A furnace protecting method for increasing the thickness of the slag layer at the bottom of a converter

Abstract

The present invention discloses a furnace protecting method for increasing the thickness of the slag layer at the bottom of a converter. The method steps are as follows: (1) Adjust the temperature of the slag in the converter to 50 - 100°C above the melting point of the slag to keep the slag in a liquid state; (2) Tilt the converter to completely expose the bottom of the furnace to the air and stay for a period of time. During this period, nitrogen is blown into the bottom blowing element to cool the tuyere and form convective heat transfer to cool the bottom of the furnace, so as to generate a temperature gradient between the slag and the bottom of the furnace; (3) Adjust the converter to a vertical state and carry out slag sticking, so as to form a slag layer at the bottom of the furnace. This method completely exposes the bottom of the furnace to the air for a certain period of time by adjusting the angle of the converter, and accelerates the cooling of the bottom of the furnace through convection generated by the bottom blowing element; a reasonable temperature gradient is generated between the slag and the bottom of the furnace, and this temperature gradient is used to achieve an efficient and uniform slag sticking effect at the bottom of the furnace; this method can quickly and uniformly increase the thickness of the slag layer at the bottom of the converter, ensure a good bottom blowing effect, and extend the service life of the bottom blowing.

Description

Technical Field

[0001] The present invention relates to a converter lining protection method, in particular to a lining protection method for increasing the thickness of the slag layer at the bottom of a converter. Background Art

[0002] The maintenance of the bottom of a converter is one of the problems that steel smelting workers seek to solve, which directly affects the secondary blowing effect of converter smelting. At present, the main maintenance method is to use slag splashing and other means to delay the erosion of the furnace bottom and extend the service life of the furnace bottom and bottom blowing.

[0003] The converter slag splashing lining protection process has a good effect on maintaining the furnace lining, but there are major problems in maintaining the furnace bottom: in the early stage of slag splashing, the high-speed nitrogen jet impacts the high-temperature slag in the molten pool, which not only fails to maintain the furnace bottom but also causes erosion of the furnace bottom; during the slag splashing process, the converter is in a vertical state, and the furnace bottom is always immersed in the slag, and the temperature of the furnace bottom is close to that of the slag, so it is difficult for the slag to adhere to the furnace bottom; because it is difficult to achieve the slag sticking effect, a large amount of materials often need to be added, which in turn causes uneven thickness of the furnace bottom and blockage of the bottom blowing holes, greatly affecting the maintenance effect of the furnace bottom. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a lining protection method for increasing the thickness of the slag layer at the bottom of a converter, so as to quickly and uniformly increase the thickness of the slag layer at the bottom of the converter.

[0005] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: (1) Adjust the temperature of the slag in the converter to 50-100 °C above the melting point of the slag, and keep the slag in a liquid state;

[0006] (2) Tilt the converter so that the furnace bottom is completely exposed to the air and stay for a period of time. During this period, nitrogen is blown into the bottom blowing element to cool the tuyere and form convective heat transfer to cool the furnace bottom, so as to generate a temperature gradient between the slag and the furnace bottom;

[0007] (3) Adjust the converter to a vertical state and perform slag sticking, so as to form a slag layer on the furnace bottom.

[0008] Further, in the step (2), a temperature gradient of 100-150 °C is generated between the slag and the furnace bottom.

[0009] Further, in the step (1), the temperature of the slag is adjusted by adding materials and blowing air to cool down.

[0010] Further, in the step (3), the vertical state is maintained for 10-30 s for slag sticking.

[0011] The beneficial effects of adopting the above technical solutions are as follows: By adjusting the converter angle, the bottom of the furnace is completely exposed to the air for a certain period of time, and convection is generated by the bottom blowing element to accelerate the cooling of the furnace bottom; a reasonable temperature gradient is generated between the slag and the furnace bottom, and this temperature gradient is used to achieve an efficient and uniform slag sticking effect on the furnace bottom; the present invention can quickly and uniformly increase the thickness of the slag layer at the bottom of the converter, ensure a good bottom blowing effect, and extend the service life of the bottom blowing. Description of the Drawings

[0012] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0013] Figure 1 It is a schematic diagram of the converter bottom cooling of the present invention.

