A device and method for producing nickel-cobalt alloy and molten iron by selective reduction and step smelting of limonite type laterite nickel ore

Abstract

A device and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron belong to the field of mineral processing and metallurgical technology. The device includes a silo, a screw feeder, a multi-stage cyclone preheating and drying system, a flue gas dust removal system, a fluidized bed roasting main furnace heating system, a first cyclone separator, a fluidized bed reduction reactor, a second cyclone separator, a first electric furnace smelting reactor, and a second electric furnace smelting reactor. The method steps are as follows: limonite laterite nickel ore is placed in the silo; it is fed into the multi-stage cyclone preheating and drying system, preheated, and then enters the roasting main furnace for heating, dehydration, and decomposition to form dried material; after gas-solid separation, the solid material enters the reduction reactor, and the high-temperature flue gas is returned to the system for preheating and drying; nitrogen and reducing gas are introduced into the inlet of the reduction reactor respectively, forming reduced material that flows out from the outlet; the solid material after gas-solid separation enters the smelting reactor, and excess gas is burned for heating; the iron-rich slag is melted and reduced, and then discharged after smelting.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing and metallurgical technology, and specifically relates to an apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. Background Technology

[0002] Nickel is an important strategic metal, widely used in stainless steel manufacturing, battery materials, electroplating, and catalysts. With the gradual depletion of sulfide nickel ore resources, attention has turned to the much larger reserves of oxide nickel ore. In recent years, laterite nickel ore has accounted for as much as 70% of smelting applications. Currently, serpentine-type laterite nickel ore is well-utilized in pyrometallurgical processes. However, limonite-type laterite nickel ore is often stockpiled as "idle ore." This ore contains 0.8%–1.3% Ni, 0.1%–0.2% Co, and 40%–50% Fe, and is a nickel-cobalt-iron associated resource.

[0003] Currently, wet processing is the most effective method for treating limonite-type lateritic nickel ore, including reduction roasting-ammonia leaching and sulfuric acid pressure leaching. Reduction roasting-ammonia leaching is gradually being phased out due to its high energy consumption and low metal recovery rate. Sulfuric acid pressure leaching is a mature industrial process for treating limonite-type lateritic nickel ore. Patent CN112322909A discloses a method for extracting valuable metal elements from lateritic nickel ore using sulfuric acid leaching and for acid and alkali regeneration and recycling. This method first mixes lateritic nickel ore powder with sulfuric acid to form a slurry, then performs high-pressure selective leaching. The leaching slurry undergoes thickening separation; the underflow is used as iron concentrate, and the overflow liquid is treated with a pH adjuster for precipitation. Filtration yields nickel-cobalt enrichment, and the filtrate is evaporated and concentrated to form magnesium sulfate crystals.

[0004] Patent CN114507780A discloses a low-cost, low-acid-consumption leaching method for lateritic nickel ore. The method involves mixing limonite-type lateritic nickel ore with sulfuric acid solution to form a slurry, followed by high-pressure acid leaching. The leaching solution is then treated with modified humic soil to adjust the pH, resulting in iron-aluminum slag and a neutralized solution. After adjusting the pH of the neutralized solution, solid-liquid separation is performed to obtain nickel-cobalt hydroxide. This invention utilizes residual acid to leach valuable metals such as nickel and cobalt from the modified humic soil-type lateritic nickel ore, reducing the unit acid consumption of nickel products. However, the process is complex, has a low throughput, and discharges a large amount of acidic leaching residue.

[0005] In general, high-pressure acid leaching is currently the mainstream process for treating limonite-type lateritic nickel ore. However, it suffers from problems such as a long process flow, high production costs, and susceptibility to corrosion and scaling in high-pressure reactors, especially the environmental issues caused by the accumulation of large amounts of leaching residue. Therefore, there is an urgent need to develop an innovative process that can fundamentally avoid the problems associated with acid leaching and achieve the efficient development and utilization of low-grade limonite-type lateritic nickel ore. Summary of the Invention

[0006] To address the problems of high production costs, difficult tailings treatment, and severe equipment corrosion in existing acid leaching processes, this invention provides an apparatus and method for selective reduction and stepwise smelting of limonite-type lateritic nickel ore to produce nickel-cobalt alloy and molten iron. The method involves multi-stage fluidized bed drying and dehydration, followed by fluidized bed selective reduction to reduce nickel and cobalt oxides in the limonite-type lateritic nickel ore to metallic nickel and metallic cobalt with a metallization rate ≥95%, while controlling the reduction of iron oxides to minimal or no reduction to metallic iron, ensuring an iron metallization rate ≤5%. Subsequently, melting and separation of nickel, cobalt, and iron are achieved through stratification to obtain nickel-cobalt alloy and iron-rich slag. The iron-rich slag is further melted and reduced under the action of coke or pulverized coal to obtain molten iron and slag, achieving stepwise recovery and comprehensive utilization of nickel, cobalt, and iron.

[0007] The apparatus for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron of the present invention includes a silo, a screw feeder, a multi-stage cyclone preheating and drying system, a flue gas dust removal system, a fluidized bed roasting main furnace heating system, a first cyclone separator, a fluidized bed reduction reactor, a second cyclone separator, a first electric furnace smelting reactor, and a second electric furnace smelting reactor.

[0008] The multi-stage cyclone preheating and drying system includes a primary cyclone preheater, a secondary cyclone preheater, a tertiary cyclone preheater, and a quaternary cyclone preheater; the flue gas dust removal system includes a dust removal device, an ash hopper, a heat exchanger, an induced draft fan, and a chimney; the fluidized bed roasting main furnace heating system includes a fluidized bed roasting main furnace and a combustion station, where natural gas is burned to generate high-temperature flue gas to heat the materials.

