Process technology for producing sponge iron through hydrogen reduction by using fluidized bed furnace
By using high-temperature hydrogen reducing gas to reduce iron ore powder in a fluidized bed furnace, and combining cyclone gas-solid separation and plate heat exchanger to purify the reducing gas, a closed-loop system is formed, which solves the problems of low reaction efficiency and high H2 consumption in hydrogen-based ironmaking, and realizes zero-carbon metallurgy and low-cost production of sponge iron.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-03-27
AI Technical Summary
Existing hydrogen-based ironmaking technology faces problems such as low reaction efficiency, high H2 consumption, difficulty in controlling explosion concentration, long process and high investment, making it difficult to achieve commercial operation. In addition, the production of sponge iron using traditional reducing agents produces carbon dioxide and pollutant emissions.
The process of producing sponge iron by hydrogen reduction using a fluidized bed furnace involves crushing and screening iron ore powder and calcining it at 800-1250℃. The iron is then reduced using high-temperature hydrogen reducing gas at around 950℃ to produce sponge iron. The reducing gas is then purified through cyclone gas-solid separation, plate heat exchange, and bag gas-solid separation and recycled. The H2 concentration and temperature of the reducing gas are controlled to form a closed-loop system.
It improves reduction efficiency, reduces H2 consumption, avoids carbon dioxide and pollutant emissions, achieves zero-carbon metallurgy, and the system is safe, reliable, adaptable to flexible production, and reduces investment costs.
Smart Images
Figure CN121737372A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of hydrogen-based ironmaking technology, specifically, it relates to a process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace. Background Technology
[0002] With increasingly stringent environmental and carbon emission standards in the steel industry, the advantages of short-process ironmaking are becoming more and more apparent. Using hydrogen reduction ironmaking is a process option that can truly achieve zero-carbon metallurgy.
[0003] Hydrogen reduction ironmaking, also known as hydrogen-based ironmaking, is a technology that uses hydrogen as a reducing agent to replace coke in traditional blast furnaces to reduce iron ore. This technology has significant environmental advantages because it produces no carbon dioxide emissions and no emissions of pollutants such as sulfur dioxide, nitrogen oxides, dust, wastewater, and VOCs generated during sintering, blast furnace, and coking processes. Although there are currently demonstration projects using hydrogen incorporation in vertical shaft furnaces, blast furnaces, and other methods to verify hydrogen metallurgy, commercial operation faces certain challenges. Improving reaction efficiency, reducing H2 consumption, completely avoiding the explosive concentration range of H2, shortening the ironmaking process, and reducing investment to a competitive level are all issues that need to be addressed.
[0004] Sponge iron is a product made by directly reducing iron ore into metallic iron. This production process usually uses natural gas or coal as a reducing agent and is an important raw material for steelmaking. If hydrogen is used as the reducing agent to produce sponge iron as a raw material for steelmaking, the goal of zero carbon in steel production can be achieved. Summary of the Invention
[0005] To solve the above problems and technical difficulties, this application adopts the following technical solution: a process technology for producing sponge iron using hydrogen reduction in a fluidized bed furnace, comprising the following steps: Step 1: After the crushed and screened iron ore powder (or other metal oxides that can be reduced by hydrogen) is screened and classified, the iron ore powder of the same particle size is continuously added to the rotary calcining kiln. The calcination temperature is 800-1250℃, and the discharge temperature is 850℃. The calcined iron ore powder is discharged into the intermediate silo for temporary storage and then added to the fluidized bed furnace in a timed and quantitative manner. Calcination can also decompose or oxidize the harmful components such as sulfur and phosphorus contained in the iron ore powder into high-temperature gases that are discharged to the waste gas treatment system. Step 2: Iron ore powder is blown into the furnace bottom by a high-temperature reducing gas with hydrogen as the main component at a temperature of about 950°C. The powder is in a uniform boiling state. After 30 to 200 minutes, it is reduced to sponge iron by H2 in the reducing gas. After the reaction is completed, the generated sponge iron is discharged from the boiling furnace into the finished product silo at a timed interval. The temperature is about 900°C. It can be sent directly to the steelmaking process or cooled by the waste heat recovery device and then stored in the finished product warehouse. Step 3: After the high-temperature reducing gas exits the fluidized bed furnace, it first enters the cyclone gas-solid separator. The separated ore automatically flows back into the fluidized bed furnace. The reducing gas enters the plate heat exchanger (hot side) to cool to about 200℃, and then enters the bag gas-solid separator for secondary separation, reducing the dust content of the reducing gas to 5-10 mg / m³. 3 Next, the reducing gas enters the air cooler to exchange heat indirectly with the air for further cooling, and the water produced by the reduction reaction is discharged by the gas-liquid separator. H2 is added to the reducing gas and it is pressurized by the compressor. Then, it enters the plate heat exchanger (cold side) for preheating, raising the temperature to about 640°C. After being heated to 950°C by the electric heater, it is blown in from the bottom of the fluidized bed furnace. After being evenly distributed by the air cap on the gas distributor, it continues to react with the ore in the fluidized bed furnace to form a reducing gas circulation loop.
