Method for controlling oxygen supply flow in stages during converter blowing

Abstract

The invention discloses a method for controlling oxygen supply flow in stages during converter blowing, which relates to the technical field of metallurgy and comprises the following steps: calculating the total amount of converter smelting oxygen blowing based on the total loading amount of converter molten iron and scrap steel and molten iron component information; converter smelting is conducted, and the oxygen supply flow and the blowing lance position are adjusted according to the carbon monoxide concentration rising speed; and finishing smelting when the carbon monoxide concentration is reduced to a threshold value. According to the CO concentration change trend, the original constant-pressure lance changing operation is optimized into variable-pressure lance changing operation according to different carbon content reaction stages, so that the problem of smoke overflow caused by the fact that smoke cannot be sucked away by dust due to the fact that carbon-oxygen reaction is too violent is solved, explosive splashing in the peak period of the carbon-oxygen reaction is relieved, and the service life of the carbon-oxygen reaction is prolonged. And meanwhile, the process requirements of converter slagging, dephosphorization and decarbonization are met, and the production requirements of converter smelting can be met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, in particular to a method for controlling oxygen flow in stages in converter blowing. BACKGROUND

[0002] A converter operation is a steelmaking process in which molten iron, scrap, and the like, which constitute main raw materials, are supplied with oxygen to perform oxidation refining (blowing), thereby obtaining molten steel. In the converter operation, in order to control the temperature and component concentration of molten steel at the end of blowing (stoppage) to target values, a blowing control is performed which is a combination of static control and dynamic control. In the static control, a mathematical model based on heat balance and material balance is used to determine the oxygen supply amount and the input amount of a cooling material or a temperature-raising material required to control the temperature and component concentration of molten steel to target values before the start of blowing. On the other hand, in the dynamic control, the temperature and component concentration of molten metal are measured during blowing using a sublance, and the oxygen supply amount and the input amount of a cooling material or a temperature-raising material determined in the static control are corrected according to a mathematical model based on heat balance and material balance and a reaction model. Then, in the dynamic control, the oxygen supply amount and the input amount of a cooling material or a temperature-raising material until the stoppage are finally determined and controlled.

[0003] At present, the oxygen flow in the converter blowing process is generally controlled according to production experience, which leads to difficult control of the converter blowing and easy occurrence of converter dry return and spattering. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for controlling oxygen flow in stages in converter blowing.

[0005] In order to solve the above technical problems, the technical scheme of the present application is as follows: A method for controlling oxygen flow in stages in converter blowing, comprising: calculating the total oxygen blowing amount for converter smelting based on the total amount of molten iron and scrap charged into the converter and the component information of the molten iron; smelting in the converter and adjusting the oxygen flow and the blowing lance position according to the carbon monoxide concentration rise rate; ending the smelting when the carbon monoxide concentration decreases to a threshold value.

[0006] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing, wherein: the calculation of the total oxygen blowing amount for converter smelting based on the total amount of molten iron and scrap charged into the converter and the component information of the molten iron comprises: the total oxygen blowing amount for converter smelting is the total amount of molten iron and scrap charged into the converter multiplied by 42 Nm 3 / ton.

[0007] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing according to the present application, wherein: the adjusting of oxygen flow by carbon monoxide concentration comprises: controlling the oxygen flow in the initial stage of smelting to be 28000Nm 3 / h; adjusting the oxygen flow to be 26000Nm 3 / h~27000Nm 3 / h when the carbon monoxide concentration reaches 35%; adjusting the oxygen flow to be 27000Nm 3 / h~28000Nm 3 / h when the carbon monoxide concentration changes from the rising stage to the falling stage, and adjusting the oxygen flow to be 26000Nm 3 / h~27000Nm 3 / h when the carbon monoxide concentration changes from the falling stage to the rising stage; controlling the oxygen flow in the final stage of blowing to be 28000Nm 3 / h.

[0008] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing according to the present application, wherein: the adjusting of blowing lance position by carbon monoxide concentration rising speed comprises: controlling the blowing lance position in the initial stage of blowing to be 1300mm; adjusting the blowing lance position to be 1350~1400mm when the carbon monoxide concentration reaches 35%; adjusting the blowing lance position to be 1300mm when the carbon monoxide concentration changes from the rising stage to the falling stage, and adjusting the blowing lance position to be 1300~1500mm when the carbon monoxide concentration changes from the falling stage to the rising stage; controlling the blowing lance position in the final stage of blowing to be 1200mm.

