A method for smelting and desulfurizing super-high sulfur molten iron

Abstract

The present application relates to the technical field of steel smelting, in particular, especially relates to a kind of smelting desulphurization method of super-high sulfur molten iron.The present application comprises the following steps: (1) molten iron is mixed into converter after being raked slag and smelted, and additional active lime is added;(2) alloying process is carried out, aluminum powder is added, additional aluminum wire section is added, active lime is added during converter tapping process, and ladle argon blowing is carried out;(3) ladle is moved to argon station, and desulphurization is carried out by adding active lime and aluminum powder;(4) molten iron is introduced into LF furnace refining, and desulphurization is carried out by adding fluorite and desulphurization white lime.The present application reduces the proportion of super-high sulfur molten iron pretreatment, reduces molten iron loss, reduces super-high sulfur molten iron pretreatment desulphurization powder consumption and energy consumption, reduces the cost of molten iron pretreatment process, reduces the process time of super-high sulfur molten iron production organization, and improves production efficiency.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and more particularly to a desulfurization method for smelting ultra-high sulfur molten iron. Background Technology

[0002] During the steelmaking process, the sulfur content of molten iron is generally controlled within the range of 0.020%-0.060%. When the sulfur content of molten iron exceeds 0.080%, the molten iron must undergo pretreatment to remove sulfur before being added to the converter for smelting.

[0003] Due to abnormal raw materials or malfunctions in blast furnace operation, high-sulfur or ultra-high-sulfur molten iron may be produced. When the sulfur content of molten iron exceeds 0.100%, it is considered ultra-high-sulfur molten iron. Such molten iron is generally directly used for casting iron, which restricts the production capacity of steelmaking lines. When using ultra-high-sulfur molten iron, a pretreatment process should be performed. However, the pretreatment process for ultra-high-sulfur molten iron is very time-consuming and consumes a large amount of powder. Furthermore, significant molten iron loss occurs during the slag removal process after desulfurization.

[0004] To reduce process costs and energy consumption, existing technologies have explored the direct addition of ultra-high sulfur molten iron to the converter without pretreatment. Currently, publicly available domestic materials describe several converter desulfurization methods. For example, patent CN201710068962.4 discloses a method for desulfurizing ultra-low temperature, ultra-high sulfur molten iron in a converter, achieving a desulfurization rate of over 70% by adjusting and controlling the converter charging system and the converter smelting process; patent CN202310526898.5 discloses a rapid desulfurization method for converter smelting, adding a desulfurizing agent to the ladle and injecting inert gas during the steel tapping process, followed by removing the desulfurization slag after tapping; and patent CN202210330382.9 discloses... A smelting method for efficient desulfurization at the converter endpoint includes the following steps: (1) dual-slag smelting, with 20%-35% of the slag being poured out during blowing for 240-270s; (2) 50%-60% of the slag being poured out at the converter endpoint; (3) controlling the converter endpoint temperature to be >1650℃ and the temperature after slag pouring to be >1640℃; (4) controlling the oxygen content of the molten steel after slag pouring to be <500ppm; (5) adding desulfurizing agent and deoxidizing agent to the converter for rapid deoxidation; (6) starting the converter for compound stirring desulfurization; (7) compound stirring for 4-7 minutes, with the desulfurization rate reaching 45%-80%, completing the desulfurization and normal steel tapping.

[0005] The aforementioned existing technologies only address the desulfurization process in converter smelting; no reports have been found on the method of desulfurization using a converter + LF furnace. Summary of the Invention

[0006] The purpose of this invention is to provide a desulfurization method for smelting ultra-high sulfur molten iron. Targeting steel grades produced using the "converter-LF-casting machine process," this method achieves production using ultra-high sulfur molten iron through converter desulfurization, desulfurization during tapping, argon station desulfurization, and LF furnace desulfurization. This method not only reduces the pressure of the desulfurization process, lowers the consumption of desulfurization powder, energy consumption, and molten iron loss, thus reducing smelting costs, but also allows for the operation of steelmaking lines under ultra-high sulfur molten iron conditions without the need for casting iron, ensuring stable production.

