Process for smelting molten iron for converter steelmaking by using hydrogen-based shaft furnace direct reduction iron

Abstract

The invention relates to a process for smelting molten iron for converter steelmaking by using hydrogen-based shaft furnace direct reduction iron. The process comprises the following steps: 1) smelting raw materials comprise direct reduction iron, coke powder and lime; and (2) after the smelting raw materials enter the furnace, a material accumulation area is formed between the electrode and the furnace lining, the height of the accumulation area is larger than the length of an electric arc generated by the electrode, and the distance between the bottom of the electrode and the liquid level of molten iron is kept to be 200-300 mm. And 3) continuously supplying power to the electrodes, continuously melting the smelting raw materials, and forming a molten iron layer, a slag layer and a raw material layer at the furnace bottom from bottom to top. And (4) the pressure in the furnace is controlled within 0-100 pa. And (5) the molten iron generated by the electric furnace and the slag are regularly discharged in a slag-iron mixing mode. According to the method, a blast furnace ironmaking process is not used, and the direct reduced iron produced by hydrogen-based shaft furnace smelting is directly used as a main raw material to smelt the molten iron, so that the possibility that the hydrogen-based reduced iron is used for converter steelmaking on a large scale is provided.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical processes, and in particular relates to a process for smelting molten iron for converter steelmaking by directly reducing iron in a hydrogen-based vertical furnace. Background Art

[0002] The steel industry is an important economic support industry in China and also a major carbon emission industry. The application of hydrogen energy in the metallurgical field is an environmentally friendly and efficient steel production technology, and is one of the important ways to achieve low-carbon development. At present, the production of China's steel industry is still dominated by long processes, and the hydrogen-based direct reduction process can be used as the main route for future development. Hydrogen-based molten reduction also has a good carbon emission reduction effect, and the high-purity foundry pig iron produced can be used in the field of high-end castings. However, the large amount of direct reduced iron produced by the hydrogen-based vertical furnace added to the converter will cause the temperature in the converter to drop too much, increase costs, and reduce the quality of molten steel, which is not conducive to subsequent production. With the development of the green hydrogen industry, green hydrogen metallurgy will be an important direction for the green development of the steel industry in the future. Smelting direct reduced iron into molten iron and adding it to the converter can realize the green smelting route and ensure the existing long process production, which is of great significance. Summary of the invention

[0003] The purpose of the present invention is to provide a process for smelting molten iron for converter steelmaking by directly reducing iron in a hydrogen-based vertical furnace, so as to provide strong support for the large-scale production of direct reduced iron in a hydrogen-based vertical furnace and its use in the converter steelmaking process route.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The process of using a hydrogen-based vertical furnace to directly reduce iron to smelt hot metal for converter steelmaking specifically includes the following steps:

[0006] 1) Smelting raw materials are added into the electric furnace through the charging system on the top of the electric furnace. The smelting raw materials include direct reduced iron, coke powder and lime.

[0007] 2) After the smelting raw materials enter the furnace, a material accumulation area is formed between the electrode and the furnace lining. The height of the accumulation area is higher than the arc length generated by the electrode, and the bottom of the electrode maintains a distance of 200 to 300 mm from the molten iron liquid surface.

[0008] 3) The electrodes are continuously powered, and the smelting raw materials are gradually melted, forming a molten iron layer, a slag layer and a raw material layer from bottom to top at the bottom of the furnace.

[0009] 4) Micro positive pressure smelting is adopted in the furnace. During normal production, the pressure in the furnace is controlled at 0-100 Pa.

[0010] 5) The molten iron and slag produced by the electric furnace are discharged regularly in the form of slag-iron mixing. The slag is lightly located above the molten iron. The slag and iron are separated by a slag retaining device, and the molten iron is transported to the converter workshop.

[0011] The top of the electric furnace is provided with a pressure detection element, a flue gas pipeline system and a raw gas emission system. The pressure detection element feeds back the pressure in the furnace in real time. Under normal production conditions, the generated furnace gas is sent to the dust removal system through the flue gas pipeline system for purification and then sent to the designated user. When the pressure in the furnace exceeds the set value, it means that the furnace has changed or the flue gas pipeline system has an abnormality. To prevent accidents, the pipeline valve of the raw gas emission system is opened in time, and the furnace gas is discharged through the raw gas emission system, so that the furnace gas is discharged to the designated location through the raw gas emission system.

