Method for reducing freezing layer of dilution electric furnace

Abstract

The invention discloses a method for controlling a freezing layer of a nickel dilution electric furnace by using a hot vulcanizing agent, which belongs to the technical field of nonferrous metallurgy and can reduce the height of the freezing layer of the nickel dilution electric furnace, improve the effective volume of a hearth of the nickel dilution electric furnace and complete the functions of reinforcing vulcanization, reducing dilution and settling separation in the nickel dilution electric furnace. And the height of a freezing layer is reduced, the production cost is saved, the operation safety of the furnace body is ensured, and the discharge operation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgical technology and relates to a method for reducing the freezing layer in a depleted electric furnace. Background Technology

[0002] Currently, in the nickel pyrometallurgical process, the control of the frozen layer in the depleted electric furnace is unstable. This can cause the frozen layer to rise rapidly in a short period of time, reducing the effective volume of the furnace and making it difficult to discharge materials from the furnace. A large amount of high-melting-point refractory materials are deposited in the frozen layer at the bottom of the furnace, causing the furnace to shut down. This makes maintenance difficult and time-consuming. Therefore, it is necessary to control the height of the frozen layer to ensure the stable operation of the metallurgical furnace. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the prior art by providing a method for reducing the freezing layer in a leaning electric furnace. This method can enhance the leaning and settling functions in a leaning electric furnace, reduce the height of the freezing layer, and solve the problems of unstable control of the freezing layer in a leaning electric furnace, which leads to the deposition of a large amount of high-melting-point refractory materials in the freezing layer at the bottom of the furnace, causing furnace failure and making maintenance difficult.

[0004] Therefore, the present invention adopts the following technical solution: A method for reducing the freezing layer in a lean electric furnace includes the following steps: Step 1: Mix the smelting slag, blowing slag, sulfiding agent, reducing agent, quartz, and high-sulfur concentrate according to the set ratio to obtain a mixture that meets the process requirements; by adding materials in different proportions, ensure that the sulfiding agent and reducing agent are fully mixed with the smelting slag / blowing slag to complete the physicochemical reaction.

[0005] The smelting slag mentioned in step 1 is nickel-copper smelting slag. The smelting slag / blowing slag, sulfiding agent, and reducing agent are mixed in a ratio of (60-30):(10-5):(2-1). If the freezing layer of the depleted electric furnace is too high, the high-sulfur concentrate, sulfiding agent, and reducing agent are mixed in a ratio of (3-5):(15-20):(2.5-3.5) and added to the melt. The reducing agent is one or more of the carbonaceous reducing agents such as lump coal, coke, and semi-coke. It is added from the top of the furnace to ensure the heat of the molten pool and the reducing atmosphere in the upper part.

[0006] The smelting slag / blowing slag mentioned in step 1 includes the following component mass fraction requirements: Ni 0.5%~2%, Cu 0.5%~1%, Fe 44%~50%, S 0.5%~1.5%, SiO2 28%~35%, with the remainder being unavoidable impurities; or the iron-silicon ratio is controlled at 1.4~1.8.

[0007] The vulcanizing agent mentioned in step 1 comprises the following components by weight percentage: Ni 7%–8%, Cu 5%–7%, Fe 33%–37%, S 25%–28%, SiO 26%–9%, ​​MgO 5%–7%, with the remainder being unavoidable impurities.

[0008] The reducing agent mentioned in step 1 includes a carbonaceous reducing agent, which has the following component requirements: average volatile matter content ≤20%, ash content ≤20%, fixed carbon content ≥50%, and particle size 30-50mm.

[0009] The high-sulfur concentrate mentioned in step 1 has the following composition requirements: Fe content ≥ 40% and S content ≥ 36%. Specifically, the high-sulfur concentrate has good miscibility with slag and can fully sulfide-reduce the valuable metal oxides in the converter slag. Fe3O4 is reduced to FeO and reacts with SiO2 to form stable Fe2SiO4 with a low melting point, thereby reducing the freezing layer at the bottom of the furnace.

