Composite vanadium-titanium pellet and preparation method thereof

Abstract

The invention discloses composite vanadium-titanium pellets and a preparation method thereof, and belongs to the technical field of Panzhian steel blast furnace smelting. The composite vanadium-titanium pellet comprises a core-layer vanadium-titanium furnace burden and a shell-layer vanadium-titanium furnace burden, the nuclear layer vanadium-titanium furnace burden comprises vanadium-titanium magnetite concentrate and an adhesive; and the shell vanadium-titanium furnace burden comprises vanadium-titanium magnetite concentrate, common ore iron concentrate and an adhesive. According to the composite vanadium-titanium pellet, the low-titanium furnace charge wraps the high-titanium furnace charge to form a barrier layer, chemical reaction between TiO2 in the vanadium-titanium pellet and C in coke in the blast furnace smelting process is reduced, and therefore generation of high-melting-point phases, such as TiC, TiN or Ti (C, N), which cannot be melted under the blast furnace smelting condition is reduced, and the yield of the composite vanadium-titanium pellet is improved. Finally, the problems of cost increase and potential safety hazards caused by the fact that the slag becomes sticky are obviously reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of blast furnace smelting in Pangang, and particularly to a composite vanadium-titanium pellet and a preparation method thereof. Background Art

[0002] Increasing the proportion of vanadium-titanium ore and the ratio of vanadium-titanium pellets in the blast furnace burden structure is an effective technical measure to reduce the cost of pig iron in the blast furnace of Pangang and reduce CO 2 emissions. However, with the increase in the proportion of vanadium-titanium ore and the ratio of pellets, the TiO 2 content in the slag increases, and the TiC, TiN and their solid solution Ti(C,N) formed by the reduction of TiO 2 during the blast furnace smelting process increase. The viscosity of the slag is more likely to deteriorate, resulting in an increase in the difficulty of blast furnace smelting, an increase in the amount of iron carried by the slag, a deterioration of technical and economic indicators, and even abnormal furnace conditions. How to reduce the reduction of TiO 2 during the blast furnace smelting process has always been the focus of attention in the blast furnace smelting of Pangang.

[0003] Production practice shows that increasing the ratio of vanadium-titanium pellets in the blast furnace burden structure can significantly reduce the TiO 2 content in the sinter and increase the CaO + SiO 2 content in the sinter, significantly improving the quality of the sinter. However, the TiO 2 content in the existing vanadium-titanium pellets is still as high as about 10%. During the smelting process, as the temperature rises, the TiO 2 in the softened pellets will react with C and N 2 in the directly contacted coke or metallic iron to form TiC and TiN. The results of the dissection of the experimental blast furnace confirmed that a large amount of TiC and TiN have been formed in the softening-melting zone of the blast furnace. Secondly, the slag-forming phases of the burden after softening and melting are not completely fused and homogenized, and the TiO 2 content of the slag-forming phases is very high, and titanium carbonitride is easily formed, leading to the deterioration of the slag properties.

[0004] Therefore, researching and developing a method to slow down the reduction of TiO 2 in the pellets is of great significance for reducing the cost of pig iron in the blast furnace of Pangang and reducing pollution. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a composite vanadium-titanium pellet and a preparation method thereof. The composite vanadium-titanium pellet can significantly reduce the cost and potential safety hazards in the blast furnace smelting process of vanadium-titanium pellets.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] The present invention provides a composite vanadium-titanium pellet, which comprises a core-layer vanadium-titanium charge and a shell-layer vanadium-titanium charge;

[0008] The core-layer vanadium-titanium charge comprises vanadium-titanium magnetite concentrate and a binder;

[0009] The shell-layer vanadium-titanium charge comprises vanadium-titanium magnetite concentrate, ordinary iron ore concentrate and a binder.

