Crude refining apparatus, and direct steelmaking system and method using said apparatus

Abstract

A crude refining apparatus, and a direct steelmaking system and method using said apparatus. The crude refining apparatus comprises a first smelting zone and a second smelting zone which are directly connected. The direct steelmaking system comprises a direct reduction apparatus, an intermediate storage bin and conveying system, a crude refining apparatus, and a refining apparatus. The direct steelmaking method comprises adding metallized pellets obtained through reduction into a direct reduction apparatus in a first smelting zone for heating and melting, obtaining molten product slag and molten iron, and periodically discharging the slag by means of a slag outlet; the molten product molten iron naturally flowing to a second smelting zone by gravity for decarbonization, dephosphorization, and desulfurization refining, thereby obtaining crude molten steel; and adding the crude molten steel to a refining apparatus for refining to obtain qualified molten steel. The steelmaking system can achieve the direct production of molten steel from solid iron-containing raw materials by means of a single smelting device, without the need for an intermediate molten iron ladle lifting and transfer stage, improving metal recovery rate, reducing energy loss, lowering production costs, reducing carbon emissions, and minimizing pollution.

Description

Roughing device, direct steelmaking system and method using the same Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and relates to a roughing device, a direct steelmaking system and a method using the device. Background Art

[0002] As achieving carbon neutrality becomes a global consensus, green, low-carbon innovation has become a trend in the transformation and upgrading of China's steel industry. Currently, the downstream steel industry has begun to consider the carbon emission intensity (carbon footprint) of its products as the sixth key factor, alongside product quality, cost, R&D, delivery, and service. With the recent implementation of the EU Carbon Border Adjustment Mechanism (CBAM), the carbon footprint of steel products has become the basis for levying the EU carbon border adjustment mechanism. This will garner increasing attention in future international trade and global supply chains. Against this backdrop, traditional blast furnace-converter (BF) production processes face significant pressure to reduce carbon emissions.

[0003] To reduce carbon emissions in China's traditional blast furnace-converter (BF) long process, a common technical measure is to increase the scrap ratio in the converter (BOF). It is understood that the maximum scrap ratio in China's BF process can reach around 35%. However, this increased scrap ratio creates insufficient energy in the BF process, necessitating measures such as scrap preheating and BOF coal injection (CPI) to ensure normal BF operation. However, scrap preheating can create environmental issues, and CPI requires retrofitting existing BFs and increases carbon emissions from the BF process. Another measure to reduce carbon emissions is to increase the proportion of short electric furnace (EAF) processes. Traditional EAFs, which use scrap as their primary feedstock, face challenges controlling residual element and nitrogen content in the molten steel. In recent years, the use of hot metal or sponge iron has been widely adopted to address these issues, reducing residual element and nitrogen content in the final EAF molten steel. However, using hot metal in EAFs hinders carbon reduction, and low-grade sponge iron leads to high slag production, long cycle times, and high production costs, hindering compatibility with subsequent processes. To address the various technical problems brought about by electric furnace smelting of low-grade sponge iron, foreign engineering companies have recently launched direct reduction + electric furnace smelting + converter smelting process technologies, such as Primetal's direct reduction + smelter + BOF process, SMS's DRP + OBF + BOF process and Hatch's direct reduction + ESF + BOF process. In essence, the process uses electric furnace smelting to replace blast furnaces to produce molten iron, and then the molten iron is added to the converter to smelt into molten steel. However, since the electric furnace smelting and molten steel roughing are two different smelting devices, namely the smelting furnace and the converter, there are links in the lifting and transfer of molten iron tanks, resulting in high metal recovery and energy loss in the system.

[0004] Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a roughing device, a direct steelmaking system and method using the device, so as to integrate the electric furnace melting and molten steel roughing processes, and solve the problems existing in the above-mentioned traditional blast furnace-converter long process, electric furnace short process and electric furnace melting + converter smelting production.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A roughing device comprises a first smelting zone and a second smelting zone connected to each other. The first smelting zone is arranged at a higher position than the second smelting zone. The molten metal smelted in the first smelting zone flows naturally to the second smelting zone by gravity for smelting.