[0014] In the figure: 1 - slag; 2 - converter; 3 - nitrogen flow; 4 - heat exchange convection. Specific Embodiments

[0015] The method for protecting the furnace by increasing the thickness of the slag layer at the bottom of the converter adopts the following control process steps: (1) Preparation of liquid slag: After tapping the converter, there is initial slag left. According to the temperature and composition of the initial slag, the melting point of the slag is calculated, and the slag temperature reduction range is obtained. By means of control measures such as adding materials for temperature reduction and blowing air for temperature reduction, the temperature of the slag is adjusted to 50 - 100 °C above the melting point of the slag to keep the slag in a liquid state, so as to ensure uniform increase in the bottom thickness of the furnace and achieve a better maintenance effect. The formula for the melting point of the slag is shown in formula (Ⅰ):

[0016] Tm = 1738.41 + 2.63(%MgO) - 19.71(%TFe) + 1.08R (Ⅰ)

[0017] In formula (Ⅰ): Tm is the melting point of the slag, °C; %MgO is the mass percentage content of MgO in the slag; %TFe is the mass percentage content of Fe in the slag; R is the binary basicity of the slag.

[0018] When adding materials for temperature reduction, dolomite is used. The slag temperature reduction of dolomite is 43.7 °C / 1% (initial slag weight), that is, the feeding amount is calculated according to adding 1% of the initial slag weight of dolomite and the slag temperature reduction is 43.7 °C; when blowing air for temperature reduction, nitrogen is blown to reduce the slag temperature, and the temperature reduction coefficient is 30 °C / min; combining adding materials for temperature reduction and blowing air for temperature reduction, a temperature reduction plan is formulated, the nitrogen blowing time is determined, and the material addition amount is calculated.

[0019] (2) Furnace bottom cooling: Figure 1As shown, the converter 2 is tilted by adjusting its angle. It is preferably adjusted to an angle of 90°. The slag flows to the side wall position after the converter is laid flat, so that the bottom of the furnace is completely exposed to the air and stays for 3 - 5 minutes. During this period, a nitrogen gas stream 3 is blown in by the bottom blowing element, and the nitrogen gas stream 3 cools the tuyere and forms a heat exchange convection 4, thereby quickly cooling the bottom of the furnace, rapidly generating a temperature gradient between the slag and the bottom of the furnace, and the temperature difference between the slag and the bottom of the furnace is 100 - 150 °C.

[0020] (3)Slag sticking to the bottom of the furnace: After the temperature drop at the bottom of the furnace reaches the target, the converter is adjusted to the vertical state and maintained for 10 - 30 s for slag sticking. Due to the large temperature gradient between the bottom of the furnace and the slag, the slag layer at the bottom of the converter can be rapidly and evenly increased. The thickness of the slag layer increases by 50 - 100 mm, and the thickness deviation at each part is less than 20 mm; after slag sticking is completed, the remaining slag is poured out.

[0021] Example 1: The method for protecting the furnace by increasing the thickness of the slag layer at the bottom of the converter adopts the following specific process.

[0022] The end-point temperature of converter blowing is 1650 °C, the TFe content in the slag composition is 17.83%, the MgO content is 7.92%, and R is 2.73. According to the slag composition, the melting point of the slag is calculated to be 1411 °C.

[0023] 1500 kg of dolomite is added and nitrogen blowing is used to cool down for 3 minutes. By adjusting the angle of the converter to 90°, the bottom of the furnace is completely exposed to the air and stays for 3 minutes. The temperature of the slag is 1503 °C, which is 92 °C higher than the melting point, meeting the requirement that the slag is in a liquid state. During the 3-minute stay, the bottom blowing element blows in nitrogen to cool the tuyere and forms a convective heat transfer to quickly cool the bottom of the furnace. The temperature of the refractory material on the surface of the bottom of the furnace is 1403 °C, and the temperature difference between the slag and the refractory material at the bottom of the furnace is 100 °C. After the bottom of the furnace reaches the cooling effect, the converter is adjusted to the vertical state and maintained for 30 s for slag sticking. The newly added thickness of the slag layer at the bottom of the furnace in this process is 50 mm. The thickness deviation at each part is less than 20 mm.

