Metal mineral powder hydrogen flash direct reduction process

Abstract

The invention relates to the technical field of metal hydrogen-based smelting, and particularly discloses a metal mineral powder hydrogen flash direct reduction process which integrates mineral powder pretreatment, heating, reduction, separation, cooling, metal smelting, waste heat recovery and flue gas purification. The functions of mineral powder suspension heating, flash reduction, metal separation, electric furnace smelting, hydrogen preheating, heat cyclic utilization, environment-friendly emission and the like are achieved, the technological process is highly controllable, the heat energy cyclic utilization rate is high, the requirement for the quality of raw materials is low, the treatment capacity is large, the mineral separation process and the smelting process can be shortened, and the production cost is reduced. The goals of metal mineral dressing and smelting integration and efficient, energy-saving and environment-friendly metal hydrogen-based smelting are achieved, and great economic benefits and social benefits are achieved in the field of metal dressing and smelting.

Description

Technical Field

[0001] The present invention relates to the technical field of metal reduction, and specifically refers to a process for direct flash reduction of metal ore powder with hydrogen gas. Background Art

[0002] Hydrogen-based metallurgy is one of the core technologies for the iron and steel industry to achieve low-carbon transformation. By using hydrogen gas to replace traditional coke as a reducing agent, carbon dioxide emissions can be significantly reduced. Traditional blast furnace ironmaking relies on coke (carbon) to reduce iron ore (Fe2O3), generating CO2, while hydrogen-based metallurgy uses hydrogen gas (H2) to replace carbon, generating water (H2O), theoretically achieving zero carbon emissions.

[0003] The current technical routes are as follows:

[0004] Direct reduced iron (DRI) + electric arc furnace: Hydrogen gas reduces iron ore to produce sponge iron, and then steel is made through an electric arc furnace.

[0005] Hydrogen-based blast furnace: Hydrogen gas is mixed into the blast furnace to partially replace coke (a transitional solution).

[0006] Hydrogen plasma smelting reduction: Hydrogen gas is used as a reducing agent and heat source (frontier exploration).

[0007] Currently, hydrogen-based metallurgy is developed and improved based on existing technical equipment. The entire process is relatively long, the DRI time is also long, and there are relatively high requirements for raw materials.

[0008] The hydrogen flash reduction DRI process is a new approach for fine ore powder DRI, with advantages such as fast reaction speed and short smelting process. However, there is no mature technology and equipment, and it is still in the experimental and exploratory stage.

[0009] Hydrogen-based metallurgy technology has moved from the laboratory to demonstration projects, but it is still in the early stage of large-scale application.

[0010] Therefore, a process for direct flash reduction of metal ore powder with hydrogen gas has become an urgent problem to be solved. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide a process for direct flash reduction of metal ore powder with hydrogen gas. Through steps such as ore powder pretreatment, heating, reduction, separation, heat exchange, smelting, tailings cooling, and flue gas purification, functions such as suspension heating of ore powder, flash reduction, metal separation, electric furnace smelting, hydrogen gas preheating, heat cycle utilization, and environmental protection emissions are achieved, realizing the goals of high efficiency, energy conservation, and environmental protection in metal hydrogen-based smelting. The metal ore powder processed by this process includes but is not limited to heavy metal ore powders such as iron ore powder, copper ore powder, lead ore powder, and zinc ore powder.

[0012] To solve the above technical problems, the technical solution provided by the present invention is: a hydrogen flash direct reduction process for metal ore powder, comprising the following steps:

[0013] S1. Controlled feeding

[0014] The metal ore powder enters the buffer bin in front of the furnace and is controlled by a quantitative metering conveyor to enter a screw feeder or a vibrating feeder and then sent into a Venturi dryer;

[0015] S2. Drying, preheating and tailing rejection

[0016] The metal ore powder removes free water, is preheated and rejects non-metallic tailings through a Venturi dryer, a first-stage drying cyclone separator, a second-stage drying cyclone separator, a first-stage cyclone preheater and a second-stage cyclone preheater;

[0017] S3. Suspension roasting and heating

[0018] The preheated metal ore powder enters the roasting furnace from the lower side and is lifted by high-temperature gas heated by a burner coming in from the bottom of the roasting furnace to be in a suspended state and heated to a temperature above the reduction temperature and below the melting point temperature. The heated metal ore powder is carried upward by the high-temperature gas flow out of the roasting furnace and into a high-temperature cyclone separator;

[0019] S4. Flash direct reduction

[0020] The high-temperature ore powder separated from the high-temperature cyclone separator enters the reduction furnace by gravity flow from the side through an isolator, is suspended by preheated high-temperature hydrogen flowing from bottom to top and moves upward. During this period, hydrogen directly and fully contacts with the high-temperature ore powder for a reduction reaction, and metal oxides are reduced to form metal particles. This process takes about 2 - 4 seconds;