[0009] The silo has a discharge port at the bottom, and the screw feeder has a feed inlet on one side opposite to the silo discharge port and a discharge port on the other side; the first-stage cyclone preheater, second-stage cyclone preheater, third-stage cyclone preheater, and fourth-stage cyclone preheater all have air outlets at the top, feed inlets on one side, and discharge ports at the bottom; the dust removal device has an air inlet on one side, a discharge port on the other side, and an ash hopper at the bottom; the fluidized bed roasting main furnace has a feed inlet on the side, a discharge port on the other side of the top, and a combustion station on one side of the lower part; the first cyclone separator and the second cyclone... Each separation cylinder has a feed inlet on one side, a gas outlet at the top, and a discharge outlet at the bottom; the fluidized bed reduction reactor has a feed inlet on one side of the top, a discharge outlet on the other side of the top, and a nitrogen inlet and a reducing gas inlet at the bottom; the first electric furnace smelting reactor has a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a nickel-cobalt molten metal discharge outlet and a rich iron slag discharge outlet on the side; the second electric furnace smelting reactor has a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a molten iron discharge outlet and a slag discharge outlet on the side.

[0010] The discharge port of the silo is connected to the inlet of the screw feeder. The discharge port of the screw feeder is connected via a pipe to the inlet of the first-stage cyclone preheater in the multi-stage cyclone preheating and drying system. The discharge port of the first-stage cyclone preheater is connected via a pipe to the inlet of the second-stage cyclone preheater. The discharge port of the second-stage cyclone preheater is connected via a pipe to the inlet of the third-stage cyclone preheater. The discharge port of the third-stage cyclone preheater is connected via a pipe to the inlet of the fourth-stage cyclone preheater. The outlet of the first-stage cyclone preheater is connected via a pipeline to the inlet of the fluidized bed roasting main furnace in the fluidized bed roasting main furnace heating system. The outlet of the fluidized bed roasting main furnace is connected via a pipeline to the inlet of the first cyclone separator. The outlet of the first cyclone separator is connected via a pipeline to the inlet of the fluidized bed reduction reactor. The outlet of the fluidized bed reduction reactor is connected via a pipeline to the inlet of the second cyclone separator. The outlet of the second cyclone separator is connected via a pipeline to the inlet of the first electric furnace smelting reactor.

[0011] The outlet of the first-stage cyclone preheater in the multi-stage cyclone preheating system is connected to the inlet of the dust removal device in the flue gas dust removal system via a pipeline. The outlet of the second-stage cyclone preheater in the multi-stage cyclone preheating system is connected to the inlet of the first-stage cyclone preheater via a pipeline. The outlet of the third-stage cyclone preheater is connected to the inlet of the second-stage cyclone preheater via a pipeline. The outlet of the fourth-stage cyclone preheater is connected to the inlet of the third-stage cyclone preheater via a pipeline. The outlet of the first cyclone separator is connected to the inlet of the fourth-stage cyclone preheater in the multi-stage cyclone preheating system via a pipeline. The outlet of the dust removal device is connected to the inlet of the induced draft fan via a pipeline. A heat exchanger is installed in the pipeline between the dust removal device and the induced draft fan. The outlet of the induced draft fan is connected to the chimney via a pipeline. The iron-rich slag outlet of the first electric furnace smelting reactor is connected to the feed inlet of the second electric furnace smelting reactor via a pipeline; the high-temperature flue gas outlets of the first and second electric furnace smelting reactors are connected to the bottom air inlet of the fluidized bed roasting main furnace via pipelines.

[0012] The method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron of the present invention is implemented using the above-mentioned apparatus and specifically includes the following steps:

[0013] (1) Place the limonite-type laterite nickel ore in the silo, start the induced draft fan, and create negative pressure in the dust removal device, multi-stage cyclone preheating system, fluidized roasting main furnace heating system and first cyclone separator. Start the fluidized roasting main furnace heating system to form high-temperature flue gas. Under the action of negative pressure, the high-temperature flue gas passes through the first cyclone separator, multi-stage cyclone preheating system and dust removal device in sequence.

[0014] (2) Start the screw feeder to feed the laterite nickel ore in the silo into the multi-stage cyclone preheating and drying system. After being preheated by the multi-stage cyclone, the laterite nickel ore enters the fluidized roasting main furnace for further heating, dehydration and decomposition to form dried material.

[0015] (3) After the dry material is separated into gas and solid by the first cyclone separator, it forms a primary solid material and enters the fluidized reduction reactor. The high-temperature flue gas is returned to the preheating and drying system to continue preheating and drying the limonite-type laterite nickel ore.

[0016] (4) Nitrogen and reducing gas are introduced into the nitrogen inlet and reducing gas inlet of the fluidized bed reduction reactor, respectively. The solid material is in a state of violent fluidization under the action of nitrogen and reducing gas, and undergoes a reduction reaction with the reducing gas in the fluidized bed reduction reactor. The resulting reduced material flows out from the outlet of the reduction reactor with the gas flow.

[0017] (5) The reduced material flowing out of the outlet of the fluidized reduction reactor enters the second cyclone separator. The secondary solid material after gas-solid separation enters the first electric furnace smelting reactor. The excess reducing gas is returned to the fluidized roasting main furnace for combustion and heating. After the secondary solid material is smelted, it is discharged from the nickel-cobalt water outlet and the iron-rich slag outlet respectively to obtain nickel-cobalt alloy and iron-rich slag.

[0018] (6) After adding coke or pulverized coal to the rich iron slag, it enters the second electric furnace smelting reactor for melting and reduction. After smelting, it is discharged from the iron outlet and the slag outlet respectively. The molten iron is used as qualified pig iron for steelmaking.

[0019] in:

[0020] In step (1), the particle size of the limonite laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 25-50% of the total mass, and the water content is ≤15% by mass percentage.

[0021] In step (2), the temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 450–650℃, 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.

[0022] In step (2), the temperature of the fluidized bed roasting furnace is 800-1000℃.

[0023] In step (2), the main reaction formulas for the removal of adsorbed water from laterite nickel ore during preheating and the removal of structural water during heating are as follows:

[0024] H₂O(l)=H₂O(g) (1)

[0025] 2FeO(OH)=Fe2O3+H2O (2).

[0026] In step (4), the reducing gas is made by mixing H2 and CO with nitrogen.

[0027] In step (4), the temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor is 600–700℃, and the residence time of the solid material in the fluidized bed reduction reactor is 30–60 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor to the molar ratio of Fe2O3 in the solid material is 1:(1.0–1.3), and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor to the mass flow rate of the solid material is 0.06–0.40 m³. 3 / kg.

