A method for producing ferronickel by selective reduction and simultaneous drying and dewatering of a siliceous-magnesic laterite nickel ore in an electric furnace

Abstract

A method for selective reduction, simultaneous drying and dehydration, and electric furnace smelting of ferronickel from ferrosilicon-magnesium laterite nickel ore is disclosed, belonging to the field of mineral processing and metallurgical technology. The steps are as follows: Ferrosilicon-magnesium laterite nickel ore is crushed and placed in a silo, then fed into a multi-stage cyclone preheating and drying system. Adsorbed water is removed by the preheated airflow, followed by heating to remove structural water, forming a dried material. The dried material undergoes gas-solid separation to form a primary solid material which enters the reduction reactor. High-temperature flue gas is returned to the preheating and drying system for further preheating and drying. Nitrogen and methane or natural gas are introduced into the inlet of the reduction reactor, resulting in the outflow of reduced material. The secondary solid material after gas-solid separation enters the smelting reactor, with excess methane returned to the main furnace for combustion and heating. The secondary solid material is mixed with flux to adjust the silicon-magnesium ratio before smelting, followed by cooling to obtain ferronickel alloy and slag. This method solves the practical problems of rotary kiln pre-reduction-electric furnace smelting processes, such as easy ring formation in the rotary kiln, low operating efficiency, and high power consumption.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing and metallurgical technology, and specifically relates to a method for selective reduction, simultaneous drying and dehydration, and electric furnace smelting of ferronickel from silicomagnesian laterite nickel ore. Background Technology

[0002] Nickel is an important strategic metal, widely used in stainless steel, batteries, electroplating, catalysts, and other fields. In actual production, the mainstream and mature process for processing ferrosilicon-magnesium laterite nickel ore is the rotary kiln pre-reduction-electric furnace smelting (RKEF) process. However, rotary kilns suffer from problems such as ring formation, low operating rate, and high power consumption, resulting in high production costs. Therefore, reducing the production cost of ferrosilicon-magnesium laterite nickel ore based on pyrometallurgical processes is crucial.

[0003] Application CN201310449196.8 discloses a smelting method for ferrosilicon-magnesium type lateritic nickel ore, including the following steps: crushing and grinding the ferrosilicon-magnesium type lateritic nickel ore to obtain a ferrosilicon-magnesium type nickel ore slurry; adding calcium carbonate to the ferrosilicon-magnesium type nickel ore slurry to neutralize and remove iron and aluminum, and then adding sodium hydroxide to adjust the pH to obtain a nickel hydroxide product. Chromium ore and flux are added to the nickel hydroxide product and melted in a plasma furnace to form a mother liquor. After the mother liquor is completely melted, coke is added for smelting, and additives are added simultaneously to obtain a nickel-chromium alloy product. This invention combines hydrometallurgical and pyrometallurgical processes, resulting in a complex production process, difficulty in controlling the moisture content of materials, high production costs, and difficulty in large-scale industrial application.

[0004] Application CN200810132540.X discloses a method for smelting ferrosilicon-magnesium laterite nickel ore. The method involves mixing the ferrosilicon-magnesium laterite nickel ore with a sulfiding agent and then pressing it into briquettes to obtain briquettes with a strength of 4 MPa to 12 MPa. The briquettes, flux, and coke are then fed into a blast furnace for smelting to obtain low-grade nickel matte and slag. However, this process is energy-intensive, highly dependent on coke, and causes severe environmental pollution. Especially with increasingly stringent environmental protection requirements, its industrial application prospects are bleak. Therefore, the development of a green, environmentally friendly, and low-energy-consumption innovative process to reduce the production cost of ferrosilicon-magnesium laterite nickel ore is of significant practical importance. Summary of the Invention

