A method for desulfurization of refining slag based on electric field strengthening

Abstract

The application discloses a refining slag desulfurization method based on electric field strengthening and belongs to the field of high-temperature steel slag processing and treatment. According to the requirements of electric field strengthening on the electric conductivity and viscosity of the refining slag, the amount of the modifying agent is calculated; the slag basin of the refining slag is transferred to a treatment workshop, the slag is poured into a molten iron tank, the modifying agent is added at the same time, and the impact force of the slag pouring is used to stir and mix the slag; a direct current electric field is applied between the slag and the gold; finally, the refining slag on the surface of the molten iron is removed, and low-sulfur refining slag and sulfur-containing molten iron are obtained. After the desulfurization slag is modified, the direct current electric field is used to strengthen the migration of the sulfur element from the refining slag to the molten iron, the rate and limit of the desulfurization reaction are greatly improved, the treatment process is simple, the cost is low, the large-scale utilization of the refining slag is realized, and economic value is brought to the enterprise.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature steel slag processing, and more specifically, relates to a desulfurization method for refining slag based on electric field enhancement. Background Technology

[0002] In recent years, the booming development of China's metallurgical industry has generated a large amount of metallurgical slag, putting enormous pressure on environmental protection. This has made the secondary recycling of metallurgical waste resources, such as refining slag, a key focus for the global metallurgical industry for many years. Among the various metallurgical slags generated, blast furnace slag has the highest utilization rate, reaching 98%, while steel slag has a slightly lower utilization rate of about 65%. Compared with these two types of waste slag, refining slag has an even lower utilization rate. This is because it contains a large amount of sulfur, has high alkalinity, poor wear resistance, and unstable volume, making it unsuitable for application in the construction industry like blast furnace slag. Furthermore, refining slag has weak oxidation properties, making it impossible to extract and recover iron and iron-containing materials from it. When disposed of in landfills, its high phosphorus and sulfur content causes significant environmental pollution.

[0003] The chemical composition of refining slag is mainly CaO, SiO2, and Al2O3. Many steps in modern metallurgical processes, such as hot metal pretreatment and steelmaking, typically involve adding slag materials with CaO, SiO2, and Al2O3 as their main chemical components to molten steel. The main components of refining slag are similar to some raw materials used in metallurgical production (such as fluxes and slag-forming materials). In summary, returning refining waste to the metallurgical process for reuse can improve the problems of land occupation and environmental pollution caused by refining waste slag. It also has practical significance for conserving metallurgical resources, reducing raw material usage in steel enterprises, and lowering production costs.

[0004] However, refining slag has a high sulfur content, ranging from 1 to 4 wt.%, and the sulfur content fluctuates significantly. During the recycling of this waste slag, the sulfur content in the molten steel may increase, leading to a "sulfur reversion" phenomenon in the steelmaking process, resulting in sulfur enrichment and secondary pollution of the molten steel. Wang Deyong et al. found through thermodynamic calculations that if the sulfur content in the refining waste slag is reduced from 1.8 wt.% to 0.18 wt.%, under otherwise unchanged conditions, the "sulfur capacity" of the refining slag can be increased to approximately 20 times its original value. Therefore, if the sulfur content of the refining waste slag can be reduced to a level comparable to the initial refining slag, i.e., less than 0.2 wt.%, it can be used for recycling in the metallurgical process, such as recovering the refining slag for pelletizing, using it as a slagging agent in steelmaking, and preparing protective slag.

[0005] Hiraki and Kobayashi et al. used a mixed gas of 79% Ar and 21% O2 to desulfurize solid refining slag through high-temperature oxidative calcination at 950-1100℃. Since the sulfur in the refining slag exists not as sulfate but as CaS, it can be oxidized to SO2 at temperatures above 1000℃ and escape. This method achieved a desulfurization rate of approximately 50%, after which the refining slag could be recycled. Allertz et al. conducted high-temperature oxidative roasting of cold refining slag at 1100-1400℃ under pure oxygen conditions. The experiment showed that the desulfurization efficiency gradually increased under completely molten conditions (1400℃), reaching as high as 85% after 1 hour of reaction. However, during the reaction, as the temperature increased, CaS might be oxidized to stable sulfate and adhere to the CaS surface, which could hinder high-temperature oxidative desulfurization to some extent.

