Low-grade magnetite tailings, limonite tailings suspension magnetization reduction calcination process

Abstract

The present application relates to a kind of low-grade siderite tailings, brown iron tailing suspension magnetization reduction calcination process, belong to iron ore dressing technical field.The low-grade siderite, brown iron tail suspension magnetization reduction calcination system includes raw material conveying system, raw material preheating system, raw material oxidation calcination and reduction system, finished product cooling system and raw material dust collection and dust return system;Siderite, brown iron tailings powder is transported from conveying system to waste heat system, enters into main calcining furnace and occurs oxidation reaction, then calcined material enters into reducer and occurs reduction reaction, and finished product after reduction enters into cooling system, and the finished product material after cooling is stored, solve the problem that siderite, brown iron tailings powder low-grade magnetite oxide content is low, grade is low and cannot be produced and utilized.

Description

Technical Field

[0001] This invention belongs to the field of iron ore beneficiation technology, specifically a low-grade horn and limonite tailings suspension magnetization reduction calcination system and process. Background Technology

[0002] Currently, the comprehensive utilization of low-grade iron ore and tailings has become an important development direction for my country's metallurgical mining industry. China is rich in iron ore resources, with proven reserves exceeding 80 billion tons. However, China's iron ore endowment is poor, mainly due to fine mineral crystal size, complex composition, and especially low iron grade. my country's iron ore is generally of poor grade and low content, characterized by fine iron mineral crystal size, deep oxidation, and complex mineral composition. It has high content of limonite and siderite, resulting in extremely poor beneficiation and low resource utilization efficiency.

[0003] With the continuous development of mining and the steel industry, the storage volume of iron tailings, as waste after mineral processing, is also constantly increasing. Statistics show that the global annual cumulative increase in tailings reaches 5 to 7 billion tons, with iron tailings accounting for about half. Currently, the total stockpile of iron tailings in China and Brazil alone exceeds 10 billion tons. my country's annual total tailings production is approximately 1.272 billion tons, of which iron tailings account for the largest share, approximately 520 million tons, or 39.9% of the total tailings production. Improving the resource utilization rate of iron tailings is of great significance for reducing the pressure on existing mineral resources, turning waste into treasure, promoting national economic development, ensuring iron resource supply, and protecting the environment.

[0004] Currently, the main methods for treating iron tailings include iron tailings reprocessing, tailings dam storage, vegetation reclamation, and mine backfilling. Traditional methods of treating iron tailings have the following problems: poor concentrate quality and low recovery rate, making them unusable for production; high raw material processing costs; and inefficient use of energy. Summary of the Invention

[0005] To address the aforementioned problems and solve the technical challenges of beneficiating refractory iron ore, this invention relates to a suspension magnetization reduction calcination system and process for low-grade hornblende and limonite tailings. The powdered hornblende and limonite tailings are transported from the conveying system to the waste heat system, where they enter the main calcining furnace to undergo an oxidation reaction. The calcined material then enters the reducer to undergo a reduction reaction. The reduced product then enters the cooling system for storage.

[0006] A suspension magnetization reduction calcination system for low-grade siderite tailings and limonite tailings includes a raw material conveying system, a raw material preheating system, a raw material oxidation calcination and reduction system, a finished product cooling system, and a raw material dust collection and ash return system.

[0007] The raw material conveying system includes a raw material belt conveyor, a raw material silo, a raw material quantitative feeder, and a raw material bucket elevator. The bottom of the raw material silo is equipped with an electric slide gate valve, which is connected to the raw material quantitative feeder.

[0008] The raw material preheating system includes a primary suspension preheater, a primary preheating mixer, a secondary suspension preheater, and a secondary preheating mixer;

[0009] The raw material oxidation, calcination and reduction system includes a main separation furnace, a main calcination furnace, a primary plug-flow fluidized bed reducer and a secondary plug-flow fluidized bed reducer;

[0010] The finished product cooling system includes a primary suspension cooler, a secondary suspension cooler, a primary cooling mixer, a secondary cooling mixer, and a twin-blade stirred fluidized bed cooler.

[0011] The raw material dust collection and return system includes a primary diffusion cyclone dust collector, a flue gas waste heat boiler, and a secondary bag filter dust collector.

[0012] A suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings includes the following steps:

[0013] (1) Raw material conveying: The raw material is powdery low-grade siderite tailings and limonite tailings. The raw material enters the raw material silo through the raw material belt conveyor and is discharged into the raw material quantitative feeder through the electric slide valve at the bottom of the raw material silo. The raw material quantitative feeder can control the hourly feed rate of the raw material. After passing through the raw material quantitative feeder, the raw material enters the raw material bucket elevator and is then discharged by the raw material bucket elevator into the primary suspension preheater.

[0014] (2) Raw material preheating: After the raw material enters the first-stage suspension preheater, it undergoes gas-solid two-phase heat exchange and separation with the raw material and flue gas exiting from the side outlet of the first-stage preheating mixer, and removes some of the attached water from the raw material. The raw material and flue gas discharged from the top of the first-stage suspension preheater enter two parallel first-stage diffusion cyclone dust collectors. The material discharged from the bottom of the first-stage suspension preheater and the calcined material and flue gas discharged from the top of the main separator enter the inlet on the side of the bottom of the second-stage preheating mixer for direct heat exchange, so that the raw material and flue gas are in a highly turbulent state in the second-stage preheating mixer. In the first stage, the gas-solid two-phase contact area increases, the contact time increases, and the heat exchange is enhanced, causing the temperatures of the gas and solid phases to tend to be uniform. The raw materials, calcined materials, and flue gas discharged from the top side of the second-stage preheating mixer enter the second-stage suspension preheater for further gas-solid two-phase heat exchange and separation. A portion of the raw materials and flue gas discharged from the top of the second-stage suspension preheater enters the bottom side inlet of the first-stage preheating mixer at the same time as the bottom discharge of the two parallel first-stage diffusion cyclone dust collectors for mixing and direct heat exchange. The other portion of the raw materials and flue gas discharged from the top of the second-stage suspension preheater enters the bottom side inlet of the first-stage preheating mixer.

