Dynamic gas supply method for maintaining stability of converter bottom blowing mushroom head

Abstract

The invention discloses a dynamic gas supply method for maintaining the stability of a converter bottom blowing mushroom head, which comprises the following steps: 1) in the converter blowing process, controlling the natural gas supply set proportion eta 1 at the earlier stage of blowing to be 9-11%, controlling the eta 1 at the middle stage of blowing to be 10-13%, and controlling the eta 1 at the later stage of blowing to be 12-15%; 2) a lime powder injection stage: adjusting the flow Fm of the injected lime powder on the basis of the eta1 to a natural gas supply correction proportion eta2; 3) reading the natural gas supply flow and pressure of the bottom lance in the blowing process, and calculating the air permeability index alpha of the mushroom head according to a formula (3); and the final natural gas supply proportion eta 3 is adjusted according to the mushroom head air permeability alpha index. According to the method, the smelting stage, the ash spraying parameter and the mushroom head breathability factor serve as reference bases for adjusting natural gas, stable control over the mushroom head in the steelmaking process is achieved, and the mushroom head falling frequency is reduced; the stability of the mushroom head is improved, and accidents caused by instability of the mushroom head are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of converter smelting, in particular to a dynamic gas supply method for maintaining the stability of a converter bottom blowing mushroom head. Background Art

[0002] The bottom gun is very easy to be melted due to the oxygen blowing at the bottom of the furnace. The mushroom head at the end of the bottom gun is very important to protect the bottom gun. Once the mushroom head is unstable, it will cause the bottom gun to malfunction and affect production stability. For example, if the mushroom head is too small, it will cause the bottom gun to burn back or even leak steel; if the mushroom head is too large, it will block the bottom gun, cause flashback, and even burn the bottom blowing pipeline.

[0003] In order to prevent the bottom gun from being melted by high-temperature melt or fire point when blowing oxygen, natural gas is used to cool the bottom gun. The bottom gun is composed of a double sleeve, with the central tube spraying oxygen and the outer sleeve spraying natural gas. The bottom gun is cooled by the principle of heat absorption of natural gas high-temperature decomposition. The cooling effect of natural gas causes the molten steel at the end of the bottom gun to solidify, forming a metal mushroom head shaped like a mushroom. The mushroom head isolates the direct contact between the fire point or molten steel and the bottom gun, effectively protecting the bottom gun. The size of the mushroom head is in dynamic change during the smelting process, and its stability is mainly affected by multiple factors such as the proportion of cooling gas, radiation from the fire point, and superheat of the molten pool, and is in a dynamic thermal balance. In addition, the mushroom head is also affected by the ash injection flow rate during the blowing process. The larger the ash injection flow rate, the greater the cooling effect, and the mushroom head tends to grow. These factors change dynamically in actual steelmaking production, causing the size of the mushroom head to fluctuate. The static control method adopted for the cooling of the bottom gun, that is, the proportion of the bottom blowing cooling gas flow rate remains unchanged during the blowing process, which leads to poor stability of the mushroom head and is very easy to fall off. Therefore, the bottom blowing cooling gas supply control should dynamically adjust the cooling gas flow rate according to the converter smelting stage, mushroom head permeability and ash injection parameters, so as to quickly adjust the mushroom head state and maintain the stability of the mushroom head. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a dynamic gas supply method for maintaining the stability of the bottom blowing mushroom head of the converter, so as to effectively ensure the stability of the mushroom head.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: comprising the following steps: 1) during the converter blowing process, the natural gas supply setting ratio η1 is controlled at 9% to 11% in the early stage of blowing, 10% to 13% in the middle stage of blowing, and 12% to 15% in the late stage of blowing; 2) In the lime powder injection stage, based on the natural gas supply setting ratio η1 of the current blowing period in step 1), the lime powder injection flow rate F m Adjust to the natural gas supply correction ratio η2, the adjustment formula is shown in formula (2); η2=η1×(1.0-0.03×Fm ) (2) In formula (2), F m is the lime powder flow rate, kg / t / min; 3) Read the natural gas supply flow and pressure of the bottom gun during blowing, and calculate the mushroom head permeability index α by formula (3); α=1.43×(F / P) (3) In formula (3), α is a dimensionless index; F is the natural gas flow rate of the bottom gun, Nm 3 / min; P is the natural gas pressure of the bottom gun, MPa; According to the mushroom head permeability α index, the final natural gas supply ratio η3 is adjusted: If 6≤α≤9, the final natural gas supply ratio η3=η0 during the current blowing period; If 4.0≤α<5.5, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-1): η3=η0-(5.5-α)×0.8×10 -2 -1.4% (4-1); If 5.5≤α<6.0, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-2): η3=η0-(6-α)×2.8×10 -2 (4-2); If 9<α≤10, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-3): η3=η0+(α-9)×2.5×10 -2 (4-3); If 10<α≤12, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-4): η3=η0+(α-10)×0.75×10 -2 +2.5% (4-4); In the above formulas (4-1) to (4-4), in the lime powder injection stage η0=η2, and in the remaining stages η0=η1.