[0010] The present invention wraps the above-mentioned core-layer vanadium-titanium charge with the above-mentioned shell-layer vanadium-titanium charge, so as to form a low-titanium barrier layer on the surface of the core-layer vanadium-titanium charge, thereby reducing the direct contact between the softened vanadium-titanium charge and coke, and thus reducing the reduction of TiO 2 .

[0011] Preferably, the basicity w(CaO) / w(SiO 2 ) of the core-layer vanadium-titanium charge ≤ 0.6; more preferably, the basicity of the core-layer vanadium-titanium charge 0.3 ≤ w(CaO) / w(SiO 2 ) ≤ 0.5. In some specific embodiments of the present invention, it is preferably 0.364, 0.586 or 0.455.

[0012] The content of TiO 2 in the core-layer vanadium-titanium charge is 7%-13%.

[0013] Preferably, the content of TiO 2 in the shell-layer vanadium-titanium charge ≤ 2%, and the proportion of TiO 2 in the five components of CaO, SiO 2 , MgO, Al 2 O 3 , TiO 2 ≤ 10%;

[0014] More preferably, the content of TiO 2 in the shell-layer vanadium-titanium charge ≤ 1.6%; further preferably 1.52%, 1.27% or 0.897%;

[0015] More preferably, the proportion of TiO 2 in the five components of CaO, SiO 2 , MgO, Al 2 O 3 , TiO 2 ≤ 9.3%; further preferably 9.25%, 7.41% or 4.94%;

[0016] Preferably, the basicity w(CaO) / w(SiO 2 ) of the shell-layer vanadium-titanium charge ≤ 1.0 and is greater than or equal to the basicity of the core-layer vanadium-titanium charge; more preferably, the basicity of the shell-layer vanadium-titanium charge 0.6 ≤ w(CaO) / w(SiO2 ) ≤ 0.95 and is greater than or equal to the basicity of the nuclear layer vanadium-titanium burden. In some specific embodiments of the present invention, it is preferably 0.606, 0.839 or 0.943.

[0017] Preferably, in the present invention, the diameter of the nuclear layer vanadium-titanium burden is 16 - 18 mm;

[0018] Preferably, the thickness of the shell layer vanadium-titanium burden is 0.5 - 4 mm.

[0019] Preferably, in the present invention, the binder is selected from bentonite or polyacrylamide; more preferably bentonite.

[0020] Preferably, in the present invention, the nuclear layer vanadium-titanium burden further includes quicklime.

[0021] Preferably, the shell layer vanadium-titanium burden further includes quicklime.

[0022] The quicklime is used to adjust the basicity.

[0023] More preferably, in the present invention, both the nuclear layer vanadium-titanium burden and the shell layer vanadium-titanium burden contain quicklime, or only the shell layer vanadium-titanium burden contains quicklime.

[0024] The present invention also provides a method for preparing the above-mentioned composite vanadium-titanium pellet ore, comprising the following steps:

[0025] (1) Mix the raw materials of the nuclear layer vanadium-titanium burden, pelletize, and screen to obtain green pellets 1;

[0026] (2) After mixing the raw materials of the shell layer vanadium-titanium burden, mix them with the green pellets obtained in step (1), and pelletize to obtain composite green pellets 2;

[0027] (3) Subject the composite green pellets 2 prepared in step (2) to drying, preheating, and roasting in sequence to obtain the above-mentioned composite vanadium-titanium pellet ore.

[0028] Preferably, in the present invention, during pelletizing in steps (1) and (2), the moisture content of the raw materials needs to be independently controlled at 7.5% - 8.5%. More preferably 7.8% - 8.5%.

[0029] Preferably, in the present invention, the drying temperature in step (3) is 110°C - 1250°C; more preferably 110 - 500°C. In some specific embodiments of the present invention, it is preferably 120°C.

[0030] Preferably, the preheating temperature is 950°C - 1150°C; more preferably 950°C - 1000°C; in some specific embodiments of the present invention, it is preferably 950°C or 980°C.

