Method for improving hydrogen-rich reduction degradation of vanadium titano-magnetite pellets

Abstract

The invention discloses a method for improving hydrogen-rich reduction degradation of vanadium titano-magnetite pellets, which comprises the following steps: first-stage reduction: the vanadium titano-magnetite oxidized pellets are placed in a hydrogen-based shaft furnace for first-stage reduction, the reduction gas is a mixed gas of H2 and N2, the reduction temperature is 400-700 DEG C, and the reduction time is 30-60 minutes; second-stage reduction is conducted, specifically, the pellets obtained after first-stage reduction are subjected to second-stage reduction, high-temperature reduction is conducted in the hydrogen-rich mixed atmosphere in the second-stage reduction, the reduction temperature ranges from 900 DEG C to 1050 DEG C, and the reduction time ranges from 60 min to 90 min; the performance indexes of the vanadium titano-magnetite metallized pellet product are as follows: the pellet strength is greater than 800N / P, the low-temperature reduction degradation index RDI + 6.3 mm is greater than 90%, and the metallization ratio is greater than or equal to 94%. The problem that in an existing hydrogen-based shaft furnace pre-reduction technology, vanadium titano-magnetite pellets are seriously pulverized is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of low-carbon metallurgical utilization, and particularly relates to a method for improving hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets. BACKGROUND

[0002] Vanadium-titanium magnetite is an important source of iron, vanadium and titanium, and is also associated with important metal components such as chromium, cobalt, nickel and scandium, and has extremely high comprehensive utilization value and is internationally recognized as a strategic mineral. The comprehensive utilization method of vanadium-titanium magnetite includes the blast furnace method and the non-blast furnace method. For a long time, the mainstream process of vanadium-titanium magnetite concentrate smelting is the blast furnace method with sintering / pelletizing for lumping, blast furnace ironmaking and converter vanadium extraction as the main process. Although the blast furnace method has large processing capacity and stable production, the vanadium-titanium recovery rate is low, and in particular, the titanium resources in vanadium-titanium magnetite cannot be effectively utilized.

[0003] Hydrogen-based shaft furnace pre-reduction-electric furnace smelting is a representative process of the non-blast furnace method, which can realize the smelting of full vanadium-titanium magnetite, and the slag contains high-grade titanium, which is beneficial to the recovery and utilization of titanium. It is considered to be an effective method to solve the comprehensive recovery of iron, vanadium and titanium in vanadium-titanium magnetite, and has advantages in process, energy consumption and environmental protection. It is the development trend of clean and efficient utilization of vanadium-titanium magnetite resources.

[0004] The electric furnace smelting technology at the rear end of the hydrogen-based shaft furnace pre-reduction-electric furnace smelting process is difficult in the hydrogen-based shaft furnace reduction process. Compared with the traditional blast furnace ironmaking, the hydrogen-based shaft furnace process requires higher iron grade of oxidized pellets, and is more demanding on the metallurgical properties of the pellets, such as reducibility, low-temperature reduction pulverization performance, reduction expansion performance and reduction bonding.

[0005] The hydrogen-based shaft furnace pre-reduction-electric furnace smelting of vanadium-titanium magnetite can realize efficient utilization of resources, but the low-temperature reduction pulverization of vanadium-titanium magnetite pellets restricts the industrial application of the non-blast furnace method. The reduction pulverization problem will cause the strength of vanadium-titanium magnetite pellets to decrease and form a large amount of powder, which will reduce the permeability of the gas-based shaft furnace and increase the amount of dust, and in severe cases, it will affect the normal operation of the gas-based shaft furnace. Therefore, developing a new method for hydrogen-rich reduction of vanadium-titanium magnetite pellets and reducing the low-temperature reduction pulverization rate of vanadium-titanium magnetite pellets in the hydrogen-based shaft furnace pre-reduction process is a key link to realize the comprehensive utilization of vanadium-titanium magnetite resources. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, which aims to solve the problem of serious pulverization of vanadium-titanium magnetite pellets in the existing hydrogen-based shaft furnace pre-reduction technology.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0008] The present application provides a method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, which comprises:

[0009] First-stage reduction: the vanadium-titanium magnetite oxidized pellets are placed in a hydrogen-based shaft furnace for first-stage reduction, the reduction gas composition is H2 and N2 mixed gas, the reduction temperature is 400-700℃, and the reduction time is 30-60min;

[0010] Second-stage reduction: the pellets after the first-stage reduction are subjected to second-stage reduction, the second-stage reduction is high-temperature reduction under a hydrogen-rich mixed gas atmosphere, the reduction temperature is 900-1050℃, and the reduction time is 60-90min;

[0011] After the reduction product is treated, the vanadium-titanium magnetite metallized pellet product is obtained, and the performance index is: pellet strength greater than 800N / P, low-temperature reduction pulverization index RDI +6.3mm >90%, and metallization rate ≥94%.