[0015] (3) Raw material oxidation, calcination, and reduction: The bottom discharge from the secondary suspension preheater and the ash return from the ash return system enter the main calcining furnace. The fuel gas in the main calcining furnace comes from the external pipeline and is burned to provide heat for the phase change reaction. After high-temperature phase change reaction, oxidation, and hydrolysis in the main calcining furnace, the γ-Fe2O3, Fe3O4, and Fe2O3•H2O in the raw material are converted into α-Fe2O3 before entering the main separation furnace. The bottom discharge from the main separation furnace enters the primary plug-flow fluidized bed reducer. The primary plug-flow fluidized bed reducer is fed from the top and the reducing gas is introduced from the bottom. The reducing gas is controlled by... The feed volume flow rate and feed gas pressure are adjusted to regulate the residence time of the calcined material in the primary plug-flow fluidized bed reducer, ensuring sufficient reduction and heat exchange for cooling. The reduction involves the reduction of α-Fe2O3 to magnetic Fe3O4. The reduction exhaust gas from the top of the primary plug-flow fluidized bed reducer enters the top exhaust pipe of the primary suspension cooler, and together with the finished product and combustion air discharged from the top of the primary suspension cooler, it enters the bottom of the main calcining furnace. The bottom discharge of the primary plug-flow fluidized bed reducer then enters the secondary plug-flow fluidized bed reducer for further reduction and heat exchange for cooling.

[0016] The secondary plug-flow fluidized bed reducer is fed from the top and circulated with reducing gas from the bottom. By controlling the feed volume, flow rate, and pressure of the reducing gas, the residence time of the bottom discharge from the primary plug-flow fluidized bed reducer within the secondary plug-flow fluidized bed reducer is adjusted, ensuring sufficient reduction and heat exchange for cooling. The reduction exhaust gas from the top of the secondary plug-flow fluidized bed reducer enters the top exhaust pipe of the primary suspension cooler, where it, along with the top exhaust product and combustion air, enters the bottom of the main calcining furnace. The bottom discharge from the secondary plug-flow fluidized bed reducer, along with the top exhaust product and combustion air from the secondary suspension cooler, enters the bottom side inlet of the primary cooling mixer. The bottom discharge from the main separator undergoes reduction phase change and heat exchange for cooling within the two-stage plug-flow fluidized bed reducer, and oxidation phase change is prevented under the protection of the reducing gas.

[0017] (4) Finished Product Cooling: The finished product and combustion air discharged from the top of the primary suspension cooler, together with the reduction waste gas from the top of the primary and secondary plug-flow fluidized bed reducers, enter the main calcining furnace; the bottom discharge of the primary suspension cooler, together with the combustion air, enters the bottom inlet of the secondary cooling mixer; the finished product and combustion air are thoroughly mixed in the secondary cooling mixer, which further cools the finished product and further increases the temperature of the combustion air; the finished product and combustion air discharged from the top side of the secondary cooling mixer enter the secondary suspension cooler for further heat exchange and gas-solid two-phase separation; the finished product and combustion air discharged from the top of the secondary suspension cooler... Air and the finished product discharge from the bottom of the secondary plug-flow fluidized bed reducer enter the bottom side inlet of the primary cooling mixer for heat exchange and cooling. Then, the finished product and combustion air from the top side outlet of the primary cooling mixer enter the primary suspension cooler. The finished product discharge from the bottom of the secondary suspension cooler enters the double-blade stirred fluidized bed cooler. The top feed of the double-blade stirred fluidized bed cooler comes from the secondary suspension cooler. Then, cooling air enters from one side of the double-blade stirred fluidized bed cooler. The finished product fully exchanges heat with the cooling air under the stirring of the blades. After heat exchange, the finished product is discharged from the bottom of the double-blade stirred fluidized bed cooler and enters the finished product silo for storage via the finished product belt conveyor.

[0018] (5) Raw material dust collection and ash return: The raw materials and flue gas discharged from the top of the primary suspension preheater enter two parallel primary diffusion cyclone dust collectors. The flue gas and raw materials are subjected to primary dust removal by the two parallel primary diffusion cyclone dust collectors. After primary dust removal, the flue gas enters the flue gas waste heat boiler for waste heat recovery and utilization, reducing the temperature and volume of the flue gas, and generating saturated water vapor at a temperature of 100℃~110℃ for use in factory production and daily life. After being cooled by the waste heat boiler, the flue gas enters the secondary bag filter dust collector for secondary dust removal, and then is discharged through the flue gas exhaust fan. The exhaust gas is discharged to the chimney; the ash from the waste heat boiler and the secondary bag filter is fed into the main calcining furnace for calcination reaction via a pneumatic conveying system; the pneumatic conveying system includes a pneumatic lift pump and a Roots blower; a flue gas outlet pipe is connected to the flue gas inlet pipe of the chimney, and a drying fan is installed on the flue gas outlet pipe to send part of the exhaust gas to the bottom of the raw material bucket elevator, where the high-temperature flue gas dries the attached water of the raw material in the raw material bucket elevator, thereby reducing the attached water content of the raw material entering the calcination system and reducing the energy consumption of the calcination system; the purified flue gas at the top of the raw material bucket elevator is sent to the primary diffusion cyclone dust collector through the exhaust pipe.

[0019] Furthermore, the raw material is powdery siderite tailings and limonite tailings with a particle size distribution of 100μm~1000μm and an attached water content of 12%~15%.

[0020] Furthermore, the temperature in the primary suspension preheater is 210℃~280℃, and 10%~20% of the attached water in the raw material is removed in the primary suspension preheater; the temperature in the primary preheating mixer is 220℃~290℃; the temperature in the secondary suspension preheater is 310℃~380℃; the temperature in the secondary preheating mixer is 320℃~390℃, and all the attached water in the raw material is removed in the secondary preheating mixer; the temperature in the main calcining furnace is 645℃~755℃.