[0009] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing according to the present application, wherein: after the converter smelting and the adjusting of oxygen flow and blowing lance position by carbon monoxide concentration rising speed, further comprising: adding auxiliary materials for converter smelting when the carbon monoxide concentration changes from the rising stage to the falling stage.

[0010] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing according to the present application, wherein: the auxiliary materials for converter smelting are slag materials.

[0011] As a preferred scheme of the method for controlling oxygen flow in stages in converter blowing according to the present application, wherein: the ending of smelting when the carbon monoxide concentration decreases to a threshold value comprises: ending the smelting when the carbon monoxide concentration decreases to 15%.

[0012] The beneficial effects of the present application are: The present application optimizes the original constant pressure variable lance operation to variable pressure variable lance operation according to the CO concentration change trend, which avoids the problem of smoke dust overflow caused by the fact that the carbon-oxygen reaction is too violent and the flue gas cannot be dedusted and sucked away, and relieves the explosive spatter during the carbon-oxygen reaction peak period, while ensuring to meet the process requirements of converter slagging, dephosphorization and decarburization, and can meet the production needs of converter smelting. DETAILED DESCRIPTION

[0013] In order to make the content of the present application more easily and clearly understood, the present application will be further described in detail according to the specific embodiments.

[0014] Example 1: The present embodiment provides a method for controlling oxygen flow in stages during converter blowing, which specifically comprises the following steps: Step S1: The composition of the molten iron in the converter is carbon 4.74%, silicon 0.38%, phosphorus 0.124%, and the weight is 103 tons, the weight of scrap steel is 24.5 tons, and the calculated oxygen blowing amount is 5355 Nm 3 .

[0015] Step S2: The converter starts to smelt by igniting the lance, and the lance flow is adjusted by observing the CO concentration change trend. The overall lance trend is low→high→low→high→low mode, see Table 1. According to the CO concentration change adjustment, gradually press the lance to 1200mm for decarburization.

[0016] Table 1

[0017] Step S3: While adjusting the oxygen lance position, the oxygen flow is adjusted according to the CO concentration curve slope. According to the CO concentration curve slope, the carbon-oxygen reaction rate is judged, and the basic oxygen flow is reduced from 28000Nm 3 / h to 25000-26000Nm3 / h, and then the oxygen flow is increased after the carbon-oxygen reaction peak period, which avoids the problem of explosive spatter caused by too violent carbon-oxygen reaction. See Table 2 for specific converter oxygen flow.

[0018] Table 2

[0019] Step S4: When the blowing is finished and the CO drops to 15%, the lance is lifted to end the smelting, and the actual oxygen supply amount is 5456 Nm 3 . The terminal measurement temperature is 1658℃, the carbon is 0.0835%, and the phosphorus is 0.0248%, which meets the process decarburization and dephosphorization requirements, and there is no spatter and smoke dust overflow phenomenon.

[0020] Embodiment 2: The embodiment provides a method for controlling oxygen flow in stages in converter blowing, and the method specifically comprises the following steps: Step S1: The converter is charged with molten iron with a carbon content of 4.57%, a silicon content of 0.41%, a phosphorus content of 0.134%, a weight of 103 tons, scrap steel with a weight of 25.53 tons, and a calculated oxygen blowing amount of 5784 Nm 3 .

[0021] Step S2: The converter starts to smelt by igniting the lower lance, and the lance flow is adjusted by observing the CO concentration curve. The overall lance trend is low->high->low->high->low mode, as shown in Table 3. According to the CO concentration curve adjustment, the lance is gradually pressed to 1200 mm for decarburization.

[0022] Table 3

[0023] Step S3: While adjusting the oxygen lance, the oxygen flow is adjusted according to the CO concentration curve slope. According to the CO concentration curve slope, the carbon-oxygen reaction rate is judged, and the basic oxygen flow is reduced from 28000 Nm 3 / h to 25000-26000 Nm 3 / h, and then the oxygen flow is increased after the carbon-oxygen reaction peak, so as to avoid the problem of explosive spatter caused by too intense carbon-oxygen reaction. The specific converter oxygen flow is shown in Table 4.

