Modification utilization method of vanadium-containing steel slag

Abstract

The invention discloses a modification utilization method of vanadium-containing steel slag, and belongs to the technical field of solid waste utilization. The method comprises the following steps: adding a modifier into a vanadium-containing steel slag tank in the slag tapping process of a vanadium blowing smelting converter, and naturally cooling after calcining to obtain Portland cement clinker and vanadium-containing pig iron; the modifier comprises the following components: fluorite, carbon powder, raw limestone and waste glass bottle slag. According to the method disclosed by the invention, the vanadium-containing steel slag is subjected to online modification in the slag tapping process of the vanadium blowing smelting converter, so that the vanadium-containing steel slag can reach the standard of being applied to Portland cement clinker, and meanwhile, vanadium-containing pig iron with high additional value can be obtained in the modification process.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste utilization, and more specifically, relates to a method for modifying and utilizing vanadium-containing steel slag. Background Art

[0002] Solid wastes in the metallurgical industry are mostly blast furnace slag, converter slag, refining slag, casting slag, desulfurization slag, etc. generated in the production process of the steel industry. In the existing industrial production, the annual output of various types of slag has reached an extremely high level, but its comprehensive utilization rate has reached an average of only 30%. The simple treatment and disorderly storage of a large amount of metallurgical slag have had a serious negative impact on the ecological environment and social life. At the same time, the comprehensive utilization of metallurgical slag is limited by technical level, processing conditions, etc., and the utilization rate is relatively low in practice.

[0003] In the long steelmaking process, the process after the molten iron pretreatment process is the converter steelmaking process, which will produce a large amount of steel slag, which is second only to blast furnace slag, but it is difficult to handle and its resource treatment is insufficient. Due to the large fluctuations in the content of these steel slag components, the steel slag powder still has problems such as low early hydration activity and long coagulation time that need to be effectively solved. Therefore, in order to solve the problem of difficult steel slag treatment, how to realize the resource utilization of metallurgical slag and improve the comprehensive utilization rate of metallurgical slag is a key issue that the steel industry urgently needs to solve.

[0004] In recent years, with the development of the new energy industry, there is a strong demand for energy storage materials, among which vanadium flow batteries have become an emerging industry field. The metal vanadium required for the manufacture of vanadium flow batteries is obtained from vanadium-titanium magnetite by pyrometallurgy or hydrometallurgy. When pyrometallurgy is used to smelt vanadium-titanium magnetite, a large amount of vanadium-containing steel slag will be produced, and the high-value and efficient utilization of vanadium-containing steel slag is still at a low-level and extensive stage.

[0005] On the whole, the chemical composition of vanadium-containing steel slag mainly includes CaO, SiO2, Al2O3, Fe2O3, MgO, V2O5 and other small amounts of metal or non-metal compounds such as TiO2, MnO, P2O5, and silicate cement clinker is in the CaO-SiO2-Al2O3-Fe2O3 system, which greatly increases the feasibility of using vanadium-containing steel slag in the cement field. However, the content of CaO and SiO2 is lower than that of silicate cement, which means that the content of calcium silicate in vanadium-containing steel slag is low. At the same time, since the presence of metal oxides such as iron and vanadium is harmful to the activity of silicate cement, it is necessary to reduce its content. It was found that the mineral composition of vanadium-containing steel slag mainly includes dicalcium silicate, tricalcium silicate, a small amount of free calcium oxide, tetracalcium ferroaluminate, and metal oxides such as MgO, CaO and MnO (collectively referred to as RO phase). In addition, the main mineral phases in vanadium-containing steel slag will change with the change of slag alkalinity.

[0006] Therefore, in order to solve the above-mentioned application of vanadium-containing steel slag in the cement field, many cement plants now often use a mixed ratio of raw materials with industrial waste (including steel slag, phosphate slag, tailings) when preparing silicate cement clinker, such as using limestone, clay, quartz sand, alumina and other industrial waste as mixed raw materials for silicate cement clinker.

[0007] After searching, the Chinese patent application number is: CN202310677773.2, and the patent document with the publication date of September 19, 2023 discloses a method for preparing cement clinker using industrial solid waste and steel slag. The Chinese patent application number is: CN202311062561.X, and the patent document with the publication date of December 29, 2023 discloses a method for preparing cement clinker using powdered solid waste and steel slag. The Chinese patent application number is: CN202311870001.7, and the patent document with the publication date of December 29, 2023 discloses a cement clinker based on composite tailings and steel slag and a preparation method thereof.

