Method for reducing Ti content of molten iron by using return mine powder

Abstract

The invention relates to a method for reducing the Ti content of molten iron by using return mine powder, which comprises the following steps of: before Ti molten iron enters a furnace, adding the return mine powder with strong oxidizing property, enabling the Ti element in the iron oxide water to enter molten iron slag in the form of TiO2, and removing the molten iron slag by using a slag conveyor to achieve the purpose of reducing the Ti content of the molten iron, so that the subsequent smelting process can be stably carried out; the iron oxide-containing material is adopted for titanium removal, energy consumption is not additionally increased, the method is suitable for an existing steelmaking process, a production line does not need to be additionally transformed, and large-scale industrial application is easy; the iron oxide-containing material is used for removing titanium, so that the quality of iron can be better maintained, the temperature of molten iron can be properly reduced by adding the return mine powder, the smelting process can be stabilized, the converter operation can be optimized, and the lining loss can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of converter smelting, and particularly to a method for reducing the Ti content of hot metal using return fines. Background Art

[0002] During the converter steelmaking process, a high titanium (Ti) content in hot metal will bring a series of adverse effects to the smelting process and the quality of molten steel. When the Ti content in hot metal is high, the melting points of calcium compounds (CaO) and silicates (SiO2) in the converter slag will increase, making it difficult for the slag to melt fully, resulting in difficult slag melting. Due to the decrease in the fluidity of the slag, the unreacted CaO and SiO2 in the slag may form high-melting-point solid-phase particles, making the slag in the converter smelting process thick and difficult to remove, thus affecting the refining effect of molten steel. Titanium in hot metal easily reacts with elements such as oxygen, sulfur, and silicon to form stable inclusions such as oxides (TiO2), sulfides (TiS), and silicides (Ti5Si3). These inclusions are difficult to remove and are distributed in the molten steel, which will reduce the plasticity, toughness, and impact properties of the steel, affecting its processing performance. The presence of Ti may lead to difficulties in decarburizing the molten steel, affecting the control of the carbon content of the steel, and further affecting the mechanical properties of the product. After high-Ti hot metal is charged into the furnace, during the high-temperature smelting process in the converter, Ti and its oxide (TiO2) may react with the refractory materials, resulting in the structural damage of the furnace lining bricks and exacerbating the erosion of the furnace lining. Especially in a high-temperature environment, TiO2 has strong permeability and will enter the pores of the furnace lining bricks, causing volume expansion and spalling of the refractory materials, shortening the converter campaign life and increasing the consumption and replacement cost of refractory materials. The Ti element in hot metal is an easily oxidized element. A high Ti content in hot metal will cause the carbon-oxygen reaction to be delayed, making it difficult to add cold materials. The Ti-containing slag has strong foam storage capacity and is prone to slag foaming and foam splashing. Therefore, it is necessary to pretreat the high-Ti hot metal before charging to reduce the Ti content in the hot metal. Summary of the Invention

[0003] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for reducing the Ti content of hot metal using return fines.

[0004] The technical solution adopted by the present invention to solve its technical problems is: A method for reducing the Ti content of hot metal using return fines, comprising the following steps:

[0005] Step S1: Before the high-Ti hot metal is charged into the furnace, add return fines with strong oxidizing properties;

[0006] Step S2: The iron oxide in the cold-pressed pellets reacts with the titanium in the hot metal to form titanium dioxide;

[0007] Step S3: Remove the hot metal slag through a slag skimmer.

[0008] As a further improvement of the present invention: in the step S1, sinter return fines containing Fe2O3 and Fe3O4 are selected, and their particle size is controlled to be 3 - 6 mm.

[0009] As a further improvement of the present invention: in the step S1, the return fines are preheated to 300 °C by the waste heat of the hot metal ladle. Before tapping from the blast furnace, 200 - 300 kg of sinter return fines are added into the hot metal ladle and evenly added within 5 - 10 minutes.

[0010] As a further improvement of the present invention: in the step S1, after adding the return fines with strong oxidation properties, when the hot metal from the blast furnace enters the hot metal ladle, internal mixing and flushing are formed, and Ti fully reacts with FeO and Fe2O3 in the return fines.

[0011] As a further improvement of the present invention: in the step S1, the tapping temperature of the blast furnace is controlled at 1200 - 1300 °C, the temperature of the hot metal ladle is controlled at 600 - 900 °C, and a heat preservation cover is added.

