A system and process for producing nickel by smelting laterite nickel ore in a coal-based roasting-reducing electric furnace

Abstract

The present application belongs to the technical field of metallurgy and mineral processing suspension fluidization roasting, and particularly relates to a system and process for producing nickel by coal-based roasting reduction electric furnace smelting of laterite nickel ore. The system comprises a feeding drying unit, a preheating drying and crushing unit, a heat supply heating unit, a coal-based pre-reduction unit, an electric furnace smelting waste heat recovery unit, a dust removal, powder conveying and desulfurization unit, and the laterite nickel ore is processed by the "dry powder crushing, coal suspension roasting, coal-based pre-reduction, and ore-smelting electric furnace" technology. The present application has strong adaptability to raw materials, can produce high-value products from cheap resources, and adopts multiple energy-saving technologies in the new process to greatly reduce energy consumption and realize efficient use of energy. The present application makes up for the limitations and deficiencies of the traditional RKEF process, can reduce process energy consumption, improve resource recovery rate, provides a new innovative breakthrough direction for efficient utilization of laterite nickel ore resources for smelting nickel-iron alloy, and can greatly improve the economic value of the development and utilization of such resources.

Description

Technical Field

[0001] This invention belongs to the field of suspension fluidized roasting technology in metallurgy and mineral processing, specifically relating to a system and process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore. Background Technology

[0002] Nickel is a silvery, lustrous ferromagnetic metallic element with excellent properties such as corrosion resistance, high hardness, good ductility, high temperature resistance, and oxidation resistance. It is a key raw material for the production of stainless steel, alloy steel, ternary power batteries, electroplating and other materials. It is widely used in metallurgy, chemical industry, construction, machinery and navigation and other fields. It is an important strategic material for national economic development and has always been listed as a strategic metal by the state.

[0003] Since the mid-1980s, nickel has been widely used. Stainless steel has been the main driver of nickel consumption. Nickel demand continues to be driven by the growth in stainless steel production, particularly in Western Europe, Japan, and Southeast Asian countries. In recent years, the application and development of nickel in the steel industry, magnetic industry, military, non-ferrous metals, precious metals, special alloys, hydrogen storage materials, special nickel powder, new nickel-coated composite materials, batteries, medical and health applications, and nickel sulfate have attracted considerable attention. Nickel possesses excellent mechanical strength, ductility, and chemical stability, making it an indispensable metal for industry and the development of modern human civilization, and holding an extremely important position in national economic development.

[0004] Nickel and iron are both common elements found in meteorites and are widely distributed in the Earth's crust and core. Global nickel resources are abundant, ranking fifth in abundance on Earth, with the highest concentration found in the core, where it forms a natural nickel-iron alloy. Nickel ore constitutes only 0.018% of the Earth's crust. There are two types of exploitable nickel resources worldwide: sulfide deposits and laterite nickel ore.

[0005] Nickel sulfide ore resources account for 40% of the world's total nickel reserves, while laterite nickel ore resources account for 60%. Due to mature extraction processes for sulfide ore, 60% of nickel production comes from sulfide ore. However, the world's exploitable sulfide ore resources are dwindling, and the exploration and construction cycles for sulfide ore are lengthy, making development and utilization relatively difficult. In contrast, laterite nickel ore resources are abundant, mining costs are low, and beneficiation processes are mature, allowing the production of various intermediate products such as nickel oxide, nickel sulfate, and ferronickel. The ore deposits are located near the coast, facilitating transportation; therefore, the development and utilization of laterite nickel ore has significant practical implications.

[0006] There are three main processes for extracting nickel metal from laterite nickel ore: hydrometallurgy (electrolysis), pyrometallurgy (electric furnace method), and pyrometallurgy (blast furnace method). The main pyrometallurgical processes for producing ferronickel are blast furnace smelting and electric furnace smelting. However, blast furnace smelting is highly polluting and energy-intensive; therefore, the Chinese government banned the production of low-grade ferronickel using blast furnaces in 2007. The rotary kiln-electric furnace process (RKEF method) has gradually replaced traditional ferronickel production processes due to its simplicity and high productivity, becoming the primary method for ferronickel production today.

[0007] However, the biggest drawback of the rotary kiln-electric furnace process (RKEF method) for processing laterite nickel ore is its high energy consumption. Electricity consumption alone accounts for about 50% of the operating cost when using electric furnace smelting (because it uses electricity as the main heat energy, it generally requires 7,000-8,000 kWh of electricity to produce one ton of nickel iron). In addition, the fuel consumption of the drying and roasting pretreatment processes before smelting nickel oxide ore can be added, and the energy cost in the operating cost may account for more than 65%. my country's power supply is constantly tight, and my country has very strict regulations on high power-consuming industries. Moreover, once the power supply in the region where the production enterprise is located is tight, the first to be affected is the power cut to the electric furnace, which is a major power consumer, causing production to be abnormal. In addition, the pyrometallurgical process has certain requirements on the nickel grade of the laterite ore being processed. For every 1% decrease in the nickel content of the ore, the production cost increases by about 3% to 4%. Secondly, the output of electric arc furnace smelting of nickel pig iron is relatively low. A single 25,000 KW electric arc furnace can produce about 25,000 tons of nickel pig iron with a nickel content of 14% per year, which is far from meeting the large demand for nickel metal caused by the explosive growth of my country's stainless steel industry in recent years.

[0008] my country is a country with relatively scarce nickel resources, and relies heavily on imports. As the world's largest importer of nickel ore and nickel metal, it is of great practical significance to research and explore new processes suitable for nickel metal production, based on the characteristics of different processes for extracting nickel metal from nickel ore, to ensure the supply of nickel resources necessary for the sustainable and healthy development of my country's stainless steel and special steel industries. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention proposes a system and process for coal-based suspension roasting and pre-reduction electric furnace smelting. It utilizes suspension fluidized bed roasting technology to study a process for processing laterite nickel ore to smelt nickel-iron alloys. The process involves "crushing, drying, coal-based fluidized bed roasting, coal-based pre-reduction, and electric arc furnace" to process laterite nickel ore.

[0010] A system for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes a feeding and drying unit, a preheating, drying and pulverizing unit, a heating unit, a coal-based pre-reduction unit, an electric furnace smelting waste heat recovery unit, and a dust removal, powder conveying and desulfurization unit.

