A gasification reduction ironmaking system and method for the co-processing of solid and hazardous waste with red mud

Abstract

This invention discloses a gasification reduction ironmaking system and method for the synergistic resource utilization of solid and hazardous waste and red mud. The system includes a raw material pretreatment unit, a pyrolysis gasification and purification unit, a gasification reduction ironmaking unit, and a waste heat comprehensive utilization unit. After pretreatment, the solid and hazardous waste enters a multi-stage gasifier for pyrolysis and gasification reactions. Combined with a two-stage gas-solid separation and return structure, the gas yield and carbon conversion rate are improved. The gasified gas enters the reduction furnace and pre-reduction furnace for cascade reduction, realizing the efficient recovery of iron resources from red mud. The waste heat comprehensive utilization unit performs multi-stage heat exchange on the tail gas and uses it for the preparation of gasifying agents, realizing closed-loop heat utilization. This invention constructs a multi-cycle system of gas, heat, and materials, realizing the recycling of gas, heat, and materials. It not only improves the resource utilization rate but also obtains tail gas rich in methane, achieving the synergistic and efficient resource utilization of solid and hazardous waste and red mud.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and metallurgical engineering technology, and in particular to a gasification reduction ironmaking system and method for the synergistic resource utilization of solid and hazardous waste and red mud. Background Technology

[0002] Solid waste includes household waste, kitchen waste, agricultural and forestry waste, biochemical sludge, chemical organic waste, and medical waste, among which solid waste possessing one or more hazardous characteristics such as corrosivity, toxicity, flammability, reactivity, or infectivity is classified as hazardous waste. With the acceleration of industrialization, the amount of solid and hazardous waste generated continues to increase, becoming a significant factor restricting the sustainable development of the ecological environment.

[0003] Currently, the main methods for treating solid hazardous waste include landfill and incineration power generation. Among these, incineration power generation is the most widely used method, but it still faces the following problems in practical application: On the one hand, due to the complex composition of solid hazardous waste, it is difficult to achieve complete combustion during the combustion process, which easily produces toxic and harmful substances such as dioxins and heavy metals, posing a significant environmental risk; on the other hand, the excess air coefficient during the incineration process is high, resulting in a large amount of heat energy being emitted with the flue gas, leading to low energy utilization efficiency. At the same time, the large amount of fly ash produced increases the difficulty of subsequent treatment and easily causes secondary pollution.

[0004] Furthermore, red mud generated during alumina production is a typical bulk industrial solid waste, characterized by its strong alkalinity, high water content, and high compressibility. Current methods for treating red mud primarily involve stockpiling, which not only occupies significant land resources but also easily leads to alkali leakage during long-term storage, polluting soil and water bodies. Regarding resource utilization, while red mud can be used in building materials, environmental protection materials, and for extracting valuable elements, most applications remain in the experimental or demonstration stages, with a low level of industrialization. In particular, the iron resources contained in red mud have not yet been efficiently utilized.

[0005] Meanwhile, biomass and organic solid waste, as a renewable energy source, have the characteristics of wide availability and low carbon emissions. However, the existing utilization methods are mainly direct combustion for power generation or liquefaction for fuel production. Direct combustion has low thermal efficiency and poor economic performance, while liquefaction technology is greatly affected by cost and market fluctuations, making it difficult to achieve stable promotion.

[0006] In existing technologies, solid and hazardous waste gasification technology and metallurgical reduction technology are usually set up independently, lacking an effective coupling mechanism. This results in the combustible gas generated by gasification not being used efficiently in the reduction process, the system heat not being utilized in stages, and the lack of a synergistic treatment path between red mud and solid and hazardous waste, leading to low overall resource utilization and energy efficiency.

[0007] Therefore, how to achieve the synergistic treatment of solid and hazardous waste and red mud, construct an integrated gasification and reduction resource utilization system, improve gas utilization efficiency and heat utilization efficiency, and achieve efficient recovery of iron resources in red mud has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The technical problem to be solved by this invention is to provide a gasification reduction ironmaking system and method for the synergistic resource utilization of solid and hazardous waste and red mud.

