A method for desulphurization of molten iron

Abstract

This invention belongs to the field of metal smelting technology, and particularly relates to a method for desulfurizing molten iron. The method includes the following steps: S1. Adding a finished heating agent to the molten iron at a rate of 2-3 kg / t of iron. The heating agent comprises, by weight, 18-24 parts of aluminum powder with a particle size less than 0.1 mm, 40-60 parts of iron oxide with a particle size less than 0.1 mm, 10-15 parts of carbon powder with a particle size less than 0.02 mm, and 3-5 parts of binder. The heating agent components are mixed and granulated to a size of 2-3 mm, then wrapped in a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles; S2. KR method molten iron desulfurization. This invention can be directly adapted to the KR method molten iron desulfurization process. By directly adding the heating agent to the molten iron to be desulfurized, the temperature of the molten iron is increased, improving the desulfurization effect.

Description

Technical Field

[0001] This invention belongs to the field of metal smelting technology, and particularly relates to a method for desulfurizing molten iron. Background Technology

[0002] In the field of molten iron pretreatment, the KR mechanical stirring method is widely used due to its highly efficient desulfurization capability. This method uses a powerful stirrer to create a vortex in the molten iron, ensuring thorough mixing of the desulfurizing agent with the molten iron. This significantly improves the mass transfer efficiency at the reaction interface, thereby achieving a high desulfurization depth and low desulfurizing agent consumption.

[0003] However, the KR process has a contradictory design flaw: the intense stirring and long reaction time lead to a significant drop in the temperature of the molten iron. This temperature drop not only directly weakens the thermodynamic driving force of the desulfurization reaction, but also makes the generated desulfurized slag viscous and its fluidity deteriorate due to the temperature decrease, ultimately resulting in difficulties in slag-iron separation, low efficiency in slag removal operations, and severe iron loss.

[0004] In existing technologies, the KR method often involves adding various heating agents (or exothermic agents, slag conditioners) during or before / after the KR stirring process. The primary purpose is to rapidly compensate for the system's heat loss and increase the local temperature at the slag-gold interface through the exothermic oxidation reaction of the heating agent. From a thermodynamic perspective, increasing the temperature can effectively reduce the viscosity of high-alkalinity desulfurization slag and improve its fluidity, theoretically facilitating subsequent slag removal operations. This approach has led to the development of various exothermic mixtures based on lime, aluminum powder, ferrosilicon, etc.

[0005] However, with the increasing demands for molten iron quality in existing technologies, the limitations of simple physical heating have become increasingly apparent. To achieve rapid heating and fluxing, highly corrosive components, such as fluorite (CaF2) or alkali metal salts (Na2CO3), are often introduced into the formulation. These components drastically accelerate the erosion rate of the refractory lining of the ladle at high temperatures, leading to a significant reduction in lining life. This not only increases the cost of refractory materials but also disrupts the production rhythm due to frequent ladle repairs. Even more seriously, the eroded and flaked refractory material enters the slag, further deteriorating its properties and making slag removal more difficult, creating a vicious cycle. Finally, from an operational perspective, excessive addition of exothermic agents in pursuit of heating effects may lead to an unnecessary increase in slag volume or the generation of large amounts of flue gas, also negatively impacting slag removal efficiency and the working environment.

[0006] Therefore, the heating agent technology currently used in the KR process has the following problems: On the one hand, physical heating is necessary and effective in alleviating temperature drop and improving the initial slag state, but it relies on impeller mechanical strong stirring to achieve deep mixing and mass transfer between molten iron and desulfurizing agent. This is prone to excessive temperature drop, leading to increased molten iron viscosity and insufficient thermodynamic driving force for the desulfurization reaction, particularly hindering the reaction process in the deep desulfurization stage. On the other hand, the chemical composition of the heating agent has side effects—the strong stirring condition places high demands on the melting and flow characteristics of the desulfurization slag. If the slag viscosity is too high and the fluidity is poor, a large number of slag-coated iron clusters will form during strong stirring, exacerbating molten iron loss and hindering effective contact between the desulfurizing agent and molten iron, weakening the mass transfer enhancement advantage of the stirring process itself—severely restricting its overall benefits and making it difficult to simultaneously achieve the two goals of "high-efficiency desulfurization" and "clean, low-consumption slag removal." How to design a new type of additive or composite process that can effectively provide heat energy, optimize slag phase structure, and possess both refractory material-friendly and environmentally friendly characteristics has become a key technological bottleneck.