[0011] The feeding and drying unit includes a raw ore feeding belt conveyor 1, a drying rotary kiln 2, a conveyor belt 3, a storage bin 4, a quantitative feeder 5, and a feeding airlock device 6; the raw ore feeding belt conveyor 1, the drying rotary kiln 2, and the conveyor belt 3 are connected together, and the conveyor belt 3, the storage bin 4, the quantitative feeder 5, and the feeding airlock device 6 are connected in sequence.

[0012] The preheating, drying and pulverizing unit includes a vertical mill 7, a denitrification reactor 8, a primary cyclone preheater 9, and a secondary cyclone preheater 10; the feeding airlock device 6 is connected to the vertical mill 7, the vertical mill 7 is connected to the denitrification reactor 8 and the primary cyclone preheater 9 through a flue, and the primary cyclone preheater 9 is connected to the secondary cyclone preheater 10 through a flue.

[0013] The heating unit includes a suspension roasting main furnace 11, a coal-fired hot air furnace 12, and a cyclone heater 13; the secondary cyclone preheater 10 is connected to the suspension roasting main furnace 11 and the cyclone heater 13 through a flue, and the suspension roasting main furnace 11 is connected to the coal-fired hot air furnace 12 through a flue.

[0014] The coal-based pre-reduction unit includes a gas lock valve 14, a reduction reactor 15, a material sealing valve 16, and a material storage distributor 17; the cyclone heater 13 is connected to the gas lock valve 14 through a flue, and the reduction reactor 15 is connected to the gas lock valve 14, the material sealing valve 16, and the material storage distributor 17 through a flue.

[0015] The electric furnace smelting waste heat recovery unit includes an electric arc furnace 18, a cooling heat exchange device 19, and an exhaust pipe 20; the material distribution device 17 is connected to the electric arc furnace 18 through a feeding pipe, the electric arc furnace 18 is connected to the cooling heat exchange device 19 and the exhaust pipe 20, the cooling heat exchange device 19 is connected to the drying rotary kiln 2 through a flue, and the exhaust pipe 20 is connected to the coal-fired hot blast stove 12 through a flue.

[0016] The dust removal, powder conveying, and desulfurization unit includes an exhaust fan 21, an electrostatic precipitator 22, a powder conveyor 23, a bag filter 24, an induced draft fan 25, and a desulfurization tower 26. The primary cyclone preheater 9 is connected in sequence to the exhaust fan 21, the drying rotary kiln 2, and the electrostatic precipitator 22 via a flue. The ash hopper of the electrostatic precipitator 22 is connected to the powder conveyor 23. The powder conveyor 23 is connected in sequence to the bag filter 24 and the inlet flue of the electrostatic precipitator 22 via a flue. The discharge pipe of the bag filter 24 is connected to the cone of the cyclone heater 13. The electrostatic precipitator 22 is connected to the induced draft fan 25 via a flue. The induced draft fan 25 is connected to the desulfurization tower 26.

[0017] Furthermore, the feeding airlock device is a screw feeder or an airlock material sealing valve.

[0018] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting, employing the aforementioned system, specifically includes the following steps:

[0019] Step (1): The laterite nickel ore is crushed to a water content of 30% to 40% and then fed into a drying rotary kiln via a feeding belt conveyor for drying. The dried laterite nickel ore with a water content of 15% to 25% is then fed into a powder vertical mill via a conveyor belt, storage bin, quantitative feeder, and feeding airlock device.

[0020] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill for powder grinding and classification circulation to obtain the powder product of the vertical mill; the particle size of the powder product is ≤1.5mm, and the distribution in the 0.8mm~1mm range is greater than 50%; the medium for classification circulation is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 380~420℃, negative pressure -5~-6kPa, and the flue gas temperature at the outlet of the vertical mill is 100~150℃, negative pressure -11~-12kPa;

[0021] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation. The tangential inlet negative pressure of the primary cyclone preheater is -12 to -12.5 kPa. The separated solid material is carried by the high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material. The separation efficiency of the cyclone preheater is over 90%, and the preheating time is 10s to 30s. The tangential inlet negative pressure of the secondary cyclone preheater is -2.5 to -3.5 kPa. The separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material.

[0022] Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 700-1000℃ and the time is 1-3min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0023] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed by the storage distributor and then enters the electric arc furnace for smelting to obtain the smelted products ferronickel and nickel slag.

[0024] Step (6): After the cold air indirectly exchanges heat with the smelted products ferronickel and nickel slag, it is sent into the drying rotary kiln through the exhaust fan;

[0025] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater to enter the pre-reduction reaction described in step 5. The negative pressure at the inlet of the exhaust fan is -12.5 to -13.5 kPa.

[0026] Step (8): The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal.

[0027] Furthermore, the true density of the laterite nickel ore in step 1 is 2.2–3 t / m³. 3 The particle size is less than 30 mm.

[0028] Furthermore, in step 2, the denitrification treatment adopts a selective catalytic reduction (SCR) process, the inlet temperature of the denitrification reactor is 400℃~440℃, the inlet negative pressure is -4~-5kPa, and the reducing agent of the catalytic reduction (SCR) process is urea.

[0029] Furthermore, in step 4, the coal used in the hot blast stove is bituminous coal, which is pulverized by a vertical mill and then transported to the hot blast stove. The true density is 1.27–1.33 t / m³. 3 The coal used in the hot blast stove has a coal particle size of -200 mesh and a content of 70-90%. The hot blast stove is a lined furnace with a pulverized coal inlet pressure of 3000-5000 Pa and a pulverized coal inlet solid-gas ratio of 0.5-1.2. The primary combustion air fan of the burner has a flow rate of 50000-75000 Nm³ / h, a pressure rise of 5000-7000 Pa, a calorific value of 5000-550000 kcal / h, and a high-temperature hot air outlet temperature. The temperature ranges from 750 to 1100℃, the outlet air velocity is 17 to 25 m / s, the outlet flue gas flow rate is 450,000 to 660,000 Nm³ / h, and the outlet pressure is -300 to -500 Pa. Slag is discharged intermittently, continuously, or at regular intervals, with a slag discharge rate of 150 to 300 kg / h and a slag discharge temperature of 200 to 500℃. The outlet temperature of the high-temperature hot air in step 4 can be adjusted by adding cold air, with a cold air volume of 28,000 to 100,000 m³ / h.

