Converter slag recycling and using method

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a method for recycling and utilizing converter slag. The method comprises the following steps: (1) after thermally braising the converter slag, screening the converter slag through a screening machine to obtain the converter slag with the diameter of less than 0.1 m; (2) the converter slag with the diameter smaller than 0.1 m is subjected to magnetic separation, and magnetic separation slag is obtained; and (3) the magnetic separation slag is conveyed to a converter stock bin and added into a converter for smelting in the blowing process. According to the method, the converter slag is used for converter smelting after magnetic separation, the converter smelting slagging effect can be improved, flux consumption is reduced, converter steel material consumption is reduced, and the smelting cost is reduced; and meanwhile, the converter slag is recycled, waste slag accumulation is avoided, and dust pollution is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy. Specifically, it particularly relates to a method for recycling and using converter slag. Background Art

[0002] In the actual production of steel mills, a large amount of converter slag is generated during converter smelting. Traditionally, these converter slags are often directly discharged after simple treatment. However, since converter slag contains a large amount of iron oxide and calcium oxide, such a treatment method will cause waste of resources. At the same time, the concentrated storage of a large amount of converter slag will pollute the environment. To address this problem, the treatment of converter slag is through hot smothering technology. However, most of the treated converter slag is still discharged as waste, and only part of the resources are utilized. This treatment method fails to make reasonable use of resources, resulting in serious waste of resources. Among the publicly available materials in China, some methods for recycling converter slag are introduced. Patent CN202211304862.4 discloses a comprehensive treatment method for converter waste slag, including pretreatment of converter slag, selection of converter slag treatment methods, crushing, separation, and screening of converter slag. Patent CN202311272252.5 discloses a method for treating converter slag. The converter slag undergoes two-stage crushing + three-stage screening, thereby improving the recovery quality of slag steel. The slag steel with a particle size greater than or equal to n and other parts can be used for different purposes respectively, achieving circular utilization and enhancing the environmental protection value. However, most of these methods focus on the treatment and recycling process of converter slag itself, and there is little discussion on how to further utilize the treated converter slag. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for recycling and using converter slag. The converter slag is recycled, subjected to magnetic separation, and then used in converter smelting, achieving improved slag melting effect in converter smelting, reducing flux consumption, lowering smelting costs, and reducing waste of resources.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows:

[0005] The present invention provides a method for recycling and using converter slag, and the method includes the following steps:

[0006] (1) After the converter slag is hot-smothered, it is screened by a screening machine to screen out converter slag with a diameter < 0.1 m;

[0007] (2) The converter slag with a diameter < 0.1 m is subjected to magnetic separation to obtain magnetically separated slag;

[0008] (3) The magnetically separated slag is transported to the converter bunker and added to the converter for smelting during the blowing process.

[0009] In the above technical solution, further, the magnetic separation slag is added according to the molten iron conditions during the blowing process. By mass percentage, the relationship between the Si content in the molten iron and the addition amount of the magnetic separation slag per ton of steel is as follows:

[0010] When the Si content in the molten iron is <0.2%, the addition amount of the magnetic separation slag is 11 ± 0.5 kg / ton of steel; the magnetic separation slag is added in three batches, where: the addition amount of the first batch is 40% - 50% of the total addition amount of the magnetic separation slag, the addition amount of the second batch is 25% - 30% of the total addition amount of the magnetic separation slag, and the addition amount of the third batch is 25% - 30% of the total addition amount of the magnetic separation slag;

[0011] When 0.2% ≤ Si < 0.4% in the molten iron, the addition amount of the magnetic separation slag is 9 kg ± 0.5 / ton of steel; the magnetic separation slag is added in three batches, where: the addition amount of the first batch is 50% - 55% of the total addition amount of the magnetic separation slag, the addition amount of the second batch is 25% - 30% of the total addition amount of the magnetic separation slag, and the addition amount of the third batch is 15 - 20% of the total addition amount of the magnetic separation slag;

