Method for smelting low-phosphorus steel from molten iron

Abstract

The invention discloses a method for smelting low-phosphorus steel from molten iron, and relates to the technical field of converter steelmaking, and the method comprises the following steps: carrying out slag splashing furnace protection treatment on a converter; molten iron and scrap steel in a preset proportion are loaded into the converter subjected to slag splashing furnace protection treatment; oxygen supply blowing and slagging treatment are conducted on the converter based on a first lance position mode, and in the first lance position mode, the lance position of an oxygen lance is increased along with increasing of the blowing duration; when the blowing flow reaches a preset flow threshold value, oxygen supply is stopped, and deslagging treatment is conducted on the converter; oxygen supply blowing is conducted on the converter on the basis of a second lance position mode, and in the second lance position mode, the lance position of the oxygen lance is firstly increased and then decreased along with increasing of the blowing duration; and when the blowing is performed to a preset final temperature, tapping is ended. Different lance position modes are used for two times of blowing, so that the dephosphorization reaction in the early stage is fully carried out, the oxidability and the slag system flowability are accurately regulated and controlled after deslagging, and the dephosphorization efficiency is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of converter steelmaking, and in particular to a method for smelting low-phosphorus steel from molten iron. BACKGROUND

[0002] With the development of science and technology, the performance and quality requirements of steel in some fields are becoming higher and higher. Phosphorus is a key control element in steel and has a great influence on the toughness of steel, which can seriously affect the low-temperature toughness, welding performance and the like of steel. Therefore, phosphorus is a harmful element in steel, and with the requirements of steel enterprises for quality and the like, the phosphorus content in steel is becoming lower and lower. In order to meet the requirements of customers, steel enterprises develop low-phosphorus or ultra-low-phosphorus and other high-quality steel grades. In the process of converter steelmaking, dephosphorization is one of the key tasks.

[0003] The traditional converter dephosphorization process mainly relies on high-alkalinity, high-oxidizing and low-temperature slag conditions. High-alkalinity slag can provide sufficient free CaO to combine with P2O5 to generate stable calcium phosphate (3CaO·P2O5 or 4CaO·P2O5), thereby realizing dephosphorization.

[0004] However, this high-alkalinity dephosphorization operation requires the addition of a large amount of lime, which increases the raw material cost, and the addition of a large amount of lime leads to a significant increase in the amount of slag produced, an increase in iron loss, a decrease in molten steel yield and poor dephosphorization effect. SUMMARY

[0005] The present application provides a method for smelting low-phosphorus steel from molten iron to solve the problems of decreased molten steel yield and poor dephosphorization effect in the prior art.

[0006] In a first aspect, the present application provides a method for smelting low-phosphorus steel from molten iron, comprising: performing slag splashing and furnace protection treatment on a converter; loading molten iron and scrap steel in a preset proportion into the converter after the slag splashing and furnace protection treatment; performing oxygen blowing and slagging treatment on the converter based on a first gun position mode; wherein in the first gun position mode, the gun position of the oxygen lance increases with the increase of the blowing time; and the slagging treatment process uses lime and sinter; stopping oxygen supply when the blowing flow rate reaches a preset flow rate threshold, and performing slag tapping treatment on the converter; performing oxygen blowing on the converter based on a second gun position mode; wherein in the second gun position mode, the gun position of the oxygen lance increases first and then decreases with the increase of the blowing time; ending the tapping when the blowing reaches a preset end point temperature.

[0007] In some feasible embodiments, the preset proportion comprises: The proportion of molten iron is 90-95% of the total charge, and the proportion of scrap steel is 0-10% of the total charge. The silicon content in the molten iron is 0.25-0.65%, and the temperature of the molten iron is greater than or equal to 1250°C.

[0008] In some feasible embodiments, the oxygen blowing based on the first gun position mode is performed on the converter, comprising: In the first time period, oxygen blowing is performed on the converter based on the first gun position; In the second time period, oxygen blowing is performed on the converter based on the second gun position, which is higher than the first gun position; In the third time period, oxygen blowing is performed on the converter based on the third gun position, which is higher than the second gun position.