[0021] S5. Heat exchange and separation of metal particles

[0022] The high-temperature metal particles generated in the reduction furnace fall in the lower section of the reduction furnace by their own gravity, exchange heat with hydrogen flowing countercurrently upward during the falling process and are further fully reduced; the heated hydrogen enters the reduction furnace from the lower part of the reduction furnace for flash reduction reaction and carries the unreduced ore powder upward out of the reduction furnace;

[0023] S6. Electric furnace smelting

[0024] The metal particles containing waste heat after heat exchange and separation then fall into the electric furnace at the bottom of the reduction furnace, are further heated and melted into a metal melt, and other impurities are removed by using existing iron and steel smelting technologies;

[0025] S7. Secondary reduction and separation

[0026] The high-temperature ore powder coming out of the reduction furnace undergoes gas-solid separation through two-stage cyclone separators; hydrogen flows from bottom to top and exchanges heat with the self-flowing high-temperature ore powder separated by the first-stage reduction separator in the pipeline and undergoes the second direct reduction reaction. The reduced high-temperature metal particles flow into the electric furnace by gravity for further heating and smelting; the unreduced ore powder is carried by the preheated hydrogen into the second-stage reduction separator for gas-solid separation, and the separated hot hydrogen is sent to the lower part of the reduction furnace to participate in the first reduction; the high-temperature gas containing reduction gas separated by the first-stage reduction separator is sent above the burner at the bottom of the roasting furnace, enters the flue for combustion and then enters the roasting furnace.

[0027] S8. Tailings Cooling and Fresh Air Preheating

[0028] The high-temperature ore powder separated by the second-stage reduction separator enters the multi-stage cyclone cooler configured step by step from top to bottom through the isolator and exchanges heat countercurrently with the cold air, and is discharged as tailings after being cooled to below 80°C; the hot air coming out of the first-stage cyclone cooler is introduced into the lower part of the roasting furnace as combustion-supporting air through the flue, and is heated by the burner installed here and then enters the roasting furnace.

[0029] Furthermore, the high-temperature flue gas carrying the ore powder separated by the first-stage drying cyclone enters the first-stage cyclone preheater, and the high-temperature flue gas separated by the first-stage cyclone preheater enters the second-stage preheating separator for dust removal and then exchanges heat and cools down through the hydrogen preheater.

[0030] Furthermore, the medium-temperature flue gas coming out of the hydrogen preheater enters the bottom of the Venturi dryer, brings the wet ore powder fed by the feeder into the first-stage drying cyclone separator, and the waste flue gas coming out of the first-stage drying cyclone separator enters the waste heat recovery device after recovering dust through the second-stage drying separator.

[0031] Furthermore, the flue gas coming out of the waste heat recovery device enters the dust collector and is sent to the desulfurization device through the exhaust fan to remove sulfides in the flue gas, and is discharged after meeting the environmental protection standards; in the desulfurization device, the limestone powder slurry contacts the sulfuric acid droplets and sulfur dioxide in the sulfur-containing flue gas countercurrently, reacts to generate calcium sulfite which settles to the bottom, and reacts with the air introduced from the outside to generate calcium sulfate (gypsum) and is discharged.

[0032] Furthermore, the hydrogen preheater is a tubular heat exchanger, and hydrogen exchanges heat with the high-temperature flue gas outside the tube inside the tube of the hydrogen preheater to cool down the high-temperature flue gas separated by the second-stage preheating cyclone separator for drying the ore powder; the waste heat recovery device is also a tubular heat exchanger, and the medium-low temperature flue gas outside its tube exchanges heat with the water inside the tube to heat and evaporate the water for waste heat power generation.

[0033] Further, in step S4, a certain amount of ore powder is always retained in the isolator, which plays a sealing role to prevent the hot air in the heating system from coming into contact with the hydrogen in the reduction furnace and causing an explosion; in step S8, a certain amount of ore powder is always retained in the isolator, which plays a sealing role to prevent the reduction gas in the reduction separator from entering the air cyclone cooler and causing an explosion.

[0034] Further, in step S2, the first-stage drying cyclone separator separates the metal ore powder from the non-metal ore powder by using the centrifugal force difference brought by the specific gravity difference of the metal ore powder. The non-metal ore powder enters the second-stage drying separator, and the separated dust is used as tailings, which are drained to the second-stage cyclone cooler for cooling and then discharged externally or drained to the dust collector hopper for external discharge.

[0035] Further, the metal particles falling from step S5 can also enter the water seal discharging device installed at the bottom of the reduction furnace for further cooling, and are sold as metal particle product storage bins, replacing step S6.

[0036] Further, the hydrogen is provided with a hydrogen-containing high-temperature synthesis gas by a methane reforming device, or a high-temperature hydrogen-containing coal gas by a coal gasification device, or high-purity hydrogen from other sources is used.