[0030] Furthermore, in step 5, the smelting temperature of the electric arc furnace is 750–950°C; in step 5, the reducing agent used in the pre-reduction reaction is pulverized coal, and the CO, CO2 and other gases generated by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion.

[0031] The nickel slag in step 5 can be used to manufacture bricks.

[0032] Furthermore, in step 6, the indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat-exchanged by the serpentine cooler in an indirect heat exchange manner on the high-temperature nickel iron and nickel slag. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide drying hot air for the drying rotary kiln, thereby realizing the recycling of energy.

[0033] Furthermore, after dust removal in step 8, ultra-low emissions can be achieved: NO x Emission concentration ≤30mg / Nm 3 SO2 emission concentration ≤30mg / Nm 3 Dust emission concentration ≤10mg / Nm 3 .

[0034] Furthermore, the nickel recovery rate in the smelted ferronickel product described in step 5 is over 90%.

[0035] Compared with existing processes, the beneficial effects of this invention are as follows:

[0036] (1) The present invention adopts a coal-based pre-reduction process, which can selectively and controllably reduce iron and nickel resources. The raw material laterite nickel ore has low nickel grade requirements, the product has high nickel content in nickel-iron, and few nickel-iron impurities. The raw material has strong adaptability and can produce high-value products with cheap resources.

[0037] (2) Due to the high temperature and metallization rate of the material entering the electric furnace, the processing capacity of the electric furnace of the same power is increased by 50% to 100% compared with the RKEF process;

[0038] (3) Construct a more economical and reasonable heat utilization cycle chain, further reduce the ore particle size, strengthen the reduction reaction and heat and mass transfer, and the process is in a closed state with a compact flow. The whole process realizes continuous heat delivery of materials and eliminates heat loss and re-oxidation problems in the material transportation process.

[0039] (4) The present invention adopts direct coal combustion technology, which replaces secondary energy electricity by directly burning primary energy fossil coal for heating, and uses coal gas as fuel to replace the electricity in the traditional process, which greatly reduces the consumption of secondary energy (electricity). The new process has lower power consumption than conventional processes and can reduce power consumption by 20% to 50% compared with RKEF process.

[0040] (5) Low-sulfur coal is used as a reducing agent and consumption is low. Coke and semi-coke are not used. Suspension heating and reduction efficiency are high. Coal consumption is more than 20% lower than that of rotary kiln, which minimizes energy consumption.

[0041] (6) This invention adopts multiple energy-saving process technologies and achieves efficient energy utilization through multiple means of waste gas and waste heat recovery and utilization, which greatly realizes energy saving and consumption reduction. The total energy consumption of the process system is reduced by more than 0.2 tce (converted to standard coal) compared with conventional processes.

[0042] (7) Compared with traditional processes, the suspension roasting system in this invention has its own denitrification and dust removal devices, eliminating the need for new waste gas treatment devices. The new process produces less gaseous waste and can achieve ultra-low emissions, making it environmentally friendly. All input raw materials are used to produce products, and the entire process avoids solid waste emissions in traditional processes, greatly reducing environmental pollution, improving resource utilization efficiency, and achieving significant environmental benefits.

[0043] (8) This invention makes up for the limitations and deficiencies of the traditional RKEF process, can reduce process energy consumption, improve resource recovery rate, and provide a new innovative breakthrough direction for the efficient utilization of laterite nickel ore resources to smelt nickel-iron alloys, which greatly improves the economic value of the development and utilization of such resources. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the process flow for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting according to the present invention.

[0045] In the diagram: 1. Raw ore feeding conveyor belt, 2. Drying rotary kiln, 3. Conveyor belt, 4. Storage silo, 5. Quantitative feeder, 6. Feeding airlock device, 7. Powder vertical mill, 8. Denitrification reactor, 9. Primary cyclone preheater, 10. Secondary cyclone preheater, 11. Suspension roasting main furnace, 12. Coal-fired hot blast stove, 13. Cyclone heater, 14. Airlock valve, 15. Reduction reactor, 16. Material sealing valve, 17. Storage distributor, 18. Submerged arc furnace, 19. Cooling heat exchange device, 20. Exhaust pipe, 21. Exhaust fan, 22. Electrostatic precipitator, 23. Powder conveyor, 24. Bag filter, 25. Exhaust fan, 26. Desulfurization tower. Detailed Implementation

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0047] To facilitate understanding of the present invention, a more comprehensive description of the invention will be given below with reference to the accompanying drawings, and several embodiments of the invention will be provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the present invention will be more thorough and complete.

[0048] A system for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes a feeding and drying unit, a preheating, drying and pulverizing unit, a heating unit, a coal-based pre-reduction unit, an electric furnace smelting waste heat recovery unit, and a dust removal, powder conveying and desulfurization unit.

[0049] The feeding and drying unit includes a raw ore feeding belt conveyor 1, a drying rotary kiln 2, a conveyor belt 3, a storage silo 4, a quantitative feeder 5, and a feeding airlock device 6; the raw ore feeding belt conveyor 1 is connected to the drying rotary kiln 2, the conveyor belt 3, and the storage silo 4, and the storage silo 4, the quantitative feeder 5, and the feeding airlock device 6 are connected in sequence.

[0050] The preheating, drying and pulverizing unit includes a vertical mill 7, a denitrification reactor 8, a primary cyclone preheater 9, and a secondary cyclone preheater 10; the feeding airlock device 6 is connected to the vertical mill 7, the vertical mill 7 is connected to the denitrification reactor 8 and the primary cyclone preheater 9 through a flue, and the primary cyclone preheater 9 is connected to the secondary cyclone preheater 10 through a flue.

[0051] The heating unit includes a suspension roasting main furnace 11, a coal-fired hot air furnace 12, and a cyclone heater 13; the secondary cyclone preheater 10 is connected to the suspension roasting main furnace 11 through a flue, and the suspension roasting main furnace 11 is connected to the coal-fired hot air furnace 12 and the cyclone heater 13 through a flue.

