A method for reducing the cost of hot metal desulphurization

Abstract

This technical solution belongs to the field of metal smelting technology, and particularly relates to a cost-reducing method for desulfurizing molten iron. The purpose of this invention is to provide a heating agent, which, by weight, comprises 15-20 parts of aluminum powder with a particle size less than 0.1 mm, 30-50 parts of iron oxide with a particle size less than 0.1 mm, 10-15 parts of potassium nitrate with a particle size less than 0.6 mm, 15-20 parts of carbon powder with a particle size less than 0.02 mm, 3-5 parts of binder, and 4-6 parts of carbonized rice husk. This invention utilizes the heating agent to increase the temperature while simultaneously altering the composition of the desulfurization slag. The carbonized rice husk provides insulation, creating favorable thermodynamic conditions for desulfurization, improving the fluidity of the desulfurization slag, and promoting slag-iron separation, thus achieving efficient and stable desulfurization operations overall.

Description

Technical Field

[0001] This technical solution belongs to the field of metal smelting technology, and in particular relates to a cost-effective method for desulfurizing molten iron. Background Technology

[0002] Desulfurization in hot metal pretreatment is a crucial step in improving steel quality. The development of this technology has always revolved around optimizing the thermodynamic and kinetic conditions of the reaction, with the core focus on creating a high-temperature environment more conducive to the forward desulfurization reaction and enhancing the mass transfer efficiency between reactants. Currently, two methods are widely used for hot metal desulfurization: the injection method and the KR method.

[0003] The injection method uses an inert gas as a carrier to spray desulfurizing powder into molten iron through a spray gun, allowing the desulfurizing agent to react with the molten iron and achieve desulfurization. However, the contact between the desulfurizing powder and the sulfur in the molten iron is insufficient, resulting in low desulfurization efficiency, high consumption of desulfurizing agent, and sticky slag, leading to poor slag-iron separation.

[0004] The KR process, developed in Japan, involves inserting a stirring head into molten iron to a certain depth. The vortex generated by the vigorous stirring action of a large agitator ensures thorough contact and reaction between the desulfurizing powder and the molten iron, achieving desulfurization. The KR process offers higher desulfurization efficiency and lower powder consumption, but it suffers from a significant temperature drop and poor slag-iron separation. To address these shortcomings, a method has been proposed that involves adding an exothermic agent to increase the slag layer temperature and promote slag-metal desulfurization and slag-iron separation.

[0005] To compensate for the drawbacks of large temperature drops and poor slag condition in the injection and KR methods, the technological development path focuses on thermal compensation and slag system modification. The mainstream approach involves adding exothermic agents or slag conditioners during the desulfurization process to increase the local slag-metal interface temperature and lower the slag's melting point and viscosity, thereby thermodynamically promoting the desulfurization reaction and kinetically improving slag-iron separation. For example, Chinese patent application CN201310632828.4 proposes a stepwise desulfurization slag removal method for vanadium-titanium molten iron. The core of this method is to add a specific desulfurization slag conditioner (mainly containing CaO, SiO2, and Al2O3, supplemented with Na2CO3 and CaF2) twice, before and after desulfurization. Stirring improves the slag condition and controls the degree of slag removal, ultimately aiming to reduce iron loss during slag removal. While this technology clearly aims to improve slag condition and reduce iron loss, its slag conditioner formulation still relies on fluorite (CaF2) and alkali (Na2CO3) as effective fluxing and slag conditioning components. In practical applications, this exacerbates the erosion of the refractory material in the molten iron ladle and fails to address the temperature drop issue during the process. Another Chinese patent application, CN202111486012.6, provides a desulfurization slag modifier primarily based on Na2CO3. Its design concept involves retaining a portion of the previous heat's "pre-slag" and using this modifier to modify it, restoring and enhancing its desulfurization capacity. This method aims to reduce the need for thorough slag removal, thereby shortening processing time and reducing temperature drop. However, the modifier contains no less than 90% Na2CO3 and is supplemented with lime and fluorite. Although it directly addresses the need for heat preservation and cooling, it leads to more prominent new problems: First, the use of high alkalinity and fluorite will accelerate the wear and tear of refractory materials and increase production costs; second, the use of large amounts of sodium salts is prone to generating volatiles and dust, which is not environmentally friendly and has high subsequent environmental protection costs.

[0006] In summary, the current technical route based on the KR method, supplemented by various slag modifiers, has always been constrained in its development. It is difficult to simultaneously achieve a balance between "desulfurization efficiency," "temperature drop control," "slag-iron separation," and "refractory material erosion and cost" in both physical and chemical aspects. Although existing technologies have made improvements in specific aspects (such as reducing iron loss and temperature drop), they generally introduce new defects, especially severe erosion of refractory materials and environmental challenges caused by the use of large amounts of alkali metals and fluorides. These have become the technical bottlenecks that urgently need to be overcome in this field.

