Control method for improving KR desulfurization effect

Abstract

The invention relates to a control method for improving the KR desulfurization effect. The method comprises the following steps: primarily crushing biomass, putting the crushed biomass into an iron ladle, adding iron-rich red mud, pouring refined circulating slag obtained after continuous casting into an impact mixer, uniformly spreading a layer of small-particle-size limestone on the mixed slag after impact mixing is finished, and uniformly mixing the mixed slag and the iron-rich red mud; and after covering, cracking and carbonizing the biomass, pre-melting the iron-rich red mud and decomposing the small-granularity limestone in an anoxic state. The advantages of powerful kinetic energy and potential energy generated in the process of pouring molten iron into a torpedo ladle or a molten iron trough are utilized, the mixed slag and the small-granularity limestone are further mixed and flushed evenly, and then the mixed slag and the small-granularity limestone are conveyed to a KR station to be desulfurized. According to the control method for improving the KR desulfurization effect, cracking carbonization of biomass raw materials, pre-melting of mixed slag of iron-rich red mud and refining circulating slag and decomposition of small-particle-size limestone are ingeniously utilized in the molten iron pretreatment process, the desulfurization efficiency and effect of molten iron in an iron ladle are improved, and the refining effect of ladle slag washing is improved.

Description

Technical Field

[0001] The present invention belongs to the field of comprehensive utilization of steel smelting resources, and in particular relates to a control method for improving KR desulfurization effect. Background Art

[0002] Hot metal pretreatment is a process used to remove impurities or recover valuable elements before adding the hot metal to the steelmaking furnace. Impurity element removal involves desiliconization, desulfurization, and dephosphorization (commonly known as the "three desulfurizations"), while valuable element recovery involves extracting vanadium, niobium, and tungsten from the hot metal. This "three desulfurizations" treatment offers a number of advantages for converter steelmaking. For example, it reduces the amount of lime required to remove silicon and phosphorus during the converter blowing process, reduces slag volume, and minimizes slag spillage and splashing. Furthermore, slag erosion on the furnace lining is reduced, significantly extending the life of the furnace. Furthermore, since the converter uses less slag, the blowing time can be shortened, increasing converter productivity, reducing iron losses, and improving steel quality.

[0003] Hot metal pretreatment is an essential step in optimizing the steelmaking production process and plays a crucial role in modern steelmaking. Common hot metal pretreatment methods currently include the injection method and the KR (Kambara Reactor) method. The KR method for hot metal pretreatment was developed by Nippon Steel in 1963 to limit magnesium usage and was introduced to industrial production in 1965. The KR method involves inserting a cross-shaped stirring head made of cast refractory material and baked into a ladle containing molten iron for rotational stirring, generating a vortex. Simultaneously, a weighed desulfurizer (primarily lime-based, such as lime, calcium carbide, and other powders) is added to the molten iron surface via a feeder and drawn into the vortex, allowing the calcium oxide-based desulfurizer and the molten iron to fully mix and react. This achieves desulfurization (and, optionally, desiliconization and dephosphorization). The advantages of the KR desulfurization process include: superior kinetics; the use of inexpensive desulfurizers such as CaO (the reaction equation is [CaO] + [S] = [CaS] + [O]); relatively stable desulfurization; high desulfurization efficiency, capable of reducing sulfur content to ≤ 0.005%; low desulfurizer consumption; and low metal loss. Due to its favorable metallurgical kinetics, stable results, low operating costs, and high efficiency, the KR process has been widely promoted and applied both domestically and internationally, particularly in steel mills with high requirements for and high proportions of low-sulfur steel grades. However, the KR desulfurization process has drawbacks: complex equipment, high initial investment, and a significant temperature drop in the desulfurized iron water. The current KR desulfurization performance requires further optimization and improvement.

[0004] Biomass refers to substances produced during life activities. Biomass from plants, such as herbs and woody plants, is primarily composed of cellulose, hemicellulose, and lignin. Biomass carbonization involves the carbonization of biomass, such as plants, plant waste, municipal waste, animal manure, and urban and industrial waste, to produce a carbon-rich product, biochar (also known as biochar). Like charcoal produced through thermal cracking, biochar is primarily composed of carbon molecules. Currently, biochar is primarily produced through hydrothermal conversion and pyrolysis carbonization. The cracking temperature of biochar generally ranges from 200 to 800°C, occasionally reaching temperatures as high as 1000°C. Studies have shown that increasing the cracking temperature increases the porosity and specific surface area of ​​biochar, and consequently, its carbon and ash content. Controlled pyrolysis of biomass, such as wood, grass, rice straw, rapeseed straw, corn straw, wood waste, and garden prunings, in an oxygen-deficient environment can yield biochar with exceptionally high carbon content.

