A method for producing hot-pressed iron nuggets from laterite nickel ore hydrometallurgy slag

Abstract

This invention provides a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag, belonging to the field of laterite nickel ore hydrometallurgical slag utilization technology. The process includes the following steps: S1, pressure filtration and water removal, reducing the moisture content of the wet slag to ≤30%; S2, drying and crushing, reducing the moisture content of the dried slag to ≤5%; S3, preheating, decrystallization, sulfate decomposition, and desulfurization, generating SO2 gas and hot-roasted sand containing oxides such as Fe2O3, Fe3O4, and CaO; S4, the hot-roasted sand is reduced in a multi-stage fluidized bed consisting of a second-stage pre-reduction fluidized bed and a third-stage final reduction horizontal bubbling fluidized bed, using H2 as the reducing agent. After reduction in the second and third-stage reduction fluidized beds, the degree of reduction reaches 65-85% and the metallization rate is >93%, respectively; S5, the reduced iron powder from the third-stage final reduction horizontal bubbling fluidized bed is processed into hot-pressed iron blocks by a hot-pressing device. The purified high-temperature flue gas is then recycled in the burner of a flash heater, thus utilizing the wet smelting slag of laterite nickel ore.

Description

Technical Field

[0001] This invention belongs to the field of utilization technology of laterite nickel ore hydrometallurgical slag, specifically a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag. Background Technology

[0002] Hydrometallurgy offers advantages such as low energy consumption and high metal recovery rates, making it the preferred smelting method for lower-grade lateritic nickel ore. Producing one ton of metallic nickel generates 120-160 tons of hydrometallurgical slag. Current disposal methods for lateritic nickel ore hydrometallurgical slag mainly include deep-sea landfilling and tailings dam construction, both of which pose significant environmental risks. If large quantities of lateritic nickel ore hydrometallurgical slag are not disposed of appropriately, they could force related smelting enterprises to cease production. Furthermore, lateritic nickel ore hydrometallurgical slag contains approximately 45-55% iron; if not effectively utilized, this will result in a waste of iron resources. Currently, the harmless treatment of lateritic nickel ore hydrometallurgical slag is a global challenge. Various countries are researching and developing harmless treatment technologies, but none have yet achieved large-scale application. Summary of the Invention

[0003] This invention provides a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag, which effectively solves the problem of serious environmental pollution caused by the large-scale stockpiling or seabed landfill of hydrometallurgical slag, and also realizes its resource utilization.

[0004] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: A method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag, comprising the following main steps: Step S1, the laterite nickel ore hydrometallurgical slag is filtered and dehydrated using a filter press, reducing the moisture content to ≤30%; Step S2, the treated hydrometallurgical slag is fed into a drying and crushing machine via a belt conveyor for drying and dispersing. The qualified dried fine powder is conveyed to the subsequent dust collection equipment with the airflow, while the coarser particles fall back into the crushing chamber for further crushing; the waste gas is discharged and dried. The flue gas is heated by a hot blast stove, and the moisture content of the dried slag after treatment is ≤5%. In step S3, the dried slag enters the first-stage preheating circulating fluidized bed for preheating. First, the crystal water is removed, and then the sulfate is decomposed to generate SO2 gas and hot calcined sand containing oxides such as Fe2O3, Fe3O4, and CaO, as well as sulfur content <0.1%. The hot calcined sand enters the second-stage pre-reduction fluidized bed. The process flue gas containing SO2 is then treated to produce acid. The main reactions in this process are as follows: 2Fe2(SO4)3 → 2Fe2O3 + 6SO2 + 3O2; 6Fe2O3 → 4Fe3O4 + O 2； 2CaSO4 → 2CaO + 2SO2 + O2; Step S4: After desulfurization, the hot calcined sand enters the hot calcined sand silo via belt conveyor and elevator. The hot calcined sand is then reduced in a multi-stage fluidized bed consisting of a second-stage pre-reduction fluidized bed and a third-stage final reduction horizontal bubbling fluidized bed. ；After passing through the second-stage pre-reduction fluidized bed, the flue gas dust is further processed by a cyclone separator. The collected dust is returned to the second-stage pre-reduction fluidized bed. The high-temperature flue gas undergoes gas heat exchange, and the recovered heat energy is provided to the burners of the second-stage pre-reduction fluidized bed and the third-stage final reduction horizontal bubbling fluidized bed for continued use. The reduced gaseous water is cooled and discharged. In this step, after passing through the second-stage pre-reduction fluidized bed, the reduction degree of the hot-roasted calcined sand reaches 65-85%. After passing through the third-stage final reduction horizontal bubbling fluidized bed, the metallization rate of the reduced iron product is >93%. The main reactions in this process are as follows: Fe2O3+3H2→2Fe+3H2O; Fe3O4+4H2→3Fe+4H2O. In step S5, the reduced iron powder from the third-stage final reduction horizontal bubbling fluidized bed passes through a flash heater and is then conveyed to the top of the discharge system by an elevator. The reduced iron powder is made into hot-pressed iron blocks by a hot-pressing device. The purified high-temperature flue gas enters the burner of the flash heater for secondary utilization.