[0008] The above three patents all start from the perspective of raw materials, and by replacing the original materials for preparing cement clinker, they reduce the difficulty of utilization, reduce the production cost of cement clinker and the clinker burning temperature, and reduce the technical effect of carbon emissions. But fundamentally, the basic raw material they use is ordinary steel slag, which is still far behind the vanadium-containing steel slag described in the present invention in terms of raw material composition, and there is no mention of how to treat non-ferrous metal oxides such as vanadium and titanium. In addition, the above existing invention methods are only based on the perspective of resource utilization and raw material configuration, and because converter steel slag has low activity, excessive total iron content, and excessive alkalinity, if it is used as the main raw material for cement clinker, the quality of the finished product will be reduced. Therefore, when preparing silicate cement clinker, they often only use steel slag as a small part of the raw materials used, and cannot fully utilize steel slag. This makes it difficult for steel slag to achieve a high-value, fully quantitative utilization efficiency as a solid waste resource. Summary of the invention

[0009] 1. Problems to be solved

[0010] Aiming at the problem that the existing vanadium-containing steel slag cannot be directly used as the raw material for preparing silicate cement clinker due to its low activity, too high iron and vanadium oxide content, too high alkalinity and other problems, or can only be used as a small part of the raw material, and the vanadium-containing steel slag cannot be fully utilized to prepare silicate cement clinker, the present invention provides a method for modifying and utilizing vanadium-containing steel slag, by online modifying the vanadium-containing steel slag during the slagging process of a vanadium blowing smelting converter, so that it can meet the standard for application to silicate cement clinker, and at the same time, high value-added vanadium-containing pig iron can be obtained in the modification process.

[0011] 2. Technical solution

[0012] To solve the above problems, the present invention adopts the following technical solutions.

[0013] A method for modifying and utilizing vanadium-containing steel slag, during the slag discharge process of a vanadium blowing smelting converter, a modifier is added to a vanadium-containing steel slag tank, and after calcination, the slag is naturally cooled to obtain silicate cement clinker and vanadium-containing pig iron; the components of the modifier include fluorite, carbon powder, quicklime stone and waste glass bottle slag.

[0014] As a further improvement of the technical solution, the raw materials of the modifier are crushed into particles with a particle size of less than 3 mm before being added, and are naturally dried, or dried at a temperature of 50° C. to 120° C. for 6 to 12 hours.

[0015] As a further improvement of the technical solution, the order of adding the modifier is: first add carbon powder to react until the iron oxide content in the slag is 3% to 5% and the vanadium oxide content is less than 0.05%, then add fluorite, and finally add quicklime and waste glass bottle slag.

[0016] As a further improvement of the technical solution, the main components and mass percentages of the waste glass bottle slag are: SiO2 is 73.93%, Al2O3 is 4.13%, CaO is 10.02%, and the sum of the mass percentages of Na2O and K2O is 11.31%.

[0017] As a further improvement of the technical solution, the weight of the added waste glass bottle slag accounts for 11.5% to 16.4% of the weight of the slag.

[0018] As a further improvement of the technical solution, the fixed carbon content of the added carbon powder is greater than 90%, and the weight of the added carbon powder accounts for 3.4% to 3.9% of the weight of the slag.

[0019] As a further improvement of the technical solution, the main components and mass percentages of the fluorite are: CaF2 is 89.5%, SiO2 is 0.7%, CaCO3 is 1.2%, and NaCl2 is 1%.

[0020] As a further improvement of the technical solution, the weight of the added fluorite accounts for 3.0% to 3.8% of the weight of the slag.

[0021] As a further improvement of the technical solution, the weight of the added quicklime stone accounts for 25% to 42% of the weight of the slag.

[0022] As a further improvement of the technical solution, during the modification process, the slag temperature is maintained between 1350°C and 1500°C.

[0023] 3. Beneficial effects

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention discloses a modification and utilization method of vanadium-containing steel slag. In the process of slag tapping of a vanadium-blowing smelting converter, the high temperature characteristics of the slag tapping of the vanadium-blowing smelting converter and the raw material conditions are utilized to perform online modification treatment on the slag, so that the slag can reach the standard for application in silicate cement clinker, and the residual calorific value is fully utilized. Meanwhile, high value-added vanadium-containing pig iron can be obtained in the modification process. The comprehensive energy consumption and production cost per unit product of silicate cement clinker and vanadium-containing pig iron are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the process of adding and modifying vanadium-containing steel slag to prepare silicate cement clinker and vanadium-containing pig iron for high-value and high-efficiency modification;