[0009] In some feasible embodiments, the oxygen blowing intensity is set to 2.70-2.85 Nm³ / (t·min); The first time period is 0-3 min, and the first gun position is 1600-1650 mm; The second time period is 3-5 min, and the second gun position is 1700-1750 mm; The third time period is after 5 min, and the third gun position is 1800-1850 mm; The preset flow threshold is 3700-3800 Nm³.

[0010] In some feasible embodiments, the slag making process comprises: When the oxygen blowing time reaches 1 min, the preset amount of lime and the initial amount of sinter are added; the initial amount is 50-60% of the preset sinter amount; Within 2-6.5 min of oxygen blowing, the remaining sinter is added in batches; each batch is 3.0-5.5 kg / t.

[0011] In some feasible embodiments, the preset lime amount comprises:

[0012] Wherein, R is the binary basicity, and the value is 2.0-2.2; %Si is the silicon content in the molten iron; t is the tapping amount.

[0013] In some feasible embodiments, the preset sinter amount comprises:

[0014] Wherein, T is the temperature of molten iron, %Si is the silicon content of molten iron, G is the amount of scrap steel added, and t is the amount of steel tapped.

[0015] In some feasible embodiments, the oxygen supply blowing of the converter based on the second lance position mode includes: During the fourth time period, oxygen blowing is performed on the converter based on the fourth gun position; During the fifth time period, oxygen blowing is performed on the converter based on the fifth gun position, which is higher than the fourth gun position. During the sixth time period, oxygen blowing is performed on the converter based on the sixth gun position, which is lower than the fourth gun position.

[0016] In some feasible embodiments, the fourth time period is 0 to 1 minute, and the fourth gun position is 1550 to 1650 mm. The fifth time period is from 1 minute to 1 minute before the end point, and the fifth gun position is 1750-1850mm. The sixth time period is 1 minute before the end point, and the sixth gun position is 1150-1250mm. The preset endpoint temperature is 1610–1635°C.

[0017] In some feasible embodiments, the oxygen supply and blowing of the converter based on the second gun position mode further includes: When the oxygen blowing time reaches 1 minute, add 19.0-23.0 kg / t of lime, 7.0-10.0 kg / t of dolomite, and 2.3-3.8 kg / t of iron-vanadium clay.

[0018] Compared with existing technologies, the beneficial effects of this application are as follows: The process of smelting low-phosphorus steel from molten iron includes oxygen blowing, slag removal, and post-slag removal blowing. Different lance positions are used in the two blowing processes, which not only ensures the full progress of the dephosphorization reaction in the early stage, but also precisely controls the oxidizing properties and slag fluidity after slag removal. Through segmented lance position-feeding-oxygen supply synergistic optimization, the dephosphorization efficiency is significantly improved. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of a method for smelting low-phosphorus steel from molten iron, provided as an embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of some embodiments of this application clearer, the technical solutions of some embodiments of this application will be clearly and completely described below with reference to specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0021] It should be noted that the brief descriptions of terms in some embodiments of this application are only for the convenience of understanding the implementation methods described below, and are not intended to limit the implementation methods of some embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0022] The terms "first," "second," "third," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar or related objects or entities and do not necessarily imply a specific order or sequence, unless otherwise indicated. It should be understood that such terms can be used interchangeably where appropriate, for example, to implement embodiments in a sequence other than those given in the illustrations or description of this application.

[0023] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclusively include, for example, a product or device that includes a series of components is not necessarily limited to those that are explicitly listed, but may include other components that are not explicitly listed or that are inherent to such product or device.

[0024] Dephosphorization is a critical task in converter steelmaking. Traditional converter dephosphorization processes mainly rely on slag conditions characterized by high basicity, high oxidizing power, and low temperature. High basicity slag provides sufficient free CaO to combine with P2O5 to form stable calcium phosphate (3CaO·P2O5 or 4CaO·P2O5), thus achieving dephosphorization. However, this high basicity dephosphorization operation requires the addition of large amounts of lime, increasing raw material costs. Furthermore, the addition of large amounts of lime leads to a significant increase in slag production, increased iron loss, decreased steel yield, and poor dephosphorization efficiency.