[0006] High-temperature oxidation is used to desulfurize molten refining slag, effectively utilizing its waste heat. This technology involves inserting a water-cooled oxygen lance into the slag layer while the slag is in a molten state, oxidizing the sulfur in the slag into gaseous SO2 for removal. While this reduces energy consumption from oxidative regeneration of the slag, the slag layer must reach a required thickness. Excessive thickness worsens the slag's fluidity, leading to uneven mixing and ultimately reducing desulfurization efficiency. Therefore, this process is difficult to operate and control, requiring high temperatures and pure oxygen conditions, resulting in high costs and operational challenges. Ultimately, it increases the burden of slag treatment in the metallurgical industry, making it impractical.

[0007] Uehara et al. conducted hydrothermal leaching experiments on refining slag using two hydrothermal methods to investigate the leaching effect on various components in the slag. The results showed that dissolution and deposition reactions occurred during the leaching process, and the leaching efficiency increased with increasing temperature. The available element calcium in the slag was not lost, and sulfur was effectively removed from the waste slag. He Huanyu studied the removal of sulfur from LF refining slag using hydrothermal leaching. The results showed that when sulfur in the waste slag dissolves into the leachate, it hydrolyzes to form HS. - Then further generate H2S (aq) While selective separation of sulfur is possible, the reaction mechanism using leaching solution dilution is a simple physical process that cannot alter the chemical composition of the slag. Using this method for sulfur recovery in the recycling of refining slag resources will inevitably lead to sulfur enrichment and deterioration of molten steel quality.

[0008] Existing desulfurization methods are mostly high-temperature oxidation and solid-state hydrothermal leaching. While these methods can solve the desulfurization problem of refining slag to a certain extent under laboratory conditions, they are difficult to apply to actual industrial production due to their complex processes, high processing costs, and limitations in large-scale refining slag processing. Therefore, in-depth research into the desulfurization mechanism and the search for a refining slag desulfurization method applicable to actual production are of paramount importance for the recycling and utilization of refining slag, making a significant contribution to environmental protection and the sustainable development of limited resources.

[0009] Patent CN105731895A discloses a method for preparing an alkali-activated high-silica bauxite-based cementitious material with adjustable conductivity. The method involves mixing high-silica bauxite, silica fume, carbon black, and an aqueous solution of sodium silicate in a stirring device, followed by molding and curing to obtain the alkali-activated high-silica bauxite-based semiconductor cementitious material with adjustable conductivity. Specifically, the mass ratio of high-silica bauxite to silica fume is 9:1, and the amounts of sodium silicate nonahydrate, carbon black, and water are 25%, 1.5%–4.5%, and 35%–49% of the sum of the mass of high-silica bauxite and silica fume, respectively. This invention belongs to the field of gel material preparation, utilizing the electrical conductivity of carbon black by adjusting the gel conductivity.

[0010] Patent CN109880971A discloses a method for recycling molten LF furnace refining slag, including the following steps: 1) Slag removal and charging: After normal smelting in the LF furnace, 2-3 consecutive furnaces of LF refining slag and a small amount of molten steel are charged into the desulfurization device; 2) Vacuuming of the ladle; 3) External electric field desulfurization: The cathode is inserted into the molten slag, and a stable electric field is applied externally; 4) SO2 collection: High-temperature SO2 gas enters the SO2 collection device through a pipeline, and the SO2 gas dissolves in the seawater inside the SO2 collection device; 5) Recycling back into the LF furnace. This invention does not consider the differences in slag composition and directly applies an electric field to the refining slag, making it difficult to guarantee a stable desulfurization effect. Summary of the Invention

[0011] 1. The problem to be solved

[0012] To address the problem of low desulfurization rate in existing refining slag desulfurization processes, this invention provides a refining slag desulfurization method based on electric field enhancement. By utilizing the effect of the electric field on the molten metal and slag, and the electrochemical mechanism of the slag-metal reaction, the viscosity and conductivity of the refining slag are adjusted, and appropriate electric field parameters and energizing time are controlled to enhance the directional migration of sulfur, ultimately obtaining low-sulfur refining slag and sulfur-containing molten iron.