[0010] In step 1, the sulfiding agent has the following requirements: when the freezing layer inside the furnace is high, it is necessary to fully ensure the separation of molten slag and matte inside the furnace and ensure that refractory materials are discharged smoothly out of the furnace. It is necessary to control the sulfur-iron ratio of the sulfiding agent to exceed 1.2.

[0011] Step 2: Add the mixture into the depletion electric furnace, with the melt surface height being 1400mm to 2000mm. The slag temperature of the depletion electric furnace is controlled at 1200 to 1350℃ (electricity consumption per ton of slag), the nickel matte temperature is controlled at 1000 to 1200℃, and the low-nickel matte grade is controlled at 20% to 40%.

[0012] In step 2, the slag surface is maintained at 1400mm to 2000mm, which includes the upper slag layer and the lower nickel matte layer. By controlling the height of the melt surface, the heat storage capacity of the melt is ensured, thereby carrying the refractory material on the frozen layer out of the furnace, reducing the amount of refractory material adhering to the frozen layer, and thus lowering the frozen layer.

[0013] Step 2 involves controlling the slag temperature in the lean electric furnace by adjusting the electrode load and electrode voltage level. The power consumption per ton of slag should not be less than 130 kWh / t, and the voltage level should be controlled between levels 4 and 9. The temperature of the melt inside the furnace is increased by increasing power consumption. The temperature of the melt is adjusted by adjusting the insertion depth of the electrodes. The high-temperature melt dissolves the high-melting-point substances on the frozen layer, thereby reducing the thickness of the frozen layer.

[0014] In step 2, the low-nickel matte grade in the depleted electric furnace is controlled by adjusting the feed material ratio to ensure that the Fe and S content in the low-nickel matte is 38-45% and 19-26%, respectively.

[0015] Step 3: Hot sulfurizing agent is returned to the lean electric furnace to enhance the interaction reaction of the slag layer, promote the increase of temperature, sulfur and viscosity of the nickel matte layer, and intensify the penetration, dissolution and scouring of the frozen layer in the hearth. It is also returned to the slag in the later stage of converter blowing.

[0016] In step 3, the reduction reaction occurs when the reducing agent, freshly introduced into the furnace, accumulates on the surface of the melt and reacts with the metal oxides in the surface melt. Fe3O4 + C = 3FeO + CO FeO + C = Fe + CO In converter slag, some metal oxides are reduced by Fe to metals such as Cu, Ni, and Co, which then form alloy phases with metallic iron. These alloy phases appear as metal particles in the slag and, after thermal clarification and analysis, settle and polymerize into the matte layer. The reaction formula is as follows: M ˊ O + Fe = M ′ +FeO M ˊ +Fe=M ˊ -Fe (alloy) The reducing agent reduces the refractory Fe3O4 in the melt, thus reducing its adhesion to the frozen layer. However, if the amount of reducing agent added is too large or the amount of sulfide is insufficient, it will lead to over-reduction, an increase in the metal phase, and the enriched metal phase will cause metal phase deposition, resulting in an increase in the melting point. At the operating temperature of 1050-1150℃, a severe runaway rise in the frozen layer will occur, and the melt will stick to the chute during discharge, making discharge difficult.

[0017] In step 3, the interaction reaction refers to the interaction reaction between the valuable metal oxide and FeS in the matte phase, forming a valuable metal sulfide that enters the matte phase. Cu₂O + FeS = Cu₂S + FeO NiO + FeS = NiS + FeO CoO + FeS = CoS + FeO In step 3, the metal sulfidation reaction refers to the sulfidation reaction of valuable metals in the metallic phase. 2Cu + FeS = Cu₂S + Fe Ni + FeS = NiS + Fe.

[0018] Step 4: After the reduction and separation of smelting slag and metal are completed, the depleted slag is discharged out of the furnace through the slag outlet. The depleted low-nickel matte is sent to the converter for secondary blowing to obtain high-nickel matte rich in valuable metals. If the discharge is not smooth, the burner is forcibly cleared and the discharge is continuous to ensure that the slag containing high melting point substances is discharged.