[0012] As a further improvement of the present invention: in the step S1, the total Fe content in the return fines is ≥ 55%, and FeO accounts for 10% - 15%.

[0013] As a further improvement of the present invention: the return fines in the step S1 are prepared by the following steps:

[0014] (1) Determine whether to add return fines according to the silicon content of the hot metal;

[0015] (2) When the silicon content of the hot metal is greater than 0.50%, add 500 - 1000 kg of return fines, and quickly lower the lance position to inhibit the reaction of oxygen with Fe in the hot metal to generate FeO and enter the slag phase. Add 300 kg of slag lime at one time to cause the slag to foam. After the flame of the converter smelting is normal, resume the normal lance position operation;

[0016] When the silicon content of the hot metal is less than 0.50%, no return fines are added in the early stage of smelting. It is necessary to ensure that the slag in the early stage does not foam severely and cause slag overflow and splashing, and the slag thickness line should not exceed the warning line when blowing for 5 - 7 minutes;

[0017] (3) Control the oxygen supply time at 7'00" to 7'30";

[0018] (4) Add the return fines in batches, reduce the Fe element in the slag into the molten steel through the C - O reaction, and at the same time adjust the FeO content of the slag;

[0019] (5) Calculate the addition amount of the return fines according to the heat balance of steelmaking, and at the same time observe the flame temperature and flexibly adjust the addition amount of the return fines to ensure that the molten steel temperature is appropriate, and strive to complete the addition amount of the return fines before 12 minutes of oxygen supply time.

[0020] As a further improvement of the present invention: when the temperature of the molten iron ladle is lower than 600 °C before tapping from the blast furnace, the molten iron ladle is preheated.

[0021] As a further improvement of the present invention: a dynamic monitoring system of the blast furnace molten iron is used to adjust the addition amount of return fines according to the Ti content of the molten iron, and the return fines are evenly distributed and added in the molten iron ladle.

[0022] As a further improvement of the present invention: in step S3, the slag layer is adjusted before slag skimming so that the thickness of the slag layer is maintained in the range of 20 - 50 mm.

[0023] As a further improvement of the present invention: the slag skimming step includes at least two slag skimming operations. The first slag skimming removes most of the TiO2, and the second slag skimming further reduces the TiO2 residue in the molten iron slag.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) High - efficiency titanium removal: The iron oxide in the cold - pressed balls reacts with the titanium in the molten iron to form titanium dioxide, separating the titanium element from the molten iron and entering the slag phase, thus effectively removing titanium. The reduction of titanium content can be achieved in a relatively short time, improving the titanium - removal efficiency.

[0026] (2) Economical and efficient: The cost of return fines is relatively low; compared with other methods, using iron - oxide - containing materials to reduce the titanium content is usually an economical and efficient choice; using iron - oxide - containing materials for titanium removal does not increase additional energy consumption, and can optimize the quality of molten iron without affecting the overall production cost.

[0027] (3) Simple operation: The operation of adding cold - pressed balls into the molten iron is relatively simple and does not require complex equipment or technical support. It is applicable to the existing steel - making process, without the need for additional production - line transformation, and is easy for large - scale industrial application.

[0028] (4) Maintaining the quality of molten iron: Compared with other methods of removing titanium, using iron - oxide - containing materials to remove titanium can better maintain the quality of iron. Because the oxidation properties of titanium and silicon are similar, iron oxide will oxidize and remove titanium and a small amount of silicon in the molten iron without having too much impact on other molten - iron elements. Adding return fines can appropriately reduce the temperature of the molten iron, which helps to stabilize the smelting process, optimize the converter operation, and reduce the lining loss. Detailed implementation manners

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. 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 scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] Unless otherwise specifically stated, the relative arrangements, numerical expressions and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for the sake of convenience of description, technologies, methods and devices known to those of ordinary skill in the relevant fields may not be discussed in detail, but in appropriate circumstances, such technologies, methods and devices should be regarded as part of the authorized specification. In all the examples shown and discussed here, any specific value should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values.