[0013] 2. Technical Solution

[0014] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0015] This invention provides a desulfurization method for refining slag based on electric field enhancement, characterized in that:

[0016] S1. Slag Pouring and Mixing: Transfer the refining slag basin to the processing workshop, pour out the slag, add the modifier at the same time, stir and mix well, and control the basicity of the refining slag to 2.0-2.5 and the calcium-aluminum ratio to 3.0-3.5.

[0017] S2. Electric Field Enhancement: Applying a DC electric field between slag and metal to enhance the migration of sulfur into molten iron, specifically in three stages:

[0018] 1) Initially, the voltage is 8-10V, and the power is applied for 3-4 minutes;

[0019] 2) Mid-term: Voltage 4-6V, power on for 10-12 minutes;

[0020] 3) In the later stage, the voltage is 1-3V, and the power is applied for 3-4 minutes.

[0021] S3. Slag Removal: Remove the refining slag from the surface of the molten iron to obtain low-sulfur refining slag and sulfur-containing molten iron. The sulfur content in the low-sulfur refining slag is less than 0.2%.

[0022] Furthermore, in step S1, the specific composition of the refining slag is as follows: CaO: 30%–60%, SiO2: 10%–30%, Al2O3: 10%–30%, MgO: 5%–20%, FeO: 5%–30%, S: 1%–4%, with the balance being unavoidable impurities.

[0023] Furthermore, the modifier is not limited to a specific type; only its effective CaO, SiO2, and Al2O3 content is assessed. When CaO needs to be added, quicklime is preferably used; when SiO2 needs to be added, quartz sand is preferably used; and when Al2O3 needs to be added, bauxite is preferably used. In actual addition, one or more of these modifiers can be selected depending on the situation. Based on the required conductivity and viscosity of the refining slag for electric field enhancement, the basicity of the refining slag is adjusted to 2.0–2.5, and the calcium-aluminum ratio is adjusted to 3.0–3.5. Here, basicity (R) is the mass ratio of calcium oxide to silicon dioxide, and the calcium-aluminum ratio (CA) is the mass ratio of calcium oxide to aluminum oxide. The formula for calculating the amount of modifier added is as follows:

[0024]

[0025] In the formula: To add SiO2 mass, M 渣 For the quality of refining slag, ω CaO R represents the CaO content in the refining slag, and R represents the target alkalinity. This represents the SiO2 content in the refining slag.

[0026]

[0027]

[0028] Where: M CaO The value of CaO added is given by R, which represents the target alkalinity, and CA represents the target calcium-aluminum ratio.

[0029]

[0030] In the formula: To add Al2O3 mass, The value represents the Al2O3 content in the refining slag, and CA represents the calcium-aluminum ratio.

[0031] Controlling the basicity of slag refining is to improve its viscosity. When the basicity is too high, the viscosity of the refining slag is too high, containing a large number of solid particles, which is not conducive to the flow of the refining slag and reduces the actual contact area between the refining slag and the molten steel, thus restricting the migration of sulfur between the slag and the metal. At the same time, the presence of solid particles makes the electric potential distribution between the slag and the metal uneven, resulting in energy waste.

[0032] Controlling the calcium-aluminum ratio in refining slag is to improve its electrical conductivity, as Al2O3 itself will form [AlO4]. 5- The tetrahedral structure deteriorates the conductivity of the slag. When the calcium-to-aluminum ratio is greater than 3.0, excess Ca... 2+ Ions can play a role in charge compensation; as the calcium-aluminum ratio increases, more metal ions and oxygen ions are released from CaO in the slag. Oxygen ions can depolymerize and simplify the complex network structure, thereby improving the conductivity of the slag.

[0033] Therefore, this application controls the basicity of the refining slag to 2.0–2.5 and the calcium-aluminum ratio to 3.0–3.5. These two factors have a synergistic effect. At this basicity, the refining slag has good fluidity, uniform overall composition, and fewer potential low points, thus avoiding ion enrichment and promoting Ca2+ production. 2+ Ions fully utilize their charge compensation function to enhance the electric field's effect on the migration of sulfur, thereby achieving optimal energy utilization efficiency.

[0034] Furthermore, in step S2, the slag mixing involves transferring the refining slag basin to the processing workshop, pouring the refining slag into the molten iron ladle, adding a modifier at the same time, and using the impact force during slag pouring to stir and mix the refining slag and the modifier.

