A method for predicting and controlling the converter smelting process using a CO concentration curve

Abstract

The present invention discloses a method for implementing a CO concentration curve to predict and pre-control a converter smelting process, comprising the following steps: a normal CO concentration curve is obtained for the entire smelting process, wherein the CO concentration is within 5% in the early stage of smelting, and when the CO concentration rises to 10%, the carbon-oxygen reaction period is entered, and when the CO concentration rises to more than 20%, the decarburization reaction is entered, in the middle stage of smelting, the decarburization rate is relatively stable, and the CO concentration changes relatively slowly, and in the late stage of smelting, the carbon content decreases and the CO concentration decreases, and the CO concentration changes in the converter smelting process. The decarburization speed is proportional and the FeO content in the slag is directly related to the amount of CO produced; if the CO concentration in the whole smelting process is abnormal, increase the amount of granular steel added after blowing for 1 minute, increase the amount of raw stone added after blowing for 1.5 minutes, reduce the oxygen pressure and oxygen flow, and raise the oxygen lance position by 0.1 to 0.2m; if scrap steel sticks to the front wall or the bottom of the furnace, resulting in rapid temperature rise in the early stage, causing slag overflow and splashing, the oxygen lance position should be raised by 1.4 to 1.6m, and the oxygen pressure should be 0.75 to 0.80Mpa.

Description

Technical Field

[0001] The present invention belongs to the technical field of converter smelting, and in particular relates to a method for implementing a CO concentration curve to predict and pre-control a converter smelting process. Background Art

[0002] At present, CO in converter gas comes from the following reactions: carbon is oxidized by contact with gaseous oxygen in the oxygen flow impact zone, carbon also reacts with oxygen dissolved in the metal, and carbon also reacts with iron oxide in the slag. When the carbon content in the molten pool is high, the vast majority of carbon oxidation products are CO rather than CO2. During the converter smelting process, the change in CO concentration is proportional to the decarburization rate.

[0003] If the CO content in the flue gas is high, it can be assumed that the FeO content in the slag is low or trending lower. While the FeO content in the slag is affected by many factors, the decarburization rate is the most critical factor in controlling the FeO content in the slag. The CaO-SiO2-FeO ternary phase diagram shows that the amount of FeO determines the properties of the slag liquid phase: the higher the FeO content, the higher the proportion of liquid phase in the slag. Furthermore, because the presence of FeO reduces the surface tension of the slag, the slag is prone to foaming. When the FeO content is too high, the high-speed reaction of CO gas easily generates foamy slag, which can cause splashing. Conversely, when the FeO content is too low, the solid phase ratio in the slag increases, making the slag viscous and causing dry-out. In severe cases, lime slagging becomes stagnant, and the molten steel is exposed to the surface.

[0004] During the dry dust removal process, during the low- and medium-iron consumption smelting process, carbon is not significantly oxidized in the initial stages due to the limitations of smelting conditions and elemental selective oxidation. The supplied O2 primarily oxidizes elements such as silicon, manganese, phosphorus, and iron in the molten iron. (The CO content is very low in the early stages, generally below 5%. When the CO content rises to around 10%, it indicates the transition to the carbon-oxygen reaction phase. When the CO content rises above 20%, it indicates the beginning of a significant carbon reaction, and decarburization gradually accelerates and becomes the primary reaction.) As the bath temperature rises and the various elements oxidize, decarburization conditions mature, carbon begins to oxidize significantly, and the CO concentration in the furnace gas rises rapidly. In the middle and later stages of the smelting process, under normal control, the decarburization rate is relatively stable, and the CO concentration changes relatively slowly. In the final and later stages of the smelting process, due to the significant decrease in the bath carbon content, the CO concentration in the coal gas also decreases significantly. The change in CO concentration during the converter smelting process is directly proportional to the decarburization rate, and the FeO content in the slag is directly related to the amount of CO generated. The CO concentration curve is divided into three stages throughout the blowing process, generally showing a "low-high-low" pattern, similar to a trapezoidal change. If abnormal slagging (such as overflow, back-drying, and splashing) occurs during the blowing process, the CO concentration in the furnace gas will also change abnormally.

