Process for smelting iron from nickel hydrometallurgy slag

Abstract

This invention provides a process for ironmaking from nickel hydrometallurgical slag, relating to the field of laterite nickel ore hydrometallurgical slag treatment technology. The main steps include: S1, filtration and dehydration: Nickel hydrometallurgical slag with a moisture content of 40-70% and a sulfur content of approximately 2.5% is filtered and dehydrated using a filter press until the moisture content is ≤30%; S2, drying and crushing: The hydrometallurgical slag with a moisture content ≤30% is treated by a flash dryer to become dry slag with a moisture content ≤3%; S3, suspension roasting and desulfurization: The aforementioned dry slag is processed through a suspension roasting and desulfurization system to generate oxides such as SO2, Fe2O3, and Fe3O4, reducing the sulfur content in the hot roasted ore to <0.1%. The flue gas is purified by a bag filter before entering the acid production process; S4, smelting and reduction: The hot roasted ore is smelted and reduced in a smelting and reduction furnace to produce iron; S5, iron and slag separation: Molten iron flows out through the tap and enters the next process, either for refining or casting; the slag is discharged through the slag outlet. This process can effectively treat the slag from the hydrometallurgical process of laterite nickel ore, and is more energy-efficient and effective than existing methods.

Description

Technical Field

[0001] This invention relates to the field of utilization technology of laterite nickel ore hydrometallurgical slag, specifically a process for ironmaking from nickel hydrometallurgical slag. Background Technology

[0002] With the booming development of the new energy industry, hydrometallurgical smelting of laterite nickel ore has become a crucial link in the raw material supply chain. Hydrometallurgical slag is a waste product generated during the hydrometallurgical smelting of laterite nickel ore, requiring harmless treatment and proper disposal. Currently, the harmless treatment of hydrometallurgical slag is a major constraint limiting the development of hydrometallurgical smelting of laterite nickel ore. Statistics show that for every 10,000 tons of nickel metal produced, approximately 1-1.2 million tons of hydrometallurgical slag (dry basis) are generated, with a moisture content generally exceeding 30%. Existing disposal methods for hydrometallurgical slag include deep-sea landfill and tailings dam construction, both of which pose significant environmental risks and waste iron resources. If hydrometallurgical slag is not disposed of appropriately, the most serious consequence will be the shutdown of laterite nickel ore hydrometallurgical plants. Deep-sea landfill involves pumping hydrometallurgical slag into the deep sea in slurry form, which will harm the marine environment. Tailings dam construction not only occupies large amounts of land but also incurs high management costs. Improper operation of tailings ponds or extreme weather events could lead to major catastrophic risks such as dam failure, resulting in environmental disasters such as groundwater and surface water pollution. Wet slag contains approximately 45-55% iron; if not effectively utilized, this will result in a waste of iron resources. Currently, the harmless treatment of wet smelting slag is a global challenge. Various countries are researching and developing harmless treatment technologies, but large-scale application has not yet been achieved. Existing technical solutions include the following main steps: S1, filtration and dewatering of wet slag with a moisture content of 40-70% to reduce the moisture content to below 30%; S2, drying and dispersing the wet slag to reduce its moisture content to approximately 3%; S3, after humidification and stirring, the dried slag is sintered using a chain grate machine, and then pelletized using a sintering pelletizing process; S4, the prepared pellets are preheated and partially pre-reduced in a rotary kiln, with the temperature of the hot pellets exiting the kiln controlled at 750-800℃. The charging system delivers hot charge to the blast furnace via a hot charge tank; in S5, hot pellets, coke, and flux enter the blast furnace via a charging machine, fuel is injected through a fuel tank, and hot gas from the hot blast stove enters the furnace to raise the furnace temperature; in S6, iron and slag are separated, with molten iron flowing out of the taphole and into the molten iron ladle; slag is discharged from the slag outlet, and the high-temperature gas is treated and utilized; in S7, blast furnace molten iron is desulfurized by KR stirring to ensure that its sulfur content meets the requirements of subsequent processes. Although this scheme can handle nickel hydrometallurgical slag, it suffers from high energy consumption and severe pollution. Summary of the Invention

[0003] The purpose of this invention is to provide a hydrometallurgical slag treatment method that differs from existing technologies, specifically a process for ironmaking from nickel hydrometallurgical slag. This method achieves the harmless treatment and application of hydrometallurgical slag through processes such as pressure filtration, drying and dispersing, suspension roasting desulfurization, and SRV furnace ironmaking, reducing the steel industry's dependence on iron ore. By utilizing the waste heat and latent heat of high-temperature coal gas in the hydrometallurgical slag drying system, this method significantly reduces energy consumption and production costs. The use of a suspension roasting desulfurization system combined with the HIsmelt ironmaking process eliminates the need for sintering, coking, pelletizing, and complex coal gas reforming systems, reducing heavily polluting processes to some extent, making the technology environmentally friendly. Simultaneously, this solution shortens the smelting process, further reducing energy consumption and contributing to the green and sustainable development of enterprises.

