A method for directly processing laterite nickel ore to produce ferronickel using a composite furnace

Abstract

A method for producing ferronickel by directly treating laterite nickel ore by using a composite furnace, comprising the following steps: dehydrating raw ore, screening raw ore, mixing materials, briquetting, reducing in the composite furnace, and outputting. The method can realize direct smelting of coarse materials, reduce energy consumption for drying and pre-reducing materials at the front end, directly use the composite furnace to complete drying and pre-reducing roasting of laterite nickel ore, simplify the process, save equipment investment and site occupation, generate high smelting temperature by direct current arc, effectively transfer heat to the molten pool, uniformly distribute multiple electrodes at the bottom of the composite furnace, make the temperature of the hearth more uniform, make the reaction more sufficient, and be beneficial to improving the metal recovery rate, have no requirement for the composition of the laterite ore raw material, can meet the production of ferronickel regardless of the high or low nickel grade of the raw material or the mixing of multiple laterite nickel ores, directly send the carbonaceous reducing agent to the working surface through the central hole of the top electrode of the composite furnace, supplement the heat of the molten pool in the hearth of the composite furnace by the burners arranged around the hearth, and the above two measures can reduce the power consumption by about 10%.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal smelting technology, and in particular relates to a method for producing nickel-iron by directly processing laterite nickel ore using a composite furnace. Background Technology

[0002] Nickel, as a major alloying element in the smelting of stainless steel, can alter the microstructure of stainless steel, thereby improving its corrosion resistance, plasticity, toughness, and weldability. Laterite nickel ore refers to a mixture of hydrated iron oxide and hydrated magnesium silicate formed from long-term, large-scale weathering, leaching, alteration, and enrichment of basic rocks such as olivine or serpentine. It is a loose, clayey nickel oxide ore resource containing a large amount of water, characterized by easy mining but difficult processing.

[0003] Laterite nickel ore can produce nickel oxide, nickel sulfate, and ferronickel. Among these, nickel sulfate and ferronickel can be used by nickel refineries. Using ferronickel not only facilitates the manufacture of stainless steel but also reduces production costs. Direct reduced ferronickel (also known as sponge ferronickel) can directly replace stainless steel scrap, thus making it a major raw material for stainless steel production.

[0004] Currently, there are roughly three main processing technologies for laterite nickel ore worldwide: pyrometallurgical processes, hydrometallurgical processes, and combined pyrometallurgical and hydrometallurgical processes. Hydrometallurgical processes, based on the leaching solution used, can be further divided into ammonia leaching and pressurized acid leaching. Ammonia leaching is unsuitable for processing laterite nickel oxide ores with high copper and cobalt content, while pressurized acid leaching is only suitable for processing laterite nickel oxide ores with low magnesium content, and large-scale production faces significant environmental pressures. Combined pyrometallurgical and hydrometallurgical processes mainly include reduction roasting-atmospheric pressure ammonia leaching and segregation-reduction roasting-beneficiation, which can be used to process different types of nickel oxide ores, but the current technology is not stable enough, and the performance indicators fluctuate significantly.

[0005] Therefore, the processing technology of laterite nickel ore usually adopts pyrometallurgical process. The pyrometallurgical process mainly includes two processes depending on the smelting and output products: reduction smelting in electric furnace or blast furnace to produce nickel iron, and sulfidation smelting in electric furnace or blast furnace with sulfiding agent to produce nickel sulfate.

[0006] Although the pyrometallurgical process for producing nickel-iron alloys from laterite nickel oxide ore has the advantages of short process and high efficiency, the largest component of production cost is energy consumption. The electricity consumption of electric furnace smelting accounts for about 50% of the operating cost. In addition, the fuel consumption of drying and roasting pretreatment processes before smelting laterite nickel oxide ore can account for more than 65% of the operating cost.

[0007] In addition, the nickel content of the ore plays an important role in the production cost of pyrometallurgical processes. If the nickel content of the ore increases by 0.1 percentage points, the production cost can be reduced by about 3 to 4 percentage points; conversely, if the nickel content of the ore decreases by 0.1 percentage points, the production cost can be increased by about 3 to 4 percentage points. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a method for producing ferronickel by directly processing laterite nickel ore using a composite furnace. This method features a short process, simple operation, easy control, strong raw material adaptability, high production efficiency, low production cost, low equipment investment, low energy consumption, high ferronickel recovery rate, and environmental friendliness.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for producing ferronickel by directly processing laterite nickel ore using a composite furnace, comprising the following steps:

[0010] Step 1: Dehydration of raw ore

[0011] The laterite nickel ore is naturally dried in a stockpile to control the moisture content of the laterite nickel ore within the range of 15-20%.