[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 technical solution belongs to the field of metal smelting technology, and in particular relates to a cost-effective method for desulfurizing molten iron.

[0009] The purpose of this invention is to provide a heating agent, which, by weight, comprises 15-20 parts aluminum powder, 30-50 parts iron oxide red, 10-15 parts potassium nitrate, 15-20 parts carbon powder, 3-5 parts binder, and 4-6 parts carbonized rice husk.

[0010] Preferably, by weight, the heating agent comprises 15-20 parts of aluminum powder with a particle size of less than 0.1 mm, 30-50 parts of iron oxide with a particle size of less than 0.1 mm, 10-15 parts of potassium nitrate with a particle size of less than 0.6 mm, 15-20 parts of carbon powder with a particle size of less than 0.02 mm, 3-5 parts of binder, and 4-6 parts of carbonized rice husk.

[0011] According to a preferred embodiment, the heating agent comprises 15 parts of aluminum powder with a particle size of less than 0.1 mm, 30 parts of iron oxide red with a particle size of less than 0.1 mm, 10 parts of potassium nitrate with a particle size of less than 0.6 mm, 15 parts of carbon powder with a particle size of less than 0.02 mm, 3 parts of binder, and 4 parts of carbonized rice husk.

[0012] According to a preferred embodiment, the heating agent comprises 20 parts of aluminum powder with a particle size of less than 0.1 mm, 50 parts of iron oxide red with a particle size of less than 0.1 mm, 15 parts of potassium nitrate with a particle size of less than 0.6 mm, 20 parts of carbon powder with a particle size of less than 0.02 mm, 5 parts of binder, and 6 parts of carbonized rice husk.

[0013] According to a preferred embodiment, the heating agent comprises 17 parts of aluminum powder with a particle size of less than 0.1 mm, 40 parts of iron oxide red with a particle size of less than 0.1 mm, 13 parts of potassium nitrate with a particle size of less than 0.6 mm, 17 parts of carbon powder with a particle size of less than 0.02 mm, 4 parts of binder, and 5 parts of carbonized rice husk.

[0014] According to a preferred embodiment, the adhesive is polyvinyl alcohol.

[0015] One objective of this invention is to provide a cost-effective method for desulfurizing molten iron, comprising the following steps: S1 Add the above-mentioned exothermic agent to the iron raw material at a rate of 1.5-2.5 kg / t iron; S2 injection method for desulfurization of molten iron.

[0016] According to a preferred embodiment, in S1, the heating agent is uniformly added to the surface of the molten iron.

[0017] According to a preferred embodiment, in S2, the blowing method involves spraying passivated active lime and magnesium powder with a particle size of less than 0.1 mm into the molten iron. The spraying conditions are a pressure of 0.45-0.6 MPa and an inert gas as the spraying carrier.

[0018] According to a preferred embodiment, the jet carrier is nitrogen.

[0019] According to a preferred embodiment, the injection rate of passivating quicklime is 2-4 kg / t iron; the injection rate of magnesium powder is 0.6-1.0 kg / t iron.

[0020] One objective of this invention is to provide a cost-reducing hot metal desulfurization system, comprising a distributor containing a heating agent, a container containing molten iron, a spray gun, and a control console, wherein the control console is configured as follows: Based on the weight of the molten iron in the container, and with a calculated addition of 1.5-2.5 kg per ton of molten iron, the distributor is controlled to uniformly add the corresponding amount of the above-mentioned heating agent to the surface of the molten iron in the container. Insert the spray gun into the container to a distance of 400-500 mm from the bottom, so that the spray gun uses nitrogen as a carrier and sprays passivating active lime with a particle size of less than 0.1 mm under a pressure of 0.45-0.6 MPa. The spraying amount of passivating active lime is 2-4 kg / t iron. Then spray passivating magnesium powder at a spraying amount of 0.6-1.0 kg / t iron.

[0021] According to a preferred embodiment, the container is a molten iron ladle.

[0022] This exothermic agent is used in the desulfurization process of molten iron to achieve the technical effects of sustained heat compensation enhancement, optimized desulfurization kinetics, and improved slag-iron separation.

[0023] 1. Enhanced thermal compensation durability After being added to molten iron, this exothermic agent continuously releases heat into the molten iron, effectively compensating for the temperature drop in traditional injection desulfurization processes caused by the addition of cold desulfurization materials, the endothermic effect of the desulfurization reaction itself, and the loss of heat radiation and conduction between the molten iron and the environment. Specifically, according to the experimental data recorded in this application, the temperature drop in conventional injection desulfurization is 8-15℃, while the temperature compensation with the addition of the exothermic agent is 7-12℃.