[0032] High titanium content in hot metal increases the melting points of CaO and SiO2 in the converter slag, making it difficult for the slag to melt fully and affecting the slag melting process. Unmelted CaO and SiO2 form high-melting-point solid particles, making the slag thick, less fluid, and difficult to remove, thus affecting the refining effect of molten steel. Titanium easily reacts with elements such as oxygen, sulfur, and silicon to form stable oxides (TiO2), sulfides (TiS), and silicides (Ti5Si3). Inclusions are evenly distributed in the molten steel and difficult to remove, affecting product quality. High Ti content in hot metal delays the carbon-oxygen reaction (C + O2 → CO / CO2), affects the decarburization process of molten steel, affects the addition and dissolution of cold materials, makes the converter smelting operation more complex, reduces production efficiency, and TiO2 has strong permeability at high temperatures, easily enters the pores of refractory bricks, causes volume expansion, leads to spalling of refractory materials, and shortens the furnace life. The reaction of Ti and its oxides with the lining material accelerates the erosion of the converter lining, increases the consumption and replacement cost of refractory materials. The slag formed by high-Ti hot metal has strong foam storage capacity, easily causes slag foaming, and affects the stability of the furnace condition. Excessive foaming of the slag may cause foam splashing, resulting in increased iron loss and affecting the safety and stability of the steelmaking process. The present invention provides a method for reducing the Ti content in hot metal using return fines, which is efficient, economical, simple to operate, and beneficial to maintaining the quality of iron.

[0033] The present invention will be further described in conjunction with embodiments: A method for reducing the Ti content in hot metal using return fines includes the following steps:

[0034] Step S1: Before the Ti-rich hot metal enters the furnace, add return fines with strong oxidizing properties;

[0035] Step S2: The iron oxide in the cold-pressed pellets reacts with the titanium in the hot metal to form titanium dioxide;

[0036] Step S3: Remove the hot metal slag through a slag skimmer.

[0037] Based on the easy oxidizability of Ti element in hot metal, return fines containing Fe2O3 and Fe3O4 are added, and Ti is oxidized to TiO2. The melting point of TiO2 is 1840 °C, higher than the temperature of hot metal. After the oxidation reaction is completed, TiO2 enters the hot metal slag, and TiO2 is removed through a slag skimmer. Before the Ti-rich hot metal enters the furnace, add return fines with strong oxidizing properties, oxidize the Ti element in the hot metal, make it enter the hot metal slag in the form of TiO2, and remove the hot metal slag through a slag skimmer to achieve the purpose of reducing Ti in hot metal, so that the subsequent smelting process can proceed smoothly.

[0038] As an embodiment of the present invention, the return fines in step S1 are prepared by the following steps:

[0039] (1) Determine whether to add return fines according to the silicon content in hot metal;

[0040] (2) When the silicon content in the hot metal is greater than 0.50%, 500 - 1000 kg of return fines is added, and the lance position is quickly lowered to inhibit the reaction of oxygen with Fe in the hot metal to form FeO and enter the slag phase. 300 kg of lime, the slag material, is added at one time to cause the slag to foam. After the flame of the converter smelting is normal, the normal lance position operation is restored;

[0041] When the silicon content in the hot metal is less than 0.50%, return fines are not added in the early stage of smelting. It is necessary to ensure that the slag in the early stage does not foam severely and cause slag overflow and splashing. When blowing for 5 - 7 minutes, the slag thickness line must not exceed the warning line;

[0042] (3) Control the oxygen supply time between 7'00" and 7'30";

[0043] (4) Add return fines in batches. Reduce the Fe element in the slag into the molten steel through the C - O reaction, and at the same time adjust the FeO content in the slag;

[0044] (5) Calculate the addition amount of return fines according to the heat balance of steelmaking. At the same time, observe the flame temperature and flexibly adjust the addition amount of return fines to ensure that the molten steel temperature is appropriate. At the same time, strive to complete the addition amount of return fines 12 minutes before the oxygen supply time.

[0045] Through the real - time monitoring of the silicon content in the hot metal, determine whether to add return fines, making the de - titanium process more targeted, avoiding unnecessary consumption of return fines, and improving resource utilization rate; combined with the heat balance calculation of steelmaking, accurately calculate the addition amount of return fines to avoid over - addition or under - addition and improve resource utilization efficiency; real - time monitor the flame temperature and flexibly adjust the addition amount of return fines to ensure that the molten steel temperature is moderate, reducing smelting abnormalities caused by too high or too low temperature; through accurately controlling the addition amount of return fines, optimizing the slag composition, and adjusting the oxygen supply strategy, make the de - Ti reaction proceed efficiently, while avoiding too fast slag foaming and causing splashing, improving the quality of molten steel, reducing production costs, and improving the stability of converter operation.

