Desulfurization-smelting collaborative iron and valuable metal recovery method based on high-sulfur high-iron-nickel smelting iron slag

Abstract

The invention provides a method for recycling iron and valuable metal based on desulfurization-smelting cooperation of high-sulfur high-iron-nickel smelting iron slag, and belongs to the technical field of metallurgy solid waste recycling. Aiming at the problems of sulfur exceeding, nickel-chromium metal waste, environmental protection risk and the like caused by direct use of the high-sulfur high-iron-nickel smelting iron slag, efficient utilization of the iron slag and gradient recovery of metal are realized through four steps of green pellet preparation, oxidizing roasting consolidation desulfurization, reduction smelting and oxygen blowing. The method specifically comprises the steps that iron slag is dried and then matched with pulverized coal and bentonite to prepare wet pellets, the wet pellets are desulfurized to 0.15% or below through oxidizing roasting, and oxidized pellets with certain compressive strength are formed; then smelting in a submerged arc furnace to produce nickel-chromium-iron liquid; the iron liquid is subjected to oxygen blowing to form a ferronickel solution and high-chromium slag, the ferronickel solution is cast to produce ferronickel alloy, the high-chromium slag is subjected to wet leaching to recover chromium, and the final slag is used as a cement additive. According to the method, efficient removal of sulfur in the iron slag, synergistic extraction of nickel and chromium and full-amount recycling of solid waste are achieved, a metallurgical slag-metal-building material recycling system is formed, and economic and environment-friendly benefits are achieved.

Description

Technical Field

[0001] This invention relates to the field of metallurgical solid waste resource utilization, specifically to a method for the desulfurization-smelting synergistic recovery of iron and valuable metals based on high-sulfur, high-iron-nickel smelting slag. Background Technology

[0002] Nickel has an abundance of 0.008% in the Earth's crust, ranking 24th among known elements, and is mainly found in basic or ultrabasic rocks. Nickel is chalcophilic; therefore, in sulfur-rich environments, it preferentially combines with sulfur, forming sulfide magmas along with some chalcophile elements such as iron, copper, and cobalt. These magmas then separate from silicate magmas, forming nickel sulfide deposits under certain conditions. Because Ni... 2+ with Fe 2+ Mg 2+ Due to their similar plasma radii, nickel typically exists as a homogeneous phase within the olivine phase ((Mg,Fe)₂SiO₄) and goethite phase (FeO(OH)) lattices, rather than forming discrete nickel minerals. Currently, over 50 nickel minerals are known globally, with common industrially valuable ones including pyrrhotite, nickel pyrrhotite, nickel arsenopyrite, nickel serpentine, and nickel limonite. Therefore, extracting nickel and cobalt from nickel-bearing minerals produces iron-rich slag with approximately 60% iron content. However, because its sulfur content is >2%, direct use in ironmaking leads to excessive sulfur levels in the molten iron, requiring additional desulfurization. Furthermore, because it contains approximately 1% Cr and 1% Ni, direct use in ironmaking results in the ineffective extraction and recovery of chromium and nickel metals, leading to resource waste. Additionally, because the iron slag contains chromium, direct landfilling or use as a building material may cause heavy metal leaching, failing to meet environmental requirements for direct stockpiling.

[0003] This invention addresses the problem that directly using iron-rich slag in ironmaking leads to excessive sulfur levels in the molten iron, requiring additional desulfurization processes, and that the nickel and chromium elements are not effectively extracted and recovered, resulting in resource waste. It proposes a method for the synergistic recovery of iron and valuable metals from high-sulfur, high-iron-nickel slag through desulfurization and smelting, producing nickel-containing pig iron and recovering chromium, thus achieving high-value-added comprehensive utilization of the slag. Summary of the Invention

[0004] This invention provides a method for the co-processing recovery of iron and valuable metals from high-sulfur, high-iron-nickel smelting slag through desulfurization and smelting. The aim is to address the problem that directly using high-iron slag in ironmaking leads to excessive sulfur levels in the molten iron, requiring additional desulfurization processes, and resulting in the ineffective extraction and recovery of nickel and chromium, thus wasting resources. This invention is a co-processing technology for desulfurization pretreatment and smelting of high-sulfur (S≥2%), high-iron (TFe≥59%) nickel smelting slag, achieving the cascade recovery of valuable metals such as iron, nickel, and chromium, and the full utilization of solid waste resources.