[0021] Furthermore, the reducing gas includes H2, CO, and CH4.

[0022] Furthermore, the discharge temperature of the primary plug-flow fluidized bed reducer is 490℃~530℃, and the discharge temperature of the secondary plug-flow fluidized bed reducer is 260℃~300℃.

[0023] Furthermore, the finished product in the dual-blade stirred fluidized bed cooler undergoes sufficient heat exchange with the cooling air under the stirring of the blades. After heat exchange, the cooling air is discharged from the other side of the dual-blade stirred fluidized bed cooler and enters the bottom side inlet of the secondary cooling mixer together with the combustion air and the bottom discharge of the primary suspension cooler.

[0024] Furthermore, the combustion air velocity in the raw material oxidation calcination and reduction system and the finished product cooling system is 14 m / s to 16 m / s; the flue gas velocity is also 14 m / s to 16 m / s.

[0025] Furthermore, in the finished product cooling system, the temperature of the primary suspension cooler is 210℃~239℃, the temperature of the primary cooling mixer is 220℃~250℃, the temperature of the secondary suspension cooler is 180℃~210℃, and the temperature of the secondary cooling mixer is 190℃~220℃.

[0026] The beneficial effects of this invention are:

[0027] This invention solves the problem of low content and low grade of magnetic iron oxide in the powdered limonite and hornblende tailings, making them unsuitable for production and utilization. The invention involves preheating the limonite and hornblende tailings powder in suspension before oxidizing and calcining it in a calcining furnace. The calcined material then enters a reduction furnace, where the reduced product undergoes suspension cooling. Flue gas and raw materials undergo thorough direct heat exchange in a preheating mixer and a preheating suspension. The flue gas after heat exchange is indirectly heated through a waste heat boiler to produce saturated steam for production and domestic use. A portion of the exhaust flue gas is sent to a raw material bucket elevator to dry the auxiliary water, thus fully utilizing the sensible heat of the flue gas. The calcined material passes through a two-stage reduction unit to maximize the reduction rate of the finished product and lower its temperature, preventing oxidation. Direct heat exchange between the finished product and combustion air in a cooling mixer and a cooling suspension further maximizes the utilization of the sensible heat. Finally, the finished product is further cooled in a double-blade stirred fluidized bed cooler before storage. The cooling air, after being heated, enters the calcination system. This invention further improves the quality of finished products and the content of magnetic iron oxides through a multi-stage heat exchange system and a reduction system, increasing the iron grade by 8% to 12% and the metal recovery rate by 10% to 15%. Furthermore, by utilizing the sensible heat of flue gas and materials, it maximizes the cascade utilization of energy. This invention is of great significance for improving the quality of iron concentrate and the utilization rate of self-produced fines, further reducing production costs, improving mine resource flow, and increasing resource utilization. Attached Figure Description

[0028] Figure 1 This is an overall flowchart of the present invention;

[0029] Figure 2 This is a flowchart of the raw material conveying system of the present invention;

[0030] Figure 3 This is a flow chart of the raw material preheating system of the present invention;

[0031] Figure 4 This is a flow chart of the raw material oxidation, calcination, and reduction system of the present invention;

[0032] Figure 5 This is a flow chart of the finished product cooling system of the present invention;

[0033] Figure 6 This is a flow chart of the raw material dust collection and ash return system of the present invention;

[0034] In the diagram: 1. Raw material; 2. Raw material conveyor belt; 3. Raw material silo; 4. Electric slide gate valve; 5. Raw material metering feeder; 6. Raw material bucket elevator; 7. Primary suspension preheater; 8. Primary preheating mixer; 9. Secondary suspension preheater; 10. Secondary preheating mixer; 11. Main calcining furnace; 12. Main separation furnace; 13. Primary plug-flow fluidized bed reducer; 14. Secondary plug-flow fluidized bed reducer; 15. Primary suspension cooler; 16. Primary cooling mixer; 17. Secondary suspension cooler; 18. Secondary cooling mixer; 19. Double-blade stirred fluidized bed cooler; 20. Finished product. Belt conveyor; 21. Finished product silo; 22. Primary diffusion cyclone dust collector; 23. Flue gas waste heat boiler; 24. Secondary bag filter dust collector; 25. Flue gas exhaust fan; 26. Chimney; 27. Drying fan; 28. Roots blower; 29. ​​Pneumatic lift pump; 30. Pressure gauge; 31. Thermometer; 32. Flue gas; 33. Calcined material; 34. Ash return; 35. Fuel gas; 36. Reducing gas; 37. Reducing waste gas; 38. Finished product; 39. Combustion air; 40. Cooling air; 41. Heat exchange air; 42. Clean water; 43. Saturated steam; 44. Purified flue gas; 45. Sampling port. Detailed Implementation

[0035] The embodiments of the invention are described in detail below with reference to the accompanying drawings, but the scope of protection of the invention is not limited to the embodiments.

[0036] To better illustrate and understand the method of use of this invention, the invention will be described in detail below. The embodiments described below are only for better explaining the invention and are not intended to limit the invention. The scope of protection of this invention is determined by the claims.

[0037] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] A low-grade rhodochrosite and limonite tail suspension magnetization reduction calcination system includes a raw material conveying system, a raw material preheating system, a raw material oxidation calcination and reduction system, a finished product cooling system, and a raw material dust collection and ash return system;

[0039] like Figure 2As shown, the raw material conveying system includes a raw material belt conveyor (2), a raw material silo (3), a raw material quantitative feeder (5), and a raw material bucket elevator (6). An electric slide gate valve (4) is installed at the bottom of the raw material silo, which is connected to the raw material quantitative feeder (5).

[0040] like Figure 3 As shown, the raw material preheating system includes a primary suspension preheater (7), a primary preheating mixer (8), a secondary suspension preheater (9), and a secondary preheating mixer (10).

[0041] like Figure 4 As shown, the raw material oxidation calcination and reduction system includes a main separation furnace (12), a main calcination furnace (11), a primary plug-flow fluidized bed reducer (13), and a secondary plug-flow fluidized bed reducer (14).

