Method for reducing nickel content in slag of high-magnesium nickel concentrate side-blown composite smelting furnace

Abstract

The invention relates to a method for reducing nickel content in slag of a high-magnesium nickel concentrate side-blown composite smelting furnace, and belongs to the field of metal smelting. According to the method, the problems of low reduction efficiency of high-magnesium nickel concentrate and high nickel content of slag are solved by optimizing spray gun layout and a reduction vulcanization process. The method specifically comprises the steps that oxygen-enriched air and fuel are sprayed in a smelting area through a double-channel spray gun, and melt is heated to 1450 DEG C or above; after the melt flows into a reduction area, spraying a powdery reducing agent (1.5-2.5% of the mass of the in-furnace concentrate) into the melt through a single-channel spray gun, and supplementing heat; adding powdery and spherical vulcanizing agents (6%-10% of the mass of the in-furnace concentrate in a ratio of 5: 1) at the same time to strengthen the vulcanization reaction; and slag is discharged after the melt is settled for more than or equal to 2.5 hours in an electrode area. According to the method, through direct injection of the pulverized coal, the synergistic effect of the composite vulcanizing agent and precise temperature control, the nickel content of the slag is reduced to 0.34% or below, the nickel recovery rate is increased, and the method is suitable for treatment of high-magnesium nickel ore and nickel-containing tailings.

Description

Technical Field

[0001] The invention belongs to the field of metal smelting and relates to a method for reducing the nickel content in slag of a high-magnesium-nickel concentrate side-blowing composite smelting furnace. Background Art

[0002] Nickel, as the vitamin among metal elements, is widely used in various fields. With the continuous expansion of application fields, the development and consumption of global nickel mineral resources are also increasing. High-grade nickel ores continue to decrease, and the problem of handling low-grade nickel ores and other nickel-containing tailings from smelting furnaces and kilns is gradually becoming prominent. The side-blown composite smelting furnace is an advanced furnace type in today's non-ferrous metallurgical furnaces. This furnace type is a composite depletion electric furnace based on the traditional side-blown smelting furnace. It uses a water-cooled retaining wall to divide the furnace into a smelting zone, a reduction zone and a depletion zone, realizing side-blowing smelting-reduction sulfide-electrode depletion in one, and has strong adaptability to low-grade nickel ores and other nickel-containing tailings from smelting furnaces and kilns. It is also suitable for the pyrometallurgical smelting of high magnesium oxide concentrates.

[0003] To improve direct metal recovery and reduce nickel content in the side-blown composite smelting furnace's tailings during production, the traditional process uses natural gas as fuel, injecting an appropriate amount of oxygen-enriched air into the furnace via a side-blowing gun to heat the melt, and then adding an appropriate amount of lump coal to the furnace top feed opening via a belt conveyor to reduce the slag. Using this traditional process, the lump coal mostly floats on the slag surface, reducing the oxidized nickel in the surface slag. However, the surface-floating lump coal is more susceptible to oxygen combustion and exothermic reaction, resulting in lower reduction efficiency. This also increases the furnace temperature, seriously affecting the life of the furnace lining in the flue gas zone. Summary of the Invention

[0004] The present invention provides a method for enhanced sulfidation reduction in a side-blown composite smelting furnace for high-magnesium-nickel concentrates. This method addresses the problem of high nickel content and valuable metal loss in the tailings of side-blown composite smelting furnaces. The method is particularly suitable for side-blown composite smelting furnaces used to process high-magnesium oxide materials and other nickel-containing tailings from smelting furnaces. The method improves the reduction effect of using coal as a reducing agent, reduces the participation of coal in the combustion reaction, and effectively reduces the nickel content in the slag of side-blown composite smelting furnaces processing high-magnesium-nickel concentrates and other nickel-containing tailings from smelting furnaces, thus addressing the problem of reducing valuable metal loss.