[0005] To address the problems of ring formation, low efficiency, and high power consumption in existing rotary kiln pre-reduction-electric furnace smelting (RKEF) processes, this invention provides a method for producing ferronickel through selective reduction, simultaneous drying and dehydration, and electric furnace smelting of ferrosilicon-magnesia type laterite nickel ore. Utilizing the strong reducing power of methane on nickel oxides and its weak reducing power on iron oxides, methane is used as a reducing agent. Under fluidized bed roasting conditions, nickel oxides are selectively reduced to metallic nickel (Ni) with a metallization rate ≥90%, while the majority of iron oxides are reduced to ferrous oxide, and a small amount of ferrous oxide is reduced to a metallization rate ≤20%. The material contains % metallic iron; in addition, serpentine is simultaneously dried and dehydrated during fluidized selective reduction roasting, meeting the requirement of ≤1.5% moisture content for the next electric furnace smelting process; during the electric furnace smelting process, at a temperature of 1550-1600℃, the silicon-magnesium ratio (SiO2 / MgO mass ratio) in the material is adjusted to (1.4-1.7):1 by adding silica or magnesia, and high-grade nickel-iron alloy and smelting slag are obtained. The smelting slag can be used as a raw material for cement production, effectively realizing the comprehensive utilization of all components of silicon-magnesium type laterite nickel ore.

[0006] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting, specifically includes the following steps:

[0007] Step (1): Crushing

[0008] The ferrosilicon-magnesium type laterite nickel ore is crushed to a particle size ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 25-40% of the total mass, and fed into the silo;

[0009] Step (2): Preheating and drying

[0010] The silicomagnesian laterite nickel ore in the silicomagnesian ...

[0011] Step (3): Selective reduction

[0012] After gas-solid separation, the dried material forms a primary solid material, which is fed into a fluidized bed reduction reactor. Nitrogen and methane or natural gas are introduced into the nitrogen inlet and reducing gas inlet of the fluidized bed reduction reactor, respectively. The primary solid material is in a fluidized state under the action of nitrogen and methane or natural gas, and undergoes a selective reduction reaction with methane at a temperature of 600-700°C in the reduction reactor to form a reduced material. After gas-solid separation, the excess methane of the reduced material is returned to the fluidized bed roasting main furnace for combustion and heating.

[0013] Step (4): Electric furnace smelting

[0014] After the gas-solid separation of the reducing material, the secondary solid material is mixed with quartz sand or magnesia flux to adjust the silicon-magnesium ratio in the secondary solid material, and then fed into the electric furnace smelting reactor. After smelting, the material is discharged from the nickel-iron molten metal outlet and the slag outlet, respectively. After cooling, nickel-iron alloy and slag are obtained.

[0015] in:

[0016] In step (1), the Ni grade of the ferrosilicon-magnesium type laterite nickel ore is 0.8-3.0%, and it contains 7.5-20% TFe, 30-45% SiO2, 20-35% MgO by weight percentage, and ≤15% water by mass percentage.

[0017] In step (2), the ferrosilicon-magnesium type laterite nickel ore is preheated in a multi-stage cyclone preheating system at a temperature of 400–550°C, and the ratio of the gas volumetric flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.10–0.30 m³ / s. 3 / kg.

[0018] In step (2), the heating temperature of the ferrosilicon-magnesium type laterite nickel ore in the roasting furnace is 800-1000℃.

[0019] In step (2), the main reaction formulas for the drying reaction of adsorbed water and the removal reaction of structural water in the preheating and heating process of ferrosilicon-magnesium laterite nickel ore are as follows:

[0020] H₂O(l)=H₂O(g) (1)

[0021] Mg3Si2(OH)4O5=Mg2SiO4+MgSiO3+2H2O (2)

[0022] In step (3), the residence time of the primary solid material in the reduction reactor is 30–60 min; the ratio of the volumetric flow rate of methane and nitrogen or natural gas entering the reduction reactor to the mass flow rate of the primary solid material is 0.06–0.40 m³. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 20-30%.

