A smelting method for desulfurizing hot metal ladles

Abstract

The present invention relates to a smelting method for desulfurizing hot metal ladles, comprising the following steps: (1) adding LF ladle top slag to an empty hot metal ladle, selecting LF ladle top slag with a CaO content ≥ 40%, and determining the addition amount according to the CaO content in the LF ladle top slag; (2) moving the hot metal ladle with the added LF ladle top slag to the hot metal receiving position to receive hot metal, requiring the hot metal temperature ≥ 1380 °C and the S content in the hot metal ≥ 0.040% before receiving hot metal; (3) turning on oxygen for bottom blowing gas in the hot metal ladle before receiving hot metal, with a bottom blowing oxygen flow rate of 600 - 900 NL / min, and ensuring that the hot metal ladle is bottom blown with oxygen throughout the hot metal receiving process; (4) receiving hot metal and completing stirring desulfurization during the hot metal receiving process, requiring the hot metal receiving time to be controlled within 4.5 min - 5.5 min; (5) after the hot metal receiving is completed, increasing the intensity of bottom stirring with oxygen, adjusting the bottom blowing stirring to 1200 - 1300 NL / min, and then continuously stirring for 2 - 3 min to end desulfurization, with a desulfurization rate of up to 35 - 45%; The present invention mainly recovers waste slag and completes hot metal desulfurization during the hot metal receiving process, effectively realizing the secondary utilization of resources and having good social and economic benefits.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking desulfurization, in particular to a smelting method for desulfurizing hot metal ladles. Background Art

[0002] Sulfur is generally a harmful element in steel. The desulfurization method mainly adopts hot metal pretreatment desulfurization. The hot metal pretreatment desulfurization generally adopts the mechanical stirring method and the injection method. Both desulfurization methods have strong desulfurization capabilities. Among them, the commonly used desulfurizer in the mechanical stirring method generally selects a CaO-based solid powder desulfurizer. After being added to the hot metal, it gradually melts with stirring and participates in the desulfurization reaction. The desulfurization cost is low and the desulfurization efficiency is relatively high.

[0003] For another main process equipment LF furnace in steelmaking, the top slag of the ladle is rich in CaO, and the CaO content is generally above 45%, and can even reach above 60%. The desulfurization ability of the top slag of the LF ladle furnace is extremely strong, and the top slag of the LF ladle is generally a CaO-Al2O3 slag system with a relatively low melting point, which is suitable for use at the hot metal temperature. However, in the actual production process, after the LF furnace finishes refining, the top slag of the ladle is generally poured into the slag pot as waste slag without being utilized. Summary of the Invention

[0004] The purpose of the present invention is to use the top slag of the LF ladle for hot metal pre-desulfurization, and provide a smelting method for desulfurizing hot metal ladles. By using the method of the present invention, a desulfurization rate of 35-45% can be achieved in the hot metal ladle.

[0005] A smelting method for desulfurizing hot metal ladles according to the present invention includes the following steps:

[0006] (1) Add the top slag of the LF ladle to an empty hot metal ladle. Select the top slag of the LF ladle with a CaO content ≥ 40%, and determine the addition amount according to the CaO content in the top slag of the LF ladle:

[0007] A. When 40% ≤ CaO ≤ 48% in the top slag of the LF ladle, the addition amount of the top slag of the ladle is 11-12 Kg / t of hot metal;

[0008] B. When 48% < CaO < 56% in the top slag of the LF ladle, the addition amount of the top slag of the ladle is 9-10 Kg / t of hot metal;

[0009] C. When CaO ≥ 56% in the top slag of the LF ladle, the addition amount of the top slag of the ladle is 7-8 Kg / t of hot metal;

[0010] (2) Move the hot metal ladle added with the top slag of the LF ladle to the hot metal receiving position to receive hot metal. It is required that the hot metal temperature ≥ 1380 °C and the S content in the hot metal ≥ 0.040% before receiving hot metal;

[0011] (3) Before pouring molten iron, turn on the oxygen for the bottom blowing gas of the hot metal ladle, with the bottom blowing oxygen flow rate of 600 - 900 NL / min, and ensure that the bottom blowing oxygen of the hot metal ladle is throughout the whole process during the pouring of molten iron;

[0012] (4) Pour molten iron and complete stirring desulfurization during the pouring process. To ensure sufficient stirring and desulfurization time and better complete the slag washing desulfurization task, the pouring time is required to be controlled within 4.5 min - 5.5 min;

[0013] (5) After the pouring of molten iron is completed, increase the intensity of bottom stirring with oxygen, adjust the bottom blowing stirring to 1200 - 1300 NL / min, and continue stirring for 2 - 3 min to end desulfurization, and the desulfurization rate can reach 35 - 45%.