[0005] Preferably, in step S3, the temperature at which the water of crystallization in the dry slag is removed in the first-stage preheated circulating fluidized bed is 480±50℃, and the temperature at which the sulfate completes its decomposition is 900±50℃.

[0006] Preferably, in step S3, the first-stage preheating circulating fluidized bed has a vertical structure.

[0007] Preferably, in step S4, the gas flow rate in the second-stage pre-reduction fluidized bed is 4-6 m / s, the temperature in the fluidized bed is 630-650℃, the residence time of the hot-roasted sand is 20-30 min, and the operating pressure is 0.4 MPa.

[0008] Preferably, in step S4, the gas flow rate in the third-stage final reduction horizontal bubbling fluidized bed is 0.5-0.6 m / s, the temperature in the fluidized bed is 630-650℃, the residence time is 45-120 min, and the operating pressure is 0.4 MPa.

[0009] Preferably, in step S4, H2, which serves as a reducing agent, is produced using an alkaline electrolytic cell.

[0010] Preferably, in step S5, the flash heater uses preheated H2 as the heating medium.

[0011] Preferably, in step S5, the reduced iron powder is heated to a temperature of 700–715°C.

[0012] Preferably, in step S1, the laterite nickel ore hydrometallurgical slag includes leaching slag produced by the high-pressure sulfuric acid leaching process (HPAL process), leaching slag produced by the atmospheric pressure sulfuric acid leaching process, leaching slag produced by the combined high-pressure and atmospheric pressure sulfuric acid leaching process, and slag produced by the sulfation roasting-water leaching process.

[0013] This invention employs direct reduction technology, sequentially processing laterite nickel ore hydrometallurgical slag through pressure filtration, dewatering, drying, crushing, three-stage fluidized bed preheating, decrystallization, desulfurization, pre-reduction, and final reduction to produce hot-pressed iron blocks from reduced iron powder. Using hydrogen as the reducing agent, this process eliminates sintering, coking, pelletizing, and the complex gas reforming system, reducing heavily polluting processes. The technology is environmentally friendly, promoting clean production and CO2 emission reduction. 2； This method can produce high-purity pig iron with low phosphorus and sulfur content and zero carbon content from laterite nickel ore hydrometallurgical slag, effectively solving the environmental pollution problem caused by the large-scale stockpiling or seabed landfill of hydrometallurgical slag. In this method, the reduction temperature in the second-stage pre-reduction fluidized bed and the third-stage final reduction horizontal bubbling fluidized bed is only 630-650℃. This low-temperature reduction reaction not only saves energy but also avoids particle adhesion. The production setup of this method is flexible. In addition to producing hot-pressed iron blocks (HBI) that are easy to transport and store, it can also produce hot and cold sponge iron (DRI), which can be directly sent to electric furnaces or converters. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] Picture 1 This invention provides a process flow diagram for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag. Detailed Implementation

[0016] [Example 1]

[0017] This embodiment describes a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag. The method was tested on a pilot plant for smelting sponge iron from hydrometallurgical slag. The pilot plant had a capacity of 0.8 to 1.4 tons of sponge iron per hour. The equipment operated continuously for 24 hours, and the test period lasted 7 days, producing a total of 190 tons of sponge iron.

