.

[0067] After detection, the hot metal contains [V] 0.310%, [P] 0.085%, [C] 4.320%; the semi-steel obtained from vanadium extraction contains [V] 0.030%, [P] 0.014%, [C] 3.440%. The total iron content of the vanadium slag is 19.99 wt%, the V2O5 content is 13.37 wt%, the CaO content is 28.26 wt%, the SiO2 content is 12.13 wt%, the Al2O3 content is 5.43 wt%, the TiO2 content is 5.75 wt%, the MnO content is 4.67 wt%, the Cr2O3 content is 2.59 wt%, the P content is 1.93 wt%, and the balance is inevitable impurities.

[0068] Example 5

[0069] A converter indirect oxidation synchronous vanadium extraction and dephosphorization method based on calcium ferrite

[0070] S1. The calcium ferrite is crushed by a pair-roll crusher, and the roll spacing is 2 mm;

[0071] S2. The product crushed in S1 is screened by a vibrating screen, the screen hole size is 1 mm, and the product on the screen is returned to S1 for secondary crushing;

[0072] S3. The calcium ferrite passing through the screen in S2 is sent into the storage bin;

[0073] S4. After the hot metal is charged into the 120t converter, the temperature of the hot metal is measured to be 1370°C. Materials are fed into the converter from the storage bin, the feeding time is 3 min, and the total addition amount is 55 kg / (tFe);

[0074] S5. Nitrogen is blown in through bottom blowing, and the blowing intensity is 0.5 m 3 / (min·tFe);

[0075] S6. After the addition of calcium ferrite is completed, timing starts. When the reaction reaches 8 min, the blowing is stopped, and vanadium slag and semi-steel are tapped.

[0076] After detection, the hot metal contains [V] 0.332%, [P] 0.090%, [C] 4.270%; the semi-steel obtained from vanadium extraction contains [V] 0.024%, [P] 0.030%, [C] 3.520%. The total iron content of the vanadium slag is 28.08 wt%, the V2O5 content is 12.21 wt%, the CaO content is 18.73 wt%, the SiO2 content is 11.49 wt%, the Al2O3 content is 3.25 wt%, the TiO2 content is 8.70 wt%, the MnO content is 5.64 wt%, the Cr2O3 content is 2.50 wt%, the P content is 1.28 wt%, and the balance is inevitable impurities.

[0077] Comparative Example 1

[0078] The converter synchronous vanadium extraction and dephosphorization were carried out according to the method of Example 1. The difference is that in step S1, instead of adding calcium ferrite, the raw materials for preparing calcium ferrite were directly added.

[0079] After detection, the hot metal contains [V] 0.320%, [P] 0.099%, [C] 4.430%; the semi-steel obtained from vanadium extraction contains [V] 0.080%, [P] 0.030%, [C] 3.200%. The total iron content of the vanadium slag is 35.00 wt%, the V2O5 content is 10.01 wt%, the CaO content is 16.07 wt%, the SiO2 content is 8.17 wt%, the Al2O3 content is 7.25 wt%, the TiO2 content is 0.82 wt%, the MnO content is 3.32 wt%, the Cr2O3 content is 3.05 wt%, the P content is 1.27 wt%, and the balance is inevitable impurities.

[0080] Comparative Example 2

[0081] The converter synchronous vanadium extraction and dephosphorization were carried out according to the method of Example 1. The difference is that in step S1, instead of adding calcium ferrite, the raw materials for preparing calcium ferrite were directly added; the reaction time in step S6 was 15 min.

[0082] After detection, the hot metal contains [V] 0.320%, [P] 0.099%, [C] 4.430%; the semi-steel obtained from vanadium extraction contains [V] 0.064%, [P] 0.013%, [C] 3.080%. The total iron content of the vanadium slag is 37.75 wt%, the V2O5 content is 10.92 wt%, the CaO content is 16.47 wt%, the SiO2 content is 10.95 wt%, the Al2O3 content is 6.75 wt%, the TiO2 content is 5.42 wt%, the MnO content is 3.03 wt%, the Cr2O3 content is 2.52 wt%, the P content is 1.48 wt%, and the balance is inevitable impurities.

[0083] According to the comparison between the examples and the comparative examples, it is found that when using the unprepared calcium ferrite composite raw material as the oxidant, the vanadium extraction and dephosphorization indexes of Comparative Example 1 are lower than those of Example 1 under the same reaction time; in Comparative Example 2, although the vanadium extraction and dephosphorization indexes are improved by extending the reaction time, it leads to an increase in energy consumption and a decrease in process efficiency. The examples prove that by using calcium ferrite composite as the oxidant, the present invention effectively reduces the reaction time while ensuring the vanadium extraction and dephosphorization effects. Therefore, compared with the prior art, the present invention has the advantages of high reaction efficiency, simple process flow and simple operation, providing reliable technical support for the development of the converter synchronous vanadium extraction and dephosphorization process.

[0084] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter based on composite calcium ferrite, comprising: S1, loading the composite calcium ferrite into a double-roll crusher for crushing and screening, and the screened sample is crushed again to obtain a first intermediate material; S2, adding molten iron into the converter, maintaining the molten iron at 1300-1400°C, transferring the first intermediate material into the converter, and injecting inert gas through bottom blowing; S3. After the reaction time reaches the requirement, the blowing is terminated and vanadium slag and semi-steel are produced.

2. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 1, wherein: The composition of the composite calcium ferrite in step S1 includes the following raw materials in percentage by mass: Fe2O3 content is 60-80wt%; CaO content is 10-20wt%; SiO2 content is 0-10wt%; Al2O3 content is 0-25wt%, The balance is inevitable impurities.

3. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 1, wherein: The screening particle size in step S1 is 1-5 mm.

4. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 1, wherein: The time for transferring the first intermediate material to the converter in step S2 is 1-3 minutes; The amount of material added is 40-70 kg / (tFe).

5. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 3, wherein: The time for transferring the first intermediate material to the converter is 3 minutes; The amount of material added is 60kg / (tFe).

6. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 1, wherein: The inert gas in step S2 is nitrogen or argon; The blowing intensity of the inert gas is 0.01-0.8m 3 / (min·tFe).

7. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 6, wherein: The inert gas is nitrogen; The blowing intensity is 0.7m 3 / (min·tFe).

8. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 1, wherein: After the reaction time in step S3 reaches 6-10 minutes, the blowing is terminated.

9. The method for simultaneous vanadium extraction and dephosphorization by indirect oxidation in a converter according to claim 8, wherein: After the reaction time reaches 8 minutes, the blowing is terminated.

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