[0006] Preferably, the iron ore powder obtained by the crushing has irregular particle shape, large specific surface area, fast reaction speed, and high production efficiency. When using raw iron ore as raw material, there are no special requirements for iron content. When the iron content is above 55%, it can have good economic benefits. Of course, the higher the iron content, the higher the reduction efficiency and the better the economic benefits.
[0007] The produced sponge iron has a high iron content, with a total iron content of over 70%. Fe is in the outer layer of the sponge iron particles, while unreduced Fe2O3, Fe3O4, and FeO are in the core of the particles. The H2O molecules produced by the reduction reaction diffuse from the inside of the particles to the outside at high temperature, forming porous sponge iron particles.
[0008] Preferably, iron ore and iron oxides are used as raw materials directly fed into the furnace, without the need for processing techniques such as pelletizing and sintering that would reduce the iron content. Calcination improves the quality of the ore powder, causing harmful components such as sulfur and phosphorus to decompose or oxidize and release gases. There are no additives, resulting in a high-purity product that is beneficial for smelting high-quality steel.
[0009] Preferably, after crushing, the raw iron ore is sieved into three particle sizes: 0.5-1.0, 1.0-2.0, and 2.0-3.5 mm. One particle size is fed into the furnace each time. By adjusting the operating parameters such as the reducing gas pressure, raw material residence time, reaction temperature, and H2 concentration at the bottom of the fluidized bed furnace according to the particle size, the requirements for the reduction of different particle sizes of ore powder in the fluidized bed can be met. Fine ore powder with a particle size of less than 0.5 mm can still be reduced by this fluidized bed furnace after being pelletized, so that the raw iron ore can be fully utilized.
[0010] Preferably, the heat source for the rotary calcining kiln is electrically heated, and a small amount of reducing gas from the fluidized bed furnace is extracted and burned as a supplementary heat source, which is provided by the combustion lance at the kiln head. Preferably, the contents of H2, H2O, and O2 in the reducing gas after the compressor are monitored in real time, and the amount of H2 added is adjusted accordingly to ensure that the H2 concentration is above 70-85%; the cooling air volume of the air cooler is adjusted to regulate the amount of water condensed in the reducing gas to ensure that the H2O content in the reducing gas is 10-21%; the amount of reducing gas diverted to the calcining kiln for combustion is adjusted to discharge O2 and other gases (generally controlled to keep O2 below 0.5%), ensuring that the reducing gas in the entire circulation chain is far away from the H2 explosion concentration range.
[0011] Preferably, the feeding of iron ore powder from the intermediate silo into the fluidized bed furnace and the discharge from the sponge iron bar to the finished product silo are both intermittent operations.
[0012] Preferably, the intermediate silo is equipped with two alternating operation units, one for feeding and the other for discharging, both operating in a closed system, and both the intermediate silo and the feed pipe are equipped with steam sealing devices; Feeding into the intermediate silo: When feeding from the rotary kiln into the intermediate silo, open the upper loading valve of the intermediate silo and the bottom steam valve to continuously introduce steam to expel the air remaining in the intermediate silo and prevent air from entering through the loading port. When feeding is finished, close the upper loading valve, adjust the steam valve to reduce the steam supply, and wait for discharge in a sealed state. During the waiting period for discharge, continuously supply a certain amount of steam to prevent external air from entering the silo. When switching to another intermediate silo, repeat the above feeding steps.
[0013] Discharging from intermediate silos: To discharge from the intermediate silos to the fluidized bed furnace, open the bottom steam valve to introduce steam, open the lower discharge valve of the intermediate silos, and open the feed valve of the fluidized bed furnace to begin discharging. Continuously introduce sealing steam from the bottom, with the steam pressure slightly higher than the furnace pressure (negative pressure) at the inlet to ensure that reducing gas does not enter the silos. After discharging, close the lower discharge valve, close the feed valve of the fluidized bed furnace, close the steam valve, and seal the empty silo to await feeding. When switching to another intermediate silo, repeat the above discharging steps.
[0014] Preferably, when the fluidized bed furnace discharges material to the finished product silo: close the bottom discharge valve of the finished product silo, open the bottom sealing steam valve, open the top exhaust valve, and introduce steam to purge the air inside the finished product silo; open the fluidized bed furnace discharge valve and the finished product silo loading valve, and the reduced sponge iron in the fluidized bed will automatically flow out by gravity to begin discharging; adjust the opening of the sealing steam valve so that the steam pressure inside the finished product silo is slightly higher than the furnace pressure (positive pressure) at the discharge port to ensure that the reducing gas in the furnace does not overflow into the finished product silo; after the discharge is completed, close the fluidized bed furnace discharge valve, close the finished product silo loading valve, and then close the sealing steam valve. The purpose of the above operation is to ensure that the reducing gas in the fluidized bed furnace does not overflow, and to prevent external air from entering the fluidized bed furnace.