[0005] Red mud is an industrial solid waste discharged during the extraction of alumina by the aluminum industry. It is called red mud because of its high iron oxide content and its resemblance to red soil. Every ton of alumina produced generates approximately 0.8-1.5 tons of red mud, and the global stockpile currently exceeds 5 billion tons. Alumina refineries typically use methods such as flat land platforms, river valley dams, and depression filling to store red mud. However, this storage method not only occupies and pollutes large amounts of land, posing serious safety hazards to the ecological environment, but also represents a waste of resources. As a major alumina producer, China is facing an urgent need to maximize the resource utilization of red mud as the stockpile grows and the pollution it causes becomes increasingly serious.

[0006] Refined slag recycling involves pouring the slag from the ladle after continuous casting into an empty ladle (or into the ladle after tapping) before tapping, rather than pouring it into the slag basin. This allows the ladle residue and refined slag to be recycled and reused, thus achieving the so-called "waste slag" recycling. Refined slag treated in the LF (Ladle Furnace) refining furnace has high basicity, low oxidizing properties, and a low melting point. Its unique composition also makes it particularly easy to pulverize. Refined slag recycling can conserve slag-making materials, increase slag formation speed, reduce electricity consumption for melting slag, and enable the recovery of excess steel after casting, further improving metal yield and reducing industrial waste emissions. Summary of the Invention

[0007] The object of the present invention is to provide a control method for improving the KR desulfurization effect. This method utilizes the cracking and carbonization of biomass raw materials, the pre-melting of the mixed slag of iron-rich red mud and refining cycle slag, and the decomposition of small-particle limestone during the molten iron pretreatment process to improve the ladle slag washing and refining effect, that is, the desulfurization efficiency and effect of the molten iron in the ladle can be improved.

[0008] In order to achieve the above-mentioned purpose of the present invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a control method for improving KR desulfurization effect, comprising the following steps:

[0010] (1) Preliminary crushing of the biomass raw materials until the length of the crushed biomass raw materials is ≤50 mm to improve the carbonization effect and efficiency;

[0011] (2) adding the preliminarily crushed biomass raw material into an iron ladle;

[0012] (3) adding 500-2000 kg of iron-rich red mud into the iron ladle;

[0013] (4) pouring the refined circulating slag at 1520° C. to 1600° C. in the ladle after continuous casting into the iron ladle, and using the kinetic energy of the circulating slag during pouring to perform mixing, so that the refined circulating slag and the biomass raw material are fully mixed to obtain mixed slag;

[0014] (5) evenly spreading small-grained limestone on the mixed slag, covering the iron ladle, and performing cracking and carbonization of the biomass raw material, pre-melting of the iron-rich red mud, and decomposition of the small-grained limestone in an oxygen-deficient environment at 600° C. to 1000° C.;

[0015] (6) removing the ladle cover and pouring molten iron at 1350° C. to 1550° C. from a torpedo tank or a molten iron ditch. Due to the weight of the molten iron and the height difference, strong kinetic energy and potential energy can be generated. The kinetic energy and potential energy of the molten iron when pouring the molten iron are used to further mix the mixed slag and the small-grained limestone to obtain a mixed material;

[0016] The weight ratio of the biomass raw material, the iron-rich red mud, the refining cycle slag, the small-grained limestone, and the molten iron is (0.8-1.2): (0.8-1.0): (5-7): (1.0-1.2): 140;

[0017] (7) The iron ladle is transferred to the KR pretreatment work station; the KR stirring head is slowly lowered into the mixture for stirring, the stirring head is inserted into the mixture to a depth of 500 to 800 mm, the rotation speed of the stirring head is 30 to 50 rpm, and the stirring time is 3 to 5 minutes, so as to promote the mixture including the mixed slag, the small-grained limestone and the molten iron to be fully mixed, thereby avoiding agglomeration and hardening that affects the function of each component;

[0018] (8) Add desulfurizer, continue to lower the KR stirring head until the insertion depth of the stirring head is 1400-1500 mm, and stir at a speed of 90-100 rpm for 10-15 minutes;

[0019] (9) Increase the speed of the stirring head to 110 rpm and continue stirring for 1 to 5 minutes to further deep desulfurization;

[0020] (10) lifting the stirring head to the waiting position to end stirring;

[0021] (11) Carry out temperature measurement, sampling, and slag removal according to process requirements; finally, wait for lifting to the converter platform.

