Bottom furnace baking method for all-molten iron sintering furnace of electric furnace

Abstract

The invention discloses an electric furnace all-molten iron sintering furnace bottom baking method which comprises the following steps: (1) after knotting of a furnace bottom is completed, laying a steel plate and pig iron at an iron inlet of the furnace bottom; (2) the first ladle of molten iron is added for 15-20 min; (3) carrying out weak oxygen supply decarburization operation, blowing at a low temperature of 1250-1520 DEG C, and controlling the time to be 150 minutes + / -30 minutes; (4) in the strong oxygen supply rapid decarburization period, the maximum oxygen flow is adopted for blowing for 10-15 min, the temperature in the furnace is increased to 1580-1600 DEG C, and the tapping temperature is increased; (5) after the components of carbon and phosphorus meet the requirements of the tapping process, performing low-level power supply operation, raising the temperature to 1660-1680 DEG C, and sintering at the bottom of the furnace for 30-60 minutes; and (6) when the tapping hole is replaced, observing the furnace bottom, the furnace slope and local shimming, and tracking the furnace bottom temperature monitoring curve in the whole furnace service period. The method has the advantages of improving thermal shock resistance and erosion resistance of a sintering layer of the furnace bottom ramming material, saving energy, reducing consumption, and being safe and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for baking a furnace bottom of an electric furnace for sintering all-molten iron. Background Art

[0002] When a new electric furnace is commissioned, ramming mass is added to harden and sinter at high temperatures, improving the corrosion resistance and protecting the furnace bottom. Typically, this mass is composed of a high proportion of granular and powdered materials, with a low proportion of binders and other components, or even entirely of granular and powdered materials. This mass is used to sinter into layers, insulating the molten pool from direct contact with the furnace bottom. Because ramming mass is primarily used in direct contact with the melt, the resulting sintered layer must possess excellent stability, density, and corrosion resistance. Furthermore, for ramming mass of the same material, the temperature gradient and uniformity within the furnace during startup are crucial for determining the sintering quality and uniformity of the ramming mass.

[0003] However, the bottom of the electric furnace uses ramming material to ensure the sintering thickness through high-temperature sintering. The ramming material generally starts to sinter at 1100℃, and 1650℃ is the optimal sintering temperature. Traditional electric furnaces use scrap steel to bake and sinter the bottom of the furnace. During the sintering process, the scrap steel needs to be melted by electricity before sintering, and the melting time of the scrap steel is relatively long. The bottom of the furnace is heated unevenly, resulting in uneven sintering of the bottom of the furnace, rapid erosion of the bottom of the furnace, and the ramming material of the bottom of the furnace flipping up during the steel tapping process. The refractory material blocks the steel tapping port, affecting the smelting time. When replacing the steel tapping port, the furnace bottom needs to be padded and the furnace bottom needs to be sintered for the second time, which increases the consumption of furnace bottom materials.

[0004] The high-temperature arc of this all-scrap steel drying furnace causes serious radiation damage to the newly built refractory materials. In addition, the furnace cover needs to be opened when the all-scrap steel furnace is being dried, resulting in large heat loss in the molten pool. At the same time, it is operated with power supply throughout the entire process, with high power consumption of 600 kWh / ton of steel and electrode consumption of 3 kg / t of steel, resulting in high costs. Summary of the Invention