[0012] In the step 5), the interval between the regular discharge of molten iron and slag is 2 to 3 hours.

[0013] The furnace body of the electric furnace includes a furnace shell, a furnace cover, and a furnace lining. The furnace cover is on the top of the furnace body. A pressure detection element and a thermocouple are arranged inside the furnace cover. The feeding system is connected to the furnace cover, and the exhaust gas pipeline system and the raw gas emission system are also connected to the furnace cover.

[0014] The furnace shell is made of carbon steel material with a thickness of 20 to 30 mm.

[0015] A furnace bottom thermocouple is buried in the bottom of the electric furnace and just below the electrode.

[0016] The furnace cover is a water-cooled furnace cover with a water-cooling pipeline arranged therein.

[0017] The electrodes are self-baking electrodes, which are pressed downward by 20 to 30 cm every 0.5 to 1.5 hours.

[0018] The direct reduced iron is derived from a hydrogen-based vertical furnace.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] Compared with the prior art, the present invention does not use the blast furnace ironmaking process, but directly uses the direct reduced iron produced by hydrogen-based vertical furnace smelting as the main raw material to smelt molten iron, thus changing the original blast furnace + converter production route (such as Figure 1 The production process of hydrogen-based vertical furnace + ASF electric furnace + converter has been changed to hydrogen-based vertical furnace + ASF electric furnace + converter, making it possible to use hydrogen-based reduced iron on a large scale in converter steelmaking. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the production flow chart of traditional blast furnace smelting molten iron + converter steelmaking.

[0022] Figure 2The present invention is a production flow chart of using direct reduced iron to smelt molten iron + converter steelmaking.

[0023] Figure 3 The figure is a schematic diagram of the furnace structure of the ASF electric furnace of the present invention for smelting molten iron using direct reduced iron.

[0024] Figure 4 This is a flow chart of feed control in the process of the present invention.

[0025] Figure 5 It is a schematic diagram of the iron-casting process in the process of the present invention.

[0026] In the figure: 1-furnace shell 2-furnace lining 3-furnace cover 4-thermocouple in furnace cover 5-pressure detection element 6-exhaust gas pipeline system 7-raw gas emission system 8-raw gas emission system valve 9-electrode 10-feeding system 11-raw material layer 12-slag layer 13-molten iron layer 14-furnace bottom thermocouple 15-slag blocking device 16-slag chute 17-molten iron chute 18-torpedo tank. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the specific implementation methods of the present invention are further described below in conjunction with embodiments. The following embodiments are used to specifically illustrate the contents of the present invention. These embodiments are only general descriptions of the contents of the present invention and do not limit the contents of the present invention.

[0028] like Figure 2-Figure 5 As shown, the process of using a hydrogen-based vertical furnace to directly reduce iron to smelt molten iron for converter steelmaking specifically includes the following steps:

[0029] 1) Smelting raw materials are added into the electric furnace through the charging system 10 at the top of the electric furnace. The smelting raw materials include direct reduced iron, coke powder and lime.

[0030] The feeding system 10 is located on the top of the electric furnace, including an annular silo on the top, a feeding pipe and a variable frequency feeder. The materials required for production are stored in the annular silo on the top of the furnace. Through the batching calculation, the batching plan is set, and the feeding system is started to weigh and feed. When the set value is reached, the feeding is stopped and the next round of feeding is waited for. Figure 4 shown.

[0031] 2) After the smelting raw materials enter the furnace, a material accumulation area is formed between the electrode 9 and the furnace lining 2. This area protects the furnace lining 2 while ensuring material supply.

[0032] The height of the accumulation area is higher than the arc length generated by the electrode 9, and the bottom of the electrode is kept at a distance of 200 to 300 mm from the molten iron surface, preferably 250 mm. The raw materials are continuously fed into the furnace. When the raw materials in the furnace are melted, the raw materials in the feeding system 10 will enter the furnace.

[0033] See Figure 3 , raw materials are added into the furnace through the feeding system 10 to form a raw material layer 11. The raw material layer 11 should be higher than the arc length generated by the electrode 9 to improve the melting efficiency and protect the furnace lining 2. The bottom of the electrode 9 is kept at a certain distance above the slag layer 12. This distance is required to ensure that the electrode 9 can start an arc and the heat generated can melt the raw material layer 11.

