Efficient composite injection molten iron desulfurization method

Abstract

The invention discloses an efficient composite injection molten iron desulfurization method, which mainly solves the technical problem of high molten iron desulfurization cost in the existing magnesium-based composite injection molten iron desulfurization process. According to the technical scheme, the efficient composite injection molten iron desulfurization method comprises the following steps: 1) collecting parameters of inverted molten iron; (2) front injection is carried out, the injection powder is lime powder, a top spray gun is inserted into the molten iron in the ladle, the lime powder is injected, and front injection parameters are determined before the lime powder is injected; (3) composite injection is conducted, injection powder is lime powder and magnesium powder, after front injection is finished, the lime powder and the magnesium powder are injected into the molten iron in the ladle at the same time, and composite injection parameters are determined before the lime powder and the magnesium powder are injected; 4) carrying out post-injection, wherein the injection powder is lime powder; and (5) after the post-blowing is finished, the spray gun is lifted. According to the method, high-efficiency and low-cost desulfurization of the molten iron is realized by adopting a lime powder desulfurization mode in a front injection stage.

Description

Technical Field

[0001] The invention relates to a molten iron pretreatment desulfurization technology, in particular to a high-efficiency composite molten iron desulfurization method by injection, and belongs to the technical field of iron and steel metallurgy. Background Art

[0002] The magnesium-based composite injection molten iron desulfurization process is one of the commonly used processes for molten iron pretreatment desulfurization. The powders used include magnesium powder and lime powder. The desulfurization process is divided into three stages: pre-injection, composite injection and post-injection: the pre-injection stage is a stage in which a certain amount of lime powder is injected alone after the injection starts; when the lime powder injection amount reaches the lime powder amount set in the pre-injection stage, lime powder and magnesium powder are injected at the same time, and this stage is the composite injection stage; when the magnesium powder injection amount reaches the set value, the magnesium powder injection is stopped and the lime powder injection is continued, and this stage is the post-injection stage; when the lime powder injection amount reaches the lime powder amount set in the post-injection stage, the lime powder injection is stopped, and the entire injection desulfurization process is ended.

[0003] In the existing composite injection hot metal desulfurization process, the amount of lime powder is relatively small, and it mainly plays the role of dispersing magnesium powder, slowing down the gasification rate of magnesium powder, preventing the spray gun from clogging and reducing the return of sulfur, while the removal of sulfur in hot metal depends on magnesium powder. The price of magnesium powder is high and is greatly affected by energy control. The highest price reaches 60,000 yuan / ton. Even under normal circumstances, the price of magnesium powder is more than 30 times that of lime powder, resulting in a high cost for hot metal desulfurization.

[0004] The Chinese patent application document with application publication number CN 107663560 A discloses a method for controlling the amount of lime powder in a magnesium-based composite injection molten iron desulfurization process. According to the principle that the injection time of magnesium powder and lime powder is the same, the composite injection stage is evenly divided into n sub-stages, and the difference between the actual injection amount and the target injection amount of lime powder is compared at the end of each sub-stage, and the target injection amount of lime powder in the composite injection stage is automatically corrected, and the lime powder dosage control accuracy is ±2kg; the amount of lime powder in the front injection stage of this technology is 0.24-0.40kg / ton of iron, and the lime powder injection rate is 30-50kg / min. The amount of lime powder in the front injection stage is small, and most of the lime powder floats to the surface of the molten iron and enters the slag to increase the alkalinity and sulfur capacity of the molten iron slag, and cannot play an effective desulfurization role. Summary of the invention

[0005] The purpose of the present invention is to provide a high-efficiency composite injection molten iron desulfurization method, which mainly solves the technical problem of high molten iron desulfurization cost in the existing magnesium-based composite injection molten iron desulfurization process; the method of the present invention realizes high-efficiency and low-cost desulfurization of molten iron; and solves the technical problem of high molten iron desulfurization cost caused by high consumption of magnesium powder.