[0035] Furthermore, in step S3, the electric field enhancement involves lowering the electrodes, inserting the anode into the molten slag, and the cathode into the molten iron. Direct current is applied. In the early stage of treatment, the voltage is controlled at 8-10V for 3-4 minutes; in the middle stage, the voltage is controlled at 4-6V for 10-12 minutes; and in the later stage, the voltage is controlled at 1-3V for 3-4 minutes. Under the influence of the electric field, sulfur undergoes directional migration from the refining slag to the molten iron. After the process is complete, the electrodes are raised back to their original positions.

[0036] The electric field enhancement principle is based on an electrochemical mechanism. Molten slag is a conductive melt with an ionic structure. When liquid metals come into contact, charged particles (ions and electrons) transfer between the two phases. Without an applied electric field, the electroneutrality of the two phases is disrupted during this transfer, and excess charge tends to be pushed to the surface. At the slag-metal interface, a charge layer appears on the surface of the liquid metal, with the opposite charge to that on the slag phase surface. This double layer hinders the continued transfer of charged particles. With the application of an electric field, the potential difference between the slag and steel promotes the directional transfer of electrons, the double layer disappears, and the negatively charged S... 2- Under the influence of the electric field, the migration rate is accelerated, which greatly improves the desulfurization efficiency and reaction limit. At the same time, the thermal effect generated by the electric field enhancement process can achieve thermal compensation for the desulfurization process.

[0037] The electric field control is divided into three stages to fully utilize the beneficial effects of electric field enhancement. The sulfur mobility is related to the DC voltage and the electric field enhancement time, as follows: Figure 2-3 As shown, the initial control voltage is 8-10V. The purpose is to use a high voltage to uniformly refine the slag composition and promote the Ca... 2+ Ions rapidly disperse throughout the refining slag, enhancing its responsiveness to the electric field and thus facilitating sulfur migration. The mid-term control voltage is 4-6V to control rapid sulfur removal from the refining slag. Experiments show that, due to Ca… 2+ The highly dispersed ions balanced the potential field around the sulfur element, effectively reducing the binding affinity of the sulfur-containing solid solution to the sulfur element and promoting the ionization of the sulfur element; when the voltage is below 4V, S... 2- The migration rate is too slow, significantly increasing the processing time. When the voltage is higher than 6V, S 2- The occurrence of reverse migration reduces the final desulfurization rate; the voltage is controlled at 1-3V in the later stage to reduce power consumption. When desulfurization is near the end, the migration rate of sulfur is low. Controlling the voltage to 1-3V can meet the voltage requirements of desulfurization and avoid ineffective power consumption.

[0038] Furthermore, in step S4, slag removal is used to separate low-sulfur refining slag from sulfur-containing molten iron. The main components of the obtained low-sulfur refining slag are: CaO: 20%–60%, SiO2: 10%–30%, Al2O3: 10%–30%, MgO: 5%–20%, FeO: 5%–30%. It can be used for slag making in converter smelting, secondary utilization of refining furnaces, and production of high-quality mineral wool. The obtained sulfur-containing molten iron can be reused multiple times to achieve multiple enrichment of sulfur elements, but the maximum sulfur content should not exceed 4.7%, otherwise it will significantly reduce the desulfurization capacity of the refining slag.

[0039] 3. Beneficial effects

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The present invention provides a desulfurization method for refining slag based on electric field enhancement, which divides the electric field enhancement process into three stages, utilizing the electric field to promote Ca... 2+ The ions are highly dispersed, balancing the potential field around the sulfur element, thereby promoting the ionization of the sulfur element from the refining slag to the molten iron, resulting in low-sulfur refining slag and sulfur-containing molten iron, achieving full-scale recovery of the refining slag.

[0042] (2) The present invention provides a method for desulfurizing refining slag based on electric field enhancement. It utilizes the conductivity of the refining slag itself and controls the concentration of free ions in the refining slag by adding a modifier, thereby regulating the conductivity and realizing the hot recovery and utilization of the refining slag. It eliminates the traditional refining slag recovery, cooling, crushing and heating process, fully recovers the heat energy of steel slag, and saves the heat consumption of molten steel (iron) when using refining slag.

[0043] (3) The present invention provides a desulfurization method for refining slag based on electric field enhancement, which can process refining slag very quickly, generally completing the processing of one batch of refining slag in 25 to 35 minutes.