[0042] like Figure 5 As shown, the finished product cooling system includes a primary suspension cooler (15), a secondary suspension cooler (17), a primary cooling mixer (16), a secondary cooling mixer (18), and a double-blade stirred fluidized bed cooler (19).

[0043] like Figure 6 As shown, the raw material dust collection and return system includes a primary diffusion cyclone dust collector (22), a flue gas waste heat boiler (23), a secondary bag dust collector (24), a flue gas exhaust fan (25), a chimney (26), and a drying fan (27).

[0044] A low-grade rhombic and limonite tail suspension magnetization reduction calcination process, as shown in Figure 1, includes the following steps:

[0045] Step 1: Raw material conveying system: Raw material (1) enters the raw material silo (3) through the raw material belt conveyor (2), and is discharged into the raw material quantitative feeder (6) through the electric slide valve (4) at the bottom of the raw material silo. The raw material quantitative feeder (5) can control the hourly feed rate of raw material; after entering the raw material bucket elevator (6) from the raw material quantitative feeder (5), the raw material is dropped into the primary suspension preheater (7) through the raw material bucket elevator (6);

[0046] Step 2: Raw material preheating system: After the raw material enters the first-stage suspension preheater (7), it undergoes gas-solid two-phase heat exchange and separation with the raw material (1) and flue gas (32) from the side outlet of the first-stage preheating mixer (8) in the first-stage suspension preheater (7), and removes some of the attached water from the powdery raw material of hornblende and limonite tailings. The raw material (1) and flue gas (32) discharged from the top of the first-stage suspension preheater (7) enter two parallel first-stage diffusion cyclone dust collectors (22). The material discharged from the bottom of the first-stage suspension preheater (7) and the calcined material (33) and flue gas (32) discharged from the top of the main separator (12) enter the inlet on the side of the bottom of the second-stage preheating mixer (10) for direct heat exchange, so that the raw material (1) and flue gas (32) are in a highly turbulent state in the second-stage preheating mixer (10), the gas-solid two-phase contact area increases, the contact time increases, and the heat exchange is enhanced. The gas and solid phases are brought to a uniform temperature. The raw material (1) and flue gas (32) discharged from the top side of the secondary preheating mixer (10) enter the secondary suspension preheater (9) for further gas-solid heat exchange and separation. A portion of the raw material (1) and flue gas (32) discharged from the top of the secondary suspension preheater (9) and the bottom discharge of the two parallel primary diffusion cyclone dust collectors (22) enter the bottom side inlet of the primary preheating mixer (8) for mixing and direct heat exchange. Another portion of the raw material (1) and flue gas (32) discharged from the top of the secondary suspension preheater (9) enters the bottom side inlet of the primary preheating mixer (8). The raw material (1) discharged from the bottom of the secondary suspension preheater (9) enters the main calcining furnace (11) for oxidation phase change calcination, which transforms Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw material into Fe2O3(a).

[0047] Step 3: Raw material oxidation calcination and reduction system: The raw material (1) discharged from the bottom of the secondary suspension preheater (9) and the ash (34) from the ash return system enter the main calciner (11). The gas (35) in the main calciner (11) comes from the external pipeline gas and is burned to provide phase change reaction heat. After the raw material undergoes a high-temperature phase change reaction in the main calciner (11), it enters the main separator (12). The calcined material (33) discharged from the bottom of the main separator (12) enters the primary plug-flow fluidized bed reducer (13). The primary plug-flow fluidized bed reducer (13) is fed from the top and the reducing gas (36) is introduced from the bottom. The feed of the reducing gas (36) is controlled by the feed body. The flow rate and feed gas pressure are adjusted to regulate the residence time of the calcined material (33) in the primary plug-flow fluidized bed reducer (13), so that the calcined material is fully reduced and cooled. The reduction is that Fe2O3(a) is reduced to magnetic Fe3O4. The reduction waste gas (37) enters the top exhaust pipe of the primary suspension cooler (15), and together with the finished product (38) and combustion air (39) discharged from the top of the primary suspension cooler (15), it enters the bottom of the main calcining furnace (11). The bottom discharge of the primary plug-flow fluidized bed reducer (13) enters the secondary plug-flow fluidized bed reducer (14) for further reduction and... Heat exchange and cooling; the top of the secondary plug-flow fluidized bed reducer (14) is fed, while the bottom is supplied with reducing gas (36). By controlling the feed volume flow rate and pressure of the reducing gas (36), the residence time of the calcined material in the secondary plug-flow fluidized bed reducer (14) is adjusted, so that the calcined material (33) is further fully reduced and cooled by heat exchange. The reduction waste gas (37) enters the top exhaust pipe of the primary suspension cooler (15), and together with the top exhaust product (38) of the primary suspension cooler (15) and the combustion air (39), it enters the bottom of the main calcining furnace (11); the bottom of the secondary plug-flow fluidized bed reducer (14) discharges the finished product (38). 38) The finished product (38) discharged from the top of the secondary suspension cooler (17) and the combustion air (39) enter the bottom side inlet of the primary cooling mixer (16); the calcined material (33) discharged from the bottom of the main separator (12) undergoes reduction phase change and heat exchange and cooling in the two-stage plug flow fluidized bed reducer, and under the protection of reducing gas (36), further prevents the material from undergoing oxidation phase change reaction, and improves the yield of calcined material (33) and the quality of finished material (38); the bottom of the main calciner (11), the primary plug flow fluidized bed reducer (13) and the secondary plug flow fluidized bed reducer (14) are fed through the sampling port (45) for sampling and analysis;