[0028] In step (4), the metallization rate of nickel and cobalt in the reducing material is ≥95%, and the metallization rate of iron is ≤5%.

[0029] In step (4), the main reaction formula for the reduction reaction is:

[0030] 3Fe2O3+CO / H2=2Fe3O4+CO2 / H2O (3)

[0031] Fe3O4+CO / H2=3FeO+CO2 / H2O (4)

[0032] NiO + CO / H2 = Ni + CO2 / H2O (5)

[0033] CoO+CO / H2=Co+CO2 / H2O (6).

[0034] In addition, some ferrous oxide may undergo a reduction reaction to produce a small amount of metallic iron, such as:

[0035] FeO+CO / H2=Fe+CO2 / H2O (7).

[0036] In step (5), the gas that enters the second cyclone separator along with the reducing material is separated into gas and solid and then enters the burner nozzle, where the unreacted reducing gas is burned as fuel.

[0037] In step (5), the melting temperature of the first electric furnace is 1450-1550℃ and the melting time is 20-40min.

[0038] In step (5), the high-temperature flue gas after the first electric furnace smelting is fed into the fluidized bed roasting main furnace heating system.

[0039] In step (5), the nickel-cobalt alloy contains ≥10% Ni by mass percentage, with a Ni recovery rate ≥90%, ≥1% Co, and a Co recovery rate ≥90%.

[0040] In step (6), the mass ratio of pulverized coal or coke entering the second electric furnace is 20-30% of the mass ratio of the rich iron slag, the smelting temperature of the second electric furnace is 1400-1500℃, the smelting time is 40-60min, the molten iron contains TFe ≥90% by mass percentage, and the Fe recovery rate is ≥90%.

[0041] In step (6), the high-temperature flue gas after melting in the second electric furnace is fed into the fluidized bed roasting main furnace heating system.

[0042] In step (6), the main reaction formula for the melt reduction reaction is:

[0043] FeO(s)=FeO(l) (8)

[0044] FeO(l) + C(s) = Fe(l) + CO(g) (9)

[0045] FeO(l)+[C](l)=Fe(l)+CO(g) (10).

[0046] The basic principle of this invention is that lateritic nickel ore of the limonite type is subjected to multi-stage cyclone drying at 450–650°C and fluidized roasting at 800–1000°C for dehydration and decomposition, thereby removing adsorbed water and structural water from the lateritic nickel ore and transforming goethite FeO(OH) into hematite Fe2O3. Since nickel oxide and cobalt oxide are more prone to reduction reactions than iron oxide, the obtained hematite Fe2O3 is selectively reduced to fusinate FeO in a fluidized state at 600–700°C by controlling the reduction conditions, with a small amount of FeO undergoing over-reduction. The process generates metallic iron (Fe), with a metallization rate of ≤5%. Simultaneously, nickel oxide (NiO) is reduced to metallic Ni with a metallization rate ≥95%, and cobalt oxide (CoO) is reduced to metallic Co with a metallization rate ≥95%. The reduced materials are then smelted in stages. In the first stage, metallic nickel and cobalt are melted and separated from iron oxide to obtain a nickel-cobalt alloy and iron-rich slag. In the second stage of molten reduction, FeO in the iron-rich slag is reduced to metallic iron under the action of coke or pulverized coal. After melting and separation, molten iron and slag are obtained, thus effectively realizing the stepwise recovery and comprehensive utilization of nickel, cobalt, and iron.

[0047] Compared with existing laterite nickel ore processing technologies, the advantages of this invention are as follows:

[0048] (1) This invention provides an apparatus and method for applying multi-stage fluidized bed roasting technology and step-by-step smelting technology to process limonite-type laterite nickel ore. The raw ore is subjected to a three-stage fluidized bed roasting process of drying and preheating, dehydration roasting, and selective reduction to achieve efficient pre-reduction of laterite nickel ore. The pre-reduction product is smelted in two steps to obtain high-grade nickel-cobalt alloy and molten iron. The properties of the products at each stage are easy to precisely control, which solves the problems of unadjustable stage products and difficult metal recovery rate in traditional roasting processes.

[0049] (2) The fluidized reduction stage of the present invention makes full use of the differences in reduction characteristics of iron oxide, nickel oxide and cobalt oxide. Under specific reduction temperature and reducing agent concentration conditions, the iron mineral is reduced to metallic iron, and the nickel and cobalt oxides are completely reduced to metallic nickel and metallic cobalt, which shortens the roasting time and saves the consumption of gas reducing agent and the roasting energy consumption in the pre-reduction stage.

[0050] (3) The first step of the smelting process of the present invention is carried out under the condition of completely limiting the iron metallization rate. No reducing agent is added in this stage. Under the melting conditions, metallic nickel and metallic cobalt are fused with a small amount of metallic iron into the liquid phase. Most of the iron exists in the slag phase in the form of oxides. Then, the second step of smelting and iron extraction is carried out, which greatly improves the grade and recovery rate of nickel and cobalt in nickel-cobalt alloy, improves the quality of nickel-cobalt alloy, and obtains high-grade molten iron for steelmaking, realizing the step-by-step recovery and comprehensive utilization of nickel, cobalt and iron.

[0051] (4) The apparatus and method for processing limonite-type laterite nickel ore of the present invention adopts fluidized bed roasting process to greatly improve the reaction rate. The high-temperature flue gas of the fluidized bed roasting main furnace and electric furnace is recycled. The heat utilization rate of the whole set of equipment is high, and the system energy consumption is greatly reduced compared with the traditional roasting process. Compared with the acid leaching process of laterite nickel ore, the process flow of the present invention is simple, and the slag clinker can be used as a raw material for cement in construction. It is environmentally friendly. At the same time, the apparatus and method of the present invention can make full use of existing large-scale equipment. The technology is mature and reliable, the production efficiency is high, and it is easy to realize industrialization and automation. Attached Figure Description

[0052] Figure 1 A schematic diagram of the apparatus for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron in this embodiment of the invention.