[0007] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the inventors studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0008] This invention belongs to the field of metal smelting technology, and particularly relates to a method for desulfurizing molten iron.

[0009] One objective of this invention is to provide a method for desulfurizing molten iron, comprising the following steps: S1 Add the finished heating agent to the molten iron at a rate of 2-3 kg / t of iron. The heating agent contains, by weight, 18-24 parts of aluminum powder, 40-60 parts of iron oxide, 10-15 parts of carbon powder, and 3-5 parts of binder. Then, mix the above heating agent components and granulate them to 2-3 mm. Wrap each granule with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles. S2 KR method for desulfurization of molten iron.

[0010] According to a preferred embodiment, the aluminum powder particle size is less than 0.1 mm.

[0011] According to a preferred embodiment, the iron oxide particle size is less than 0.1 mm.

[0012] According to a preferred embodiment, the toner particle size is less than 0.02 mm.

[0013] According to a preferred embodiment, the adhesive is polyvinyl alcohol.

[0014] According to a preferred embodiment, the passivated active lime has a particle size of less than 2 mm.

[0015] According to a preferred embodiment, the heating agent comprises, by weight, 18 parts aluminum powder, 40 parts iron oxide red, 10 parts carbon powder and 3 parts binder.

[0016] According to a preferred embodiment, the heating agent comprises, by weight, 24 parts aluminum powder, 60 parts iron oxide red, 15 parts carbon powder and 5 parts binder.

[0017] According to a preferred embodiment, the heating agent comprises, by weight, 21 parts aluminum powder, 50 parts iron oxide red, 12 parts carbon powder and 4 parts binder.

[0018] According to a preferred embodiment, the KR method includes the following steps: inserting the KR stirring head into the molten iron, controlling the rotation speed at 100-130 rpm; adding 4-8 kg / t of passivating quicklime 1 min after adding the finished heating agent. Preferably, the passivating quicklime has a particle size of less than 2 mm.

[0019] One of the objectives of this invention is to provide a system for desulfurizing molten iron, which includes a cloth-feeding unit containing a heating agent, a reaction unit containing molten iron, and a stirring unit.

[0020] Insert the stirring unit into the reaction vessel and stir at 100-130 rpm.

[0021] In the fabric unit, the finished heating agent is added to the reaction unit at a rate of 2-3 kg / t of iron. After the reaction is heated, passivated quicklime with a rate of 4-8 kg / t of iron is added to the reaction unit. The heating agent contains, by weight, 18-24 parts aluminum powder, 40-60 parts iron oxide red, 10-15 parts carbon powder, and 3-5 parts binder. The above heating agent components are mixed and granulated to a size of 2-3 mm, and then wrapped with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles.

[0022] Preferably, the reaction unit is a molten iron ladle.

[0023] The beneficial effects of this technical solution are: This invention is directly applicable to the KR method for hot metal desulfurization. The exothermic agent particles are encased in iron sheets and dispersed within the molten iron under KR stirring. The reaction exhibits high exothermic efficiency, rapidly raising the temperature of the molten iron and creating better desulfurization conditions. Simultaneously, the Al2O3 generated by the exothermic agent modifies the desulfurization process, enhancing the desulfurization effect.

[0024] 1. The finished exothermic agent is dispersed in the molten iron under KR stirring, exhibiting high exothermic reaction efficiency and rapidly increasing the temperature of the molten iron. This compensates for the significant heat loss caused by the strong stirring in the KR method, creating better desulfurization conditions. Related experimental data shows that when comparing with Comparative Example 1 (which did not add this exothermic agent), with all other initial conditions for molten iron, KR desulfurization process parameters, and operating procedures remaining completely identical, the sulfur content of the molten iron at the desulfurization endpoint can be stably reduced to below 13-18 ppm, with a desulfurization rate 5%-7% higher than Comparative Example 1, achieving a more efficient deep desulfurization effect in the molten iron. 2. The products of the exothermic agent can modify the desulfurization slag, reduce the hemispherical temperature of the molten slag by 35-45℃, and provide a chemical basis for improving the fluidity of the molten slag.