[0005] The purpose of the present invention is to solve the problems of uneven heating, high energy consumption and high cost in the existing furnace baking method, and to provide an electric furnace full-hot metal sintering furnace bottom baking method, which can improve the thermal shock resistance and corrosion resistance of the sintered layer of the ramming material at the furnace bottom, improve the sintering effect of the ramming material, save energy and reduce consumption, and be safe and efficient.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for baking a furnace bottom for sintering hot metal in an electric furnace, comprising the following steps: (1) After the furnace bottom is knotted, steel plates and pig iron are used to pave the iron inlet of the furnace bottom to effectively prevent the outlet from being washed by the iron flow when a new furnace is opened with full molten iron; (2) Significantly reduce the speed of adding the first ladle of molten iron, control the time of adding the first ladle of molten iron to 15-20 minutes, and keep the liquid level in the furnace rising slowly, in order to maintain the initial shape of the furnace bottom and furnace slope; (3) Weak oxygen supply decarburization operation at low temperature causes the temperature in the furnace to rise slowly. The low temperature is 1250℃~1520℃, and the time is controlled at 150min±30min. After the ramming material is sintered in this stage, it expands slightly. After sintering, the grains are small and uniform in size, with few intercrystalline gaps. There are no large pores remaining between the grains due to sintering mass transfer and particle aggregation and growth. The temperature rises evenly, and at the same time, it ensures that it does not produce a large number of dense and wide cracks, preventing the slag from penetrating the "channel" and improving the service life. (4) Strong oxygen supply rapid decarburization period, using the maximum oxygen flow rate to blow for 10-15 minutes, increasing the carbon-oxygen reaction and raising the furnace temperature to 1580-1600℃ tapping temperature. This stage is mainly based on sampling and phosphorus composition, and normal smelting operations are carried out until the tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, the low-level power supply is operated, the temperature is raised to 1660~1680℃, and the furnace bottom is sintered for 30~60min. This stage mainly adopts high-temperature sintering. After sintering, the sintered layer has high density and good volume stability, and further has thermal shock resistance and corrosion resistance; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make local padding, and track the furnace bottom temperature monitoring curve throughout the entire furnace service life.

[0007] Furthermore, in the step (3), the blowing is carried out at 1250° C. with a low oxygen flow rate, and the time is controlled within 120 minutes.

[0008] Furthermore, in the step (3), the blowing is carried out at 1250° C. with a low oxygen flow rate, and the time is controlled at 165 minutes.

[0009] Furthermore, in step (4), the maximum oxygen flow rate is used for blowing for 12 minutes to increase the carbon-oxygen reaction and raise the temperature in the furnace to 1580-1600°C, the tapping temperature.

[0010] Furthermore, in step (4), the maximum oxygen flow rate is used for blowing for 14 minutes to increase the carbon-oxygen reaction and raise the temperature in the furnace to 1580-1600°C, the tapping temperature.

[0011] Furthermore, in step (5), the temperature is raised to 1660-1680°C and the furnace bottom is sintered for 43 minutes.

[0012] Furthermore, in step (5), the temperature is raised to 1660-1680°C and the furnace bottom is sintered for 47 minutes.

[0013] Compared with the prior art, the advantages of the technical solution of the present invention are: (1) The present invention adopts all-molten iron to sinter the furnace bottom. Through the physical heat of molten iron at 1350°C, after being added into the furnace, the molten iron can completely cover the ramming material at the furnace bottom, sintering the ramming material at the furnace bottom evenly. The low oxygen supply intensity makes the molten pool evenly heated, thereby improving the sintering effect of the ramming material. (2) The present invention adopts a furnace shell of an all-hot iron drying furnace, which has better effects on furnace break sintering and furnace bottom sintering than all-scrap steel sintering. The number of furnace repairs during the production process is reduced, the production efficiency is improved, and the furnace life is significantly improved. During the entire furnace life cycle, the highest point of the furnace bottom temperature drops from 350°C to 320°C, and the safety performance of the furnace bottom is further improved. (3) After the molten iron in the full-hot iron drying furnace of the present invention is put into the furnace, the molten iron can completely fill the ramming material area at the bottom of the furnace, and the sintered layer at the bottom of the furnace can reach 250-300 mm after sintering; (4) The present invention adopts a full hot metal drying furnace, and the electrodes do not need to be powered for a long time during the furnace opening, which can effectively save electricity and reduce energy consumption; (5) The method of the present invention reduces the number of furnace bottom padding operations, thereby reducing the tapping port inspection time by 120 minutes per time and the sintering time by 120 minutes per time, thereby saving production time and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the distribution of the molten pool area and the furnace bottom charging area of the present invention. DETAILED DESCRIPTION Example 1