[0027] Figure 2 This is a schematic diagram of the process of blowing vanadium-enriched slag and tapping semi-steel in a vanadium-blowing smelting converter;

[0028] Figure 3 This is a schematic diagram of the heating electrode function in a vanadium-containing slag tank;

[0029] Figure 4 In order to add anion F -1 (Adding CaF2) The relationship between the free calcium oxide content and temperature;

[0030] Figure 5 This is the effect of calcination temperature on the reduction efficiency of iron and vanadium oxides in vanadium-containing steel slag under the conditions of carbon powder content of 3.5% and calcination time of 50 min. DETAILED DESCRIPTION

[0031] Exemplary embodiments of the present invention are described in detail below. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments may be implemented and various changes may be made to the present invention without departing from the spirit and scope of the present invention. The more detailed description of the embodiments of the present invention below is not intended to limit the scope of the claimed invention, but is merely for illustration and does not limit the description of the features and characteristics of the present invention, in order to propose the best mode for performing the present invention, and is sufficient to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0032] Example 1

[0033] A modification and utilization method of vanadium-containing steel slag, by modifying the vanadium-containing steel slag in the slag-discharging process, the iron oxide content in the vanadium-containing steel slag is reduced to 3% to 5%, the vanadium oxide content is less than 0.05%, the content of the main components such as CaO, Al2O3, SiO2 is basically consistent with that of silicate cement clinker, and the quaternary basicity (ratio of CaO+MgO to Al2O3+SiO2) of the slag after the modification reaction is controlled at 2.4 to 2.8. The main minerals finally formed by the modified slag are C3S (tricalcium silicate), C2S (dicalcium silicate), C3A (tricalcium aluminate), C4AF (tetracalcium aluminoferrite solid solution), wherein the C3S content is greater than 60%, and the total amount of C3S and C2S is more than 75%. The specific process and technical effect are described in detail below.

[0034] The specific process of the method is to add a modifier to the vanadium-containing steel slag tank during the slag discharge process of the vanadium blowing smelting converter, and naturally cool it after calcination to obtain silicate cement clinker and vanadium-containing pig iron; the components of the modifier include fluorite, carbon powder, quicklime and waste glass bottle slag.

[0035] Before adding the raw materials of the modifier, they must be crushed into particles with a particle size of less than 3 mm and dried naturally or dried at a temperature of 50°C to 120°C for 6 to 12 hours.

[0036] like Figure 1 As shown, the order of adding the modifier is: first add carbon powder to fully reduce the iron oxide and vanadium oxide in the vanadium-containing steel slag, until the iron oxide content in the slag is 3% to 5% and the vanadium oxide content is less than 0.05%, then add fluorite to adjust the flow characteristics and activity of the steel slag, and finally add quicklime and waste glass bottle slag to adjust the steel slag composition and quaternary basicity.

[0037] Among them, the main components and mass percentages of waste glass bottle slag are: SiO2 is 73.93%, Al2O3 is 4.13%, CaO is 10.02%, and the sum of the mass percentages of Na2O and K2O is 11.31%. The weight of the added waste glass bottle slag accounts for 11.5% to 16.4% of the weight of the slag. The main components and mass percentages of fluorite are: CaF2 is 89.5%, SiO2 is 0.7%, CaCO3 is 1.2%, and NaCl2 is 1%. The weight of the added fluorite accounts for 3.0% to 3.8% of the weight of the slag. The fixed carbon content of the added carbon powder is greater than 90%, and the weight of the added carbon powder accounts for 3.4% to 3.9% of the weight of the slag. The weight of the added quicklime accounts for 25% to 42% of the weight of the slag. During the modification process, the slag temperature is maintained between 1350℃ and 1500℃.

[0038] The technical principle and effect of this embodiment are analyzed below to further illustrate the technical effect of this embodiment.

[0039] Since the vanadium smelting converter has a V2O5 content of up to 12-17% after multiple vanadium slag enrichment, this provides good raw material conditions for direct reduction and vanadium extraction of vanadium-containing steel slag. At the same time, the vanadium-containing steel slag also contains rich CaO, SiO2, Al2O3, Fe2O3 and MgO resources, which have the raw material conditions for modified preparation of cement clinker. However, it can also be seen that the above raw material conditions themselves are quite different from ordinary steel slag, so the known technical measures cannot achieve the technical goal of obtaining silicate cement clinker and vanadium-containing pig iron at the same time.