[0025] To address the aforementioned problems, this application provides a method for smelting low-phosphorus steel from molten iron. Figure 1 This illustration shows a schematic flow diagram of a method for smelting low-phosphorus steel from molten iron, according to an embodiment of this application. Figure 1 As shown, the method for smelting low-phosphorus steel with molten iron provided in this application may include the following steps: S1. Perform slag splashing protection treatment on the converter; S2. Load the molten iron and scrap steel in a preset ratio into the converter after the slag splashing and furnace protection treatment; S3. The converter is subjected to oxygen blowing and slag formation based on the first lance position mode; wherein, in the first lance position mode, the lance position of the oxygen lance increases with the increase of blowing time; the slag formation process uses lime and sinter. S4. When the blowing flow rate reaches the preset flow rate threshold, stop the oxygen supply and perform slag removal treatment on the converter. S5. The converter is subjected to oxygen blowing based on the second lance position mode, wherein, in the second lance position mode, the lance position of the oxygen lance first increases and then decreases as the blowing time increases; S6. Stop tapping the steel when the blowing reaches the preset endpoint temperature.

[0026] The following section uses a 120t top-and-bottom blown converter as an example to further illustrate the steps involved in smelting low-phosphorus steel.

[0027] In some embodiments, after the previous heat of steel is tapped from the converter, the converter undergoes slag splashing for furnace protection. Slag splashing for furnace protection refers to a smelting technique that utilizes the magnesium oxide-containing final slag from steelmaking, sprayed with high-pressure nitrogen to form a high-melting-point protective layer, thereby extending the life of the furnace lining. This protective layer effectively reduces refractory material loss by inhibiting oxidation and decarburization of the furnace lining brick surface and mitigating the erosive effect of high-temperature molten slag.

[0028] After the slag splashing protection treatment of the converter is completed, all the slag is poured out to ensure that the furnace lining is stable and there is no residual high-phosphorus slag in the furnace, so as to carry out the subsequent smelting process.

[0029] In some embodiments, after the slag is poured out, a charging process is performed, in which raw materials for smelting are added to the converter. The raw materials may include molten iron and scrap steel. The charging ratio of molten iron and scrap steel is preset and can be set according to the total charging amount.

[0030] The proportion of molten iron is 90-95% of the total charge, and the proportion of scrap steel is 0-10% of the total charge. In this embodiment, the material proportion can be by weight, that is, the weight of molten iron accounts for 90-95% of the total charge, and the weight of scrap steel accounts for 0-10%. The total charge can be the standard charge of the converter.

[0031] The silicon content in the molten iron is 0.25-0.65%, and the temperature of the molten iron is greater than or equal to 1250℃.

[0032] Table 1 shows data on molten iron and scrap steel in some examples.

[0033] Table 1

[0034]

[0035] Therefore, molten iron and scrap steel in a preset ratio can be loaded into a converter after slag splashing protection treatment for smelting.

[0036] In some embodiments, after molten iron and scrap steel are charged into the converter, a smelting process can be carried out. The smelting process may include four stages: pre-process control, slag removal, post-slag removal blowing, and final control.

[0037] The initial control measures can include oxygen supply and slag formation. The oxygen supply system refers to oxygen blowing, while the slag formation system refers to slag treatment. Oxygen supply and slag formation can be started simultaneously to ensure that the initial slag forms and covers the molten metal surface within a short time during blowing.

[0038] In some embodiments, oxygen blowing and slagging can be performed on the converter based on the first lance position mode. In the first lance position mode, the position of the oxygen lance increases with the increase of blowing time.

[0039] The oxygen supply intensity during the blowing process is controlled between 2.70 and 2.85 Nm³ / (t·min).

[0040] In the first lance position mode, oxygen blowing is performed on the converter, including: During the first time period, oxygen blowing is performed on the converter based on the first gun position.

[0041] During the second time period, oxygen blowing is performed on the converter based on the second gun position, which is higher than the first gun position.

[0042] During the third time period, oxygen blowing is performed on the converter based on the third gun position, which is higher than the second gun position.