[0006] Furthermore, in step 1), the CO content in the flue gas is collected at time t after the converter blowing starts, and the real-time collected data is recorded as D0, t0, and the data before 3 to 8 seconds is recorded as D1, t1; k is calculated by formula (1) s , k s =arctan((D0-D1) / (t0-t1)) (1); If k s >45°, the converter is in the early stage of blowing; if ks <45°, the converter blowing enters the middle stage of blowing; if k s >135°, the converter blowing enters the late stage of blowing.

[0007] Furthermore, in step 1), the number of bottom guns at the bottom of the converter is 2 to 8, and the oxygen flow rate of the central tube of a single bottom gun is 25 to 40 Nm 3 / min.

[0008] Furthermore, in the step 2), the total flow rate of lime powder sprayed by all bottom guns is controlled at 2.0-4.0 kg / t / min.

[0009] The beneficial effects of the above technical solution are as follows: (1) The present invention overcomes the unstable permeability of the mushroom head caused by static control of natural gas, and provides a quantitative natural gas dynamic control method, which is conducive to real-time adjustment of the natural gas supply ratio and maintaining the stability of the mushroom head. (2) After the natural gas flow rate is dynamically adjusted by the present invention, it is helpful to reduce natural gas consumption and save costs. (3) The present invention reduces the risk of bottom gun backfire caused by too small mushroom head and the risk of bottom gun backfire caused by too large mushroom head, which is conducive to the long-term safe and stable operation of the bottom gun and bottom blowing smelting process.

[0010] The present invention uses the smelting stage, ash spraying parameters and mushroom head permeability factors as references for adjusting natural gas to achieve stable control of the mushroom head during the steelmaking process and reduce the frequency of mushroom head shedding; it can effectively improve the stability of the mushroom head, reduce production accidents caused by mushroom head instability, and solve the problems existing in the background technology. DETAILED DESCRIPTION

[0011] The present invention is further described in detail below in conjunction with specific implementation modes.

[0012] This dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head, in the converter steelmaking process, takes the blowing stage, the flow rate of lime powder sprayed at the bottom of the furnace and the permeability of the mushroom head of the bottom gun as the key factors for dynamically adjusting the cooling gas of the bottom gun, and dynamically controls the cooling gas flow rate through the real-time status of these three factors to achieve the purpose of maintaining the stability of the mushroom head. The natural gas control scheme as a whole follows the "low, high, high mode", and is dynamically adjusted according to other factors on this basis. First, the blowing process is divided into three stages according to the flue gas composition data of the blowing process, and the natural gas supply parameters are set according to the stages; then, the natural gas supply parameters are further adjusted according to the lime flow rate of the bottom ash spraying during the blowing process, that is, if the lime powder flow rate increases, the natural gas flow rate is appropriately reduced; finally, a natural gas dynamic control scheme is established through the permeability of the mushroom head to achieve the final value of the natural gas supply parameters. This dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head includes the following steps: 1) Natural gas supply setting ratio: The natural gas supply ratio η refers to the ratio of the natural gas flow rate sprayed from the outer casing of the bottom gun to the oxygen flow rate sprayed from the center tube, that is, η=F NG / F O2 , where F NG is the natural gas flow rate, unit Nm 3 / min,F O2 is the oxygen flow rate, unit Nm 3 / min. The natural gas supply setting ratio η1 in each blowing period of the blowing process adopts low, high and high modes: the natural gas supply setting ratio η1 in the early stage of blowing is controlled at 9% to 11%, the natural gas setting ratio η1 in the middle stage of blowing is controlled at 10% to 13%, and the natural gas setting ratio η1 in the late stage of blowing is controlled at 12% to 15%. The number of bottom guns at the bottom of the converter is 2 to 8, and the oxygen flow rate of the central tube of a single bottom gun is 25 to 40Nm 3 / min.