[0012] The first-stage reduction is used to pretreat the vanadium-titanium magnetite pellets, thereby improving the low-temperature reduction pulverization phenomenon of the vanadium-titanium magnetite oxidized pellets.

[0013] As a further improvement of the above scheme, the vanadium-titanium magnetite has a total iron content of not less than 50% by mass, a TiO2 content of 5-12%, and a V2O5 content of less than 1%.

[0014] As a further improvement of the above scheme, the average compressive strength of the vanadium-titanium magnetite oxidized pellets is 2000-2200N / P.

[0015] As a further improvement of the above scheme, in the first-stage reduction process, the reduction gas composition is H2 and N2 mixed gas, and the volume of the reduction gas satisfies: H2 ratio is 40%-70%.

[0016] As a further improvement of the above scheme, in the second-stage reduction process, the reduction gas composition is H2, CO, CO2 and N2, and the volume of the reduction gas satisfies: H2+CO≥85%, H2 / (H2+CO)≥0.75, and 12%≥N2≥6%.

[0017] As a further improvement of the above scheme, the reduction product treatment includes: after the second-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out to obtain the vanadium-titanium magnetite metallized pellets.

[0018] The principle of the present application: the fundamental reason for the reduction pulverization problem of vanadium-titanium magnetite pellets is the expansion stress caused by the transformation of hematite phase to magnetite phase during the reduction process, which leads to the destruction of pellet structure and the reduction of pellet strength; the existing technical methods all use H2-CO mixed reducing atmosphere for the reduction of vanadium-titanium magnetite, and due to the different reduction rates of H2 and CO for hematite, the stress suffered by the pellets during the reduction process is uneven, which further aggravates the pellet pulverization; meanwhile, the carbon deposition phenomenon in the low-temperature reduction process of carbon monoxide also leads to the destruction of pellet structure.

[0019] Compared with the prior art, the present application has the beneficial technical effects of:

[0020] The present application adopts a two-stage reduction method, wherein the first stage reduction is a pretreatment of vanadium-titanium magnetite pellets under the reduction condition of low-temperature pure hydrogen, which effectively suppresses the low-temperature hydrogen-rich reduction pulverization behavior of vanadium-titanium magnetite pellets and reduces the reduction pulverization rate; the second stage reduction is a high-temperature reduction under a hydrogen-rich atmosphere, and by controlling the high H2 ratio in the reduction atmosphere, the reduction rate of iron oxides is accelerated, the metallization rate of the pellets is improved, and the vanadium-titanium magnetite metallized pellet product meets the requirements of the international mainstream gas-based shaft furnace technology.

[0021] In summary, the present application solves the problem of reduction pulverization in the hydrogen-rich reduction process of vanadium-titanium magnetite pellets. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application is a process flow diagram for improving the hydrogen-rich reduction pulverization of vanadium-titanium magnetite pellets. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0024] If a specific technique or condition is not specified in the embodiments, it is carried out according to the technique or condition described in the literature in the art or according to the product instruction. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be obtained by market purchase. In the following examples, unless otherwise specified, "%" refers to the percentage by weight.

[0025] The typical chemical composition of the vanadium-titanium magnetite concentrate used in the examples and comparative examples of the present application is shown in Table 1, and the average compressive strength of the vanadium-titanium magnetite oxide pellets used in the present application is 2081 N / P.

[0026] Table 1 Main chemical composition of vanadium-titanium magnetite, wt%

[0027]

[0028] Example 1

[0029] A method for improving the hydrogen-rich reduction pulverization of vanadium-titanium magnetite pellets, as shown in the process flow Figure 1 The vanadium-titanium magnetite oxidized pellets are directly placed in a hydrogen-rich shaft furnace for one-stage reduction, and the reduction conditions for one-stage reduction are: a reduction temperature of 500°C, a reduction time of 30 min, and a reduction atmosphere of a mixed gas of 50% H2 and 50% N2.