[0019] In step 4, if the sulfiding agent is insufficient, and there is discharge at the furnace front, the generated cobalt matte will be continuously reduced near the reducing agent and electrodes, increasing the amount of high-melting-point nickel-iron alloy components and further affecting the discharge at the furnace front. Hot low-nickel matte is returned to the inside of the depleted electric furnace, and the melt with poor discharge at the furnace front under the high freezing layer is carried out by the low-nickel matte, ensuring smooth discharge at the furnace front of the depleted electric furnace, reducing the accumulation of high-melting-point substances in the furnace, and thus reducing the freezing layer.

[0020] The composition of the low-nickel matte returned to the furnace by weight percentage is: Ni 23%–27%, Cu 15%–19%, Fe 26%–30%, Co 0.3%–0.6%, S 25%–28%, with the remainder being unavoidable impurities.

[0021] In step 4, hot sulfiding agent is returned to the inside of the lean electric furnace, and converter slag from the later stage is returned simultaneously. The composition of the converter slag from the early stage by weight percentage is: Ni 0.73%–0.75%, Cu 0.55%–0.90%, Fe 46%–49%, S 0.65%–0.92%, with the remainder being unavoidable impurities. The composition of the converter slag from the later stage by weight percentage is: Ni 0.77%–0.89%, Cu 0.55%–0.65%, Fe 48%–51%, S 0.65%–1.2%, with the remainder being unavoidable impurities.

[0022] When completing the reduction separation of smelting slag and metal in step 4, it is necessary to ensure the depletion and clarification separation time in the furnace to ensure that the slag and low-nickel matte are fully separated.

[0023] The beneficial effects of this invention are as follows: This invention can significantly reduce the height of the frozen layer in non-ferrous metal furnaces and increase the effective volume of the furnace. By completing the functions of depletion and settling in a single enhanced depletion electric furnace, the height of the frozen layer is reduced, production costs are saved, and smelting safety is further improved. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be described below with reference to the accompanying drawings and implementation methods.

[0026] like Figure 1 As shown, a method for reducing the freezing layer in a lean electric furnace includes the following steps: Step 1: Mix the smelting slag, blowing slag, sulfiding agent, reducing agent, quartz, and high-sulfur concentrate according to the set ratio to obtain a mixture that meets the process requirements; by adding materials in different proportions, ensure that the sulfiding agent and reducing agent are fully mixed with the smelting slag / blowing slag to complete the physicochemical reaction.

[0027] The smelting slag mentioned in step 1 is nickel-copper smelting slag. The smelting slag / blowing slag, sulfiding agent, and reducing agent are mixed in a ratio of (60-30):(10-5):(2-1). If the freezing layer of the depleted electric furnace is too high, the high-sulfur concentrate, sulfiding agent, and reducing agent are mixed in a ratio of (3-5):(15-20):(2.5-3.5) and added to the melt. The reducing agent is one or more of the carbonaceous reducing agents such as lump coal, coke, and semi-coke. It is added from the top of the furnace to ensure the heat of the molten pool and the reducing atmosphere in the upper part.

[0028] The smelting slag / blowing slag mentioned in step 1 includes the following component mass fraction requirements: Ni 0.5%~2%, Cu 0.5%~1%, Fe 44%~50%, S 0.5%~1.5%, SiO2 28%~35%, with the remainder being unavoidable impurities; or the iron-silicon ratio is controlled at 1.4~1.8.

[0029] The vulcanizing agent mentioned in step 1 comprises the following components by weight percentage: Ni 7%–8%, Cu 5%–7%, Fe 33%–37%, S 25%–28%, SiO 26%–9%, ​​MgO 5%–7%, with the remainder being unavoidable impurities.

[0030] The reducing agent mentioned in step 1 includes a carbonaceous reducing agent, which has the following component requirements: average volatile matter content ≤20%, ash content ≤20%, fixed carbon content ≥50%, and particle size 30-50mm.