[0040] Therefore, this embodiment utilizes the high temperature characteristics of the slag after the vanadium blowing smelting converter and the raw material conditions to perform online modification treatment on it, so as to fully utilize the residual calorific value and reduce the comprehensive energy consumption and production cost of silicate cement clinker and vanadium-containing pig iron per unit product. During the treatment process, this embodiment prevents the temperature from dropping during the slag modification process by inserting heating electrodes in the slag pot, thereby ensuring the continuity and smooth progress of the vanadium-containing slag modification process. The process flow of steel tapping, slag tapping and heating electrodes in the vanadium blowing smelting converter is as follows: Figure 2 and Figure 3 shown.

[0041] Since Fe2O3 can be used as a flux in silicate cement clinker, its proper presence can reduce the liquid phase formation temperature, reduce the liquid phase viscosity, and promote the formation of C3S in the clinker. Therefore, in this embodiment, 3.4% to 3.9% of carbon powder is added to reduce the total iron content in the steel slag and maintain it at 3% to 5%. At the same time, the addition of carbon powder can directly reduce vanadium in vanadium-containing steel slag, and control the vanadium oxide content in the vanadium-containing steel slag to less than 0.05%. At this time, the metallic iron and metallic vanadium reduced by carbon powder under high temperature will melt and combine to form vanadium-containing pig iron (FeV), which will gather and sink to the bottom of the slag tank. The specific chemical reactions that occur in this process are as follows:

[0042] Fe2O3+3C=2Fe↓+3CO↑;

[0043] V2O5+5C=2V↓+5CO↑;

[0044] Fe+V=FeV.

[0045] Since the slag after chemical modification has the problem of low activity, and the viscosity of the slag is very large during the converter slag discharge process, it is not conducive to the full mixing and reaction of the raw materials. Adding CaF2 can act as a flux and well change the flow characteristics of steel slag and increase the activity of steel slag. In addition, when the ingredients are improperly mixed or the calcination is poor, the cement clinker will have calcium oxide (f-CaO) that is not absorbed and exists in a free state. At the firing temperature, the structure of overburned free calcium oxide is relatively dense, and the hydration is very slow. Usually, the reaction is more obvious after adding water for 3 days. When free calcium oxide is hydrated to form calcium hydroxide, the volume expands by 97.9%, causing local expansion stress inside the hardened cement stone. Therefore, with the increase of free calcium content, the first is the decrease of tensile and flexural strength, and then the strength shrinks after a few days, and even causes poor stability in severe cases. Deformation or cracking of cement products leads to the destruction of cement paste.

[0046] Therefore, the content of free calcium oxide should be strictly controlled. Figure 4 It can be seen that under the same conditions, the increase in temperature can effectively make C2S absorb free CaO to generate C3S, thereby reducing the content of f-CaO. -1 After that, the content of free calcium oxide shows a greater downward trend with the increase of temperature. Therefore, in this embodiment, by adding 3.0% to 3.8% fluorite and controlling the temperature to be greater than 1350° C., the content of free calcium oxide is reduced to less than 2%.

[0047] When cement clinker is formed, tricalcium silicate (C3S) is the last of the four minerals (C3S, C2S, C3A, C4AF) to be formed. Usually at high temperatures, calcium oxide and silicon oxide first react to form dicalcium silicate, and then calcium oxide and dicalcium silicate react to form tricalcium silicate. The reaction formula is as follows:

[0048] 2CaO+SiO2=2CaO·SiO2;

[0049] 2CaO·SiO2+CaO=3CaO·SiO2;

[0050] If there is no liquid phase, in the CaO-SiO2 binary system, when the tricalcium silicate single mineral is synthesized by solid phase reaction, it can be quickly formed in just a few minutes at 1800℃; after heating at 1650℃ for 1 hour, tricalcium silicate is basically formed, and the free calcium is about 1% at this time; after heating at 1450℃ for 1 hour, only a small amount of C3S crystals are generated, and most of them are dicalcium silicate and calcium oxide. However, if there is enough flux (liquid phase), at 1250-1450℃, C3S can absorb CaO in the liquid phase and form tricalcium silicate relatively quickly.

[0051] Therefore, in this embodiment, according to the composition of vanadium-containing steel slag and the components of silicate cement clinker, the Ca-containing raw material is the main added substance (mainly CaO, supplemented by CaF2), and the secondary added substance is SiO2 (glass slag), both of which can be used as flux to increase the liquid phase.