[0052] The coal-based pre-reduction unit includes a gas lock valve 14, a reduction reactor 15, a material sealing valve 16, and a material storage distributor 17; the cyclone heater 13 is connected to the gas lock valve 14 through a flue, and the reduction reactor 15 is connected to the gas lock valve 14, the material sealing valve 16, and the material storage distributor 17 through a flue.

[0053] The electric furnace smelting waste heat recovery unit includes an electric arc furnace 18, a cooling heat exchange device 19, and an exhaust pipe 20; the material distribution device 17 is connected to the electric arc furnace 18 through a feeding pipe, the electric arc furnace 18 is connected to the cooling heat exchange device 19 and the exhaust pipe 20, the cooling heat exchange device 19 is connected to the drying rotary kiln 2 through a flue, and the exhaust pipe 20 is connected to the coal-fired hot blast stove 12 through a flue.

[0054] The dust removal and desulfurization unit includes an exhaust fan 21, an electrostatic precipitator 22, a powder conveyor 23, a bag filter 24, an induced draft fan 25, and a desulfurization tower 26. The primary cyclone preheater 9 is connected to the exhaust fan 21 through a flue. The exhaust fan 21 is connected to the drying kiln 2 through a flue. The drying rotary kiln 2 is connected to the electrostatic precipitator 22 through a flue. The ash hopper of the electrostatic precipitator 22 is connected to the powder conveyor 23. The powder conveyor 23 is connected to the bag filter 24 through a flue. The bag filter 24 is connected to the inlet flue of the electrostatic precipitator 22 through a flue. The discharge pipe of the bag filter 24 is connected to the cone of the cyclone heater 13. The electrostatic precipitator 22 is connected to the induced draft fan 25 through a flue. The induced draft fan 25 is connected to the desulfurization tower 26.

[0055] A process flow for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting, such as... Figure 1 As shown:

[0056] Lateritic nickel ore raw material with a certain amount of attached moisture is conveyed to the drying rotary kiln 2 via feeding belt conveyor 1 for drying. After the moisture content is reduced in the drying rotary kiln 2, the material is conveyed to the storage silo 4 via conveyor belt 3. After being weighed and metered by electronic quantitative feeder 5, it is fed into the feeding airlock device 6. The feeding airlock device 6 feeds the material into the powder vertical mill 7. NO is removed from the secondary cyclone preheater 10 and then through the denitrification reactor 8. x The hot flue gas preheats and dries the material in the vertical mill 7 to remove adhering water. The dry-crushed material in the vertical mill 7 enters the first-stage cyclone preheater 9 under the pneumatic conveying of the preheated flue gas. The material separated by the cyclone enters the second-stage cyclone preheater 10 under the conveying of the flue gas from the outlet of the cyclone heater 13. The separated material enters the suspension roasting main furnace 11 by its own weight. The high-temperature flue gas from the coal-fired hot blast stove 12 heats and cracks the material in the suspension roasting main furnace 11 and then conveys it to the cyclone heater 13. The separated material enters the reduction reactor 15 through the airlock valve 14. The material undergoes a reduction reaction with the coal-based coal powder from the material sealing valve 16 in the reduction reactor 15 and is then conveyed to the storage distributor 17. The high-temperature material, after being evenly distributed by the distributor, enters the electric arc furnace 18 for melting and smelting to produce ferronickel and nickel slag.

[0057] Example 1

[0058] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes the following steps:

[0059] Step (1): The raw material is laterite nickel ore with a true density of 2.53 t / m³. 3 The particle size is less than 28 mm. After crushing, the laterite nickel ore with 36% attached water is fed into the drying rotary kiln through the feeding belt conveyor for drying. After drying, the laterite nickel ore with 18.3% attached water is sent into the powder vertical mill through the conveyor belt, storage bin, quantitative feeder and feeding air lock device.

[0060] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill before being recycled for powder grinding and classification to obtain the powder product; the classification medium is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 405℃, negative pressure is -5.35kPa, the flue gas temperature at the outlet of the vertical mill is 110℃, negative pressure is -11.35kPa; the particle size of the powder product is ≤1.35mm, and the content of 56.3% is distributed in the range of 0.8mm to 1mm;

[0061] The denitrification treatment adopts selective catalytic reduction (SCR) process. The inlet temperature of the denitrification reactor is 425℃ and the inlet negative pressure is -4.6kPa. The reducing agent of the catalytic reduction (SCR) process is urea.

[0062] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation, with a separation efficiency of 92.5%; the separated solid material is carried by high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material; the tangential inlet negative pressure of the secondary cyclone preheater is -2.7 kPa; the separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material, and the outlet negative pressure of the primary cyclone preheater is -12.7 kPa;

[0063] Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 860℃ and the time is 1.5min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0064] The coal-fired hot blast stove uses bituminous coal, which is pulverized by a vertical mill and then fed into the stove. The coal has a true density of 1.29 t / m³. 3 The coal-fired hot blast stove has a coal particle size of -200 mesh and a content of 73.3%. The pulverized coal inlet pressure is 3870 Pa, the pulverized coal inlet solid-gas ratio is 0.83, the pressure rise is 5879 Pa, the high-temperature hot air outlet temperature is 959℃, the outlet pressure is -433 Pa, and the slag discharge rate is 245 kg / h.

[0065] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed through the storage distributor and then enters the electric arc furnace for smelting. The smelting temperature of the electric arc furnace is 778℃. The part of the electric arc furnace that is insufficient for the regenerative reduction reaction temperature is replenished by the electric arc furnace itself through power consumption; the smelting products ferronickel and nickel slag are obtained.

[0066] The reducing agent used in the pre-reduction reaction is pulverized coal. The CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion, and secondary energy is effectively utilized and recovered.

[0067] Step (6): After the cold air indirectly exchanges heat with the electric furnace smelting products and slag, it is sent into the drying rotary kiln by the exhaust fan. The hot air temperature is 386℃. The indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat exchanged with the high-temperature nickel iron and nickel slag by the serpentine cooler in an indirect heat exchange manner. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide dry hot air for the drying rotary kiln and realize the recycling of energy.