[0014] The top slag of the LF ladle is added to the hot metal ladle in a liquid state.

[0015] The process principle of the present invention is as follows: The hot metal is desulfurized by using the top slag of the LF ladle. The top slag of the LF ladle is in a liquid state, and directly adding it for use can omit the melting time. It is selected to directly add the top slag of the LF ladle into an empty hot metal ladle, then pour molten iron into the hot metal ladle with the top slag of the LF ladle added, control the pouring time of molten iron, use the stirring during the pouring process to complete slag washing, and blow O2 from the bottom of the hot metal ladle. Blowing O2 from the bottom can, on the one hand, improve the stirring ability, and on the other hand, use the bottom blowing of O2 to promote the regeneration of CaO in the slag and further complete desulfurization. The specific principle analysis is as follows:

[0016] The desulfurization reaction equation of the present invention is as follows:

[0017] (CaO) + [S] → (CaS) + 1 / 2O2 (1)

[0018] As the desulfurization reaction proceeds, the content of CaO in the slag is gradually consumed, the content of CaO gradually decreases, while the content of CaS in the slag gradually increases as the desulfurization reaction proceeds. To ensure the continuous progress of the reaction and improve the utilization rate of the CaO desulfurizer, since reaction formula (1) is a reversible reaction, by continuously injecting O2, O2 reacts with CaS in the slag, and CaO and SO2 can be reproduced. The regeneration process of CaO can promote the continuous progress of the desulfurization reaction

[0019] (CaS) + 3 / 2{O2}→ (CaO) + {SO2} (2)

[0020] Therefore, by using the method of the present invention, desulfurization smelting can be easily achieved in the hot metal ladle, and the desulfurization rate is as high as 35 - 45%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1)The present invention mainly uses recycled waste residue to desulfurize hot metal during the hot metal charging process, effectively realizing the secondary utilization of resources and having good social and economic benefits.

[0023] (2)The desulfurization efficiency of the present invention is relatively high. The hot metal desulfurization task is advanced or partially advanced to the hot metal charging process, effectively reducing the desulfurization pressure on KR and saving desulfurization costs.

[0024] (3)The process flow of the present invention is simple and clear, highly operable, and easy to control. Specific Embodiments

[0025] In order to better explain the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with specific embodiments. The following embodiments are merely exemplary descriptions of the technical solution of the present invention and do not limit the present invention in any form. Any changes or equivalent substitutions that do not deviate from the concept of the present invention are included within the protection scope of the present invention.

[0026] Example 1

[0027] Hot metal ladle number 1, sulfur content in hot metal before charging: w(S)%: 0.042%.

[0028] A smelting method for desulfurizing hot metal in this embodiment includes the following steps:

[0029] (1)Add LF ladle top slag to the empty hot metal ladle 1. Detect that the CaO content in the LF ladle top slag is 45%, and add 11.5 Kg / t of hot metal of LF ladle top slag to the empty hot metal ladle 1;

[0030] (2)Move the hot metal ladle with LF steel plate top slag added to the hot metal charging position to receive hot metal. The temperature of the hot metal before charging is 1380 °C, and the S content of the hot metal is 0.042%;

[0031] (3)Before charging, turn on oxygen for the bottom blowing gas of the hot metal ladle, and the bottom blowing oxygen flow rate is 600 NL / min. The hot metal ladle is bottom blown with oxygen throughout the hot metal charging process;

[0032] (4)Charge hot metal and complete stirring desulfurization during the hot metal charging process. To ensure sufficient stirring and desulfurization time and better complete the slag washing desulfurization task, the actual hot metal charging time is 4.5 min;

[0033] (5)After the hot metal charging is completed, increase the bottom stirring intensity, adjust the bottom blowing stirring to 1200 NL / min, and continue stirring for 2 min to end desulfurization.

[0034] After the hot metal charging is completed, take a sample for detection, w(S)%: 0.0273%, and the desulfurization efficiency during the hot metal charging process is 35%.

[0035] Example 2

[0036] Hot metal ladle No. 2, sulfur content of hot metal before charging: w(S)%: 0.050%.

[0037] A smelting method for desulfurizing hot metal in a hot metal ladle in this embodiment includes the following steps:

[0038] (1) Add LF ladle top slag to the empty hot metal ladle 2. Detect that the CaO content in the LF ladle top slag is 52%. Add 9.5 Kg / t of hot metal of LF ladle top slag to the empty hot metal ladle 2;

[0039] (2) Move the hot metal ladle with LF ladle top slag added to the charging position to receive hot metal. The temperature of the hot metal before charging is 1390 °C, and the S content of the hot metal is 0.050%;

[0040] (3) Before charging, turn on oxygen for bottom blowing gas in the hot metal ladle. The bottom blowing oxygen flow rate is 700 NL / min, and the hot metal ladle is bottom blown with oxygen throughout the charging process;

[0041] (4) Charge the hot metal and complete stirring desulfurization during the charging process. To ensure sufficient stirring and desulfurization time and better complete the slag washing desulfurization task, the actual charging time is 5 min;

[0042] (5) After the charging is completed, increase the intensity of bottom stirring with oxygen. Adjust the bottom blowing stirring to 1250 NL / min and continue stirring for 2.5 min to end desulfurization.