[0013] The three stages of the converter blowing period, the early stage, the middle stage and the late stage, are determined by the CO content of the converter flue gas: the CO content in the flue gas is collected at time t after the start of converter blowing, where t is in seconds and the CO content is in vol%; the real-time collected data is recorded as D0 and t0, and the first 5s data is recorded as D1 and t1; k is calculated by formula (1): s , k s =arctan((D0-D1) / (t0-t1)) (1); In formula (1), D0 is the CO content in the flue gas at the current time t, vol%; t0 is the current time t, s; D0 is the CO content in the flue gas at t0, vol%; t0 is 3 to 8 seconds before the current time t, preferably 5 seconds before the current time t.

[0014] If k s >45°, the CO content curve in the flue gas composition is in the rising stage, and the converter blowing is in the early stage of blowing; if k s <45° for more than 30s, the CO content curve in the flue gas composition is in a relatively stable stage, and the converter blowing enters the middle stage of blowing; if k s >135° for more than 30 seconds continuously, the CO content curve in the flue gas composition is in a descending stage, and the converter blowing enters the late stage of blowing.

[0015] The terminal temperature of the molten steel during converter blowing is controlled at 1580-1680°C.

[0016] 2) Natural gas supply correction ratio during lime powder injection: record the actual lime powder injection flow rate F during the blowing process mThe natural gas supply correction ratio η2 in the lime powder injection stage is adjusted based on the natural gas supply setting ratio η1 in each blowing period in step 1) according to the actual lime powder injection flow rate. The adjustment formula is shown in formula (2); η2=η1×(1.0-0.03×F m ) (2) In formula (2), η1 is the set ratio of natural gas supply in the current blowing period, %; η2 is the correction ratio of natural gas supply after the lime powder injection stage, %; F m is the lime powder flow rate, kg / t / min.

[0017] The lime powder is sprayed into the furnace from a bottom gun, and the total flow rate of the lime powder sprayed from the bottom gun is controlled at 2.0-4.0 kg / t / min.

[0018] If lime powder is not sprayed, before lime spraying or after lime spraying, the natural gas supply ratio is implemented according to the natural gas supply setting ratio η1 in step 1).

[0019] 3) Read the natural gas supply flow and pressure of the bottom gun during the converter blowing process, and calculate the mushroom head permeability index α by formula (3). α=1.43×(F / P) (3) In formula (3), α is a dimensionless index with a value range of 3 to 12; F is the natural gas flow rate of the bottom gun, Nm 3 / min; P is the natural gas pressure of the bottom gun, MPa.

[0020] According to the mushroom head permeability α index, the natural gas supply ratio in the current blowing period is adjusted to the final natural gas supply ratio η3: 3.1) If 6≤α≤9, the permeability of the mushroom head is in good condition, and the natural gas supply ratio η3=η0 during the current blowing period; 3.2) If 4.0≤α<5.5, the final natural gas supply ratio η3 of the current blowing period is adjusted according to formula (4-1), η3=η0-(5.5-α) ×0.8×10 -2 -1.4% (4-1); 3.3) If 5.5≤α<6.0, the final natural gas supply ratio η3 of the current blowing period is adjusted according to formula (4-2): η3=η0-(6-α)×2.8×10 -2 (4-2); 3.4) If 9<α≤10, the final natural gas supply ratio η3 during the current blowing period is adjusted according to formula (4-3): η3=η0+(α-9)×2.5×10 -2 (4-3); 3.5) If 10<α≤12, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-4): η3=η0+(α-10)×0.75×10 -2 +2.5% (4-4); In the formulas (4-1) to (4-4), η0 is the natural gas supply ratio before adjustment in this step. In the lime powder injection stage, η0=η2, and in the remaining stages, η0=η1.

[0021] Embodiment 1: The dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head is specifically described as follows.

[0022] Before blowing, the natural gas supply setting ratio η1 is set to 9%, 10% and 12% in the first, middle and last stages respectively, taking a bottom gun at the bottom of the furnace as an example. After the start of blowing, the natural gas supply setting ratio η1=9% in the early stage, the lime powder injection flow rate at the bottom of the furnace is 2.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2=8.46%; the bottom gun permeability index α=6.53, and the natural gas maintains η2 unchanged. When blowing enters the middle stage, the natural gas supply setting ratio is η1=10%, the bottom gun maintains the lime powder injection flow rate of 2.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2=9.40%; at a certain moment in the middle stage, the lime powder injection ends, the lime powder injection flow rate is 0, the natural gas supply ratio is adjusted to η1=10%, the bottom gun permeability index α=9.4, and is calculated and adjusted to the final natural gas supply ratio η3=11% according to formula (4-3). In the later stage of blowing, the natural gas supply ratio η1=12%, the lime powder injection flow rate is 0, the bottom gun permeability index α=10.8, and the final natural gas supply ratio η3=15.1% is calculated and adjusted according to formula (4-4). After the furnace smelting is completed, the permeability index α=0.88, the mushroom head has good permeability and returns to the stable range. During the whole process, the mushroom head did not fall off and remained stable.