[0004] The technical solution adopted by this invention to solve the technical problem is as follows: a process method for ironmaking from nickel hydrometallurgical slag, mainly including the following steps: S1, hydrometallurgical slag with a water content of 40-70% and a sulfur content of about 2.5% is filtered and dehydrated using a filter press to reduce its water content to ≤30%; S2, the treated slag is fed into a flash dryer via a belt conveyor for drying and crushing to dry the surface of the material; the fine powder that has passed the drying process is conveyed to the subsequent dust collection equipment with the airflow, while the coarser particles fall back to the crushing chamber of the flash dryer for further crushing; the moisture content of the dried slag is ≤3%; S3, the dried slag is treated by a high solid-to-gas ratio suspension preheating roasting system, where all sulfates in the hot dry slag are decomposed to generate oxides such as SO2, Fe2O3, and Fe3O4; after passing through the suspension roasting desulfurization system, the sulfur content in the hot roasted slag is reduced to < 0.1% can meet the requirements of subsequent ironmaking processes for sulfur content in roasted sand; flue gas is purified by a bag filter and then enters the acid production process; S4, the desulfurized hot roasted sand is smelted into iron using the HIsmelt process in a molten reduction furnace (SRV); the hot roasted sand and pulverized coal are sprayed into the molten iron pool in the SRV furnace through special spray guns, and oxygen-enriched hot air is blown in from the top for secondary combustion. By stirring the molten pool, the iron oxide is rapidly reduced; S5, iron and slag are separated, the molten iron flows out through the tapping port and enters the next process for direct refining or casting; the slag is discharged through the slag outlet and can be used as building material after water quenching.

[0005] Furthermore, the wet slag processed in the S1 process 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.

[0006] Furthermore, in the drying and crushing process of S2, the temperature of the drying flue gas is 750±50℃, which is generated by high-temperature coal gas through hot blast stove 1. The coal gas used by hot blast stove 1 is supplied by coal gas generator 1. After the system is running normally, hot blast stove 1 can use all or part of the high-temperature coal gas discharged from SRV furnace. The flash dryer used is equipped with a feeding device to prevent material blockage and collapse, and is equipped with a water circulation cooling system.

[0007] Furthermore, in the S3 suspension roasting desulfurization process, the suspension reaction atmosphere conditions are a CO concentration of about 5%, a reaction time of 5 to 10 seconds, a hot gas temperature at the bottom of the roasting furnace of 800 to 900 degrees Celsius, a hot roasting sand temperature of 750 to 800 degrees Celsius, and a particle size of <5 mm.

[0008] Furthermore, in the S4 ironmaking process, the molten pool temperature is 1600°±50°, the secondary combustion zone temperature is 1200°±50°, and the secondary combustion rate is 50-60%. The upper part of the reduction furnace is an oxidizing atmosphere, while the lower molten pool is a strongly reducing atmosphere. The molten pool is stirred by adjusting the angle and pressure of the spray gun to promote the reduction of iron oxide and the separation of slag and iron.

[0009] Furthermore, in the ironmaking process of S4, the oxygen-enriched hot air injected from the top of the reduction furnace is provided by the hot blast stove 3.

[0010] The beneficial effects of this invention are: the hot roasted sand treated by the suspension roasting desulfurization system can be directly injected into the reduction furnace, resulting in high energy utilization; the produced molten iron is of high quality with low content of harmful components such as S and P; this solution eliminates the need for sintering, coking, pelletizing and complex gas reforming systems, reducing environmental pollution, and the plant occupies a small area, thus reducing investment costs; it can use inexpensive raw materials and fuels, has a short process flow, and low operating and maintenance costs. Attached Figure Description

[0011] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0012] Figure 1 This is a process flow diagram of the existing technical solution, namely the process of nickel hydrometallurgical slag-blast furnace ironmaking.

[0013] Figure 2 This is a process flow diagram of the technical solution of the present invention.