[0034] The position and height of charge stacking must be reasonably controlled. In addition to meeting the needs of smelting production, it should also meet the purpose of shielding the arc and protecting the furnace lining.

[0035] 3) The electrode 9 is continuously powered, and the smelting raw materials are gradually melted, forming a molten iron layer 13, a slag layer 12 and a raw material layer 11 from bottom to top at the bottom of the furnace.

[0036] The present invention replaces the traditional lump ore as the main raw material with direct reduced iron as the main smelting raw material. Since the direct reduced iron has low resistance and cannot generate resistance heat, an open arc operation is adopted to supply power and strike an arc, and the direct reduced iron is melted by the arc heat.

[0037] The electrode 9 is continuously powered, the materials gradually melt into the furnace, and a series of physical and chemical reactions occur, eventually forming qualified molten iron.

[0038] During the smelting process, the density of the liquid slag produced is greater than the specific gravity of the smelting raw materials (direct reduced iron + lime + coke powder), so the smelting raw materials float on the liquid slag.

[0039] See Figure 3 During the heating and melting process of the raw material layer 11, the direct reduced iron undergoes a violent physical and chemical reaction with raw materials such as coke powder and lime. The iron melts to form a molten iron layer 13, and non-iron impurities and iron oxides react chemically with coke and lime to form a slag layer 12. Since the specific gravity of molten iron is greater than the specific gravity of slag and greater than the specific gravity of the raw material pile, the molten iron layer 13 is located at the bottom of the furnace, the slag layer 12 is in the middle, and the raw material layer 11 is located on the slag layer 12.

[0040] The electrode 9 is a self-baking electrode, and the electrode system is provided with a pressing device. As the bottom electrode is consumed, the electrode 9 is pressed downward intermittently as required, and is pressed downward by 20 to 30 cm every 0.5 to 1.5 hours. In some embodiments, the electrode is pressed downward by 25 cm every 1 hour.

[0041] 4) Micro-positive pressure smelting is adopted in the furnace. During normal production, the pressure in the furnace is controlled within 100pa.

[0042] 5) The molten iron and slag produced by the electric furnace are discharged regularly in the form of slag-iron mixing. The slag is lightly located above the molten iron, and the slag and iron are separated by the slag retaining device 15. The slag 12 passes through the slag chute 16 and enters the slag pool for storage or water quenching. The molten iron passes through the molten iron chute 17 and enters the thunder tank 18, and the molten iron is transported to the converter workshop.

[0043] According to calculation, the furnace mouth is opened at regular intervals to discharge iron and slag; the regular discharge interval of molten iron and slag is 2-3 hours, preferably 2 hours. Molten iron is sent to the steelmaking workshop for standby through torpedo tank cars, and slag is sent to the slag yard for storage after water quenching.

[0044] The oxides in the furnace react chemically with the reducing agent to generate furnace gas. The main component of the furnace gas generated during the smelting process is CO. The furnace smelting adopts micro-positive pressure smelting. The top of the electric furnace is equipped with a pressure detection element 5, a flue gas pipeline system 6 and a raw gas emission system 7. The pressure detection element 5 provides real-time feedback of the pressure in the furnace. Under normal production conditions, the pressure in the furnace is controlled within 100pa. The generated furnace gas is sent to the dust removal system through the flue gas pipeline system 6 for purification and then sent to the designated user; when the pressure in the furnace exceeds the set value, it means that the furnace mine has changed or the flue gas pipeline system 6 has an abnormality. In order to prevent accidents, the raw gas emission system valve 8 is opened in time, and the furnace gas is discharged through the raw gas emission system 7, so that the furnace gas is discharged to the designated location through the raw gas emission system 7.

[0045] The furnace body of the electric furnace comprises a furnace shell 1, a furnace cover 3, and a furnace lining 2. The furnace cover 3 is at the top of the furnace body. A pressure detection element 5 and a thermocouple 4 in the furnace cover are arranged in the furnace cover 3. The charging system 10 is connected to the furnace cover 3. The exhaust gas pipeline system 6 and the raw gas exhaust system 7 are also connected to the furnace cover 3. The electric furnace of the present invention is named ASF electric furnace.

[0046] The furnace shell 1 is made of carbon steel with a thickness of 20-30 mm. In some embodiments, the furnace shell 1 has a thickness of 25 mm.