[0005] Patent No. 201310310632.3 describes a method for operating the carbon monoxide lance position in a converter blowing process. The lance position can be adjusted rhythmically based on fluctuations in carbon monoxide concentration, which is a digital change combined with flame fluctuations. Proper operation can prevent slag drying and splashing throughout the process. However, the patent does not cover the CO guidance function throughout the blowing process.

[0006] Patent number 202110390468.6 A method for determining the temperature of a double-slag single pouring furnace in a converter using a converter dust removal system: The converter adopts dry electrostatic precipitator, and a gas recovery analyzer is installed in the converter gas recovery flue. The gas composition in the flue is analyzed by the gas recovery analyzer. When the CO concentration is detected to rise rapidly and the temperature is near the critical point of the carbon-phosphorus conversion temperature, the curve characteristic shows a rapid rise in the CO value. At this time, the time for lifting the gun and pouring the slag has been reached, and the furnace temperature is between 1350-1400°C. The data feedback from the converter dust removal system can be effectively used to determine the temperature of the molten pool in the furnace, solving the problem of selecting the timing of the single pouring furnace in the double-slag process. It only guides the timing and hit rate of the single pouring slag, and does not involve subsequent operations.

[0007] Patent number 202110274869.5 describes a method for stably controlling converter splashing and backdrying. Key technical requirements are quantified, and a prediction can be made when the C0 curve changes by more than 10% / 30 seconds. If the C0 curve rises by more than 10% in 30 seconds, backdrying can be predicted, and slag removal can be initiated by raising the lance or adding iron-containing material. If the C0 curve falls by more than 10% in 30 seconds, splashing can be predicted, and dolomite can be added for thickening the slag, followed by lowering the lance. This method is therefore easy to promote and implement, and its effectiveness can be guaranteed. However, the correlation between CO and backdrying and splashing in actual operation is weak, the prediction and control capabilities are weak, and the control plan is not specific and complete enough to be addressed. It also does not address the prediction and change of the CO concentration at the endpoint. Summary of the Invention

[0008] The object of the present invention is to provide a method for predicting and controlling a converter smelting process by using a CO concentration curve.

[0009] The technical solution adopted by the present invention to solve the technical problem is: a method for predicting and controlling the converter smelting process by using a CO concentration curve, comprising the following steps:

[0010] 1) The normal CO concentration curve of the whole smelting process: the CO concentration is within 5% in the early stage of smelting. When the CO concentration rises to 10%, it enters the carbon-oxygen reaction period. When the CO concentration rises to more than 20%, it enters the decarburization reaction. In the middle stage of smelting, the decarburization rate is relatively stable and the CO concentration changes relatively slowly. At the end of smelting, the carbon content decreases and the CO concentration decreases. During the converter smelting process, the change in CO concentration is proportional to the decarburization rate, and the FeO content in the slag is directly related to the amount of CO generated.

[0011] 2) According to step 1), if the CO concentration is abnormal throughout the entire smelting process and the temperature rises too quickly in the early stage of smelting, causing slag overflow and splashing, the amount of granular steel added is increased after blowing for 1 minute. After blowing for 1.5 minutes, the amount of raw stone added is increased, the oxygen pressure and oxygen flow are reduced, and the oxygen lance position is raised by 0.1-0.2m to slow the decarburization rate and gradually increase the FeO content in the slag. If the temperature rises too quickly in the early stage due to scrap steel sticking to the front wall or furnace bottom, causing slag overflow and splashing, the oxygen lance position is raised by 1.4-1.6m and the oxygen pressure is 0.75-0.80 MPa.