[0007] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0008] This invention provides a method for desulfurizing ultra-high sulfur molten iron, comprising the following steps:

[0009] (1) After removing the slag, the molten iron is added to the converter for smelting, and active lime is added.

[0010] (2) During the steelmaking alloying process, aluminum powder is added and aluminum wire segments are added. During the converter steelmaking process, active lime is added and argon is blown into the ladle.

[0011] (3) The steel ladle was moved to the argon station and desulfurized by adding quicklime and aluminum powder;

[0012] (4) The molten steel is fed into the LF furnace for refining, and desulfurization is carried out by adding fluorite and desulfurization lime.

[0013] In the above technical solution, further, in step (1), the relationship between the sulfur content of molten iron and the amount of slag removed is as follows:

[0014] For molten iron with a content of 0.100% ≤ S < 0.150%, remove 1 / 3 of the molten iron slag.

[0015] For molten iron with a content of 0.150% ≤ S < 0.200%, remove half of the molten iron slag.

[0016] For molten iron with a slag content of 0.200% ≤ S < 0.250%, remove 3 / 4 of the molten iron slag.

[0017] The molten iron has a sulfur content of ≥0.250%, and all molten iron slag is removed.

[0018] In the above technical solution, further, in step (1), the relationship between the amount of active lime added during the converter smelting process and the sulfur content of the molten iron is as follows:

[0019] The amount of active lime added = (sulfur content of molten iron - 0.100%) × 10000, unit: kg / t steel.

[0020] In the above technical solution, further, in step (2), the amount of active lime added during the converter tapping process is:

[0021] When the final sulfur content at the converter is ≥0.050%, the amount of active lime added is 2.5 + 2 × (final sulfur content at the converter - 0.050%) × 2000, kg / t steel; when the final sulfur content at the converter is <0.050%, the amount of active lime added is 2.5 kg / t steel.

[0022] The amount of aluminum powder added during the converter alloying process is:

[0023] When the sulfur content at the converter endpoint is ≥0.050%, the amount of aluminum powder added is = (sulfur content at the converter endpoint - 0.050%) × 500 kg / t steel; when the sulfur content at the converter endpoint is <0.050%, no aluminum powder is added after tapping the steel from the converter.

[0024] The amount of aluminum segment added during the converter alloying process is:

[0025] When the sulfur content at the converter endpoint is ≥0.050%, the amount of aluminum wire segment to be added is (sulfur content at the converter endpoint - 0.050%) × 500, kg / t steel; when the sulfur content at the converter endpoint is <0.050%, no additional aluminum wire segment is required when tapping steel from the converter.

[0026] In the above technical solution, further, in step (2), the ladle argon blowing method is as follows:

[0027] The argon blowing time during the tapping process is:

[0028] When the final sulfur content of the converter is ≥0.050%, the argon blowing time during the tapping process is 120 + (final sulfur content - 0.050%) * 100000, unit: s; when the final sulfur content of the converter is <0.050%, the argon blowing time during the tapping process is 120 s.

[0029] The argon blowing flow rate during the steel tapping process is 80 ± 0.5 m³ / s. 3 / min;

[0030] The argon blowing time after tapping is:

[0031] When the final sulfur content of the converter is ≥0.050%, the argon blowing time after tapping is 0.8 * (final sulfur content - 0.050%) * 200000, unit: s; when the final sulfur content of the converter is <0.0500%, the argon blowing time after tapping is 0 s.

[0032] The argon blowing flow rate after tapping is 80±0.5m³. 3 / min;

[0033] The argon blowing time at the argon station is:

[0034] When the final sulfur content of the converter is ≥0.050%, the argon blowing time at the argon station is 150 + (final sulfur content - 0.050%) * 100000, in seconds; when the final sulfur content of the converter is <0.050%, the argon blowing time after tapping is 150 seconds.

[0035] The argon blowing flow rate at the argon station is 100 ± 0.5 m³ / s. 3 / min.

