Converter low-cost high-efficiency dephosphorization method based on composite process regulation and control

Abstract

The invention discloses a low-cost and high-efficiency converter dephosphorization method based on composite process regulation and control. A dynamic matching model of molten iron components and a slagging system is established, oxygen lance process optimization with specific parameters is combined, and specially-made sludge balls are added in the middle stage of blowing to reinforce slag steel reaction. A high scrap steel ratio and temperature-phosphorus content coupling control model is innovatively developed, and the phosphorus content at the end point is stabilized to be smaller than or equal to 0.030% in cooperation with slag remaining operation and quality strengthening measures of a conventional slag stopping cone. Compared with a traditional method, consumption of slagging materials is reduced, the dephosphorization rate is increased to 73.7%, and equipment investment does not need to be newly increased. The method is especially suitable for low-cost and high-efficiency dephosphorization production of small and medium-sized converters.

Description

Technical Field

[0001] The invention relates to the technical field of converter steelmaking, and in particular to a low-cost and high-efficiency converter dephosphorization method based on composite process control. Background Art

[0002] Phosphorus, a harmful element in steel, significantly reduces the ductility and toughness of steel (especially the "cold brittleness" phenomenon at low temperatures), and phosphorus segregation in steel is difficult to eliminate through subsequent processes. Since blast furnace ironmaking cannot effectively remove phosphorus (blast furnaces use a reducing atmosphere and have poor dephosphorization capabilities), converter steelmaking has become the core link in dephosphorization. With the stringent requirements for phosphorus content (usually ≤0.015%) for high-value-added steel grades such as automotive plates and pipeline steel, the development of low-cost, efficient dephosphorization processes has become a technical priority for the steel industry.

[0003] Existing converter dephosphorization processes mainly use the following methods: the single slag method completes dephosphorization through a one-time slag production, which is suitable for low-carbon steel (carbon content ≤ 0.05%). The final phosphorus content can be controlled at 0.01% to 0.02%, but dephosphorization of high-carbon steel is difficult; the double slag method has two stages of slag production. After the initial dephosphorization, some slag is poured out before entering the decarburization stage. This method can reduce lime consumption by more than 30%, but the smelting cycle is extended, and it is difficult to match the slag pouring temperature with the alkalinity. The double slag method (MURC) uses two converters for dephosphorization and decarburization respectively, which can achieve ultra-low phosphorus steel (P ≤ 0.005%), but the equipment utilization rate is high and the cost is significantly increased.

[0004] Limited equipment makes it difficult for small and medium-sized steel mills to adopt advanced technologies such as RH vacuum treatment. Traditional single-slag methods suffer from low dephosphorization rates (approximately 60%), high lime consumption, and unstable endpoint control. Especially when processing high-phosphorus hot metal (P>0.10%), dry-out and splashing are common, disrupting smooth production. Therefore, there is an urgent need to develop a low-cost, efficient dephosphorization process. Summary of the Invention

[0005] The present invention provides a converter high scrap ratio dephosphorization method based on staged kinetic control. The core of the method is to establish a dynamic matching system of "oxygen supply intensity-scrap ratio-slag phase evolution". The specific process is as follows:

[0006] a) Use a mixing furnace to mix the molten iron components and control the temperature and phosphorus content fluctuations;

[0007] b) Scrap steel ratio control: Increase the scrap steel ratio on the basis of meeting the converter heat balance to ensure the comprehensive phosphorus content of the metal material;

[0008] c) Establish a dynamic slag-making model: determine the reference amount of metallurgical lime to be added based on the silicon content of the molten iron entering the furnace;

[0009] d) Blowing stage control:

[0010] Stage I: Rapid slag formation by high oxygen pressure shock, with initial slag FeO>20%;

[0011] Phase II: Enhanced dephosphorization with sludge balls and dynamic adjustment of oxygen supply intensity;

[0012] Phase III: Real-time adjustment of alkalinity based on furnace gas analysis (CO / CO2) to stabilize the endpoint phosphorus content.

[0013] e) Endpoint temperature control: Establish a temperature control model and adjust the endpoint temperature based on the target phosphorus content. T = 1630 + 10 × (0.03 - P target), where P target is the target phosphorus content.

[0014] f) Combine the slag retention operation with the single slag dephosphorization process to retain part of the final slag in the furnace, and perform the slag splashing operation while controlling the FeO content of the final slag to avoid splashing when adding iron.

[0015] Preferably, the step a) of controlling the temperature and phosphorus content fluctuations specifically involves controlling the molten iron temperature in the mixing furnace to be ≥1280° C. and maintaining the molten iron phosphorus content fluctuation to be ≤±0.01%.

[0016] Preferably, the specific steps of increasing the scrap steel ratio in step b) are: cutting the scrap steel into blocks of 500×500 mm or less, preheating the scrap steel entering the furnace to a temperature of ≥400°C using pre-furnace scrap steel, and increasing the scrap steel ratio entering the furnace by increasing the scrap steel temperature.