[0048] Step 4: Finished Product Cooling System: The finished product (38) and combustion air (39) discharged from the top of the primary suspension cooler (15) enter the main calcining furnace (11) together with the reduction waste gas (37) from the top of the primary and secondary plug-flow fluidized bed reducers (14); the finished product (38) discharged from the bottom of the primary suspension cooler (15) enters the secondary cooling mixer (11) together with the combustion air (39) and the heat exchange air (41) discharged from the double-blade stirred fluidized bed cooler (19). 8) Bottom inlet; In the secondary cooling mixer (18), the finished material (38) and the combustion air (39) are fully mixed, which further cools the material and further increases the temperature of the combustion air (39); The finished product (38) and the combustion air (39) discharged from the top side of the secondary cooling mixer (18) enter the secondary suspension cooler (17) for further heat exchange and gas-solid separation of the finished material (38) and the combustion air (39); The secondary suspension The top-discharged finished product (38) and combustion air (39) of the float cooler (17) and the bottom-discharged finished product (38) of the secondary plug-flow fluidized bed reducer (14) enter the bottom side inlet of the primary cooling mixer (16) for heat exchange and cooling. Then, the finished product (38) and combustion air (39) from the top side outlet of the primary cooling mixer (16) enter the primary suspension cooler (15); the bottom-discharged finished product (38) of the secondary suspension cooler (17) enters the double-blade cooler. Inside the stirred fluidized bed cooler (19), the top feed of the double-blade stirred fluidized bed cooler (19) comes from the secondary suspension cooler (17), and then the cooling air enters from one side of the double-blade stirred fluidized bed cooler (19). The finished product (38) is fully heated by the cooling air (40) under the stirring of the blades. After the heat exchange, the finished material (38) is discharged from the bottom of the double-blade stirred fluidized bed cooler (19) and enters the finished product silo (21) for storage via the finished product belt conveyor (20).

[0049] Step 5: Raw material dust collection and ash return system: The raw material (1) and flue gas (32) discharged from the top of the primary suspension preheater (17) enter two parallel primary diffusion cyclone dust collectors (22). The flue gas (32) and raw material (1) are dusted once by the two parallel primary diffusion cyclone dust collectors (22). After the first dust removal, the flue gas (32) enters the flue gas waste heat boiler (23) for waste heat recovery and utilization, and reduces the temperature and volume of the flue gas, and generates usable saturated steam. Clean water (42) enters the flue gas waste heat boiler (23) for indirect heating, and then becomes saturated steam (43). The temperature of the saturated steam (43) is 100℃~110℃, which can be used for factory production and domestic use. After being cooled by the waste heat boiler (23), the flue gas (32) enters the secondary bag dust collector (24) for further processing. Secondary dust removal, and then exhaust to the chimney (26) through the flue gas exhaust fan (25); the ash (34) from the waste heat boiler (23) and the secondary bag dust collector (24) enters the main calcining furnace (11) through the pneumatic conveying system for calcination reaction; the pneumatic conveying system includes a pneumatic lifting pump (29) and a Roots blower (28); the drying fan (27) connects to a flue gas outlet pipe from the flue gas inlet pipe of the chimney (26) and sends part of the purified flue gas (44) to the bottom of the raw material bucket elevator (6), and uses the high temperature of the purified flue gas (44) to dry the attached water of the raw material (1) in the raw material bucket elevator (6), thereby reducing the attached water content of the raw material (1) entering the calcination system and reducing the energy consumption of the calcination system; the purified flue gas (44) at the top of the raw material bucket elevator (6) is sent to the primary diffusion cyclone dust collector (22) through the exhaust pipe.

[0050] Example 1

[0051] The siderite tailings are in powder form (particle size distribution 100μm~800μm, attached water content 13%), with a grade of 45.2%. The raw material enters the raw material silo via a conveyor belt, and then exits through an electric gate valve at the bottom of the silo into a quantitative feeder. The quantitative feeder controls the hourly feed rate, adjusting it in real-time according to the load of the calcination system. From the quantitative feeder, the material enters a bucket elevator. Purified flue gas (150℃) is introduced to the bottom of the bucket elevator by a drying fan. The purified flue gas and raw material move upwards together in the bucket elevator, performing initial drying of the attached water, reducing the attached water content by 6%. The material then falls through the bucket elevator into the primary suspension preheater, while the top flue gas enters the primary diffusion cyclone dust collector.

[0052] The initially dried raw materials enter the raw material preheating system, the raw material oxidation calcination and reduction system, and the finished product cooling system. In the raw material preheating system, the temperature of the first-stage suspension preheater is 264℃, the first-stage preheating mixer is 285℃, the second-stage suspension preheater is 362℃, and the second-stage preheating mixer is 390℃, completely removing any attached water from the material. The main furnace calcination temperature is 745℃, causing the Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw materials to oxidize into Fe2O3(a). The calcined material then enters the reduction system, where H2 and CO reducing gases are introduced. The primary plug-flow fluidized bed reducer has an outlet temperature of 530℃, and the secondary plug-flow fluidized bed reducer has an outlet temperature of 300℃, causing the material to undergo Fe2O3(a) reduction to magnetic Fe3O4 under reducing gas. In the finished product cooling system, the primary suspension cooler has a temperature of 242℃, the primary cooling mixer has a temperature of 250℃, the secondary suspension cooler has a temperature of 210℃, and the secondary cooling mixer has a temperature of 220℃, cooling the finished material to lower its temperature. The finished material then enters a double-blade stirred fluidized bed cooler, where it is cooled to 100℃ before being transported to the finished product silo for storage via a finished product conveyor belt. After reduction, the average grade of the siderite tailings reached 53.7%, an increase of 8.5%, and the total iron recovery rate reached 88.6% in magnetic separation tube analysis.

[0053] Example 2

[0054] The siderite tailings are in powder form (particle size distribution 80μm~600μm, attached water content 12%), with a siderite grade of 54.4%. The raw material enters the raw material silo via a conveyor belt, and then exits through an electric gate valve at the bottom of the silo into a quantitative feeder. The quantitative feeder controls the hourly feed rate, adjusting it in real-time according to the load of the calcination system. From the quantitative feeder, the material enters a bucket elevator. Purified flue gas (139℃) is introduced to the bottom of the bucket elevator by a drying fan. The purified flue gas and raw material move upwards together in the bucket elevator, performing initial drying of the attached water, reducing the attached water content by 5%. The material then falls through the bucket elevator into the primary suspension preheater, while the top flue gas enters the primary diffusion cyclone dust collector.

