A control method based on a converter operation model under high scrap ratio conditions

Abstract

The present application relates to the technical field of converter steelmaking, and particularly relates to a control method based on a converter operation model under high scrap steel ratio conditions. According to relevant information such as scrap steel, molten iron, charging and oxygen supply of the present heat under high scrap steel ratio conditions, the model performs heat balance calculation and material balance calculation, obtains the scrap steel melting point interval and the converter bath temperature rising curve under the present heat conditions, and then, in combination with the actual CO content change in the blowing of the present heat, timely and timely operation adjustment of the charging mode, oxygen lance blowing position, blowing oxygen flow and converter bottom blowing flow under high scrap steel ratio conditions is performed, so that the abnormal phenomena such as "spattering" and "returning dry" in the blowing process are effectively avoided, efficient and stable operation of the blowing process is realized, the metal yield and production efficiency are improved, and the present application has remarkable economic benefits and promotion prospects.

Description

Technical Field

[0001] This invention relates to the field of converter steelmaking technology, and specifically to a control method based on a converter operation model under high scrap ratio conditions. Background Technology

[0002] With the increasing emphasis on reducing carbon emissions in steel products, controlling carbon emissions from integrated steelmaking processes has become a hot research topic. In integrated steelmaking, over 80% of carbon emissions originate from pre-ironmaking processes such as coking, sintering, and blast furnaces—key processes for carbon reduction. For integrated converter steelmaking processes, increasing the scrap ratio and decreasing the hot metal ratio are highly feasible and will be important measures and means for reducing carbon emissions in the future.

[0003] Scrap steel is a recyclable ferrous resource. Increasing the scrap steel ratio helps reduce environmental pollution and overall energy consumption in the steel industry, resulting in significant economic, environmental, and social benefits. Domestic and international steel companies have conducted extensive research on increasing the scrap steel ratio in converters, with key methods including scrap preheating, adding reheating agents to the converter, and improving secondary combustion rates.

[0004] Currently, more efficient utilization of scrap steel has become an important development direction for converter steelmaking. As one of the main raw materials for converter smelting, scrap steel, due to its cold material properties, has a significant impact on the stable control of the converter molten pool temperature and the efficient and smooth operation of converter production during its melting process. After being added, scrap steel absorbs some heat. As the molten pool temperature rises, the scrap steel gradually melts. During melting, it absorbs more heat per unit time, causing significant fluctuations in the molten pool temperature, affecting the normal heating curve, and significantly impacting the blowing operation. If accurate judgment and timely corresponding operational measures are not taken, it will directly affect the slag formation effect and the normal blowing process, and may even cause significant "splashing" or "re-drying" phenomena, posing quality and safety hazards to production.

[0005] Currently, research on scrap steel melting in converters is relatively scarce. Most methods for increasing the scrap steel ratio originate from the production practices of steel enterprises. However, due to differences in converter capacity, smelting processes, and other factors among different types of steel plants, the same scrap steel ratio increasing methods or processes also exhibit varying effects in different steel plants. Existing technologies also have relatively few studies on the effects of scrap steel ratio changes on converter blowing, charging, temperature, and metal recovery, limiting the efficient utilization of scrap steel in converters. Therefore, converter operation control methods under high scrap steel ratio conditions urgently need to be researched and resolved. Summary of the Invention

[0006] To address the technical problem of ineffective utilization of scrap steel under high scrap ratio conditions, this invention provides a control method based on a converter operation model under high scrap ratio conditions. This method can achieve efficient and stable operation of the converter blowing process, improve metal yield and production efficiency, and effectively avoid abnormal phenomena such as "splashing" and "re-drying" during the blowing process.

[0007] This invention provides a control method based on a converter operation model under high scrap ratio conditions, comprising the following steps:

[0008] S1. Based on the type and proportion of scrap steel added, calculate the time T from the start of melting to complete melting of the scrap steel through heat balance. T = t1 - t0, where t0 is the time when the scrap steel starts to melt and t1 is the time when the scrap steel is completely melted.

[0009] S2. Calculate the converter molten pool temperature curve based on heat balance and material balance;

[0010] S3. Based on time T, the converter molten pool temperature rise curve, and the instantaneous CO content in the converter flue gas, adjust the charging mode, oxygen lance position, oxygen flow rate, and converter bottom blowing flow rate.

[0011] S4. After all the scrap steel has melted at time t1, the system switches to normal control mode operation.