[0024] Table 4

[0025] Step S4: When the blowing is to 100% endpoint, the lance is lifted to end the smelting, and the actual oxygen supply amount is 5974 Nm 3 . The endpoint measurement temperature is 1648℃, the carbon content is 0.1328%, and the phosphorus content is 0.0216%, which meets the process decarburization and dephosphorization requirements, and there is no spatter and smoke overflow phenomenon.

[0026] Therefore, the technical scheme of the present application optimizes the original constant pressure variable lance operation into a variable pressure variable lance operation according to different carbon content reaction stages according to the CO concentration change trend, which not only avoids the problem of smoke overflow caused by the fact that the flue gas cannot be dusted and sucked away due to too intense carbon-oxygen reaction, but also relieves the explosive spatter at the carbon-oxygen reaction peak, while ensuring that the process requirements of converter slagging and dephosphorization and decarburization are met, and the production needs of converter smelting can be met.

[0027] In addition to the above embodiments, the present application can also have other implementation manners; any technical scheme formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A method for controlling oxygen supply flow in stages during converter blowing, characterized in that: include: Calculate the total oxygen blowing amount for converter smelting based on the total charge of converter molten iron and scrap steel and the molten iron composition information; Carry out converter smelting and adjust the oxygen flow rate and blowing gun position according to the rising rate of carbon monoxide concentration; The smelting is terminated when the carbon monoxide concentration drops to a threshold value.

2. The method for controlling oxygen flow rate in stages during converter blowing according to claim 1, characterized in that: The calculation of the total amount of oxygen blown for converter smelting based on the total charge amount of converter molten iron and scrap steel and the molten iron composition information includes: The total amount of oxygen blown in converter smelting is the total amount of molten iron and scrap charged into the converter multiplied by 42 Nm 3 / ton.

3. The method for controlling oxygen supply flow in stages during converter blowing according to claim 1, characterized in that: The adjusting of the oxygen supply flow rate according to the carbon monoxide concentration comprises: Control the oxygen flow rate at the initial stage of smelting to 28000Nm 3 / h; When the carbon monoxide concentration reaches 35%, adjust the oxygen flow rate to 26000Nm 3 / h~27000Nm 3 / h; When the carbon monoxide concentration changes from an increasing stage to a decreasing stage, adjust the oxygen flow rate to 27000Nm 3 / h~28000Nm 3 / h, when the carbon monoxide concentration changes from a decreasing stage to an increasing stage, the oxygen supply flow rate is adjusted to 26000Nm 3 / h~27000Nm 3 / h; Control the oxygen flow rate at the end of blowing to 28000Nm 3 / h.

4. The method for controlling oxygen flow rate in stages during converter blowing according to claim 1, wherein: The adjusting of the blowing gun position by the rising speed of carbon monoxide concentration includes: The blowing gun position at the initial stage of blowing is controlled to be 1300mm; When the carbon monoxide concentration reaches 35%, adjust the blowing gun position to 1350~1400mm; When the carbon monoxide concentration changes from an increasing stage to a decreasing stage, adjust the blowing gun position to 1300mm; when the carbon monoxide concentration changes from a decreasing stage to an increasing stage, adjust the blowing gun position to 1300~1500mm; The blowing gun position at the end of blowing is controlled to be 1200mm.

5. The method for controlling oxygen flow rate in stages during converter blowing according to claim 1, characterized in that: After performing converter smelting and adjusting the oxygen flow rate and blowing lance position according to the increasing rate of carbon monoxide concentration, the method further includes: The converter smelting auxiliary materials are added when the carbon monoxide concentration changes from an increasing stage to a decreasing stage.

6. The method for controlling oxygen flow rate in stages during converter blowing according to claim 5, characterized in that: The converter smelting auxiliary material is slag.

7. The method for controlling oxygen flow rate in stages during converter blowing according to claim 1, characterized in that: The smelting is terminated when the carbon monoxide concentration drops to a threshold value, comprising: The smelting is terminated when the carbon monoxide concentration drops to 15%.

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