[0025] Meanwhile, based on the significant reduction in the temperature of the molten slag hemisphere, the viscosity of the molten slag decreases substantially and its flow properties are fundamentally improved, which is suitable for the molten slag flow requirements of the KR method's strong stirring. During the stirring process, the low-viscosity molten slag can be uniformly dispersed into a continuous liquid film to encapsulate the desulfurizing agent particles, avoiding the agglomeration and deactivation of the desulfurizing agent. At the same time, it can quickly adsorb and enrich the desulfurization reaction products, preventing them from dissolving back into the molten iron, further ensuring the deep desulfurization effect. After stirring stops, the low-viscosity molten slag can quickly agglomerate and float, significantly shortening the slag-iron separation time and effectively reducing the slag-iron encapsulation phenomenon formed during strong stirring, achieving a total iron loss reduction of 1.0-1.3 kg / t iron compared to the comparative example without added exothermic agent.

[0026] 3. Improved desulfurization efficiency, reduced iron loss, and optimized auxiliary material consumption jointly reduce the overall cost of the desulfurization process by 2.4-3.1 yuan / t iron compared to the control group without the added exothermic agent. In addition, the excellent fluidity of the molten slag can reduce the running resistance of the stirring impeller, reduce equipment energy consumption and wear, and further expand the application value of this exothermic agent in the KR desulfurization process. Detailed Implementation

[0027] In the description of this invention, terminology is used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0028] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the materials, reagents or instruments used, unless otherwise specified by the manufacturer, are all commercially available reagents and materials; the conditions not specified in the examples are all carried out according to conventional conditions or conditions recommended by the manufacturer. At the same time, the present invention does not limit the source of the raw materials used. Unless otherwise specified, the raw materials used in the present invention are all commercially available products in this technical field.

[0029] Example 1 Insert the KR stirring head into the molten iron, control the rotation speed at 100 rpm, and add the finished heating agent to the surface of the molten iron ladle through the material distributor at a rate of 2.0 kg / t iron.

[0030] By weight, the heating agent contains 18 parts aluminum powder (particle size less than 0.1 mm), 40 parts iron oxide red (particle size less than 0.1 mm), 10 parts carbon powder (particle size less than 0.02 mm), and 3 parts binder (polyvinyl alcohol).

[0031] Then, the above-mentioned heating agent components are mixed and granulated to a size of 2-3 mm, and then wrapped with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles.

[0032] After the reaction is exothermic for 1 minute, add 4 kg / t of passivating active lime (particle size less than 2 mm).

[0033] The results showed that the sulfur content of molten iron was reduced to 18 ppm, the desulfurization rate increased by 5%, the total iron loss decreased by 1 kg / t of iron, and the cost decreased by 2.4 yuan / t of iron.

[0034] Example 2 Insert the KR stirring head into the molten iron, control the rotation speed at 130 rpm, and add the finished heating agent to the surface of the molten iron ladle through the material distributor at a rate of 3 kg / t of iron.

[0035] By weight, the heating agent contains 24 parts aluminum powder (particle size less than 0.1 mm), 60 parts iron oxide red (particle size less than 0.1 mm), 15 parts carbon powder (particle size less than 0.02 mm), and 5 parts binder (polyvinyl alcohol).

[0036] Then, the above-mentioned heating agent components are mixed and granulated to 2-3 mm, and then wrapped with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles.

[0037] After the reaction is exothermic for 1 minute, add 8 kg / t of passivating active lime (particle size less than 2 mm).

[0038] The results showed that the sulfur content of molten iron was reduced to below 13 ppm, the desulfurization rate increased by 7%, the total iron loss decreased by 1.3 kg / t iron, and the cost decreased by 3.1 yuan / t iron.

[0039] Example 3 Insert the KR stirring head into the molten iron and control the rotation speed at 115 rpm. Add the finished heating agent to the surface of the molten iron ladle through the distributor at a rate of 2.5 kg / t of iron.