[0012] Step 2: Screening of raw ore

[0013] The dehydrated laterite nickel ore is screened using a screening machine. The red stone blocks with a particle size of less than 20mm are directly used in subsequent steps. The red stone blocks with a particle size of more than 20mm need to be crushed. Only after being crushed into red stone blocks with a particle size of less than 20mm can they be used in subsequent steps.

[0014] Step 3: Mixing the materials

[0015] Redstone blocks, laterite, magnesite, and carbonaceous reducing agent are fed into a mixer in a set ratio by a quantitative belt feeder, and the mixer mixes the above raw materials evenly.

[0016] Step 4: Pressing the dough into balls

[0017] During the mixing process, water glass binder also needs to be added. After the mixing is completed, the prepared mixture is sent to a briquetting machine to produce briquettes with a particle size of 30-50mm.

[0018] Step 5: Restore

[0019] The lumps are directly fed into the furnace of the composite furnace, where they are dried, pre-reduced, and smelted until a nickel-iron alloy solution is produced.

[0020] Step Six: Output

[0021] The nickel-iron alloy solution is discharged from the tapping port of the composite furnace and enters the casting machine. After being cooled by the casting machine, it forms a nickel-iron alloy ingot. At the same time, the slag is discharged from the slag outlet of the composite furnace and is used as a building material after water quenching.

[0022] In step three, the proportion of redstone blocks is 5-10%, the proportion of laterite is 70-80%, the proportion of magnesite is 0-3%, and the proportion of carbonaceous reducing agent is 1-15%.

[0023] In step five, the smelting time per furnace is 4–6 hours, the slag discharge frequency is 6–8 times per day, the furnace smelting temperature is 1400–1650℃, the furnace top temperature is 900–1200℃, the furnace top pressure is 0–100 Pa, the furnace bottom temperature is below 300℃, the furnace flue gas emission temperature is 900–1200℃, the water-cooled flue outlet exhaust temperature is 120–180℃, the chimney outlet exhaust temperature is below 100℃, and the chimney outlet exhaust dust content is 80 mg / Nm³. 3 the following.

[0024] In step five, the composite furnace is powered by a DC transformer. The positive terminal of the DC transformer is electrically connected to the top electrode of the composite furnace, and the negative terminal of the DC transformer is electrically connected to the bottom electrode of the composite furnace.

[0025] In step five, the top electrode of the composite furnace adopts a hollow structure. During the smelting process, the carbonaceous reducing agent is directly fed to the working surface through the central channel of the top electrode. The feeding amount of the carbonaceous reducing agent is 0-10%.

[0026] In step five, a burner is installed around the furnace chamber of the composite furnace. The flames emitted by the burner replenish the heat of the molten pool in the furnace chamber. Only then can the power supply of the DC transformer be reduced to lower energy consumption.

[0027] In step five, the bottom electrode of the composite furnace is made of multiple electrodes that are evenly distributed.

[0028] The beneficial effects of this invention are:

[0029] This invention discloses a method for producing ferronickel from laterite nickel ore using a composite furnace. This method allows for the direct smelting of relatively coarse materials, reducing energy consumption in upstream material drying and pre-reduction processes, and minimizing heat loss during the process. The composite furnace simultaneously completes the drying and pre-reduction roasting of the laterite nickel ore, significantly simplifying the process and saving on equipment investment and space requirements. The high-temperature plasma DC arc generates high smelting temperatures and effectively transfers heat to the molten pool. Furthermore, the multiple and evenly distributed bottom electrodes of the composite furnace ensure more uniform furnace temperature and a more complete reaction, improving metal recovery. The method is not limited by the composition of the laterite ore; regardless of nickel grade or the mixture of different laterite nickel ores, it can meet the requirements for ferronickel production. The top electrode of the composite furnace delivers a carbonaceous reducing agent directly to the working surface through a central channel, and burners arranged around the furnace chamber supplement the heat to the molten pool. These two combined measures can reduce energy consumption by approximately 10%, providing a low-cost ferronickel alloy for stainless steel smelting. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of a method for producing ferronickel by directly processing laterite nickel ore using a composite furnace according to the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0032] like Figure 1 As shown, a method for producing ferronickel by directly processing laterite nickel ore using a composite furnace includes the following steps:

[0033] Step 1: Dehydration of raw ore

[0034] The laterite nickel ore is naturally dried in a stockpile to control the moisture content of the laterite nickel ore within the range of 15-20%.

[0035] Step 2: Screening of raw ore

[0036] The dehydrated laterite nickel ore is screened using a screening machine. The red stone blocks with a particle size of less than 20mm are directly used in subsequent steps. The red stone blocks with a particle size of more than 20mm need to be crushed. Only after being crushed into red stone blocks with a particle size of less than 20mm can they be used in subsequent steps.