[0036] In the above technical solution, further, in step (3), the amount of active lime added is:

[0037] When the sulfur content in the argon station is ≥0.050%, the amount of quicklime to be added is calculated as (sulfur content in the argon station - 0.050%) × 10000, with the unit being kg / t steel. When the sulfur content in the argon station is <0.050%, no quicklime needs to be added.

[0038] The amount of aluminum powder added is:

[0039] When the sulfur content in the argon station is ≥0.050%, the amount of aluminum powder added = (sulfur content in the argon station - 0.050%) × 500, unit: kg / t steel; when the sulfur content in the argon station is <0.050%, no aluminum powder is added.

[0040] In the above technical solution, further, in step (3), when the sulfur content of the argon station is ≥0.050%, a second argon blowing is performed. The second argon blowing time is calculated as (argon station sulfur content - 0.050%) * 500,000, where the second argon blowing flow rate is 100 ± 0.5 m³ / s. 3 / min.

[0041] In the above technical solution, further, in step (4), the amount of fluorite added is:

[0042] When the sulfur content at the LF furnace inlet is ≥0.050%, the amount of fluorite to be added is = (sulfur content at the LF furnace inlet - 0.050%) × 1000, unit: kg / t steel; when the sulfur content at the LF furnace inlet is <0.050%, no additional fluorite is required.

[0043] The amount of quicklime to be added is:

[0044] When the sulfur content at the LF furnace inlet is ≥0.050%, the amount of quicklime to be added is = (sulfur content at the LF furnace inlet - 0.050%) × 5000, unit: kg / t steel. When the sulfur content at the LF furnace inlet is <0.050%, no quicklime needs to be added.

[0045] The beneficial effects of this invention are as follows:

[0046] 1. Reduce the proportion of pretreatment of ultra-high sulfur molten iron to reduce molten iron loss;

[0047] 2. It fills the gap in the LF furnace steel grades for smelting ultra-high sulfur molten iron;

[0048] 3. Reduce the consumption of desulfurization powder and energy in the pretreatment of ultra-high sulfur molten iron, thereby reducing the cost of the molten iron pretreatment process;

[0049] 4. Reduce the time required for organizing the production of ultra-high sulfur molten iron and improve production efficiency. Detailed Implementation

[0050] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0051] Example 1

[0052] The steel grade to be smelted is AH32, the ladle is grade D, the turnaround time is 100 min, the steel output is 270.5 t, the finished product requirements are S≤0.020%, the molten iron temperature is 1386℃, the molten iron S content is 0.128%, and the scrap steel is 43.2 t.

[0053] Includes the following steps:

[0054] 1) Remove 1 / 3 of the molten iron slag, amounting to 0.5t, and then add it to the converter;

[0055] 2) 757 kg of quicklime was added during the converter smelting process, bringing the total addition to 8757 kg. The oxygen accumulation reached 11106 Nm³. 3 At that time, TSC test was carried out through the secondary gun. According to the TSC measurement data, the gun was lifted when the end point was reached. The end point temperature was 1648℃ and the oxygen value was 436ppm. The results of rapid analyzer detection were C=0.056%, P=0.0163%, and S=0.088%.

[0056] 3) During the steelmaking alloying process, the amount of aluminum wire added was 41 kg, with a total addition of 476 kg. Aluminum powder was added at 51 kg, and the total amount of quicklime added was 1087 kg, of which 412 kg was added as supplementary quicklime. The argon blowing time during the steelmaking process was 158 seconds, and the argon flow rate was 80 m³ / s. 3 / min, argon blowing time after tapping is 76s, argon flow rate is 80m³ / min. 3 / min, driven to the argon station, argon purge time at the argon station 188s, argon flow rate 100m³ / min. 3 / min;

[0057] 4) The argon station sample concentration (S) was 0.065%, which did not meet the requirements for entering the LF furnace (S < 0.050%). Secondary treatment was performed at the argon station, adding 405 kg of quicklime and 20 kg of aluminum powder. The secondary argon blowing time was 75 seconds, and the argon flow rate was 100 m³ / s. 3 / min, proceed to the next process;

[0058] 5) The sample taken from the LF furnace has an S=0.048% content. After conventional process treatment, the S=0.011% content after LF treatment, which is qualified. The sample is then cast on the casting machine, and the S=0.011% content meets the requirements of the steel grade.

