Method for efficient utilization of aod de-ironed slag

Abstract

The present application belongs to the technical field of solid waste recycling, and provides a method for efficient utilization of AOD deironing slag, wherein the deironing slag produced by AOD smelting is first cooled by water and then crushed into slag blocks; the crushed deironing slag blocks are then dried and dehydrated and added into a high-position stock bin of a steelmaking converter; then, after the converter is loaded with molten iron and scrap steel, oxygen is blown by a top lance and nitrogen is blown at the bottom for smelting; after the composition and temperature of the molten steel in the converter reach the requirements, the molten steel is tapped. The present method mainly solves the problem that the high-iron-content slag produced in the deironing process cannot be effectively utilized, thereby causing resource waste; by adding the deironing slag in the converter smelting process, the converter can reduce the amount of scrap steel to be added, thereby reducing the smelting cost, and at the same time, the solid waste is returned for utilization, thereby reducing environmental pollution.

Description

Technical Field

[0001] This invention belongs to the field of solid waste recycling technology, and relates to the return of iron-containing de-iron slag with high iron content to the converter for reuse. Specifically, it is a method for the efficient utilization of AOD de-iron slag. Background Technology

[0002] In the smelting of high-nickel stainless steel and nickel-based alloys, pure nickel and high-nickel ferronickel (Ni≥30%) are added. These high-nickel raw materials are expensive and scarce. To address this, some companies use AOD (Alternating Dry Ore) to charge molten nickel-iron produced by RKEF (Refined Metallurgical Equipment) for de-ironization and nickel enrichment. This process generates a large amount of high-iron-content de-ironized slag, with the following composition: FeO: 60-80%, CaO: 8-18%, SiO2: 1-3%, MgO: 3-8%, containing a significant amount of iron. The conventional slag treatment method involves mixing the de-ironized slag with carbon steel smelting slag, and then using the sorted steel slag as paving material or as a raw material for cement production, resulting in a waste of iron resources. Summary of the Invention

[0003] The purpose of this invention is to provide a method for the efficient utilization of AOD de-ironizing slag. AOD de-ironizing slag is used as raw material for converter smelting. It is added during the converter decarburization process and the FeO in the slag is reduced by the C in the converter molten iron. This fully recovers the iron element in the de-ironizing slag with high iron content. At the same time, the oxygen content of FeO in the slag is used to replace oxygen supply, thereby improving the slag formation, dephosphorization and decarburization speed in converter smelting and reducing oxygen consumption.

[0004] The technical solution adopted by the present invention to achieve the above objectives is as follows: A method for efficient utilization of AOD (Anaerobic Ore Depletion) slag includes the following steps: S1. Iron removal slag crushing: The iron removal slag produced by AOD smelting is cooled with water and then crushed into slag blocks. S2. Iron removal slag is loaded into the high-level silo: After the crushed iron removal slag is dried and dehydrated, it is added into the high-level silo of the converter in the steel plant. S3. Use of de-iron slag: After the converter is loaded with molten iron and scrap steel, oxygen is blown from the top lance and nitrogen is blown from the bottom lance for smelting. S4. After the composition and temperature of the molten steel in the converter reach the required level, the steel is tapped.

[0005] Furthermore, the diameter of the crushed slag in S1 ranges from 10mm to 80mm; Furthermore, the oxygen supply position of the top lance in the S3 converter adopts a low-high-low position, and the bottom blowing nitrogen adopts a high flow rate and high intensity. Furthermore, the control process for the gas supply mode of the top and bottom lances in the S3 converter and the amount of de-iron slag added is as follows: S31. Smelting desiliconization period: During the blowing process, add 10-12 kg / t of desiliconization slag from a high position within 0-4 min of blowing. The top lance position of the converter is 1700-1800 mm, and the bottom blowing gas supply intensity is 0.12-0.15 Nm3 / (min·t). The desiliconization rate is increased by oxidizing silicon in the iron water with FeO in the desiliconization slag. The reaction formula is: 2(FeO)+[Si]=2[Fe]+(SiO2). S32. During the mid-stage of smelting, i.e., within 5 to 12 minutes of blowing, 16 to 20 kg / t of de-iron slag is added in batches from a high position. The top lance position of the converter is 2000 mm, and the bottom blowing gas supply intensity is 0.10 to 0.13 Nm3 / (min·t). The FeO in the de-iron slag reacts with [C] and [P] in the molten steel to increase the decarburization and dephosphorization rate. The reaction formulas are (FeO) + [C] = [Fe] + CO↑, 5(FeO) + 2[P] = 5[Fe] + (P2O5). S33. In the later stage of smelting, i.e. within 13 to 18 minutes of blowing, no more iron removal slag is added, the top lance position of the converter is 1600mm, the bottom blowing gas supply intensity is 0.13 to 0.15 Nm3 / (min·t), and the bottom blowing gas is switched to Ar gas.