[0024] Example 2: The method for protecting the furnace by increasing the thickness of the slag layer at the bottom of the converter adopts the following specific process.

[0025] The end-point temperature of converter blowing is 1635 °C, the TFe content in the slag composition is 17.06%, the MgO content is 7.53%, and R is 3.10. According to the slag composition, the melting point of the slag is calculated to be 1426 °C.

[0026] Add 2300 kg of dolomite, blow nitrogen to cool down for 3 min. By adjusting the converter angle to 90°, the bottom of the furnace is completely exposed to the air and stays for 5 min. The slag temperature is 1476 °C, 50 °C higher than the melting point, meeting the requirement that the slag is in a liquid state. During the 5-min stay, the bottom-blowing element blows nitrogen into the tuyere to cool the tuyere and form convective heat transfer to quickly cool the bottom of the furnace. The refractory temperature on the surface of the furnace bottom is 1326 °C, and the temperature difference between the slag and the refractory of the furnace bottom is 150 °C. After the bottom of the furnace reaches the cooling effect, adjust the converter to the vertical state and maintain it for 20 s for slag sticking. The newly added thickness of the slag layer at the bottom of the furnace in this process is 100 mm. The thickness deviation of each part is less than 20 mm.

[0027] Example 3: The furnace protection method for increasing the thickness of the slag layer at the bottom of the converter adopts the following specific process.

[0028] The temperature at the end of converter blowing is 1615 °C. The slag composition: the content of TFe is 17.32%, the content of MgO is 7.73%, and R is 2.97. According to the slag composition, the melting point of the slag is calculated to be 1420 °C.

[0029] Blow nitrogen to cool down for 3 min. By adjusting the converter angle to 90°, the bottom of the furnace is completely exposed to the air and stays for 3 min. The slag temperature is 1520 °C, 100 °C higher than the melting point, meeting the requirement that the slag is in a liquid state. During the 4-min stay, the bottom-blowing element blows nitrogen into the tuyere to cool the tuyere and form convective heat transfer to quickly cool the bottom of the furnace. The refractory temperature on the surface of the furnace bottom is 1400 °C, and the temperature difference between the slag and the refractory of the furnace bottom is 120 °C. After the bottom of the furnace reaches the cooling effect, adjust the converter to the vertical state and maintain it for 10 s for slag sticking. The newly added thickness of the slag layer at the bottom of the furnace in this process is 60 mm. The thickness deviation of each part is less than 20 mm.

Claims

1. A furnace lining protection method for increasing the thickness of the bottom slag layer in a converter, characterized in that, The method steps are as follows: (1) Adjust the temperature of the slag in the converter to 50-100 °C above the melting point of the slag and keep the slag in a liquid state; (2) Tilt the converter so that the bottom of the furnace is completely exposed to the air and stay for a period of time. During this period, nitrogen is blown into the bottom blowing element to cool the tuyere and form convective heat transfer to cool the bottom of the furnace, so as to generate a temperature gradient between the slag and the bottom of the furnace; (3) Adjust the converter to a vertical state and carry out slag sticking, so as to form a slag layer on the bottom of the furnace.

2. The furnace protecting method for increasing the thickness of the slag layer at the bottom of the converter according to claim 1, characterized in that: In the step (2), a temperature gradient of 100-150 °C is generated between the slag and the bottom of the furnace.

3. A furnace lining protection method for increasing the thickness of the bottom slag layer of a converter according to claim 1, characterized in that: In the step (1), the temperature of the slag is adjusted by adding materials and blowing air to lower the temperature.

4. A furnace protecting method for increasing the thickness of the slag layer at the bottom of a converter according to claim 1, 2 or 3, characterized in that: In the step (3), the vertical state is maintained for 10-30 s for slag sticking.

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