[0008] Optionally, the first smelting zone and the second smelting zone are connected in a slope or step-like manner.

[0009] Optionally, the first smelting zone and the second smelting zone are powered by electrical energy, chemical energy or nuclear energy.

[0010] Optionally, the first smelting zone and the second smelting zone are powered by electric energy, and electrodes are arranged at the top and / or bottom of the first smelting zone and the second smelting zone.

[0011] Optionally, the electrodes are provided in at least one group, and each group is provided with at least one electrode.

[0012] Optionally, the first smelting zone and the second smelting zone are powered by chemical energy, and spray guns and / or burners are arranged on the top and / or bottom and / or side walls of the first smelting zone.

[0013] Optionally, the spray gun and / or burner sprays carbon powder, flux, chemical fuel, oxygen, nitrogen or natural gas, coal gas.

[0014] Optionally, the rough refining device is provided with at least one steel tapping port and at least one slag tapping port.

[0015] A direct steelmaking system comprises a direct reduction device, a roughing device and a refining device arranged in sequence along the material flow direction, wherein the roughing device is the roughing device mentioned above.

[0016] Optionally, an intermediate storage bin is provided between the direct reduction device and the rough refining device, wherein one end of the intermediate storage bin is connected to the discharge port of the direct reduction device, and the other end is connected to the first smelting zone of the rough refining device.

[0017] Optionally, the intermediate storage bin is connected to the first smelting zone of the roughing device via a chute, a chute, a chain conveyor or a pneumatic conveyor.

[0018] Optionally, the direct reduction device is a vertical furnace, a fluidized bed, a rotary hearth furnace or a tunnel kiln.

[0019] Optionally, the furnace gas generated in the second smelting zone is returned to the first smelting zone or the direct reduction device.

[0020] Optionally, the refining device is one or more of CAS-OB, LF, RH, VD, and VOD.

[0021] A direct steelmaking method provides the above-mentioned continuous steelmaking system;

[0022] The metallized pellets are obtained by reduction in a direct reduction device;

[0023] adding the metallized pellets to the first smelting zone of a roughing device and heating and melting them to obtain slag and molten iron;

[0024] The molten iron flows naturally to the second smelting zone by gravity, where it is heated, smelted and impurities removed to obtain crude molten steel.

[0025] The crude molten steel is added to or flows into the refining device for refining to obtain qualified molten steel.

[0026] Optionally, an intermediate storage bin is provided between the direct reduction device and the crude refining device, one end of the intermediate storage bin is connected to the discharge port of the direct reduction device, and the other end is connected to the first smelting zone of the crude refining device; the metallized pellets are stored in the intermediate storage bin and then transported to the crude refining device.

[0027] Optionally, the metallization rate of the metallized pellets is greater than or equal to 60%, and the carbon content in the molten iron is not higher than 3.5%.

[0028] Optionally, flux and oxygen are injected into the second smelting zone through a spray gun to perform decarburization, dephosphorization and desulfurization.

[0029] Optionally, the flux is one or more of lime, light-burned dolomite, limestone, fluorite powder, synthetic slag-making agent, and iron ore powder.

[0030] The beneficial effects of the present invention are:

[0031] The present invention has the following advantages: First, it does not use molten iron, which can effectively reduce the carbon emissions of the steel production process; second, it can directly produce molten steel from solid iron-containing raw materials through a smelting equipment, without the intermediate links of molten iron tank lifting and transfer, which greatly improves the metal yield and reduces energy loss, reduces production costs and reduces carbon emissions, and reduces pollution; third, the roughing device can quickly and efficiently receive hot solid iron-containing raw materials, reduce energy loss, and reduce production costs; fourth, it can utilize the refining facilities, operation facilities and casting facilities of existing long-process steel mills, which is conducive to reducing equipment investment and has high scalability; fifth, it is conducive to the production of ultra-low nitrogen steel; sixth, it can realize the comprehensive recycling and energy recovery of high-temperature flue gas in the entire smelting link, which is a low-consumption, environmentally friendly new process.