[0005] Therefore, the present invention adopts the following technical solution: A method for the co-processed recovery of iron and valuable metals from high-sulfur, high-iron, and nickel smelting slag through desulfurization and smelting includes the following steps: (1) Preparation of green pellets: Dry the iron slag to a moisture content of less than 6%, mix the ingredients according to the ratio of iron slag: coal powder: bentonite = 100: (1-3): (0.8-2.5), and prepare wet pellets of 8-16mm. The drying equipment is a rotary drum dryer; pelleting is done by adding water to a pelletizing disc, and the moisture content of the wet pellets is controlled at 8-10%.

[0006] The initial composition of the high-sulfur, high-iron-nickel smelting slag meets the following requirements: TFe≥59%, S≥2%, Cr=0.5-1.0%, Ni=1.0-2.0%.

[0007] (2) Pellet consolidation desulfurization: After drying and preheating, wet pellets are roasted in an oxidizing atmosphere to consolidate and desulfurize the pellets to a sulfur content of ≤0.15%, thereby obtaining oxidized pellets with compressive strength; The calcination equipment for oxidizing atmosphere calcination is selected from oxidizing pellet vertical furnace or chain grate machine-rotary kiln; the calcination temperature is 1070±20℃, the grate temperature is 500±50℃; the compressive strength of oxidized pellets is ≥1900N / piece.

[0008] (3) Reduction smelting: Oxidized pellets are added to a submerged arc furnace with coke, quicklime and fluorite to smelt nickel-chromium-iron liquid, and the initial slag is used as roadbed material; The proportions and conditions for reduction smelting are as follows: the ratio of oxidized pellets to coke satisfies C / Fe=0.8; the amount of quicklime and fluorite added satisfies the material basicity R2=2.0-2.5; the smelting temperature is 1400-1500℃ (preferably 1450℃), and the smelting time is 40-60min.

[0009] (4) Oxygen blowing and separation and recovery: oxygen is blown into the nickel-chromium iron liquid to form high-chromium slag. The high-chromium slag is wet leached to recover chromium, and the final slag is used as a cement additive. Nickel-iron alloy is prepared after the iron liquid is cast.

[0010] The oxygen blowing and subsequent treatment meet the following requirements: the oxygen blowing rate is 2-4 Nm³ / min (preferably 3 Nm³ / min), and a high-chromium slag with a Cr₂O₃ content of 4.0-5.0% is formed after blowing; after wet leaching of the high-chromium slag, the chromium leaching rate is ≥85%, and the Cr leaching concentration in the final slag is <0.1 mg / L; the TFe content of the nickel-iron alloy is ≥95%, the Ni content is ≥0.2%, and the S content is ≤0.05%.

[0011] The entire process realizes the resource utilization of solid waste. The initial slag in step (3) is directly used as roadbed material with a Cr2O3 content of ≤0.1%; the final slag in step (4) is used as cement additive with a dosage of ≤15% and meets the heavy metal leaching toxicity standard.

[0012] The beneficial effects of this invention are as follows: 1. Optimization of high-efficiency desulfurization and pretreatment The oxidative roasting process reduces the sulfur content of iron slag to below 0.15%, avoiding the problem of excessive sulfur in molten iron during direct ironmaking, eliminating the need for subsequent desulfurization processes, and reducing production costs. Pelletizing technology ensures the material possesses sufficient compressive strength, providing physical stability for subsequent smelting.

[0013] 2. Co-recycling of valuable metals A step-by-step process of reduction smelting and oxygen blowing is employed to achieve the tiered extraction of iron, nickel, and chromium. After oxygen blowing separation, chromium is enriched in the form of high-chromium slag and recovered through wet leaching. Finally, the nickel-iron alloy is directly cast, significantly improving the resource utilization rate of scarce metals such as nickel and chromium and avoiding waste. Nickel recovery rate >95%, chromium leaching rate ≥85%, and the utilization rate of scarce metals is improved.

[0014] 3. Green resource utilization throughout the entire process The initial slag produced by smelting is directly used as roadbed material, and the final slag is used as cement additive, achieving zero solid waste discharge. At the same time, environmental risks are reduced by solidifying heavy metals (such as chromium), meeting environmental protection requirements. The products of each stage of the process are utilized with high added value, forming a circular economy chain of "metallurgical solid waste - metal recycling - building material raw materials". Attached Figure Description

[0015] Figure 1 This is a process flow diagram for the desulfurization-smelting co-recovery of iron and valuable metals from iron slag. Detailed Implementation

[0016] The present invention will be further explained below with reference to specific embodiments. Example

[0017] A method for the co-processed recovery of iron and valuable metals from high-sulfur, high-iron, and nickel smelting slag through desulfurization and smelting includes the following steps: (1) Preparation of green pellets: Iron slag with TFe content of 59.00%, S content of 2.16%, Cr content of 0.889% and Ni content of 1.72% was dried to a moisture content of less than 6% using a drum dryer. It was then mixed with coal powder with a -200 mesh content of 82% at a ratio of iron slag: coal powder: bentonite = 100: 2: 1.5. Green pellets were prepared by adding water using a pelletizing pan to obtain 8-16 mm wet pellets, with the moisture content of the wet pellets controlled at 8-10%.