[0023] Embodiment 2: The dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head is specifically described as follows.

[0024] Before blowing, the natural gas supply setting ratio η1 is set to 11%, 13% and 15% in the first, middle and last stages respectively, taking a bottom gun at the bottom of the furnace as an example. After the start of blowing, the natural gas supply setting ratio η1=11% in the early stage, the lime powder injection flow rate at the bottom of the furnace is 4.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2=9.68%; the bottom gun permeability index α=8.25, and the natural gas maintains η2 unchanged. When blowing enters the middle stage, the natural gas supply setting ratio η1=13%, the bottom gun maintains the lime powder injection flow rate of 4.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2=11.44%; at a certain moment in the middle stage, the lime spraying ends, the lime powder injection flow rate is 0, the natural gas ratio is adjusted to η1=13%, the bottom gun permeability index α=5.6, and is calculated and adjusted to the final natural gas supply ratio η3=11.88% according to formula (4-2). In the later stage of blowing, the natural gas supply ratio η1=15%, the lime powder injection flow rate is 0, and the bottom gun permeability index α=5.8. According to formula (4-2), the final natural gas supply ratio η3=14.44% is calculated and adjusted. After the furnace smelting is completed, the permeability index α=0.59. The next furnace smelting continues to adjust the natural gas ratio according to the stage, lime powder flow rate, and permeability index. During the whole process, the mushroom head did not fall off and remained stable.

[0025] Embodiment 3: The dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head is specifically described as follows.

[0026] Before blowing, the natural gas supply setting ratio η1 is set to 10%, 12% and 14% in the first, middle and last stages respectively, taking a bottom gun at the bottom of the furnace as an example. After the start of blowing, the natural gas supply setting ratio η1 = 10% in the early stage, the lime powder injection flow rate at the bottom of the furnace is 3.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2 = 9.1%; the bottom gun permeability index α = 4.0, according to formula (4-1) and adjusted to the final natural gas supply ratio η3 = 6.5%. When blowing enters the middle stage, the natural gas supply ratio is adjusted to η1 = 12%. At a certain moment in the middle stage, the lime spraying ends, the lime powder injection flow rate is 0, the natural gas supply setting ratio η1 = 12%, the bottom gun permeability index α = 5.5, calculated according to formula (4-2) and adjusted to the final natural gas supply ratio η3 = 10.6%. In the later stage of blowing, the natural gas supply ratio η1=14%, the lime powder injection flow rate is 0, the bottom gun permeability index α=6.3, and the natural gas ratio does not need to be adjusted. After the furnace smelting is completed, the permeability index α=0.72. The mushroom head has good permeability and returns to the stable range. During the whole process, the mushroom head did not fall off and remained stable.

[0027] Embodiment 4: The dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head is specifically described as follows.

[0028] Before blowing, the natural gas supply setting ratio η1 is set to 11%, 12% and 13% in the first, middle and last stages respectively, taking a bottom gun at the bottom of the furnace as an example. After the start of blowing, the natural gas supply setting ratio η1 = 11% in the early stage, the lime powder injection flow rate at the bottom of the furnace is 3.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2 = 10.01%; the bottom gun permeability index α = 8.2, and the natural gas ratio is no longer adjusted. When blowing enters the middle stage, the natural gas supply setting ratio η1 = 12%, the lime spraying ends at a certain moment in the middle stage, the lime powder injection flow rate is 0, the natural gas ratio is adjusted to η1 = 12%, the bottom gun permeability index α = 9.0, and the natural gas ratio is no longer adjusted. In the late stage of blowing, the natural gas supply setting ratio η1 = 13%, the lime powder injection flow rate is 0, the bottom gun permeability index α = 9.8, and the final natural gas supply ratio η3 = 15% is calculated and adjusted according to formula (4-3). After the furnace smelting was completed, the permeability index α was 0.82. The mushroom head had good permeability and returned to a stable range. During the whole process, the mushroom head did not fall off and remained stable.

[0029] Embodiment 5: The dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head is specifically described as follows.