[0053] Among them, 1. hopper, 2. screw feeder, 3. primary cyclone preheater, 4. secondary cyclone preheater, 5. tertiary cyclone preheater, 6. quaternary cyclone preheater, 7. dust removal device, 8. ash hopper, 9. heat exchanger, 10. induced draft fan, 11. chimney, 12. fluidized bed roasting main furnace, 13. combustion station, 14. first cyclone separator, 15. fluidized bed reduction reactor, 16. second cyclone separator, 17. first electric furnace smelting reactor, 18. nickel-cobalt molten iron outlet, 19. iron-rich slag outlet, 20. second electric furnace smelting reactor, 21. molten iron outlet, 22. slag outlet;

[0054] Figure 2 A schematic diagram of the process flow for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron in this embodiment of the invention. Detailed Implementation

[0055] 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.

[0056] The low-grade limonite-type laterite nickel ore used in this embodiment of the invention has a Ni grade of 0.7-1.3%, a Co grade of 0.05-0.30%, and contains 40-50% TFe, 3-5% SiO2, 4-6% Al2O3, 4-6% CaO, and 0.5-5% MgO by weight percentage.

[0057] In the embodiments of the present invention, the nickel-cobalt alloy contains 10-30% Ni and 1-6% Co by mass percentage.

[0058] In this embodiment of the invention, the fluidized bed reduction reactor 15 is provided with a baffle. The top of the baffle is fixed to the top of the fluidized bed reduction reactor 15, and the side of the baffle is fixed to the side of the fluidized bed reduction reactor 15. A gas distribution plate is provided at the bottom of the fluidized bed reduction reactor 15. Below the gas distribution plate are nitrogen inlet and reducing gas inlet, respectively. A gap is provided between the gas distribution plate and the baffle as a channel for the flow of solid materials.

[0059] In the embodiments of the present invention, the reducing gas is produced by mixing H2 and CO generated from coal gasification or natural gas cracking with nitrogen.

[0060] The pulverized coal in the embodiments of the present invention is bituminous coal or anthracite.

[0061] Example 1

[0062] An apparatus for the selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron, such as... Figure 1 As shown, it includes a silo 1, a screw feeder 2, a multi-stage cyclone preheating and drying system, a flue gas dust removal system, a fluidized bed roasting main furnace heating system, a first cyclone separator 14, a fluidized bed reduction reactor 15, a second cyclone separator 16, a first electric furnace smelting reactor 17, and a second electric furnace smelting reactor 20.

[0063] The multi-stage cyclone preheating and drying system includes a primary cyclone preheater 3, a secondary cyclone preheater 4, a tertiary cyclone preheater 5, and a quaternary cyclone preheater 6; the flue gas dust removal system includes a dust removal device 7, an ash hopper 8, a heat exchanger 9, an induced draft fan 10, and a chimney 11; the fluidized bed roasting main furnace heating system includes a fluidized bed roasting main furnace 12 and a combustion station 13, which generates high-temperature flue gas by burning natural gas to heat the materials.

[0064] The bottom of the silo 1 is provided with a discharge port, and the screw feeder 2 is provided with a feed port on one side opposite to the discharge port of the silo 1, and a discharge port on the other side; the first-stage cyclone preheater 3, the second-stage cyclone preheater 4, the third-stage cyclone preheater 5, and the fourth-stage cyclone preheater 6 are all provided with air outlets at the top, feed inlets on one side, and discharge ports at the bottom; the dust removal device 7 is provided with an air inlet on one side, a discharge port on the other side, and an ash hopper 8 at the bottom; the fluidized bed roasting main furnace 12 is provided with a feed inlet on the side, a discharge port on the other side of the top, and a combustion station 13 on one side of the lower part; the first cyclone separator 14 and the second cyclone separator... Each of the cylinders 16 has a feed inlet on one side, a gas outlet at the top, and a discharge outlet at the bottom; the fluidized bed reduction reactor 15 has a feed inlet on one side of the top, a discharge outlet on the other side of the top, and a nitrogen inlet and a reducing gas inlet at the bottom; the first electric furnace smelting reactor 17 has a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a nickel-cobalt molten metal discharge outlet 18 and a rich iron slag discharge outlet 19 on the side; the second electric furnace smelting reactor 20 has a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a molten iron discharge outlet 21 and a slag discharge outlet 22 on the side.

[0065] The discharge port of the silo 1 is connected to the inlet of the screw feeder 2. The discharge port of the screw feeder 2 is connected via a pipe to the inlet of the first-stage cyclone preheater 3 in the multi-stage cyclone preheating and drying system. The discharge port of the first-stage cyclone preheater 3 is connected via a pipe to the inlet of the second-stage cyclone preheater 4. The discharge port of the second-stage cyclone preheater 4 is connected via a pipe to the inlet of the third-stage cyclone preheater 5. The discharge port of the third-stage cyclone preheater 5 is connected via a pipe to the inlet of the fourth-stage cyclone preheater 6. The fourth-stage cyclone preheater in the multi-stage cyclone preheating and drying system... The outlet of device 6 is connected via a pipe to the inlet of the fluidized bed roasting main furnace 12 in the fluidized bed roasting main furnace heating system. The outlet of the fluidized bed roasting main furnace 12 is connected via a pipe to the inlet of the first cyclone separator 14. The outlet of the first cyclone separator 14 is connected via a pipe to the inlet of the fluidized bed reduction reactor 15. The outlet of the fluidized bed reduction reactor 15 is connected via a pipe to the inlet of the second cyclone separator 16. The outlet of the second cyclone separator 16 is connected via a pipe to the inlet of the first electric furnace smelting reactor 17.