[0006] Furthermore, lime is added in batches during the smelting process to control the slag alkalinity at 3.0–3.2.

[0007] The beneficial effects of this invention are as follows: 1. Adding de-iron slag during the converter smelting process allows the FeO in the slag to be reduced by the [C] and [Si] in the converter molten iron, thus recovering the iron element. This can replace scrap steel and reduce smelting costs.

[0008] 2. By utilizing the oxygen content of FeO in the slag to replace oxygen supply, the decarburization and dephosphorization speed of the converter is improved, the oxygen consumption of the converter is reduced, and the efficient utilization of de-iron slag is achieved. 3. The AOD (Alternating Oxide Desulfurization) process for returning iron slag to the converter achieves the goal of leaving the plant without solid waste, thus reducing environmental pollution. Detailed Implementation

[0009] The present invention will be further described below with reference to embodiments: The method for efficient utilization of AOD (Anaerobic De-oxidation) slag includes the following steps: S1. Iron removal slag crushing: The iron removal slag produced by AOD smelting is cooled with water and then crushed into slag blocks with a diameter range of 10mm-80mm. S2. Iron removal slag is loaded into the high-level silo: After the crushed iron removal slag is dried and dehydrated, it is added into the high-level silo of the converter in the steel plant. S3. Use of de-iron slag: After the converter is loaded with molten iron and scrap steel, oxygen is blown from the top lance and nitrogen is blown from the bottom lance for smelting. The oxygen supply lance position of the top lance of the converter adopts a low-high-low position, and the bottom blowing adopts a high flow rate gas supply intensity. The process for controlling the gas supply mode of the converter top and bottom lances and the amount of de-iron slag added is as follows: S31. Smelting desiliconization period: During the blowing process, add 10-12 kg / t of desiliconization slag from a high position within 0-4 min of blowing. The top lance position of the converter is 1700-1800 mm, and the bottom blowing gas supply intensity is 0.12-0.15 Nm3 / (min·t). The desiliconization rate is increased by oxidizing silicon in the iron water with FeO in the desiliconization slag. The reaction formula is: 2(FeO)+[Si]=2[Fe]+(SiO2). S32. During the mid-stage of smelting, i.e., within 5 to 12 minutes of blowing, 16 to 20 kg / t of de-iron slag is added in batches from a high position. The top lance position of the converter is 2000 mm, and the bottom blowing gas supply intensity is 0.10 to 0.13 Nm3 / (min·t). The FeO in the de-iron slag reacts with [C] and [P] in the molten steel to increase the decarburization and dephosphorization rate. The reaction formulas are (FeO) + [C] = [Fe] + CO↑, 5(FeO) + 2[P] = 5[Fe] + (P2O5). S33. In the later stage of smelting, i.e. within 13 to 18 minutes of blowing, no more de-slag is added. The top lance position of the converter is 1600 mm, the bottom blowing gas supply intensity is 0.13 to 0.15 Nm3 / (min·t), the bottom blowing gas is switched to Ar gas, and lime is added in batches during the smelting process to control the slag basicity at 3.0 to 3.2.

[0010] S4. After the composition and temperature of the molten steel in the converter reach the required level, the steel is tapped. Example 1

[0011] Carbon steel is smelted using a 180-ton converter with de-ferroalved slag. The implementation method is as follows: S1. Iron removal slag crushing: The iron removal slag removed during the AOD smelting process is sent to the slag yard in a slag pot. Water is used to cool the slag, and a crusher is used to crush the iron removal slag into slag blocks of 10-80mm.

[0012] S2. Placing the de-iron slag into the high-level silo: After drying and dehydrating the crushed de-iron slag, it is transported to the high-level silo of the 180-ton converter in the steel plant.

[0013] S3. Use of de-iron slag: After the converter is charged with 160 tons of molten iron and 25 tons of scrap steel, oxygen blowing smelting begins. The converter top lance position is 1800mm, and the bottom blowing gas flow rate is 24 Nm3 / min. 2000 kg of de-iron slag and 2000 kg of lime are added from the top position. After 4 minutes of blowing, when large-scale decarburization begins, the converter top lance position is raised to 2000mm, and 2800 kg of de-iron slag is added in batches from the top position. The bottom blowing gas flow rate is 21.5 Nm3 / min. The FeO in the de-iron slag is used to increase the decarburization and dephosphorization rate. After 13 minutes of blowing, the converter top lance position is adjusted to 1600mm, and the bottom blowing gas is switched to Ar gas with a bottom blowing gas flow rate of 27 Nm3 / min. After the composition and temperature of the molten steel in the converter meet the requirements of the specifications, the steel is tapped.