[0031] Preferably, the roasting temperature is 1250°C - 1280°C; more preferably 1260°C - 1270°C. In some specific embodiments of the present invention, it is preferably 1260°C. In the above preparation method, the pelletizing time in step (1) is preferably 20 - 25 min.

[0032] After the core layer vanadium-titanium burden obtained by screening in step (1) to have a diameter of 16 - 18 mm is the green pellet 1, the green pellets smaller than 16 mm and larger than 18 mm are crushed and then returned for continuous pelletizing.

[0033] When the binder in the raw materials of the core layer vanadium-titanium burden in step (1) is selected from bentonite, its content is 1.5% - 2.0% of the total amount of the raw materials.

[0034] When the binder in the raw materials of the shell layer vanadium-titanium burden in step (2) is selected from bentonite, its content is 1.5% - 2.0% of the total amount of the raw materials.

[0035] The pelletizing time in step (2) is preferably 3 - 5 min.

[0036] After the roasting in step (3) is completed, post-treatments such as cooling are also included.

[0037] Compared with the prior art, the composite vanadium-titanium pellet ore provided by the present invention includes a core layer vanadium-titanium burden and a shell layer vanadium-titanium burden; the core layer vanadium-titanium burden includes vanadium-titanium magnetite concentrate and a binder; the shell layer vanadium-titanium burden includes vanadium-titanium magnetite concentrate, ordinary iron ore concentrate and a binder. The composite vanadium-titanium pellet ore forms a barrier layer by wrapping the high-titanium burden with the low-titanium burden, reducing the chemical reaction between TiO in the vanadium-titanium pellet ore and C in the coke during the blast furnace smelting process, thereby reducing the formation of high-melting-point phases such as TiC, TiN or Ti(C,N) that cannot be melted under the blast furnace smelting conditions, and finally significantly reducing the cost increase and safety hazard problems caused by the slag becoming viscous. 2 With the C in the coke, thus reducing the formation of high-melting-point phases such as TiC, TiN or Ti(C,N) that cannot be melted under the blast furnace smelting conditions, and finally significantly reducing the cost increase and safety hazard problems caused by the slag becoming viscous. Specific Embodiments

[0038] In order to further illustrate the present invention, the composite vanadium-titanium pellet ore and its preparation method provided by the present invention will be described in detail below with reference to the embodiments.

[0039] The following green pellet 1 is the core layer vanadium-titanium burden in the composite vanadium-titanium pellet ore described in the present invention; the second layer burden is the shell layer vanadium-titanium burden in the composite vanadium-titanium pellet ore described in the present invention.

[0040] The following TFe represents total iron.

[0041] Example 1

[0042] Prepare the composite pellet ore with the raw materials shown in Table 1.

[0043] After mixing 98.5 parts of vanadium-titanium magnetite concentrate and 1.5 parts of bentonite, pelletizing is carried out in a disk pelletizer for 25 min, controlling the moisture content to be 8.0%. After the green pellets are screened by a screening machine, dry green pellets 1 with a diameter of 16 - 18 mm are obtained. The basicity of green pellets 1 is 0.364 and the TiO 2 content is 12.77%.

[0044] Mix 12 parts of vanadium-titanium magnetite concentrate, 84.5 parts of ordinary iron ore concentrate, 2 parts of quicklime and 1.5 parts of bentonite to obtain the second layer of burden. Control its basicity to be 0.606 and the TiO 2 content to be 1.52%. The TiO 2 In the five components of CaO, SiO 2 , MgO, Al 2 O 3 , TiO 2 the proportion is 9.25% (as shown in Table 2). Then mix the second layer of burden with green pellets 1 and pelletize in a disk pelletizer for 3.5 min, controlling the moisture content to be 7.8% to obtain composite green pellets 2. After measurement, the proportion of composite green pellets 2 with a diameter of 16.5 - 22 mm is 92%.