[0014] In the diagram, the direction of material and energy flow is indicated by “——→”, and the direction of flue gas flow is indicated by dashed lines “----→”. Detailed Implementation

[0015] The main equipment used in the process of nickel hydrometallurgical slag ironmaking according to the present invention includes: filter press, belt conveyor, wet silo, belt scale, flash dryer, hot blast stove 1, gas generator 1, bag filter 1, dry silo, screw scale 1, suspension roasting desulfurization system, hot blast stove 2, gas generator 2, bag filter 2, intermediate silo, elevator, hot roasted sand silo, screw scale 2, pulverized coal tank, screw scale 3, hot blast stove 3, gas generator 3, SRV furnace, blower, refining or casting equipment, and electrical and automation system.

[0016] Example 1

[0017] The composition of wet slag sample 1 in this embodiment is as follows (mass percentage). 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 The calorific value of the coal gas is 1360 kcal / Nm³. 3 The composition of the gas is as follows: Element <![CDATA[ CO 2 ]]> CO <![CDATA[ H 2 ]]> <![CDATA[ N 2 ]]> <![CDATA[ CH 4 ]]> Volume percentage / % 3.84 30.48 14.91 49.57 0.49

[0018] The main implementation steps are as follows: Step 1: Using wet slag with a moisture content of 45%, filter it through a filter press to reduce the moisture content of the wet slag from nickel hydrometallurgy to 28%. Step 2: The slag after filter pressing is conveyed to a flash dryer via a belt conveyor. The hot air temperature in the flash dryer is 720°C, and the moisture content of the dried slag is 2.2%. Step 3: The dried slag enters a suspension preheating roasting system. The outlet temperature of the roasting furnace is controlled at 800-850°C, and the atmosphere condition is a CO concentration of 4%. After passing through the suspension roasting system, the temperature of the hot roasted sand is 750-780°C, and the S content is 0.12%. Step 4: The desulfurized hot roasted sand and pulverized coal are injected into the molten iron pool in the SRV furnace through special spray guns. At the same time, oxygen-enriched hot air is blown in from the top for secondary combustion. The oxygen content in the combustion zone is controlled within the range of 35-40%, and the temperature is controlled at around 1200°C. The molten pool temperature is controlled within the range of 1580-1630°C, and the high reducing atmosphere condition is CO. The content is 20%–25%. The rapid reduction of iron oxide is promoted through stirring the molten pool; Step 5: Iron slag separation, the molten iron flows out through the taphole and enters the next process, directly for refining or casting. The molten iron has high purity and the composition is: Si content 0.02%, P content 0.01%, S content 0.02%, Mn content 0.04%. The slag is discharged through the taphole and can be used as building material after water quenching; the waste heat of the hot coal gas is recovered and utilized (the high-temperature coal gas generates hot air at a temperature of 750℃ through a hot blast stove, which is used for the wet slag drying in step S2), completing the entire wet slag ironmaking process.

[0019] Example 2

[0020] The composition of wet slag sample 2 in this embodiment is as follows (mass percentage). 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 The calorific value of the coal gas is 1360 kcal / Nm³. 3 The composition of the gas is as follows: Element <![CDATA[ CO 2 ]]> CO <![CDATA[ H 2 ]]> <![CDATA[ N 2 ]]> <![CDATA[ CH 4 ]]> Volume percentage / % 3.84 30.48 14.91 49.57 0.49

[0021] The main implementation steps are as follows: Step 1: Using wet slag with a moisture content of 48%, filter it through a filter press to reduce the moisture content of the nickel hydrometallurgical slag to 28%. Step 2: The slag after filter pressing is conveyed to a flash dryer via a belt conveyor. The hot air temperature in the flash dryer is 730°C, and the moisture content of the dried slag is 2.8%. Step 3: The dried slag enters a suspension preheating roasting system. The outlet temperature of the roasting furnace is controlled at 820–850°C, and the atmosphere condition is a CO concentration of 4.2%. After passing through the suspension roasting system, the temperature of the hot roasted sand is 750–780°C, and the S content is 0.18%. Step 4: The desulfurized hot roasted sand and pulverized coal are injected into the molten iron pool in the SRV furnace through special spray guns. At the same time, oxygen-enriched hot air is blown in from the top for secondary combustion. The oxygen content in the combustion zone is controlled within the range of 35–40%, and the temperature is controlled at around 1200°C. The molten pool temperature is controlled within the range of 1550–1600°C, and the high reducing atmosphere condition is CO. The content is 20%–25%. Stirring the molten pool promotes rapid reduction of iron oxide. Step 5: Iron and slag separation. Molten iron flows out through the taphole and enters the next process for direct refining or casting. The molten iron has high purity and the composition is: Si 0.02%, P 0.01%, S 0.03%, Mn 0.04%. The slag is discharged through the slag outlet and can be used as building material after water quenching. High-temperature gas is used for waste heat recovery (high-temperature gas generates hot air at 750℃ through a hot blast stove, which is used for drying the wet slag in step S2), completing the entire wet slag ironmaking process.