[0055] The initially dried raw materials enter the raw material preheating system, the raw material oxidation calcination and reduction system, and the finished product cooling system. In the raw material preheating system, the temperature of the first-stage suspension preheater is 250℃, the first-stage preheating mixer is 280℃, the second-stage suspension preheater is 350℃, and the second-stage preheating mixer is 380℃, completely removing any attached water from the material. The main furnace calcination temperature is 748℃, causing the Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw material to oxidize into Fe2O3(a). The calcined material then enters the reduction system, where CH4 and CO reducing gases are introduced. The primary plug-flow fluidized bed reducer has an outlet temperature of 520℃, and the secondary plug-flow fluidized bed reducer has an outlet temperature of 290℃, causing the material to undergo Fe2O3(a) reduction to magnetic Fe3O4 under reducing gas. In the finished product cooling system, the primary suspension cooler has a temperature of 230℃, the primary cooling mixer has a temperature of 239℃, the secondary suspension cooler has a temperature of 200℃, and the secondary cooling mixer has a temperature of 210℃, cooling the finished material to lower its temperature. The finished material then enters a double-blade stirred fluidized bed cooler, where it is cooled to 90℃ before being transported to the finished product silo for storage via a finished product conveyor belt. After reduction, the average grade of the siderite tailings reached 65.2%, an increase of 10.8%, and the total iron recovery rate reached 90.4% in magnetic separation tube analysis.

[0056] Example 3

[0057] Brown tailings powder (particle size distribution 80μm~800μm, attached water content 14%), siderite tailings grade 52.5%. The raw materials are fed into the raw material silo via a conveyor belt, and then discharged through an electric gate valve at the bottom of the silo into a quantitative feeder. The quantitative feeder controls the hourly feed rate, adjusting it in real-time according to the load of the calcination system. From the quantitative feeder, the material enters a bucket elevator. Purified flue gas (160℃) is introduced to the bottom of the bucket elevator by a drying fan. The purified flue gas and raw materials move upwards together in the bucket elevator, initially drying the attached water and reducing the water content by 8%. The material then falls through the bucket elevator into the primary suspension preheater, while the top flue gas enters the primary diffusion cyclone dust collector.

[0058] The initially dried raw materials enter the raw material preheating system, the raw material oxidation calcination and reduction system, and the finished product cooling system. In the raw material preheating system, the temperature of the first-stage suspension preheater is 245℃, the first-stage preheating mixer is 270℃, the second-stage suspension preheater is 360℃, and the second-stage preheating mixer is 370℃, completely removing any attached water from the material. The main furnace calcination temperature is 752℃, causing the Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw material to oxidize into Fe2O3(a). The calcined material then enters the reduction system, where CH4 and H2 reducing gases are introduced. The primary plug-flow fluidized bed reducer has an outlet temperature of 525℃, and the secondary plug-flow fluidized bed reducer has an outlet temperature of 285℃, causing the material to undergo Fe2O3(a) reduction to magnetic Fe3O4 under reducing gas. In the finished product cooling system, the primary suspension cooler has a temperature of 225℃, the primary cooling mixer has a temperature of 235℃, the secondary suspension cooler has a temperature of 210℃, and the secondary cooling mixer has a temperature of 220℃, cooling the finished material. The finished material then enters a double-blade stirred fluidized bed cooler, where it is cooled to 105℃ before being transported to the finished product silo for storage via a finished product conveyor belt. After reduction, the average grade of the siderite tailings reached 61.9%, an increase of 9.4%, and the total iron recovery rate reached 92.3% in magnetic separation tube analysis.

[0059] Example 4

[0060] Brown tailings powder (particle size distribution 100μm~1000μm, attached water content 16%), siderite tailings grade 48.5%. The raw materials are fed into the raw material silo via a conveyor belt, and then discharged through an electric gate valve at the bottom of the silo into a quantitative feeder. The quantitative feeder controls the hourly feed rate, adjusting it in real-time according to the load of the calcination system. From the quantitative feeder, the material enters a bucket elevator. Purified flue gas (155℃) is introduced to the bottom of the bucket elevator by a drying fan. The purified flue gas and raw materials move upwards together in the bucket elevator, performing initial drying of the attached water, reducing the attached water content by 6.5%. The material then falls through the bucket elevator into the primary suspension preheater, while the top flue gas enters the primary diffusion cyclone dust collector.

[0061] The initially dried raw materials enter the raw material preheating system, the raw material oxidation calcination and reduction system, and the finished product cooling system. In the raw material preheating system, the temperature of the first-stage suspension preheater is 235℃, the first-stage preheating mixer is 260℃, the second-stage suspension preheater is 350℃, and the second-stage preheating mixer is 360℃, completely removing any attached water from the material. The main furnace calcination temperature is 742℃, causing the Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw material to oxidize into Fe2O3(a). The calcined material then enters the reduction system, where CH4 and H2 reducing gases are introduced. The primary plug-flow fluidized bed reducer has an outlet temperature of 515℃, and the secondary plug-flow fluidized bed reducer has an outlet temperature of 275℃, causing the material to undergo Fe2O3(a) reduction to magnetic Fe3O4 under reducing gas. In the finished product cooling system, the primary suspension cooler has a temperature of 214℃, the primary cooling mixer has a temperature of 228℃, the secondary suspension cooler has a temperature of 205℃, and the secondary cooling mixer has a temperature of 212℃, cooling the finished material. The finished material then enters a double-blade stirred fluidized bed cooler, where it is cooled to 102℃ before being transported to the finished product silo for storage via a finished product conveyor belt. After reduction, the average grade of the siderite tailings reached 59.7%, an increase of 11.2%, and the total iron recovery rate reached 89.4% in magnetic separation tube analysis.