[0037] Further, the metal ore powder is roasted, heated and reduced in a flowing and suspended state; the metal ore powder is pneumatically transported between different parts, and heat is exchanged in the dense phase and carried in the dilute phase during the transportation of the gas-solid mixture. By controlling the gas flow velocity at different stages and using the principle of the large specific gravity of the metal powder, separation from the unreduced ore powder (non-metal ore powder) is achieved.

[0038] The advantages of the present invention compared with the prior art are as follows: The present invention integrates ore powder pretreatment, heating, reduction, separation, cooling, smelting, waste heat recovery, and flue gas purification. The process flow is highly controllable, the heat energy is recycled, the requirements for raw material quality are low, the processing capacity is large, the ore dressing process and the smelting process can be shortened, the integrated selection and smelting of metal minerals can be realized, and it has great economic and social benefits in the field of metal selection and smelting. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a process flow diagram of a hydrogen flash direct reduction process for metal ore powder of the present invention. The dotted line in the figure is the reduction gas (hydrogen or its synthesis gas), the dashed line is the high-temperature gas flue, and the solid line is the gas-solid mixed flue and pipeline.

[0040] As shown in the figure: 1. Conveyor, 2. Buffer bin, 3. Metering conveyor, 4. Venturi dryer, 5. Vibrating feeder, 6. High-temperature cyclone separator, 7. Roaster, 8. First-stage cyclone preheater, 9. First-stage drying cyclone separator, 10. Second-stage drying cyclone separator, 11. Reduction furnace, 12. Electric furnace, 13. First-stage reduction separator, 14. Second-stage reduction separator, 15. Waste heat recovery device, 16. Isolator, 17. First-stage cyclone cooler, 18. Second-stage cyclone cooler, 19. Second-stage cyclone preheater, 20. Dust collector, 21. Desulfurization device, 22. Exhaust fan. Detailed implementation mode

[0041] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", "vertical", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0042] In the description of the present invention, the "first feature" and "second feature" may include one or more of such features. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0043] In the present invention, unless otherwise clearly defined and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] The following further details a hydrogen flash direct reduction process for metal ore powder according to the present invention with reference to the accompanying drawings.

[0045] Working principle of the present invention: The metal ore powder is suspended and heated by the high-temperature gas heated by the burner in the roasting furnace 7 to generate metal oxides and then transported. It is suspended by high-temperature hydrogen in the reduction furnace 11, and the high-temperature metal oxides are flash-reduced to metal particles. The ore powder is subjected to gas-solid separation in different cyclone separators, pneumatically transported and heat-exchanged in the pipelines between different devices, with dense-phase heat exchange and dilute-phase carrier flow during the transportation of the gas-solid mixture. The air flow velocity in different stages is controlled, and the principle that the reduced metal powder has a relatively large specific gravity is utilized to achieve separation from the unreduced ore powder. The preheated hydrogen (reduction gas) at different stages in the device is sent to the bottom of the reduction furnace 11 and moves upward to react with the high-temperature ore powder in a suspended flash reduction reaction. The fresh air entering from the outside is sent to the lower part of the roasting furnace 7 to heat the suspended roasted ore powder after recovering heat in the cooling section. The exhaust fan 22 provides the power for pneumatic transportation and gas-solid separation of the entire device and supplies the combustion-supporting air for the combustion station. The high-temperature flue gas discharged from the roasting furnace 7 provides the heat energy for hydrogen preheating and ore powder drying preheating. The fresh air exchanges heat with the unreduced high-temperature non-metallic ore powder (tailings), and the heat recovered from the tailings is used as the combustion-supporting gas.

[0046] Combined with the attached Figure 1 , the specific implementation process of a hydrogen flash direct reduction process for metal ore powder of the present invention is as follows:

[0047] A hydrogen flash direct reduction process for metal ore powder includes the following steps:

[0048] S1. Controllable feeding. The metal ore powder enters the buffer bin 2 in front of the furnace through the conveyor 1, and is controlled by the quantitative metering conveyor 3 to enter the screw feeder or vibrating feeder 5 and then sent to the Venturi dryer 4. The conveyor 1 and the vibrating feeder 5 have functions of remote, local control, monitoring, alarm, and interlock; the metering conveyor 3 is equipped with a local PLC system and introduced into the DCS to achieve remote local monitoring, alarm, and interlock functions; the buffer bin 2 is equipped with a level detection instrument, having functions of remote, local monitoring, high and low alarm, and interlock; the Venturi dryer 4 is equipped with inlet and outlet temperature and pressure difference detection instruments, having functions of remote local monitoring and alarm.