[0043] Therefore, the oxygen lance position is controlled using a "low-high-high" mode. The oxygen lance position is gradually raised, which allows for rapid formation of oxidizing properties in the early stage of blowing, promoting efficient oxidation of silicon and phosphorus; in the middle stage, it stabilizes the slag condition and inhibits re-drying; in the later stage, it lifts the lance to decarburize and enhance the phosphorus distribution ratio, so that the phosphorus content of the final molten steel is stably controlled at a low level, achieving the smelting of low-phosphorus steel.

[0044] In some embodiments, the first time period is 0 to 3 minutes, and the first gun position is 1600 to 1650 mm. The second time period is 3 to 5 minutes, and the second gun position is 1700 to 1750 mm. The third time period is after 5 minutes, and the third gun position is 1800-1850mm.

[0045] When the blowing flow rate reaches 3700-3800 Nm³, turn off the oxygen and lift the lance.

[0046] Table 2 shows the specific parameters of oxygen blowing in some embodiments.

[0047] Table 2

[0048]

[0049] In some embodiments, lime and sinter are used in the slag-forming process. The lime and sinter are added in stages according to a precise ratio to ensure that the slag basicity R is kept stable in the range of 2.0 to 2.2, taking into account both dephosphorization efficiency and slag fluidity.

[0050] The slag-making system specifically includes: When the oxygen blowing time reaches 1 minute, add lime corresponding to the preset lime weight and the initial weight of sinter. The initial weight is 50-60% of the preset sinter weight.

[0051] The amounts of lime and sinter to be added are calculated in advance. In the first batch, all the lime is added and the amount of sinter added is 50-60% of the calculated amount. During the oxygen blowing period of 2-6.5 minutes, the remaining sinter is added in batches; the amount added in each batch is between 3.0 and 5.5 kg / t.

[0052] In some embodiments, the method for calculating the preset lime weight includes:

[0053] in, R represents binary alkalinity, with a value ranging from 2.0 to 2.2; %Si represents the silicon content in molten iron, in percentages of %; t represents the amount of steel produced, in tons.

[0054] In some embodiments, the method for calculating the weight of the pre-set sinter includes:

[0055] in, T represents the temperature of the molten iron, in °C. %Si represents the silicon content of molten iron, G represents the amount of scrap steel added, and the unit is tons; t represents the amount of steel produced.

[0056] Table 3 shows the specific parameters of the slag-forming material in some embodiments.

[0057] Table 3

[0058]

[0059] The specific timing and amount of material added in Examples 1-3 are as follows: Example 1: Add 3257 kg of lime and 1650 kg of sinter for 1 min 10 s during the blowing process; add 510 kg of sinter for 3 min 30 s during the blowing process; add 535 kg of sinter for 4 min 10 s during the blowing process; add 535 kg of sinter for 5 min 15 s during the blowing process.

[0060] Example 2: Add 2746 kg of lime and 1550 kg of sinter for 1 minute of blowing; add 525 kg of sinter for 4 minutes and 26 seconds of blowing; add 550 kg of sinter for 5 minutes and 20 seconds of blowing.

[0061] Example 3: Add 4063 kg of lime and 2630 kg of sinter for 1 min 20 s during the initial blowing process; add 423 kg of sinter for 2 min 20 s during the blowing process; add 405 kg of sinter for 3 min 5 s during the blowing process; add 489 kg of sinter for 4 min 10 s during the blowing process; add 435 kg of sinter for 5 min 15 s during the blowing process; add 514 kg of sinter for 5 min 55 s during the blowing process.

[0062] In some embodiments, when the blowing flow rate reaches a preset flow threshold, oxygen supply is stopped and the converter is subjected to slag removal. The preset flow threshold is set to 3700–3800 Nm³, as shown in Table 2.

[0063] After shutting off the oxygen and lifting the lance, let the converter stand for 2-3 minutes, then pour out the slag from the furnace. The specific standing times for Examples 1-3 are 2 min 20 s, 2 min 30 s, and 2 min 35 s, respectively.

[0064] In some embodiments, a second blowing process is carried out after the slag is poured out, that is, oxygen is supplied again after the slag is poured out.