[0023] In step (3), the main chemical reaction formula is:

[0024] NiO + CH4 = Ni + CO + H2 (3)

[0025] 3Fe2O3+CH4=2Fe3O4+CO+2H2 (4)

[0026] Fe3O4+CO / H2 =3FeO+CO2 / H2O (5)

[0027] CH4=C+2H2 (6)

[0028] In addition, some ferrous oxide may undergo a reduction reaction to produce a small amount of metallic iron, such as:

[0029] FeO + CO / H2 = Fe + CO2 / H2O (7)

[0030] Or FeO+C=Fe+CO. (8)

[0031] In step (3), the metallization rate of nickel in the reducing material is ≥90%, and the metallization rate of iron is ≤20%.

[0032] In step (4), quartz sand or magnesia flux is added to adjust the mass percentage of SiO2 / MgO in the secondary solid material to (1.4~1.7):1.

[0033] In step (4), the mass of the added quartz sand or magnesia flux accounts for 8 to 30% of the mass of the laterite nickel ore raw material.

[0034] In step (4), the main reaction formula for the smelting reaction is:

[0035] 2MgO + SiO2 = Mg2SiO4 (9)

[0036] MgO + SiO2 = MgSiO3 (10)

[0037] 2FeO + SiO2 = Fe2SiO4. (11)

[0038] In step (4), the electric furnace melting temperature is 1550-1600℃ and the melting time is 30-90min.

[0039] In step (4), the nickel-iron alloy contains ≥15% Ni by mass percentage, with a Ni recovery rate ≥90%, ≤80% TFe by mass percentage, and a Fe recovery rate of 10-20%.

[0040] The basic principle of this invention is that ferrosilicon-magnesium type lateritic nickel ore is subjected to multi-stage cyclone drying at 400–550°C and fluidized roasting at 800–1000°C for dehydration and decomposition, thereby removing adsorbed water and structural water from the lateritic nickel ore. Serpentine Mg3Si2(OH)4O5 is transformed into forsterite Mg2SiO4 and pyroxene MgSiO3. During the reduction process, hematite Fe2O3 in the ferrosilicon-magnesium type lateritic nickel ore is selectively reduced to FeO in a fluidized state. A small amount of FeO undergoes over-reduction to generate metallic iron Fe with a metallization rate ≤20%, wherein NiO is produced at 600–70°C. At 0℃, the metal is selectively reduced by methane to metallic Ni with a metallization rate ≥90%. The metallic Ni in the reduced material is fused with metallic iron during electric furnace smelting at 1550~1600℃ to form a high-grade nickel-iron alloy, which is discharged through the nickel-iron molten material discharge port. At the same time, depending on the composition of the raw materials, the silicon-magnesium ratio in the reduced material is adjusted by adding quartz sand or magnesia flux, that is, the mass ratio of SiO2 / MgO is (1.4~1.7):1. Under high-temperature electric furnace smelting conditions, a low-melting-point liquid silicon-magnesium slag is formed and discharged through the slag discharge port. After cooling, it can be used as a high-quality raw material for cement.

[0041] Compared with the existing rotary kiln-electric furnace smelting process for processing ferrosilicon-magnesium laterite nickel ore, the method of this invention can not only achieve selective reduction and simultaneous drying and dehydration of ferrosilicon-magnesium laterite nickel ore with high heat recycling efficiency, but also obtain high-grade nickel-iron alloys. It effectively solves the practical problems of easy ring formation, low operating efficiency, and high power consumption in the rotary kiln pre-reduction-electric furnace smelting process. The solid particles of ferrosilicon-magnesium laterite nickel ore are in a fluidized state, with high gas-solid mass and heat transfer efficiency, rapid drying and dehydration and chemical reaction, and low roasting energy consumption. The drying and dehydration of solid materials are carried out simultaneously with selective reduction. The nickel oxide (NiO) in the ferrosilicon-magnesium laterite is selectively reduced to metallic Ni, which is then fused with a small amount of metallic iron (Fe) during the electric furnace smelting process to form a high-grade nickel-iron alloy. Most of the hematite Fe2O3 is converted into ferrous oxide during the reduction process and reacts with quartz SiO2 during the electric furnace smelting process to form low-melting-point fir olivine. At the same time, the silicon-magnesium ratio of the reduced material is adjusted by adding fluxes such as quartz sand or magnesia sand during the electric furnace smelting process, i.e., the mass ratio of SiO2 / MgO is (1.4~1.7):1, to form a low-melting-point liquid ferrosilicon slag, which facilitates the stratified separation of liquid nickel-iron alloy and smelting slag. Attached Figure Description