[0049] S2. Drying, preheating and tailing discharge. The ore powder is dried to remove free water and preheated through the Venturi dryer 4, the first-stage drying cyclone separator 9, and the first-stage cyclone preheater 8. The first-stage drying cyclone separator 9 separates the metallic ore powder from the non-metallic ore powder by utilizing the centrifugal force difference caused by the specific gravity difference of the ore powder in terms of specifications. The non-metallic ore powder enters the second-stage drying cyclone separator 10 for separation, and the separated dust is used as tailings, which are drained to the ash hopper of the dust collector 20 or discharged after being cooled by the second-stage cyclone cooler 18. The gas separated by the first-stage cyclone preheater 8 enters the second-stage cyclone preheater 19 for further separation of the ore powder therein and then is discharged. Temperature and pressure detection instruments are configured at the top inlets of the first-stage cyclone preheater 8, the first-stage drying cyclone separator 9, the second-stage drying cyclone separator 10, the second-stage cyclone cooler 18, and the second-stage cyclone preheater 19, and temperature detection instruments are configured at the cone outlets to achieve remote monitoring and alarm functions. The dust collector 20 is configured with a PLC and introduced into the DCS to achieve remote and local monitoring, alarm, and interlock functions. An oxygen detector is configured at the flue gas pipeline outlet of the second-stage cyclone preheater 19 to monitor the oxygen content of the roasting flue gas in real time, and the gas volume of the fuel gas is controlled through a loop to ensure safe combustion. Combustible gas detectors such as hydrogen, methane, and carbon monoxide are configured at the flue gas outlet pipeline of the second-stage drying cyclone separator 10 to achieve remote and local monitoring, alarm, and interlock to prevent explosion and deflagration accidents.

[0050] S3. Suspension roasting and heating. The preheated metallic ore powder coming out of the first-stage cyclone preheater 8 flows into the roasting furnace 7 from the lower side of the roasting furnace 7 by gravity due to the position height difference, and is lifted by the high-temperature gas heated by the burner entering from the bottom of the roasting furnace 7 to be in a suspended state and heated to above the reduction temperature and below the melting point temperature to generate metal oxides. The metal ore powder containing metal oxides after heating is carried upward by the high-temperature gas flow out of the roasting furnace 7 and enters the high-temperature cyclone separator 6. Redundant temperature detection instruments and pressure detection instruments are configured at the top and bottom inlets of the roasting furnace 7 to achieve remote, local monitoring, alarm, and interlock functions.

[0051] S4. Flash direct reduction. The high-temperature ore powder separated by the high-temperature cyclone separator 6 flows into the reduction furnace 11 from the side by gravity through the isolator 16, and is suspended and moves upward by the preheated high-temperature hydrogen gas flowing from bottom to top. During this period, hydrogen directly and fully contacts with the high-temperature ore powder for a reduction reaction, and the metal oxides are reduced to form metal particles. This process takes about 2 - 4 seconds. A certain height of ore powder always remains in the isolator 16, and the gas pressure difference at the inlet and outlet ends cannot be exceeded, which plays an isolation and sealing role to prevent the hot flue gas of the heating system from contacting the hydrogen gas in the reduction furnace and causing an explosion. The ore powder that has not undergone the reduction reaction is carried upward by the excess hydrogen gas and reduction waste gas into the first-stage reduction separator 13. Temperature and pressure detection instruments are configured at the inlet and outlet ends of the reduction furnace 11 and the isolator 16.

[0052] S5. Metal particle heat exchange and separation. The high-temperature metal particles generated in the reduction furnace 11 fall in the lower section of the reduction furnace 11 by their own gravity. During the falling process, they exchange heat with the hydrogen flowing countercurrently and are further fully reduced. Flow rate detection instruments, oxygen detection instruments, and hydrogen detection instruments are configured in the upper and lower parts of the reduction furnace 11 to achieve remote, on-site monitoring and interlocking functions, and monitor the temperature, speed, concentration, excess coefficient, and safety of flash reduction.

[0053] S6. Electric furnace smelting. The metal particles containing a large amount of waste heat after heat exchange and separation then fall into the electric furnace 12 at the bottom of the reduction furnace and are further heated and melted into a metal melt, and other impurities are removed using existing iron and steel smelting technologies; the electric furnace 12 is a currently mature smelting device, and temperature, level, current, voltage, and tail gas detection instruments are configured to achieve remote and on-site monitoring functions.

[0054] S7. Secondary reduction and separation. The high-temperature ore powder coming out of the reduction furnace 11 undergoes gas-solid separation through two-stage cyclone separators; hydrogen flows from bottom to top and exchanges heat with the high-temperature ore powder flowing down by gravity separated by the first-stage reduction separator 13 in the pipeline and undergoes a second direct reduction reaction. The reduced high-temperature metal particles flow into the electric furnace 12 by gravity for further heating and melting; the unreacted ore powder (non-metallic tailings powder) is carried by the preheated hydrogen into the second-stage reduction separator 14 for gas-solid separation, and the separated hot hydrogen is sent to the lower part of the reduction furnace 11 to participate in the first reduction; the high-temperature gas containing reduction gas separated by the first-stage reduction separator 13 is sent above the burner at the bottom of the roasting furnace 7, enters the flue for combustion and then enters the roasting furnace 7; temperature, pressure, oxygen, and hydrogen detection instruments are configured at the inlets of the first-stage reduction separator 13 and the second-stage reduction separator 14 to achieve remote and on-site monitoring functions.