[0046] As an embodiment of the present invention, in step S1, select sintered return fines containing Fe2O3 and Fe3O4, and control its particle size at 3 - 6 mm; the return fines are pre - heated to 300 °C by the waste heat of the hot metal ladle. Before the blast furnace taps, 200 - 300 kg of sintered return fines is added into the hot metal ladle and evenly added within 5 - 10 minutes; when the hot metal from the blast furnace enters the hot metal ladle after adding the return fines with strong oxidation properties, internal mixing and flushing are formed, and Ti fully reacts with FeO and Fe2O3 in the return fines; in step S1, control the blast furnace tapping temperature at 1200 - 1300 °C, control the hot metal ladle temperature at 600 - 900 °C, and cover it for heat preservation; in step S1, the total Fe content in the return fines ≥ 55%, and FeO accounts for 10% - 15%.

[0047] Select sinter return fines containing Fe2O3 and Fe3O4 to provide sufficient oxidation ability to ensure that Ti in the hot metal can be fully oxidized to TiO2. Control the particle size of the return fines at 3 - 6 mm to ensure its dispersion in the hot metal, increase the contact area with Ti, promote the Ti removal reaction, and at the same time prevent fine particles from being carried away by the gas flow, reduce losses, and improve resource utilization rate. Preheat the return fines to 300 °C using the waste heat of the hot metal ladle to reduce the temperature shock when the return fines enter the hot metal, increase the oxidation reaction rate, and accelerate the Ti removal process. Before tapping from the blast furnace, add 200 - 300 kg of sinter return fines into the hot metal ladle to ensure an appropriate supply of FeO and Fe2O3 and enable the reaction to proceed fully.

[0048] Utilize the fluidity of the blast furnace hot metal when it enters the hot metal ladle to generate an internal mixing and flushing effect, promote the full reaction of Ti with FeO and Fe2O3, rapidly oxidize Ti to TiO2 and make it enter the slag phase, and improve the Ti removal efficiency.

[0049] The reactions mainly include:

[0050] 2(FeO)+[Ti]=2[Fe]+TiO2

[0051] 2(Fe2O3)+3[Ti]=4[Fe]+3TiO2

[0052] Control the tapping temperature of the blast furnace at 1200 - 1300 °C to ensure that Ti undergoes a rapid oxidation reaction at a sufficiently high temperature and improve the Ti removal efficiency. Control the temperature of the hot metal ladle at 600 - 900 °C and cover it for heat preservation to reduce heat loss, maintain an appropriate reaction temperature, maximize the activity of the return fines, and improve the Ti removal efficiency. The total Fe content of the return fines is ≥ 55%, and FeO accounts for 10% - 15%, ensuring sufficient supply of oxidant, ensuring the full progress of the Ti oxidation reaction, and at the same time reducing iron losses caused by too high FeO content and improving smelting economy. By optimizing the selection, preheating, precise addition, and temperature control of the return fines, this method can efficiently remove Ti from the hot metal, improve the Ti removal efficiency, reduce oxide inclusions, and improve the quality of molten steel. At the same time, this method improves production stability and resource utilization rate without additional equipment investment and has good industrial application value.

[0053] As an embodiment of the present invention, when the temperature of the molten iron ladle is lower than 600°C before tapping from the blast furnace, the molten iron ladle is preheated. When the temperature of the molten iron ladle is lower than 600°C before tapping from the blast furnace, the molten iron ladle is preheated to prevent the rapid temperature drop of the molten iron after it enters the ladle, which affects the oxidation reaction of Ti, and keep the temperature of the molten iron ladle within the range of 600-900°C, which helps to maintain the activity of the returned ore powder, promote the full oxidation of Ti, improve the Ti removal effect. The preheating can also reduce the problem of increased slag viscosity caused by too low temperature, optimize the slag melting process, and improve the quality of molten iron; use the dynamic monitoring system of blast furnace molten iron, adjust the addition amount of returned ore powder according to the Ti content in the molten iron, and evenly distribute and add the returned ore powder in the molten iron ladle, analyze the Ti content in the molten iron in real time, and automatically adjust the addition amount of returned ore powder to ensure the best Ti removal effect. Add the returned ore powder evenly in the molten iron ladle to avoid too high or too low local concentration, ensure sufficient contact between FeO, Fe2O3 and Ti, improve the reaction uniformity, and reduce the waste of returned ore powder; in step S3, the slag layer is adjusted before slag skimming to keep the slag layer thickness within the range of 20-50 mm, ensure that the slag has good fluidity and separation ability, make TiO2 easier to enter the slag phase, and improve the Ti removal efficiency; the slag skimming step includes at least two slag skimming operations. The first slag skimming removes most of the TiO2, and the second slag skimming further reduces the TiO2 residue in the molten iron slag, ensuring more thorough Ti removal, reducing the accumulation of TiO2 in the slag, reducing the adverse impact on the converter operation, and improving the stability of steelmaking.