[0012] When 0.4% ≤ Si < 0.6% in the molten iron, the addition amount of the magnetic separation slag is 7.5 ± 0.5 kg / ton of steel; the magnetic separation slag is added in three batches, where: the addition amount of the first batch is 55% - 60% of the total addition amount of the magnetic separation slag, the addition amount of the second batch is 25% - 30% of the total addition amount of the magnetic separation slag, and the addition amount of the third batch is 10% - 15% of the total addition amount of the magnetic separation slag;

[0013] When the Si content in the molten iron is ≥ 0.6%, the addition amount of the magnetic separation slag is 3.5 ± 0.5 kg / ton of steel; the magnetic separation slag is added in two batches, where: the addition amount of the first batch is 60% - 65% of the total addition amount of the magnetic separation slag, and the addition amount of the second batch is 35% - 40% of the total addition amount of the magnetic separation slag.

[0014] In the above technical solution, further, by mass percentage, when the Si content in the molten iron is Si < 0.6%, the blowing control process parameters are as follows:

[0015] The lance position at the start of blowing is 2900 - 3000 mm, the oxygen pressure at the start of blowing is 1.0 - 1.15 Mpa, and the oxygen flow rate is 53000 - 53500 N m 3 / h, blow for 60 - 70 s, add the first batch of quicklime and calcined dolomite, with the addition amount being 65% - 70% of the total addition amount. 10 - 15 s after feeding, lower the lance position to 2400 - 2450 mm. 30 - 40 s after feeding, add the first batch of magnetic separation slag, and simultaneously lower the lance position to 2150 - 2200 mm, lasting until 130 - 140 s of blowing. Then add the second batch of quicklime and calcined dolomite, with the addition amount being 30% - 40% of the total addition amount. 10 - 15 s after feeding, raise the lance position to 2250 - 2300 mm. 30 - 40 s after feeding, add the second batch of magnetic separation slag, and simultaneously lower the lance position to 2150 - 2200 mm, lasting for 30 - 40 s. Blow for 600 - 700 s, raise the lance position to 2900 - 3000 mm, add the third batch of magnetic separation slag. 30 - 40 s after feeding, lower the lance position to 2600 - 2700 mm, lasting for 30 - 40 s.

[0016] In the above technical solution, further, in terms of mass percentage, when the Si content in hot metal is Si ≥ 0.6%, the blowing control process parameters are as follows:

[0017] The initial blowing lance position is 2900 - 3000 mm, the initial blowing oxygen pressure is 1.0 - 1.15 Mpa, and the oxygen blowing flow rate is 53000 - 53500 N m 3 / h, blow for 60 - 70 s, add the first batch of quicklime and calcined dolomite, with the addition amount being 65% - 70% of the total addition amount. 10 - 15 s after feeding, lower the lance position to 2400 - 2450 mm. 30 - 40 s after feeding, add the first batch of magnetic separation slag, and simultaneously lower the lance position to 2150 - 2200 mm, lasting until 130 - 140 s of blowing. Then add the second batch of quicklime and calcined dolomite, with the addition amount being 30% - 40% of the total addition amount. 10 - 15 s after feeding, raise the lance position to 2250 - 2300 mm. 30 - 40 s after feeding, add the second batch of magnetic separation slag, and simultaneously lower the lance position to 2150 - 2200 mm, lasting for 30 - 40 s.

[0018] In the above technical solution, further, when the Si content in hot metal is Si < 0.2%, the total addition amount of quicklime is 25 ± 0.5 kg per ton of steel, and the total addition amount of calcined dolomite is 11 ± 0.5 kg per ton of steel.

[0019] In the above technical solution, further, when the Si content in hot metal is 0.2% ≤ Si < 0.6%, the total addition amount of quicklime = [25 + (hot metal silicon - 0.2) * 20] ± 0.5 kg per ton of steel, and the addition amount of calcined dolomite = [11 + (hot metal silicon - 0.2) * 15] ± 0.5 kg per ton of steel.