[0012] Furthermore, in step S1, the scrap steel used is first classified. Depending on the specific circumstances of each enterprise, the types of scrap steel added include light and thin scrap, medium-sized scrap steel, heavy scrap steel, baled scrap, briquettes, steel slag, dust balls, carbon scrap steel, alloy scrap steel, and pig iron blocks. At the same time, the size, dimensions, and block size of the scrap steel are strictly regulated; and the specific weight and proportion of each type of scrap steel are added strictly according to the process specifications. Because the composition and block size of each type of scrap steel are different, their melting points, heat absorption, and melting rates in the molten pool are also different. Only by classifying the scrap steel in a standardized manner, adding it according to the process requirements, and calculating the physicochemical properties of each type of scrap steel separately, can the total impact of the added scrap steel on smelting be calculated more accurately.

[0013] Furthermore, in step S2, the factors for calculating heat balance and material balance include molten iron conditions, feeding conditions, and oxygen supply conditions; molten iron conditions include molten iron composition and temperature; feeding conditions include scrap steel type and proportion, slag material weight and amount added; oxygen supply conditions include oxygen supply time, oxygen consumption, and exothermic oxidation reactions of various elements.

[0014] Furthermore, the main component of the converter flue gas produced by the carbon-oxygen reaction during converter blowing is CO, and the oxidation products of the carbon-oxygen reaction are mostly CO rather than CO2. Therefore, the CO content value detected by the gas analyzer indirectly reflects the rate of the carbon-oxygen reaction. In oxygen converters, changes in the emitted CO gas can serve as a reference for measuring the operational stability of "splashing" and "re-drying" during the blowing process. Similarly, the CO content in the flue gas can guide and predict the carbon-oxygen reaction during the blowing process, effectively ensuring stable control of the blowing operation. When a high proportion of scrap steel reaches its melting point, a concentrated endothermic phenomenon occurs, causing an inflection point (reduced heating rate) in the converter molten pool temperature rise curve. Due to differences in the amount of scrap steel added and the proportions of various scrap steels, the timing and duration of the inflection point in the converter molten pool temperature rise curve also vary accordingly. Similarly, changes in the temperature rise curve reflect changes in the carbon-oxygen reaction within the furnace, resulting in a corresponding inflection point in the CO content curve (a decrease in the instantaneous CO content). The real-time CO content changes displayed on the instrument can serve as a reference for the start of melting of high-proportion scrap steel.

[0015] Increasing the proportion of scrap steel slows down the rate of molten pool heating, making it difficult to raise the temperature. This increases the viscosity of the metal inside the furnace, leading to a decrease in the rate of reaction and heat transfer in the molten pool, thus increasing the melting time of the scrap steel. When a high proportion of scrap steel begins to melt, it absorbs a relatively concentrated amount of heat, reducing the rate of molten pool heating and the rate of carbon-oxygen reaction in the furnace, resulting in a lower instantaneous CO content. At this point, the oxygen lance height should be appropriately lowered to accelerate the carbon-oxygen reaction and avoid low-temperature splashing caused by excessive low-temperature slag. Based on the time T it takes for the scrap steel to reach its melting point, the converter molten pool heating curve, and the instantaneous CO content in the converter flue gas, adjust the charging mode, oxygen lance height, oxygen flow rate, and converter bottom blowing flow rate.

[0016] Furthermore, in step S3, the method for adjusting the feeding mode is as follows: due to the increase in the proportion of scrap steel and the relatively low temperature of the molten pool, it is not easy to concentrate the feeding. Therefore, a "multi-batch, small-volume" feeding method is adopted to alleviate the temperature drop caused by concentrated feeding. At the same time, it is ensured that the last batch of material is fed 2 minutes before the t0 time of the converter molten pool temperature curve.

[0017] Furthermore, in step S3, the method for adjusting the oxygen lance blowing position is to appropriately lower the oxygen lance blowing position to accelerate the carbon-oxygen reaction rate, initially using a low lance position and low flow rate mode; before time t1, the height H of the oxygen lance blowing position... (t) Calculate according to the following formula, H0 represents the original normal gun position height at that moment; after time t1, the oxygen lance blowing gun position returns to normal.

[0018] Furthermore, in step S3, the method for adjusting the oxygen flow rate in the refining process is as follows: before time t1, the oxygen flow rate F(t) is calculated using the following formula: F0 represents the normal oxygen flow rate at that time; the oxygen flow rate returns to normal after time t1.

[0019] Furthermore, in step S3, the method for adjusting the converter bottom blowing flow rate is to appropriately reduce the bottom blowing flow rate based on the scrap ratio to reduce the temperature drop caused by bottom blowing; before time t1, the converter bottom blowing flow rate W (t) Calculate according to the following formula, W0 represents the normal bottom blowing flow rate of the converter at that time, and η represents the percentage content of scrap steel added in that heat. The bottom blowing flow rate of the converter returns to normal after time t1.

[0020] Furthermore, in step S4, after the converter cycle is completed, the model data information is fed back to the database for self-learning correction.