[0068] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater and enters the pre-reduction reaction system. The negative pressure at the inlet of the exhaust fan is -13.02 kPa.

[0069] Step (8); The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal. After desulfurization and wet electrostatic precipitator, ultra-low emissions can be achieved: NO x Emission concentration: 21.56 mg / Nm³ 3 SO2 emission concentration: 18.37 mg / Nm³ 3 Dust emission concentration: 5.14 mg / Nm³ 3 ;

[0070] In steps 7 and 8, the system's wind pressure is supplied by the exhaust fan and the induced draft fan.

[0071] In this embodiment, the total energy consumption (converted to standard coal) is reduced by approximately 0.233 tce (converted to standard coal) compared to the conventional process, and the nickel recovery rate in the obtained smelting product, ferronickel, is 91.92%.

[0072] Example 2

[0073] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes the following steps:

[0074] Step (1): The raw material is laterite nickel ore with a true density of 2.47 t / m³. 3 The particle size is less than 25 mm. After crushing, the laterite nickel ore with 34.5% water content is fed into the drying rotary kiln through the feeding belt conveyor for drying. After drying, the laterite nickel ore with 19.5% water content is sent into the powder vertical mill through the conveyor belt, storage silo, quantitative feeder and feeding air lock device.

[0075] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill before being recycled for powder grinding and classification to obtain the powder product; the classification medium is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 413℃, negative pressure is -5.18kPa, the flue gas temperature at the outlet of the vertical mill is 133℃, negative pressure is -11.64kPa; the maximum particle size of the powder product is 1.40mm, and the content of particles in the range of 0.8mm to 1mm is 57.8%;

[0076] The denitrification treatment adopts selective catalytic reduction (SCR) process. The inlet temperature of the denitrification reactor is 432℃ and the inlet negative pressure is -4.7kPa. The reducing agent of the catalytic reduction (SCR) process is urea.

[0077] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation, with a separation efficiency of 90.9%; the separated solid material is carried by high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material; the tangential inlet negative pressure of the secondary cyclone preheater is -2.85 kPa; the separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material, and the outlet negative pressure of the primary cyclone preheater is -12.55 kPa;

[0078] Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 889℃ and the time is 1.7min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0079] The coal-fired hot blast stove uses bituminous coal, which is pulverized by a vertical mill and then fed into the stove. The coal has a true density of 1.30 t / m³. 3 The coal used in the coal-fired hot blast stove has a coal particle size of -200 mesh and a content of 75.7%. The pulverized coal inlet pressure is 4210 Pa, the pulverized coal inlet solid-gas ratio is 0.91, the pressure rise is 6180 Pa, the high-temperature hot air outlet temperature is 978℃, the outlet pressure is -393 Pa, and the slag discharge rate is 228 kg / h.

[0080] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed through the storage distributor and then enters the electric arc furnace for smelting. The smelting temperature of the electric arc furnace is 813℃. The part of the electric arc furnace that is insufficient for the regenerative reduction reaction temperature is replenished by the electric arc furnace itself through power consumption; the smelting products ferronickel and nickel slag are obtained.

[0081] The reducing agent used in the pre-reduction reaction is pulverized coal. The CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion, and secondary energy is effectively utilized and recovered.

[0082] Step (6): After the cold air indirectly exchanges heat with the electric furnace smelting products and slag, it is sent into the drying rotary kiln by the exhaust fan. The hot air temperature is 386℃. The indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat exchanged with the high-temperature nickel iron and nickel slag by the serpentine cooler in an indirect heat exchange manner. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide dry hot air for the drying rotary kiln and realize the recycling of energy.

[0083] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater and enters the pre-reduction reaction system. The negative pressure at the inlet of the exhaust fan is -13.17 kPa.

[0084] Step (8); The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal. After desulfurization and wet electrostatic precipitator, ultra-low emissions can be achieved: NO x Emission concentration: 22.33 mg / Nm³ 3 SO2 emission concentration: 16.57 mg / Nm³ 3 Dust emission concentration: 6.34 mg / Nm³ 3 ;

[0085] In steps 7 and 8, the system's wind pressure is supplied by the exhaust fan and the induced draft fan.

[0086] In this embodiment, the total energy consumption (converted to standard coal) is reduced by approximately 0.217 tce (converted to standard coal) compared to the conventional process, and the nickel recovery rate in the obtained smelting product, ferronickel, is 91.78%.

[0087] Example 3

[0088] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes the following steps:

[0089] Step (1): The raw material is laterite nickel ore with a true density of 2.41 t / m³. 3 The particle size is less than 29 mm. After crushing, the laterite nickel ore with 36.7% water content is fed into the drying rotary kiln through the feeding belt conveyor for drying. After drying, the laterite nickel ore with 20.9% water content is sent into the powder vertical mill through the conveyor belt, storage silo, quantitative feeder and feeding air lock device.

[0090] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill before being recycled for powder grinding and classification to obtain the powder product; the classification medium is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 438℃, the negative pressure is -5.33kPa, the flue gas temperature at the outlet of the vertical mill is 125℃, and the negative pressure is -11.88kPa; the maximum particle size of the powder product is 1.35mm, and the content of particles in the range of 0.8mm to 1mm is 61.2%;

[0091] The denitrification treatment adopts selective catalytic reduction (SCR) process. The inlet temperature of the denitrification reactor is 444℃ and the inlet negative pressure is -4.77kPa. The reducing agent of the catalytic reduction (SCR) process is urea.

[0092] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation, with a separation efficiency of 91.35%; the separated solid material is carried by high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material; the tangential inlet negative pressure of the secondary cyclone preheater is -2.73 kPa; the separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material, and the outlet negative pressure of the primary cyclone preheater is -12.67 kPa;

[0093] Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 885℃ and the time is 1.59min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0094] The coal-fired hot blast stove uses bituminous coal, which is pulverized by a vertical mill and then fed into the stove. The coal has a true density of 1.34 t / m³. 3 The coal used in the coal-fired hot blast stove has a coal particle size of -200 mesh and a content of 72.4%. The pulverized coal inlet pressure is 4077 Pa, the pulverized coal inlet solid-gas ratio is 0.93, the pressure rise is 6430 Pa, the high-temperature hot air outlet temperature is 1028℃, the outlet pressure is -383 Pa, and the slag discharge rate is 201 kg / h.