[0020] In the above technical solution, further, when the Si content of the hot metal is Si ≥ 0.6%, the total addition amount of the active lime is 33 ± 0.5 kg / ton of steel, and the total addition amount of the lightly burned dolomite is 17 ± 0.5 kg / ton of steel.

[0021] The method of the present invention is applicable to non-electric furnace steel grades with a sulfur content S ≥ 0.005% and all electric furnace steel grades.

[0022] The beneficial effects of the present invention are as follows:

[0023] 1. The method of the present invention uses the converter slag after magnetic separation for converter smelting, which can improve the slag melting effect in converter smelting, reduce the consumption of fluxes, reduce the consumption of iron and steel materials in the converter, and reduce the smelting cost;

[0024] 2. The method of the present invention fills the blank of the method for recycling and using converter slag by magnetic separation. At the same time, the recycling and use of converter slag avoid the accumulation of waste slag and reduce dust pollution. Detailed implementation mode

[0025] The following embodiments can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0026] Embodiment 1

[0027] Apply the converter slag to smelt the steel grade AYHS5. The amount of hot metal used is 260t, the Si content of the hot metal is 0.18%, and the amount of scrap steel used is 42.2t. The specific steps are as follows:

[0028] (1) After the converter slag generated during the converter smelting process is heat-soaked, it is screened by a screening machine to screen out the converter slag with a diameter < 0.1m. Among them, the converter slag with a diameter greater than 1m is directly used as slag steel, and the converter slag with 0.1m ≤ diameter ≤ 1m is directly used as selected granular iron;

[0029] (2) Magnetically separate the converter slag with a diameter < 0.1m, and select the slag with an iron content of 30 - 40%, and the remaining is disposed of as tail slag;

[0030] (3) Convey the magnetically separated slag to the converter bunker through a belt and add it to the converter during the blowing process for smelting. The magnetically separated slag should be loaded into the high-position bunker of the converter according to the requirements of the converter. The weighing quantity must be accurate, with an error of ±0.1t. Adjust the blanking slide plate to prevent slipping. The addition amount of the magnetically separated slag in this furnace is 3.05t;

[0031] (4) After the converter scrap steel and hot metal are charged, start to lower the lance to blow oxygen. The lance position at the start of blowing is 2960mm, the oxygen pressure at the start of blowing is 1.05Mpa, and the oxygen flow rate is 53000 Nm 3 / h. After successful ignition, 4,725 kg of the first batch of quicklime and 2,080 kg of lightly burned dolomite were added after 65 s of blowing. After 75 s of blowing, the lance position was lowered to 2,420 mm. After 95 s of blowing, 1,520 kg of the first batch of magnetic separation slag was added, and simultaneously the lance position was lowered to 2,200 mm and maintained until 134 s of blowing. Then, 2,025 kg of quicklime and 900 kg of lightly burned dolomite of the second batch were added. 10 s after adding the second batch of materials, the lance position was raised to 2,300 mm. 30 s after adding the second batch of materials, 760 kg of the second batch of magnetic separation slag was added, and simultaneously the lance position was lowered to 2,200 mm and maintained for 35 s. After 620 s of oxygen blowing, dry return occurred in the furnace, the lance position was raised to 2,950 mm, 770 kg of the third batch of magnetic separation slag was added. 30 s after adding, the lance position was lowered to 2,650 mm and maintained for 30 s, and the dry return phenomenon of the slag was alleviated, and the preparation process was tested.

[0032] (5) According to the automatic calculation and the actual situation of the on-site flame, when the oxygen accumulation reached 11,106 Nm 3 ³, a TSC test was carried out through the sublance. Blowing to the end point based on the TSC measurement data, the lance was lifted. The end point temperature was 1,688 °C, the oxygen value was 566 ppm. The detection results of the rapid analyzer were C = 0.041%, P = 0.0163%, Mn = 0.08%, S = 0.008%, meeting the requirements of the steel grade composition, and tapping quickly.