[0042] Figure 1 A schematic diagram of the process flow for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting. Detailed Implementation

[0043] To further describe the present invention, the method of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0044] In the embodiments of the present invention, the flux quartz sand contains ≥90% SiO2 by weight and has a loss on ignition ≤1%; the flux magnesia contains ≥90% MgO by weight and has a loss on ignition ≤1%.

[0045] In the embodiments of the present invention, the reducing gas is methane or natural gas.

[0046] Example 1

[0047] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore through selective reduction, simultaneous drying and dehydration, and electric furnace smelting is illustrated in the following process flow diagram: Figure 1 As shown, the specific steps include:

[0048] Step (1): Crushing

[0049] The ferrosilicon-magnesium type lateritic nickel ore is crushed to a particle size ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 35% of the total mass and is fed into the silo. The ferrosilicon-magnesium type lateritic nickel ore has a Ni grade of 0.94%, contains 7.80% TFe, 38.80% SiO2, 32.50% MgO by weight, and 12.96% water by weight.

[0050] Step (2): Preheating and drying

[0051] The silica-magnesia type lateritic nickel ore in the silo is fed into a multi-stage cyclone preheating and drying system. The preheating system temperature is 450℃, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.15m³. 3 / kg, the silica-magnesia type lateritic nickel ore is desorbed by preheated airflow and then fed into the heating system of the fluidized roasting main furnace to remove structural water and form a dry material. The heating temperature of the silica-magnesia type lateritic nickel ore in the roasting main furnace is 850℃, and the residence time of the dry material in the fluidized roasting main furnace is 8s. The high-temperature flue gas after gas-solid separation of the dry material is returned to the preheating and drying system to continue preheating the silica-magnesia type lateritic nickel ore.

[0052] Step (3): Selective reduction

[0053] The dried material, after gas-solid separation, forms a primary solid material, which is fed into a fluidized bed reduction reactor. Nitrogen and methane or natural gas are introduced into the nitrogen inlet and reducing gas inlet of the reactor, respectively. The primary solid material is fluidized under the influence of nitrogen and methane or natural gas, and undergoes a selective reduction reaction with methane within the reactor. The temperature of the primary solid material during the reduction reaction in the reactor is 630℃, and the residence time of the primary solid material in the reactor is 30 min. The ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.15 m³ / s. 3 / kg, the volume concentration of methane gas entering the reduction reactor is 25%, forming a reduced material. The metallization rate of nickel in the reduced material is 92.20%, and the metallization rate of iron is 12.76%. After gas-solid separation, the excess methane in the reduced material is returned to the fluidized roasting main furnace for combustion and heating.

[0054] Step (4): Electric furnace smelting

[0055] The secondary solid material formed after gas-solid separation of the reduced material is mixed with quartz sand or magnesia flux. The quartz sand contains 92% SiO2 by weight and has a loss on ignition of 0.56%. The mass percentage of the added quartz sand flux is 14% of the mass percentage of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid material is adjusted to 1.6:1. The mixture is then fed into an electric furnace smelting reactor. The electric furnace smelting temperature is 1550℃, and the smelting time is 30 minutes. After smelting in the electric furnace, the molten nickel-iron alloy is discharged from the molten nickel-iron outlet and the slag outlet, respectively. After cooling, nickel-iron alloy and slag are obtained. The nickel-iron alloy contains 23.44% Ni by mass, with a Ni recovery rate of 95.40%. It also contains 71.91% TFe by mass, with an Fe recovery rate of 13.54%.