[0030] Before blowing, the natural gas supply setting ratio η1 is set to 10%, 11% and 12% in the first, middle and last stages respectively, taking a bottom gun at the bottom of the furnace as an example. After the start of blowing, the natural gas supply setting ratio η1=10% in the early stage, the lime powder injection flow rate at the bottom of the furnace is 2.0kg / t / min, the natural gas supply correction ratio η2 is calculated according to formula (2) and adjusted to η2=9.4%; the bottom gun permeability index α=11.27, calculated according to formula (4-4) and adjusted to the final natural gas supply ratio η3=12.85%. When blowing enters the middle stage, the natural gas supply setting ratio η1=11%, the lime powder injection flow rate is 0, the bottom gun permeability index α=9.2, calculated according to formula (4-3) and adjusted to the final natural gas supply ratio η3=11.5%. In the late stage of blowing, the natural gas supply setting ratio η1=12%, the lime powder injection flow rate is 0, the bottom gun permeability index α=8.5, and the natural gas supply ratio does not need to be adjusted. After the furnace smelting was completed, the permeability index α was 0.88. The mushroom head had good permeability and returned to a stable range. During the whole process, the mushroom head did not fall off and remained stable.

[0031] Long-term application case statistics: A 260-ton converter in a steel plant in Hebei Province has produced more than 5,000 heats using bottom oxygen blowing and bottom powder spraying technology. According to statistics, the mushroom head falls off once in an average of 73 heats using the conventional method; the mushroom head falls off once in an average of 458 heats using this dynamic gas supply method. It can be seen that this dynamic gas supply method significantly improves the protective effect of the mushroom head on the bottom gun, and the life of the bottom gun is increased from a minimum of 45 heats to 1,450 heats; therefore, the use of this dynamic gas supply method effectively improves the stability of the mushroom head, which is conducive to the long-term stability of bottom blowing.

Claims

1. A dynamic gas supply method for maintaining the stability of the bottom blowing mushroom head of a converter, characterized in that: The steps include: 1) during the converter blowing process, the natural gas supply setting ratio η1 is controlled at 9% to 11% in the early stage of blowing, 10% to 13% in the middle stage of blowing, and 12% to 15% in the late stage of blowing; 2) In the lime powder injection stage, based on the natural gas supply setting ratio η1 of the current blowing period in step 1), the lime powder injection flow rate F m Adjust to the natural gas supply correction ratio η2, the adjustment formula is shown in formula (2); η2=η1×(1.0-0.03×F m ) (2) In formula (2), F m is the lime powder flow rate, kg / t / min; 3) Read the natural gas supply flow and pressure of the bottom gun during blowing, and calculate the mushroom head permeability index α by formula (3); α=1.43×(F / P) (3) In formula (3), α is a dimensionless index; F is the natural gas flow rate of the bottom gun, Nm 3 / min; P is the natural gas pressure of the bottom gun, MPa; According to the mushroom head permeability α index, the final natural gas supply ratio η3 is adjusted: If 6≤α≤9, the final natural gas supply ratio η3=η0 during the current blowing period; If 4.0≤α<5.5, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-1): η3=η0-(5.5-α)×0.8×10 -2 -1.4% (4-1); If 5.5≤α<6.0, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-2): η3=η0-(6-α)×2.8×10 -2 (4-2); If 9<α≤10, the final natural gas supply ratio η3 of the current blowing period is adjusted according to formula (4-3): η3=η0+(α-9)×2.5×10 -2 (4-3); If 10<α≤12, the final natural gas supply ratio η3 in the current blowing period is adjusted according to formula (4-4): η3=η0+(α-10)×0.75×10 -2 +2.5% (4-4); In the above formulas (4-1) to (4-4), in the lime powder injection stage η0=η2, and in the remaining stages η0=η1.

2. A natural gas dynamic gas supply method for maintaining the stability of the mushroom head of a bottom-blown converter according to claim 1, characterized in that: In the step 1, the CO content in the flue gas is collected at time t after the converter blowing starts, and the real-time collected data is recorded as D0 and t0, and the data before 3 to 8 seconds is recorded as D1 and t1; k is calculated by formula (1) s , k s =arctan((D0-D1) / (t0-t1)) (1); If k s >45°, the converter is in the early stage of blowing; if k s <45°, the converter blowing enters the middle stage of blowing; if k s >135°, the converter blowing enters the late stage of blowing.

3. A dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head according to claim 1, characterized in that: In the step 1, the number of bottom guns at the bottom of the converter is 2 to 8, and the oxygen flow rate of the central tube of a single bottom gun is 25 to 40 Nm 3 / min.

4. A dynamic gas supply method for maintaining the stability of the converter bottom blowing mushroom head according to claim 1, characterized in that: In the step 2), the total flow rate of lime powder sprayed by all bottom guns is controlled at 2.0-4.0 kg / t / min.