[0005] The technical solution of the present invention is: A method for reducing the nickel content in slag of a high-magnesium-nickel concentrate side-blown composite smelting furnace comprises the following steps: (1) High magnesium nickel concentrate is added to the side-blown composite smelting furnace from the top charging port of the smelting zone, oxygen-enriched air and fuel are sprayed into the furnace through the double-channel lance 1 to heat and melt the material to above 1450°C; (2) After the melt flows into the reduction zone, a powdered reducing agent is sprayed into the melt through a single-channel spray gun 2. The amount of reducing agent is 1.5%-2.5% of the mass of the concentrate fed into the furnace. At the same time, heat is added through the spray gun 1. The sulfiding agent is added through the feeding port at the top of the reduction zone. The amount of sulfiding agent is 6%-10% of the mass of the concentrate fed into the furnace. The mass ratio of powdered sulfiding agent to spherical sulfiding agent is 5:1. (3) The melt flows from the reduction zone to the electrode zone, and the slag is discharged after the electrodes are kept warm and the melt is allowed to settle for ≥2.5 hours. The final slag contains ≤0.34% nickel.

[0006] Spray gun 1 is a dual-channel spray gun, with gas fuel or powdered fuel injected into the inner channel and oxygen-enriched air injected into the outer channel; spray gun 2 is a single-channel spray gun, which injects a powdered reducing agent. The magnesium oxide content of the high-magnesium nickel concentrate is 12%-13%.

[0007] The powdered reducing agent has a carbon content of ≥50% and is delivered via nitrogen or high-pressure air, with a pipeline delivery pressure greater than 0.3 MPa and a pressure greater than 210 kPa at the tip of the spray gun. The sulfurizing agent has a sulfur content of ≥40%. The powdered sulfurizing agent is used to entrain in the melt to sulfurize elemental nickel, while the spherical sulfurizing agent sinks to the bottom to sulfurize the lower layer of slag.

[0008] The smelting zone spray gun 1 has a back pressure greater than 0.13 MPa, a natural gas to oxygen ratio of 1:1.6, and a total air volume of ≥1100 Nm³ / h. The reduction zone spray gun layout is such that one spray gun 2 is placed between every two spray guns 1. The back pressure of the reduction zone spray gun 1 is greater than 0.13 MPa, and the natural gas to oxygen ratio is 1:1.7. Spray guns 1 and 2 are inserted into the melt to a depth of ≥100 mm.

[0009] The melt temperature is monitored by maintaining the surface temperature of the water jacket in the smelting area at 150-240°C and the inlet and return water temperature difference at 9-11°C. The oxidation depth is determined by the magnetic iron content at the overflow slag and the amount of reducing agent is adjusted.

[0010] When the delivery pressure of spray gun 2 is lower than 300kPa or higher than 360kPa, use purge air to clean the pipeline.

[0011] The powdered reducing agent is pulverized coal or sulfur; the sulfiding agent is pyrite containing sulfur ≥40%, ensuring that the sulfiding agent can sink into the slag layer to carry out sulfidation reaction.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. Reduction efficiency is significantly improved Powdered reducing agent is directly sprayed into the melt: Pulverized coal and other reducing agents are sprayed directly into the melt through a single-channel spray gun (spray gun 2). This solves the problem of combustion loss caused by traditional lump coal floating on the slag surface, improves the utilization rate of the reducing agent, and effectively reduces the content of oxidized nickel in the slag.

[0013] The amount of reducing agent is precisely controlled (1.5%-2.5% of the mass of the concentrate fed into the furnace) to avoid excessive reduction and the formation of refractory metal alloys. At the same time, nitrogen / high-pressure air delivery (pressure > 0.3MPa) is used to ensure injection stability.

[0014] 2. Sulfurization reaction optimization Ratio of composite vulcanizing agent: powdered vulcanizing agent (quickly drawn into the melt) and spherical vulcanizing agent (sulfurized at the bottom) are mixed in a mass ratio of 5:1, which not only ensures the immediate vulcanization of elemental nickel (forming low-melting-point nickel sulfide), but also strengthens the vulcanization effect of the lower slag, avoiding the problem of vulcanizing agent agglomeration.