[0062] Example 5

[0063] The raw material is a mixed powder of siderite and brown iron tailings (particle size distribution 80μm~1000μm, attached water content 15%), with a siderite tailings grade of 56.2%. The raw material enters the raw material silo via a conveyor belt, and then exits through an electric gate valve at the bottom of the silo into a quantitative feeder. The quantitative feeder controls the hourly feed rate, adjusting it in real-time according to the load of the calcination system. From the quantitative feeder, the material enters a bucket elevator. Purified flue gas (148℃) is introduced to the bottom of the bucket elevator by a drying fan. The purified flue gas and raw material move upwards together in the bucket elevator, performing initial drying of the attached water, reducing the attached water content by 7.2%. The material then falls through the bucket elevator into the primary suspension preheater, while the top flue gas enters the primary diffusion cyclone dust collector.

[0064] The initially dried raw materials enter the raw material preheating system, the raw material oxidation calcination and reduction system, and the finished product cooling system. In the raw material preheating system, the temperature of the first-stage suspension preheater is 238℃, the first-stage preheating mixer is 256℃, the second-stage suspension preheater is 348℃, and the second-stage preheating mixer is 346℃, completely removing any attached water from the material. The main furnace calcination temperature is 754℃, causing the Fe2O3(r), Fe3O4, and Fe2O3•H2O in the raw materials to oxidize into Fe2O3(a). The calcined material then enters the reduction system, where CH4 is introduced.4、 CO and H2 are used as reducing gases. The primary plug-flow fluidized bed reducer has an outlet temperature of 508℃, and the secondary plug-flow fluidized bed reducer has an outlet temperature of 262℃, causing the material to undergo Fe2O3(a) reduction to magnetic Fe3O4 under the reducing gas. In the finished product cooling system, the primary suspension cooler has a temperature of 202℃, the primary cooling mixer has a temperature of 216℃, the secondary suspension cooler has a temperature of 192℃, and the secondary cooling mixer has a temperature of 202℃, cooling the finished material. The finished material then enters a double-blade stirred fluidized bed cooler, where it is cooled to 92℃ before being transported to the finished product silo for storage via a finished product conveyor belt. After reduction, the average grade of the siderite tailings reached 66.8%, an increase of 10.6%, and the total iron recovery rate reached 91.6% in the magnetic separator analysis.