[0056] Example 2

[0057] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0058] (1) The low-grade ferrosilicon-magnesium type laterite nickel ore used in the embodiments of the present invention has a Ni grade of 2.95%, contains 19.37% TFe, 43.60% SiO2, and 21.62% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 40% of the total mass, and contains 13.68% water by mass percentage.

[0059] (2) The silica-magnesia type lateritic nickel ore is preheated to 550℃ in a multi-stage cyclone preheating system, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.30 m³ / s. 3 / kg; The heating temperature of the silica-magnesia type laterite nickel ore in the roasting furnace is 1000℃, and the residence time of the dried material in the fluidized roasting furnace is 5s;

[0060] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 700℃, and the residence time of the primary solid material in the reduction reactor is 55 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.35 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 30%;

[0061] (4) The metallization rate of nickel in the reduced material was 97.31%, and the metallization rate of iron was 19.60%;

[0062] (5) After the secondary solid material is mixed with the magnesia flux, it is put into the electric furnace for smelting. The magnesia contains 95% MgO by weight and has a loss on ignition of 0.35%. The mass of the added magnesia flux accounts for 9% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid material is adjusted to 1.4:1. The electric furnace smelting temperature is 1600℃ and the smelting time is 50min.

[0063] (6) The nickel-iron alloy contains 44.65% Ni by mass percentage, with a Ni recovery rate of 96.07%, and contains 53.63% TFe by mass percentage, with an Fe recovery rate of 19.13%.

[0064] Example 3

[0065] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0066] (1) The low-grade ferrosilicon-magnesium type laterite nickel ore used in the embodiments of the present invention has a Ni grade of 1.25%, contains 10.66% TFe, 40.73% SiO2, and 31.30% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 25% of the total mass, and contains 14.28% water by weight percentage.

[0067] (2) The silica-magnesia type lateritic nickel ore is preheated to 500℃ in a multi-stage cyclone preheating system, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.20 m³ / s. 3 / kg; The heating temperature of the silica-magnesia type laterite nickel ore in the roasting furnace is 950℃, and the residence time of the dried material in the fluidized roasting furnace is 6s;

[0068] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 650℃, and the residence time of the primary solid material in the reduction reactor is 40 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.20 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 20%;

[0069] (4) The metallization rate of nickel in the reduced material was 93.08%, and the metallization rate of iron was 15.57%;

[0070] (5) After the secondary solid materials are mixed with the quartz sand agent, they are put into the electric furnace for smelting. The quartz sand contains 93% SiO2 by weight and has a loss on ignition of 0.40%. The mass of the added quartz sand flux accounts for 13% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid materials is adjusted to 1.7:1. The electric furnace smelting temperature is 1560℃ and the smelting time is 60min.

[0071] (6) The nickel-iron alloy contains 28.10% Ni by mass percentage, with a Ni recovery rate of 94.65%, and contains 68.57% TFe by mass percentage, with an Fe recovery rate of 16.88%.

[0072] Example 4

[0073] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0074] (1) The low-grade ferrosilicon-magnesium type laterite nickel ore used in the embodiments of the present invention has a Ni grade of 2.01%, contains 15.70% TFe, 35.63% SiO2, and 27.47% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 30% of the total mass, and contains 12.80% water by mass percentage.

[0075] (2) The silica-magnesia type lateritic nickel ore is preheated to 400℃ in a multi-stage cyclone preheating system, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.10 m³ / s. 3 / kg; The heating temperature of the silica-magnesia type laterite nickel ore in the roasting furnace is 800℃, and the residence time of the dried material in the fluidized roasting furnace is 10s;

[0076] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 600℃, and the residence time of the primary solid material in the reduction reactor is 60 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.10 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 20%;

[0077] (4) The metallization rate of nickel in the reduced material is 94.00%, and the metallization rate of iron is 17.65%;

[0078] (5) After the secondary solid material is mixed with the quartz sand agent, it is put into the electric furnace for smelting. The quartz sand contains 91% SiO2 by weight and has a loss on ignition of 0.50%. The mass of the added quartz sand flux accounts for 9% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid material is adjusted to 1.5:1. The electric furnace smelting temperature is 1580℃ and the smelting time is 45min.