[0018] The composition of sample 1, a hydrometallurgical slag from laterite nickel ore, is as follows: Ni Co Mn Mg Fe Al Ca Si Cr Na C S 0.108 0.011 0.112 0.242 51.448 1.985 0.065 3.411 2.403 0.073 0.060 2.14

[0019] Specifically, the implementation steps are as follows: Step S1, pressure filtration and water removal to reduce the moisture content of the wet smelting slag to below 30%; Step S2, drying and dispersing, ensuring the moisture content of the dried slag is ≤5%; In step S3, the dry slag enters the first-stage preheated circulating fluidized bed at approximately 480–500°C to remove the crystal water. It is then heated to 880–900°C, completing sulfate decomposition. The generated SO2 gas is purified and sent to the acid production system. The hot-roasted sand enters the roasting silo via a belt conveyor and elevator. In step S4, the hot-roasted sand undergoes pre-reduction in the second-stage pre-reduction fluidized bed. The gas flow rate is controlled at 4–6 m / s, the temperature at 630–650°C, and the residence time at 20–30 min, achieving a pre-reduction degree of 68–82%. Then, the hot-roasted sand undergoes final reduction in the third-stage horizontal bubbling fluidized bed. The gas flow rate is controlled at 0.5–0.6 m / s, the temperature at 630–650°C, and the residence time at 60–90 min, resulting in a metallization rate of approximately 94.3%. H2 is used as the sole reducing agent, produced in an alkaline electrolytic cell. In step S5, the reduced iron powder from the third-stage horizontal bubbling fluidized bed passes through a flash heater and is then conveyed to the top of the discharge system by an elevator. The reduced iron powder is then processed into hot-pressed iron blocks (HBI) by a hot-pressing device. The purified high-temperature flue gas enters the burner of the flash heater for secondary utilization.

[0020] [Example 2]

[0021] This embodiment describes a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag. The method was tested on a pilot plant for smelting sponge iron from hydrometallurgical slag. The pilot plant had a capacity of 0.8 to 1.4 tons / hour of sponge iron. The relevant parameters were adjusted, and the equipment ran continuously for 24 hours. The test period was 5 days, and a total of 138 tons of sponge iron was produced.

[0022] The composition of sample 2, a hydrometallurgical slag from laterite nickel ore, is as follows: Ni Co Mn Mg Fe Al Ca Si Cr Na C S 0.099 0.011 0.13 0.631 51.458 1.877 0.002 3.515 2.365 0.132 0.050 2.44

[0023] The specific implementation steps are as follows: Step S1, pressure filtration and dewatering to reduce the moisture content of the wet smelting slag to below 30%; Step S2, drying and dispersing, the moisture content of the dried slag is ≤5%; Step S3, the dried slag enters the first-stage preheating circulating fluidized bed at approximately 480-500℃ to remove the crystal water, and is further heated to 900-920℃ to complete sulfate decomposition. The generated SO2 gas is purified and sent to the acid production system, and the hot calcined sand enters the calcined sand bin via belt conveyor and elevator; Step S4, the hot calcined sand undergoes pre-reduction in the second-stage pre-reduction fluidized bed, controlling the gas flow rate in the fluidized bed at 4-6 m / s, the temperature in the fluidized bed at 630-650℃, and the residence time of the hot calcined sand at 25-30 minutes. The pre-reduction degree can reach 71-84%; then, the hot-calcined sand undergoes final reduction in the third-stage horizontal bubbling fluidized bed, controlling the gas flow rate in the fluidized bed at 0.5-0.6 m / s, the temperature in the fluidized bed at 630-650℃, and the residence time at 80-110 min, with a metallization rate of approximately 95.6% for the reduced product; H2 is used as the sole reducing agent, and H2 is produced in an alkaline electrolytic cell; in step S5, the reduced iron powder from the third-stage horizontal bubbling fluidized bed passes through a flash heater and is then conveyed to the top of the discharge system by an elevator. The reduced iron powder is then made into hot-pressed iron blocks (HBI) by a hot pressing device, and the purified high-temperature flue gas enters the burner of the flash heater for secondary utilization.

[0024] The above two embodiments describe a method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to the present invention. Contents not described in detail in the specification are all prior art or common knowledge well known to those skilled in the art. The above description is not restrictive, and actual implementation methods are not limited thereto. For those skilled in the art, any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention without creative design of similar structural methods and embodiments should be included within the protection scope of the present invention.