[0021] The principle of this invention is that the smelting heat of converter steelmaking comes from the physical and chemical heat of molten iron. After increasing the scrap ratio in the converter, the heat balance and temperature change of the converter need to be considered first. Through model construction, combined with material balance and heat balance calculations, the time when the scrap reaches the melting point and the time from the start of melting to the end of melting of various scraps, as well as the temperature rise curve of the converter molten pool, can be predicted. Referring to the changes in CO content during the blowing process, the oxygen lance control position, oxygen flow rate, charging system and other related processes and parameters can be adjusted in a timely manner to achieve stable and efficient operation of the converter under high scrap ratio conditions.

[0022] The beneficial effects of this invention are as follows: Based on the specific information of scrap steel, molten iron, charging, and oxygen supply for this heat under high scrap steel ratio conditions, the model performs heat balance calculations and material balance calculations to obtain the scrap steel melting point range and converter molten pool temperature rise curve under these conditions. Combined with the actual CO content changes during the blowing process, timely and appropriate adjustments are made to the charging mode, oxygen lance position, blowing oxygen flow rate, and converter bottom blowing flow rate under high scrap steel ratio conditions. This effectively avoids abnormal phenomena such as "splashing" and "re-drying" during the blowing process, achieving efficient and stable operation of the blowing process, improving metal yield and production efficiency, and demonstrating significant economic benefits and promising prospects for promotion. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the control method flow of a specific embodiment of the present invention. Detailed Implementation

[0025] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0026] like Figure 1 This invention illustrates a control method for a converter operation model under high scrap ratio conditions, comprising the following steps:

[0027] S1. Based on the type and proportion of scrap steel added, the time T from the start of melting to complete melting of the scrap steel is calculated through heat balance. T = t1 - t0, where t0 is the time when the scrap steel starts to melt and t1 is the time when the scrap steel is completely melted. The types of scrap steel added include light and thin scrap, medium scrap steel, heavy scrap steel, baled scrap, briquettes, steel slag, dust and mud balls, carbon scrap steel, alloy scrap steel, and pig iron blocks.

[0028] S2. Calculate the converter pool temperature rise curve based on heat balance and material balance. The factors for heat balance and material balance calculation include molten iron conditions, charging conditions and oxygen supply conditions. Molten iron conditions include molten iron composition and temperature. Charging conditions include scrap steel type and proportion, slag material weight and amount added. Oxygen supply conditions include oxygen supply time, oxygen consumption and exothermic oxidation reactions of various elements.

[0029] S3. Based on time T, the converter molten pool temperature rise curve, and the instantaneous CO content in the converter flue gas, adjust the charging mode, oxygen lance position, oxygen flow rate, and converter bottom blowing flow rate.

[0030] The method to adjust the feeding mode is to adopt a "multi-batch, small-volume" feeding method to ensure that the last batch of material is fed 2 minutes before the t0 time of the converter molten pool heating curve.

[0031] The method for adjusting the oxygen lance blowing position is as follows: before time t1, the height H of the oxygen lance blowing position is... (t) Calculate according to the following formula, H0 represents the normal lance position height at that moment; after time t1, the oxygen lance blowing position returns to normal.

[0032] The method for adjusting the oxygen flow rate in the refining process is as follows: before time t1, the oxygen flow rate F(t) is calculated using the following formula: F0 represents the normal oxygen flow rate for refining at that time; the oxygen flow rate for refining returns to normal after time t1.

[0033] The method for adjusting the converter bottom blowing flow rate is as follows: before time t1, the converter bottom blowing flow rate W... (t) Calculate according to the following formula, W0 represents the normal converter bottom blowing flow rate at that time, and η represents the percentage content of scrap steel added in that heat; the converter bottom blowing flow rate returns to normal after time t1.

[0034] S4. After all the scrap steel has melted at time t1, the system switches to the normal control mode. After the converter heat is completed, the model data information is fed back to the database for self-learning and correction.

[0035] Example 1

[0036] Example 1 includes furnace batch 1: molten iron temperature at the furnace inlet is 1362℃; molten iron composition: C: 4.36%; Si: 0.52%; Mn: 0.36%; P: 0.086%; S: 0.030%; scrap steel + molten iron addition amount is (173+58)t; scrap steel structure: light and thin scrap + medium scrap + heavy scrap + baled scrap + briquettes + pig iron blocks = 5+8+12+6+12+15 = 58t; main slag-forming materials and alloy addition amounts: lime 22kg / t, dolomite 7.2kg / t, ore 6.7kg / t; oxygen consumption 48m³. 3 The model calculates the time when the scrap steel reaches its melting point (t0 = 7.6 min), the end of complete melting (t1 = 11.8 min), and the melting time T (T = t1 - t0 = 11.8 - 7.6 = 4.2 min). Real-time adjustments are made based on the molten pool heating curve and the actual instantaneous CO content changes in the converter flue gas during this heat. The last batch of material is added before 5.6 min (two minutes before t0); before time t1, the oxygen lance blowing position is controlled and adjusted to... Before time t1, the control of the blowing oxygen flow rate was adjusted to... Before time t1, the converter bottom blowing flow rate control was adjusted to... After 11.8 minutes, the system switched to normal control mode. The blowing process was smooth, with no splashing or back-drying, and the endpoint was hit on the first attempt.