[0015] Preferably, the reducing gas discharged from the top of the fluidized bed furnace enters the circulation loop, and after purification, condensation, H2 replenishment, pressurization, and heating, it re-enters the fluidized bed furnace for recycling. After exiting the fluidized bed furnace, the high-temperature reducing gas first enters the cyclone gas-solid separator. The separated ore automatically flows back into the fluidized bed furnace. The reducing gas then enters the plate heat exchanger (hot side) to cool to about 200℃, and then enters the bag gas-solid separator for secondary separation, reducing the dust content of the reducing gas to 5-10 mg / m³. 3 Next, the reducing gas enters the air cooler to exchange heat indirectly with the air for further cooling, and the water produced by the reduction reaction is discharged by the gas-liquid separator. H2 is added to the reducing gas and it is pressurized by the compressor. Then it enters the plate heat exchanger (cold side) for preheating, raising the temperature to about 642°C. After being heated to 950°C by the electric heater, it is blown in from the bottom of the fluidized bed furnace. After being evenly distributed by the air cap on the gas distributor, it continues to react with the ore in the fluidized bed furnace to form a reducing gas circulation loop.
[0016] Preferably, the H2 source for the fluidized bed furnace is green hydrogen, which is produced by electrolyzing water using photovoltaic and wind power; the power and heating electricity is green electricity, which comes from photovoltaic or wind power generation. The factory can be built in western provinces rich in wind and solar power resources, which is conducive to absorbing green electricity and realizing zero-carbon green iron (steel) smelting.
[0017] Preferably, the fluidized bed furnace is easy to shut down and standby, and also easy to start up quickly. When shutting down, only a small amount of hydrogen is needed for heat preservation. The production time and capacity can be flexibly adjusted according to photovoltaic, wind power generation or off-peak electricity prices. During non-production periods, the furnace charge can be emptied for heat preservation and standby (compressor stops running), or the charge level can be lowered for heat preservation and standby (compressor runs at reduced load).
[0018] Preferably, the fluidized bed furnace can use not only H2 as the reducing gas, but also CO2+H2 or coke oven gas (CO+H2) as the reducing gas, with the CO2+H2 reducing gas originating from the cracking of green methanol.
[0019] Furthermore, the particles separated by the cyclone gas-solid separator are directly returned to the fluidized bed furnace to continue the reduction reaction; The minerals recovered from the baghouse gas-solid separator and wastewater treatment are returned to the rotary calcining kiln raw material silo for re-entry into the furnace for reduction.
[0020] Furthermore, the H2 gas consumed during reduction inside the fluidized bed furnace is continuously replenished to the compressor inlet, maintaining the H2 concentration of the circulating reducing gas at a stable level of 70-85% or higher, ensuring that the circulating reducing gas stays far away from the explosive concentration range throughout the entire process.
[0021] Furthermore, the fluidized bed furnace features small size, low investment, fast reaction speed, high production efficiency, and safety and reliability.
[0022] Furthermore, the fluidized bed in the boiler operates under positive pressure; The pressure of the reducing gas blown into the furnace bottom is automatically adjusted according to the height of the fluidized bed, and the required power is provided by the compressor.
[0023] The cyclone gas-solid separator, the hot side of the plate heat exchanger, the bag gas-solid separator, and the air cooler are all operated under negative pressure. The plate heat exchanger operates under positive pressure on the cold side; All devices are closed-loop and in a sealed state to prevent outside air from leaking in.
[0024] The fluidized bed furnace is equipped with an explosion-proof valve according to specifications, and has an automatic overpressure relief valve on the top.
[0025] Compared to existing technologies, the beneficial effects of this application are as follows: This application reduces iron ore powder or other metal oxides with hydrogen at 800-950℃ in a fluidized bed furnace, reducing more than 85% of Fe2O3 to iron. The core of the ore powder contains unreduced Fe2O3, and the outer layer of the particles is spongy Fe. The product can be directly supplied to electric furnaces and converters for steelmaking. Since no auxiliary materials are added, it is beneficial for producing high-quality steel. This application involves crushing the raw iron ore and sieving it into three particle sizes: 0.5-1.0, 1.0-2.0, and 2.0-3.5 mm. Only one particle size can be fed into the furnace at a time. By adjusting the operating parameters such as the reducing gas pressure, raw material residence time, reaction temperature, and H2 concentration at the bottom of the fluidized bed furnace according to the particle size, the requirements for the reduction of different particle sizes of ore powder in the fluidized bed furnace can be met. Fine ore powder with a particle size of less than 0.5 mm can still be reduced by this fluidized bed furnace after being pelletized, so that the raw iron ore can be fully utilized.