[0012] 3) The CO concentration is abnormal throughout the smelting process, and the temperature rise is too slow in the early stage of smelting, resulting in slag overflow and splashing. By promptly converting the lance to a low-oxygen lance with high oxygen pressure after the semi-oxygen period ends, the amount of slag material added in a single batch and the interval length can be reduced. After the slope of the CO concentration curve rises significantly, the lance is slowly raised to the normal lance position, and then the second batch of material is added;

[0013] 4) In the case of abnormal CO concentration in the whole smelting process, uneven heating in the early stage causes slag overflow and splashing. When the CO concentration drops, lower the oxygen lance position by 0.1-0.2m and increase the heating rate to avoid FeO accumulation. When the CO curve reaches the normal slope, restore the normal lance position.

[0014] 5) If the CO concentration is abnormal during the entire smelting process, and the CO concentration in the middle and late stages of blowing is ≥10% of the normal value, early intervention is carried out to raise the oxygen lance position by 0.1-0.2m each time. If the CO concentration is still higher than the normal value, the oxygen lance position is raised by increasing the range of raising the oxygen lance. The high lance position is controlled at 1.8-2.0m, the oxygen pressure at the lance is 0.88Mpa, and the lance is raised quickly and lowered slowly. The range of lowering the lance is controlled at 0.2-0.4m each time to maintain a balanced decarburization rate, eliminate slag dead zones and carbon component stratification, and improve slag melting effect;

[0015] 6) In the whole process of smelting, if the CO concentration is abnormal, slag overflow and splashing occur in the middle and late stages of blowing, and the oxygen lance position is raised by more than 0.2m in the middle stage of blowing, the oxygen pressure shall be increased by 0.01-0.015Mpa accordingly. When the CO concentration drops suddenly or with a large slope, the oxygen lance position shall be lowered by 0.1-0.2m each time. When the CO concentration drops by more than 10% and there are signs of slag overflow and splashing, the oxygen lance position shall be moved forward, raised once and lowered twice, and the amplitude shall be controlled within 300-500mm.

[0016] 7) The CO concentration is abnormal throughout the smelting process, and the CO concentration in the furnace rises rapidly in the later stage. 1 to 1.5 minutes before the end of blowing, the oxygen lance position is 2.3 to 2.5 meters, the working oxygen pressure is controlled at 0.90 to 0.93 MPa, the high oxygen lance position holding time is controlled to be ≤30 seconds, the lance lowering amplitude is controlled at 0.2 to 0.4 meters each time, and the holding time is controlled at 5 to 10 seconds each time.

[0017] The present invention has the following beneficial effects: based on a thorough study of the corresponding relationship between the variation law of the coal gas CO furnace gas composition and the blowing process, combined with mechanism research and the establishment of various typical models, the prediction and pre-control of the entire converter smelting process and the end point and full-process dynamic monitoring are realized, thereby achieving the transformation from the traditional empirical steelmaking method to digital steelmaking, replacing manual empirical steelmaking, and the comprehensive hit rate of the blowing process and the end point control is ≥95%; the steel material consumption is increased by ≥5.5%; the end point one-turn hit rate is >97.5%; the temperature loss caused by abnormal slagging conditions such as back drying, slag overflow, and splashing during the process is effectively avoided, and the end point temperature is increased by 10 to 30°C; it is ensured that the proportion of steel discharged directly from the furnace without turning over is >98%, and the blowing cycle is shortened by about 3 minutes; the method is not affected by equipment conditions and raw material conditions, does not require additional investment, is suitable for use by various steel companies, and makes converter steelmaking more scientific, digital, and intelligent. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the normal CO concentration curve.

[0019] Figure 2 This is the normal CO concentration "double platform" change curve.

[0020] Figure 3 This is a curve of CO concentration change when the temperature rises too quickly.

[0021] Figure 4 This is the CO concentration change curve when the temperature rises too slowly (1).

[0022] Figure 5 This is the CO concentration change curve when the temperature rises too slowly (2).

[0023] Figure 6 This is the CO concentration change curve when the temperature rises too slowly (3).

[0024] Figure 7 This is the CO concentration change curve in the middle and late stages of return drying.

[0025] Figure 8 It is a curve diagram of CO concentration change in the middle and late stages of splashing.

[0026] Figure 9 This is the CO concentration change curve of the later stage and the slagging of the pressure gun (I).