[0040] By weight, the heating agent contains 21 parts aluminum powder (particle size less than 0.1 mm), 50 parts iron oxide red (particle size less than 0.1 mm), 12 parts carbon powder (particle size less than 0.02 mm), and 4 parts binder (polyvinyl alcohol).

[0041] Then, the above-mentioned heating agent components are mixed and granulated to 2-3 mm, and then wrapped with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles.

[0042] After the reaction generates heat for 1 minute, add 6 kg / t of passivating active lime (particle size less than 2 mm).

[0043] The results showed that the sulfur content of molten iron was reduced to below 15.5 ppm, the desulfurization rate was increased by more than 6%, the total iron loss was reduced by 1.15 kg / t of iron, and the cost was reduced by more than 2.8 yuan / t of iron.

[0044] Comparative Example 1 Add 8 kg / t of passivating quicklime (particle size less than 2 mm) and insert the KR stirring head into the molten iron, controlling the rotation speed at 130 rpm.

[0045] The results showed that the sulfur content of the molten iron was reduced to below 20 ppm, the desulfurization rate was 85%, and the total iron loss was 25 kg / t of iron.

[0046] Furthermore, compared to Comparative Example 1, this exothermic agent significantly improved the fluidity and separation effect of the molten slag, and reduced the hemispherical temperature of the slag.

[0047] It should be noted that the specific embodiments described above are exemplary, and those skilled in the art can devise various solutions inspired by the disclosure of this invention, all of which fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification is illustrative and not intended to limit the scope of the claims. The scope of protection of this invention is defined by the claims and their equivalents.

Claims

1. A method for desulfurizing molten iron, characterized in that, Includes the following steps: S1 Add the finished heating agent to the molten iron at a rate of 2-3 kg / t of iron. The heating agent contains, by weight, 18-24 parts of aluminum powder, 40-60 parts of iron oxide, 10-15 parts of carbon powder, and 3-5 parts of binder. Then, mix the above heating agent components and granulate them to 2-3 mm. Wrap each granule with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80 g of heating agent particles. S2 KR method for desulfurization of molten iron.

2. The hot metal desulfurization method according to claim 1, characterized in that, The heating agent comprises, by weight, 18 parts aluminum powder, 40 parts iron oxide red, 10 parts carbon powder and 3 parts binder.

3. The hot metal desulfurization method according to claim 1, characterized in that, The heating agent comprises, by weight, 24 parts aluminum powder, 60 parts iron oxide red, 15 parts carbon powder and 5 parts binder.

4. The hot metal desulfurization method according to claim 1, characterized in that, The heating agent comprises, by weight, 21 parts aluminum powder, 50 parts iron oxide red, 12 parts carbon powder and 4 parts binder.

5. The hot metal desulfurization method according to claim 1, characterized in that, The KR method includes the following steps: Insert the KR stirring head into the molten iron and control the rotation speed at 100-130 rpm; Add 4-8 kg / t of passivated active lime with iron 1 minute after adding the finished heating agent.

6. The hot metal desulfurization method according to claim 1, characterized in that, The passivated active lime has a particle size of less than 2 mm.

7. The hot metal desulfurization method according to claim 1, characterized in that, The adhesive is polyvinyl alcohol.

8. The hot metal desulfurization method according to claim 1, characterized in that, The passivated active lime has a particle size of less than 2 mm.

9. A system for desulfurizing molten iron, comprising a cloth-feeding unit containing a heating agent, a reaction unit containing molten iron, and a stirring unit, wherein, The stirring unit is inserted into the reaction vessel and stirred at a speed of 100-130 rpm; The fabric unit adds the finished heating agent to the reaction unit at a rate of 2-3 kg / t of iron. After the reaction is heated, 4-8 kg / t of passivated active lime is added to the reaction unit. The heating agent contains, by weight, 18-24 parts of aluminum powder, 40-60 parts of iron oxide, 10-15 parts of carbon powder and 3-5 parts of binder. The above-mentioned heating agent components are mixed and granulated to a size of 2-3 mm, and then wrapped with a 1 mm thick ultra-low carbon steel sheet to form a finished heating agent containing 60-80g of heating agent particles.

10. The system according to claim 9, characterized in that, The reaction unit is a molten iron ladle.