[0059] Example 2

[0060] The steel grade to be smelted is AGMJ45, ladle grade D, turnaround time is 105 min, steel output is 271.8 t, finished product requirements are S≤0.015%, molten iron temperature is 1372℃, molten iron S content is 0.155%, and scrap steel is 45.2 t.

[0061] Includes the following steps:

[0062] 1) Remove half of the molten iron slag, amounting to 0.9t, and then add it to the converter;

[0063] 2) During the converter smelting process, 1495 kg of quicklime was added, bringing the total addition to 9495 kg. The oxygen accumulation reached 10906 Nm³. 3 At that time, TSC test was carried out through the secondary gun. According to the TSC measurement data, the gun was lifted when the end point was reached. The end point temperature was 1652℃ and the oxygen value was 462ppm. The results of rapid analyzer detection were C=0.051%, P=0.0153%, and S=0.108%.

[0064] 3) During the steelmaking alloying process, 63 kg of aluminum wire segments were added, bringing the total to 512 kg. 78 kg of aluminum powder and 1310 kg of quicklime were added, of which 635 kg were added as supplementary material. The argon blowing time during the steelmaking process was 178 seconds, with an argon flow rate of 80 m³ / h. 3 / min, argon blowing time after tapping is 116s, argon flow rate is 80m³ / min. 3 / min, driven to the argon station, argon purge time at the argon station 208s, argon flow rate 100m³ / min. 3 / min;

[0065] 4) The argon station sample concentration (S) was 0.085%, which did not meet the requirements for entering the LF furnace (S < 0.050%). Secondary treatment was performed at the argon station, adding 951 kg of quicklime and 47 kg of aluminum powder. The secondary argon blowing time was 175 s, and the argon flow rate was 100 m³ / s. 3 / min, proceed to the next process;

[0066] 5) The sample taken from the LF furnace is S=0.068%. 48kg of fluorite was added to the LF furnace, bringing the total added fluorite to 248kg. 244kg of quicklime was added, bringing the total added amount to 2244kg. After LF treatment, S=0.009%, which is qualified. The sample was then cast on the casting machine. The casting machine S=0.010%, which meets the requirements of the steel grade.

[0067] Example 3

[0068] The steel grade is QB, the ladle is grade D, the turnaround time is 110 min, the steel output is 271.5 t, the finished product requirements are S≤0.020%, the molten iron temperature is 1392℃, the molten iron S content is 0.195%, and the scrap steel is 41.2 t.

[0069] Includes the following steps:

[0070] 1) Remove 3 / 4 of the molten iron slag, amounting to 1.2t, and then add it to the converter;

[0071] 2) During the converter smelting process, 2579 kg of quicklime was added, bringing the total amount of quicklime added to 10579 kg. The oxygen accumulation reached 11311 Nm³. 3 At that time, TSC test was carried out through the secondary gun. According to the TSC measurement data, the gun was lifted when the end point was reached. The end point temperature was 1642℃ and the oxygen value was 452ppm. The results of rapid analyzer detection were C=0.049%, P=0.0203%, and S=0.148%.

[0072] 3) During the steelmaking alloying process, 106 kg of aluminum wire segments were added, bringing the total to 545 kg. 133 kg of aluminum powder and 1743 kg of quicklime were added, of which 1068 kg were added as supplementary material. The argon blowing time during the steelmaking process was 218 seconds, with an argon flow rate of 80 m³ / h. 3 / min, argon blowing time after tapping is 196s, argon flow rate is 80m³ / min. 3 / min, driven to the argon station, argon purge time at the argon station 248s, argon flow rate 100m³ / min. 3 / min;

[0073] 4) The argon station sample concentration (S) was 0.0115%, which did not meet the requirements for entering the LF furnace (S < 0.050%). The argon station underwent secondary treatment, adding 1764 kg of quicklime and 88 kg of aluminum powder. The secondary argon blowing time was 325 s, and the argon flow rate was 100 m³ / s. 3 / min, proceed to the next process;

[0074] 5) The sample taken from the LF furnace is S=0.082%. 86kg of fluorite was added to the LF furnace, bringing the total added fluorite to 286kg. 434kg of quicklime was added, bringing the total added amount to 2434kg. After LF treatment, S=0.015%, which is qualified. The sample was then cast on the casting machine. The casting machine S=0.015%, which meets the requirements of the steel grade.