[0027] Figure 10 This is the CO concentration change curve of the later stage and the pressure gun slagging (2).

[0028] Figure 11 This is the CO concentration change curve of the later stage and the pressure gun slagging (3). DETAILED DESCRIPTION

[0029] The present invention will now be described in further detail.

[0030] A method for predicting and controlling a converter smelting process using a CO concentration curve includes the following steps:

[0031] Combined with the changing rules and characteristics of the CO concentration curve in the coal gas during the blowing process, the job operators are guided in the process slagging operation, process temperature and end point judgment, thereby improving the economic and technical indicators and efficiency of the converter. It can more effectively prevent and solve problems such as slag overflow, splashing, "back drying", and abnormal final slag condition during the converter steelmaking blowing process, further improving the smelting operation level and the application effect of intelligent blowing.

[0032] 1. Analysis of normal CO concentration curve of the whole smelting process

[0033] 1.1 During the dry dust removal process with medium and low iron consumption, carbon is not significantly oxidized in the initial stages due to the limitations of smelting conditions and elemental selective oxidation. The supplied O2 primarily oxidizes elements such as silicon, manganese, phosphorus, and iron in the molten iron. (The CO content is very low in the early stages, generally below 5%. When the CO content rises to around 10%, it indicates the transition to the carbon-oxygen reaction phase. When the CO content rises above 20%, it indicates the beginning of a significant carbon reaction, and decarburization gradually accelerates and becomes the primary reaction.) As the bath temperature rises and the various elements oxidize, decarburization conditions mature, carbon begins to oxidize significantly, and the CO concentration in the furnace gas rises rapidly. In the middle stages of the smelting process, under normal control, the decarburization rate is relatively stable, and the CO concentration changes relatively slowly. In the middle and later stages of the smelting process, due to the significant decrease in the bath carbon content, the CO concentration in the coal gas also decreases significantly. Therefore, during the converter smelting process, the change in CO concentration is directly proportional to the decarburization rate, and the FeO content in the slag is directly related to the amount of CO generated. The CO concentration change curve is divided into three stages during the entire blowing process. The overall trend is "low-high-low" and is close to a trapezoidal change. If there is abnormal slag formation during the blowing process (slag overflow, back drying, splashing, etc.), the CO concentration in the furnace gas will also change abnormally. The normal change trend of CO concentration is as follows: Figure 1 shown.

[0034] 1.2 After the silicon and manganese are oxidized, the decarburization reaction begins after a certain period of time (the CO concentration reaches the normal mid-term value range within 6 minutes), and the CO concentration curve shows two platforms as follows: Figure 2This is mainly a mode in which the physical heat (temperature, charge amount) and chemical heat (C, Si) of the molten iron are relatively low. The temperature rise rate of the molten pool is slow for a certain period of time, the FeO content in the slag is relatively high, the lime is fully melted, and the slag fluidity is relatively good.

[0035] 2. Analysis of abnormal CO concentration curve

[0036] 2.1.1 Rapid heating in the early stage causes slag overflow and splashing

[0037] The rapid rise of CO concentration curve in a certain period in the early stage (large slope and high peak) is a manifestation of high molten pool temperature (such as Figure 3 As shown), the decarburization rate increases rapidly during the continuous reduction of Si and Mn, the FeO in the slag is consumed, and the slag cannot be melted, which is prone to low-temperature slag overflow and splashing. Measures are taken: by increasing the amount of granular steel added after 1 minute of blowing and the amount of raw stone added after 1.5 minutes, reducing the oxygen pressure and oxygen flow, and raising the oxygen lance position by 0.1 to 0.2m compared to the normal level, the decarburization rate is slowed down and the FeO content in the slag is gradually increased. Another situation is that the front wall or the bottom of the furnace is abnormally sticky with scrap steel, which causes the scrap steel temperature control effect to fail. Measures are taken: If there are signs of low-temperature slag overflow and splashing, the oxygen lance should be operated quickly to a position of about 1.4 to 1.6m and an oxygen pressure of 0.75 to 0.80Mpa to expand the gas discharge channel, balance the molten pool reaction, and slow down the CO reaction rate. If low-temperature slag overflow is difficult to control, 100 to 200kg / time of limestone or lime can be added in small batches to perform slag pressing operations to shorten the transition period. After a smooth transition, the normal lance position is restored (the subsequent two control measures are consistent)