[0015] The sulfur content of the sulfiding agent is ≥40% to ensure the sulfurization efficiency. At the same time, the proportion (6%-10% of the mass of the concentrate entering the furnace) works synergistically with the reducing agent to prevent the nickel element from being enriched into a high-melting-point alloy.

[0016] 3. Refinement of smelting process parameters Spray gun layout and heat compensation: A reducing agent spray gun (spray gun 2) is arranged between every two fuel spray guns (spray gun 1) in the reduction zone. The fuel spray gun supplements the heat absorption of the reduction reaction (natural gas: oxygen = 1:1.7), maintains the melt temperature ≥1450℃, and avoids stagnation of the reduction reaction due to insufficient temperature.

[0017] Dual-channel spray gun design (spray gun 1): The inner channel sprays fuel, and the outer channel sprays oxygen-enriched air (back pressure > 0.13 MPa), enhancing melt agitation and melting rate. The total air volume is ≥ 1100 Nm³ / h, ensuring efficient heat transfer in the melting zone.

[0018] 4. Operation Monitoring and Stability Real-time monitoring of melt temperature: The melt state is indirectly judged by the surface temperature of the vertical water jacket (150-240℃) and the inlet and return water temperature difference (9-11℃). When the spray gun back pressure is abnormal, the temperature is increased or purged in time (clean the pipeline when the spray gun 2 pressure is <300kPa or >360kPa).

[0019] Sedimentation time ≥ 2.5 hours: The electrode area is allowed to stand still enough to allow nickel sulfide to settle. The amount of reducing agent is dynamically adjusted based on the analysis of magnetic iron content to ensure that the nickel content in the slag is ≤ 0.34%.

[0020] 5. Economic benefits and environmental protection Reduce metal loss: The nickel content in the slag is reduced from a higher level in traditional processes to below 0.34%, significantly improving the direct nickel recovery rate.

[0021] Extend the life of the furnace lining: reduce the high temperature in the furnace caused by the combustion of lump coal on the slag surface (the overheating problem in the flue gas area of ​​the traditional process), and reduce maintenance costs.

[0022] Wide adaptability: It is especially suitable for high-magnesia nickel concentrate and other nickel-containing tailings, solving the problem of low-grade resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of a side-blown composite melting furnace; Figure 2 It is a structural schematic diagram of a dual-channel spray gun 1; Figure 3 It is a structural schematic diagram of a single-channel spray gun 2. DETAILED DESCRIPTION

[0024] The present invention will be further described below through specific embodiments. Example

[0025] A method for reducing the nickel content in slag of a high-magnesium-nickel concentrate side-blown composite smelting furnace comprises the following steps: The side-blown composite smelting furnace is divided into a smelting zone, a reduction zone, and an electrode zone. During production, high-magnesium-nickel concentrate enters the furnace from the smelting zone's discharge port. Lance 1 heats and melts the material to above 1450°C. The melt flows from the smelting zone to the reduction zone under static pressure. Lance 2 injects a powdered reducing agent into the melt, while lance 1 replenishes heat. A sulfiding agent is added through a feed port at the top of the reduction zone. The melt flows from the reduction zone to the electrode zone under static pressure. The electrodes maintain heat, and the melt settles and separates. Finally, the slag is discharged through the slag outlet. The resulting slag has an average nickel content of 0.34.

[0026] Spray gun 1 is a dual-channel spray gun. The inner channel injects gas fuel (such as natural gas) or pulverized fuel (such as pulverized coal), and the outer channel injects oxygen-enriched air. When using gas fuel, it can be directly fed into the spray gun and ejected under pressure. When using pulverized fuel, compressed air or carrier nitrogen is used to draw the powder into the spray gun and eject it. Spray gun 2 is a single-channel spray gun. This single-channel spray gun serves as the channel for the powdered reductant. When using the powdered reductant, compressed air or carrier nitrogen is used to draw the powder into the spray gun and eject it. Spray gun 1 heats the slag through the spray gun nozzle, while spray gun 2 reduces the slag by injecting the reductant. Spray guns 1 and 2 are inserted to a depth of more than 100 mm to prevent the gun tips from sticking, which could cause the gas fuel and powdered reductant to escape from the furnace shell pores. When the pressure in the spray gun 2 delivery pipeline is below 300 kPa or above 360 ​​kPa, purge air is used to purge the delivery pipeline to prevent blockage.