[0006] The technical idea of ​​the present invention is to increase the pre-injection lime powder desulfurization mode, and under the condition of high alkalinity of molten iron slag, take advantage of the characteristics of lime powder with large specific surface area and strong desulfurization ability, and increase the amount of lime powder in the pre-injection stage to give full play to the desulfurization ability of lime powder when the sulfur mass percentage of molten iron is high, and reduce the sulfur mass percentage of molten iron before spraying magnesium powder, thereby reducing the consumption of magnesium powder. According to the influence of the pre-injection lime powder desulfurization mode on the amount of magnesium powder, the temperature drop of molten iron, and the life of the spray gun, the benefit calculation method of lime powder desulfurization is determined, and the pre-injection lime powder desulfurization mode is adopted under the premise of meeting the positive benefit, high molten iron temperature, and high molten iron silicon mass percentage. Combined with the amount of lime powder in the pre-injection stage and whether the molten iron ladle uses the ladle casting surplus, the amount of magnesium powder is corrected, and finally the cost of molten iron desulfurization is reduced.

[0007] The technical solution adopted by the present invention is a high-efficiency composite injection molten iron desulfurization method, comprising the following steps:

[0008] 1) Collect the parameters of the hot metal pouring tank. After the hot metal ladle enters the desulfurization station, collect the hot metal mass m of the current furnace pouring tank 铁 , pouring pot molten iron temperature T0, pouring pot molten iron sulfur mass percentage w[S] 倒罐 and the mass percentage of silicon in hot metal in the pouring tank w[Si] 倒罐 ;

[0009] 2) Perform pre-injection, the spraying powder is lime powder, insert the top spray gun into the molten iron in the ladle, spray the lime powder, and determine the pre-injection parameters before spraying the lime powder, including the amount of lime powder in the pre-injection stage m 石,1 ; Lime powder injection rate v 石,1 ; The ratio of powder to nitrogen per unit time in the pre-injection stage ε1; The default lime powder desulfurization mode is adopted, and the amount of lime powder in the pre-injection stage is preset according to historical data m 石,0 , m 石,0 The purpose is to promote the reaction of lime powder with sulfur in molten iron, so that the desulfurization products can be stably present in the molten iron slag. The benefit EP of the lime powder desulfurization mode is calculated according to formulas 1 to 4.

[0010] EP=Δm 镁，0 ×(p 镁 +k×p 石 )-m 石,0 ×p 石 -ΔT×p T -ΔC 枪 Formula 1;

[0011]

[0012]

[0013]

[0014] In formulas 1 to 4, EP is the benefit of lime powder desulfurization mode, in units of RMB / ton iron; Δm 镁,0 is the amount of magnesium powder that can be reduced in the lime powder desulfurization mode, in kg / ton iron; p 镁 is the price of magnesium powder, in yuan / kg; p 石 is the price of lime powder, in yuan / kg; k is the ratio of lime powder consumption to magnesium powder consumption per unit time in the composite injection stage; m 石,0 is the preset amount of lime powder in the pre-injection stage, in kg / ton iron; ΔT is the temperature drop of molten iron increased by lime powder desulfurization mode, in °C; p T The cost of raising the temperature of molten iron by 1°C, in yuan / ton of iron; ΔC 枪 is the cost change of desulfurization spray gun, in Yuan / ton iron;

[0015] w[CaO] 石 w[Mg] is the mass percentage of CaO in lime powder; 镁 is the mass percentage of magnesium in magnesium powder; η 石 is the lime powder recovery rate; η 镁 is the magnesium powder recovery rate; T0 is the pouring temperature of the molten iron, in °C; c 铁 is the specific heat of molten iron, in J / (kg·℃); c 石 is the specific heat of lime, in J / (kg·℃); m 铁 v is the quality of the hot metal poured from the current furnace; 石,1 is the lime powder injection rate in the pre-injection stage, in kg / min; r is the temperature drop rate of molten iron during the injection process, in °C / min; p 枪 is the price of the spray gun, in yuan / piece; A is the life of the spray gun, in min; is the average injection time per furnace, in min; The average weight of molten iron in each furnace, in tons;

[0016] When EP>0 and T0≥1260℃ and w[Si] 倒罐 ≥0.2%, lime powder desulfurization mode is adopted to reduce m 石,0 Assign to m 石,1 , that is, m 石,1 1.2~2.3kg / ton iron; lime powder injection rate v in the pre-injection stage 石,1 The ratio of powder to nitrogen per unit time in the pre-injection stage is 50-80 kg / min; the ratio of powder to nitrogen per unit time is 65-80 kg / Nm 3 ;