[0032] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0034] FIG1 is a schematic diagram of a process of an embodiment. DETAILED DESCRIPTION

[0035] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0036] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0037] In the description of the present invention, it should be understood that if there are terms such as "up", "down", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0038] The roughing unit disclosed in the present invention includes a directly connected first and second smelting zones. The direct steelmaking system disclosed in the present invention includes an intermediate storage bin and conveying system for a direct reduction unit, a roughing unit, and a refining unit. The direct reduction unit is connected to the first smelting zone via a conveying system beneath the intermediate storage bin. One end of the intermediate storage bin is connected to the discharge port of the direct reduction unit, and the other end is connected to the first smelting zone of the roughing unit. The first and second smelting zones are directly connected, with the first smelting zone being higher than the second. Molten steel smelted in the second smelting zone can be connected to the refining unit via a chute or steel tank.

[0039] The direct steelmaking method disclosed in the present invention is to store the metallized pellets obtained by reduction in the direct reduction device through an intermediate storage bin, and then directly add them to the first smelting zone through a chute or a chute or a chain conveyor or pneumatic conveying. At the same time, the metallized pellets are heated and melted by an energy supply system arranged on the roughing device to obtain slag and molten iron as molten products, and the slag is regularly discharged through a slag outlet; the molten iron product flows naturally to the second smelting zone by gravity, is heated by the energy supply system, and is decarbonized, dephosphorized and desulfurized by flux and oxygen sprayed into the spray gun to obtain crude molten steel; the crude molten steel is added to the refining device through a chute or a molten steel tank, and qualified molten steel is obtained after the molten steel is refined.

[0040] Example 1

[0041] Taking the production of ordinary carbon steel varieties as an example, the method of producing qualified molten steel using a direct steelmaking system is described. As shown in Figure 1, the metallized pellets obtained by reduction in the direct reduction device are stored in an intermediate storage bin, where the metallization rate of the metallized pellets is 92%, the carbon content is 1.0%, and the SiO2 content is 4.5%. They are then added to the first smelting zone of the roughing device through a chute. The metallized pellets are heated and melted by electrodes arranged in the first smelting zone to obtain molten iron and slag. The C content in the molten iron is ≤3.5% and is located in the lower part of the molten pool. The slag is located in the upper part of the molten pool and can be discharged regularly through the slag outlet. The molten iron produced after smelting in the first smelting zone can flow naturally to the second smelting zone by gravity; in the second smelting zone, the molten iron is heated and heated by electrodes in the second smelting zone, and oxygen, lime, etc. are injected into the molten iron through a spray gun installed in the second smelting zone to decarburize, dephosphorize and heat the molten iron. The steel can be tapped after decarburization reaches the end point of C0.08-0.12%, P≤0.035%, and the temperature is not lower than 1580°C. After that, the crude molten steel is sent to the refining device LF through a chute or a molten steel tank for composition and temperature adjustment. The steel is tapped after the refining end point meets the composition and superheat requirements for subsequent continuous casting ladle pouring.

[0042] Example 2

[0043] Taking the production of ultra-low carbon steel as an example, the method of producing qualified molten steel using a direct steelmaking system is described. As shown in Figure 1, sintered ore or pellets are charged into a direct reduction device for reduction to obtain metallized pellets, wherein the metallization rate of the metallized pellets is 92%, the carbon content is 1.0%, and the SiO2 content is 4.5%. The metallized pellets are discharged to an intermediate storage bin and added to the first smelting zone of the roughing device through a chute. The metallized pellets are heated and melted by electrodes arranged in the first smelting zone to obtain molten iron and slag, wherein the C content of the molten iron is ≤3.5% and is located in the lower part of the molten pool. The slag is located in the upper part of the molten pool and can be discharged regularly through the slag outlet. The molten iron produced after smelting in the first smelting zone can flow naturally to the second smelting zone by gravity. Second smelting zone; in the second smelting zone, the molten iron is heated and heated by the electrodes in the second smelting zone, and oxygen, lime, etc. are sprayed into the molten iron through the spray gun set in the second smelting zone to decarburize, dephosphorize and heat the molten iron. The steel can be tapped after decarburization to the end point of C0.03-0.05%, P≤0.015%, and the temperature is not lower than 1680°C. After that, the crude molten steel is sent to the refining device RH through a chute or a molten steel tank for composition and temperature adjustment. The refining end point C≤30ppm, N≤30ppm, and the temperature is not lower than 1590°C for tapping, which meets the subsequent continuous casting ladle pouring composition and superheat requirements.