[0017] Preferably, the dynamic slag making model described in step c) is that when the phosphorus content of molten iron P∈0.10%, 0.12%, the corrected amount of lime added is the additional amount = (0.8+13P)×tons of molten iron weight (kg / furnace), and the amount of lime is reduced by 2kg / t for every 1% increase in the scrap steel ratio.

[0018] Preferably, step d) uses a four-hole Laval oxygen lance with a nozzle angle of 11.3±0.1°; the oxygen supply intensity is controlled in stages: the blowing period (0-3min) is 4.5±0.2Nm 3 / (min·t), the main blowing period (3-12min) dropped to 3.5±0.1Nm 3 / (min·t).

[0019] Preferably, the specific steps of stage II in step d) are as follows: stage II (3-8 min, main dephosphorization period): reducing the oxygen supply intensity to 3-4 and prolonging the molten pool reaction time. 3 / (min·t), the gun position is lowered to 0.75-0.85m and adjusted according to the dynamic reaction in the furnace. Sludge balls are added in batches to promote slagging and replenish FeO to avoid back drying.

[0020] Preferably, in step d) of stage III, the slag addition is adjusted in real time based on furnace gas analysis (CO / CO2 ratio), and the basicity control function is:

[0021] R=2.6+0.12t+0.05Δ[P]

[0022] Where t is the smelting time (min), and Δ[P] is the deviation between the instantaneous phosphorus content and the target value.

[0023] Preferably, the sludge balls in step d) are added by adding sludge balls with a particle size of 30-50 mm at 3-8 minutes of blowing, with an addition amount of 0.8-1.2 kg / t steel;

[0024] Preferably, in step f), the FeO content in the final slag is controlled to be ≤25%.

[0025] Preferably, the sludge balls in step d) contain the following components by weight: TFe 50-54%, CaO 8-12%, SiO25-10%, and moisture ≤3%.

[0026] Preferably, the staged oxygen supply in step d) includes: the basic lance position at 0.70m to 0.85m (from the liquid surface), the slagging lance position at 0.95m to 1.5m, and the carbon pulling lance position at 0.70m to 0.80m. The terminal lance pressure time is preferably greater than 20 seconds. The basic lance position is the main blowing lance position, and the high lance position is preferably used for rapid slagging during the start-up blowing period.

[0027] Beneficial effects

[0028] The present invention discloses a low-cost and efficient dephosphorization method for a converter based on composite process control. By establishing a dynamic matching model between molten iron composition and slag-making system, combined with the optimization of oxygen lance process with specific parameters, special sludge balls are added in the middle stage of blowing to enhance the slag-steel reaction. An innovative high scrap ratio and temperature-phosphorus content coupling control model is developed, combined with slag retention operation and quality enhancement measures for conventional slag cones to achieve a stable end-point phosphorus content of ≤0.030%. Compared with traditional methods, slag material consumption is reduced, the dephosphorization rate is increased to 73.7%, and no new equipment investment is required. It is particularly suitable for low-cost and efficient dephosphorization production in small and medium-sized converters. Core breakthroughs include:

[0029] Dynamic matching model

[0030] A dynamic matching model between molten iron composition and slag-making system was established to optimize slag-to-material ratio and oxygen supply parameters in real time for precise dephosphorization. A temperature-phosphorus content coupling control model was developed, combined with tapping temperature optimization (1630°C) to inhibit rephosphorization and reduce energy consumption.

[0031] Oxygen lance process optimization

[0032] The oxygen supply intensity and gun position parameters are regulated in stages (dynamic adjustment from high to medium to low) to enhance the molten pool reaction efficiency and promote rapid slag formation of high FeO slag in the initial stage.

[0033] Special sludge balls to enhance dephosphorization

[0034] Special sludge balls are added in batches during the middle stage of blowing to supplement FeO and strengthen the slag-steel interface reaction, solving the dry-back problem of the traditional process and increasing the dephosphorization rate to 73.7%.

[0035] High scrap ratio process

[0036] Through scrap steel pretreatment (size control + preheating to ≥400℃), the scrap steel ratio is significantly improved, the phosphorus content of the metal material is controlled, and the phosphorus brought into the furnace is reduced.

[0037] Slag retention and slag blocking to improve quality

[0038] The slag retention operation is adopted to recycle the final slag, combined with the single slag dephosphorization process, and the conventional slag stop cone is used to accurately control the slag amount, and the slag splashing operation is performed to control the FeO content of the final slag to ≤25%, avoiding splashing when adding iron.

[0039] In summary, through dynamic model matching + process parameter optimization + material coordinated regulation, the problems of low dephosphorization efficiency and high cost of traditional converters have been innovatively solved, achieving low-cost and efficient production. It is suitable for green and efficient steelmaking in small and medium-sized converters and has significant economic and environmental value. DETAILED DESCRIPTION

[0040] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention.

[0041] Example 1:

[0042] 60t converter, hot metal phosphorus 0.114%

[0043] Step 1: Take samples after mixing in the iron mixing furnace, the phosphorus content of molten iron is 0.113% ± 0.005%

[0044] Step 2: According to the converter heat balance, the scrap steel addition amount is determined to be 14.79 tons, and the scrap steel ratio is 23%.