[0022] In a specific embodiment, the biomass raw material includes one or more of wood, grass, rice straw, rape straw, corn straw, waste wood, and garden trimmings.

[0023] In one embodiment, the primary crushing is performed using a crusher.

[0024] In one embodiment, the ladle is a red-hot ladle of normal circulation.

[0025] In a specific embodiment, the iron-rich red mud is a solid waste from the Bayer process for producing alumina, and the iron-rich red mud comprises: Fe2O3 40-60wt%, SiO2 4-20wt%, Al2O3 12-20wt%, CaO 5-10wt%, Na2O 2-10wt%, TiO2 1-10wt%, and the remaining components are less than 5wt%.

[0026] In one specific embodiment, taking into account the physical properties of the iron-rich red mud, the iron-rich red mud is air-dried or baked and then bagged (1-ton bag, half-ton bag, or 20 kg small bag) for standby use, thereby facilitating the addition and manual input of the iron-rich red mud, ensuring convenient transportation, avoiding leakage during transportation, and also saving the cost of making and pressing balls when utilizing traditional red mud.

[0027] In a specific embodiment, the refined circulating slag includes: SiO2 2-12 wt%, Al2O3 22-37 wt%, CaO 35-56 wt%, and MgO 1-10 wt%.

[0028] In one embodiment, the particle size of the small-grained limestone is in the range of 5 to 15 mm.

[0029] In one embodiment, the desulfurizing agent is limestone or calcium carbide.

[0030] In one specific embodiment, the amount of desulfurizer added is calculated based on a model according to the molten iron conditions (molten iron composition, temperature, weight), combined with the added biomass raw materials (weight), iron-rich red mud (weight and composition), refining cycle slag (weight and composition), and small-particle limestone (weight).

[0031] For example, the addition amount of desulfurizer (regression analysis) formula is as follows:

[0032] Desulfurizer addition amount = -8.412 + 0.011 × T - 1.727 × Si + 68.420 × S 前 -481.320×S 后 -103.120×G 生物质原料 -87.571×G 富铁赤泥 -1.353×G 精炼循环渣 -1.620×G 小粒度石灰石

[0033] Where: T is the molten iron temperature, unit: ℃

[0034] Si is the silicon content of molten iron, unit: %

[0035] S 前 Sulfur content of molten iron before pretreatment, unit: %

[0036] S 后 Sulfur content of molten iron after pretreatment, unit: %

[0037] G 生物质原料 The weight of biomass raw materials added to this furnace (equivalent to tons of iron), unit: kg / t

[0038] G 富铁赤泥 The weight of iron-rich red mud added to this furnace (equivalent to tons of iron), unit: kg / t

[0039] G 精炼循环渣 The weight of the refining cycle slag added to this furnace (equivalent to tons of iron), unit: kg / t

[0040] G 小粒度石灰石 The weight of small-sized limestone added to this furnace (equivalent to tons of iron), unit: kg / t

[0041] The present invention performs preliminary crushing of the biomass and places it in an iron ladle, adds iron-rich red mud, pours the refined circulating slag after continuous casting into the ladle for mixing, and evenly spreads a layer of small-grained limestone on the mixed slag after mixing. After covering, the biomass is cracked and carbonized, the iron-rich red mud is pre-melted, and the small-grained limestone is decomposed under an oxygen-deficient state. Utilizing the powerful kinetic energy and potential energy generated during the process of pouring molten iron from a torpedo tank or an iron ditch, the mixed slag and small-grained limestone are further mixed and evenly mixed, and then transported to the KR station for desulfurization. Compared with the prior art, the control method for improving the KR desulfurization effect of the present invention has the following advantages:

[0042] 1. Utilizing the temperature of the refining circulating slag in the ladle and the oxygen-deficient environment with a lid to carbonize the biomass raw materials can save the carbonization cost of the biomass raw materials; realize the comprehensive and efficient utilization of the refining circulating slag, iron-rich red mud and biomass raw materials; at the same time, the carbonization environment is conducive to removing the moisture brought into the biomass raw materials, ensuring the dryness of the mixed materials and preventing moisture from being brought into the converter and affecting the quality of the molten iron.