[0044] (4) The desulfurization method of refining slag based on electric field enhancement of the present invention has a simple process flow, no roasting or extraction, low processing cost and large capacity, and does not generate pollutants such as wastewater, waste gas and dust, thus saving resources and being green and environmentally friendly. Attached Figure Description

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0046] Figure 1 SEM-BEI image of refining slag;

[0047] Figure 2 The graph shows the relationship between DC voltage and sulfur mobility.

[0048] Figure 3 This is a graph showing the relationship between electric field enhancement time and sulfur mobility.

[0049] Figure 4 This is a comparison chart showing the processing effects of Comparative Example 1. Detailed Implementation

[0050] The following detailed description of exemplary embodiments of the invention is taken with reference to the accompanying drawings, which form part of the description and illustrate exemplary embodiments in which the invention may be practiced. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from the spirit and scope thereof. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not restrictive of the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0051] Example 1

[0052] The refining slag used in Example 1 was a batch of KR desulfurization refining slag selected by Hebei Yongyang Special Steel Group Co., Ltd. The main components are shown in Table 1. The refining slag weighed 1270 kg. The quicklime, quartz sand, and bauxite used were all metallurgical auxiliary materials procured uniformly by the company. The effective component of the quicklime was CaO, with an effective content of 92.6%; the effective component of the quartz sand was SiO2, with an effective content of 96.3%; and the effective component of the bauxite was Al2O3, with an effective content of 55.8%.

[0053] Table 1-1 Composition of Refining Slag from Example 1, wt%

[0054]

[0055] It includes the following steps:

[0056] S1: Ingredients: Based on the required conductivity and viscosity of the refining slag for electric field enhancement, control the basicity of the refining slag to be 2.0–2.5 and the calcium-aluminum ratio to be 3.0–3.5. Calculate the amount of modifier to be added. The simplified numerical calculation steps are as follows:

[0057] 1) Calculate the existing alkalinity and calcium-aluminum ratio:

[0058] 2) If R > 2.5, CA > 3.5, and the basicity and calcium-aluminum ratio are too high, then add SiO2 and Al2O3;

[0059] 3) The required mass of SiO2 and Al2O3 to be added is:

[0060]

[0061]

[0062] Table 1-2 Specific Calculation Parameters for Example 1

[0063]

[0064] 4) Based on the conversion of effective components, the amount of quartz sand added is 38-110kg, and the amount of bauxite added is 204-263kg. Preferably, the median of the calculation is taken, that is, 74kg of quartz sand and 234kg of bauxite are added.

[0065] S2: Slag Mixing: The refining slag basin is transferred to the processing workshop, which is equipped with an operating room, molten iron ladle, molten iron ladle car, electrode support, electrode anode, electrode cathode, and DC power supply. The processing workshop is equipped with a steel ladle for holding the refining slag, which is transported by a ladle car. The processing workshop is equipped with an electrode support for fixing the electrodes, and the electrode support fixes the cathode and anode respectively. The cathode and anode are immersed in the steel ladle and energized by the DC power supply.

[0066] The molten iron ladle contains a certain mass of molten iron. The mass of molten iron is determined according to the actual situation, and in principle, it should facilitate subsequent slag removal operations. In this embodiment, the mass of molten iron is 96t. The refining slag is poured into the molten iron ladle, and at the same time, quartz sand and bauxite of the calculated mass of S1 are added. The refining slag and modifier are stirred and mixed evenly using the impact force during slag pouring.

[0067] S3: Electric Field Enhancement: The electrode support is lowered, the anode is inserted into the molten slag, and the cathode is inserted into the molten iron. Under the influence of the electric field, sulfur migrates directionally from the refining slag to the molten iron. After completion, the electrode is raised back to its original position. Electric field enhancement is specifically divided into three stages:

[0068] 1) Initially, the voltage was 9V, and the power was applied for 4 minutes;

[0069] 2) Mid-term, voltage 5V, power on for 12 minutes;

[0070] 3) Later, the voltage is 2V, and the power is applied for 3 minutes.

[0071] S4: Slag Removal: Separating low-sulfur refining slag from sulfur-containing molten iron. In this embodiment, the sulfur content of the refining slag is reduced to 0.12% after treatment, and the desulfurization rate reaches 91.8%; the sulfur content of the molten iron is increased from 0.89% to 1.33%, and the refining slag can continue to be desulfurized.