[0026] Because the mineral powder particles are small, irregular in shape, and have a large specific surface area, they are in a fluidized boiling state in the fluidized bed furnace. Under high H2 concentration, the diffusion path of H2 into the interior and the diffusion path of the generated H2O molecules from the inside of the particles to the outside at high temperature are short, resulting in fast reaction speed and high reduction efficiency.
[0027] The fluidized bed furnace of this application has a hydrogen reducing atmosphere inside. The hydrogen is produced by electrolysis of water. The power source is photovoltaic or wind power or off-peak electricity price. The factory can be built in western provinces with abundant wind and solar power resources, which is conducive to the consumption of green electricity and the reduction of steelmaking costs. The feed material to the fluidized bed furnace in this application is first calcined in a rotary kiln to 800-1250℃. The high-temperature material is then directly sent to the fluidized bed furnace, and the high-temperature sponge iron after reduction in the fluidized bed furnace is directly sent to the steelmaking process, thus reducing energy consumption.
[0028] The reducing gas discharged from the fluidized bed furnace of this application enters the circulation device, and then undergoes gas-solid separation, cooling and condensation, H2 replenishment and pressurization, heat exchange, and heating before re-entering the fluidized bed furnace for recycling.
[0029] The fluidized bed furnaces in this application all have intermittent feeding and discharging, which is automatically completed by the control logic.
[0030] This application allows for easy shutdown and standby, as well as quick startup. During shutdown, only a small amount of hydrogen is required for heat preservation. Production time and capacity can be flexibly adjusted according to photovoltaic, wind power generation, or off-peak electricity prices. During non-production periods, the furnace charge can be emptied for heat preservation while waiting for production (compressor stops running), or the material level can be lowered for heat preservation while waiting for production (compressor operates at reduced load).
[0031] The system capacity per unit in this application can vary, and the designed capacity can be determined based on the energy supply and raw material scenarios. Attached Figure Description
[0032] In the attached diagram: Figure 1 This is a process flow diagram of an embodiment of this application; Figure 2 This is a schematic diagram of material balance in an embodiment of this application. Figure 1 ; Figure 3 This is a schematic diagram of material balance in an embodiment of this application. Figure 2 ; Figure 4 This is a schematic diagram of material balance in an embodiment of this application. Figure 3 ; Figure 5 This is a schematic diagram of material balance in an embodiment of this application. Figure 4 ; Figure 6 This is a schematic diagram of the heat balance in an embodiment of this application; Figure 7 This is a schematic diagram of water balance in an embodiment of this application. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments. Generally, the components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations.
[0034] Example 1 A process technology for producing sponge iron using hydrogen reduction in a fluidized bed furnace, employing the following apparatus: (1) After the crushed and screened iron ore powder (or other metal oxides that can be reduced by hydrogen) is screened and classified, the iron ore powder of the same particle size is continuously added to the rotary calcining kiln. The calcination temperature is 800-1250℃. The iron ore powder with a temperature of 850℃ after calcination is discharged into the intermediate silo for temporary storage and then added to the fluidized bed furnace in a timed and quantitative manner. At the same time, the rotary calcining kiln decomposes or oxidizes the harmful components such as sulfur and phosphorus contained in the iron ore powder into high-temperature gas and discharges it to the waste gas treatment system. (2) When iron ore powder is blown into the furnace bottom at about 950°C by high-temperature reducing gas with hydrogen as the main component, it is in a uniform boiling state and stays for about 30 minutes. It is reduced to sponge iron by H2 in the reducing gas. The sponge iron generated at 900°C is discharged from the boiling furnace into the finished product silo at regular intervals. It can be sent directly to the steelmaking process or cooled by the waste heat recovery device and then stored in the finished product silo. (3) After the high-temperature reducing gas exits the fluidized bed furnace, it first enters the cyclone gas-solid separator, and the separated ore automatically flows back into the fluidized bed furnace; then, the reducing gas enters the plate heat exchanger (hot side) and is cooled to about 200°C; then it enters the bag gas-solid separator for secondary separation, reducing the dust content of the reducing gas to 5-10 mg / m³. 3 The reducing gas then enters the air cooler for indirect heat exchange with the air, and enters the gas-liquid separator to discharge the water produced by the reduction reaction. After H2 is added, the reducing gas is pressurized by the compressor and re-enters the plate heat exchanger (cold side) to be preheated to about 642°C. Finally, it is electrically heated to 950°C and blown in from the bottom of the fluidized bed furnace. After being evenly distributed by the air cap on the gas distributor, it continues to undergo a reduction reaction with the ore in the fluidized bed furnace, forming a circulating loop of reducing gas. (4) Compressor: H2 is added at the inlet, and the amount added is slightly greater than the amount consumed in the reduction to maintain the relative stability of each component of the circulating gas: H2 accounts for 70%, water vapor accounts for 21%, O2 accounts for 0.5%, and the rest are non-condensable gases, etc.