[0075] Example 4

[0076] Smelting steel grade A, ladle grade D, turnaround time 101 min, steel output 271.1 t, finished product requirements S≤0.020%, molten iron temperature 1377℃, molten iron S content 0.252%, scrap steel 42.2 t;

[0077] Includes the following steps:

[0078] 1) Remove all the slag from the molten iron, the amount of slag removed is 1.5t, and then add it to the converter;

[0079] 2) During the converter smelting process, 4120 kg of quicklime was added, bringing the total amount of quicklime added to 12120 kg. The oxygen accumulation reached 11016 Nm³. 3At that time, TSC test was carried out through the secondary gun. According to the TSC measurement data, the gun was lifted when the end point was reached. The end point temperature was 1662℃ and the oxygen value was 502ppm. The results of rapid analyzer detection were C=0.041%, P=0.0183%, and S=0.188%.

[0080] 3) During the steelmaking alloying process, 149 kg of aluminum wire segments were added, bringing the total to 618 kg. 187 kg of aluminum powder and 2174 kg of quicklime were added, of which 1499 kg were added as supplementary material. The argon blowing time during the steelmaking process was 258 seconds, with an argon flow rate of 80 m³ / h. 3 / min, argon blowing time after steel tapping is 276s, argon flow rate is 80m³ / min. 3 / min, driven to the argon station, argon purge time at the argon station 288s, argon flow rate 100m³ / min. 3 / min;

[0081] 4) The argon station sample concentration (S) was 0.132%, which did not meet the requirements for entering the LF furnace (S < 0.050%). The argon station underwent secondary treatment, adding 2222 kg of quicklime and 111 kg of aluminum powder. The secondary argon blowing time was 410 s, and the argon flow rate was 100 m³ / s. 3 / min, proceed to the next process;

[0082] 5) The sample taken from the LF furnace is S=0.0111%. 165kg of fluorite is added to the LF furnace, bringing the total amount of fluorite added to 365kg. 826kg of quicklime is added, bringing the total amount added to 2826kg. After LF treatment, S=0.015%, which is in line with the composition. The sample is then cast on the casting machine. The casting machine shows S=0.015%, which meets the requirements for the steel grade.