[0043] 2. Since the biochar obtained by high-temperature cracking has a rich multi-microporous structure, it has a large specific surface area and high surface activity. Therefore, increasing the content of biochar in the slag can reduce the surface tension of the slag, and is conducive to the foaming of the slag, improving the slag fluidity, and facilitating the desulfurization reaction. In addition, since the alkaline oxides (such as K2O and CaO) contained in the biochar can react with the acidic oxides (such as SiO2) in the molten iron, it can lower the melting point and effectively improve the fluidity of the molten iron, which is conducive to metallurgical reactions such as dephosphorization and desulfurization. At the same time, the multi-microporous structure of the biochar can capture gas during the blowing process, promote the stabilization of bubbles and the formation of stable foam slag, thereby increasing the contact area of ​​the reaction interface and reducing splashing.

[0044] 3. Iron-rich red mud contains Fe2O3, CaO, Al2O3, and SiO2, while high-basicity refining cycle slag contains Fe2O3, CaO, Al2O3, MgO, and SiO2. At ladle temperatures, the mixture of iron-rich red mud and high-basicity refining cycle slag forms low-temperature calcium ferrite (SFCA) and complex calcium ferrite (SFCAM). This formation process typically involves the following: formation of CaO·Fe2O3 (1050-1150°C); reaction of Al2O3 with CaO to form calcium aluminate (1100-1150°C); melting of calcium aluminate in CaO·Fe2O3 (1100-1150°C) to form monocalcium aluminoferrite; melting of monocalcium aluminoferrite and reaction with Fe2O3 to form hemicalcium aluminoferrite (1200-1250°C); and subsequent reaction with SiO2 to form SFCA (1200-1250°C). When slag contains Mg, it forms a Mg-containing complex calcium ferrite called SFCAM. It is well known that low-melting-point SFCA and SFCAM are excellent slagging agents. Therefore, the high-basicity, low-temperature SFCA and SFCAM produced after pre-melting of the iron-rich red mud of the present invention help improve the fluidity of molten iron and the desulfurization reaction, thereby enhancing desulfurization efficiency and rate. Al2O3 in the slag also effectively promotes slagging.

[0045] 4. Small-grained limestone's primary chemical component is CaCO₃, with a decomposition temperature of approximately 896°C. At the temperature of the refining cycle slag, small-grained limestone decomposes to produce CaO and CO₂. The CaO formed by the decomposition of small-grained limestone particles added to the molten iron is actually fine, highly active lime (CaO) particles with excellent desulfurization capabilities. Therefore, it can replace lime (CaO) as a desulfurizer, reducing the consumption of small-grained lime (CaO) in the desulfurizer and lowering the raw material cost of the desulfurization process. Furthermore, the decomposed CaO provides a calcium source for composite calcium ferrite, facilitating its formation. Simultaneously, the CO₂ produced by decomposition diffuses and coats the mixed slag within the iron ladle, initially facilitating the anaerobic cracking and carbonization of the biomass feedstock. Later, it acts as a molten pool agitator, improving mass transfer conditions, facilitating slag fluidity, and accelerating desulfurization. Because CO₂ is a weakly oxidizing gas, limestone used as a desulfurizer is typically supplemented with a certain amount of carbon. The presence of biochar in the mixed slag ensures a reducing atmosphere for sulfur removal.

[0046] 5. Since the CO2 generated by the later decomposition of the low-temperature phase calcium ferrite (SFCA) and composite calcium ferrite (SFCAM), biochar, and small-particle limestone is beneficial to the fluidity of molten iron, the present invention no longer needs to use small-particle fluorite (CaF2) in the traditional desulfurizer used to improve the fluidity of molten iron, thereby avoiding the pollution of the environment by fluoride ions in fluorite, which is beneficial to environmental protection and reduces the cost of auxiliary materials.