[0055] S8. Tailings cooling and fresh air preheating. The high-temperature tailings powder separated by the second-stage reduction separator 14 passes through the isolator 16 and flows into the multi-stage cyclone cooler configured step by step from top to bottom by gravity and exchanges heat countercurrently with cold air, and is cooled to below 80°C and discharged from the system as tailings. The preheated air coming out of the first-stage cyclone cooler 17 is introduced into the lower part of the roasting furnace 7 as combustion-supporting air through the flue, and is heated by the burner installed here and then enters the roasting furnace 7; a certain height of ore powder always remains in the isolator 16, and the pressure difference at the inlet and outlet cannot be exceeded to prevent the reduction gas in the reduction separator from entering the air cyclone cooler and causing an explosion. Temperature and pressure detection instruments are configured at the inlets and outlets of the multi-stage cyclone cooler to achieve remote and on-site monitoring functions.

[0056] S9. Tailings treatment. If the metal content in the tailings still has recycling value, it can be sorted again, and the selected concentrate enters the furnace front buffer bin 2 again;

[0057] S9. Hydrogen preheating. The high-temperature flue gas separated from the high-temperature separator 6 and carrying the ore powder from the first-stage drying separator 9 enters the first-stage cyclone preheater 8. The high-temperature flue gas separated from the first-stage cyclone preheater 8 enters the second-stage preheating separator 19 for dust removal and then exchanges heat and cools down through the hydrogen preheater. This hydrogen preheater is a tubular heat exchanger. Hydrogen exchanges heat with the high-temperature flue gas outside the tubes inside the tubes of the hydrogen preheater, cooling down the high-temperature flue gas separated from the second-stage preheating cyclone separator to medium-temperature flue gas for drying the ore powder. Temperature and pressure detectors are configured at the inlet and outlet ends of the flue gas of the hydrogen preheater, a hydrogen detector is configured at the flue gas outlet end, and temperature and pressure detectors are configured at the inlet and outlet ends of hydrogen to achieve remote, on-site monitoring, and interlocking functions.

[0058] S10. Flue gas waste heat recovery. The medium-temperature flue gas coming out of the hydrogen preheater enters the bottom of the Venturi dryer 4, bringing the wet ore powder fed in by the feeder into the first-stage drying cyclone separator 9. The waste flue gas coming out of the first-stage drying cyclone separator 9 enters the waste heat recovery device 15 after recovering dust through the second-stage drying separator. This waste heat recovery device 15 is a tubular heat exchanger. The medium-low temperature flue gas outside its tubes exchanges heat with the water inside the tubes, heating and evaporating the water for waste heat power generation. Temperature and pressure detectors are configured at the inlet and outlet ends of the flue gas of the waste heat recovery device 15, a hydrogen detector is configured at the flue gas outlet end, and temperature and pressure detectors are configured at the inlet and outlet ends of water to achieve remote, on-site monitoring, and interlocking functions.

[0059] S11. Flue gas purification. The flue gas coming out of the waste heat recovery device 15 enters the dust collector 20 and is sent to the desulfurization device 21 through the main induced / draft fan 22 to remove sulfides in the flue gas and then discharged after meeting the environmental protection standards; the limestone powder slurry in the desulfurization device 21 contacts the sulfuric acid droplets and sulfur dioxide in the sulfur-containing flue gas countercurrently and reacts to generate calcium sulfite, which settles to the bottom and reacts with the air introduced from the outside to generate calcium sulfate (gypsum) and is discharged. The dust collector 20 and the exhaust fan 22 are configured with an on-site PLC system as a complete set of devices and introduced into the DCS monitoring. Temperature, sulfide, and dust detection instruments are configured at the inlet and outlet of the flue gas of the desulfurization device 21 to achieve remote, on-site monitoring, and interlocking functions.

[0060] S12. Discharge of collected dust. The dust collected by the dust collector 20 is discharged as tailings.

[0061] In an embodiment of the present application, the metal particles falling from step S5 can also enter the water seal device installed at the bottom of the reduction furnace for further cooling and be sold as a metal particle product storage bin, replacing step S6.

[0062] Preferably, the roasting furnace 7 is configured with a main combustion station for providing heat for heating the ore powder, using natural gas or coal gas as fuel. The temperature for heating the ore powder is determined according to different metal ore powders. The principle is that the roasting temperature is less than the melting point of the metal ore powder and greater than the reduction temperature of the metal ore powder with hydrogen.