[0083] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for desulfurizing ultra-high sulfur molten iron, characterized in that, Includes the following steps: (1) After slag removal, the molten iron is added to the converter for smelting, and active lime is added. (2) During the steelmaking alloying process, aluminum powder is added and aluminum wire segments are added. During the converter steelmaking process, active lime is added and argon is blown into the ladle. (3) The steel ladle was moved to the argon station and desulfurized by adding quicklime and aluminum powder; (4) The molten steel is fed into the LF furnace for refining, and desulfurization is carried out by adding fluorite and quicklime; In step (2), the amount of active lime added during the converter tapping process is: When the final sulfur content of the converter is ≥0.0500%, the amount of active lime added = 2.5 + 2 × (final sulfur content of the converter - 0.050%) × 2000, unit: kg / t steel; When the final sulfur content of the converter is <0.050%, the amount of active lime added is 2.5 kg / t steel; The amount of aluminum powder added during the converter alloying process is: When the final sulfur content at the converter is ≥0.050%, the amount of aluminum powder added is = (final sulfur content at the converter - 0.050%) × 500 kg / t steel; when the final sulfur content at the converter is <0.050%, no aluminum powder is added after tapping the steel from the converter. The amount of aluminum segment added during the converter alloying process is: When the sulfur content at the converter endpoint is ≥0.050%, the amount of aluminum wire segment added is = (sulfur content at the converter endpoint - 0.050%) × 500 kg / t steel; when the sulfur content at the converter endpoint is <0.050%, no additional aluminum wire segment is required when tapping steel from the converter. In step (2), the method for argon blowing into the ladle is as follows: The argon blowing time during the tapping process is: When the sulfur content at the converter endpoint is ≥0.050%, the argon blowing time during tapping is 120 + (sulfur content at the converter endpoint - 0.050%) × 100000, in seconds. The final sulfur content of the converter is <0.050%, and the argon blowing time during the tapping process is 120s; The argon blowing flow rate during the steel tapping process is 80 ± 0.5 m³ / s. 3 / min; The argon blowing time after tapping is: When the sulfur content at the converter endpoint is ≥0.050%, the argon blowing time after tapping is 0.8 × (sulfur content at the converter endpoint - 0.050%) × 200000, unit: s; The final sulfur content of the converter is <0.050%, and the argon blowing time after tapping is 0s; The argon blowing flow rate after tapping is 80±0.5m³. 3 / min; The argon blowing time at the argon station is: When the final sulfur content of the converter is ≥0.050%, the argon blowing time at the argon station = 150 + (final sulfur content of the converter - 0.050%) × 100000, unit: s; The final sulfur content of the converter is <0.050%, and the argon blowing time at the argon station is 150s; The argon blowing flow rate at the argon station is 100 ± 0.5 m³ / s. 3 / min.

2. The desulfurization method for smelting ultra-high sulfur molten iron according to claim 1, characterized in that, In step (1), the relationship between the sulfur content of molten iron and the amount of slag removed is as follows: If 0.100% ≤ S in molten iron < 0.150%, remove 1 / 3 of the molten iron slag. If 0.150% ≤ molten iron S < 0.200%, remove 1 / 2 of the molten iron slag; If 0.200% ≤ S in molten iron < 0.250%, remove 3 / 4 of the molten iron slag. The molten iron has a sulfur content of ≥0.250%, and all molten iron slag is removed.

3. The desulfurization method for smelting ultra-high sulfur molten iron according to claim 1, characterized in that, In step (1), the relationship between the amount of active lime added and the sulfur content of the molten iron during the converter smelting process is as follows: The amount of active lime added = (sulfur content of molten iron - 0.100%) × 10000, unit: kg / t steel.

4. The desulfurization method for smelting ultra-high sulfur molten iron according to claim 1, characterized in that, In step (3), the amount of active lime added is: When the sulfur content in the argon station is ≥0.050%, the amount of quicklime to be added is calculated as (sulfur content in the argon station - 0.050%) × 10000, in kg / t steel. If the sulfur content in the argon station is <0.050%, no quicklime needs to be added. The amount of aluminum powder added is: When the sulfur content in the argon station is ≥0.050%, the amount of aluminum powder added = (sulfur content in the argon station - 0.050%) × 500, unit: kg / t steel; The sulfur content of the argon station is <0.050%, and no aluminum powder is added.

5. The desulfurization method for smelting ultra-high sulfur molten iron according to claim 1, characterized in that, In step (3), when the sulfur content of the argon station is ≥0.050%, a second argon blowing is performed. The second argon blowing time is = (sulfur content of the argon station - 0.050%) × 500000, unit: s; The argon blowing flow rate of the secondary argon station is 100±0.5m³. 3 / min.

6. The desulfurization method for smelting ultra-high sulfur molten iron according to claim 1, characterized in that, In step (4), the amount of fluorite added is: When the sulfur content at the LF furnace inlet is ≥0.050%, the amount of fluorite to be added is = (sulfur content at the LF furnace inlet - 0.050%) × 1000, unit: kg / t steel; when the sulfur content at the LF furnace inlet is <0.050%, no additional fluorite is required. The amount of quicklime to be added is: When the sulfur content at the LF furnace inlet is ≥0.050%, the amount of quicklime to be added is = (sulfur content at the LF furnace inlet - 0.050%) × 5000, unit: kg / t steel. When the sulfur content at the LF furnace inlet is <0.050%, no quicklime needs to be added.