[0033] The steel grade smelted in this furnace belongs to a high-temperature and low-phosphorus steel grade, and the smelting difficulty is great. After adding the magnetic separation slag, the slag melting effect has been significantly improved, and the dephosphorization effect is obvious. This furnace saved 1,500 kg of quicklime. The price of quicklime is 430 yuan per ton, reducing the cost by about 700 yuan per month. At the same time, the total iron content in the magnetic separation slag is 30 - 40%, and the tapping volume of this furnace is 0.9 tons more, creating huge benefits.

[0034] Example 2

[0035] The converter slag was applied to smelt the steel grade Q235B. The amount of hot metal used was 260 t, and the Si content of the hot metal was 0.38%. The amount of scrap steel used was 38.2 t. The specific steps were as follows:

[0036] (1) After the converter slag generated during the converter smelting process was heat-soaked, it was screened by a screening machine to screen out the converter slag with a diameter < 0.1 m. Among them, the converter slag with a diameter greater than 1 m was directly used as slag steel, and the slag with 0.1 m ≤ diameter ≤ 1 m was directly used as selected granular iron.

[0037] (2) The converter slag with a diameter < 0.1 m was subjected to magnetic separation. The slag with an iron content of 30 - 40% was selected and the rest was disposed of as tail slag.

[0038] (3) The magnetic separation slag obtained after magnetic separation is conveyed to the converter bunker by belt and added to the converter during the blowing process for smelting. The magnetic separation slag should be loaded into the high-level bunker of the converter according to the requirements of the converter. The weighing quantity must be accurate, with an error of ±0.1t. Adjust the feeding slide plate to prevent material slipping. The addition amount of magnetic separation slag in this furnace is 2.45t;

[0039] (4) After the converter scrap and hot metal are charged, start blowing oxygen with the lance. The lance position at the start of blowing is 2980mm, the oxygen pressure at the start of blowing is 1.05Mpa, and the oxygen flow rate is 53000Nm 3 / h. After successful ignition, add the first batch of 5900kg of active lime and 2960kg of lightly burned dolomite after 60s of blowing. After 70s of blowing, lower the lance position to 2420mm. After 90s of blowing, add the first batch of 1225kg of magnetic separation slag, and simultaneously lower the lance position to 2200mm and continue until 138s of blowing. Then add the second batch of 2530kg of active lime and 1270kg of lightly burned dolomite. 10s after adding the second batch of materials, raise the lance position to 2350mm. 30s after adding the second batch of materials, add the second batch of 735kg of magnetic separation slag, and simultaneously lower the lance position to 2200mm and continue for 33s. After 680s of blowing, the phenomenon of slag drying back appears in the furnace. Raise the lance position to 3000mm, add the third batch of 490kg of magnetic separation slag. 30s after adding, lower the lance position to 2620mm and continue for 35s. The phenomenon of slag drying back is alleviated, and the preparation process is tested;

[0040] (5) According to the automatic calculation and the actual situation of the on-site flame, when the oxygen accumulation reaches 11516Nm 3 , conduct a TSC test through the sublance. Blow to the end point based on the TSC measurement data, raise the lance. The end point temperature is 1648°C, the oxygen value is 466ppm, and the test results of the rapid analyzer show that C = 0.041%, P = 0.0133%, Mn = 0.08%, S = 0.008%, meeting the requirements of the steel grade composition, and tap the steel quickly;

[0041] After adding the magnetic separation slag, the slag melting effect is significantly improved, and the dephosphorization effect is obvious. In this furnace, 1200kg of active lime is saved. The active lime is 430 yuan per ton, reducing the cost by 516 yuan per month. At the same time, the total iron content in the magnetic separation slag is 30 - 40%. The tapping amount of this furnace is 0.75t more, creating huge benefits.