[0066] The outlet of the first-stage cyclone preheater 3 in the multi-stage cyclone preheating system is connected to the inlet of the dust removal device 7 in the flue gas dust removal system via a pipeline. The outlet of the second-stage cyclone preheater 4 in the multi-stage cyclone preheating system is connected to the inlet of the first-stage cyclone preheater 3 via a pipeline. The outlet of the third-stage cyclone preheater 5 is connected to the inlet of the second-stage cyclone preheater 4 via a pipeline. The outlet of the fourth-stage cyclone preheater 6 is connected to the inlet of the third-stage cyclone preheater 5 via a pipeline. The outlet of the first cyclone separator 14 is connected to the inlet of the fourth-stage cyclone preheater 6 in the multi-stage cyclone preheating system via a pipeline. The outlet of the dust removal device 7 is connected to the inlet of the induced draft fan 10 via a pipeline. A heat exchanger 9 is installed in the pipeline between the dust removal device 7 and the induced draft fan 10. The outlet of the induced draft fan 10 is connected to the chimney 11 via a pipeline. The fluidized bed reduction reactor 15 is equipped with a baffle. The top of the baffle is fixed to the top of the fluidized bed reduction reactor 15, and the side of the baffle is fixed to the side of the fluidized bed reduction reactor 15. The bottom of the fluidized bed reduction reactor 15 is equipped with a gas distribution plate. Below the gas distribution plate are nitrogen inlet and reducing gas inlet, respectively. There is a gap between the gas distribution plate and the baffle as a channel for the flow of solid materials.

[0067] The iron-rich slag outlet 19 of the first electric furnace smelting reactor 17 is connected to the feed inlet of the second electric furnace smelting reactor 20 via a pipeline; the high-temperature flue gas outlets of the first electric furnace smelting reactor 17 and the second electric furnace smelting reactor 20 are connected to the bottom air inlet of the fluidized bed roasting main furnace 12 via pipelines.

[0068] Example 2

[0069] A method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron is illustrated in the following process flow diagram: Figure 2 As shown, the specific operation method is as follows:

[0070] (1) Place the limonite-type laterite nickel ore in silo 1. The Ni grade is 1.25%, the Co grade is 0.22%, and the weight percentage contains TFe 48.80%, SiO2 3.38%, Al2O3 4.12%, CaO 4.20%, MgO 0.77%. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 45% of the total mass. The water content is 12.90% by mass.

[0071] (2) Start the induced draft fan 10 to create negative pressure in the dust removal device 7, the multi-stage cyclone preheating system, the fluidized bed roasting main furnace heating system, and the first cyclone separator 14. Start the fluidized bed roasting main furnace heating system to generate high-temperature flue gas. Under the action of negative pressure, the high-temperature flue gas passes sequentially through the first cyclone separator 14, the multi-stage cyclone preheating system, and the dust removal device 7. Start the screw feeder 2 to feed the laterite nickel ore in the silo into the multi-stage cyclone preheating and drying system. The ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixed material is 0.30 m³ / s. 3 / kg, the temperature of laterite nickel ore after preheating by a multi-stage cyclone preheating system is 640℃. The preheated material enters the fluidized bed roasting main furnace heating system for further heating and dehydration. The temperature of the fluidized bed roasting main furnace 12 is 990℃, and the material is dried after heating.

[0072] (3) The primary solid material after gas-solid separation in the first cyclone separator 14 enters the fluidized bed reduction reactor 15; the high-temperature flue gas returns to the preheating and drying system to continue preheating and drying the mixture.

[0073] (4) Nitrogen and reducing gas are introduced into the nitrogen inlet and reducing gas inlet of the fluidized bed reduction reactor 15, respectively. The solid material is in a state of vigorous fluidization under the action of nitrogen and reducing gas, and undergoes a reduction reaction with the reducing gas within the fluidized bed reduction reactor 15. The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 700℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 30 min. The molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to the molar ratio of Fe2O3 in the solid material is 1:1.25, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.25 m³. 3 / kg, the metallization rate of nickel in the reducing material is 95.75%, the metallization rate of cobalt is 97.11%, and the metallization rate of iron is 2.05%. The resulting reducing material flows out from the outlet of the fluidized bed reduction reactor 15 with the gas flow.

[0074] (5) The reduced material flowing out of the outlet of the fluidized bed reduction reactor 15 enters the second cyclone separator 16. The secondary solid material after gas-solid separation enters the first electric furnace smelting reactor 17. The gas that enters the second cyclone separator 16 along with the reduced material enters the burner of the combustion station 13 after gas-solid separation. The unreacted reduced gas is used as fuel for combustion. The smelting temperature of the first electric furnace smelting reactor 17 is 1550℃ and the smelting time is 20min. After smelting, the nickel-cobalt alloy and the iron-rich slag are discharged from the nickel-cobalt water outlet 18 and the iron-rich slag outlet 19, respectively, to obtain the nickel-cobalt alloy and the iron-rich slag. The nickel-cobalt alloy contains 28.70% Ni by mass percentage, with a Ni recovery rate of 92.32%, and contains 5.23% Co, with a Co recovery rate of 95.64%.

[0075] (6) After adding coke, the rich iron slag enters the second electric furnace smelting reactor 20 for melting and reduction. The amount of coke added accounts for 30% of the mass of the rich iron slag. The melting temperature of the second electric furnace smelting reactor 20 is 1500℃ and the melting and reduction time is 50min. After melting, the molten iron is discharged from the iron outlet 21 and the slag outlet 22 respectively. The molten iron contains 92.75% TFe by mass percentage and the Fe recovery rate is 93.08%. After cooling, the molten iron is used as qualified pig iron for steelmaking. The high-temperature flue gas after melting in the first electric furnace smelting reactor 17 and the second electric furnace smelting reactor 20 is fed into the fluidized bed roasting main furnace heating system.

[0076] Example 3

[0077] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0078] (1) The limonite-type laterite nickel ore has a Ni grade of 0.71%, a Co grade of 0.06%, and contains 40.05% TFe, 4.75% SiO2, 4.99% Al2O3, 5.65% CaO, and 1.72% MgO by weight. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 40% of the total mass. The water content is 12.75% by mass.

[0079] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 450℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.10 m³ / s. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 800℃;

[0080] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 600℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 50 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.05, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.15 m³ / s. 3 / kg;

[0081] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 97.01%, the metallization rate of cobalt is 98.55%, and the metallization rate of iron is 4.85%.

[0082] (5) The melting temperature of the first electric furnace melting reactor 17 is 1450℃ and the melting time is 40min. The nickel-cobalt alloy contains 12.80% Ni by mass percentage, with a Ni recovery rate of 96.00%, and contains 1.02% Co, with a Co recovery rate of 90.53%.