[0043] After the charging is completed, take a sample for detection. w(S)%: 0.030%, and the desulfurization efficiency during the charging process is 40%.

[0044] Example 3:

[0045] Hot metal ladle No. 3, sulfur content of hot metal before charging: w(S)%: 0.056%.

[0046] A smelting method for desulfurizing hot metal in a hot metal ladle in this embodiment includes the following steps:

[0047] (1) Add LF ladle top slag to the empty hot metal ladle 3. Detect that the CaO content in the LF ladle top slag is 58%. Add 7.5 Kg / t of hot metal of LF ladle top slag to the empty hot metal ladle 3;

[0048] (2) Move the hot metal ladle with top slag added to the charging position to receive hot metal. The temperature of the hot metal before charging is 1400 °C, and the S content of the hot metal is 0.056%;

[0049] (3) Before charging, turn on oxygen for bottom blowing gas in the hot metal ladle. The bottom blowing oxygen flow rate is 900 NL / min, and the hot metal ladle is bottom blown with oxygen throughout the charging process;

[0050] (4) Charge the hot metal and complete stirring desulfurization during the charging process. To ensure sufficient stirring and desulfurization time and better complete the slag washing desulfurization task, the actual charging time is 5.5 min;

[0051] After the hot metal charging is completed, increase the intensity of bottom oxygen stirring, adjust the bottom blowing stirring to 1300 NL / min, and continue stirring for another 3 min to end the desulfurization.

[0052] Take a sample after the hot metal charging is completed. w(S)%: 0.0308%. The desulfurization efficiency during the hot metal charging process is 45%.

[0053] Compare the hot metal desulfurization and smelting method of the present invention with the conventional hot metal charging mode of the hot metal ladle. The results are shown in Table 1 below.

[0054] Table 1 Comparison list of the hot metal charging and smelting method of the embodiment of the present invention and the conventional hot metal charging mode of the hot metal ladle

[0055]

[0056] As can be seen from Table 1 above, by using the hot metal desulfurization and smelting method of the present invention, the desulfurization rate of the hot metal ladle can reach 35 - 45%, while in the conventional hot metal charging mode of the hot metal ladle, the desulfurization is generally not carried out during the hot metal charging process, and the desulfurization efficiency during the hot metal charging process is 0.

Claims

1. A smelting method for desulfurizing hot metal ladles, characterized in that It includes the following steps: Add LF ladle top slag into an empty hot metal ladle. Select LF ladle top slag with CaO content ≥ 40%, and determine the addition amount according to the CaO content in the LF ladle top slag: When 40% ≤ CaO ≤ 48% in the LF ladle top slag, the addition amount of ladle top slag is 11 - 12 Kg / t hot metal; When 48% < CaO < 56% in the LF ladle top slag, the addition amount of ladle top slag is 9 - 10 Kg / t hot metal; When CaO ≥ 56% in the LF ladle top slag, the addition amount of ladle top slag is 7 - 8 Kg / t hot metal; (2) Move the hot metal ladle with LF ladle top slag added to the hot metal receiving position for receiving hot metal. It is required that the hot metal temperature ≥ 1380 °C and the S content in the hot metal ≥ 0.040% before hot metal receiving; (3) Open oxygen for bottom blowing gas at the bottom of the hot metal ladle before hot metal receiving. The bottom blowing oxygen flow rate is 600 - 900 NL / min, and ensure that the hot metal ladle is bottom blown with oxygen throughout the hot metal receiving process; (4) Receive hot metal and complete stirring desulfurization during the hot metal receiving process. To ensure sufficient stirring and desulfurization time and better complete the slag washing desulfurization task, it is required that the hot metal receiving time is controlled within 4.5 min - 5.5 min; (5) After the hot metal receiving ends, increase the intensity of bottom blowing oxygen stirring. Adjust the bottom blowing stirring to 1200 - 1300 NL / min and continue stirring for 2 - 3 min to end desulfurization. The desulfurization rate can reach 35 - 45%.

2. The smelting method for desulfurizing hot metal ladles according to claim 1, characterized in that: The LF ladle top slag is added to the hot metal ladle in a liquid state.

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