[0037] Example 2

[0038] Furnace 2: Inlet temperature of molten iron 1336℃; molten iron composition: C: 4.28%; Si: 0.46%; Mn: 0.31%; P: 0.078%; S: 0.026%; Scrap steel + molten iron addition: (171 + 60)t; Scrap steel structure: light and thin scrap + medium scrap + heavy scrap + baled scrap + briquettes + pig iron blocks = 5 + 8 + 12 + 6 + 9 + 18 = 58t; Main slag-forming materials and alloy additions: lime 23kg / t, dolomite 7.8kg / t, ore 7.7kg / t; Oxygen consumption: 46m³ 3 The model calculates the time when the scrap steel reaches its melting point (t0 = 6.2 min), the end of complete melting (t1 = 10.6 min), and the melting time T (T = t1 - t0 = 10.6 - 6.2 = 4.4 min). Real-time adjustments are made based on the molten pool heating curve and the actual instantaneous CO content changes in the converter flue gas during this heat. The last batch of material is added before 4.2 min (two minutes before t0); before time t1, the oxygen lance blowing position is controlled and adjusted to... Before time t1, the control of the blowing oxygen flow rate was adjusted to... Before time t1, the converter bottom blowing flow rate control was adjusted to...

[0039] 60 / (171+60)≈536m 3 / h; After 10.6 minutes, it switches to normal control mode operation. The blowing process is stable, with no splashing or back-drying, and the endpoint is hit on the first attempt. After the converter cycle is completed, the model data information is fed back to the database for self-learning and correction.

[0040] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A control method based on a model of converter operation under high scrap ratio conditions, characterized in that, Includes the following steps: S1. Based on the type and proportion of scrap steel added, calculate the time T from the start of melting to complete melting of the scrap steel through heat balance. T = t1 - t0, where t0 is the time when the scrap steel starts to melt and t1 is the time when the scrap steel is completely melted. S2. Calculate the converter molten pool temperature curve based on heat balance and material balance; S3. Based on time T, the converter molten pool temperature rise curve, and the instantaneous CO content in the converter flue gas, adjust the charging mode, oxygen lance position, oxygen flow rate, and converter bottom blowing flow rate. S4. After all the scrap steel has melted at time t1, the system switches to normal control mode operation. In step S3, The method to adjust the feeding mode is to adopt a "multi-batch, small-volume" feeding method to ensure that the last batch of material is fed 2 minutes before the t0 time of the converter molten pool heating curve. The method for adjusting the oxygen lance blowing position is as follows: before time t1, the height H of the oxygen lance blowing position is... （t） Calculate H using the following formula. （t） =H0-300× H0 represents the original normal gun position height at that moment; after time t1, the oxygen lance blowing gun position returns to normal. The method for adjusting the oxygen flow rate in the smelting process is as follows: before time t1, the oxygen flow rate F(t) is calculated using the following formula: F(t) = F0 - F0 × F0 represents the normal oxygen flow rate at that time; the oxygen flow rate returns to normal after time t1. The method for adjusting the converter bottom blowing flow rate is as follows: before time t1, the converter bottom blowing flow rate W... （t） Calculate W using the following formula. （t） =W0-W0× η, W0 is the normal converter bottom blowing flow rate at that time, and η is the percentage content of scrap steel added in that heat; the converter bottom blowing flow rate returns to normal after time t1.

2. A control method based on a model of converter operation under high scrap ratio conditions as claimed in claim 1, characterized in that, In step S1, the types of scrap steel added include light and thin scrap, medium scrap steel, heavy scrap steel, baled scrap, briquettes, steel slag, dust balls, carbon scrap steel, alloy scrap steel, and pig iron blocks.

3. The control method based on a converter operation model under high scrap ratio conditions as described in claim 1, characterized in that, In step S2, the factors for calculating heat balance and material balance include molten iron conditions, feeding conditions, and oxygen supply conditions; molten iron conditions include molten iron composition and temperature; feeding conditions include scrap steel type and proportion, slag material weight and amount added; oxygen supply conditions include oxygen supply time, oxygen consumption, and exothermic oxidation reactions of various elements.

4. A control method based on a model of converter operation under high scrap ratio conditions as claimed in claim 1, characterized in that, In step S4, after the converter furnace cycle is completed, the model data information is fed back to the database for self-learning correction.

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