[0065] Oxygen blowing can be performed on the converter based on the second lance position mode. In the second lance position mode, the position of the oxygen lance first increases and then decreases as the blowing time increases.

[0066] The oxygen supply intensity during the blowing process is controlled between 2.70 and 2.85 Nm³ / (t·min).

[0067] Oxygen blowing in the converter based on the second lance position mode includes: During the fourth time period, oxygen blowing is performed on the converter based on the fourth gun position.

[0068] During the fifth time period, oxygen blowing is performed on the converter based on the fifth gun position, which is higher than the fourth gun position.

[0069] During the sixth time period, oxygen blowing is performed on the converter based on the sixth gun position, which is lower than the fourth gun position.

[0070] Therefore, the oxygen lance position is controlled in a "low-high-low" mode to ensure that the dephosphorization reaction proceeds fully and avoids phosphorus reversion, thereby producing ultra-low phosphorus steel.

[0071] In some embodiments, the fourth time period is 0 to 1 minute, and the fourth gun position is 1550 to 1650 mm. The fifth time period is from 1 minute to 1 minute before the end point, and the fifth gun position is 1750-1850mm. The sixth time period is 1 minute before the finish line, and the sixth gun position is 1150-1250mm.

[0072] That is, the gun position is initially set at 1550-1650mm during the second blowing process. After blowing for 1 minute, the gun position is raised to 1750-1850mm while maintaining the same oxygen supply intensity. The gun position is then lowered to 1150-1250mm 1 minute before the end of the process.

[0073] Table 4 shows the specific parameters for oxygen blowing after slag removal in some embodiments.

[0074] Table 4

[0075]

[0076] In some embodiments, during the oxygen-blowing process of the converter based on the second gun position mode, lime, dolomite and ferrovanadium clay are added. The three substances work together to construct a high-alkalinity, low-melting-point slag, which enhances the interfacial migration and fixation of phosphorus.

[0077] When the oxygen blowing time reaches 1 minute, add 19.0-23.0 kg / t of lime, 7.0-10.0 kg / t of dolomite, and 2.3-3.8 kg / t of iron vanadium clay.

[0078] Table 5 shows the specific parameters for feeding in some embodiments.

[0079] Table 5

[0080]

[0081] In some embodiments, the endpoint control process includes ending tapping when the blowing reaches a preset endpoint temperature. The preset endpoint temperature is 1610–1635°C.

[0082] Table 6 shows the specific parameters of the endpoint temperature in some embodiments.

[0083] Table 6

[0084]

[0085] Therefore, the method for smelting low-phosphorus steel with molten iron according to the embodiments of this application can control the phosphorus content of the steel to below 0.0010%, and the dephosphorization effect is strong.

[0086] As can be seen from the above technical solutions, the embodiments of this application have the following technical effects: (1) This invention achieves the goal of using high-phosphorus molten iron to stably produce low-phosphorus steel, and can stably control the phosphorus content of the steel produced from the converter to below 0.0010%, which meets the stringent requirements of high-end ultra-low phosphorus steel.

[0087] (2) Reduced slag consumption and increased metal recovery. Total lime consumption was reduced by 15% to 25% compared to traditional processes; the total slag volume was reduced, iron loss was reduced, and steel recovery was improved.

[0088] (3) Strong process stability and operability. It effectively eliminates the "re-drying" phenomenon of high-alkalinity slag, the entire blowing process is stable, and the metal splashing rate is greatly reduced; (4) Through phased precise control and mathematical modeling of material calculation, the process has good reproducibility and is easy to achieve automated control and standardized operation.

[0089] (5) The reduction in slag directly reduces the amount of solid waste emitted by steel enterprises, resulting in significant environmental benefits.

[0090] The same or similar parts among the various embodiments in this specification can be referred to mutually, and will not be repeated here.

[0091] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. It should be understood that the invention is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

[0092] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein.