[0031] The high-sulfur concentrate mentioned in step 1 has the following composition requirements: Fe content ≥ 40% and S content ≥ 36%. Specifically, the high-sulfur concentrate has good miscibility with slag and can fully sulfide-reduce the valuable metal oxides in the converter slag. Fe3O4 is reduced to FeO and reacts with SiO2 to form stable Fe2SiO4 with a low melting point, thereby reducing the freezing layer at the bottom of the furnace.

[0032] In step 1, the sulfiding agent has the following requirements: when the freezing layer inside the furnace is high, it is necessary to fully ensure the separation of molten slag and matte inside the furnace and ensure that refractory materials are discharged smoothly out of the furnace. It is necessary to control the sulfur-iron ratio of the sulfiding agent to exceed 1.2.

[0033] Step 2: Add the mixture into the depletion electric furnace, with the melt surface height being 1400mm to 2000mm. The slag temperature of the depletion electric furnace is controlled at 1200 to 1350℃ (electricity consumption per ton of slag), the nickel matte temperature is controlled at 1000 to 1200℃, and the low-nickel matte grade is controlled at 20% to 40%.

[0034] In step 2, the slag surface is maintained at 1400mm to 2000mm, which includes the upper slag layer and the lower nickel matte layer. By controlling the height of the melt surface, the heat storage capacity of the melt is ensured, thereby carrying the refractory material on the frozen layer out of the furnace, reducing the amount of refractory material adhering to the frozen layer, and thus lowering the frozen layer.

[0035] Step 2 involves controlling the slag temperature in the lean electric furnace by adjusting the electrode load and electrode voltage level. The power consumption per ton of slag should not be less than 130 kWh / t, and the voltage level should be controlled between levels 4 and 9. The temperature of the melt inside the furnace is increased by increasing power consumption. The temperature of the melt is adjusted by adjusting the insertion depth of the electrodes. The high-temperature melt dissolves the high-melting-point substances on the frozen layer, thereby reducing the thickness of the frozen layer.

[0036] In step 2, the low-nickel matte grade in the depleted electric furnace is controlled by adjusting the feed material ratio to ensure that the Fe and S content in the low-nickel matte is 38-45% and 19-26%, respectively.

[0037] Step 3: Hot sulfurizing agent is returned to the lean electric furnace to enhance the interaction reaction of the slag layer, promote the increase of temperature, sulfur and viscosity of the nickel matte layer, and intensify the penetration, dissolution and scouring of the frozen layer in the hearth. It is also returned to the slag in the later stage of converter blowing.

[0038] In step 3, the reduction reaction occurs when the reducing agent, freshly introduced into the furnace, accumulates on the surface of the melt and reacts with the metal oxides in the surface melt. Fe3O4 + C = 3FeO + CO FeO + C = Fe + CO In converter slag, some metal oxides are reduced by Fe to metals such as Cu, Ni, and Co, which then form alloy phases with metallic iron. These alloy phases appear as metal particles in the slag and, after thermal clarification and analysis, settle and polymerize into the matte layer. The reaction formula is as follows: M ˊ O + Fe = M ′ +FeO M ˊ +Fe=M ˊ -Fe (alloy) The reducing agent reduces the refractory Fe3O4 in the melt, thus reducing its adhesion to the frozen layer. However, if the amount of reducing agent added is too large or the amount of sulfide is insufficient, it will lead to over-reduction, an increase in the metal phase, and the enriched metal phase will cause metal phase deposition, resulting in an increase in the melting point. At the operating temperature of 1050-1150℃, a severe runaway rise in the frozen layer will occur, and the melt will stick to the chute during discharge, making discharge difficult.

[0039] In step 3, the interaction reaction refers to the interaction reaction between the valuable metal oxide and FeS in the matte phase, forming a valuable metal sulfide that enters the matte phase. Cu₂O + FeS = Cu₂S + FeO NiO + FeS = NiS + FeO CoO + FeS = CoS + FeO In step 3, the metal sulfidation reaction refers to the sulfidation reaction of valuable metals in the metallic phase. 2Cu + FeS = Cu₂S + Fe Ni + FeS = NiS + Fe.