Claims

1. A suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings, characterized in that, The equipment used in this process includes a raw material conveying system, a raw material preheating system, a raw material oxidation, calcination and reduction system, a finished product cooling system, and a raw material dust collection and ash return system. The raw material conveying system includes a raw material belt conveyor, a raw material silo, a raw material quantitative feeder, and a raw material bucket elevator. The bottom of the raw material silo is equipped with an electric slide gate valve, which is connected to the raw material quantitative feeder. The raw material preheating system includes a primary suspension preheater, a primary preheating mixer, a secondary suspension preheater, and a secondary preheating mixer; The raw material oxidation, calcination and reduction system includes a main separation furnace, a main calcination furnace, a primary plug-flow fluidized bed reducer and a secondary plug-flow fluidized bed reducer; The finished product cooling system includes a primary suspension cooler, a secondary suspension cooler, a primary cooling mixer, a secondary cooling mixer, and a twin-blade stirred fluidized bed cooler. The raw material dust collection and return system includes a primary diffusion cyclone dust collector, a flue gas waste heat boiler, and a secondary bag filter dust collector; the process includes the following steps: (1) Raw material conveying: The raw material is powdery low-grade siderite tailings and limonite tailings. The raw material enters the raw material silo through the raw material belt conveyor and is discharged into the raw material quantitative feeder through the electric slide valve at the bottom of the raw material silo. The raw material quantitative feeder can control the hourly feed rate of the raw material. After passing through the raw material quantitative feeder, the raw material enters the raw material bucket elevator and is then discharged by the raw material bucket elevator into the primary suspension preheater. (2) Raw material preheating: After the raw material enters the first-stage suspension preheater, it undergoes gas-solid two-phase heat exchange and separation with the raw material and flue gas exiting from the side outlet of the first-stage preheating mixer, and removes some of the attached water from the raw material. The raw material and flue gas discharged from the top of the first-stage suspension preheater enter two parallel first-stage diffusion cyclone dust collectors. The material discharged from the bottom of the first-stage suspension preheater and the calcined material and flue gas discharged from the top of the main separator enter the inlet on the side of the bottom of the second-stage preheating mixer for direct heat exchange, so that the raw material and flue gas are in a highly turbulent state in the second-stage preheating mixer. In the first stage, the gas-solid two-phase contact area increases, the contact time increases, and the heat exchange is enhanced, causing the temperatures of the gas and solid phases to tend to be uniform. The raw materials, calcined materials, and flue gas discharged from the top side of the second-stage preheating mixer enter the second-stage suspension preheater for further gas-solid two-phase heat exchange and separation. A portion of the raw materials and flue gas discharged from the top of the second-stage suspension preheater enters the bottom side inlet of the first-stage preheating mixer at the same time as the bottom discharge of the two parallel first-stage diffusion cyclone dust collectors for mixing and direct heat exchange. The other portion of the raw materials and flue gas discharged from the top of the second-stage suspension preheater enters the bottom side inlet of the first-stage preheating mixer. (3) Raw material oxidation, calcination, and reduction: The bottom discharge from the secondary suspension preheater and the ash return from the ash return system enter the main calcining furnace. The fuel gas in the main calcining furnace comes from the external pipeline and is burned to provide heat for the phase change reaction. After high-temperature phase change reaction, oxidation, and hydrolysis in the main calcining furnace, the γ-Fe2O3, Fe3O4, and Fe2O3•H2O in the raw material are converted into α-Fe2O3 before entering the main separation furnace. The bottom discharge from the main separation furnace enters the primary plug-flow fluidized bed reducer. The primary plug-flow fluidized bed reducer is fed from the top and the reducing gas is introduced from the bottom. The reducing gas is controlled by... The feed volume flow rate and feed gas pressure are adjusted to regulate the residence time of the calcined material in the primary plug-flow fluidized bed reducer, ensuring sufficient reduction and heat exchange for cooling. The reduction involves the reduction of α-Fe2O3 to magnetic Fe3O4. The reduction exhaust gas from the top of the primary plug-flow fluidized bed reducer enters the top exhaust pipe of the primary suspension cooler, and together with the finished product and combustion air discharged from the top of the primary suspension cooler, it enters the bottom of the main calcining furnace. The bottom discharge of the primary plug-flow fluidized bed reducer then enters the secondary plug-flow fluidized bed reducer for further reduction and heat exchange for cooling. The secondary plug-flow fluidized bed reducer is fed from the top and circulated with reducing gas from the bottom. By controlling the feed volume, flow rate, and pressure of the reducing gas, the residence time of the bottom discharge from the primary plug-flow fluidized bed reducer within the secondary plug-flow fluidized bed reducer is adjusted, ensuring sufficient reduction and heat exchange for cooling. The reduction exhaust gas from the top of the secondary plug-flow fluidized bed reducer enters the top exhaust pipe of the primary suspension cooler, where it, along with the top exhaust product and combustion air, enters the bottom of the main calcining furnace. The bottom discharge from the secondary plug-flow fluidized bed reducer, along with the top exhaust product and combustion air from the secondary suspension cooler, enters the bottom side inlet of the primary cooling mixer. The bottom discharge from the main separator undergoes reduction phase change and heat exchange for cooling within the two-stage plug-flow fluidized bed reducer, and oxidation phase change is prevented under the protection of the reducing gas. (4) Finished Product Cooling: The finished product and combustion air discharged from the top of the primary suspension cooler, together with the reduction waste gas from the top of the primary and secondary plug-flow fluidized bed reducers, enter the main calcining furnace; the bottom discharge of the primary suspension cooler, together with the combustion air, enters the bottom inlet of the secondary cooling mixer; the finished product and combustion air are thoroughly mixed in the secondary cooling mixer, which further cools the finished product and further increases the temperature of the combustion air; the finished product and combustion air discharged from the top side of the secondary cooling mixer enter the secondary suspension cooler for further heat exchange and gas-solid two-phase separation; the finished product and combustion air discharged from the top of the secondary suspension cooler... Air and the finished product discharge from the bottom of the secondary plug-flow fluidized bed reducer enter the bottom side inlet of the primary cooling mixer for heat exchange and cooling. Then, the finished product and combustion air from the top side outlet of the primary cooling mixer enter the primary suspension cooler. The finished product discharge from the bottom of the secondary suspension cooler enters the double-blade stirred fluidized bed cooler. The top feed of the double-blade stirred fluidized bed cooler comes from the secondary suspension cooler. Then, cooling air enters from one side of the double-blade stirred fluidized bed cooler. The finished product fully exchanges heat with the cooling air under the stirring of the blades. After heat exchange, the finished product is discharged from the bottom of the double-blade stirred fluidized bed cooler and enters the finished product silo for storage via the finished product belt conveyor. (5) Raw material dust collection and ash return: The raw materials and flue gas discharged from the top of the primary suspension preheater enter two parallel primary diffusion cyclone dust collectors. The flue gas and raw materials are subjected to primary dust removal by the two parallel primary diffusion cyclone dust collectors. After primary dust removal, the flue gas enters the flue gas waste heat boiler for waste heat recovery and utilization, reducing the temperature and volume of the flue gas, and generating saturated water vapor at a temperature of 100℃~110℃ for use in factory production and daily life. After being cooled by the waste heat boiler, the flue gas enters the secondary bag filter dust collector for secondary dust removal, and then is discharged through the flue gas exhaust fan. The exhaust gas is discharged to the chimney; the ash from the waste heat boiler and the secondary bag filter is fed into the main calcining furnace for calcination reaction via a pneumatic conveying system; the pneumatic conveying system includes a pneumatic lift pump and a Roots blower; a flue gas outlet pipe is connected to the flue gas inlet pipe of the chimney, and a drying fan is installed on the flue gas outlet pipe to send part of the exhaust gas to the bottom of the raw material bucket elevator, where the high-temperature flue gas dries the attached water of the raw material in the raw material bucket elevator, thereby reducing the attached water content of the raw material entering the calcination system and reducing the energy consumption of the calcination system; the purified flue gas at the top of the raw material bucket elevator is sent to the primary diffusion cyclone dust collector through the exhaust pipe.

2. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The raw materials are powdery siderite tailings and limonite tailings with a particle size distribution of 100μm~1000μm and an attached water content of 12%~15%.

3. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The temperature in the primary suspension preheater is 210℃~280℃, and 10%~20% of the attached water in the raw material is removed in the primary suspension preheater; the temperature in the primary preheating mixer is 220℃~290℃; the temperature in the secondary suspension preheater is 310℃~380℃; the temperature in the secondary preheating mixer is 320℃~390℃, and all the attached water in the raw material is removed in the secondary preheating mixer; the temperature in the main calcining furnace is 645℃~755℃.

4. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The reducing gases include H2, CO, and CH4.

5. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The discharge temperature of the primary plug-flow fluidized bed reducer is 490℃~530℃, and the discharge temperature of the secondary plug-flow fluidized bed reducer is 260℃~300℃.

6. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The finished product in the dual-blade stirred fluidized bed cooler is fully heated by the stirring of the blades and the cooling air. After the cooling air is heated, it is discharged from the other side of the dual-blade stirred fluidized bed cooler and enters the bottom side inlet of the secondary cooling mixer together with the combustion air and the bottom discharge of the primary suspension cooler.

7. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The combustion air velocity in the raw material oxidation calcination and reduction system and the finished product cooling system is 14 m / s to 16 m / s; the flue gas velocity is 14 m / s to 16 m / s.

8. The suspension magnetization reduction calcination process for low-grade siderite tailings and limonite tailings according to claim 1, characterized in that, The temperature of the primary suspension cooler in the finished product cooling system is 210℃~239℃, the temperature of the primary cooling mixer is 220℃~250℃, the temperature of the secondary suspension cooler is 180℃~210℃, and the temperature of the secondary cooling mixer is 190℃~220℃.

Images