[0014] Adding 4.8 tons of de-iron slag to each furnace of a 180-ton converter can reduce the amount of scrap steel added by 3.1 tons and lower the smelting cost by 30 yuan / ton. Example 2

[0015] Carbon steel is smelted using an 80-ton converter with de-iron slag. S1. Iron removal slag crushing: The iron removal slag removed during the AOD smelting process is sent to the slag yard in a slag pot. Water is used to cool the slag, and a crusher is used to crush the iron removal slag into slag blocks of 10-80mm.

[0016] S2. Placing the de-iron slag into the high-level silo: After drying and dehydrating the crushed de-iron slag, it is transported to the high-level silo of the 180-ton converter in the steel plant.

[0017] S3. Use of De-iron Slag: After charging the converter with 73 tons of molten iron and 10 tons of scrap steel, oxygen blowing smelting begins. The converter top lance position is 1800mm, and the bottom blowing gas flow rate is 10 Nm3 / min. 1000 kg of de-iron slag is added from the top position, along with 800 kg of lime. After 4 minutes of blowing, when significant decarburization begins, the converter top lance position is raised to 2000mm, and 1300 kg of de-iron slag is added in batches from the top position, with the bottom blowing gas flow rate remaining at 10 Nm3 / min. The FeO in the de-iron slag enhances the decarburization and dephosphorization effects. After 13 minutes of blowing, the converter top lance position is adjusted to 1600mm, and the bottom blowing gas is switched to Ar gas, with a bottom blowing gas flow rate of 12 Nm3 / min. After the composition and temperature of the molten steel in the converter meet the requirements of the specifications, the steel is tapped.

[0018] Adding 2.6 tons of de-iron slag to each 80-ton converter can reduce the amount of scrap steel added by 1.6 tons and lower the smelting cost by 35 yuan / ton.

[0019] Practical application in production has proven that by adopting this method, the amount of scrap steel added to the converter can be reduced, smelting costs can be lowered, and solid waste can be recycled, thus reducing environmental pollution.

Claims

1. A method for efficient utilization of AOD (Anaerobic Oxide) de-ironizing furnace slag, characterized in that: Includes the following steps: S1. The slag produced by AOD smelting is cooled with water and then crushed into slag blocks. S2. Dry and dehydrate the crushed iron-removing slag blocks and add them to the high-level material silo of the steelmaking converter. S3. After the converter is loaded with molten iron and scrap steel, oxygen is blown from the top lance and nitrogen is blown from the bottom lance for smelting. S4. After the composition and temperature of the molten steel produced in the converter reach the required level, the steel is tapped.

2. The method for efficient utilization of AOD de-ironizing slag according to claim 1, characterized in that: The diameter of the crushed slag in S1 ranges from 10mm to 80mm.

3. The method for efficient utilization of AOD de-ironizing slag according to claim 1, characterized in that: The oxygen supply position of the top lance in the S3 converter changes from low to high and then back to low, while the bottom-blown nitrogen uses a high flow rate.

4. The method for efficient utilization of AOD de-ironizing slag according to claim 1, characterized in that: The process for controlling the gas supply mode of the top and bottom lances of the S3 converter and the amount of de-iron slag added is as follows: S31. During the blowing process from 0 min to 4 min, add 10 to 12 kg / t of de-iron slag from a high position, with the top lance position of the converter at 1700 to 1800 mm and the bottom blowing gas supply intensity at 0.12 to 0.15 Nm3 / (min·t). S32. During the blowing process, add 16-20 kg / t of de-iron slag in batches from a high position within 5-12 minutes. The top lance position of the converter is 2000 mm, and the bottom blowing gas supply intensity is 0.10-0.13 Nm3 / (min·t). S33. During the blowing process for 13-18 minutes, no more de-iron slag is added. The top lance position of the converter is 1600mm. The bottom blowing gas supply intensity is 0.13-0.15Nm3 / (min·t). The bottom blowing gas is switched to Ar gas.

5. A method for efficient utilization of AOD de-ironizing slag according to claim 4, characterized in that: Lime is added in batches during the smelting process to control the slag alkalinity at 3.0 to 3.2.