[0045] The above composite green pellets 2 are dried at 120 °C for 25 min in sequence, preheated at 950 °C for 27 min, roasted at 1260 °C for 16 min, and after cooling, composite vanadium-titanium pellet ore is prepared. After testing, its compressive strength is 2413 N / piece, and the chemical composition is as shown in Table 2.

[0046] Table 1 Chemical composition of raw materials

[0047]

[0048]

[0049] Table 2 Chemical composition of composite vanadium-titanium pellet ore

[0050]

[0051] Example 2

[0052] Prepare composite pellet ore with the raw materials shown in Table 1.

[0053] After mixing 97.5 parts of vanadium-titanium magnetite concentrate, 1 part of quicklime and 1.5 parts of bentonite, pelletizing is carried out in a disk pelletizer for 20 min, controlling the moisture content to be 8.3%. After the green pellets are screened by a screening machine, dry green pellets 1 with a diameter of 16 - 18 mm are obtained. The basicity of green pellets 1 is 0.586 and the TiO 2 content is 12.15%.

[0054] Mix 10 parts of vanadium-titanium magnetite concentrate, 85.5 parts of ordinary iron ore concentrate, 3.5 parts of quicklime and 1 part of bentonite to obtain the second layer of burden, and control its basicity to be 0.839 and the TiO 2 content to be 1.27%, and the TiO 2 in CaO, SiO 2 , MgO, Al 2 O 3 , TiO 2 accounts for 7.41% in the five components (as shown in Table 3). Then, mix the second layer of burden with green pellet 1 and pelletize in a disc pelletizer for 4 min, control the moisture content to be 8.1%, and obtain composite green pellet 2. After measurement, the proportion of composite green pellet 2 with a diameter of 16.5 - 22 mm is 93.7%.

[0055] After drying the above composite green pellet 2 at 120 °C for 22 min in sequence, preheating at 950 °C for 25 min, roasting at 1260 °C for 15 min, and cooling, composite vanadium-titanium pellet ore is prepared. After testing, its compressive strength is 2357 N / piece, and the chemical composition is shown in Table 3.

[0056] Table 3 Chemical composition of composite vanadium-titanium pellet ore

[0057]

[0058] Example 3

[0059] Prepare composite pellet ore with the raw materials shown in Table 1.

[0060] After mixing 97.5 parts of vanadium-titanium magnetite concentrate, 0.5 part of quicklime, and 2 parts of bentonite, pelletize in a disc pelletizer for 22 min, control the moisture content to be 8.5%, and after screening the obtained green pellets through a screening machine, dry green pellet 1 with a diameter of 16 - 18 mm is obtained. The basicity of green pellet 1 is 0.455 and the TiO 2 content is 12.16%.

[0061] Mix 7 parts of vanadium-titanium magnetite concentrate, 87 parts of ordinary iron ore concentrate, 4.5 parts of quicklime and 1.5 parts of bentonite to obtain the second layer of burden, and control its basicity to be 0.943 and the TiO 2 content to be 0.897%, and the TiO 2 in CaO, SiO 2 , MgO, Al 2 O 3 , TiO 2 accounts for 4.94% in the five components (as shown in Table 4). Then, mix the second layer of burden with green pellet 1 and pelletize in a disc pelletizer for 5 min, control the moisture content to be 8.4%, and obtain composite green pellet 2. After measurement, the proportion of composite green pellet 2 with a diameter of 16.5 - 22 mm is 93%.

[0062] After drying the above-mentioned composite green balls 2 at 120 °C for 28 min in sequence, preheating them at 980 °C for 22 min, roasting them at 1260 °C for 18 min, and cooling, composite vanadium-titanium pellet ore is prepared. After testing, its compressive strength is 2289 N / piece, and its chemical composition is shown in Table 4.

[0063] Table 4 Chemical composition of composite vanadium-titanium pellet ore

[0064]

[0065] R in Tables 2, 3, and 4 above 2 All represent basicity, specifically the mass fraction ratio of CaO to SiO 2 2.