[0095] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed by the storage distributor and then enters the electric arc furnace for smelting. The smelting temperature of the electric arc furnace is 837℃. The part of the electric arc furnace that is insufficient for the regenerative reduction reaction temperature is replenished by the electric arc furnace itself through power consumption; the smelting products are ferronickel and nickel slag.

[0096] The reducing agent used in the pre-reduction reaction is pulverized coal. The CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion, and secondary energy is effectively utilized and recovered.

[0097] Step (6): After the cold air indirectly exchanges heat with the electric furnace smelting products and slag, it is sent into the drying rotary kiln by the exhaust fan. The hot air temperature is 396℃. The indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat exchanged with the high-temperature nickel iron and nickel slag through the serpentine cooler in an indirect heat exchange manner. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide dry hot air for the drying rotary kiln and realize the recycling of energy.

[0098] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater and enters the pre-reduction reaction system. The negative pressure at the inlet of the exhaust fan is -13.32 kPa.

[0099] Step (8); The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal. After desulfurization and wet electrostatic precipitator, ultra-low emissions can be achieved: NO x Emission concentration: 25.13 mg / Nm³ 3 SO2 emission concentration: 14.55 mg / Nm³ 3 Dust emission concentration: 6.71 mg / Nm³ 3 ;

[0100] In steps 7 and 8, the system's wind pressure is supplied by the exhaust fan and the induced draft fan.

[0101] In this embodiment, the total energy consumption (converted to standard coal) is reduced by approximately 0.232 tce (converted to standard coal) compared to the conventional process, and the nickel recovery rate in the obtained smelting product, ferronickel, is 92.06%.

[0102] Example 4

[0103] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes the following steps:

[0104] Step (1): The raw material is laterite nickel ore with a true density of 2.44 t / m³. 3 The particle size is less than 26 mm. After crushing, the laterite nickel ore with 37.3% water content is fed into the drying rotary kiln through the feeding belt conveyor for drying. After drying, the laterite nickel ore with 21.7% water content is sent into the powder vertical mill through the conveyor belt, storage bin, quantitative feeder and feeding air lock device.

[0105] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill before being recycled for powder grinding and classification to obtain the powder product; the classification medium is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 430℃, negative pressure is -5.22kPa, the flue gas temperature at the outlet of the vertical mill is 129℃, negative pressure is -11.57kPa; the maximum particle size of the powder product is 1.47mm, and the content of particles in the range of 0.8mm to 1mm is 62.0%;

[0106] The denitrification treatment adopts selective catalytic reduction (SCR) process. The inlet temperature of the denitrification reactor is 411℃ and the inlet negative pressure is -4.5kPa. The reducing agent of the catalytic reduction (SCR) process is urea.

[0107] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation, with a separation efficiency of 91.89%; the separated solid material is carried by high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material; the tangential inlet negative pressure of the secondary cyclone preheater is -2.72 kPa; the separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material, and the outlet negative pressure of the primary cyclone preheater is -12.62 kPa;

[0108] Step (4): The pre-roasted material falls into the suspension roasting main furnace by its own weight for further heating and cracking. The heating and cracking temperature is 903℃ and the time is 1.5min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0109] The coal-fired hot blast stove uses bituminous coal, which is pulverized by a vertical mill and then fed into the stove. The coal has a true density of 1.32 t / m³. 3 The coal-fired hot blast stove has a coal particle size of -200 mesh and a content of 71.4%. The pulverized coal inlet pressure is 4333 Pa, the pulverized coal inlet solid-gas ratio is 0.84, the pressure rise is 6040 Pa, the high-temperature hot air outlet temperature is 934℃, the outlet pressure is -378 Pa, and the slag discharge rate is 188 kg / h.

[0110] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed by the storage distributor and then enters the electric arc furnace for smelting. The smelting temperature of the electric arc furnace is 841℃. The part of the electric arc furnace that is insufficient for the regenerative reduction reaction temperature is replenished by the electric arc furnace itself through power consumption; the smelting products ferronickel and nickel slag are obtained.

[0111] The reducing agent used in the pre-reduction reaction is pulverized coal. The CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion, and secondary energy is effectively utilized and recovered.

[0112] Step (6): After the cold air indirectly exchanges heat with the electric furnace smelting products and slag, it is sent into the drying rotary kiln by the exhaust fan. The hot air temperature is 377℃. The indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat exchanged with the high-temperature nickel iron and nickel slag through the serpentine cooler in an indirect heat exchange manner. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide dry hot air for the drying rotary kiln and realize the recycling of energy.

[0113] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater and enters the pre-reduction reaction system. The negative pressure at the inlet of the exhaust fan is -13.22 kPa.

[0114] Step (8); The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal. After desulfurization and wet electrostatic precipitator, ultra-low emissions can be achieved: NO x Emission concentration: 18.01 mg / Nm³ 3 SO2 emission concentration: 15.44 mg / Nm³ 3 Dust emission concentration: 7.01 mg / Nm³ 3 ;

[0115] In steps 7 and 8, the system's wind pressure is supplied by the exhaust fan and the induced draft fan.

[0116] In this embodiment, the total energy consumption (converted to standard coal) is reduced by approximately 0.219 tce (converted to standard coal) compared to the conventional process, and the nickel recovery rate in the obtained smelting product, ferronickel, is 90.90%.

[0117] Example 5

[0118] A process for producing nickel from laterite nickel ore by coal-based roasting and reduction electric furnace smelting includes the following steps:

[0119] Step (1): The raw material is laterite nickel ore with a true density of 2.55 t / m³. 3 The particle size is less than 29 mm. After crushing, the laterite nickel ore with 37% attached water is fed into the drying rotary kiln through the feeding belt conveyor for drying. After drying, the laterite nickel ore with 18.99% attached water is sent into the powder vertical mill through the conveyor belt, storage bin, quantitative feeder and feeding air lock device.