[0030] The one-stage reduced vanadium-titanium magnetite reduction pellets are subjected to two-stage reduction, and the reduction temperature for two-stage reduction is 950°C, the reduction time is 90 min, and the reduction atmosphere is H2 with a proportion of 65%, CO with a proportion of 20%, CO2 with a proportion of 5%, and N2 with a proportion of 10%.

[0031] After the two-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out, and the main technical indexes of the obtained vanadium-titanium magnetite metallized pellets are: a pellet strength of 837 N / P, a reduction pulverization index RDI +6.3mm (the mass fraction of the sample greater than 6.3 mm after reduction) of 95.37%, and a metallization rate of 94.31%.

[0032] Example 2

[0033] A method for improving the hydrogen-rich reduction pulverization of vanadium-titanium magnetite pellets, the vanadium-titanium magnetite oxidized pellets are directly placed in a hydrogen-rich shaft furnace for one-stage reduction, and the reduction conditions for one-stage reduction are: a reduction temperature of 500°C, a reduction time of 30 min, and a reduction atmosphere of a mixed gas of 40% H2 and 60% N2.

[0034] The one-stage reduced vanadium-titanium magnetite reduction pellets are subjected to two-stage reduction, and the reduction temperature for two-stage reduction is 950°C, the reduction time is 90 min, and the reduction atmosphere is H2 with a proportion of 80%, CO with a proportion of 10%, CO2 with a proportion of 5%, and N2 with a proportion of 5%.

[0035] After the two-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out, and the main technical indexes of the obtained vanadium-titanium magnetite metallized pellets are: a pellet strength of 957 N / P, a reduction pulverization index RDI +6.3mm (the mass fraction of the sample greater than 6.3 mm after reduction) of 91.34%, and a metallization rate of 95.27%.

[0036] Example 3

[0037] A method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, wherein vanadium-titanium magnetite oxidized pellets are directly placed in a hydrogen-rich shaft furnace for one-stage reduction, and the one-stage reduction conditions are: a reduction temperature of 500 DEG C, a reduction time of 30 min, and a reduction atmosphere of a mixed gas of 70% H2 and 30% N2;

[0038] The one-stage reduced vanadium-titanium magnetite reduction pellets are subjected to two-stage reduction, the two-stage reduction temperature is 950 DEG C, the reduction time is 120 min, and the reduction atmosphere is H2 with a proportion of 65%, CO with a proportion of 20%, CO2 with a proportion of 5%, and N2 with a proportion of 10%;

[0039] After the two-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out, the main technical indexes of the obtained vanadium-titanium magnetite metallized pellets are: a pellet strength of 1036 N / P, a reduction pulverization index RDI +6.3mm (the mass fraction of the sample greater than 6.3 mm after reduction) of 98.64%, and a metallization rate of 96.26%.

[0040] Example 4

[0041] A method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, wherein vanadium-titanium magnetite oxidized pellets are directly placed in a hydrogen-rich shaft furnace for one-stage reduction, and the one-stage reduction conditions are: a reduction temperature of 400 DEG C, a reduction time of 60 min, and a reduction atmosphere of a mixed gas of 40% H2 and 60% N2;

[0042] The one-stage reduced vanadium-titanium magnetite reduction pellets are subjected to two-stage reduction, the two-stage reduction temperature is 1050 DEG C, the reduction time is 60 min, and the reduction atmosphere is H2 with a proportion of 75%, CO with a proportion of 15%, CO2 with a proportion of 4%, and N2 with a proportion of 6%;

[0043] After the two-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out, the main technical indexes of the obtained vanadium-titanium magnetite metallized pellets are: a pellet strength of 1127 N / P, a reduction pulverization index RDI +6.3mm (the mass fraction of the sample greater than 6.3 mm after reduction) of 96.24%, and a metallization rate of 97.87%.

[0044] Example 5

[0045] A method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, wherein vanadium-titanium magnetite oxidized pellets are directly placed in a hydrogen-rich shaft furnace for one-stage reduction, and the one-stage reduction conditions are: a reduction temperature of 700 DEG C, a reduction time of 30 min, and a reduction atmosphere of a mixed gas of 70% H2 and 30% N2;

[0046] A section of the reduced vanadium-titanium magnetite reduced pellet is subjected to two-stage reduction, the two-stage reduction temperature is 900℃, the reduction time is 90min, the reduction atmosphere is H2 ratio of 75%, CO ratio of 15%, CO2 ratio of 4%, N2 ratio of 6%;

[0047] After the two-stage reduction, N2 is introduced to cool to room temperature, and the reduction product is taken out, the main technical indexes of the obtained vanadium-titanium magnetite metallized pellet are: pellet strength is 932N / P, reduction disintegration index RDI +6.3mm (reduced sample mass fraction greater than 6.3mm) is 98.62%, and the metallization rate is 94.71%.