[0035] Includes the following steps: After crushing and screening, the iron ore powder is classified, and 0.5-1.0mm particles are added to the raw material silo and continuously metered into the rotary calcining kiln. The rotary calcining kiln calcines the iron ore powder to below 800-1250℃. The iron ore powder with a calcination temperature of 850℃ is discharged into the intermediate material silo and then added to the fluidized bed furnace in a timed and quantitative manner. The calcining kiln decomposes and oxidizes non-metallic harmful components such as sulfur and phosphorus at high temperature and discharges them into the waste gas treatment. Iron ore powder is in a boiling state at a high H2 concentration and 950℃ in a fluidized bed furnace. After staying for 30 minutes, it is reduced to sponge iron by H2 in the reducing gas. The generated 900℃ sponge iron is discharged from the lower part of the fluidized bed furnace at regular intervals and sent directly to the steelmaking process or into the cost warehouse. After passing through the waste heat recovery device, it is cooled and stored in the warehouse.
[0036] The total iron content of the iron ore powder is 66%; The highest calcination temperature in the rotary kiln is 800-1250℃, and the reduction temperature in the fluidized bed furnace is 800-950℃. The discharged sponge iron has a total iron content of 84%, with Fe on the outside of the sponge iron particles, and Fe2O3, Fe3O4 and FeO in the core of the particles surrounded by the external Fe. The H2O molecules produced by the reduction reaction diffuse from the inside of the particles to the outside at high temperature, forming porous sponge iron particles.
[0037] The rotary calcining kiln preferentially uses electric heating as the heat source, and the reducing gas from the fluidized bed furnace is used as a supplementary heat source. The supplementary ratio is adjusted to control the concentration of O2 and non-condensable impurities in the reducing gas, which is supplied through the combustion lance at the kiln head.
[0038] The feeding of iron ore powder from the intermediate silo into the fluidized bed furnace and the discharge of sponge iron are both intermittent operations. The intermediate silo of the fluidized bed furnace is equipped with two alternating closed feeding units. The intermediate silo, finished product silo, feed pipe and discharge pipe are all sealed with steam.
[0039] When discharging material from the intermediate silo into the fluidized bed furnace, the following control logic is automatically followed: the bottom sealing steam valve opens, the lower unloading valve opens, material discharge begins, the compressor frequency converter automatically increases the furnace bottom pressure, the lower unloading valve closes when material discharge ends, the steam inlet valve closes, the intermediate silo is sealed and empty and waits, then switches to another intermediate silo to repeat the above operation.
[0040] When discharging material from the fluidized bed furnace to the finished product silo, the following control logic is automatically followed: bottom discharge valve closed, sealing steam valve open, top exhaust valve open, fluidized bed furnace discharge valve open, discharge begins, compressor frequency converter automatically reduces furnace bottom pressure, discharge ends, discharge valve closes, sealing steam valve closes.
[0041] The hydrogen-containing reducing gas from the fluidized bed furnace is recycled in a closed loop.
[0042] The reducing gas discharged from the top of the fluidized bed furnace enters the reducing gas circulation device: after gas-solid separation, cooling and condensation, hydrogen replenishment, pressurization, heat exchange and heating, it re-enters the fluidized bed furnace for recycling. The reducing gas discharged from the top of the fluidized bed furnace first enters the cyclone gas-solid separator, and the separated ore automatically flows back into the fluidized bed furnace. Then, the reducing gas enters the plate heat exchanger (hot side) and is cooled to about 200°C. It then enters the bag filter gas-solid separator for secondary separation, reducing the dust content of the reducing gas to 5-10 mg / m³. 3 The reducing gas then enters the air cooler for indirect heat exchange with the air, and then enters the gas-liquid separator to discharge the water produced by the reduction reaction. After H2 is added to the reducing gas, it is pressurized by the compressor and re-enters the plate heat exchanger (cold side) to be preheated to about 640°C. Finally, it is electrically heated to 950°C and blown in from the bottom of the fluidized bed furnace. After being evenly distributed by the air cap on the gas distributor, it continues to undergo a reduction reaction with the ore in the fluidized bed furnace, forming a circulating loop of reducing gas.
[0043] The bottom inlet temperature of the fluidized bed furnace is greater than or equal to 950℃. The additional heat is provided by an electric heater. The fluidized bed furnace blows in high-temperature hydrogen-containing reducing gas at 950℃ from the bottom of the furnace. The gas is evenly distributed by the air cap on the gas distributor and then recycled. The particles separated by the cyclone gas-solid separator are returned to the fluidized bed furnace to continue the reduction reaction; The mineral powder recovered from the baghouse gas-solid separator and wastewater treatment is then returned to the raw material silo of the rotary calcining kiln to participate in the reduction reaction again.