[0079] (6) The nickel-iron alloy contains 30.85% Ni by mass percentage, with a Ni recovery rate of 93.88%, and contains 66.50% TFe by mass percentage, with an Fe recovery rate of 16.07%.

[0080] Example 5

[0081] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0082] (1) The low-grade ferrosilicon-magnesium type laterite nickel ore used in the embodiments of the present invention has a Ni grade of 0.85%, contains 8.47% TFe, 42.54% SiO2, and 34.15% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 38% of the total mass, and contains 14.09% water by weight percentage.

[0083] (2) The preheating temperature of the ferrosilicon-magnesium type laterite nickel ore in the multi-stage cyclone preheating system is 420℃, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.12m³. 3 / kg; The heating temperature of the ferrosilicon-magnesium type laterite nickel ore in the roasting furnace is 820℃, and the residence time of the dried material in the fluidized roasting furnace is 9s;

[0084] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 610℃, and the residence time of the primary solid material in the reduction reactor is 50 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.12 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 26%;

[0085] (4) The metallization rate of nickel in the reduced material was 91.76%, and the metallization rate of iron was 13.90%;

[0086] (5) After the secondary solid materials are mixed with the quartz sand agent, they are put into the electric furnace for smelting. The quartz sand contains 92% SiO2 by weight and has a loss on ignition of 0.60%. The mass of the added quartz sand flux accounts for 8% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid materials is adjusted to 1.4:1. The electric furnace smelting temperature is 1570℃ and the smelting time is 65min.

[0087] (6) The nickel-iron alloy contains 20.70% Ni by mass percentage, with a Ni recovery rate of 91.12%, and contains 74.86% TFe by mass percentage, with an Fe recovery rate of 14.82%.

[0088] Example 6

[0089] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0090] (1) The low-grade ferrosilicon-magnesium type laterite nickel ore used in the embodiments of the present invention has a Ni grade of 1.54%, contains 12.18% TFe, 37.77% SiO2, and 32.65% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 28% of the total mass, and contains 13.60% water by mass percentage.

[0091] (2) The preheating temperature of the ferrosilicon-magnesium type laterite nickel ore in the multi-stage cyclone preheating system is 470℃, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.22m³. 3 / kg; The heating temperature of the ferrosilicon-magnesium type laterite nickel ore in the roasting furnace is 880℃, and the residence time of the dried material in the fluidized roasting furnace is 7s;

[0092] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 640℃, and the residence time of the primary solid material in the reduction reactor is 45 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.30 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 22%;

[0093] (4) The metallization rate of nickel in the reduced material is 92.90%, and the metallization rate of iron is 15.75%;

[0094] (5) After the secondary solid material is mixed with the quartz sand agent, it is put into the electric furnace for smelting. The quartz sand contains 90% SiO2 by weight percentage and has a loss on ignition of 0.80%. The mass percentage of the added quartz sand flux accounts for 19% of the mass percentage of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid material is adjusted to 1.7:1. The electric furnace smelting temperature is 1590℃ and the smelting time is 40min.

[0095] (6) The nickel-iron alloy contains 35.08% Ni by mass percentage, with a Ni recovery rate of 91.55%, and contains 62.01% TFe by mass percentage, with an Fe recovery rate of 13.39%.

[0096] Example 7

[0097] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0098] (1) The low-grade ferrosilicon-magnesium type lateritic nickel ore used in the embodiments of the present invention has a Ni grade of 2.70%, contains 18.46% TFe, 33.79% SiO2, and 26.45% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type lateritic nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 38% of the total mass, and contains 13.84% water by weight percentage.