[0037] Step 3: Mixing the materials

[0038] Redstone blocks, laterite ore, magnesite (whether to add it depends on the alkaline composition in the composite furnace), and carbonaceous reducing agent (anthracite or coke granules) are fed into a mixer in a set proportion by a quantitative belt feeder. The mixer then mixes the above raw materials evenly. Specifically, the proportion of redstone blocks is 5-10%, the proportion of laterite ore is 70-80%, the proportion of magnesite is 0-3%, and the proportion of carbonaceous reducing agent is 1-15%.

[0039] Step 4: Pressing the dough into balls

[0040] During the mixing process, water glass binder also needs to be added. After the mixing is completed, the prepared mixture is sent to a briquetting machine to produce briquettes with a particle size of 30-50mm.

[0041] Step 5: Restore

[0042] The lumps are directly fed into the furnace of the composite furnace, where they are dried, pre-reduced, and smelted until a nickel-iron alloy solution is produced. Specifically, each furnace smelting time is 4–6 hours, with slag discharges 6–8 times per day. The furnace smelting temperature is 1400–1650℃, the furnace top temperature is 900–1200℃, the furnace top pressure is 0–100 Pa, the furnace bottom temperature is below 300℃, the furnace flue gas emission temperature is 900–1200℃, the water-cooled flue gas outlet temperature is 120–180℃, the chimney outlet exhaust temperature is below 100℃, and the chimney outlet exhaust dust content is 80 mg / Nm³. 3 The following describes the process: The composite furnace is powered by a DC transformer. The positive terminal of the DC transformer is electrically connected to the top electrode of the composite furnace, and the negative terminal is electrically connected to the bottom electrode. The top electrode of the composite furnace has a hollow structure. During the smelting process, the carbonaceous reducing agent is directly fed to the working face through the central channel of the top electrode. The feed rate of the carbonaceous reducing agent (pulverized coal) is 0-10%. Burners are arranged around the furnace chamber of the composite furnace. The flames emitted by the burners supplement the heat of the molten pool in the furnace chamber. Only under these conditions can the power supply from the DC transformer be reduced to lower energy consumption. The bottom electrodes of the composite furnace are multiple and evenly distributed. The technical performance parameters of the composite furnace are: furnace shell diameter φ7080mm, furnace chamber diameter φ4680mm, furnace wall height 10787mm, top electrode diameter φ880mm, bottom electrode diameter φ400mm, and 10 bottom electrodes (one in the center, three evenly distributed in the inner ring, and six evenly distributed in the outer ring). The DC transformer has a power of 5000KVA, a secondary DC voltage of 120~200V, 17 adjustable power levels, and a power density of 314KVA / m³. 2 The calorific value of the burner is 200,000 watts.

[0043] Step Six: Output

[0044] The nickel-iron alloy solution is discharged from the tapping port of the composite furnace and enters the casting machine. After being cooled by the casting machine, it forms a nickel-iron alloy ingot. At the same time, the slag is discharged from the slag outlet of the composite furnace and is used as a building material after water quenching.

[0045] Example 1:

[0046] Raw ore: Single laterite nickel ore, with the following chemical composition: Ni-1.52, Fe-14.05, MgO-23.67, SiO2-38.12.

[0047] Process conditions: Laterite nickel ore is screened to obtain redstone blocks with a particle size of less than 20mm, and redstone blocks with a particle size of more than 20mm are crushed to less than 20mm; during mixing, the amount of crushed redstone blocks added is 5%, anthracite added is 2%, coke powder added is 3%, and magnesite added is 3%. An appropriate amount of water glass binder is added during the mixing process; after the mixing is completed, the mixture is pressed into briquettes to prepare briquettes with a particle size of 30-50mm; the briquettes are added into the composite furnace, and the secondary output voltage of the DC transformer is adjusted to 120V to ensure that the smelting temperature in the furnace is >1400℃. During the smelting process, 5% carbonaceous reducing agent (coal powder) is directly sent to the working face through the central channel of the top electrode, and the burner is turned on in time to supplement the heat.

[0048] Under these process conditions, the resulting nickel-iron alloy has the following properties: nickel grade of 12% and nickel recovery rate of 92.8%; iron grade of 86.18% and iron recovery rate of 90.5%.

[0049] Example 2:

[0050] Raw ore: Three different types of lateritic nickel ore. The chemical composition of the first type of lateritic nickel ore is: Ni-1.52, Fe-14.05, MgO-23.67, SiO2-38.12, with a ratio of 45%. The chemical composition of the second type of lateritic nickel ore is: Ni-1.72, Fe-17.86, MgO-23.83, SiO2-33.51, with a ratio of 45%. The chemical composition of the third type of lateritic nickel ore is: Ni-1.72, Fe-21.42, MgO-13.51, SiO2-36.97, with a ratio of 10%.