[0024] The use of the exothermic agent in this application not only significantly reduces the actual temperature drop of molten iron, creating better thermodynamic and kinetic conditions for desulfurization, but also accelerates the mass transfer process and reaction rate of the desulfurization reaction, thereby improving the desulfurization effect.

[0025] 2. Improved slag-iron separation effect The exothermic reaction of this exothermic agent effectively alters the properties of the molten slag and reduces its hemispherical temperature. According to relevant experimental data, compared to Comparative Example 1, this exothermic agent reduces the hemispherical temperature of the slag by 50-60℃, improving its fluidity and promoting slag-iron separation.

[0026] In summary, by achieving the aforementioned technical effects, this invention utilizes an exothermic agent to increase temperature, while simultaneously altering the composition of the desulfurization slag and using carbonized rice husks for insulation, creating favorable thermodynamic conditions for desulfurization, improving the fluidity of the desulfurization slag, and promoting slag-iron separation. Overall, this achieves efficient and stable desulfurization operations. This technical solution, while ensuring a high desulfurization rate, reduces desulfurizing agent consumption, shortens the processing cycle, reduces heat loss from molten iron, and ultimately yields cleaner molten iron (capable of desulfurization to 12 ppm) and lower overall production costs (total iron loss reduced by 1.0 kg / t iron), demonstrating significant technical and economic benefits. 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 This embodiment relates to a cost-effective method for desulfurizing molten iron.

[0030] By weight, the heating agent contains 15 parts aluminum powder (particle size less than 0.1 mm), 30 parts iron oxide red (particle size less than 0.1 mm), 10 parts potassium nitrate (particle size less than 0.6 mm), 15 parts carbon powder (particle size less than 0.02 mm), and 3 parts binder (polyvinyl alcohol).

[0031] The heating agent particles are 4-6 mm. After 1 min, 4 parts of carbonized rice husk are added to the surface. The above-mentioned components are mixed and granulated to 4-6 mm. After 1 min, carbonized rice husk is added again.

[0032] Step 1: Add heating agent to the surface of the molten iron ladle using a material distributor, at a rate of 1.5 kg / t of iron.

[0033] Step 2: Insert the spray gun into the molten iron ladle and stop when it is 400 mm from the bottom of the ladle. Using nitrogen as a carrier, at a pressure of 0.6 MPa, spray in passivating quicklime (particle size less than 0.1 mm) at a rate of 2 kg / t iron. Then spray in passivating magnesium powder at a rate of 0.6 kg / t iron.

[0034] The results showed that the sulfur content in the molten iron was reduced to 18 ppm. Compared with conventional pretreatment desulfurization, the desulfurization rate in this embodiment was increased by 4%.

[0035] In addition, the results also showed that the desulfurization slag fluidity was enhanced (the hemispherical temperature of the slag decreased by 50-60℃), the total iron loss decreased by 0.8 kg / t iron, and the cost decreased by 1.9 yuan / t iron.

[0036] Example 2 By weight, the heating agent contains 20 parts aluminum powder (particle size less than 0.1 mm), 50 parts iron oxide red (particle size less than 0.1 mm), 15 parts potassium nitrate (particle size less than 0.6 mm), 20 parts carbon powder (particle size less than 0.02 mm), and 5 parts binder (polyvinyl alcohol). The heating agent particles are 4-6 mm in size. After 1 minute, 6 parts carbonized rice husks are added to the surface.

[0037] Step 1: Add heating agent to the surface of the molten iron ladle using a material distributor, at a rate of 2.5 kg / t of iron.

[0038] Step 2: Insert the spray gun into the molten iron ladle and stop when it is 450 mm from the bottom of the ladle. Using nitrogen as a carrier, at a pressure of 0.45 MPa, spray in passivating quicklime (particle size less than 0.1 mm) at a rate of 4 kg / t iron. Then spray in passivating magnesium powder at a rate of 1 kg / t iron.

[0039] The results showed that the sulfur content in the molten iron was reduced to 12 ppm. Compared with Comparative Example 1, the desulfurization rate in this embodiment was increased by 8%.

[0040] In addition, the results also showed that the desulfurization slag fluidity was improved, the total iron loss was reduced by 1.0 kg / t iron, and the cost was reduced by 2.6 yuan / t iron.

[0041] Example 3 By weight, the heating agent contains 17 parts aluminum powder (particle size less than 0.1 mm), 40 parts iron oxide red (particle size less than 0.1 mm), 13 parts potassium nitrate (particle size less than 0.6 mm), 17 parts carbon powder (particle size less than 0.02 mm), and 4 parts binder (polyvinyl alcohol). The heating agent particles are 4-6 mm in size. After 1 minute, 5 parts carbonized rice husks are added to the surface.

[0042] Step 1: Add heating agent to the surface of the molten iron ladle using a material distributor, at a rate of 2.0 kg / t of iron.