[0044] Example 3

[0045] The difference between Example 3 and Examples 1 and 2 is that the composition of the metallized pellets after direct reduction is a metallization rate of 85%, a carbon content of 2.0%, and a SiO2 content of 6.0%.

[0046] Comparative Example 1

[0047] When producing ultra-low carbon steel from conventional blast furnace iron, the process follows the blast furnace (BF) - converter (BOF) - refining (RH) process. The converter (BOF) uses molten iron as the primary raw material for smelting. The converter achieves a C content of 0.03-0.05%, a P content of ≤0.015%, a temperature of 1690°C, and a nitrogen content below 20 ppm in the molten steel. At this point, the steel can be tapped and hoisted to the RH for refining. The refining process achieves a C content of ≤30 ppm, a nitrogen content of ≤30 ppm, and a temperature of 1590°C, resulting in qualified molten steel.

[0048] Comparative Example 2

[0049] Using scrap steel and metallized pellets as raw materials, the process follows the following steps: scrap steel, metallized pellets - electric furnace - RH refining. Scrap steel and metallized pellets are added to the electric furnace for smelting. The electric furnace smelting process achieves an endpoint of C ≥ 0.05%, P ≤ 0.015%, and steel is tapped at 1690°C. The molten steel has a nitrogen content of approximately 80 ppm, at which point it is tapped and hoisted to the RH refining unit. RH refining achieves an endpoint of C ≤ 50 ppm, N ≤ 60 ppm, and qualified molten steel is tapped at 1590°C.

[0050] Among them, in the process of preparing qualified molten steel in Comparative Example 1, the converter uses molten iron from blast furnace as raw material. This process has high carbon emissions and is not conducive to reducing carbon emissions.

[0051] In the process of preparing qualified molten steel in Comparative Example 2, scrap steel and metallized pellets are used as raw materials in the electric furnace. However, due to the high gangue content in the metallized pellets and the large amount of electric furnace slag, the power consumption of the electric furnace is increased and the life of the refractory is reduced, which is not conducive to the operation of the electric furnace and economic production. In addition, the nitrogen content in the molten steel at the end of the electric furnace is high, and RH treatment denitrification is difficult, making it difficult to produce low-nitrogen steel grades.

[0052] With the direct steelmaking system and method of Examples 1, 2 and 3, the metallized pellets obtained by reduction in the direct reduction device are stored in an intermediate storage bin and added to the first smelting zone of the roughing device through a chute or a chute or a chain conveyor or pneumatic conveying. At the same time, the metallized pellets are heated and melted by an energy supply system provided on the roughing device to obtain slag and molten iron as molten products, and the slag is regularly discharged through the slag outlet; the molten iron product flows naturally to the second smelting zone by gravity, the molten steel is heated by energy supply, and the flux and oxygen injected by the spray gun are used for decarburization, dephosphorization and desulfurization, thereby obtaining crude molten steel; the crude molten steel is added to the refining device through a chute or a molten steel tank, and qualified molten steel is obtained after the molten steel is refined. The new process does not use molten iron, which can effectively reduce carbon emissions in the steel production process; it can directly produce molten steel from solid iron-containing raw materials through a smelting equipment, without the need for lifting and transferring molten iron tanks in between, greatly improving metal recovery and reducing energy loss, lowering production costs and carbon emissions, and reducing pollution; it can quickly and efficiently receive hot solid iron-containing raw materials, reduce energy loss, and lower production costs; it can utilize the refining facilities, operating facilities and casting facilities of existing long-process steel mills, which is conducive to reducing equipment investment and has high scalability; it can achieve comprehensive recycling and energy recovery of high-temperature flue gas in the entire smelting process, and is a low-consumption, environmentally friendly new process.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A crude refining device, characterized in that: It includes a first smelting zone and a second smelting zone connected to each other. The first smelting zone is arranged at a higher position than the second smelting zone. The molten metal smelted in the first smelting zone flows naturally to the second smelting zone by gravity for smelting.