[0017] When EP≤0 or T0<1260℃ or w[Si] 倒罐<0.2%, lime powder without desulfurization mode is adopted, m 石,1 0.2~0.3kg / ton iron; lime powder injection rate v in the pre-injection stage 石,1 The ratio of powder to nitrogen per unit time in the pre-injection stage is 30-40 kg / min; the ratio of powder to nitrogen per unit time is 40-57 kg / Nm 3 ;

[0018] 3) Perform composite spraying, the spraying powder is lime powder and magnesium powder. After the pre-spraying is completed, the lime powder and magnesium powder are sprayed into the molten iron in the ladle at the same time. Before spraying the lime powder and magnesium powder, the composite spraying parameters are determined, including the amount of magnesium powder m 镁 ; Magnesium powder injection rate v 镁 ; The ratio of lime powder to magnesium powder per unit time k; The ratio of powder to nitrogen per unit time ε2; The amount of magnesium powder in the composite injection stage m 镁 According to formula 5,

[0019] m 镁 =m 镁,0 -Δm 镁，1 Formula 5;

[0020] In formula 5, m 镁 is the amount of magnesium powder used in the composite injection stage, in kg / ton iron; m 镁,0 is the amount of magnesium powder used in conventional processes, in kg / ton iron; Δm 镁,1 It is the correction parameter of magnesium powder dosage, the unit is kg / ton iron;

[0021] The amount of lime powder used in the current injection stage m 石,1 =1.2~2.3kg / ton iron, Δm 镁,1 Calculated by formula 6,

[0022]

[0023] The amount of lime powder used in the current injection stage m 石,1 =0.2~0.3kg / ton iron, Δm 镁,1 =0;

[0024] Magnesium powder injection rate v in the composite injection stage 镁 The ratio of lime powder to magnesium powder per unit time in the composite injection stage is 3.0 to 3.5; the ratio of powder to nitrogen per unit time in the composite injection stage is 65 to 85 kg / Nm 3 ;

[0025] 4) Post-injection, the spraying powder is lime powder, the amount of lime powder used in the post-injection stage is m 石,3 0.3~0.5kg / ton iron; lime powder injection rate v in the post-injection stage石,3 The ratio of powder to nitrogen per unit time in the post-injection stage is 30-60 kg / Nm 3 ;

[0026] 5) After the post-spraying is completed, lift the spray gun.

[0027] Further, in step 2) of the present invention, the lime powder yield η 石 According to formula 7, η 石 =3.02+4.092×m 石,0 -3.482×(m 石,0 -1.55) 2 Formula seven.

[0028] Further, in step 2) of the present invention, the magnesium powder yield η 镁 The best value is 65% to 75%, which can better reflect the desulfurization ability of magnesium powder when the sulfur content of molten iron is high.

[0029] Further, in step 3) of the present invention, when the molten iron in the ladle is added with the molten steel from the ladle, the amount of magnesium powder used in the composite blowing stage is m 镁 According to formula 8,

[0030] m 镁 =m 镁,0 -Δm 镁，1 -Δm 镁，2 Formula 8;

[0031] In formula 8, Δm 镁，2 It is the amount of magnesium powder reduced after adding the remaining molten steel from the ladle to the molten iron in the ladle, and the unit is kg / ton iron. When the molten steel is treated in the LF ladle refining furnace, Δm 镁，2 =0.1~0.12kg / ton iron; when LF ladle refining furnace is not used to treat molten steel, Δm 镁，2 =0.05~0.07kg / ton iron.

[0032] The selection basis of the process parameters of the method of the present invention is:

[0033] 1. In step 2), when lime powder desulfurization mode is used in the pre-injection stage, m 石,1It is 1.2-2.3 kg / ton of iron because the chemical reaction formula of lime powder and sulfur is 2CaO+2[S]+[Si]=2(CaS)+(SiO2). The alkalinity of molten iron slag affects the desulfurization reaction of lime powder. When the alkalinity of molten iron slag is low, the sulfur capacity of molten iron slag is low, the ability to dissolve CaS is weak and the activity of SiO2 is high, which is not conducive to the desulfurization reaction. Normally, the basicity of molten iron slag is 0.8-1.0. The lime powder sprayed at the beginning is mainly used to increase the basicity of molten iron slag to increase the sulfur capacity, and it reacts very little with the sulfur in the molten iron. As the lime powder is sprayed, the basicity of the molten iron slag gradually increases, and the lime powder begins to react more with the sulfur in the molten iron, and the utilization rate of the lime powder gradually increases. However, when the mass percentage of sulfur in the molten iron is reduced to a certain level, the desulfurization reaction rate of the lime powder will decrease due to the influence of the sulfur mass transfer rate in the molten iron. If the amount of lime powder sprayed continues to increase, the utilization rate of the lime powder will show a downward trend. At the same time, it will significantly increase the molten iron desulfurization cycle, reduce steelmaking capacity, and increase the temperature drop of the molten iron during the desulfurization process. Therefore, the amount of lime powder cannot be too low, otherwise the effect of reducing the desulfurization cost cannot be achieved. The amount of lime powder cannot be too high, otherwise it will affect the converter production and converter heat.

[0034] 2. In step 2), when the temperature of the hot metal in the pouring tank T0 is less than 1260°C, the lime powder non-desulfurization mode is adopted because, when T0 is low, the temperature of the hot metal entering the converter will be lower after the lime powder desulfurization mode is adopted, which greatly increases the possibility of insufficient heat in the converter. The converter blowing process needs to add a heating agent to supplement heat, which increases the cost. When the silicon mass percentage w[Si] of the hot metal in the pouring tank is 倒罐 When the content of w[Si] is less than 0.2%, the lime powder non-desulfurization mode is adopted because, according to the chemical reaction formula of lime powder desulfurization 2CaO+2[S]+[Si]=2(CaS)+(SiO2), when w[Si] 倒罐 When it is too low, it is not conducive to the desulfurization reaction of lime powder. After a large number of experiments, it was found that w[Si] 倒罐 When the percentage is less than 0.2%, the desulfurization effect of lime powder is not obvious.

[0035] 3. In step 2), the optimal magnesium powder yield η when calculating the lime powder desulfurization benefit 镁 The rate of magnesium powder recovery is 65-75%, which is obtained based on a large amount of historical data. 镁 This is because the sulfur removed by lime powder is in the range where the sulfur content of molten iron is relatively high. In this range, the reaction ability of magnesium powder with sulfur is relatively strong, and the utilization rate of magnesium powder desulfurization is relatively high.

[0036] 4. In step 2), a higher lime powder injection speed should be used as much as possible in the pre-injection stage to shorten the injection time and reduce the temperature drop of the molten iron; under the condition of a higher lime powder injection speed, maintain an appropriate powder-gas ratio, while avoiding splashing, increase the lime powder penetration ratio, gas-powder two-phase flow rate, stirring, enhance the stirring of the molten iron, and promote the desulfurization reaction.

[0037] 5. In step 3), the amount of magnesium powder used in the composite injection stage is m 镁 The calculation takes into account the effect of adding ladle casting residue molten steel into the molten iron in the ladle on the amount of magnesium powder. This is because the ladle casting residue contains a large amount of ladle slag with high basicity and high sulfur capacity. During the process of pouring the pot and turning the iron, the ladle slag and the molten iron are well mixed and can play a certain desulfurization role. The average desulfurization amount is 0.002-0.005%. Therefore, the amount of magnesium powder can be reduced. The reduction amount is determined according to the molten steel refining method. When the molten steel is treated by the LF ladle refining furnace, since the LF ladle refining furnace can desulfurize the molten steel, the amount of magnesium powder can be adjusted according to the upper limit of the fluctuation of the desulfurization amount of the ladle casting residue slag.