[0038] 2.1.2 Slow heating in the early stage leads to slag overflow and splashing

[0039] The CO concentration in the furnace gas fails to reach its peak value (about 6 minutes) due to the low temperature of the molten pool (such as Figure 4 、 5 As shown in the figure, decarburization reaction begins after Si and Mn decrease, but the decarburization speed is not high and slag emulsion cannot be formed. This phenomenon is particularly obvious in heats with low Si in molten iron, low temperature, high scrap ratio and more light scrap. Measures are taken: timely conversion to low lance position and high oxygen pressure operation for the end of semi-oxygen, and at the same time reducing the amount of slag material added in a single batch and the interval time. After the slope of the CO concentration curve rises significantly, the lance is slowly raised to the normal lance position, and then the second batch of materials is added at the right time.

[0040] 2.1.3 Uneven heating in the early stage causes slag overflow and splashing

[0041] The CO concentration reaches a small peak and then begins to decrease, as shown in Figure 6This process is mainly due to the mismatch between the reaction of carbon and oxygen in the molten iron and the real-time molten pool temperature (which is more obvious in heats with high molten iron temperature, high carbon and low silicon), resulting in a gap in the oxidation of carbon in the molten pool and the accumulation of excess iron oxide in the slag. The curve is characterized by a rapid drop in the CO volume fraction. Usually, when the CO volume fraction drops by more than 10%, slag overflow and even splashing will easily occur. Measures should be taken: ensure the timing, quantity and sequence of adding a batch of materials as required, effectively control the air blowing time after half oxygen is passed, ensure the initial heating rate and temperature saturation, lower the oxygen lance position by 0.1-0.2m when the CO concentration shows a significant large slope drop, increase the heating rate to avoid FeO accumulation, and restore the normal lance position when the CO curve reaches the normal slope change.

[0042] 2.2 Mid- and late-stage drying

[0043] In the middle and late stages of blowing (middle and early stages), the CO concentration shows a "hump" change, and the high point CO concentration is ≥10% of the normal value. Figure 7 As shown, a continuous increase in CO concentration in the furnace gas or a high level indicates that the slag is drying out. This is primarily due to poorly balanced carbon-oxygen reactions. The oxygen supply cannot meet the reaction requirements, consuming a large amount of iron oxide in the slag, causing the slag to dry out. During this drying period, the slag becomes viscous and even slag hardening occurs. The CO generated by carbon oxidation has reduced upward resistance, leading to a sharp increase in CO concentration. Measures to be taken: Preemptive intervention should be initiated every 0.1-0.2 m of drying out. If drying out becomes severe, increase the lance lift range. The high-oxygen lance position should be maintained at 1.8-2.0 m, with an oxygen pressure of approximately 0.88 MPa. A fast lift and slow lowering (0.2-0.4 m per lowering) approach should be employed. Maintaining a balanced decarburization rate eliminates slag dead zones and carbon stratification, improving slag melting efficiency. However, avoid operating the lance at a high position for extended periods (≥20 seconds).