[0120] Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor 8, and then preheated and dried with the material in the vertical mill before being recycled for powder grinding and classification to obtain the powder product; the classification medium is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 418℃, negative pressure is -5.09kPa, the flue gas temperature at the outlet of the vertical mill is 122℃, negative pressure is -11.17kPa; the particle size of the powder product is ≤1.42mm, and the content of 59.9% is distributed in the range of 0.8mm to 1mm;

[0121] The denitrification treatment adopts selective catalytic reduction (SCR) process. The inlet temperature of the denitrification reactor is 408℃ and the inlet negative pressure is -4.7kPa. The reducing agent of the catalytic reduction (SCR) process is urea.

[0122] Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation, with a separation efficiency of 93.1%; the separated solid material is carried by high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material; the tangential inlet negative pressure of the secondary cyclone preheater is -2.75 kPa; the separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material, and the outlet negative pressure of the primary cyclone preheater is -12.8 kPa;

[0123] Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 892℃ and the time is 1.65min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system.

[0124] The coal-fired hot blast stove uses bituminous coal, which is pulverized by a vertical mill and then fed into the stove. The coal has a true density of 1.31 t / m³. 3 The coal-fired hot blast stove has a coal particle size of -200 mesh and a content of 74.3%. The pulverized coal inlet pressure is 3950 Pa, the pulverized coal inlet solid-gas ratio is 0.79, the pressure rise is 5811 Pa, the high-temperature hot air outlet temperature is 960℃, the outlet pressure is -409 Pa, and the slag discharge rate is 213 kg / h.

[0125] Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed through the storage distributor and then enters the electric arc furnace for smelting. The smelting temperature of the electric arc furnace is 814℃. The part of the electric arc furnace that is insufficient for the regenerative reduction reaction temperature is replenished by the electric arc furnace itself through power consumption; the smelting products ferronickel and nickel slag are obtained.

[0126] The reducing agent used in the pre-reduction reaction is pulverized coal. The CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion, and secondary energy is effectively utilized and recovered.

[0127] Step (6): After the cold air indirectly exchanges heat with the electric furnace smelting products and slag, it is sent into the drying rotary kiln by the exhaust fan. The hot air temperature is 396℃. The indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat exchanged with the high-temperature nickel iron and nickel slag through the serpentine cooler in an indirect heat exchange manner. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide dry hot air for the drying rotary kiln and realize the recycling of energy.

[0128] Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater and enters the pre-reduction reaction system. The negative pressure at the inlet of the exhaust fan is -13.22 kPa.

[0129] Step (8); The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal. After desulfurization and wet electrostatic precipitator, ultra-low emissions can be achieved: NO x Emission concentration: 18.33 mg / Nm³ 3 SO2 emission concentration: 16.16 mg / Nm³ 3 Dust emission concentration: 6.37 mg / Nm³ 3 ;

[0130] In steps 7 and 8, the system's wind pressure is supplied by the exhaust fan and the induced draft fan.

[0131] In this embodiment, the total energy consumption (converted to standard coal) is reduced by approximately 0.229 tce (converted to standard coal) compared to the conventional process, and the nickel recovery rate in the obtained smelting product, ferronickel, is 92.43%.

Claims

1. A system for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore, characterized in that, It includes a feeding and drying unit, a preheating, drying and pulverizing unit, a heating unit, a coal-based pre-reduction unit, an electric furnace smelting waste heat recovery unit, and a dust removal, powder conveying and desulfurization unit. The feeding and drying unit includes a raw ore feeding belt conveyor (1), a drying rotary kiln (2), a conveyor belt (3), a storage bin (4), a quantitative feeder (5), and a feeding airlock device (6); the raw ore feeding belt conveyor (1), the drying rotary kiln (2), and the conveyor belt (3) are connected together, and the conveyor belt (3), the storage bin (4), the quantitative feeder (5), and the feeding airlock device (6) are connected in sequence; The preheating, drying and pulverizing unit includes a vertical mill (7), a denitrification reactor (8), a primary cyclone preheater (9), and a secondary cyclone preheater (10); the feeding airlock device (6) is connected to the vertical mill (7), the vertical mill (7) is connected to the denitrification reactor (8) and the primary cyclone preheater (9) through a flue, and the primary cyclone preheater (9) is connected to the secondary cyclone preheater (10) through a flue; The heating unit includes a suspension roasting main furnace (11), a coal-fired hot air furnace (12), and a cyclone heater (13); the secondary cyclone preheater (10) is connected to the suspension roasting main furnace (11) and the cyclone heater (13) through a flue, and the suspension roasting main furnace (11) is connected to the coal-fired hot air furnace (12) through a flue. The coal-based pre-reduction unit includes a gas lock valve (14), a reduction reactor (15), a material sealing valve (16), and a material distribution device (17); the cyclone heater (13) is connected to the gas lock valve (14) through a flue, and the reduction reactor (15) is connected to the gas lock valve (14), the material sealing valve (16), and the material distribution device (17) through a flue. The electric furnace smelting waste heat recovery unit includes an electric arc furnace (18), a cooling heat exchange device (19), and an exhaust pipe (20); the material distributor (17) is connected to the electric arc furnace (18) through a feeding pipe, the electric arc furnace (18) is connected to the cooling heat exchange device (19) and the exhaust pipe (20), the cooling heat exchange device (19) is connected to the drying rotary kiln (2) through a flue, and the exhaust pipe (20) is connected to the coal-fired hot blast stove (12) through a flue; The dust removal and powder conveying desulfurization unit includes an exhaust fan (21), an electrostatic precipitator (22), a powder conveyor (23), a bag filter (24), an induced draft fan (25), and a desulfurization tower (26). The primary cyclone preheater (9) is connected to the exhaust fan (21), the drying rotary kiln (2), and the electrostatic precipitator (22) in sequence through a flue. The ash hopper of the electrostatic precipitator (22) is connected to the powder conveyor (23). The powder conveyor (23) is connected to the bag filter (24) and the inlet flue of the electrostatic precipitator (22) in sequence through a flue. The discharge pipe of the bag filter (24) is connected to the cone of the cyclone heater (13). The electrostatic precipitator (22) is connected to the induced draft fan (25) through a flue. The induced draft fan (25) is connected to the desulfurization tower (26).

2. The system for producing nickel by laterite nickel ore coal-based roasting and reduction electric furnace smelting according to claim 1, characterized in that, The feeding airlock device is a screw feeder or an airlock material sealing valve.