[0083] (6) The melting temperature of the second electric furnace melting reactor 20 is 1400℃, the melting reduction time is 60min, the amount of pulverized coal added accounts for 22% of the mass percentage of rich iron slag, the molten iron contains 90.33% TFe by mass percentage, and the Fe recovery rate is 90.06%.

[0084] Example 4

[0085] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0086] (1) The limonite-type laterite nickel ore has a Ni grade of 1.02%, a Co grade of 0.17%, and contains 46.06% TFe, 3.99% SiO2, 5.00% Al2O3, 4.94% CaO, and 1.53% MgO by weight. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 35% of the total mass. The water content is 13.02% by weight.

[0087] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 530℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.15m³. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 930℃;

[0088] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 620℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 45 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.15, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.12 m³ / s. 3 / kg;

[0089] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 96.80%, the metallization rate of cobalt is 97.63%, and the metallization rate of iron is 1.17%.

[0090] (5) The melting temperature of the first electric furnace melting reactor 17 is 1520℃ and the melting time is 25min. The nickel-cobalt alloy contains 20.66% Ni by mass percentage, with a Ni recovery rate of 92.52%, and contains 3.60% Co, with a Co recovery rate of 96.63%.

[0091] (6) The melting temperature of the second electric furnace melting reactor 20 is 1470℃, the melting reduction time is 50min, the amount of pulverized coal added accounts for 25% of the mass percentage of rich iron slag, the molten iron contains 92.01% TFe by mass percentage, and the Fe recovery rate is 92.09%.

[0092] Example 5

[0093] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0094] (1) The limonite-type laterite nickel ore has a Ni grade of 0.88%, a Co grade of 0.13%, and contains 42.90% TFe, 4.55% SiO2, 5.80% Al2O3, 5.63% CaO, and 4.07% MgO by weight percentage. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 25% of the total mass. The water content is 12.80% by weight percentage.

[0095] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 480℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.18m³. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 880℃;

[0096] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 650℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 40 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.10, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.18 m³. 3 / kg;

[0097] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 97.80%, the metallization rate of cobalt is 96.36%, and the metallization rate of iron is 2.88%.

[0098] (5) The melting temperature of the first electric furnace melting reactor 17 is 1470℃ and the melting time is 30min. The nickel-cobalt alloy contains 14.65% Ni by mass percentage, with a Ni recovery rate of 91.41%, and contains 2.26% Co, with a Co recovery rate of 95.64%.

[0099] (6) The melting temperature of the second electric furnace melting reactor 20 is 1420℃, the melting reduction time is 55min, the coke addition is 30% of the mass percentage of rich iron slag, the molten iron contains 96.43% TFe by mass percentage, and the Fe recovery rate is 90.62%.

[0100] Example 6

[0101] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0102] (1) The limonite-type laterite nickel ore has a Ni grade of 1.15%, a Co grade of 0.20%, and contains 47.55% TFe, 3.63% SiO2, 4.28% Al2O3, 4.66% CaO, and 2.08% MgO by weight. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 30% of the total mass. The water content is 13.43% by mass.

[0103] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 600℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.25m³. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 960℃;

[0104] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 640℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 35 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.20, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.30 m³ / s. 3 / kg;

[0105] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 94.50%, the metallization rate of cobalt is 97.77%, and the metallization rate of iron is 3.26%.

[0106] (5) The melting temperature of the first electric furnace melting reactor 17 is 1490℃ and the melting time is 25min. The nickel-cobalt alloy contains 23.60% Ni by mass percentage, with a Ni recovery rate of 92.41%, and contains 4.47% Co, with a Co recovery rate of 97.13%.

[0107] (6) The melting temperature of the second electric furnace melting reactor 20 is 1440℃, the melting reduction time is 50min, the coke addition accounts for 24% of the mass percentage of the rich iron slag, the molten iron contains 91.22% TFe by mass percentage, and the Fe recovery rate is 91.25%.

[0108] Example 7

[0109] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0110] (1) The limonite-type laterite nickel ore has a Ni grade of 0.95%, a Co grade of 0.18%, and contains 44.87% TFe, 4.20% SiO2, 5.65% Al2O3, 4.88% CaO, and 3.01% MgO by weight. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 40% of the total mass. The water content is 14.09% by mass.

[0111] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 500℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.15m³. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 900℃;

[0112] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 670℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 35 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.30, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.20 m³ / s. 3 / kg;

[0113] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 97.13%, the metallization rate of cobalt is 98.52%, and the metallization rate of iron is 3.27%.

[0114] (5) The melting temperature of the first electric furnace melting reactor 17 is 1480℃ and the melting time is 35min. The nickel-cobalt alloy contains 18.60% Ni by mass percentage, with a Ni recovery rate of 95.99%, and contains 3.55% Co, with a Co recovery rate of 96.83%.

[0115] (6) The melting temperature of the second electric furnace melting reactor 20 is 1450℃, the melting reduction time is 50min, the amount of pulverized coal added accounts for 28% of the mass percentage of rich iron slag, the molten iron contains 93.11% TFe by mass percentage, and the Fe recovery rate is 90.19%.

[0116] Example 8

[0117] An apparatus and method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron. The apparatus structure is the same as in Example 1, and the method is the same as in Example 2, except that:

[0118] (1) The limonite-type laterite nickel ore has a Ni grade of 1.21%, a Co grade of 0.24%, and contains 49.00% TFe, 3.52% SiO2, 4.60% Al2O3, 4.22% CaO, and 1.85% MgO by weight. The particle size of its solid part is ≤1.5mm, of which the part with a particle size less than 0.074mm accounts for 35% of the total mass. The water content is 13.99% by weight.

[0119] (2) The temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 550℃, and the ratio of the gas volume flow rate of the cyclone preheating system to the mass flow rate of the mixture is 0.20 m³ / s. 3 / kg, the temperature of the fluidized bed roasting main furnace 12 is 950℃;

[0120] (3) The temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor 15 is 660℃, and the residence time of the solid material in the fluidized bed reduction reactor 15 is 42 min; the molar ratio of the total amount of H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:1.20, and the ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor 15 to the mass flow rate of the solid material is 0.16 m³. 3 / kg;

[0121] (4) The metallization rate of nickel in the reduced material discharged from the fluidized bed reduction reactor 15 is 96.82%, the metallization rate of cobalt is 97.49%, and the metallization rate of iron is 4.01%.