2. The crude refining device according to claim 1, characterized in that: The first smelting zone and the second smelting zone are connected in a slope or step shape.

3. The crude refining device according to claim 1, characterized in that: The first smelting zone and the second smelting zone are powered by electrical energy, chemical energy or nuclear energy.

4. The crude refining device according to claim 1, characterized in that: The first smelting zone and the second smelting zone are powered by electric energy, and electrodes are arranged on the top and / or bottom of the first smelting zone and the second smelting zone.

5. The crude refining device according to claim 4, characterized in that: The electrodes are provided in at least one group, and each group is provided with at least one electrode.

6. The crude refining device according to claim 1, characterized in that: The first smelting zone and the second smelting zone are powered by chemical energy, and lances and / or burners are arranged on the top and / or bottom and / or sidewall of the first smelting zone.

7. The crude refining device according to claim 6, characterized in that: The spray gun and / or burner sprays carbon powder, flux, chemical fuel, oxygen or natural gas, nitrogen or coal gas.

8. The crude refining device according to claim 1, characterized in that: The roughing device is provided with at least one steel tapping port and at least one slag tapping port.

9. A direct steelmaking system, characterized in that: A direct reduction device, a crude refining device and a refining device are sequentially arranged along the material flow direction, wherein the crude refining device is a crude refining device according to any one of claims 1-8.

10. The direct steelmaking system according to claim 9, characterized in that: An intermediate storage bin is provided between the direct reduction device and the roughing device. One end of the intermediate storage bin is connected to the discharge port of the direct reduction device, and the other end is connected to the first smelting zone of the roughing device.

11. The direct steelmaking system according to claim 10, characterized in that: The intermediate storage bin is connected to the first smelting zone of the roughing device via a chute, a chute, a chain conveyor or a pneumatic conveyor.

12. The direct steelmaking system according to claim 9, characterized in that: The direct reduction device is a vertical furnace, a fluidized bed, a rotary hearth furnace or a tunnel kiln.

13. The direct steelmaking system according to claim 9, characterized in that: The furnace gas generated in the second smelting zone is returned to the first smelting zone or the direct reduction device.

14. The direct steelmaking system according to claim 9, characterized in that: The refining device is one or more of CAS-OB, LF, RH, VD, and VOD.

15. A direct steelmaking process, characterized in that: Providing a direct steelmaking system according to any one of claims 9 to 14; The metallized pellets are obtained by reduction in a direct reduction device; adding the metallized pellets to the first smelting zone of a roughing device and heating and melting them to obtain slag and molten iron; The molten iron flows naturally to the second smelting zone by gravity, where it is heated, smelted and impurities removed to obtain crude molten steel. The crude molten steel is added to the refining device for refining to obtain qualified molten steel.

16. The direct steelmaking process according to claim 15, characterized in that: An intermediate storage bin is provided between the direct reduction device and the rough refining device, one end of the intermediate storage bin is connected to the discharge port of the direct reduction device, and the other end is connected to the first smelting zone of the rough refining device; the metallized pellets are stored in the intermediate storage bin and then transported to the rough refining device.

17. The direct steelmaking process according to claim 15, characterized in that: The metallization rate of the metallized pellets is greater than or equal to 60%, and the carbon content in the molten iron is not higher than 3.5%.

18. The direct steelmaking process according to claim 15, characterized in that: In the second smelting zone, flux and oxygen are injected through a lance to carry out decarburization, dephosphorization and desulfurization.

19. The direct steelmaking process according to claim 18, characterized in that: The flux is one or more of lime, light-burned dolomite, limestone, fluorite powder, synthetic slag-making agent, and iron ore powder.

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