[0044] 2.3 Overflow and splashing in the middle and late stages

[0045] During normal smelting, the carbon-oxygen reaction is relatively stable. When the CO concentration suddenly decreases or decreases with a large slope, with an amplitude of ≥10%, it indicates that slag overflow and splashing are likely to occur. The reasons for slag overflow and splashing are that the mid-term gun position is too high for a long time or the oxygen pressure is too low. In addition, operational reasons cause the slag to be dry or severely dried, and then the gun is lifted and the slag treatment time is long, the impact depth is insufficient, and the carbon-oxygen reaction is restricted, resulting in FeO accumulation in the slag (one is to increase the oxygen content carrier and the other is to reduce the slag surface tension). In addition, the concentrated addition of slag causes the molten pool to cool suddenly, and the early scrap steel clumps are dispersed, causing the molten pool to cool suddenly, etc., which leads to the inhibition of CO reaction. The above situation leads to the restriction of normal, high-speed and intense CO reaction, resulting in imbalance or delay, sudden and rapid drop of CO concentration and accumulation of FeO. When the temperature of the molten pool changes and rises again, the CO reaction is intense again and a large amount of CO gas is discharged in a short time, which will cause continuous slag overflow and splashing. Measures should be taken: ① In the middle of blowing, the oxygen gun position and oxygen pressure should be coordinated reasonably. When the gun is raised more than 0.2m, the oxygen pressure should be increased accordingly (0.01~0.015Mpa), to ensure reasonable impact depth and oxygen supply intensity, maintain a reasonable decarburization rate and avoid abnormal fluctuations in CO concentration. ② When the CO concentration suddenly or greatly increases, the CO concentration should be reduced. When the slope decreases, lower the gun in time (lower the gun 0.1~0.2m each time, the lowest gun position in the middle period -0.1~0.2m) to intervene and effectively control the CO concentration to decrease by no more than 6~8%. ③ When the CO concentration decreases by more than 10% and there are signs of slag overflow and splashing, remember not to lower the gun directly for control. Rapid flow gun operation is required (raise 1 and lower 2, with an amplitude controlled at 300~500mm). First, the high oxygen gun position destroys the foam slag layer to accelerate gas discharge, and then reduces the acceleration of FeO consumption in the slag. When the situation is serious, the frequency of gun channeling needs to be increased and a small amount of lime or limestone needs to be used to press the slag to improve the overall effect.

[0046] In the later stage, the CO reaction in the furnace gradually weakened or the high lance position and low oxygen pressure slag adjustment operation were continued, and the iron oxide content in the slag showed an increasing state. The oxygen lance was lowered too quickly and the timing was inappropriate during the lance adjustment process, and the steel-slag stirring in the molten pool was instantly enhanced (the carbon content was around 0.50-0.20%). The CO concentration suddenly and rapidly rose, and the carbon in the molten pool reacted with the excess iron oxide in the slag, causing the slag to overflow and splash. Measures to be taken: "High lance and high pressure" operation is adopted about 1-1.5 minutes before the end of blowing. According to the actual slag conditions, the upper limit of the lance position can be 2.3-2.5m, the working oxygen pressure is controlled at 0.90-0.93Mpa, and the high lance position holding time is controlled to be ≤30s. (The amplitude of each lance lowering is controlled at 0.2-0.4m, and the holding time is controlled at 5-10s. The high lance position holding and adjustment time are flexibly controlled according to the actual slag conditions and the ignition lance position.

[0047] 2.4 The slag is not good in the later stage and the pressure gun

[0048] In the later stage and during the gun pressure process, the CO concentration did not show a downward trend, but instead remained at a high level, and showed abnormal trends such as rising instead of falling (such as Figure 9-11 As shown), the main reason is that the blowing process is poorly controlled, the slag is not completely melted, not well melted, and not thoroughly melted, the decarburization rate is not balanced enough, and the composition of the molten pool is uneven. During the gun pressing process, carbon is mixed and reacted again, and the CO concentration curve is abnormal. This phenomenon is prone to abnormal conditions such as excessive stickiness of the poured slag, incomplete melting, high P, and inability to measure temperature and take samples. Measures to be taken: If such a situation occurs before gun pressing, adjust the slag with high gun and high pressure before pressing the gun. If this situation occurs during and after gun pressing, lift the gun and turn off the oxygen, then lower the gun for a second point blowing and then pour the furnace, so as to move the processing checkpoint forward and effectively control the duration and number of point blowing.

[0049] The present invention is not limited to the above-mentioned embodiments. Anyone should be aware that any structural changes made under the guidance of the present invention, and any technical solutions that are the same or similar to those of the present invention, fall within the scope of protection of the present invention.