[0122] (5) The melting temperature of the first electric furnace melting reactor 17 is 1510℃ and the melting time is 30min. The nickel-cobalt alloy contains 25.60% Ni by mass percentage, with a Ni recovery rate of 95.26%, and contains 5.20% Co, with a Co recovery rate of 97.61%.

[0123] (6) The melting temperature of the second electric furnace melting reactor 20 is 1460℃, the melting reduction time is 55min, the amount of pulverized coal added accounts for 40% of the mass percentage of rich iron slag, the molten iron contains 92.54% TFe by mass percentage, and the Fe recovery rate is 92.78%.

[0124] Comparative Example 1

[0125] The apparatus is the same as in Example 1, and the raw materials, methods, and steps are the same as in Example 2, except that:

[0126] The solid material undergoes reduction reaction in fluidized bed reduction reactor 15 at a temperature of 850℃, with a residence time of 40 min. The molar ratio of total H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:0.3. With other operating conditions remaining constant, the reduced material discharged from the outlet of the fluidized bed reduction reactor 15 exhibits a nickel metallization rate of 96.92%, a cobalt metallization rate of 98.25%, and an iron metallization rate of 80.75%. The resulting nickel-cobalt alloy contains only 8.09% Ni by mass, with a Ni recovery rate of 97.26%, and 1.43% Co, with a Co recovery rate of 97.68%. The molten iron contains 91.22% TFe by mass, but the Fe recovery rate is only 68.75%.

[0127] Comparative Example 2

[0128] The apparatus is the same as in Example 1, and the raw materials, methods, and steps are the same as in Example 2, except that:

[0129] The solid material undergoes reduction reaction in fluidized bed reduction reactor 15 at a temperature of 950℃, with a residence time of 50 min. The molar ratio of total H2 and CO in the reducing gas entering the fluidized bed reduction reactor 15 to Fe2O3 in the solid material is 1:0.32. With other operating conditions remaining constant, the reduced material discharged from the outlet of the fluidized bed reduction reactor 15 exhibits a nickel metallization rate of 99.80%, a cobalt metallization rate of 99.22%, and an iron metallization rate of 88.37%. The resulting nickel-cobalt alloy contains only 6.25% Ni by mass, with a Ni recovery rate of 97.42%, and only 1.10% Co, with a Co recovery rate of 97.80%. The molten iron contains 90.80% TFe by mass, but the Fe recovery rate is only 61.05%.

[0130] Comparative Example 3

[0131] The apparatus is the same as in Example 1, and the raw materials, methods, and steps are the same as in Example 2, except that:

[0132] The secondary solid material after gas-solid separation in the second cyclone separator 16 does not enter the first electric furnace smelting reactor 17, but is directly fed into the second electric furnace smelting reactor 20. If all other operating conditions are the same, nickel-cobalt alloy products cannot be obtained. After nickel-cobalt smelting, it enters the molten iron. The final molten iron contains 90.25% TFe by mass percentage, with an Fe recovery rate of 94.10%. The Ni content in the molten iron is only 2.32%, and the Co content is only 0.41%. The stepwise recovery of iron, cobalt, and nickel cannot be achieved.

Claims

1. A method for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron, characterized in that, Specifically, the following steps are included: (1) Place the limonite-type laterite nickel ore in the silo, start the induced draft fan, and create negative pressure in the dust removal device, multi-stage cyclone preheating system, fluidized bed roasting main furnace heating system and first cyclone separator. Start the fluidized bed roasting main furnace heating system to generate high-temperature flue gas. Under the action of negative pressure, the high-temperature flue gas passes through the first cyclone separator, multi-stage cyclone preheating system and dust removal device in sequence. (2) Start the screw feeder to feed the laterite nickel ore in the silo into the multi-stage cyclone preheating and drying system. After being preheated by the multi-stage cyclone, the laterite nickel ore enters the fluidized roasting main furnace for further heating, dehydration and decomposition to form dried material. (3) After the dry material is separated into gas and solid by the first cyclone separator, it forms a primary solid material and enters the fluidized bed reduction reactor; the high-temperature flue gas is returned to the preheating and drying system to continue to preheat and dry the limonite-type laterite nickel ore. (4) Nitrogen and reducing gas are introduced into the nitrogen inlet and reducing gas inlet of the fluidized bed reduction reactor, respectively. The reducing gas is made by mixing H2 and CO with nitrogen. The solid material is in a state of vigorous fluidization under the action of nitrogen and reducing gas, and undergoes a reduction reaction with the reducing gas in the fluidized bed reduction reactor. The molar ratio of the total amount of H2 and CO in the reducing gas to Fe2O3 in the solid material is 1:1.0~1.

3. The ratio of the volumetric flow rate of the reducing gas entering the fluidized bed reduction reactor to the mass flow rate of the solid material is 0.06~0.40 m³. 3 / kg, the temperature of the solid material during the reduction reaction in the fluidized bed reduction reactor is 600~700℃, the residence time is 30~60min, and the resulting reduced material flows out from the outlet of the reduction reactor with the gas flow. The metallization rate of nickel and cobalt in the reduced material is ≥95%, and the metallization rate of iron is ≤5%. (5) The reduced material flowing out of the outlet of the fluidized bed reduction reactor enters the second cyclone separator. The secondary solid material after gas-solid separation enters the first electric furnace smelting reactor. The smelting temperature of the first electric furnace is 1450~1550℃ and the smelting time is 20~40min. The excess reducing gas is returned to the fluidized bed roasting main furnace for combustion and heating. After the secondary solid material is smelted, it is discharged from the nickel-cobalt water outlet and the iron-rich slag outlet, respectively, to obtain nickel-cobalt alloy and iron-rich slag. (6) After adding coke or pulverized coal, the iron-rich slag enters the second electric furnace smelting reactor for melting and reduction. After smelting, it is discharged from the iron outlet and the slag outlet respectively. The apparatus for selective reduction and stepwise smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron includes a silo, a screw feeder, a multi-stage cyclone preheating and drying system, a flue gas dust removal system, a fluidized bed roasting main furnace heating system, a first cyclone separator, a fluidized bed reduction reactor, a second cyclone separator, a first electric furnace smelting reactor, and a second electric furnace smelting reactor. The multi-stage cyclone preheating and drying system includes a primary cyclone preheater, a secondary cyclone preheater, a tertiary cyclone preheater, and a quaternary cyclone preheater; the flue gas dust removal system includes a dust removal device, an ash hopper, a heat exchanger, an induced draft fan, and a chimney; the fluidized bed roasting main furnace heating system includes a fluidized bed roasting main furnace and a combustion station.

2. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In the apparatus for selective reduction and stepwise smelting of limonite-type laterite nickel ore to produce nickel-cobalt alloy and molten iron, the bottom of the silo has a discharge port, and the screw feeder has a feed inlet on one side opposite the silo discharge port and a discharge port on the other side; the first-stage, second-stage, third-stage, and fourth-stage cyclone preheaters all have air outlets at the top, feed inlets on one side, and discharge ports at the bottom; the dust removal device has an air inlet on one side, a discharge port on the other side, and an ash hopper at the bottom; the fluidized bed roasting main furnace has a feed inlet on the side, a discharge port on the other side of the top, and a discharge port on one side of the lower part. It has a combustion station; the first and second cyclone separators are equipped with a feed inlet on one side, a gas outlet at the top, and a discharge outlet at the bottom; the fluidized bed reduction reactor is equipped with a feed inlet on one side of the top, a discharge outlet on the other side of the top, and a nitrogen inlet and a reducing gas inlet at the bottom; the first electric furnace smelting reactor is equipped with a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a nickel-cobalt molten metal discharge outlet and a rich iron slag discharge outlet on the side; the second electric furnace smelting reactor is equipped with a feed inlet on one side of the top, a high-temperature flue gas outlet on the other side of the top, and a molten iron discharge outlet and a slag discharge outlet on the side.

3. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In the apparatus for selective reduction and stepwise smelting of limonite-type laterite nickel ore to produce nickel-cobalt alloy and molten iron, the outlet of the silo is connected to the inlet of a screw feeder. The outlet of the screw feeder is connected via a pipeline to the inlet of the first-stage cyclone preheater in a multi-stage cyclone preheating and drying system. The outlet of the first-stage cyclone preheater is connected via a pipeline to the inlet of the second-stage cyclone preheater. The outlet of the second-stage cyclone preheater is connected via a pipeline to the inlet of the third-stage cyclone preheater. The outlet of the third-stage cyclone preheater is connected via a pipeline to the inlet of the fourth-stage cyclone preheater. The outlet of the fourth-stage cyclone preheater in the multi-stage cyclone preheating and drying system is connected to the inlet of the fluidized bed roasting main furnace in the fluidized bed roasting main furnace heating system via a pipeline. The outlet of the fluidized bed roasting main furnace is connected to the inlet of the first cyclone separator via a pipeline. The outlet of the first cyclone separator is connected to the inlet of the fluidized bed reduction reactor via a pipeline. The outlet of the fluidized bed reduction reactor is connected to the inlet of the second cyclone separator via a pipeline. The outlet of the second cyclone separator is connected to the inlet of the first electric furnace smelting reactor via a pipeline. The outlet of the first-stage cyclone preheater in the multi-stage cyclone preheating system is connected to the inlet of the dust removal device in the flue gas dust removal system via a pipeline. The outlet of the second-stage cyclone preheater in the multi-stage cyclone preheating system is connected to the inlet of the first-stage cyclone preheater via a pipeline. The outlet of the third-stage cyclone preheater is connected to the inlet of the second-stage cyclone preheater via a pipeline. The outlet of the fourth-stage cyclone preheater is connected to the inlet of the third-stage cyclone preheater via a pipeline. The outlet of the first cyclone separator is connected to the inlet of the fourth-stage cyclone preheater in the multi-stage cyclone preheating system via a pipeline. The outlet of the dust removal device is connected to the inlet of the induced draft fan via a pipeline. A heat exchanger is installed in the pipeline between the dust removal device and the induced draft fan. The outlet of the induced draft fan is connected to the chimney via a pipeline. The iron-rich slag outlet of the first electric furnace smelting reactor is connected to the feed inlet of the second electric furnace smelting reactor via a pipeline; the high-temperature flue gas outlets of the first and second electric furnace smelting reactors are connected to the bottom air inlet of the fluidized bed roasting main furnace via pipelines.

4. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In step (1), the particle size of the limonite laterite nickel ore is ≤1.5mm, of which the portion with a particle size less than 0.074mm accounts for 25~50% of the total mass, and the water content is ≤15% by mass percentage.

5. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In step (2), the temperature of the laterite nickel ore after preheating by the multi-stage cyclone preheating system is 450~650℃, and the ratio of the gas volume flow rate entering the multi-stage cyclone preheating system to the mass flow rate of the mixture is 0.10~0.30 m³ / s. 3 / kg; The temperature of the fluidized bed roasting furnace is 800~1000℃.

6. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In step (5), the gas that enters the second cyclone separator along with the reducing material is separated into gas and solid and then enters the burner nozzle, where the unreacted reducing gas is used as fuel for combustion; the high-temperature flue gas after the first electric furnace smelting is fed into the fluidized bed roasting main furnace heating system.

7. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In step (5), the nickel-cobalt alloy contains ≥10% Ni by mass percentage, with a Ni recovery rate ≥90%, ≥1% Co, and a Co recovery rate ≥90%.

8. The method for selective reduction-step smelting of limonite laterite nickel ore to produce nickel-cobalt alloy and molten iron according to claim 1, characterized in that, In step (6), the mass ratio of pulverized coal or coke entering the second electric furnace is 20-30% of the mass of rich iron slag, the smelting temperature of the second electric furnace is 1400-1500℃, the smelting time is 40-60 min, the molten iron contains TFe ≥90% by mass percentage, and the Fe recovery rate is ≥90%; the high-temperature flue gas after smelting in the second electric furnace is fed into the fluidized bed roasting main furnace heating system.

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