[0099] (2) The preheating temperature of the ferrosilicon-magnesium type laterite nickel ore in the multi-stage cyclone preheating system is 530℃, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.24 m³ / s. 3 / kg; The heating temperature of the silica-magnesia type laterite nickel ore in the roasting furnace is 970℃, and the residence time of the dried material in the fluidized roasting furnace is 6s;

[0100] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 680℃, and the residence time of the primary solid material in the reduction reactor is 35 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.30 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 25%;

[0101] (4) The metallization rate of nickel in the reduced material was 93.15%, and the metallization rate of iron was 18.82%;

[0102] (5) After the secondary solid materials are mixed with the quartz sand agent, they are put into the electric furnace for smelting. The quartz sand contains 95% SiO2 by weight and has a loss on ignition of 0.35%. The mass of the added quartz sand flux accounts for 11% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid materials is adjusted to 1.6:1. The electric furnace smelting temperature is 1600℃ and the smelting time is 35min.

[0103] (6) The nickel-iron alloy contains 40.52% Ni by mass percentage, with a Ni recovery rate of 92.78%, and contains 57.60% TFe by mass percentage, with an Fe recovery rate of 15.06%.

[0104] Example 8

[0105] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0106] (1) The low-grade ferrosilicon-magnesium type lateritic nickel ore used in the embodiments of the present invention has a Ni grade of 2.28%, contains 14.54% TFe, 31.05% SiO2, and 25.80% MgO by weight percentage. The particle size of the ferrosilicon-magnesium type lateritic nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 37% of the total mass, and contains 14.12% water by weight percentage.

[0107] (2) The silica-magnesia type laterite nickel ore is preheated to 460℃ in a multi-stage cyclone preheating system, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.15m³. 3 / kg; The heating temperature of the silica-magnesia type laterite nickel ore in the roasting furnace is 830℃, and the residence time of the dried material in the fluidized roasting furnace is 9s;

[0108] (3) The temperature of the primary solid material during the reduction reaction in the reduction reactor is 620℃, and the residence time of the primary solid material in the reduction reactor is 50 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.15 m³ / min. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 24%;

[0109] (4) The metallization rate of nickel in the reduced material was 94.25%, and the metallization rate of iron was 18.80%;

[0110] (5) After the secondary solid material is mixed with the quartz sand agent, it is put into the electric furnace for smelting. The quartz sand contains 92% SiO2 by weight and has a loss on ignition of 0.47%. The mass of the added quartz sand flux accounts for 14% of the mass of the laterite nickel ore raw material. The mass ratio of SiO2 / MgO in the secondary solid material is adjusted to 1.7:1. The electric furnace smelting temperature is 1590℃ and the smelting time is 40min.

[0111] (6) The nickel-iron alloy contains 35.80% Ni by mass percentage, with a Ni recovery rate of 92.99%, and contains 61.44% TFe by mass percentage, with an Fe recovery rate of 17.64%.

[0112] Comparative Example 1

[0113] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0114] When secondary solid materials are fed into the electric furnace for smelting, no flux is added to adjust the silicon-magnesium ratio. Under identical experimental conditions, the SiO2 / MgO mass ratio in the secondary solid materials is 1.1:1. This results in difficulty separating slag and iron after electric furnace smelting, and poor slag fluidity. The final nickel-iron alloy contains only 12.75% Ni by mass, with a Ni recovery rate of only 70.40%. It also contains 84.25% TFe by mass, with an Fe recovery rate of 35.56%.

[0115] Comparative Example 2

[0116] A method for producing ferronickel from ferrosilicon-magnesium type laterite nickel ore by selective reduction, simultaneous drying and dehydration, and electric furnace smelting is the same as in Example 1, except that:

[0117] In a reduction reactor at 900℃, the reducing gas was changed to a H2 / CO mixture while all other experimental conditions remained the same. The resulting reduced material from the outlet showed a nickel metallization rate of 98.25% and an iron metallization rate of 85.80%. The final nickel-iron alloy exhibited a Ni recovery rate of 96.54%, a TFe recovery rate of 90.50% by mass, and an Fe recovery rate of 88.03%, but contained only 8.25% Ni by mass.