[0072] The main components of the obtained low-sulfur refining slag are: CaO: 47.43%, SiO2: 21.98%, Al2O3: 15.21%, MgO: 6.77%, FeO: 5.42%, S: 0.12%, and its electron micrograph is shown below. Figure 1 As shown, it can be used for slag making in converter smelting, secondary utilization in refining furnaces, and production of high-quality mineral wool; the resulting sulfur-containing molten iron can be used multiple times to achieve multiple enrichment of sulfur elements, but the maximum sulfur content should not exceed 4.7%, otherwise it will significantly reduce the desulfurization capacity of refining slag.

[0073] Example 2

[0074] The refining slag used in Example 2 was a batch of LF refining slag selected by Hebei Yongyang Special Steel Group Co., Ltd. The main components are shown in Table 2. The mass of the refining slag was 1473 kg. The lime, quartz sand, and bauxite used were all metallurgical auxiliary materials procured uniformly by the company. The effective component of the lime was CaO, with an effective content of 92.6%; the effective component of the quartz sand was SiO2, with an effective content of 96.3%; and the effective component of the bauxite was Al2O3, with an effective content of 55.8%.

[0075] Table 2-1 Composition of Refining Slag from Example 2 (wt%)

[0076]

[0077] It includes the following steps:

[0078] S1: Ingredients: Based on the requirements of conductivity and viscosity of the refining slag for electric field enhancement, control the basicity of the refining slag to 2.0-2.5 and the calcium-aluminum ratio to 3.0-3.5. Calculate the amount of modifier to be added as 138 kg of limestone.

[0079] 1) Calculate the existing alkalinity and calcium-aluminum ratio:

[0080] 2) If R < 2.5, CA < 3.5, and the basicity and calcium-aluminum ratio are too low, add CaO;

[0081] 3) The required amount of CaO to be added is:

[0082]

[0083]

[0084] Table 2-2 Specific Calculation Parameters for Example 2

[0085]

[0086] 4) In order to simultaneously meet the requirements of alkalinity and calcium-aluminum ratio, the preferred addition of CaO is 128 kg. Based on the conversion of effective lime components, the addition of lime is 138 kg, so that it can simultaneously meet the requirements of refining slag alkalinity of 2.0-2.5 and calcium-aluminum ratio of 3.0-3.5.

[0087] S2: Slag Pouring and Mixing: The refining slag basin is transferred to the processing workshop, which is equipped with an operating room, molten iron ladle, molten iron ladle car, electrode support, electrode anode, electrode cathode, and DC power supply. The molten iron in the ladle has a mass of 98t. The refining slag is poured into the molten iron ladle, and at the same time, the quartz sand and limestone calculated in S1 are added. The refining slag and modifier are mixed evenly using the impact force during slag pouring.

[0088] S3: Electric Field Enhancement: The electrode support is lowered, the anode is inserted into the molten slag, and the cathode is inserted into the molten iron. Under the influence of the electric field, sulfur migrates directionally from the refining slag to the molten iron. After completion, the electrode is raised back to its original position. Electric field enhancement is specifically divided into three stages:

[0089] 1) Initially, the voltage was 9V, and the power was applied for 4 minutes;

[0090] 2) Mid-term, voltage 5V, power on for 12 minutes;

[0091] 3) Later, the voltage is 2V, and the power is applied for 3 minutes.

[0092] S4: Slag Removal: Separating low-sulfur refining slag from sulfur-containing molten iron. In this embodiment, the sulfur content of the refining slag is reduced to 0.08% after treatment, and the desulfurization rate reaches 90.7%; the sulfur content of the molten iron is increased from 1.46% to 1.77%, and the refining slag can continue to be desulfurized.

[0093] The main components of the obtained low-sulfur refining slag are CaO: 44.38%, SiO2: 19.72%, Al2O3: 13.67%, MgO: 10.34%, FeO: 8.21%, and S: 0.08%. It can be used for slag making in converter smelting, secondary utilization in refining furnaces, and production of high-quality mineral wool. The obtained sulfur-containing molten iron can be reused multiple times to achieve multiple enrichment of sulfur elements, but the maximum sulfur content should not exceed 4.7%, otherwise it will significantly reduce the desulfurization capacity of the refining slag.