[0022] The above two embodiments are merely typical embodiments of the present invention, and not all embodiments. Any aspects not detailed herein are conventional technical means known to those skilled in the art. Any modifications, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of the present invention without creative effort should be included within the protection scope of the present invention.

Claims

1. A process for ironmaking from nickel hydrometallurgical slag, characterized in that... The main steps include: S1. Wet slag with a moisture content of 40-70% and a sulfur content of approximately 2.5% is filtered and dehydrated using a filter press to reduce its moisture content to ≤30%. S2. The treated slag is conveyed by a belt conveyor to a flash dryer for drying and crushing, ensuring the material surface is dry. The finely dried powder is transported with the airflow to subsequent dust collection equipment, while coarser particles fall back into the crushing chamber of the flash dryer for further crushing. The moisture content of the dried slag is ≤3%. S3. The dried slag is processed through a high solid-to-gas ratio suspension preheating roasting system, where all sulfates in the hot-dried slag decompose, generating oxides such as SO2, Fe2O3, and Fe3O4. After passing through the suspension roasting desulfurization system, the sulfur content in the hot-roasted slag is reduced to < 0.1%; The flue gas is purified by a bag filter and then enters the acid production process; S4, the desulfurized hot calcined sand is smelted into iron in an SRV furnace using the HIsmelt process; the hot calcined sand and pulverized coal are sprayed into the molten iron pool in the SRV furnace through special spray guns, and oxygen-enriched hot air is blown in from the top for secondary combustion. By stirring the molten pool, the iron oxide is rapidly reduced; S5, the iron and slag are separated. The molten iron flows out through the tap and enters the next process for direct refining or casting; the slag is discharged through the slag outlet and can be used as building material after water quenching.

2. The process for ironmaking from nickel hydrometallurgical slag according to claim 1, characterized in that, The wet slag processed in the S1 process includes leaching slag produced by high-pressure sulfuric acid leaching process, leaching slag produced by atmospheric-pressure sulfuric acid leaching process, leaching slag produced by combined high-pressure and atmospheric-pressure sulfuric acid leaching process, and slag produced by sulfation roasting-water leaching process.

3. The process for ironmaking from nickel hydrometallurgical slag according to claim 1, characterized in that, In the drying and crushing process of S2, the temperature of the drying flue gas is 750±50℃.

4. The process for ironmaking from nickel hydrometallurgical slag according to claim 3, characterized in that, The drying flue gas in the S2 process is generated by high-temperature coal gas through hot blast stove 1. The coal gas used by hot blast stove 1 is supplied by coal gas generator 1. After the system is running normally, hot blast stove 1 can use all or part of the high-temperature coal gas discharged from SRV furnace.

5. The process for ironmaking from nickel hydrometallurgical slag according to claim 3, characterized in that, The flash dryer used in the S2 process is equipped with a feeding device to prevent material blockage and collapse, and a water circulation cooling system.

6. The process for ironmaking from nickel hydrometallurgical slag according to claim 1, characterized in that, In the S3 suspension roasting desulfurization process, the suspension reaction atmosphere conditions are a CO concentration of about 5%, a reaction time of 5 to 10 seconds, a hot gas temperature at the bottom of the roasting furnace of 800 to 900 degrees Celsius, a hot roasting sand temperature of 750 to 800 degrees Celsius, and a particle size of <5 mm.

7. The process for ironmaking from nickel hydrometallurgical slag according to claim 1, characterized in that, In the ironmaking process of S4, the molten pool temperature is 1600°±50°, the secondary combustion zone temperature is 1200°±50°, and the secondary combustion rate is 50-60%. The upper part of the SRV furnace is an oxidizing atmosphere, and the lower molten pool is a strong reducing atmosphere. The molten pool is stirred by adjusting the angle and pressure of the spray gun to promote the reduction of iron oxide and the separation of slag and iron.

8. The process for ironmaking from nickel hydrometallurgical slag according to claim 7, characterized in that, In the ironmaking process of S4, the oxygen-enriched hot air injected from the top of the SRV furnace is supplied by the hot blast stove 3.

Images