[0042] Example 3

[0043] Apply the converter slag to smelt the steel grade SPCC. The amount of hot metal used is 260t, the Si content of the hot metal is 0.51%, and the amount of scrap used is 40.2t. The specific steps are as follows:

[0044] (1) After the converter slag generated in the converter smelting process is heat-soaked, it is screened by a screening machine to screen out converter slag with a diameter < 0.1 m. Among them, the converter slag with a diameter greater than 1 m is directly used as slag steel, and the slag with 0.1 m ≤ diameter ≤ 1 m is directly used as selected granular iron;

[0045] (2) The converter slag with a diameter < 0.1 m is subjected to magnetic separation. The slag with an iron content of 30 - 40% is selected and the rest is disposed of as tail slag;

[0046] (3) The magnetic separation slag obtained after magnetic separation is transported to the converter bunker by belt and added to the converter for smelting during the blowing process. The magnetic separation slag should be loaded into the high-position bunker of the converter according to the requirements of the converter. The weighing quantity must be accurate, with an error of ±0.1 t. Adjust the blanking flap to prevent material slipping. The amount of magnetic separation slag added in this furnace is 2.00 t;

[0047] (4) After the converter scrap and hot metal are charged, start blowing oxygen with the lance. The initial lance position is 3000 mm, the initial oxygen blowing pressure is 1.05 Mpa, and the oxygen blowing flow rate is 53000 Nm 3 / h. After successful ignition, add the first batch of active lime 5595 kg and light-burned dolomite 2590 kg after blowing for 68 s. After blowing for 78 s, lower the lance position to 2450 mm. After blowing for 98 s, add the first batch of magnetic separation slag 1200 kg, and simultaneously lower the lance position to 2200 mm and continue until blowing for 138 s. Then add the second batch of 2400 kg active lime and 1100 kg light-burned dolomite. 10 s after adding the second batch of materials, raise the lance position to 2350 mm. 30 s after adding the second batch of materials, add the second batch of magnetic separation slag 600 kg, and simultaneously lower the lance position to 2200 mm and continue for 30 s; Blow oxygen for 650 s. When back-drying occurs in the furnace, raise the lance position to 2900 mm, add the third batch of magnetic separation slag 200 kg. 30 s after adding, lower the lance position to 2620 mm and continue for 35 s. The back-drying phenomenon of the slag is alleviated, and the preparation process is tested;

[0048] (5) According to the automatic calculation and the actual situation of the on-site flame, when the oxygen accumulation reaches 11120 Nm 3 , conduct a TSC test through the sublance. Blow to the end point based on the TSC measurement data, raise the lance. The end point temperature is 1668 °C, the oxygen value is 510 ppm. The test results of the rapid analyzer show that C = 0.045%, P = 0.0153%, Mn = 0.08%, S = 0.008%, meeting the requirements of the steel grade composition, and quickly tap the steel;

[0049] After adding the magnetic separation slag, the slag melting effect is significantly improved, and the dephosphorization effect is obvious. In this furnace, 1800 kg of active lime is saved. The active lime is 430 yuan per ton, reducing the cost by 774 yuan per month. At the same time, the total iron content in the magnetic separation slag is 30 - 40%, and the steel output in this furnace is 0.65 t more, creating huge benefits.