[0018] (2) Pellet consolidation and desulfurization: Wet pellets are transported to the drying bed of the vertical furnace of oxidized pellets by belt. After drying and preheating, they are roasted in the vertical furnace of oxidized pellets. The grate temperature is controlled at 500±50℃ and the combustion chamber temperature is controlled at 1070±20℃ to consolidate and desulfurize the green pellets, producing oxidized pellets with an average compressive strength of 1900N / piece and a sulfur content of 0.13%.

[0019] (3) Reduction smelting: Iron slag and coke are batched according to C / Fe=0.8, and quicklime and fluorite are batched according to material basicity R2=2.0. The mixture is smelted in an electric arc furnace at 1450℃ for 50 minutes to produce molten iron with TFe content of 92.5%, Ni content of 1.65%, and Cr content of 0.82%; and primary slag with Cr2O3 content of 0.08% is produced, which is directly used as roadbed material.

[0020] (4) Oxygen is blown into the molten iron at 3 Nm³ / min to form a high-chromium slag with a Cr2O3 content of 4.5%. The high-chromium slag is wet leached to recover chromium. The final slag is tested and the Cr leaching concentration is <0.1 mg / L. As a cement additive, its dosage is ≤15%. Finally, a nickel-iron alloy with a TFe content of 95.2%, a Ni content of 0.25%, and a S content of 0.03% is obtained.

Claims

1. A method for the synergistic recovery of iron and valuable metals from high-sulfur, high-iron-nickel smelting slag through desulfurization and smelting, characterized in that... Includes the following steps: (1) Preparation of green pellets: Dry the iron slag to a moisture content of less than 6%, mix the ingredients according to the ratio of iron slag: coal powder: bentonite = 100: (1-3): (0.8-2.5), and prepare wet pellets of 8-16mm. (2) Pellet consolidation desulfurization: After drying and preheating, wet pellets are roasted in an oxidizing atmosphere to consolidate and desulfurize the pellets to a sulfur content of ≤0.15%, thereby obtaining oxidized pellets with compressive strength; (3) Reduction smelting: Oxidized pellets are added to a submerged arc furnace with coke, quicklime and fluorite to smelt nickel-chromium-iron liquid, and the initial slag is used as roadbed material; (4) Oxygen blowing and separation and recovery: oxygen is blown into the nickel-chromium iron liquid to form high-chromium slag. The high-chromium slag is wet leached to recover chromium, and the final slag is used as a cement additive. Nickel-iron alloy is prepared after the iron liquid is cast.

2. The method according to claim 1, characterized in that, In step (1), the drying equipment is a drum dryer; pelleting is done by adding water to a pelletizing disc, and the moisture content of the wet pellets is controlled at 8-10%.

3. The method according to claim 1, characterized in that, In step (2), the calcination equipment for oxidizing atmosphere calcination is selected from oxidizing pellet vertical furnace or chain grate machine-rotary kiln; the calcination temperature is 1070±20℃, the grate temperature is 500±50℃; the compressive strength of oxidized pellets is ≥1900N / piece.

4. The method according to claim 1, characterized in that, In step (3), the proportions and conditions for reduction smelting are as follows: the ratio of oxidized pellets to coke satisfies C / Fe=0.8; the amount of quicklime and fluorite added satisfies the material basicity R2=2.0-2.5; the smelting temperature is 1400-1500℃, and the smelting time is 40-60min.

5. The method according to claim 1, characterized in that, In step (4), the oxygen blowing and subsequent treatment meet the following requirements: the oxygen blowing rate is 2-4 Nm³ / min, and a high-chromium slag with a Cr2O3 content of 4.0-5.0% is formed after blowing; after wet leaching of the high-chromium slag, the Cr leaching concentration in the final slag is <0.1 mg / L; the TFe content of the nickel-iron alloy is ≥95%, the Ni content is ≥0.2%, and the S content is ≤0.05%.

6. The method according to claim 1, characterized in that, The initial composition of the high-sulfur, high-iron-nickel smelting slag meets the following requirements: TFe≥59%, S≥2%, Cr=0.5-1.0%, Ni=1.0-2.0%.

7. The method according to claim 1, characterized in that, The entire process realizes the resource utilization of solid waste. The initial slag in step (3) is directly used as roadbed material with a Cr2O3 content of ≤0.1%; the final slag in step (4) is used as cement additive with a dosage of ≤15% and meets the heavy metal leaching toxicity standard.

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