[0040] Step 4: After the reduction and separation of smelting slag and metal are completed, the depleted slag is discharged out of the furnace through the slag outlet. The depleted low-nickel matte is sent to the converter for secondary blowing to obtain high-nickel matte rich in valuable metals. If the discharge is not smooth, the burner is forcibly cleared and the discharge is continuous to ensure that the slag containing high melting point substances is discharged.

[0041] In step 4, if the sulfiding agent is insufficient, and there is discharge at the furnace front, the generated cobalt matte will be continuously reduced near the reducing agent and electrodes, increasing the amount of high-melting-point nickel-iron alloy components and further affecting the discharge at the furnace front. Hot low-nickel matte is returned to the inside of the depleted electric furnace, and the melt with poor discharge at the furnace front under the high freezing layer is carried out by the low-nickel matte, ensuring smooth discharge at the furnace front of the depleted electric furnace, reducing the accumulation of high-melting-point substances in the furnace, and thus reducing the freezing layer.

[0042] The composition of the low-nickel matte returned to the furnace by weight percentage is: Ni 23%–27%, Cu 15%–19%, Fe 26%–30%, Co 0.3%–0.6%, S 25%–28%, with the remainder being unavoidable impurities.

[0043] In step 4, hot sulfiding agent is returned to the inside of the lean electric furnace, and converter slag from the later stage is returned simultaneously. The composition of the converter slag from the early stage by weight percentage is: Ni 0.73%–0.75%, Cu 0.55%–0.90%, Fe 46%–49%, S 0.65%–0.92%, with the remainder being unavoidable impurities. The composition of the converter slag from the later stage by weight percentage is: Ni 0.77%–0.89%, Cu 0.55%–0.65%, Fe 48%–51%, S 0.65%–1.2%, with the remainder being unavoidable impurities.

[0044] When completing the reduction separation of smelting slag and metal in step 4, it is necessary to ensure the depletion and clarification separation time in the furnace to ensure that the slag and low-nickel matte are fully separated.

Claims

1. A method for reducing the freezing layer in a lean electric furnace, characterized in that, Includes the following steps: Step 1: Mix the smelting slag, blowing slag, sulfiding agent, reducing agent, quartz, and high-sulfur concentrate according to the set ratio to obtain a mixture. Step 2: Add the mixture into the depletion furnace, control the melt height to 1400mm-2000mm, control the slag temperature to 1200-1350℃, control the nickel matte temperature to 1000-1200℃, and control the low-nickel matte grade to 20-40%. Step 3: Hot sulfiding agent is returned to the lean electric furnace. After the sulfiding agent, reducing agent and converter slag are fully mixed, reduction reaction, cross reaction and metal sulfidation reaction occur. The reduction reaction refers to the reduction of some metal oxides in converter slag by Fe into metals Cu, Ni, and Co, which then form an alloy phase with metallic iron. These metal particles appear in the slag and, after thermal clarification and analysis, settle and polymerize into the matte layer. The interaction reaction refers to the interaction between valuable metal oxides and FeS in the matte phase, forming valuable metal sulfides that enter the matte phase. (Basic reaction:) Metal sulfidation refers to the sulfidation reaction of valuable metals in a metallic phase; Step 4: After the reduction and separation of smelting slag and metal are completed, the depleted slag is discharged out of the furnace through the slag outlet. The depleted low-nickel matte is sent to the converter for secondary blowing to obtain high-nickel matte rich in valuable metals. If the discharge is not smooth, the burner is forcibly cleared and the discharge is continuous to ensure that the slag containing high melting point substances is discharged.

2. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The smelting slag mentioned in step 1 is nickel-copper smelting slag. The smelting slag / blowing slag, sulfiding agent, and reducing agent are mixed in a ratio of (60-30):(10-5):(2-1). If the freezing layer of the depleted electric furnace is too high, the high-sulfur concentrate, sulfiding agent, and reducing agent are mixed in a ratio of (3-5):(15-20):(2.5-3.5) and added to the melt. The reducing agent is one or more carbonaceous reducing agents such as lump coal, coke, and semi-coke, and is added from the top of the furnace to ensure the heat of the molten pool and the reducing atmosphere in the upper part.

3. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The smelting slag / blowing slag in step 1 includes the following component mass fraction requirements: Ni 0.5%~2%, Cu 0.5%~1%, Fe 44%~50%, S 0.5%~1.5%, SiO2 28%~35%, with the remainder being unavoidable impurities; or the iron-silicon ratio is controlled at 1.4~1.

8.

4. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The vulcanizing agent in step 1 comprises the following components by weight percentage: Ni 7%–8%, Cu 5%–7%, Fe 33%–37%, S 25%–28%, SiO 26%–9%, ​​MgO 5%–7%, with the remainder being unavoidable impurities.

5. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The reducing agent in step 1 is mainly a carbonaceous reducing agent, and includes the following component requirements: average volatile matter content ≤20%, ash content ≤20%, fixed carbon content ≥50%, and particle size 30-50mm.

6. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The high-sulfur concentrate mentioned in step 1 has the following composition requirements: Fe content ≥ 40% and S content ≥ 36%. Specifically, the high-sulfur concentrate has good miscibility with slag and can fully sulfide-reduce the valuable metal oxides in the converter slag. Fe3O4 is reduced to FeO and reacts with SiO2 to form stable Fe2SiO4 with a low melting point, thereby reducing the freezing layer at the bottom of the furnace.

7. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, In step 1, the sulfiding agent has the following requirements: when the freezing layer inside the furnace is high, it is necessary to fully ensure the separation of molten slag and matte inside the furnace and ensure that refractory materials are discharged smoothly out of the furnace. It is necessary to control the sulfur-iron ratio of the sulfiding agent to exceed 1.

2.

8. The method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, In step 2, the slag surface is maintained at 1400mm to 2000mm; The temperature control of slag in the lean electric furnace is mainly based on the adjustment of electrode load and electrode voltage level. The power consumption per ton of slag is not less than 130 kWh / t, and the voltage level is controlled between level 4 and level 9. In the low-nickel matte, the content of Fe and S elements accounts for 38-45% and 19-26%, respectively.

9. A method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, In step 3, the reduction reaction refers to the reduction reaction that occurs when the reducing agent, which has just entered the furnace, accumulates on the surface of the melt and reacts with the metal oxides in the surface melt. Fe3O4 + C = 3FeO + CO FeO + C = Fe + CO In converter slag, some metal oxides are reduced by Fe to metals such as Cu, Ni, and Co, which then form alloy phases with metallic iron. These alloy phases appear as metal particles in the slag and, after thermal clarification and analysis, settle and polymerize into the matte layer. The reaction formula is as follows: M ˊ O+Fe=M ′ +FeO M ˊ +Fe=M ˊ -Fe (alloy) The interaction reaction refers to the interaction between valuable metal oxides and FeS in the matte phase, forming valuable metal sulfides that enter the matte phase. (Basic reaction:) Cu₂O + FeS = Cu₂S + FeO NiO + FeS = NiS + FeO CoO + FeS = CoS + FeO Metal sulfidation refers to the sulfidation reaction of valuable metals in a metallic phase. 2Cu + FeS = Cu₂S + Fe Ni + FeS = NiS + Fe.

10. A method for reducing the freezing layer in a lean electric furnace according to claim 1, characterized in that, The low-nickel matte returned to the furnace in step 4 has the following composition by weight percentage: Ni 23%–27%, Cu 15%–19%, Fe 26%–30%, Co 0.3%–0.6%, S 25%–28%, with the remainder being unavoidable impurities. Hot sulfiding agent is returned to the inside of the lean electric furnace, and the late-stage converter slag is returned simultaneously; the weight percentage composition of the early-stage converter slag is: Ni 0.73%~0.75%, Cu 0.55%~0.90%, Fe 46%~49%, S 0.65%~0.92%; The composition of the slag in the later stage of converter is as follows by weight percentage: Ni 0.77%~0.89%, Cu 0.55%~0.65%, Fe 48%~51%, S 0.65%~1.2%, with the remainder being unavoidable impurities.

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