[0047] In summary, the control method for improving the KR desulfurization effect of the present invention cleverly utilizes the cracking and carbonization of biomass raw materials, the pre-melting of the mixed slag of iron-rich red mud and refining cycle slag, and the decomposition of small-particle limestone during the molten iron pretreatment process, thereby improving the desulfurization efficiency and effect of the molten iron in the ladle and improving the refining effect of the ladle slag washing. DETAILED DESCRIPTION

[0048] Example 1:

[0049] The biomass raw materials (rice straw, rape straw, corn straw, etc. collected from a farmer) were initially crushed to a length of ≤50 mm using a crusher.

[0050] Heat 1, a 120t converter, and a red-hot ladle in normal operation. 1.1t of crushed biomass was first added to the ladle, followed by 1t of air-dried, iron-rich red mud (1 ton bag, solid waste from Bayer process alumina production, consisting of: Fe2O3 48wt%, SiO2 13wt%, Al2O3 16wt%, CaO 8wt%, Na2O 6wt%, TiO2 7wt%, with the remaining components less than 5wt%). The biomass and iron-rich red mud were spread out as much as possible.

[0051] 6t of refined circulating slag (1550℃, main components: SiO28wt%, Al2O3 28wt%, CaO 45wt%, MgO 8wt%) in the ladle after casting by the continuous casting machine is poured into the iron ladle, and the kinetic energy of the circulating slag during pouring is used to mix the refined circulating slag and the biomass raw material so that the refined circulating slag and the biomass raw material are fully mixed to obtain a mixed slag.

[0052] Then, a layer of small-grained limestone (1 t, particle size 5-15 mm) is evenly spread on the mixed slag.

[0053] The iron ladle is covered to keep it warm, and the crushed biomass raw materials undergo anoxic cracking and carbonization at the ambient temperature (880°C) inside the iron ladle. At the same time, the iron-rich red mud begins to pre-melt and the small-particle limestone undergoes high-temperature decomposition.

[0054] Before adding molten iron, the ladle lid is removed and 140 t of molten iron (temperature 1316°C, composition: ωC = 4.45%, ωSi = 0.38%, ωMn = 0.33%, ωP = 0.098%, ωS = 0.012%) is poured from the torpedo. The molten iron's own weight and height difference generate significant kinetic and potential energy, which is then used to mix the molten iron. The mixed slag and fine-grained limestone are further mixed to form a mixed material. After the molten iron is poured, the ladle is transferred to the KR pretreatment station.

[0055] According to the molten iron conditions (molten iron composition, temperature, weight), combined with the added biomass raw materials (weight), iron-rich red mud (weight and composition), refining cycle slag (weight and composition), and small-particle limestone (weight), the amount of desulfurizer added is calculated based on the model.

[0056] Regression analysis of the amount of desulfurizer added: (S 后 The target value is 0.003%)

[0057] Desulfurizer addition amount = -8.412 + 0.011 × T - 1.727 × Si + 68.420 × S 前 -481.320×S 后 -103.120×G 生物质原料 -87.571×G 富铁赤泥 -1.353×G 精炼循环渣 -1.620×G 小粒度石灰石

[0058] =-8.412+0.011×1316-1.727×0.38+68.420×0.012-481.320×0.003-103.120×1.1 / 140-87.571×1 / 140-1.353×6 / 140-1.620×1 / 140

[0059] ≈3.28kg / t iron

[0060] Slowly lower the KR stirring head for stirring. The depth of the stirring head inserted into the mixture is 500mm, the speed of the stirring head is 35 rpm, and the stirring time is 3min. When the iron-rich red mud, small-grained limestone, biochar and the iron slag in the iron bag are fully stirred and mixed, add desulfurizer according to the desulfurizer addition amount regression equation calculated value (calcium carbide small-grained limestone) 3.28kg / t iron. Then continue to lower the KR stirring head for stirring. The insertion depth of the stirring head is 1400mm, the speed of the stirring head is 90 rpm, and the stirring time is 12min. Lift the stirring head to the waiting position. After the stirring process is completed and the slag is removed, wait for the next process.

[0061] Temperature measurement, sampling, and slag removal are carried out according to process requirements. Finally, the product is hoisted to the converter platform.