[0094] Example 3

[0095] The refining slag used in Example 3 was a batch of KR desulfurization refining slag selected by Anhui Changjiang Iron & Steel Co., Ltd. The main components are shown in Table 3. The mass of the refining slag was 1860 kg. The quicklime and bauxite used were metallurgical auxiliary materials procured uniformly by the company. The effective component of the limestone was CaO, with an effective content of 94.3%; the effective component of the bauxite was Al2O3, with an effective content of 52.7%. The SiO2-containing material used was crushed glass, purchased from the Ma'anshan Waste Material Recycling Center, with an SiO2 content of 98.7%.

[0096] Table 3-1 Composition of Refining Slag from Example 3 (wt%)

[0097]

[0098] S1: Ingredients: Based on the requirements of conductivity and viscosity of the refining slag for electric field enhancement, control the basicity of the refining slag to be 2.0-2.5 and the calcium-aluminum ratio to be 3.0-3.5. Calculate the amount of modifier to be added as 122 kg of crushed glass and 333 kg of bauxite.

[0099] 1) Calculate the existing alkalinity and calcium-aluminum ratio:

[0100] 2) If R > 2.5, CA > 3.5, and the basicity and calcium-aluminum ratio are too high, then add SiO2 and Al2O3;

[0101] 3) The required mass of SiO2 and Al2O3 is:

[0102]

[0103]

[0104] Table 3-2 Specific Calculation Parameters for Example 3

[0105]

[0106] 4) Based on the conversion of effective ingredients, the amount of crushed glass added is 71-172 kg, and the amount of bauxite added is 288-378 kg. Preferably, 122 kg of crushed glass and 333 kg of bauxite are added.

[0107] S2: Slag Pouring and Mixing: The refining slag basin is transferred to the processing workshop, which is equipped with an operating room, molten iron ladle, molten iron car, electrode support, electrode anode, electrode cathode, and DC power supply. The molten iron in the ladle has a mass of 124t. The refining slag is poured into the molten iron ladle, and at the same time, quartz sand and limestone of the calculated mass in S1 are added. The refining slag and modifier are mixed evenly using the impact force during slag pouring.

[0108] S3: Electric Field Enhancement: The electrode support is lowered, the anode is inserted into the molten slag, and the cathode is inserted into the molten iron. Under the influence of the electric field, sulfur migrates directionally from the refining slag to the molten iron. After completion, the electrode is raised back to its original position. Electric field enhancement is specifically divided into three stages:

[0109] 1) Initially, the voltage is 10V, and the power is applied for 4 minutes;

[0110] 2) Mid-term, voltage 6V, power on for 12 minutes;

[0111] 3) Later, the voltage was 2V and the power was applied for 4 minutes.

[0112] S4: Slag Removal: Separating low-sulfur refining slag from sulfur-containing molten iron. In this embodiment, the sulfur content of the refining slag is reduced to 0.15% after treatment, and the desulfurization rate reaches 92.5%; the sulfur content of the molten iron is increased from 1.76% to 2.34%, and the refining slag can continue to be desulfurized.

[0113] The main components of the obtained low-sulfur refining slag are CaO: 46.33%, SiO2: 20.59%, Al2O3: 14.12%, MgO: 5.73%, FeO: 9.84%, and S: 0.15%. It can be used for slag making in converter smelting, secondary utilization in refining furnaces, and production of high-quality mineral wool. The obtained sulfur-containing molten iron can be reused multiple times to achieve multiple enrichment of sulfur elements, but the maximum sulfur content should not exceed 4.7%, otherwise it will significantly reduce the desulfurization capacity of the refining slag.

[0114] Comparative Example 1

[0115] To verify the effectiveness of the modification process and staged electric field enhancement of this invention, industrial experiments were conducted based on the existing process conditions of Anhui Changjiang Iron & Steel Co., Ltd. Using the method of this invention as the basic experimental procedure, Group A was conducted under the following conditions: no modification and no staged electric field enhancement; Group B was conducted under the following conditions: modification and no staged electric field enhancement; Group C was conducted under the following conditions: no modification and staged electric field enhancement; and Group D was conducted under the following conditions: modification and staged electric field enhancement. Three heat cycles were conducted for each group, and the desulfurization rate and power consumption were compared. Figure 4 As shown, the specific values ​​are shown in Table 4:

[0116] Table 4 Comparison of Desulfurization Rate and Power Consumption Results

[0117]

[0118] The comparison shows that the desulfurization efficiency of refining slag without modification and without staged electric field enhancement is low and the power consumption is high. After refining slag modification and staged electric field enhancement treatment, the desulfurization rate of refining slag is significantly improved and the power consumption is reduced to a certain extent.