[0044] The H2 gas consumed during reduction inside the fluidized bed furnace is continuously replenished to the compressor inlet to maintain a relatively stable H2 concentration in the circulating gas.
[0045] The fluidized bed furnace operates under positive pressure. The cyclone gas-solid separator, the hot side of the plate heat exchanger, the bag gas-solid separator, and the air cooler are all operated under negative pressure. The plate heat exchanger operates under positive pressure on the cold side; All devices are closed-loop and in a sealed state to prevent outside air from leaking in.
[0046] The fluidized bed furnace is equipped with an explosion-proof valve according to specifications, and has an automatic overpressure relief valve on the top.
[0047] Monitor the H2, H2O, and O2 content in the reducing gas after the compressor, and adjust the amount of H2 added accordingly to ensure that the H2 concentration is above 70%. Adjust the cooling air volume of the air cooler to regulate the amount of water condensed in the reducing gas to ensure that the H2O content in the reducing gas is less than 21%. Adjust the proportion of reducing gas diverted to the calcining kiln for combustion to discharge O2 and other gases (generally control O2 to be below 0.5%), and ensure that the reducing gas in the entire circulation chain is far away from the H2 explosion concentration range.
[0048] The H2 source for the fluidized bed furnace is green hydrogen, which is produced by electrolyzing water using photovoltaic power generation. Example 2 like Figure 1 As shown, the fluidized bed furnace body 1 includes a reducing gas inlet 22 at the bottom of the fluidized bed furnace body 1, a gas distributor 9 and a wind cap 10 installed on the upper part of the reducing gas inlet 22, a feed inlet 18, a discharge outlet 19 and a return outlet 21 installed in the middle and lower parts of the fluidized bed furnace body 1, a steam sealing device installed on the feed inlet 18 and the discharge outlet 19, and an emergency pressure relief outlet 28 installed on the top of the fluidized bed furnace body 1. The rotary calcining kiln 2 has a raw material silo 3 at its kiln tail, a discharge valve 25 at its raw material silo 3, and a waste gas outlet 26 at its kiln tail. The rotary calcining kiln 2 has a combustion torch 4 at its kiln head and an intermediate material silo 5 at its kiln head. The lower part of the intermediate material silo 5 is connected to the feed inlet 18 of the fluidized bed furnace. The discharge outlet 18 has a discharge valve 23. Discharge valves 24 are installed at the kiln head and the intermediate material silo 5. Two sets of intermediate material silos 5 are provided. Steam is introduced into the intermediate material silos 5 and the feed pipe for sealing and alternating feeding to prevent air from entering the fluidized bed furnace.
[0049] The reducing gas circulation device includes a cyclone gas-solid separator 6, and a discharge valve 23 and a return pipe at the bottom of the cyclone gas-solid separator 6.
[0050] The reducing gas circulation device includes a plate heat exchanger 7, which has four ports: two inlets and two outlets. These ports are connected to the outlet of the cyclone gas-solid separator 6 (hot side inlet), the inlet main pipe of the bag gas-solid separator 29 (hot side outlet), the outlet of the compressor 7 (cold side inlet), and the bottom inlet main pipe of the fluidized bed furnace 1 (cold side outlet).
[0051] The reducing gas air cooler 13 device has an indirect cooling coil inside the air cooler 13, and the external cooling medium of the air cooler 13 is air, which is provided by the cooling fan 14. The hot air after exchange is discharged into the air, and the exhaust gas from the outlet of the air cooler 13 enters the gas-liquid separator 15. The condensate discharged from the bottom of the gas-liquid separator 15 goes to the wastewater treatment system, and the gas from the top of the gas-liquid separator 15 enters the compressor 7 and is circulated into the fluidized bed furnace 1.
[0052] The discharge device of the fluidized bed furnace includes a finished product silo 11, which contains a waste heat recovery device 12. There are two discharge devices: discharge port 19 for normal discharge and discharge port 24 for slag discharge. Discharge ports 19 and 24 are equipped with unloading valves 23. Discharge port 19 has two outlets: one directly sends the hot material to the steelmaking process, and the other sends it to the finished product silo 11 for cooling and stacking.
[0053] Example 3 like Figure 2 , 3 As shown in Figures 4 and 5, 1000 parts of iron ore powder are fed into a rotary calcining kiln. Assuming the proportion of TFe is 66%, after calcination and drying in the rotary calcining kiln, 70 parts of water are discharged. In a fluidized bed furnace, after reduction with 25 parts of pure H2, 730 parts of sponge iron product are obtained, in which the proportion of TFe is 84% and the proportion of elemental Fe is 58%. The 224 parts of water generated by the reduction reaction are cooled by a plate heat exchanger and an air cooler and then discharged to the wastewater treatment system.