[0015] To make the present invention more clear, the following further describes an electric furnace full-hot metal sintering furnace bottom baking method of the present invention in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0016] See also Figure 1 The present invention uses a molten iron furnace to sinter the furnace bottom, which includes a molten pool area 1 and a furnace bottom ramming material area 2. The molten iron itself heats up to 1350°C. After being added to the furnace, the molten iron can completely cover the furnace bottom ramming material, evenly sintering the furnace bottom ramming material. The low oxygen supply intensity allows the molten pool to be evenly heated, improving the sintering effect of the ramming material. After the molten iron is added to the furnace, the molten iron can completely cover the furnace bottom ramming material area 2. After sintering, the furnace bottom sintering layer can reach 250-300mm.

[0017] First, a comparative example in which the method of the present invention is not adopted is provided, as follows: (1) After the furnace bottom is knotted, the scrap steel is loaded into the hanging basket and added into the furnace by the crane; (2) Use the lowest electrode voltage and current to slowly heat the scrap steel, causing it to melt and form a molten pool to provide sintering heat; (3) After the molten pool is formed, use the oxygen lance in low flow mode to slowly blow oxygen for smelting; (4) During the strong oxygen supply rapid decarburization period, the maximum oxygen flow rate is used for blowing for 10 minutes to increase the carbon-oxygen reaction and raise the furnace temperature to 1580~1600℃ (steel tapping temperature). This stage mainly carries out normal smelting operations based on sampling and phosphorus composition until the steel tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, operate with low-level power supply, raise the temperature to 1660~1680℃, and sinter the furnace bottom for 40 minutes; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make partial shims, and track the furnace bottom temperature monitoring curve throughout the service life. After 100 furnaces, the furnace bottom temperature detection curve slowly rose to 214℃, and the final service life was 494 times.

[0018] In this embodiment, the method for baking the bottom of an electric furnace for sintering all-hot metal according to the present invention is characterized in that: (1) After the furnace bottom is knotted, steel plates and pig iron are used to pave the iron inlet of the furnace bottom to effectively prevent the outlet from being washed by the iron flow when a new furnace is opened with full molten iron; (2) Add the first batch of molten iron. The time for adding the first batch of molten iron is 15 minutes. The purpose is to maintain the initial shape of the furnace bottom and furnace slope; (3) At low temperature, the ramming material is blown from 1250℃ with low oxygen flow for 120min. After sintering at this stage, the ramming material expands slightly. After sintering, the grains are small and uniform in size, with few intercrystalline gaps. There are no large pores remaining between the grains due to sintering mass transfer and particle aggregation and growth. The uniform temperature rise also ensures that it does not produce a large number of dense and wide cracks, preventing the slag from penetrating the "channel" and improving the service life. (4) During the strong oxygen supply rapid decarburization period, the maximum oxygen flow rate is used for blowing for 10 minutes to increase the carbon-oxygen reaction and raise the furnace temperature to 1580~1600℃ (steel tapping temperature). This stage mainly carries out normal smelting operations based on sampling and phosphorus composition until the steel tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, the low-level power supply is operated, the temperature is raised to 1660~1680℃, and the furnace bottom is sintered for 40 minutes. This stage mainly adopts high-temperature sintering. After sintering, the sintered layer has high density and good volume stability, and further has thermal shock resistance and corrosion resistance; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make partial shims, and track the furnace bottom temperature monitoring curve throughout the furnace service life. After 100 furnace cycles, the furnace bottom temperature detection curve slowly rose to 209°C, and the final service life was 663 times, which was 166 times higher than the average life of a full scrap furnace of 500 furnace cycles. Example 2