[0062] Sampling analysis results: S content is 0.003%, KR desulfurization rate is (0.012-0.003) / 0.012=75%, which is lower than the average S content of 0.0042% in the historical furnace under the same conditions (molten iron temperature is 1316℃, composition is ωC=4.45%, ωSi=0.38%, ωMn=0.33%, ωP=0.098%, ωS=0.012%), and the desulfurization effect is significantly improved.

[0063] Example 2:

[0064] A red-hot ladle in normal operation from a 210t converter in heat 2. 1.3t of crushed biomass is first added to the ladle, followed by 1.5t of iron-rich red mud (one ton bag + one half-ton bag). The biomass and iron-rich red mud are evenly spread. After the continuous casting machine completes casting, 7.5t of refined slag from the ladle is poured into the ladle. The kinetic energy of the circulating slag is used to mix the refined circulating slag and biomass. A layer of 1.6t of fine-grained limestone is then evenly spread on top of the mixed slag.

[0065] The ladle is covered to insulate it. Before adding the molten iron, the lid is removed and 210 tons of molten iron is poured from a torpedo. The weight of the molten steel and the height difference create strong kinetic and potential energy, which is used to mix the mixed slag in the ladle during the pouring process. The molten iron temperature is 1338°C, and the composition is ωC = 4.42%, ωSi = 0.46%, ωMn = 0.31%, ωp = 1.16%, and ωS = 0.016%. After the molten iron is poured, it is transferred to the KR pretreatment station.

[0066] The desulfurizer dosage model was calculated based on the molten iron conditions, combined with the added biomass, iron-rich red mud, refined slag, and fine-grained limestone. A KR agitator was slowly lowered to a depth of 700 mm, at a speed of 40 rpm, for 4 minutes. Thoroughly mix the iron-rich red mud, fine-grained limestone, biochar, and iron slag in the ladle, then add the desulfurizer according to the regression calculation.

[0067] Regression analysis of the amount of desulfurizer added: (S 后 The target value is 0.003%)

[0068] Desulfurizer addition amount = -8.412 + 0.011 × T - 1.727 × Si + 68.420 × S 前 -481.320×S 后 -103.120×G 生物质原料 -87.571×G 富铁赤泥 -1.353×G 精炼循环渣 -1.620×G小粒度石灰石

[0069] =-8.412+0.011×1338-1.727×0.46+68.420×0.016-481.320×0.003-103.120×1.3 / 210-87.571×1.5 / 210-1.353×7.5 / 210-1.620×1.6 / 210

[0070] ≈3.838kg / t iron

[0071] The KR agitator is then lowered to a depth of 1500mm, with a speed of 95 rpm for 13 minutes. The speed is increased to 110 rpm for 3.5 minutes to further enhance desulfurization. The agitator is then raised to the waiting position. After the agitation process is complete and the slag is skimmed, the process is ready for the next step.

[0072] Temperature measurement, sampling, and slag removal are carried out according to process requirements. Finally, the product is hoisted to the converter platform.

[0073] Sampling analysis results: S content is 0.002%, KR desulfurization rate is (0.016-0.003) / 0.016=81.25%, which is lower than the average S content of 0.0045% in historical furnaces under the same conditions (molten iron temperature 1338°C, composition ωC=4.42%, ωSi=0.46%, ωMn=0.31%, ωp=1.16%, ωS=0.016%), which is (0.0045-0.003=0.0015) 0.0015%, and the desulfurization effect is significantly improved.