[0043] Step 2: Insert the spray gun into the molten iron ladle and stop when it is 500 mm from the bottom of the ladle. Using nitrogen as a carrier, at a pressure of 0.5 MPa, spray in passivating quicklime (particle size less than 0.1 mm) at a rate of 3 kg / t iron. Then spray in passivating magnesium powder at a rate of 0.8 kg / t iron.

[0044] The results showed that the sulfur content in the molten iron was reduced to 15 ppm. Compared with Comparative Example 1, the desulfurization rate in this embodiment was increased by 6%.

[0045] Total iron loss was reduced by 0.9 kg / t iron, and cost was reduced by 2.3 yuan / t iron.

[0046] Comparative Example 1 Insert the spray gun into the molten iron ladle, 500 mm from the bottom, using nitrogen as a carrier gas at a pressure of 0.6 MPa, and spray in passivating quicklime (particle size less than 0.1 mm) at a rate of 4 kg / t iron. Then spray in passivating magnesium powder at a rate of 1.2 kg / t iron.

[0047] The results showed that the sulfur content of the molten iron was reduced to below 20 ppm, the desulfurization rate was 82%, and the total iron loss was 10 kg / t of iron.

[0048] Meanwhile, tests showed that compared to the conventional injection desulfurization process (Comparative Example 1) which resulted in a temperature drop of 8-15℃, the addition of an exothermic agent (Examples 1, 2, and 3) provided a temperature compensation of 7-12℃.

[0049] 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 heating agent, characterized in that, By weight, it contains 15-20 parts aluminum powder, 30-50 parts iron oxide red, 10-15 parts potassium nitrate, 15-20 parts carbon powder, 3-5 parts binder and 4-6 parts carbonized rice husk.

2. The heating agent according to claim 1, characterized in that, The heating agent contains 15 parts aluminum powder with a particle size of less than 0.1 mm, 30 parts iron oxide red with a particle size of less than 0.1 mm, 10 parts potassium nitrate with a particle size of less than 0.6 mm, 15 parts carbon powder with a particle size of less than 0.02 mm, 3 parts binder and 4 parts carbonized rice husk.

3. The heating agent according to claim 1, characterized in that, The heating agent contains 20 parts aluminum powder with a particle size of less than 0.1 mm, 50 parts iron oxide with a particle size of less than 0.1 mm, 15 parts potassium nitrate with a particle size of less than 0.6 mm, 20 parts carbon powder with a particle size of less than 0.02 mm, 5 parts binder, and 6 parts carbonized rice husk.

4. The heating agent according to claim 1, characterized in that, The heating agent contains 17 parts aluminum powder with a particle size of less than 0.1 mm, 40 parts iron oxide red with a particle size of less than 0.1 mm, 13 parts potassium nitrate with a particle size of less than 0.6 mm, 17 parts carbon powder with a particle size of less than 0.02 mm, 4 parts binder and 5 parts carbonized rice husk.

5. A cost-reducing method for desulfurizing molten iron, characterized in that, Includes the following steps: S1. Add the exothermic agent according to any one of claims 1-4 to the iron raw material, the amount added being 1.5-2.5 kg / t iron; S2 injection method for desulfurization of molten iron.

6. The cost-reducing hot metal desulfurization method according to claim 5, characterized in that, In S2, the spraying method involves spraying passivated active lime and passivated magnesium powder with a particle size of less than 0.1 mm into molten iron. The spraying conditions are a pressure of 0.45-0.6 MPa and an inert gas as the spraying carrier.

7. The cost-reducing hot metal desulfurization method according to claim 6, characterized in that, The jet carrier is nitrogen.

8. The cost-reducing hot metal desulfurization method according to claim 6, characterized in that, The amount of passivated active lime injected is 2-4 kg / t iron; the amount of magnesium powder injected is 0.6-1.0 kg / t iron.

9. A cost-reducing hot metal desulfurization system, characterized in that, The device includes a cloth feeder containing a heating agent, a container containing molten iron, a spray gun, and a control console, wherein the control console is configured as follows: Based on the weight of the molten iron in the container, and with a calculated addition of 1.5-2.5 kg per ton of molten iron, the distributor is controlled to uniformly add the corresponding amount of the heating agent described in any one of claims 1-4 to the surface of the molten iron in the container. Insert the spray gun into the container to a distance of 400-500 mm from the bottom. Use nitrogen as a carrier and spray passivating quicklime with a particle size of less than 0.1 mm at a pressure of 0.45-0.6 MPa. The spraying rate of passivating quicklime is 2-4 kg / t iron. Then spray passivating magnesium powder at a rate of 0.6-1.0 kg / t iron.

10. The cost-reducing hot metal desulfurization system according to claim 9, characterized in that, The container is a molten iron ladle.