[0019] In this embodiment, the method for baking the bottom of an electric furnace for sintering all-hot metal according to the present invention is characterized in that: (1) After the furnace bottom is knotted, steel plates and pig iron are used to pave the iron inlet of the furnace bottom to effectively prevent the outlet from being washed by the iron flow when a new furnace is opened with full molten iron; (2) Add the first batch of molten iron. The time for adding the first batch of molten iron is 17 minutes. The purpose is to maintain the initial shape of the furnace bottom and furnace slope. (3) At low temperature, low oxygen flow is used for blowing from 1250℃ for 165min. After sintering at this stage, the ramming material expands slightly. After sintering, the grains are small and uniform in size, with few intercrystalline gaps. There are no large pores remaining between the grains due to sintering mass transfer and particle aggregation and growth. The uniform temperature rise also ensures that it does not produce a large number of dense and wide cracks, preventing the slag from penetrating the "channel" and improving the service life. (4) During the strong oxygen supply rapid decarburization period, the maximum oxygen flow rate is used for blowing for 14 minutes to increase the carbon-oxygen reaction and raise the furnace temperature to 1580~1600℃ (steel tapping temperature). This stage mainly carries out normal smelting operations based on sampling and phosphorus composition until the steel tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, the low-level power supply is operated, the temperature is raised to 1660~1680℃, and the furnace bottom is sintered for 43 minutes. This stage mainly adopts high-temperature sintering. After sintering, the sintered layer has high density and good volume stability, and further has thermal shock resistance and corrosion resistance; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make partial shims, and track the furnace bottom temperature monitoring curve throughout the furnace service life. After 100 furnace cycles, the furnace bottom temperature detection curve slowly rose to 206°C, and the final service life was 671 times, which was 171 times higher than the average life of a full scrap furnace of 500 furnace cycles. Example 3

[0020] In this embodiment, the method for baking the bottom of an electric furnace for sintering all-hot metal according to the present invention is characterized in that: (1) After the furnace bottom is knotted, steel plates and pig iron are used to pave the iron inlet of the furnace bottom to effectively prevent the outlet from being washed by the iron flow when a new furnace is opened with full molten iron; (2) Add the first batch of molten iron. The time for adding the first batch of molten iron is 19 minutes. The purpose is to maintain the initial shape of the furnace bottom and furnace slope. (3) At low temperature, low oxygen flow is used for blowing from 1250℃ for 150min. After sintering at this stage, the ramming material expands slightly. After sintering, the grains are small and uniform in size, with few intercrystalline gaps. There are no large pores remaining between the grains due to sintering mass transfer and particle aggregation and growth. The uniform temperature rise also ensures that it does not produce a large number of dense and wide cracks, preventing the slag from penetrating the "channel" and improving the service life. (4) During the strong oxygen supply rapid decarburization period, the maximum oxygen flow rate is used for blowing for 12 minutes to increase the carbon-oxygen reaction and raise the furnace temperature to 1580~1600℃ (steel tapping temperature). This stage mainly involves normal smelting operations based on sampling and phosphorus composition until the steel tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, the low-level power supply is operated, the temperature is raised to 1660~1680℃, and the furnace bottom is sintered for 47 minutes. This stage mainly adopts high-temperature sintering. After sintering, the sintered layer has high density and good volume stability, and further has thermal shock resistance and corrosion resistance; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make partial shims, and track the furnace bottom temperature monitoring curve throughout the furnace service life. After 100 furnace cycles, the furnace bottom temperature detection curve slowly rose to 201°C, and the final service life was 693 times, which was 193 times higher than the average life of 500 furnace cycles of a full scrap steel furnace.

[0021] The present invention utilizes the physical heat of molten iron and the chemical heat generated during the oxygen blowing smelting process as heat sources to bake the furnace, aiming to improve the thermal shock resistance and corrosion resistance of the sintered layer of the furnace bottom ramming material, thereby solving the problems of rapid erosion of the furnace bottom and rapid temperature rise, improving the safety factor of the furnace bottom, and at the same time reducing the number of times the furnace bottom is padded at the steel tapping port and the amount of furnace bottom ramming material used, which is of great significance to efficient and low-cost production.