[0038] Compared with the prior art, the present invention has the following positive effects: 1. The method of the present invention adopts a lime powder desulfurization mode in the pre-injection stage, and utilizes the characteristics of lime powder with large specific surface area and strong desulfurization ability. On the premise that the molten iron desulfurization cycle and the molten iron temperature drop meet the requirements, the amount of lime powder in the pre-injection stage is greatly increased compared with the conventional process. At the same time, with a higher lime powder injection rate, the desulfurization ability of the lime powder can be fully utilized when the sulfur mass percentage of the molten iron is high, the desulfurization utilization rate of the lime powder is improved, and the sulfur mass percentage of the molten iron before the injection of magnesium powder is reduced. 2. The method of the present invention determines the benefit calculation method of the lime powder desulfurization mode in the front-injection stage according to the positive and negative effects of the lime powder desulfurization mode. The calculation method takes into account the influence of the lime powder desulfurization mode on the amount of magnesium powder, the temperature drop of molten iron, and the life of the spray gun. The influencing factors are considered comprehensively, and the calculation results are more reasonable; according to the benefits of the lime powder desulfurization mode, the temperature of molten iron, and the mass percentage of silicon in the molten iron, it is determined whether to adopt the front-injection lime powder desulfurization mode, and the front-injection mode with the best cost is selected according to the change of magnesium powder price; the present invention combines the amount of lime powder used in the front injection and whether the molten iron ladle uses the ladle casting surplus, thereby reducing the consumption of magnesium powder and realizing efficient and low-cost molten iron desulfurization. 3. The method of the present invention solves the technical problem of high molten iron desulfurization cost caused by excessive magnesium powder consumption, and reduces the influence of the rising magnesium powder price on the molten iron desulfurization cost. DETAILED DESCRIPTION

[0039] The present invention is further illustrated below in conjunction with Examples 1 to 6, as shown in Tables 1 to 4.

[0040] The pre-injection stage of Examples 1 to 3 of the present invention adopts a lime powder desulfurization mode, and the pre-injection stage of Examples 4 to 6 adopts a conventional lime powder non-desulphurization mode.

[0041] The nominal capacity of the ladle used to hold molten iron in the embodiment of the present invention is 150 tons, and the price of lime powder is p 石 0.75 yuan / kg, the mass percentage of CaO in lime powder is w[CaO] 石 The magnesium content in magnesium powder is 97%, w[Mg] 镁 90%, the specific heat of molten iron c 铁 is 0.837 J / (kg·℃), the specific heat of lime c 石 is 1J / (kg·℃), the price of the spray gun is p 枪 2500 yuan / piece, the life of the spray gun A is 750 minutes, and the average spraying time per furnace is 15.5min, average weight of molten iron poured from each furnace The ratio of lime powder consumption to magnesium powder consumption per unit time in the composite injection stage is k3, and the magnesium powder injection rate is v 镁 The ratio of powder to nitrogen blowing per unit time is 65 kg / Nm 3 ; Lime powder dosage in the post-injection stage m 石,3 The lime powder injection rate is 0.42 kg / ton iron, v 石,3 The ratio of powder to nitrogen blowing per unit time is 33kg / Nm 3 The parameters of hot metal pouring, the benefit calculation parameters in the lime powder desulfurization mode in the front injection stage, the benefits in the lime powder desulfurization mode in the front injection stage and the parameters of lime powder dosage in the front injection stage, and the process parameters and effects of composite injection hot metal desulfurization are shown in Tables 1 to 4.

[0042] Table 1 Parameters of hot metal pouring in the embodiment of the present invention

[0043] category <![CDATA[m 铁 ,t]]> <![CDATA[T0,℃]]> <![CDATA[w[S] 倒罐 ,%]]> <![CDATA[w[Si] 倒罐 ,%]]> Example 1 150 1368 0.0579 0.410 Example 2 151 1362 0.0556 0.352 Example 3 110 1378 0.0364 0.0344 Example 4 143 1359 0.0202 0.417 Example 5 148 1345 0.0339 0.321 Example 6 149 1255 0.0651 0.0216

[0044] Table 2 Benefit calculation parameters in lime powder desulfurization mode in the front injection stage of the embodiment of the present invention

[0045]

[0046] Table 3 Benefits of lime powder desulfurization mode in the front injection stage of the embodiment of the present invention and parameters of the amount of lime powder injected before

[0047]

[0048] Note: In the table, "A" indicates that molten steel is treated by argon blowing from the bottom of the ladle furnace; "L" indicates that molten steel is refined by using an LF ladle refining furnace.

[0049] Table 4 Process parameters and effects of composite injection hot metal desulfurization in the embodiment of the present invention

[0050]

[0051]

[0052] As shown in the above table, the main difference between Example 1 and Example 4 is the different prices of magnesium powder: the price of magnesium powder in Example 1 is 30 yuan / kg, and the lime powder desulfurization mode is adopted. The magnesium powder reduces 0.073kg / ton of iron, and the benefit is 0.577 yuan / ton of iron; when the price of magnesium powder in Example 4 is 21 yuan / kg, the benefit EP calculation result under the lime powder desulfurization mode is negative, so the lime powder desulfurization mode is not adopted.