[0050] The technology, shape, and structure not described in detail in the present invention are all well-known technologies.

Claims

1. A method for predicting and controlling the converter smelting process using a CO concentration curve, characterized in that: The following steps are involved: 1) The normal CO concentration curve of the whole smelting process: the CO concentration is within 5% in the early stage of smelting. When the CO concentration rises to 10%, it enters the carbon-oxygen reaction period. When the CO concentration rises to more than 20%, it enters the decarburization reaction. In the middle stage of smelting, the decarburization rate is relatively stable and the CO concentration changes relatively slowly. At the end of smelting, the carbon content decreases and the CO concentration decreases. During the converter smelting process, the change in CO concentration is proportional to the decarburization rate, and the FeO content in the slag is directly related to the amount of CO generated. 2) According to step 1), if the CO concentration is abnormal throughout the entire smelting process and the temperature rises too quickly in the early stage of smelting, causing slag overflow and splashing, the amount of granular steel added is increased after blowing for 1 minute. After blowing for 1.5 minutes, the amount of raw stone added is increased, the oxygen pressure and oxygen flow are reduced, and the oxygen lance position is raised by 0.1-0.2m to slow the decarburization rate and gradually increase the FeO content in the slag. If the temperature rises too quickly in the early stage due to scrap steel sticking to the front wall or furnace bottom, causing slag overflow and splashing, the oxygen lance position is raised by 1.4-1.6m and the oxygen pressure is 0.75-0.80 MPa. 3) The CO concentration is abnormal throughout the smelting process, and the temperature rise is too slow in the early stage of smelting, resulting in slag overflow and splashing. By promptly converting the lance to a low-oxygen lance with high oxygen pressure after the semi-oxygen period ends, the amount of slag material added in a single batch and the interval length can be reduced. After the slope of the CO concentration curve rises significantly, the lance is slowly raised to the normal lance position, and then the second batch of material is added; 4) In the case of abnormal CO concentration in the whole smelting process, uneven heating in the early stage causes slag overflow and splashing. When the CO concentration drops, lower the oxygen lance position by 0.1-0.2m and increase the heating rate to avoid FeO accumulation. When the CO curve reaches the normal slope, restore the normal lance position. 5) If the CO concentration is abnormal during the entire smelting process, and the CO concentration in the middle and late stages of blowing is ≥10% of the normal value, early intervention is carried out to raise the oxygen lance position by 0.1-0.2m each time. If the CO concentration is still higher than the normal value, the oxygen lance position is raised by increasing the range of raising the oxygen lance. The high lance position is controlled at 1.8-2.0m, the oxygen pressure at the lance is 0.88Mpa, and the lance is raised quickly and lowered slowly. The range of lowering the lance is controlled at 0.2-0.4m each time to maintain a balanced decarburization rate, eliminate slag dead zones and carbon component stratification, and improve slag melting effect; 6) In the whole process of smelting, if the CO concentration is abnormal, slag overflow and splashing occur in the middle and late stages of blowing, and the oxygen lance position is raised by more than 0.2m in the middle stage of blowing, the oxygen pressure shall be increased by 0.01-0.015Mpa accordingly. When the CO concentration drops suddenly or with a large slope, the oxygen lance position shall be lowered by 0.1-0.2m each time. When the CO concentration drops by more than 10% and there are signs of slag overflow and splashing, the oxygen lance position shall be moved forward, raised once and lowered twice, and the amplitude shall be controlled within 300-500mm. 7) The CO concentration is abnormal throughout the smelting process, and the CO concentration in the furnace rises rapidly in the later stage. 1 to 1.5 minutes before the end of blowing, the oxygen lance position is 2.3 to 2.5 meters, the working oxygen pressure is controlled at 0.90 to 0.93 MPa, the high oxygen lance position holding time is controlled to be ≤30 seconds, the lance lowering amplitude is controlled at 0.2 to 0.4 meters each time, and the holding time is controlled at 5 to 10 seconds each time.

Images