[0027] High-magnesium-nickel concentrate is evenly added from the two top feed ports in the side-blown smelting zone to ensure the melting rate of the material in the furnace. The surface temperature of the vertical water jacket in the smelting zone is between 150-240°C, the average temperature difference between the vertical water jacket inlet and return water is between 9-11°C, and the melt temperature is above 1450°C. If there is severe leakage of fuel or powdered reducing agent around the furnace body or the back pressure of the spray gun gradually increases, it indicates that the spray gun blowing quality has deteriorated. The spray gun blowing quality can be improved by raising the temperature.

[0028] The back pressure of spray gun 1 in the smelting area is higher than 0.13Mpa, the ratio of natural gas to oxygen is 1:1.6, and the total air volume of the internal and external channels is greater than 1100Nm 3 / h, ensuring that the melt reaches the smelting temperature and the spray gun 1 can fully stir the melt, thereby accelerating the melting rate of the material; the spray guns in the reduction zone are arranged with a spray gun 2 installed between every two spray guns 1, the spray gun back pressure of the spray gun 1 in the reduction zone is higher than 0.13Mpa, and the ratio of natural gas to oxygen is 1:1.7, ensuring that there is a heat source to supplement heat after the powdered reducing agent enters the melt and absorbs heat in the reduction reaction, thereby meeting the temperature requirements of the reduction reaction.

[0029] The dosage of powdered reducing agent is 1.5%-2.5% of the concentrate mass entering the furnace. This ensures the powdered reducing agent's reducing effect while preventing excessive dosage, which can cause over-reduction of the melt and the formation of metal alloy phases. The powdered reducing agent has a carbon content of ≥50% and is delivered using nitrogen or high-pressure air. The pipeline delivery pressure is greater than 0.3 MPa, and the pressure at the spray gun tip is greater than 210 kPa to ensure smooth delivery of the powdered reducing agent without pipe blockage.

[0030] When adding the reducing agent, supplemental heat is applied through the spray gun 1 to ensure that the heat absorbed by the reduction reaction is equal to the heat added, so that the reduction reaction proceeds in a positive direction. When adding the reducing agent, a certain amount of sulfiding agent is added to ensure that the reduced metal element can be sulfided and separated into the nickel matte layer through sedimentation.

[0031] The sulfiding agent dosage is 6-10% of the concentrate mass, and the ratio of powdered sulfiding agent to spherical sulfiding agent is 5:1. This ensures that the powdered sulfiding agent can fully entrain into the melt to sulfide the reduced elemental nickel into nickel sulfide. The spherical sulfiding agent, due to its higher specific gravity than the side-blown composite smelting slag, sinks to the bottom, sulfiding the lower slag and ensuring the sulfidation effect. In addition, the mixed powdered sulfiding agent and spherical sulfiding agent can prevent the sulfiding agent from caking in the sulfiding agent bin, achieving smooth material discharge. The sulfur content of the sulfiding agent is greater than 40%. The powdered sulfiding agent is used to entrain into the melt to sulfide the elemental nickel, while the spherical sulfiding agent sinks to the bottom to sulfidize the lower slag.

[0032] In the electrode area, allow the slag to settle for at least 2.5 hours before discharging it to ensure sufficient settling of valuable metal sulfides. Hourly sampling and analysis are performed through the overflow slag outlet to determine the magnetic iron content of the slag, which can be used to determine the depth of oxidation within the furnace. If the depth of oxidation is high, adjust the reducing agent dosage appropriately to ensure effective reduction.