[0054] The following are the actual application examples of using the method of reducing the Ti content in molten iron with returned ore powder according to the present invention:

[0055] Example 1:

[0056] The Ti content in the blast furnace molten iron is high. The average Ti content in the molten iron of the first five furnaces without adding returned ore powder is 0.142%. Starting from furnace 24103722, 500 kg of returned ore powder is added to each furnace, and slag skimming is carried out 4 times. The Ti content in the molten iron decreases significantly. The average Ti content in the molten iron of the five furnaces after adding returned ore powder is 0.753%. The measured results are as follows:

[0057]

[0058]

[0059] Example 2:

[0060] The Ti content in the blast furnace molten iron is high. The average Ti content in the molten iron of the first five furnaces without adding returned ore powder is 0.153%. Starting from furnace 24103625, 500 kg of returned ore powder is added to each furnace, and slag skimming is carried out 4 times. The Ti content in the molten iron decreases significantly. The average Ti content in the molten iron of the five furnaces after adding returned ore powder is 0.862%. The measured results are as follows:

[0061]

[0062]

[0063] In summary, after reading the present invention document, those of ordinary skill in the art can make various other corresponding transformation schemes without creative mental labor according to the technical solutions and technical concepts of the present invention, and all of them fall within the scope protected by the present invention.

Claims

1. A method for reducing the Ti content in molten iron using return fines, characterized in that, It includes the following steps: Step S1: Before the Ti hot metal enters the furnace, add return fines with strong oxidizing properties. Step S2: The iron oxide in the cold-pressed pellets reacts with titanium in the hot metal to form titanium dioxide. Step S3: Remove the hot metal slag through a slag skimmer.

2. The method for reducing the Ti content in hot metal by using return fines according to claim 1, characterized in that In step S1, select sintered return fines containing Fe2O3 and Fe3O4 and control their particle size within 3 - 6 mm.

3. A method for reducing the Ti content in hot metal using return fines according to claim 2, characterized in that In step S1, the return fines are preheated to 300 °C by the waste heat of the hot metal ladle. Before tapping from the blast furnace, add 200 - 300 kg of sintered return fines into the hot metal ladle and uniformly add them within 5 - 10 minutes.

4. A method for reducing the Ti content in hot metal using return fines according to claim 3, characterized in that, In step S1, after adding the return fines with strong oxidizing properties, an internal mixing impact is formed when the blast furnace hot metal enters the hot metal ladle, and Ti fully reacts with FeO and Fe2O3 in the return fines.

5. A method for reducing the Ti content in hot metal using return fines according to claim 4, characterized in that, In step S1, control the tapping temperature of the blast furnace at 1200 - 1300 °C, control the temperature of the hot metal ladle at 600 - 900 °C, and cover it for heat preservation.

6. A method for reducing the Ti content in hot metal using return fines according to claim 5, characterized in that In step S1, the total Fe content in the return fines is ≥ 55%, and FeO accounts for 10% - 15% of it.

7. A method for reducing the Ti content in hot metal using return fines according to claim 1, characterized in that When the temperature of the hot metal ladle is lower than 600 °C before tapping from the blast furnace, preheat the hot metal ladle.

8. A method for reducing the Ti content in hot metal using return fines according to claim 1, characterized in that Use the dynamic monitoring system of blast furnace hot metal to adjust the addition amount of return fines according to the Ti content in the hot metal and uniformly distribute and add the return fines in the hot metal ladle.

9. A method for reducing the Ti content in hot metal by using return fines according to claim 1, characterized in that, In step S3, adjust the slag layer before slag skimming to keep the slag layer thickness within the range of 20 - 50 mm.

10. A method for reducing the Ti content in hot metal using return fines, characterized in that, The slag skimming step includes at least two slag skimming operations. The first slag skimming removes most of the TiO2, and the second slag skimming further reduces the TiO2 residue in the hot metal slag.

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