Claims

1. A method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag, characterized in that... The main steps include: Step S1, the wet smelting slag of laterite nickel ore is filtered and dehydrated using a filter press, reducing the moisture content to ≤30%; Step S2, the treated wet slag is conveyed to a drying and crushing machine via a belt conveyor for drying and dispersing. The fine powder that meets the drying requirements is transported to the subsequent dust collection equipment with the airflow, while the coarser particles fall back to the crushing chamber for further crushing; the exhaust gas is discharged externally, and the drying flue gas is heated by a hot air furnace, resulting in a dry slag moisture content of ≤5%; Step S3, the dry slag enters the first-stage preheating circulating fluidized bed for preheating, first removing the crystal water, and then heating to decompose the sulfate, generating SO2 gas and hot calcined sand containing oxides such as Fe2O3, Fe3O4, and CaO, as well as sulfur content <0.1%. The hot calcined sand enters the second-stage pre-reduction fluidized bed, and the process flue gas containing SO2 is treated to produce acid; the main reaction occurring in this process is 2Fe2(SO4)3 → 2Fe2O3 + 6SO2 + 3O2; 6Fe2O3 → 4Fe3O4 + O 2； 2CaSO4→2CaO + 2SO2+ O2; Step S4: After desulfurization, the hot calcined sand enters the hot calcined sand silo via belt conveyor and elevator. The hot calcined sand is then reduced in a multi-stage fluidized bed consisting of a second-stage pre-reduction fluidized bed and a third-stage final reduction horizontal bubbling fluidized bed. ； After passing through the second-stage pre-reduction fluidized bed, the flue gas dust is further processed by a cyclone separator. The collected dust is returned to the second-stage pre-reduction fluidized bed. The high-temperature flue gas undergoes gas heat exchange, and the recovered heat energy is provided to the burners of the second-stage pre-reduction fluidized bed and the third-stage final reduction horizontal bubbling fluidized bed for continued use. The reduced gaseous water is cooled and discharged. In this step, after passing through the second-stage pre-reduction fluidized bed, the reduction degree of the hot-roasted calcined sand reaches 65-85%. After passing through the third-stage final reduction horizontal bubbling fluidized bed, the metallization rate of the reduced iron product is >93%. The main reactions in this process are as follows: Fe2O3+3H2→2Fe+3H2O; Fe3O4+4H2→3Fe+4H2O. In step S5, the reduced iron powder from the third-stage final reduction horizontal bubbling fluidized bed passes through a flash heater and is then conveyed to the top of the discharge system by an elevator. The reduced iron powder is made into hot-pressed iron blocks by a hot-pressing device. The purified high-temperature flue gas enters the burner of the flash heater for secondary utilization.

2. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 1, characterized in that: In step S3, the temperature at which the water of crystallization in the dry slag is removed in the first-stage preheated circulating fluidized bed is 480±50℃, and the temperature at which the sulfate completes its decomposition is 900±50℃.

3. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 2, characterized in that: The first-stage preheating circulating fluidized bed has a vertical structure.

4. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 1, characterized in that: In step S4, the gas flow rate in the second-stage pre-reduction fluidized bed is 4-6 m / s, the temperature in the fluidized bed is 630-650℃, the residence time of the hot-roasted sand is 20-30 min, and the operating pressure is 0.4 MPa.

5. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 4, characterized in that: The gas flow rate in the third-stage final reduction horizontal bubbling fluidized bed is 0.5–0.6 m / s, the temperature inside the fluidized bed is 630–650℃, the residence time is 45–120 min, and the operating pressure is 0.4 MPa.

6. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 4, characterized in that: H2, used as a reducing agent, is produced in an alkaline electrolytic cell.

7. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 1, characterized in that: In step S5, the flash heater uses preheated H2 as the heating medium.

8. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 7, characterized in that: The heating temperature for reducing iron powder is 700–715℃.

9. The method for producing hot-pressed iron blocks from laterite nickel ore hydrometallurgical slag according to claim 1, characterized in that: In step S1, the slag from the hydrometallurgical process of laterite nickel ore includes leaching slag produced by the high-pressure sulfuric acid leaching process, leaching slag produced by the atmospheric pressure sulfuric acid leaching process, leaching slag produced by the combined high-pressure and atmospheric pressure sulfuric acid leaching process, and slag produced by the sulfation roasting-water leaching process.

Images