[0063] Preferably, the hydrogen is provided with a hydrogen-containing high-temperature synthesis gas by a methane reforming device, or a high-temperature hydrogen-containing coal gas is provided by a coal gasification device, or high-purity hydrogen is used.

[0064] In the present invention, the mentioned drying cyclone separator, cyclone preheater, cyclone cooler, high-temperature cyclone separator, etc. are non-standard cyclones designed according to the processing capacity of the device, the properties of the ore powder, and the flow rate, and are applied to different process parts to achieve the function of gas-solid separation.

[0065] In an embodiment of the present application, the metal ore powder is roasted, heated, and reduced in a flowing and suspended state; the metal ore powder is pneumatically transported between different parts, and heat exchange occurs in the dense phase and carrier flow in the dilute phase during the transportation of the gas-solid mixture, and the gas flow velocity in different stages is controlled. Utilizing the principle that the specific gravity of the metal and the ore powder is large, the separation from the non-metal ore powder is achieved.

[0066] In the present invention, the fineness of the metal ore powder is determined according to the reduction experiment of the ore powder particles.

[0067] During the entire process of the present invention, the temperature, pressure, flow rate, flow, level, and composition of the solid ore powder, gas, and gas-solid mixture are detected throughout the process, and the DCS system is used for control to perform process control and monitoring, and the required safety interlocks and equipment protection interlocks are set to ensure the safe operation of the system.

[0068] The present invention integrates low-carbon metallurgy technology, direct reduction smelting technology, hydrogen direct reduction smelting technology, flash reduction smelting of powdered minerals with hydrogen, and integrated metal ore dressing and metallurgy.

[0069] In the present invention, the roasting and reduction of the metal ore powder occur in different containers. The powdered mineral is heated to a temperature above the reduction temperature by the roasting furnace 7 and then flows by gravity from the high position to the lower reduction furnace 11, where it is suspended by high-temperature hydrogen and undergoes a flash reduction reaction.

[0070] The present invention utilizes the principle that the specific gravity of the reduced metal powder is greater than that of its oxide, and separates them with an appropriate wind speed during the material transportation process.

[0071] The present invention realizes multiple reductions of the metal ore powder to recover the metal in the ore powder to the greatest extent. The reducing hydrogen undergoes the first reduction with the high-temperature ore powder in the reduction furnace 11. During the falling process of the reduced metal powder, it undergoes reverse heat exchange movement with the preheated hydrogen in the pipeline at the lower part of the reduction furnace, and further reaction of the iron powder particles that have not fully reacted is achieved; the reduced metal powder is sent to the electric furnace 12 for smelting and then sent to the next process.

[0072] The incompletely reduced ore powder separated from the reduction furnace 11 undergoes a reduction reaction with hydrogen again in the cooling section to ensure that the metal oxides in the ore powder can be reduced and recovered to the maximum extent, while recovering heat. The high-temperature flue gas containing the reduction gas separated after reduction is sent to the bottom inlet of the roasting furnace 7 for combustion, and the ore powder enters the roasting furnace 7 for suspension roasting.

[0073] The reduction hydrogen required by the present invention can be provided with a hydrogen-containing high-temperature synthesis gas by a methane reforming device, or a high-temperature hydrogen-containing coal gas can be provided by a coal gasification device to make full use of the heat in the high-temperature synthesis gas. High-purity hydrogen can also be used.

[0074] The cooling section of the present invention is divided into two sections. In one section, the fresh air inhaled by the device and the reduced ore powder undergo countercurrent heat exchange through multi-stage cyclone cooling. The heated hot air is sent to the roasting furnace for combustion support and suspension, and the cooled ore powder (less than 80 °C) is sent to the magnetic separator to recover the reduced magnetic minerals again. In the other section, the reduction gas sent from the outside undergoes countercurrent and cyclone cooling with the reduced ore powder. A second reduction reaction and metal powder separation are carried out at this stage. The heated reduction gas is sent to the reduction furnace, and the cooled metal powder is sent to the electric furnace 12 for smelting and then sent to the next process.

[0075] The ore powder processed by the present invention is realized in a flowing and suspended state. The ore powder is pneumatically transported between different parts of the device, and dense-phase heat exchange and dilute-phase carrier flow occur during the transportation of the gas-solid mixture. By controlling the gas flow velocity at different stages and using the principle that the reduced metal powder has a large specific gravity, the separation from the unreduced ore powder is achieved.

[0076] The present invention realizes the integration of ore dressing and smelting, can process medium and low-grade ore powder in the ore dressing stage to generate metal substances, shortens the ore dressing process, and the tailings produced from the roasting furnace 7 have activity due to high-temperature roasting and can become building material raw materials, greatly reducing the cost of tailings management.