Claims

1. A method for smelting low-phosphorus steel from molten iron, characterized in that, include: Slag splashing protection treatment for the converter; Molten iron and scrap steel in a predetermined ratio are loaded into the converter after slag splashing and furnace protection treatment; The converter is subjected to oxygen blowing and slag formation based on the first lance position mode; wherein, in the first lance position mode, the lance position of the oxygen lance increases with the increase of blowing time; the slag formation process uses lime and sinter. When the blowing flow rate reaches the preset flow rate threshold, the oxygen supply is stopped, and the converter is subjected to slag removal. The converter is subjected to oxygen blowing based on the second lance position mode, wherein, in the second lance position mode, the lance position of the oxygen lance first increases and then decreases as the blowing time increases; The tapping process ends when the steel is blown to the preset endpoint temperature.

2. The method for smelting low-phosphorus steel from molten iron according to claim 1, characterized in that, The preset ratio includes: The proportion of molten iron is 90-95% of the total charge, and the proportion of scrap steel is 0-10% of the total charge; The silicon content in the molten iron is 0.25-0.65%, and the temperature of the molten iron is greater than or equal to 1250℃.

3. The method for smelting low-phosphorus steel with molten iron according to claim 1, characterized in that, The oxygen supply and blowing process for the converter based on the first lance position mode includes: During the first time period, oxygen blowing is performed on the converter based on the first gun position; During the second time period, oxygen blowing is performed on the converter based on the second gun position, which is higher than the first gun position; During the third time period, oxygen blowing is performed on the converter based on the third gun position, which is higher than the second gun position.

4. The method for smelting low-phosphorus steel with molten iron according to claim 3, characterized in that, The oxygen supply intensity for oxygen blowing is set at 2.70–2.85 Nm³ / (t·min); The first time period is 0 to 3 minutes, and the first gun position is 1600 to 1650 mm. The second time period is 3 to 5 minutes, and the second gun position is 1700 to 1750 mm. The third time period is after 5 minutes, and the third gun position is 1800-1850mm. The preset flow rate threshold is 3700-3800 Nm³.

5. The method for smelting low-phosphorus steel from molten iron according to claim 4, characterized in that, The slag-making process includes: When the oxygen blowing time reaches 1 minute, lime corresponding to the preset lime weight and the initial weight of sinter are added; the initial weight is 50-60% of the preset sinter weight. During the oxygen blowing period of 2 to 6.5 minutes, the remaining sintered ore is added in batches; the amount added in each batch is between 3.0 and 5.5 kg / t.

6. The method for smelting low-phosphorus steel with molten iron according to claim 5, characterized in that, The preset lime weight includes: ； in, R represents binary alkalinity, with a value ranging from 2.0 to 2.2; %Si represents the silicon content of molten iron; t represents the amount of steel produced.

7. The method for smelting low-phosphorus steel with molten iron according to claim 6, characterized in that, The preset weight of sintered ore includes: ； in, T is the temperature of molten iron, %Si is the silicon content of molten iron, G is the amount of scrap steel added, and t is the amount of steel tapped.

8. The method for smelting low-phosphorus steel from molten iron according to claim 1, characterized in that, The oxygen supply and blowing process for the converter based on the second gun position mode includes: During the fourth time period, oxygen blowing is performed on the converter based on the fourth gun position; During the fifth time period, oxygen blowing is performed on the converter based on the fifth gun position, which is higher than the fourth gun position. During the sixth time period, oxygen blowing is performed on the converter based on the sixth gun position, which is lower than the fourth gun position.

9. The method for smelting low-phosphorus steel with molten iron according to claim 8, characterized in that, The fourth time period is 0 to 1 minute, and the fourth gun position is 1550 to 1650 mm. The fifth time period is from 1 minute to 1 minute before the end point, and the fifth gun position is 1750-1850mm. The sixth time period is 1 minute before the end point, and the sixth gun position is 1150-1250mm. The preset endpoint temperature is 1610–1635°C.

10. The method for smelting low-phosphorus steel from molten iron according to claim 9, characterized in that, The oxygen supply and blowing process for the converter based on the second gun position mode also includes: When the oxygen blowing time reaches 1 minute, add 19.0-23.0 kg / t of lime, 7.0-10.0 kg / t of dolomite, and 2.3-3.8 kg / t of iron-vanadium clay.

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