[0033] The unique spray gun layout and structure, the gas volume ratio of the spray gun, the method and ratio of reducing and sulfiding agents, and the simultaneous addition of reducing and sulfiding agents ensure that the oxidized nickel in the slag is reduced to elemental nickel, which is then sulfided to form nickel sulfide with smaller grains and a lower melting point. This prevents the elemental nickel from aggregating with other reduced elemental metals to form a larger nickel alloy with a higher melting point, which settles to the bottom and forms a frozen layer at the furnace bottom. This method can reduce the slag content of side-blown composite smelting furnaces to below 0.34.

Claims

1. A method for reducing the nickel content in slag of a high-magnesium-nickel concentrate side-blown composite smelting furnace, characterized in that: The method comprises the following steps: (1) adding high-magnesium-nickel concentrate into a side-blown composite smelting furnace from a charging port at the top of the smelting zone, injecting oxygen-enriched air and fuel through a double-channel lance 1, and heating and melting the material to above 1450°C; (2) After the melt flows into the reduction zone, powdered reducing agent is sprayed into the melt through a single-channel spray gun 2. The amount of reducing agent is 1.5%-2.5% of the mass of the concentrate fed into the furnace. At the same time, heat is supplemented through the spray gun 1. The sulfiding agent is added through the feeding port at the top of the reduction zone. The amount of sulfiding agent is 6%-10% of the mass of the concentrate fed into the furnace. The mass ratio of powdered sulfiding agent to spherical sulfiding agent is 5:

1. (3) The melt flows from the reduction zone to the electrode zone, and the slag is discharged after the electrode is kept warm and the melt is allowed to settle for ≥2.5 hours. The final slag contains ≤0.34% nickel.

2. The method according to claim 1, characterized in that The spray gun 1 is a double-channel spray gun, the inner channel of which is sprayed with gas fuel or powdered fuel, and the outer channel of which is sprayed with oxygen-enriched air; the spray gun 2 is a single-channel spray gun, which is sprayed with powdered reducing agent.

3. The method according to claim 1, characterized in that The magnesium oxide content of the high-magnesium nickel concentrate is 12%-13%.

4. The method according to claim 1, wherein The powdered reducing agent has a carbon content of ≥50% and is transported by nitrogen or high-pressure air. The pipeline transport pressure is greater than 0.3 MPa, and the pressure at the gun head of spray gun 2 is greater than 210 kPa.

5. The method according to claim 1, characterized in that The sulfur content of the vulcanizing agent is ≥40%. The powdered vulcanizing agent is used to be drawn into the melt to vulcanize elemental nickel, and the spherical vulcanizing agent is used to sink to the bottom to vulcanize the lower layer of slag.

6. The method according to claim 1, characterized in that The back pressure of the spray gun 1 in the smelting zone is higher than 0.13Mpa, the ratio of natural gas to oxygen is 1:1.6, and the total air volume is ≥1100Nm³ / h.

7. The method according to claim 2, characterized in that The spray gun layout in the reduction zone is that a spray gun 2 is arranged between every two spray guns 1, the spray gun back pressure of the reduction zone spray gun 1 is higher than 0.13Mpa, the natural gas and oxygen ratio is 1:1.7; the spray gun 1 and the spray gun 2 are inserted into the melt to a depth of ≥100mm.

8. The method according to claim 1, characterized in that The melt temperature is monitored by maintaining the surface temperature of the water jacket in the smelting area at 150-240°C and the inlet and return water temperature difference at 9-11°C. The oxidation depth is determined by the magnetic iron content at the overflow slag and the amount of reducing agent is adjusted.

9. The method according to claim 1, characterized in that When the delivery pressure of spray gun 2 is lower than 300kPa or higher than 360kPa, use purge air to clean the pipeline.

10. The method according to claim 1, characterized in that The powdered reducing agent is pulverized coal or sulfur; the sulfiding agent is pyrite containing sulfur ≥40%, ensuring that the sulfiding agent can sink into the slag layer to carry out sulfidation reaction.

Images