[0077] This process estimates the costs of fuel and reduction gas with reference to the reduction gas and fuel consumption of the iron ore magnetization roasting device. The relevant calculations are as follows:

[0078] 1. For a magnetization roasting device using coal gasification as fuel and reduction gas to reduce iron oxide (Fe2O3) to magnetite (Fe3O4), 104 kg of coal (5500 kcal) is consumed for processing each ton of ore powder (iron content 45%). In theory, the present invention requires 104×3 = 312 kg of coal to reduce iron oxide to metallic iron. Considering the excess atmosphere for complete reduction, the actual coal consumption for processing one ton of ore powder is calculated at 67% excess, and the required coal consumption is about 520 kg. Then the cost of fuel and reduction gas is about 500 yuan / T (ore powder);

[0079] 2. Taking hydrogen production by steam reforming of natural gas as an example, when reducing iron(III) oxide (Fe2O3) to iron(II,III) oxide (Fe3O4), theoretically about 40 cubic meters of natural gas (with a calorific value of 7000 kcal) is consumed for treating each ton of ore powder (with an iron content of 45%). The device theoretically needs to consume 40×3 = 120 cubic meters of natural gas to reduce iron oxide to metallic iron. Considering the excess atmosphere for complete reduction, when actually treating one ton of ore powder with a 67% excess calculation, the natural gas consumption is about 200 cubic meters. If the unit price of natural gas is calculated at 3 yuan, then the cost of fuel and reducing gas is about 200×3 = 600 yuan / T (ore powder);

[0080] Thus, it can be seen that this process can save production costs and has great economic and social benefits in the field of metal beneficiation and smelting.

[0081] The above describes the present invention and its implementation manners. Such description is not restrictive. What is shown in the drawings is only one of the implementation manners of the present invention. Due to the significant differences in the physical and chemical properties of different metal ore powders, the actual structure is not limited thereto. All stages of this process device need to be increased, decreased, and optimized specifically. Generally speaking, if those of ordinary skill in the art are inspired by it and design, without creative efforts, structural manners and embodiments similar to this technical solution without departing from the gist of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A process for direct flash reduction of metal ore powder with hydrogen, characterized in that, It includes the following steps: S1. Controllable feeding The metal ore powder enters the buffer bin in front of the furnace and is controlled by a quantitative metering conveyor to enter the screw feeder or vibrating feeder and then be sent into the Venturi dryer; S2. Drying, preheating and tailing rejection The metal ore powder removes free water, is preheated and rejects non-metallic tailings through the Venturi dryer, the first-stage drying cyclone separator, the second-stage drying cyclone separator, the first-stage cyclone preheater, and the second-stage cyclone preheater; S3. Suspension roasting and heating The preheated metal ore powder enters the roasting furnace from the lower side and is lifted by the high-temperature gas heated by the burner coming in from the bottom of the roasting furnace to be in a suspended state and heated to above the reduction temperature and below the melting point temperature. The heated metal ore powder is carried upward by the high-temperature gas flow out of the roasting furnace and enters the high-temperature cyclone separator; S4. Flash direct reduction The high-temperature ore powder separated from the high-temperature cyclone separator enters the inside of the reduction furnace by gravity flow from the side through the isolator, is suspended and moves upward by the preheated high-temperature hydrogen gas flowing from bottom to top. During this period, hydrogen gas directly and fully contacts the high-temperature ore powder for a reduction reaction to generate metal particles. This process takes about 2 - 4 seconds; S5. Heat exchange and separation of metal particles The high-temperature metal particles generated in the reduction furnace fall in the lower section of the reduction furnace by their own gravity. During the falling process, they exchange heat with the hydrogen gas flowing countercurrently upward and are further fully reduced; the heated hydrogen gas enters the reduction furnace from the lower part of the reduction furnace for flash reduction reaction and takes the unreduced ore powder upward out of the reduction furnace; S6. Electric furnace smelting The metal particles containing waste heat after heat exchange and separation then fall into the electric furnace at the bottom of the reduction furnace, are further heated and melted into a metal melt, and other impurities are removed; S7. Secondary reduction and separation The high-temperature ore powder coming out of the reduction furnace undergoes gas-solid separation through two-stage cyclone separators; the hydrogen gas flows from bottom to top and exchanges heat with the high-temperature ore powder flowing down by gravity separated from the first-stage reduction separator in the pipeline and undergoes a second direct reduction reaction. The reduced high-temperature metal particles fall into the electric furnace by gravity for further heating and melting; the unreactive ore powder is carried by the preheated hydrogen gas into the second-stage reduction separator for gas-solid separation. The separated hot hydrogen gas is sent to the lower part of the reduction furnace to participate in the first reduction; the high-temperature gas containing reduction gas separated from the first-stage reduction separator is sent above the burner at the bottom of the roasting furnace, enters the flue for combustion and then enters the roasting furnace; S8. Tailings cooling and fresh air preheating The high-temperature ore powder separated from the second-stage reduction separator enters the multi-stage cyclone cooler arranged step by step from top to bottom through the isolator and exchanges heat countercurrently with cold air, and is cooled to below 80 °C and discharged as tailings; the hot air coming out of the first-stage cyclone cooler is introduced into the lower part of the roasting furnace as combustion-supporting air through the flue, and is heated by the burner installed here and then enters the roasting furnace.