[0053] The main differences between Examples 2, 3, 5, and 6 are: the price of magnesium powder in Example 2 is 30 yuan / kg, and the lime powder desulfurization mode is adopted. The magnesium powder reduces 0.139 kg / ton of iron, and the benefit is 1.805 yuan / ton of iron; the price of magnesium powder in Example 5 is 16.8 yuan / kg, and the lime powder desulfurization mode is ineffective, so the original conventional process is adopted; the price of magnesium powder in Example 3 is 30 yuan / kg, and the lime powder desulfurization mode is adopted. The molten iron ladle uses the ladle casting residue and the refining path does not include the LF furnace. The magnesium powder reduces 0.2 kg / ton of iron, and the benefit is 3.611 yuan / ton of iron; the price of magnesium powder in Example 6 is 30 yuan / kg. Although the benefit EP calculation result under the lime powder desulfurization mode is 1.862 yuan / ton of iron, since the molten iron temperature is lower than 1260°C, the lime powder desulfurization mode is not adopted.

[0054] It can be seen from Examples 1 to 6 that the critical price of magnesium powder in the pre-injection lime powder desulfurization mode decreases with the increase of lime powder dosage, and the benefit increases with the increase of lime powder dosage.

[0055] When the efficiency of the lime powder desulfurization mode, the temperature of the molten iron in the pouring tank, and the mass percentage of silicon in the molten iron in the pouring tank meet the conditions, the use of the lime powder desulfurization mode in the front injection stage can reduce the desulfurization cost.