3. A process for producing nickel by laterite nickel ore coal-based roasting and reduction electric furnace smelting, employing the system for producing nickel by laterite nickel ore coal-based roasting and reduction electric furnace smelting as described in claim 1 or claim 2, characterized in that, Specifically, the steps include the following: Step (1): The laterite nickel ore is crushed to a water content of 30% to 40% and then fed into a drying rotary kiln via a feeding belt conveyor for drying. The dried laterite nickel ore with a water content of 15% to 25% is then fed into a powder vertical mill via a conveyor belt, storage bin, quantitative feeder, and feeding airlock device. Step (2): The high-temperature flue gas from the secondary cyclone preheater is denitrified by the denitrification reactor, and then preheated and dried with the material in the vertical mill for powder grinding and classification circulation to obtain the powder product; the particle size of the powder product is ≤1.5mm, and the distribution in the 0.8mm~1mm range is greater than 50%; the medium for classification circulation is high-temperature gas phase flue gas; the flue gas temperature at the inlet of the vertical mill is 380~420℃, negative pressure -5~-6kPa, and the flue gas temperature at the outlet of the vertical mill is 100~150℃, negative pressure -11~-12kPa; Step (3): The powder vertical mill product is conveyed by high-temperature flue gas from the secondary cyclone preheater to the primary cyclone preheater for gas-solid separation. The tangential inlet negative pressure of the primary cyclone preheater is -12 to -12.5 kPa. The separated solid material is carried by the high-temperature flue gas from the cyclone heater to the secondary cyclone preheater for gas-solid separation and removal of crystal water to obtain pre-baked material. The separation efficiency of the cyclone preheater is over 90%, and the preheating time is 10s to 30s. The tangential inlet negative pressure of the secondary cyclone preheater is -2.5 to -3.5 kPa. The separated lower-temperature flue gas is carried by the exhaust fan to the drying rotary kiln to dry and preheat the laterite nickel ore raw material. Step (4): The pre-roasted material falls into the suspension roasting furnace by its own weight for further heating and cracking. The heating and cracking temperature is 700-1000℃ and the time is 1-3min. After heating and cracking, it is sent to the cyclone heater by high-temperature hot air from the coal-fired hot air furnace for gas-solid separation. The separated high-temperature material enters the coal-based pre-reduction system. Step (5): The high-temperature material enters the reduction reactor through the airlock valve, and after pre-reduction reaction with the coal powder from the material sealing valve, it is distributed by the storage distributor and then enters the electric arc furnace for smelting to obtain the smelted products ferronickel and nickel slag. Step (6): After the cold air indirectly exchanges heat with the smelted products ferronickel and nickel slag, it is sent into the drying rotary kiln through the exhaust fan; Step (7): The flue gas and dust separated by the first-stage cyclone preheater are preheated and dried by the exhaust fan before entering the electrostatic precipitator for dust removal. The dust-removed powder material is transported to the bag filter by the powder conveyor under the action of compressed air. The powder material recovered by the bag filter is returned to the cone of the cyclone heater to enter the pre-reduction reaction described in step 5. The negative pressure at the inlet of the exhaust fan is -12.5 to -13.5 kPa. Step (8): The flue gas after dust removal is sent to the desulfurization tower by an induced draft fan. The desulfurization process adopts limestone-gypsum wet desulfurization and wet electrostatic precipitator for further dust removal.

4. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, The true density of the laterite nickel ore in step 1 is 2.2–3 t / m³. 3 The particle size is less than 30 mm.

5. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, In step 2, the denitrification process adopts selective catalytic reduction (SCR) technology. The inlet temperature of the denitrification reactor is 400℃~440℃, and the inlet negative pressure is -4~-5kPa. The reducing agent of the SCR process is urea.

6. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, The coal used in step 4 is bituminous coal, which is pulverized by a vertical mill and then transported to the coal-fired hot blast stove. The coal has a true density of 1.27–1.33 t / m³. 3 The coal used in the hot blast stove has a coal particle size of -200 mesh and a content of 70-90%. The hot blast stove is a lined furnace with a pulverized coal inlet pressure of 3000-5000 Pa and a pulverized coal inlet solid-gas ratio of 0.5-1.

2. The primary combustion air fan of the burner has a flow rate of 50000-75000 Nm³ / h, a pressure rise of 5000-7000 Pa, a calorific value of 5000-550000 kcal / h, and a high-temperature hot air outlet temperature. The temperature ranges from 750 to 1100℃, the outlet air velocity is 17 to 25 m / s, the outlet flue gas flow rate is 450,000 to 660,000 Nm³ / h, and the outlet pressure is -300 to -500 Pa. Slag is discharged intermittently, continuously, or at regular intervals, with a slag discharge rate of 150 to 300 kg / h and a slag discharge temperature of 200 to 500℃. The outlet temperature of the high-temperature hot air in step 4 can be adjusted by adding cold air, with a cold air volume of 28,000 to 100,000 m³ / h.

7. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, The smelting temperature of the electric arc furnace in step 5 is 750-950℃; the reducing agent used in the pre-reduction reaction in step 5 is pulverized coal, and the CO, CO2 and other gases produced by the reduction reaction of pulverized coal with laterite nickel ore are sent to a coal-fired hot blast stove for combustion; the nickel slag in step 5 can be used to manufacture bricks.

8. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, In step 6, the indirect heat exchange device between the cold air and the electric furnace smelting products and slag is a serpentine cooler. The cold air is cooled and heat-exchanged by the serpentine cooler in an indirect heat exchange manner on the high-temperature nickel iron and nickel slag. The hot air after air-cooled heat exchange is connected to the drying rotary kiln to provide drying hot air for the drying rotary kiln, thereby realizing the recycling of energy.

9. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, After dust removal in step 8, ultra-low emissions can be achieved: NOx emission concentration ≤30mg / Nm³. 3 SO2 emission concentration ≤30mg / Nm 3 Dust emission concentration ≤10mg / Nm 3 .

10. The process for producing nickel by coal-based roasting and reduction electric furnace smelting of laterite nickel ore according to claim 3, characterized in that, The nickel recovery rate in the smelted product ferronickel described in step 5 is over 90%.

Images