[0066] Comparative Example 1

[0067] Same as Example 1, composite pellet ore is prepared with the raw materials shown in Table 1.

[0068] After mixing 98.5 parts of vanadium-titanium magnetite concentrate and 1.5 parts of bentonite evenly, pelletizing is carried out in a disk pelletizer for 25 min, and the water content is controlled at 8.0%. After the obtained green balls are screened by a screening machine, dry green balls 1 with a diameter of 16 - 18 mm are obtained. The basicity of green balls 1 is 0.364, and the TiO 2 content is 12.77%.

[0069] Application Example 1

[0070] The composite vanadium-titanium pellet ore prepared in Example 1 above and the green balls 1 prepared in Comparative Example 1 are respectively smelted in a blast furnace together with sintered ore at 1200 m 3 In the blast furnace smelting, under the conditions that the TiO 2 content in the slag is 22.75% - 22.85% and the Ti content in the hot metal is 0.10% - 0.18%, the viscosity of the slag in Comparative Example 1 at 1470 °C is 0.435 Pa·S, and the sum of the TiC and TiN contents is 0.637%. While the viscosity of the slag in Example 1 at 1470 °C is 0.286 Pa·S, and the sum of the TiC and TiN contents is 0.388%. This shows that the composite vanadium-titanium pellet ore described in the present invention significantly reduces the possibility of the slag becoming viscous under the blast furnace smelting conditions, which is beneficial to solving the problems of cost increase and potential safety hazards.

[0071] The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A composite vanadium-titanium pellet, characterized in that: Including core layer vanadium titanium furnace charge and shell layer vanadium titanium furnace charge; The core layer vanadium-titanium furnace charge includes vanadium-titanium magnetite concentrate and a binder; The shell vanadium-titanium furnace charge comprises vanadium-titanium magnetite concentrate, common iron ore concentrate and adhesive.

2. The composite vanadium-titanium pellet according to claim 1, characterized in that: The basicity of the core layer vanadium-titanium furnace charge is w(CaO) / w(SiO2)≤0.

6.

3. The composite vanadium-titanium pellet according to claim 1, characterized in that: The content of TiO2 in the shell vanadium-titanium furnace charge is ≤2%, and the proportion of TiO2 in the five components of CaO, SiO2, MgO, Al2O3 and TiO2 is ≤10%; The basicity of the shell layer vanadium titanium furnace charge w(CaO) / w(SiO2)≤1.0, and is greater than or equal to the basicity of the core layer vanadium titanium furnace charge.

4. The composite vanadium-titanium pellet according to claim 1, characterized in that: The diameter of the core layer vanadium-titanium charge is 16-18 mm; The thickness of the shell vanadium-titanium furnace charge is 0.5-4 mm.

5. The composite vanadium-titanium pellet according to claim 1, characterized in that: The adhesive is selected from bentonite or polyacrylamide.

6. The composite vanadium-titanium pellet according to claim 1, characterized in that: The core layer vanadium-titanium furnace charge also includes quicklime.

7. The composite vanadium-titanium pellet according to claim 1 or 6, characterized in that: The shell vanadium-titanium furnace charge also includes quicklime.

8. The method for preparing composite vanadium-titanium pellets according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) mixing raw materials of core layer vanadium and titanium charge, pelletizing, and screening to obtain green balls 1; (2) mixing the raw materials of the shell vanadium-titanium furnace charge evenly with the green balls obtained in step (1) to form balls, thereby obtaining composite green balls 2; (3) The composite green ball 2 prepared in step (2) is dried, preheated, and roasted in sequence to obtain the composite vanadium-titanium pellet.

9. The preparation method according to claim 8, characterized in that: During the pelletizing in steps (1) and (2), the moisture content of the raw materials needs to be independently controlled to be 7.5%-8.5%.

10. The preparation method according to claim 8, characterized in that: The drying temperature in step (3) is 110°C-1250°C; The preheating temperature is 950°C-1150°C; The calcination temperature is 1250°C-1280°C.

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