[0050] Example 4

[0051] The converter slag is applied to smelt the steel grade SPHC. The amount of hot metal used is 260 t, the Si content of the hot metal is 0.66%, and the amount of scrap steel used is 41.2 t. The specific steps are as follows:

[0052] (1) After the converter slag generated in the converter smelting process is heat-soaked, it is screened by a screening machine to screen out the converter slag with a diameter < 0.1 m. Among them, the converter slag with a diameter greater than 1 m is directly used as slag steel, and the slag with 0.1 m ≤ diameter ≤ 1 m is directly used as selected granular iron;

[0053] (2) The converter slag with a diameter < 0.1 m is subjected to magnetic separation. The slag with an iron content of 30 - 40% is selected and the remaining is disposed of as tail slag;

[0054] (3) The magnetic separation slag obtained after magnetic separation is conveyed to the converter bin by belt and added to the converter during the blowing process for smelting. The magnetic separation slag should be loaded into the high-position bin of the converter according to the requirements of the converter. The weighing quantity must be accurate, with an error of ±0.1 t. Adjust the blanking slide plate to prevent material slipping. The amount of magnetic separation slag added in this furnace is 0.95 t;

[0055] (4) After the converter scrap and hot metal are charged, start blowing oxygen with the lance. The initial lance position is 3000 mm, the initial oxygen blowing pressure is 1.05 Mpa, and the oxygen blowing flow rate is 53000 Nm 3 / h. After successful ignition, add the first batch of active lime 6240 kg and light-burned dolomite 3210 kg after blowing for 68 s. After blowing for 78 s, lower the lance position to 2450 mm. After blowing for 98 s, add the first batch of magnetic separation slag 570 kg, and simultaneously lower the lance position to 2200 mm and continue until blowing for 138 s. Then add the second batch of 2670 kg active lime and 1375 kg light-burned dolomite. 10 s after adding the second batch of materials, raise the lance position to 2350 mm. 30 s after adding the second batch of materials, add the second batch of magnetic separation slag 380 kg, and simultaneously lower the lance position to 2200 mm and continue for 35 s for the preparation process test;

[0056] (5) According to the automatic calculation and the actual situation of the on-site flame, when the oxygen accumulation reaches 12120 Nm 3 , conduct a TSC test through the sublance. Blow to the end point based on the TSC measurement data, raise the lance, the end point temperature is 1682 °C, the oxygen value is 550 ppm, and the detection results of the rapid analyzer are C = 0.040%, P = 0.0173%, Mn = 0.09%, S = 0.005%, meeting the requirements of the steel grade composition, and quickly tap the steel;

[0057] After adding the magnetic separation slag, the slag melting effect is significantly improved, and the dephosphorization effect is obvious. In this furnace, 2100 kg of active lime is saved. The active lime is 430 yuan / t, reducing the cost by 903 yuan per month. At the same time, the total iron content in the magnetic separation slag is 30 - 40%, and the tapping amount of this furnace is 0.4 t more, creating huge benefits.

[0058] The above embodiments are only the preferred embodiments of the present invention and do not limit the implementation manners. The protection scope of the present invention shall be subject to the scope defined by the claims. Based on the above description, other different forms of changes or variations can be made. The obvious changes or variations derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for recovering and using converter slag, characterized in that: The method comprises the following steps: (1) After the converter slag is hot-stemmed, it is screened by a screening machine to screen out converter slag with a diameter of less than 0.1 m; (2) subjecting converter slag having a diameter of less than 0.1 m to magnetic separation to obtain magnetically separated slag; (3) The magnetic separation slag is transported to the converter silo and added to the converter for smelting during the blowing process.