Claims

1. A control method for improving KR desulfurization effect, comprising the following steps: (1) Preliminary crushing of the biomass raw material until the length of the crushed biomass raw material is ≤50 mm; (2) adding the preliminarily crushed biomass raw material into an iron ladle; (3) adding 500-2000 kg of iron-rich red mud into the iron ladle; (4) pouring the refined circulating slag at 1520° C. to 1600° C. in the ladle after continuous casting into the iron ladle, and using the kinetic energy of the circulating slag during pouring to perform mixing, so that the refined circulating slag and the biomass raw material are fully mixed to obtain mixed slag; (5) evenly spreading small-grained limestone on the mixed slag, covering the iron ladle, and performing cracking and carbonization of the biomass raw material, pre-melting of the iron-rich red mud, and decomposition of the small-grained limestone in an oxygen-deficient environment at 600° C. to 1000° C.; (6) removing the ladle cover and pouring molten iron at 1350° C. to 1550° C. from a torpedo tank or a molten iron ditch. Due to the weight of the molten iron and the height difference, strong kinetic energy and potential energy can be generated. The kinetic energy and potential energy of the molten iron when pouring the molten iron are used to further mix the mixed slag and the small-grained limestone to obtain a mixed material; The weight ratio of the biomass raw material, the iron-rich red mud, the refining cycle slag, the small-grained limestone, and the molten iron is (0.8-1.2): (0.8-1.0): (5-7): (1.0-1.2): 140; (7) The iron ladle is transferred to the KR pretreatment work station; the KR stirring head is slowly lowered into the mixture for stirring, the stirring head is inserted into the mixture to a depth of 500 to 800 mm, the rotation speed of the stirring head is 30 to 50 rpm, and the stirring time is 3 to 5 minutes, so as to promote sufficient mixing of the mixture; (8) Add desulfurizer, continue to lower the KR stirring head until the insertion depth of the stirring head is 1400-1500 mm, and stir at a speed of 90-100 rpm for 10-15 minutes; (9) Increase the speed of the stirring head to 110 rpm and continue stirring for 1 to 5 minutes to further deep desulfurization; (10) lifting the stirring head to the waiting position to end stirring; (11) Carry out temperature measurement, sampling, and slag removal according to process requirements; finally, wait for lifting to the converter platform.

2. The control method for improving KR desulfurization effect according to claim 1, wherein the biomass raw material comprises one or more of wood, grass, rice straw, rape straw, corn straw, waste wood, and garden prunings.

3. The control method for improving KR desulfurization effect according to claim 1, wherein the preliminary crushing is performed using a crusher.

4. The control method for improving KR desulfurization effect according to claim 1, wherein the iron ladle is a red-hot iron ladle with normal turnover.

5. The control method for improving KR desulfurization effect according to claim 1, wherein the iron-rich red mud is a solid waste from the Bayer process for producing alumina, and the iron-rich red mud comprises: Fe2O3 40~60wt%, SiO2 4~20wt%, Al2O3 12~20wt%, CaO 5~10wt%, Na2O 2~10wt%, TiO2 1~10wt%, and the remaining ingredients are <5wt%.

6. The control method for improving KR desulfurization effect according to claim 1, wherein the iron-rich red mud is air-dried or oven-dried and then bagged in 1-ton bags, half-ton bags, or 20 kg small bags for standby use.

7. The control method for improving KR desulfurization effect according to claim 1, wherein the refined circulating slag comprises: SiO22~12wt%, Al2O3 22~37wt%, CaO 35~56wt%, MgO 1~10wt%.

8. The control method for improving KR desulfurization effect according to claim 1, wherein the particle size of the small-grained limestone is in the range of 5 to 15 mm.

9. The control method for improving KR desulfurization effect according to claim 1, wherein the desulfurizer is limestone or calcium carbide.

10. The control method for improving the KR desulfurization effect according to claim 1, wherein the amount of the desulfurizer added is calculated based on the following formula according to the conditions of the molten iron, the weight of the added biomass raw material, the weight and composition of the iron-rich red mud, the weight and composition of the refining cycle slag, and the weight of the small-particle limestone: Desulfurizer addition amount = -8.412 + 0.011 × T - 1.727 × Si + 68.420 × S 前 -481.320×S 后 -103.120×G 生物质原料 -87.571×G 富铁赤泥 -1.353×G 精炼循环渣 -1.620×G 小粒度石灰石 in: T is the molten iron temperature, unit: °C Si is the silicon content of molten iron, unit: % S 前 Sulfur content of molten iron before pretreatment, unit: % S 后 Sulfur content of molten iron after pretreatment, unit: % G 生物质原料 The weight of biomass raw materials added to this furnace, converted into tons of iron, unit: kg / t G 富铁赤泥 The weight of the iron-rich red mud added to this furnace, converted into tons of iron, unit: kg / t G 精炼循环渣 The weight of the refining cycle slag added to this furnace, converted into tons of iron, unit: kg / t G 小粒度石灰石 The weight of small-grained limestone added to this furnace, converted into tons of iron, unit: kg / t.