[0054] like Figure 6 As shown, the heat Q1 = 0.44 GJ of the raw material discharged to the fluidized bed furnace after passing through the rotary kiln, the heat absorbed by the reduction reaction in the fluidized bed furnace is Q2 = 0.41 GJ, the heat carried by the reducing gas discharged from the fluidized bed furnace is Q3 = 17.7 GJ, the heat carried by the sponge iron discharged from the fluidized bed furnace is Q4 = 0.22 GJ, the heat carried by the reducing gas after passing through the plate heat exchanger and air cooler is Q5 = 13 GJ, the heat carried by the sealing steam is Q8 = 0.028 GJ, and the heat that needs to be supplemented by the heater is Q6 = Q2 + Q3 + Q4 - Q1 - Q5 - Q8 = 4.8 GJ.
[0055] like Figure 7As shown, 70 parts of water evaporate after 1000 parts of iron ore powder raw material are calcined in a rotary kiln, 224 parts of water are generated in the reduction reaction in the fluidized bed furnace, 383 parts of water are carried by the reducing gas circulation from the reducing gas inlet 20 of the fluidized bed furnace, the total amount of water discharged from the top of the fluidized bed furnace is 617 parts, 9 parts of sealing steam are discharged after passing through a plate heat exchanger and an air cooler, and 233 parts of water vapor are condensed and discharged to the wastewater treatment plant.
[0056] illustrate Figure 2-5 Material balance Figure 6 Heat balance Figure 7 The water balance was based on processing 1,000 portions of iron ore powder per hour.
[0057] The embodiments described above are merely preferred embodiments of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of this application, and these all fall within the protection scope of this application.
Claims
1. A process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace, characterized in that, Includes the following steps: Step 1: After crushing and screening, iron ore powder or other metal oxides that can be reduced by hydrogen are screened and classified. Iron ore powder of the same particle size is continuously added to a rotary calcining kiln. The calcination temperature is 800-1250℃ and the discharge temperature is 850℃. The calcined iron ore powder is discharged into an intermediate silo for temporary storage and then added to a fluidized bed furnace in a timed and quantitative manner. Calcination can also decompose or oxidize the harmful components such as sulfur and phosphorus contained in the iron ore powder into high-temperature gases that are discharged to the waste gas treatment system. Step 2: Iron ore powder is blown into the furnace bottom by a high-temperature reducing gas with hydrogen as the main component at a temperature of 950°C. The powder is in a uniform boiling state. After 30 to 200 minutes, it is reduced by H2 in the reducing gas into sponge iron powder. After the reaction is completed, the generated sponge iron is discharged from the boiling furnace into the finished product silo at a timed interval. The temperature is 900°C. It can be sent directly to the steelmaking process or cooled by the waste heat recovery device and then stored in the finished product warehouse. Step 3: After the high-temperature reducing gas exits the fluidized bed furnace, it first enters the cyclone gas-solid separator. The separated ore automatically flows back into the fluidized bed furnace. The reducing gas enters the hot side of the plate heat exchanger to cool to 200℃, and then enters the bag gas-solid separator for secondary separation, reducing the dust content of the reducing gas to 5-10 mg / m³. 3 Next, the reducing gas enters the air cooler to exchange heat indirectly with the air for further cooling, and the water produced by the reduction reaction is discharged by the gas-liquid separator. H2 is added to the reducing gas and it is pressurized by the compressor. Then, it enters the cold side of the plate heat exchanger for preheating, raising the temperature to 640°C. After being heated to 950°C by the electric heater, it is blown in from the bottom of the fluidized bed furnace. After being evenly distributed by the air cap on the gas distributor, it continues to undergo a reduction reaction with the ore in the fluidized bed furnace, forming a circulating loop of reducing gas.
2. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The iron ore powder obtained by the crushing has irregular particle shape, large specific surface area, fast reaction speed, and high production efficiency. When the original iron ore is used as raw material, there are no special requirements for the iron content. When the iron content is above 55%, it can have good economic benefits. The total iron content of the generated sponge iron is above 70%. After crushing, the raw iron ore is sieved into three particle sizes: 0.5-1.0, 1.0-2.0, and 2.0-3.5 mm. Only one particle size can be fed into the furnace at a time. The operating parameters, such as the reducing gas pressure, raw material residence time, reaction temperature, and H2 concentration, are adjusted according to the particle size to meet the reduction requirements of different particle sizes of ore powder within the fluidized bed. Fine ore powder with a particle size less than 0.5 mm is pelletized and then reduced in the fluidized bed furnace, ensuring that the raw iron ore is fully utilized. Using iron ore and iron oxides as raw materials directly into the furnace, without going through the processing technology of pelletizing and sintering which would reduce the iron content, and calcination improves the quality of the ore powder, causing harmful sulfur and phosphorus components to decompose or oxidize and generate gases that escape. Without the addition of auxiliary materials, the resulting product has high cleanliness, which is beneficial for smelting high-quality steel. The highest calcination temperature in the rotary kiln is 800-1250℃, and the reduction temperature in the fluidized bed furnace is 800-950℃.
3. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The rotary calcining kiln preferentially uses electric heating as its heat source, with reducing gas from the fluidized bed furnace as a supplementary heat source. The supplementary ratio is adjusted to control the concentration of O2 and non-condensable impurities in the reducing gas, which is supplied through the combustion lance at the kiln head. The fluidized bed furnace can use not only H2 as the reducing gas, but also CO2+H2 or CO+H2 or coke oven gas as the reducing gas. The CO2+H2 or CO+H2 reducing gas comes from the heating and cracking of methanol.
4. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, All fluidized bed furnaces have intermittent feeding and discharging, which is automatically completed by the control logic and can be started and stopped quickly. When discharging material from the intermediate silo into the fluidized bed furnace, the following control logic is automatically followed: the bottom sealing steam valve opens, the lower unloading valve opens, material discharge begins, the compressor frequency converter automatically increases the furnace bottom pressure, material discharge ends, the lower unloading valve closes, the steam inlet valve closes, the intermediate silo is sealed and empty, and then the process is repeated with another intermediate silo. When discharging material from the fluidized bed furnace to the finished product silo, the following control logic is automatically followed: bottom discharge valve closed, sealing steam valve opened, top exhaust valve opened, fluidized bed furnace discharge valve opened, discharge begins, compressor frequency converter automatically reduces furnace bottom pressure, discharge ends, discharge valve closed, sealing steam valve closed. The intermediate silo is equipped with two alternating sealed feeding units. The intermediate silo, finished product silo, feed pipe and discharge pipe are all equipped with sealed steam sealing devices to prevent external air from leaking in.
5. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The reducing gas discharged from the top of the fluidized bed furnace has a temperature range of 850-900℃. After entering the circulation device, it reaches 950℃ after passing through the electric heater and then enters the bottom of the fluidized bed furnace for recycling. The reducing gas discharged from the top of the fluidized bed furnace enters the cyclone gas-solid separator to separate large particles in the reducing gas, and then enters the plate heat exchanger for cooling. After the reducing gas temperature is cooled to 200°C, it enters the bag gas-solid separator, and then enters the air cooler to cool to 70°C. The H2O generated by reduction is condensed and separated and sent to wastewater treatment. The reducing gas is then sent to the plate heat exchanger for heating by the compressor and continues to be recycled. The bottom air inlet temperature of the fluidized bed furnace is greater than or equal to 950℃, and the additional heat required is provided by an electric heater.
6. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The fluidized bed furnace reduction device is easy to shut down and standby, and also easy to start up quickly. When shutting down, only a small amount of hydrogen is needed for heat preservation. The production time and capacity can be flexibly adjusted according to photovoltaic, wind power generation or off-peak electricity prices. During non-production periods, the furnace charge can be emptied for heat preservation and standby (compressor stops running), or the charge level can be lowered for heat preservation and standby (compressor runs at reduced load).
7. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The content of H2, H2O, and O2 in the reducing gas after the compressor is monitored in real time, and the amount of H2 added is adjusted accordingly to ensure that the H2 concentration is above 70-85%. The cooling air volume of the air cooler is adjusted to regulate the amount of water condensed in the reducing gas, ensuring that the H2O content in the reducing gas is 10-21%. The proportion of reducing gas diverted to the calcining kiln for combustion is adjusted to discharge O2 and other gases, control O2 to below 0.5%, and ensure that the reducing gas in the entire circulation chain is far away from the H2 explosion concentration range.
8. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 5, characterized in that, The particles separated by the cyclone gas-solid separator are then returned to the fluidized bed furnace to continue the reduction reaction. The mineral powder recovered from the baghouse gas-solid separator and wastewater treatment is returned to the raw material silo of the rotary calcining kiln to participate in the reduction reaction again.
9. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The H2 required for reduction inside the fluidized bed furnace is continuously replenished by the compressor inlet, maintaining the H2 concentration in the circulating gas at a level greater than 70-85%.
10. The process technology for producing sponge iron by hydrogen reduction using a fluidized bed furnace according to claim 1, characterized in that, The fluidized bed furnace operates under positive pressure. The cyclone gas-solid separator, the hot side of the plate heat exchanger, the bag gas-solid separator, and the air cooler all operate under negative pressure. The cold side of the plate heat exchanger is under positive pressure; All devices are closed-loop and in a sealed state to prevent outside air from leaking in; The fluidized bed furnace is equipped with an explosion-proof valve according to specifications, and has an automatic overpressure relief valve on the top.