[0119] Comparative Example 2

[0120] Anhui Changjiang Iron & Steel Co., Ltd. has a method for desulfurization of refining slag by carbonation. The method includes the following steps: First, the refining slag is ground into fine powder, and the ground slag is thoroughly mixed with water at a solid-liquid ratio of 1:5-1:20 and stirred. Second, a carbonation reaction is carried out. The reaction pressure is atmospheric pressure, and the stirring degree is required to ensure that there is no sediment at the bottom of the container. Third, after the carbonation reaction, the suspension is filtered, the filter residue is washed with water and dried to obtain a low-sulfur refining slag.

[0121] To compare the beneficial effects of this invention, 10 batches of continuously produced refining slag were selected, and desulfurization was performed alternately using existing methods and this method. The desulfurization rate, treatment cost, and treatment time were compared as follows:

[0122] Table 410 Desulfurization rate, treatment cost, and treatment time of furnace refining slag

[0123]

[0124] Existing methods include cooling, crushing, fine grinding, and carbonation. The processing steps are cumbersome, waste the residual heat of the refining slag, and the statistical processing time is only the time required for carbonation. The total process time is about 16 to 24 hours. Carbonation is limited by solid-liquid reaction, and the average desulfurization rate is only 63.3%. The average processing cost is 268.6 yuan.

[0125] This method involves direct hot desulfurization and recovery of refining slag. The process is simple, with an average desulfurization rate of up to 91.7%, which is 28.4% higher than existing methods. The average cost is 79.8 yuan, which is 188.8 yuan lower than existing methods. The average processing time is 30.4 min, which is 10.8 min lower than existing methods, demonstrating significant benefits.

Claims

1. A desulfurization method for refining slag based on electric field enhancement, characterized in that, Including the following steps: S1. Slag mixing: Add modifier to refining slag, stir and mix well, and control the basicity of refining slag to 2.0~2.5 and the calcium-aluminum ratio to 3.0~3.5; S2, Electric Field Enhancement: A DC electric field is applied between the slag and metal. The electric field is divided into three stages: 1) Initially, the voltage is 8-10V, and the power is applied for 3-4 minutes; 2) Mid-term: Voltage 4-6V, power on for 10-12 minutes; 3) In the later stage, the voltage is 1-3V, and the power is applied for 3-4 minutes; S3. Slag Removal: Remove the refining slag from the surface of the molten iron to obtain low-sulfur refining slag and sulfur-containing molten iron.

2. The desulfurization method for refining slag according to claim 1, characterized in that, In step S1, the refining slag comprises, by mass percentage: CaO: 30%~60%, SiO2: 10%~30%, Al2O3: 10%~30%, and MgO: 5%~20%.

3. The desulfurization method for refining slag according to claim 1, characterized in that, In step S1, the modifier comprises one of CaO, SiO2, and Al2O3.

4. The desulfurization method for refining slag according to claim 3, characterized in that, When a modifier containing SiO2 is added, the amount of SiO2 added must satisfy the following: In the formula: To join quality, For the quality of refining slag, For refining slag content, For the target alkalinity, For refining slag content.

5. The desulfurization method for refining slag according to claim 3, characterized in that, When a modifier containing CaO is added, the amount of CaO added must satisfy the following conditions: In the formula: To join Mass, R is the target alkalinity, For the target calcium-aluminum ratio, For the quality of refining slag, For refining slag content, For refining slag content, For refining slag content.

6. The desulfurization method for refining slag according to claim 3, characterized in that, When a modifier containing Al2O3 is added, the amount of Al2O3 added must satisfy the following conditions: In the formula: To join quality, For refining slag Content, CA is the target calcium-aluminum ratio, For the quality of refining slag, For refining slag content.

7. The desulfurization method for refining slag according to any one of claims 1-6, characterized in that, The sulfur content in the low-sulfur refining slag obtained in step S3 is less than 0.2 wt%.

Images