[0022] Based on the calculation that the power consumption of starting a furnace with all scrap steel is 600kwh / t steel, starting a furnace with all molten iron is expected to reduce power consumption by 90%, saving about 70,000 yuan in electricity bills.

[0023] In addition, the method of the present invention reduces the number of furnace bottom padding times, reduces the steel outlet maintenance time, and reduces the sintering time, saving 480 minutes in the entire furnace life cycle, equivalent to an output of 1,000 tons, and generating a benefit of approximately 200,000 yuan.

[0024] At the same time, the present invention adopts an all-hot iron furnace, and each time the furnace shell is replaced, the cost can be reduced. If the furnace is replaced 15 times a year, the annual cost can be reduced by more than 4 million yuan.

[0025] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the scope of protection required by the present invention.

Claims

1. A method for baking a furnace bottom for sintering hot metal in an electric furnace, characterized by: (1) After the furnace bottom is knotted, steel plates and pig iron are used to pave the iron inlet of the furnace bottom; (2) Significantly reduce the speed of adding the first ladle of molten iron, control the time of adding the first ladle of molten iron to 15-20 minutes, and keep the liquid level in the furnace rising slowly; (3) Decarburization operation with weak oxygen supply at low temperature causes the temperature in the furnace to rise slowly, and the low temperature blowing temperature is 1250℃~1520℃, and the time is controlled within 150min±30min; (4) Strong oxygen supply rapid decarburization period, using the maximum oxygen flow rate to blow for 10-15 minutes, increasing the carbon-oxygen reaction and raising the furnace temperature to 1580-1600℃ tapping temperature. This stage is mainly based on sampling and phosphorus composition, and normal smelting operations are carried out until the tapping composition requirements are met; (5) After the carbon and phosphorus components meet the requirements of the steelmaking process, low-level power supply operation is carried out, the temperature is raised to 1660~1680℃, and the furnace bottom is sintered for 30~60min. This stage mainly adopts high-temperature sintering; (6) When replacing the taphole, observe the furnace bottom and furnace slope, make local padding, and track the furnace bottom temperature monitoring curve throughout the entire furnace service life.

2. The method for baking the bottom of an electric furnace for sintering hot metal according to claim 1, wherein: In the step (3), the blowing temperature is set at 1250° C. with a low oxygen flow rate, and the blowing time is controlled at 120 min.

3. The method for baking the bottom of an electric furnace for sintering hot metal according to claim 1, wherein: In the step (3), the blowing temperature is set at 1250° C. with a low oxygen flow rate, and the blowing time is controlled at 165 min.

4. The method for baking the bottom of an electric furnace for sintering hot metal according to any one of claims 1 to 3, characterized in that: In the step (4), the maximum oxygen flow rate is used for blowing for 12 minutes to increase the carbon-oxygen reaction and raise the temperature in the furnace to 1580-1600°C, the tapping temperature.

5. The method for baking the bottom of an electric furnace for sintering hot metal according to any one of claims 1 to 3, characterized in that: In the step (4), the maximum oxygen flow rate is used for blowing for 14 minutes to increase the carbon-oxygen reaction and raise the temperature in the furnace to 1580-1600°C, the tapping temperature.

6. The method for baking the bottom of an electric furnace for sintering hot metal according to any one of claims 1 to 3, characterized in that: In the step (5), the temperature is raised to 1660-1680°C and the furnace bottom is sintered for 43 minutes.

7. The method for baking the bottom of an electric furnace for sintering hot metal according to any one of claims 1 to 3, characterized in that: In the step (5), the temperature is raised to 1660-1680°C and the furnace bottom is sintered for 47 minutes.

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