[0045] Step 3: Calculate the amount of lime added = (0.8 + 13 × 0.113) × 49.52 = 2.269 × 49.52 = 112.36 kg / furnace

[0046] Step 4: Use an 11.3° four-hole oxygen gun with an oxygen supply intensity of 4.5Nm 3 / (min·t)

[0047] Step 5: After blowing for 5 minutes, add 50kg of sludge balls (composition: TFe 51%, CaO 11%, SiO2 10%) in two batches.

[0048] Step 6: The final temperature is controlled at 1630°C.

[0049] After practical application, the end point phosphorus content was stabilized at 0.025-0.030%, and the dephosphorization rate was 73.5%.

[0050] As can be seen from the above examples, the low-cost, high-efficiency converter dephosphorization method provided by the present invention, based on composite process control, achieves a stable endpoint phosphorus content of ≤0.030%. Compared with traditional methods, slag material consumption is reduced, the dephosphorization rate is increased to 73.7%, and no additional equipment investment is required. This method is particularly suitable for low-cost, high-efficiency dephosphorization production in small and medium-sized converters.

[0051] The above description is only the best embodiment of the present invention. It should be noted that, for those skilled in the art, without departing from the principles of the present invention, the technical solution of the present invention may be modified or replaced with equivalents, which can still achieve the technical effects of the present invention and should also be considered to fall within the scope of protection of the present invention.

Claims

1. A low-cost and high-efficiency dephosphorization method for a converter based on composite process control, characterized in that: The following steps are involved: a) Use a mixing furnace to mix the molten iron components and control the temperature and phosphorus content fluctuations; b) Scrap steel ratio control: Increase the scrap steel ratio on the basis of meeting the converter heat balance to ensure the comprehensive phosphorus content of the metal material; c) Establish a dynamic slag-making model: determine the reference amount of metallurgical lime to be added based on the silicon content of the molten iron entering the furnace; d) Blowing stage control: Stage I: Rapid slag formation by high oxygen pressure shock, with initial slag FeO>20%; Phase II: Enhanced dephosphorization with sludge balls and dynamic adjustment of oxygen supply intensity; Phase III: Real-time adjustment of alkalinity based on furnace gas analysis (CO / CO2) to stabilize the endpoint phosphorus content. e) Endpoint temperature control: Establish a temperature control model and adjust the endpoint temperature based on the endpoint target phosphorus content. T = 1630 + 10 × (0.03 - P target), where P target is the endpoint target phosphorus content. f) Combine the slag retention operation with the single slag dephosphorization process to retain part of the final slag in the furnace, and perform the slag splashing operation while controlling the FeO content of the final slag to avoid splashing when adding iron.

2. The preparation method according to claim 1, characterized in that The step a) controlling the temperature and phosphorus content fluctuations specifically includes controlling the molten iron temperature in the mixing furnace to be ≥1280° C. and maintaining the molten iron phosphorus content fluctuation to be ≤±0.01%.

3. The preparation method according to claim 1, characterized in that The specific steps of increasing the scrap steel ratio in step b) are: cutting the scrap steel into blocks of less than 500×500 mm, preheating the scrap steel in front of the furnace to a temperature of ≥400°C, reducing the heat loss caused by the scrap steel, and creating favorable conditions for increasing the scrap steel ratio.

4. The preparation method according to claim 1, characterized in that The dynamic slag forming model described in step c) is that when the phosphorus content of molten iron P∈0.10%, 0.12%, the corrected lime addition amount is added amount = (0.8 + 13P) × molten iron weight tons (kg / furnace), and the amount of lime is reduced by 2kg / t for every 1% increase in the scrap ratio.

5. The preparation method according to claim 1, characterized in that Step d) uses a four-hole Laval oxygen lance with a nozzle angle of 11.3±0.1°; the oxygen supply intensity is controlled in stages: the blowing period (0-3min) is 4.5±0.2Nm 3 / (min·t), the main blowing period (3-12min) dropped to 3.5±0.1Nm 3 / (min·t).

6. The preparation method according to claim 1, characterized in that In step d) of stage III, the slag addition is adjusted in real time based on the furnace gas analysis (CO / CO2 ratio). The basicity control function is: R=2.6+0.12t+0.05Δ[P] Where t is the smelting time (min), and Δ[P] is the deviation between the instantaneous phosphorus content and the target value.

7. The preparation method according to claim 1, characterized in that The sludge balls described in step d) are added as follows: sludge balls with a particle size of 30-50 mm are added at a rate of 0.8-1.2 kg / t at 3-8 minutes of blowing; the sludge balls contain the following components by weight: TFe 50-54%, CaO 8-12%, SiO2 5-10%, and moisture ≤3%.

8. The preparation method according to claim 1, characterized in that In step e), the FeO content in the final slag is controlled to be ≤25%.

9. The preparation method according to claim 1, characterized in that The staged oxygen supply in step d) includes: the basic lance position is 0.70m to 0.85m (from the liquid surface), the slagging lance position is 0.95m to 1.5m, and the carbon pulling lance position is 0.70m to 0.80m. The terminal lance pressure time is greater than 20 seconds. The basic lance position is the main blowing lance position, and the high lance position is used for rapid slagging during the blowing period.