[0051] Process conditions: Laterite nickel ore is screened to obtain redstone blocks with a particle size of less than 20mm, and redstone blocks with a particle size of more than 20mm are crushed to less than 20mm; during mixing, crushed redstone blocks are not added, anthracite is added at 2%, coke powder at 4%, and magnesite at 3%, and an appropriate amount of water glass binder is added during the mixing process; after mixing, the mixture is pressed into briquettes to prepare briquettes with a particle size of 30-50mm; the secondary output voltage of the DC transformer is adjusted to 140V to ensure that the smelting temperature in the furnace is >1400℃; during the smelting process, 5% carbonaceous reducing agent (coal powder) is directly sent to the working face through the central channel of the top electrode, and the burner is turned on in a timely manner to supplement heat.

[0052] Under these process conditions, the resulting nickel-iron alloy has the following properties: nickel grade of 12.25% and nickel recovery rate of 93.4%; iron grade of 87.02% and iron recovery rate of 90.8%.

[0053] In the two embodiments described above, when the process conditions remain unchanged, the only difference is that no reducing agent is added during the mixing stage, but the carbonaceous reducing agent (coal powder) is directly sent to the working face through the central channel of the top electrode during the refining process, which can also produce nickel-iron alloy of the same quality.

[0054] The solutions described in the embodiments are not intended to limit the scope of patent protection of this invention. All equivalent implementations or modifications that do not depart from the scope of this invention are included in the patent scope of this case.

Claims

1. A method for producing ferronickel from laterite nickel ore using a composite furnace, characterized in that... Includes the following steps: Step 1: Dehydration of raw ore The laterite nickel ore is naturally dried in a stockpile to control the moisture content of the laterite nickel ore within the range of 15-20%. Step 2: Screening of raw ore The dehydrated laterite nickel ore is screened using a screening machine. The red stone blocks with a particle size of less than 20mm are directly used in subsequent steps. The red stone blocks with a particle size of more than 20mm need to be crushed. Only after being crushed into red stone blocks with a particle size of less than 20mm can they be used in subsequent steps. Step 3: Mixing the materials Redstone blocks, laterite, magnesite, and carbonaceous reducing agent are fed into a mixer in a set ratio by a quantitative belt feeder, and the mixer mixes the above raw materials evenly. Step 4: Pressing the dough into balls During the mixing process, water glass binder also needs to be added. After the mixing is completed, the prepared mixture is sent to a briquetting machine to produce briquettes with a particle size of 30-50mm. Step 5: Restore The lumpy material is directly fed into the furnace chamber of the composite furnace, where it is dried, pre-reduced, and smelted. This allows for the direct smelting of coarser materials, reducing energy consumption in the initial material drying and pre-reduction processes, until a nickel-iron alloy solution is produced. The top electrode of the composite furnace has a hollow structure, allowing carbonaceous reducing agent to be directly fed to the working surface through the central channel of the top electrode during the smelting process. The feed rate of the carbonaceous reducing agent is 0-10%. Burners are arranged around the furnace chamber of the composite furnace, and the flames emitted by the burners supplement the heat of the molten pool in the furnace chamber. This allows for a reduction in the power supply from the DC transformer, thereby reducing energy consumption. The bottom electrode of the composite furnace consists of multiple electrodes that are evenly distributed. Step Six: Output The nickel-iron alloy solution is discharged from the tapping port of the composite furnace and enters the casting machine. After being cooled by the casting machine, it forms a nickel-iron alloy ingot. At the same time, the slag is discharged from the slag outlet of the composite furnace and is used as a building material after water quenching.

2. The method for producing ferronickel from laterite nickel ore using a composite furnace according to claim 1, characterized in that: In step three, the proportion of redstone blocks is 5-10%, the proportion of laterite is 70-80%, the proportion of magnesite is 0-3%, and the proportion of carbonaceous reducing agent is 1-15%.

3. The method for producing ferronickel from laterite nickel ore using a composite furnace according to claim 1, characterized in that: In step five, the smelting time for each furnace is 4-6 hours, the number of slag discharges per day is 6-8, the smelting temperature in the furnace is 1400-1650℃, the furnace top temperature is 900-1200℃, the furnace top pressure is 0-100Pa, the furnace bottom temperature is below 300℃, the furnace flue gas emission temperature is 900-1200℃, the flue gas outlet temperature of the water-cooled flue is 120-180℃, the exhaust gas temperature at the chimney outlet is below 100℃, and the dust content of the exhaust gas at the chimney outlet is below 80mg / Nm³.

4. The method for producing ferronickel from laterite nickel ore using a composite furnace according to claim 1, characterized in that: In step five, the composite furnace is powered by a DC transformer. The positive terminal of the DC transformer is electrically connected to the top electrode of the composite furnace, and the negative terminal of the DC transformer is electrically connected to the bottom electrode of the composite furnace.

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