[0047] The furnace cover 3 is a water-cooled furnace cover with a water-cooling pipe inside. The furnace cover 3 is evenly distributed with multiple thermocouples 4 inside the furnace cover for observing the temperature inside the furnace. When the temperature displayed by the thermocouple 4 inside the furnace cover exceeds the set value, it means that the furnace is abnormal and an emergency plan needs to be taken to ensure the stability of the furnace condition. The furnace cover 3 is evenly distributed with multiple pressure detection elements 5 for observing the pressure inside the furnace. This process uses micro-positive pressure operation. During normal production, the coal gas generated in the furnace is transported to the coal gas dust removal system through the flue gas system 6 for treatment and then transported to the user point for use. When the pressure in the furnace is higher than the set value, the raw gas emission system valve 8 in the raw gas emission flue system 7 is opened, and the coal gas enters the raw gas emission system.

[0048] The temperature of the furnace cover 1 is measured in real time by the thermocouple 4 in the furnace cover. If the temperature is too high, the furnace condition or the furnace cover cooling water system should be checked in time.

[0049] A furnace bottom thermocouple 14 is buried in the bottom of the electric furnace and just below the electrode 9 .

[0050] The furnace lining 2 is built with aluminum-magnesium and carbon refractory bricks, which are divided into permanent layer and working layer, and the furnace mouth is built with high-aluminum refractory bricks. A furnace bottom thermocouple 14 is buried in the furnace bottom just below the electrode 9 to monitor the temperature of the furnace bottom refractory material. If the temperature is higher than the set value, an alarm will be triggered.

[0051] The direct reduced iron is derived from a hydrogen-based vertical furnace.

Claims

1. A process for smelting hot metal for converter steelmaking by directly reducing iron using a hydrogen-based vertical furnace, characterized in that: The specific steps include: 1) Add smelting raw materials into the electric furnace through the charging system on the top of the electric furnace. The smelting raw materials include direct reduced iron, coke powder and lime; 2) After the smelting raw materials enter the furnace, a material accumulation area is formed between the electrode and the furnace lining. The height of the accumulation area is higher than the arc length generated by the electrode, and the bottom of the electrode is kept at a distance of 200 to 300 mm from the molten iron surface; 3) The electrodes are continuously powered, the smelting raw materials are gradually melted, and a molten iron layer, a slag layer and a raw material layer are formed from bottom to top at the bottom of the furnace; 4) Micro-positive pressure smelting is adopted in the furnace. During normal production, the pressure in the furnace is controlled at 0-100 Pa; 5) The molten iron and slag produced by the electric furnace are discharged regularly in the form of slag-iron mixing. The slag is lightly located above the molten iron. The slag and iron are separated by a slag retaining device, and the molten iron is transported to the converter workshop.

2. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 1, characterized in that: The top of the electric furnace is provided with a pressure detection element, a flue gas pipeline system and a raw gas emission system. The pressure detection element provides real-time feedback of the pressure inside the furnace. Under normal production conditions, the generated furnace gas is sent to the dust removal system for purification through the flue gas pipeline system; when the pressure inside the furnace exceeds the set value, the furnace gas is discharged through the raw gas emission system.

3. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 1, characterized in that: In the step 5), the interval between the regular discharge of molten iron and slag is 2 to 3 hours.

4. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 2, characterized in that: The furnace body of the electric furnace includes a furnace shell, a furnace cover, and a furnace lining. The furnace cover is on the top of the furnace body. A pressure detection element and a thermocouple are arranged inside the furnace cover. The feeding system is connected to the furnace cover, and the exhaust gas pipeline system and the raw gas emission system are also connected to the furnace cover.

5. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 2, characterized in that: The furnace shell is made of carbon steel material with a thickness of 20 to 30 mm.

6. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 1 or 2, characterized in that: A furnace bottom thermocouple is buried in the bottom of the electric furnace and just below the electrode.

7. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 2, characterized in that: The furnace cover is a water-cooled furnace cover with a water-cooling pipe arranged therein.

8. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 1, characterized in that: The electrodes are self-baking electrodes, which are pressed downward by 20 to 30 cm every 0.5 to 1.5 hours.

9. The process for smelting molten iron for converter steelmaking by direct reduction of iron using a hydrogen-based vertical furnace according to claim 1, characterized in that: The direct reduced iron is derived from a hydrogen-based vertical furnace.

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