2. The method for recovering and using converter slag according to claim 1, characterized in that: The magnetic separation slag is added during the blowing process according to the molten iron conditions. In terms of mass percentage, the relationship between the Si content in the molten iron and the amount of magnetic separation slag added per ton of steel is as follows: When Si in molten iron is less than 0.2%, the amount of magnetic slag added is 11±0.5kg / ton steel; the magnetic slag is added in three batches, wherein: the first batch is 40%-50% of the total amount of magnetic slag added, the second batch is 25%-30% of the total amount of magnetic slag added, and the third batch is 25%-30% of the total amount of magnetic slag added; When the molten iron content is 0.2%≤Si<0.4%, the amount of magnetic slag added is 9kg±0.5 / ton of steel; the magnetic slag is added in three batches, wherein the first batch is 50%-55% of the total amount of magnetic slag added, the second batch is 25%-30% of the total amount of magnetic slag added, and the third batch is 15-20% of the total amount of magnetic slag added; When the molten iron content is 0.4%≤Si<0.6%, the amount of magnetic slag added is 7.5±0.5kg / ton steel; the magnetic slag is added in three batches, wherein: the first batch is 55%-60% of the total amount of magnetic slag added, the second batch is 25%-30% of the total amount of magnetic slag added, and the third batch is 10%-15% of the total amount of magnetic slag added; When Si in molten iron is ≥0.6%, the amount of magnetic slag added is 3.5±0.5kg / ton steel; the magnetic slag is added in two batches, wherein: the first batch is 60%-65% of the total amount of magnetic slag added, and the second batch is 35%-40% of the total amount of magnetic slag added.

3. The method for recovering and using converter slag according to claim 2, characterized in that: When the Si content of molten iron is Si<0.6% in mass percentage, the blowing control process parameters are as follows: Blowing gun position 2900-3000mm, blowing oxygen pressure 1.0-1.15Mpa, blowing oxygen flow 53000-53500Nm 3 / h, blowing for 60-70s, add the first batch of active lime and light-burned dolomite, the amount added is 65%-70% of the total amount, 10-15s after adding, the gun position drops to 2400-2450mm, 30-40s after adding, add the first batch of magnetic separation slag, and synchronously drop the gun position to 2150-2200mm, continue until blowing for 130-140s, add the second batch of active lime and light-burned dolomite, the amount added is 30% of the total amount %-40%, 10-15s after feeding, the gun position is raised to 2250-2300mm, 30-40s after feeding, the second batch of magnetic separation slag is added, and the gun position is synchronously lowered to 2150-2200mm, which lasts for 30-40s, and refining is carried out for 600-700s, the gun position is raised to 2900-3000mm, and the third batch of magnetic separation slag is added. 30-40s after feeding, the gun position is lowered to 2600-2700mm, which lasts for 30-40s.

4. The method for recovering and using converter slag according to claim 2, characterized in that: In terms of mass percentage, when the Si content of molten iron is Si ≥ 0.6%, the blowing control process parameters are as follows: Blowing gun position 2900-3000mm, blowing oxygen pressure 1.0-1.15Mpa, blowing oxygen flow 53000-53500Nm 3 / h, blowing for 60-70s, add the first batch of active lime and light-burned dolomite, the addition amount is 65%-70% of the total addition amount, 10-15s after adding, the gun position drops to 2400-2450mm, 30-40s after adding, add the first batch of magnetic separation slag, synchronously the gun position drops to 2150-2200mm, and continue until 130-140s of blowing, add the second batch of active lime and light-burned dolomite, the addition amount is 30%-40% of the total addition amount, 10-15s after adding, the gun position is raised to 2250-2300mm, 30-40s after adding, add the second batch of magnetic separation slag, synchronously the gun position drops to 2150-2200mm, and continue for 30-40s.

5. The method for recovering and using converter slag according to claim 3, characterized in that: When the Si content of molten iron is Si<0.2%, the total amount of active lime added is 25±0.5kg / ton of steel, and the total amount of light-burned dolomite added is 11±0.5kg / ton of steel.

6. The method for recovering and using converter slag according to claim 3, characterized in that: When the Si content of molten iron is 0.2%≤Si<0.6%, the total amount of active lime added = [25 + (molten iron silicon - 0.2) * 20] ± 0.5 kg / ton of steel, and the amount of light-burned dolomite added = [11 + (molten iron silicon - 0.2) * 15] ± 0.5 kg / ton of steel.

7. The method for recovering and using converter slag according to claim 4, characterized in that: When the Si content of molten iron is Si≥0.6%, the total amount of active lime added is 33±0.5kg / ton of steel, and the total amount of light-burned dolomite added is 17±0.5kg / ton of steel.