[0052] Alkali oxides can reduce the temperature at which the clinker liquid phase appears and reduce the viscosity of the liquid phase, and act as mineralizers (mainly referring to potassium and sodium). When the alkali content is low, it can promote C2S to absorb CaO to generate C3S, and further reduce f-CaO. In this embodiment, the main component calcium oxide is an alkaline flux, and fluorite is a neutral flux, but it contains 1% NaCl2. Although silicon dioxide is an acidic flux, its content is far less than the sum of calcium oxide and CaF2; in addition, since vanadium-containing steel slag contains a certain amount of MgO and MnO, it itself shows a weak alkalinity, which will cause Al2O3 to dissociate. At this time, the liquid phase viscosity will show a downward trend, and the ion mobility performance will continue to increase under this trend, promoting the generation of C3S.

[0053] In this example, laboratory experiments were conducted to investigate the effect of calcination temperature on the reduction efficiency of iron and vanadium oxides in vanadium-containing steel slag when the carbon powder content was 3.5% and the calcination time was 50 min. Figure 5 It can be seen from the data that when the temperature is greater than 1350℃, the reduction rate of iron in steel slag is about 92%, and the reduction rate of vanadium is about 90%. In addition, since C3S is the last substance generated and is the main substance of cement clinker. Figure 4 It can be seen that a high temperature environment is conducive to reducing the formation of f-CaO and increasing the formation of C3S. When CaF2 is added, when the temperature of the vanadium-containing steel slag is greater than 1350°C, the content of free calcium oxide is reduced to less than 2%. Therefore, controlling the temperature of the slag to be greater than 1350°C is conducive to the efficient reduction of iron and vanadium oxides in the slag, but too high a temperature will also increase the smelting cost of the heating electrode, thereby reducing the application economy of this embodiment. Therefore, the slag modification temperature of this embodiment should be controlled at 1350°C to 1500°C.

[0054] In summary, the modification and utilization method of vanadium-containing steel slag in this embodiment is to modify the vanadium-containing steel slag online during the slag discharge process of the vanadium blowing smelting converter so that it can meet the standards for application in silicate cement clinker, and at the same time, high value-added vanadium-containing pig iron can be obtained during the modification process.

[0055] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A method for modifying and utilizing vanadium-containing steel slag, characterized in that: During the slag discharge process of the vanadium blowing smelting converter, a modifier is added to the vanadium-containing steel slag tank, and after calcination, the slag is naturally cooled to obtain silicate cement clinker and vanadium-containing pig iron; the components of the modifier include fluorite, carbon powder, quicklime and waste glass bottle slag.

2. The method for modifying and utilizing vanadium-containing steel slag according to claim 1, characterized in that: Before adding the raw materials of the modifier, they are crushed into particles with a particle size of less than 3 mm, and then dried naturally or dried at a temperature of 50° C. to 120° C. for 6 to 12 hours.

3. The method for modifying and utilizing vanadium-containing steel slag according to claim 1, characterized in that: The order of adding the modifier is: first add carbon powder to react until the iron oxide content in the slag is 3% to 5% and the vanadium oxide content is less than 0.05%, then add fluorite, and finally add quicklime and waste glass bottle slag.

4. The method for modifying and utilizing vanadium-containing steel slag according to claim 3, characterized in that: The main components and mass percentages of the waste glass bottle slag are: SiO2 is 73.93%, Al2O3 is 4.13%, CaO is 10.02%, and the sum of the mass percentages of Na2O and K2O is 11.31%.

5. The method for modifying and utilizing vanadium-containing steel slag according to claim 4, characterized in that: The weight of the added waste glass bottle slag accounts for 11.5% to 16.4% of the weight of the slag.

6. The method for modifying and utilizing vanadium-containing steel slag according to claim 3, characterized in that: The fixed carbon content of the added carbon powder is greater than 90%, and the weight of the added carbon powder accounts for 3.4% to 3.9% of the weight of the slag.

7. The method for modifying and utilizing vanadium-containing steel slag according to claim 3, characterized in that: The main components and mass percentages of the fluorite are: CaF2 is 89.5%, SiO2 is 0.7%, CaCO3 is 1.2%, and NaCl2 is 1%. The weight of the added fluorite accounts for 3.0% to 3.8% of the weight of the slag.

8. The method for modifying and utilizing vanadium-containing steel slag according to claim 7, characterized in that: The weight of the added fluorite accounts for 3.0% to 3.8% of the weight of the slag.

9. The method for modifying and utilizing vanadium-containing steel slag according to claim 3, characterized in that: The weight of the added quicklime stone accounts for 25% to 42% of the weight of the slag.

10. A method for modifying and utilizing vanadium-containing steel slag according to any one of claims 1 to 9, characterized in that: During the modification process, the slag temperature is maintained between 1350°C and 1500°C.

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