Claims

1. A method for producing ferronickel from ferrosilicon-magnesia type laterite nickel ore through selective reduction, simultaneous drying and dehydration, and electric furnace smelting, characterized in that... Specifically, the following steps are included: Step (1): Crushing The ferrosilicon-magnesium type lateritic nickel ore is crushed to a particle size ≤1.5mm, with the portion smaller than 0.074mm accounting for 25-40% of the total mass, and fed into the silo; the ferrosilicon-magnesium type lateritic nickel ore has a Ni grade of 0.8-3.0%, contains 7.5-20% TFe, 30-45% SiO2, 20-35% MgO by weight, and has a water content ≤15% by weight. Step (2): Preheating and drying The silica-magnesia type lateritic nickel ore in the silo is fed into a multi-stage cyclone preheating and drying system. The preheating temperature is 400~550℃, and the ratio of the gas volume flow rate to the mass flow rate of the mixture entering the multi-stage cyclone preheating system is 0.10~0.30 m³ / s. 3 / kg, the adsorbed water of the ferrosilicon-magnesium type lateritic nickel ore is removed by the preheated airflow and then fed into the fluidized roasting main furnace heating system for 5~10 s to remove the structural water. The heating temperature is 800~1000℃ to form dry material. The high-temperature flue gas after gas-solid separation of the dry material is returned to the preheating and drying system to continue preheating the ferrosilicon-magnesium type lateritic nickel ore. Step (3): Selective reduction After gas-solid separation, the dried material forms a primary solid material, which is fed into a fluidized bed reduction reactor. Nitrogen and methane or natural gas are introduced into the nitrogen inlet and reducing gas inlet of the fluidized bed reduction reactor, respectively. The primary solid material is in a fluidized state under the action of nitrogen and methane or natural gas, and undergoes a selective reduction reaction with methane at a temperature of 600~700℃ in the reduction reactor to form a reduced material. The metallization rate of nickel in the reduced material is ≥90%, and the metallization rate of iron is ≤20%. After gas-solid separation, the excess methane in the reduced material is returned to the fluidized bed roasting main furnace for combustion and heating. Step (4): Electric furnace smelting The secondary solid material formed after gas-solid separation of the reduced material is mixed with quartz sand or magnesia flux to adjust the silicon-magnesium ratio in the secondary solid material, and then fed into the electric furnace smelting reactor. After smelting, it is discharged from the nickel-iron molten metal outlet and the slag outlet, respectively. After cooling, nickel-iron alloy and slag are obtained. Quartz sand or magnesia flux is added to adjust the mass ratio of SiO2 / MgO in the secondary solid material to (1.4~1.7):

1. The mass percentage of the added quartz sand or magnesia flux is 8~30% of the mass of the laterite nickel ore raw material.

2. The method for producing ferronickel from silica-magnesia type laterite nickel ore through selective reduction, simultaneous drying and dehydration, and electric furnace smelting according to claim 1, characterized in that... In step (3), the residence time of the primary solid material in the reduction reactor is 30-60 min; the ratio of the volumetric flow rate of methane and nitrogen entering the reduction reactor to the mass flow rate of the primary solid material is 0.06-0.40 m³. 3 / kg; the volume concentration of methane gas entering the reduction reactor is 20~30%.

3. The method for producing ferronickel from silica-magnesia type laterite nickel ore through selective reduction, simultaneous drying and dehydration, and electric furnace smelting according to claim 1, characterized in that... In step (4), the electric furnace melting temperature is 1550~1600℃ and the melting time is 30~90 min.

4. The method for producing ferronickel from silica-magnesia type laterite nickel ore through selective reduction, simultaneous drying and dehydration, and electric furnace smelting according to claim 1, characterized in that... In step (4), the nickel-iron alloy contains ≥15% Ni by mass percentage, with a Ni recovery rate ≥90%, ≤80% TFe by mass percentage, and a Fe recovery rate of 10~20%.

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