[0048] Comparative Example 1

[0049] The difference from Example 1 is that no one-stage pre-reduction is performed, and the vanadium-titanium magnetite oxidized pellet is directly placed in a hydrogen-rich shaft furnace for reduction, the reduction temperature is 950℃, the reduction time is 120min, the reduction atmosphere is H2 ratio of 65%, CO ratio of 20%, CO2 ratio of 5%, N2 ratio of 10%; the main technical indexes of the obtained vanadium-titanium magnetite metallized pellet are: pellet strength is 694.35N / P, reduction disintegration index RDI +6.3mm (reduced sample mass fraction greater than 6.3mm) is 78.61%, and the metallization rate is 94.26%.

[0050] Comparative Example 2

[0051] The difference from Example 1 is that no one-stage pre-reduction is performed, and the vanadium-titanium magnetite oxidized pellet is directly placed in a hydrogen-rich shaft furnace for reduction, the reduction temperature is 950℃, the reduction time is 120min, the reduction atmosphere is H2 ratio of 45%, CO ratio of 40%, CO2 ratio of 5%, N2 ratio of 10%; the main technical indexes of the obtained vanadium-titanium magnetite metallized pellet are: pellet strength is 557.19N / P, reduction disintegration index RDI +6.3mm (reduced sample mass fraction greater than 6.3mm) is 70.31%, and the metallization rate is 91.29%.

[0052] Comparative Example 3

[0053] The difference from Example 1 is that no one-stage pre-reduction is performed, and the vanadium-titanium magnetite oxidized pellet is directly placed in a hydrogen-rich shaft furnace for reduction, the reduction temperature is 950℃, the reduction time is 120min, the reduction atmosphere is H2 ratio of 40%, CO ratio of 20%, CO2 ratio of 20%, N2 ratio of 20%; the main technical indexes of the obtained vanadium-titanium magnetite metallized pellet are: pellet strength is 747.61N / P, reduction disintegration index RDI +6.3mmThe mass fraction of the sample (greater than 6.3 mm after reduction) was 85.31%, and the metallization rate was 86.29%.

[0054] Although the embodiments of the present application have been shown and described above, it should be understood by those skilled in the art that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments without departing from the principles and spirit of the present application within the scope of the present application.

Claims

1. A method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets, characterized in that, include: First-stage reduction: Vanadium-titanium magnetite oxide pellets are placed in a hydrogen-based vertical shaft furnace for first-stage reduction. The reducing gas composition is a mixture of H2 and N2, the reduction temperature is 400-700℃, and the reduction time is 30-60 min. Two-stage reduction: The pellets after the first-stage reduction undergo a second-stage reduction. The second-stage reduction is carried out at high temperature in a hydrogen-rich mixed atmosphere, with a reduction temperature of 900-1050℃ and a reduction time of 60-90min. After processing the reduction product, vanadium-titanium magnetite metallized pellets were obtained with the following performance indicators: pellet strength greater than 800 N / P, and low-temperature reduction pulverization index (RDI). +6.3mm >90%, metallization rate ≥94%.

2. The method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets according to claim 1, characterized in that, The vanadium-titanium magnetite, by mass fraction, has a total iron content of not less than 50%, a TiO2 content of 5-12%, and a V2O5 content of less than 1%.

3. The method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets according to claim 1, characterized in that, The average compressive strength of the vanadium-titanium magnetite oxide pellets is 2000–2200 N / P.

4. The method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets according to claim 1, characterized in that, During the reduction process, the reducing gas is a mixture of H2 and N2, and the volume of the reducing gas satisfies the following condition: the H2 ratio is 40% to 70%.

5. The method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets according to claim 1, characterized in that, In the two-stage reduction process, the reducing gas composition is H2, CO, CO2 and N2, and the reducing gas volume satisfies: H2+CO≥85%, H2 / (H2+CO)≥0.75, 12%≥N2≥6%.

6. The method for improving the hydrogen-rich reduction and pulverization of vanadium-titanium magnetite pellets according to claim 1, characterized in that, The reduction product processing includes: after the two-stage reduction is completed, N2 is introduced to cool to room temperature, and the reduction product is taken out to obtain vanadium-titanium magnetite metallized pellets.

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