[0056] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A high-efficiency composite injection hot metal desulfurization method, characterized in that: The method comprises the following steps: 1) Collect the parameters of the hot metal pouring tank. After the hot metal ladle enters the desulfurization station, collect the hot metal mass m of the current furnace pouring tank 铁 , pouring pot molten iron temperature T0, pouring pot molten iron sulfur mass percentage w[S] 倒罐 and the mass percentage of silicon in the hot metal in the pouring tank w[Si] 倒罐 ; 2) Perform pre-injection, the spraying powder is lime powder, insert the top spray gun into the molten iron in the ladle, spray the lime powder, and determine the pre-injection parameters before spraying the lime powder, including the amount of lime powder in the pre-injection stage m 石,1 ; Lime powder injection rate v 石,1 ; The ratio of powder to nitrogen per unit time in the pre-injection stage ε1; The default lime powder desulfurization mode is adopted, and the amount of lime powder in the pre-injection stage is preset according to historical data m 石,0 , m 石,0 The efficiency EP of lime powder desulfurization mode is 1.2-2.3 kg / ton iron. According to formulas 1-4, the efficiency EP of lime powder desulfurization mode is calculated. EP=Δm 镁，0 ×(p 镁 +k×p 石 )-m 石,0 ×p 石 -ΔT×p T -ΔC 枪 Formula 1; In formulas 1 to 4, EP is the benefit of lime powder desulfurization mode, in units of RMB / ton iron; Δm 镁,0 is the amount of magnesium powder that can be reduced in the lime powder desulfurization mode, in kg / ton iron; p 镁 is the price of magnesium powder, in yuan / kg; p 石 is the price of lime powder, in yuan / kg; k is the ratio of lime powder consumption to magnesium powder consumption per unit time in the composite injection stage; m 石,0 is the preset amount of lime powder in the pre-injection stage, in kg / ton iron; ΔT is the temperature drop of molten iron increased by lime powder desulfurization mode, in °C; p T The cost of raising the temperature of molten iron by 1°C, in yuan / ton of iron; ΔC 枪 is the cost change of desulfurization spray gun, in Yuan / ton iron; w[CaO] 石 w[Mg] is the mass percentage of CaO in lime powder; 镁 is the mass percentage of magnesium in magnesium powder; η 石 is the lime powder recovery rate; η 镁 is the magnesium powder recovery rate; T0 is the pouring temperature of the molten iron, in °C; c 铁 is the specific heat of molten iron, in J / (kg·℃); c 石 is the specific heat of lime, in J / (kg·℃); m 铁 v is the quality of the hot metal poured from the current furnace; 石,1 is the lime powder injection rate in the pre-injection stage, in kg / min; r is the temperature drop rate of molten iron during the injection process, in °C / min; p 枪 is the price of the spray gun, in yuan / piece; A is the life of the spray gun, in min; is the average injection time per furnace, in min; The average weight of molten iron in each furnace, in tons; When EP>0 and T0≥1260℃ and w[Si] 倒罐 ≥0.2%, lime powder desulfurization mode is adopted, m 石,1 1.2~2.3kg / ton iron; lime powder injection rate v in the pre-injection stage 石,1 The ratio of powder to nitrogen per unit time in the pre-injection stage is 50-80 kg / min; the ratio of powder to nitrogen per unit time is 65-80 kg / Nm 3 ; When EP≤0 or T0<1260℃ or w[Si] 倒罐 <0.2%, lime powder without desulfurization mode is adopted, m 石,1 0.2~0.3kg / ton iron; lime powder injection rate v in the pre-injection stage 石,1 The ratio of powder to nitrogen per unit time in the pre-injection stage is 30-40 kg / min; the ratio of powder to nitrogen per unit time is 40-57 kg / Nm 3 ; 3) Perform composite spraying, the spraying powder is lime powder and magnesium powder. After the pre-spraying is completed, the lime powder and magnesium powder are sprayed into the molten iron in the ladle at the same time. Before spraying the lime powder and magnesium powder, the composite spraying parameters are determined, including the amount of magnesium powder m 镁 ; Magnesium powder injection rate v 镁 ; The ratio of lime powder to magnesium powder per unit time k; The ratio of powder to nitrogen per unit time ε2; The amount of magnesium powder in the composite injection stage m 镁 According to formula 5, m 镁 =m 镁,0 -Δm 镁，1 Formula 5; In formula 5, m 镁 is the amount of magnesium powder used in the composite injection stage, in kg / ton iron; m 镁,0 is the amount of magnesium powder used in conventional processes, in kg / ton iron; Δm 镁,1 It is the correction parameter of magnesium powder dosage, the unit is kg / ton iron; The amount of lime powder used in the current injection stage m 石,1 =1.2~2.3kg / ton iron, Δm 镁,1 Calculated by formula 6, The amount of lime powder used in the current injection stage m 石,1 =0.2~0.3kg / ton iron, Δm 镁,1 =0; Magnesium powder injection rate v in the composite injection stage 镁 The ratio of lime powder to magnesium powder per unit time in the composite injection stage is 3.0 to 3.5; the ratio of powder to nitrogen per unit time in the composite injection stage is 65 to 85 kg / Nm 3 ; 4) Post-injection, the spraying powder is lime powder, the amount of lime powder used in the post-injection stage is m 石,3 0.3~0.5kg / ton iron; lime powder injection rate v in the post-injection stage 石,3 The ratio of powder to nitrogen per unit time in the post-injection stage is 30-60 kg / Nm 3 ; 5) After the post-spraying is completed, lift the spray gun.

2. The high-efficiency composite hot metal desulfurization method according to claim 1, characterized in that: In step 2), the lime powder yield η 石 According to formula 7, η 石 =3.02+4.092×m 石,0 -3.482×(m 石,0 -1.55) 2 Formula seven.

3. The high-efficiency composite hot metal desulfurization method according to claim 1, characterized in that: In step 2), the magnesium powder yield η 镁 It is 65% to 75%.

4. The high-efficiency composite hot metal desulfurization method according to claim 1, characterized in that: In step 3), when the molten iron in the ladle is added with the remaining molten steel from the ladle, the amount of magnesium powder used in the composite injection stage is m 镁 According to formula 8, m 镁 =m 镁,0 -Δm 镁，1 -Δm 镁，2 Formula 8; In formula 8, Δm 镁，2 It is the amount of magnesium powder reduced after adding the remaining molten steel from the ladle to the molten iron in the ladle, and the unit is kg / ton iron. When the molten steel is treated in the LF ladle refining furnace, Δm 镁，2 =0.1~0.12kg / ton iron; when LF ladle refining furnace is not used to treat molten steel, Δm 镁，2 =0.05~0.07kg / ton iron.

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