2. A hydrogen flash direct reduction process for metal ore powder according to claim 1, characterized in that: The high-temperature flue gas separated from the roasting furnace carries the ore powder coming out of the first-stage drying cyclone into the first-stage cyclone preheater. The high-temperature flue gas separated from the first-stage cyclone preheater enters the second-stage preheating separator for dust removal and then exchanges heat and cools down through the hydrogen preheater.

3. A direct reduction process for hydrogen flash smelting of metal ore powder according to claim 2, characterized in that: The medium-temperature flue gas coming out of the hydrogen preheater enters the bottom of the Venturi dryer, and brings the wet ore powder fed by the feeder into the first-stage drying cyclone separator. The waste flue gas coming out of the first-stage drying cyclone separator enters the waste heat recovery device after the dust is recovered by the second-stage drying separator.

4. A direct reduction process of metal ore powder by hydrogen flash roasting according to claim 3, characterized in that: The flue gas coming out of the waste heat recovery device enters the dust collector and is sent to the desulfurization device via the induced draft fan to remove the sulfides in the flue gas, and is discharged after meeting the environmental protection standards.

5. A direct hydrogen flash reduction process for metal ore powder according to claim 4, characterized in that: The hydrogen preheater is a tubular heat exchanger. Hydrogen exchanges heat with the high-temperature flue gas outside the tubes inside the hydrogen preheater, and reduces the high-temperature flue gas separated by the second-stage preheating cyclone separator for drying the ore powder; the waste heat recovery device is also a tubular heat exchanger. The medium and low-temperature flue gas outside its tubes exchanges heat with the water inside the tubes to heat and evaporate the water for waste heat power generation; the flue gas after recovering the waste heat passes through the desulfurization device again to remove the sulfides in the flue gas, and then is discharged; in the desulfurization device, the limestone powder slurry contacts the sulfuric acid droplets in the sulfur-containing flue gas countercurrently, reacts to generate calcium sulfite which settles to the bottom, and reacts with the air introduced from the outside to generate calcium sulfate and is discharged.

6. A direct hydrogen flash reduction process for metal ore powder according to claim 5, characterized in that: In step S4, a certain height of ore powder always remains in the isolator. The height of this ore powder is based on the principle that the gas pressure difference between the inlet and outlet cannot be exceeded, which plays a sealing role to prevent the oxygen-containing hot flue gas in the heating system from contacting the hydrogen in the reduction furnace and causing an explosion. In step S8, a certain height of ore powder always remains in the isolator. The height of this ore powder is based on the principle that the gas pressure difference between the inlet and outlet cannot be exceeded, which plays a sealing role to prevent the reducing gas in the reduction separator from entering the air cyclone cooler and causing an explosion.

7. A direct reduction process of metal ore powder by hydrogen flash smelting according to claim 6, characterized in that: In step S2, the first-stage drying cyclone separator separates the metal from the non-metal in the metal ore powder by using the centrifugal force difference brought by the specific gravity difference of the metal ore powder. The non-metal ore powder enters the second-stage drying separator. The dust separated by the second-stage drying cyclone separator is used as tailings, which is drained to the second-stage cyclone cooler for cooling and then discharged, or drained to the dust collector hopper and then discharged.

8. A direct reduction process for hydrogen flash smelting of metal ore powder according to claim 7, characterized in that: The metal particles falling from step S5 can also enter the water seal discharging device at the bottom of the reduction furnace for further cooling, and are sold as metal particle product storage bins, replacing step S6.

9. A hydrogen flash direct reduction process for metal ore powder according to claim 8, characterized in that: The hydrogen is provided with a hydrogen-containing high-temperature synthesis gas by a methane reforming device, or a high-temperature coal gas containing hydrogen and carbon monoxide by a coal gasification device, or high-purity hydrogen is used.

10. A direct reduction process for hydrogen flash of metal ore powder according to claim 9, characterized in that: The metal ore powder realizes movement and reduction in a flowing and suspended state; the metal ore powder is pneumatically transported between different parts, and heat is exchanged in the dense phase and carried in the dilute phase during the transportation of the gas-solid mixture. The gas flow velocity in different stages is controlled, and the principle that the reduced metal powder has a large specific gravity is used to realize the separation from the unreduced ore powder.

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