[0009] To solve the above-mentioned technical problems, the present invention provides a gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud, comprising: The raw material pretreatment unit is used for crushing and granulating solid hazardous waste. The pyrolysis gasification and purification unit includes a gasifier and a gas-solid return structure. The gasifier includes a fluidized bed section, a pyrolysis section, a cracking section and a sedimentation separation section from bottom to top along the height direction. A slag temperature regulation section is provided on one side of the gasifier and is connected to the pyrolysis section. The gas-solid return structure is used to separate the gas-solid mixture from the gasifier and send the solid particles back to the gasifier. The gasification reduction ironmaking unit includes a red mud feeding structure, a slag cooler, a pre-reduction furnace, and a reduction furnace. The red mud feeding structure is connected to the slag cooler. The gas inlet of the reduction furnace is connected to the gas outlet of the gas-solid return structure. The gas inlet of the pre-reduction furnace is connected to the gas outlet of the reduction furnace. The slag outlet of the reduction furnace is connected to the slag cooler. The red mud feeding structure is connected to the pre-reduction furnace, and the slag outlet of the pre-reduction furnace is connected to the reduction furnace. The waste heat comprehensive utilization unit includes an air blower, a primary air preheater, a waste heat boiler, a mixed gas preheater, a secondary air preheater, and an air-steam mixer. The outlet of the air blower is connected to the primary air preheater, the primary air preheater is connected to the waste heat boiler, the waste heat boiler is connected to the mixed gas preheater, the mixed gas preheater is connected to the secondary air preheater, the air-steam mixer is connected to the secondary air preheater and the waste heat boiler, the gas outlet of the pre-reduction furnace is connected to the gas inlet of the secondary air preheater, the gas outlet of the slag cooler is connected to the gas inlet of the mixed gas preheater, and the outlet of the air-steam mixer is connected to the fluidized bed section.

[0010] Preferably, the raw material pretreatment unit includes a raw material silo, a series of iron separators, a raw material conveyor belt, a primary crusher, a secondary crusher, a feeding device, and a twin-helix shaftless feeder. The raw material silo and the primary crusher are connected by the raw material conveyor belt. The series of iron separators are suspended above the raw material conveyor belt. The outlet of the primary crusher and the inlet of the secondary crusher are connected. The secondary crusher and the inlet of the twin-helix shaftless feeder are connected by the feeding device. The outlet of the twin-helix shaftless feeder is connected to the middle of the gasifier. The feeding device is a feeding hopper or a granulator.

[0011] Preferably, the gas-solid return structure includes a primary gas-solid separator, a primary return feeder, a secondary gas-solid separator, a secondary return feeder, and a return fan. The outlet of the gasifier is connected to the inlet of the primary gas-solid separator. The solid feed pipe of the primary gas-solid separator is connected to the fluidized bed section through the primary return feeder. The gas outlet of the primary gas-solid separator is connected to the inlet of the secondary gas-solid separator through a pipeline. The solid feed pipe of the secondary gas-solid separator is connected to the slag temperature control section through the secondary return feeder. The return fan is connected to the primary return feeder and the secondary return feeder through pipelines respectively. Both the air fan and the return fan are oxygen generators.

[0012] Preferably, the red mud feeding structure includes a red mud powder silo, a red mud powder screw feeder, and an air conveying fan. The outlet of the red mud powder silo is connected to the inlet of the red mud powder screw feeder. The outlet of the red mud powder screw feeder is connected to the air inlet section of the air conveying fan through a pipeline. The outlet of the air conveying fan is connected to the slag cooler. The air conveying fan feeds the red mud powder into the slag cooler.

[0013] Preferably, the outlet of the secondary return feeder is connected to the slag temperature control section. A conical outlet with an inclined axis is provided on one side of the bottom of the slag temperature control section. The small end of the conical outlet is inserted into the dry distillation section. An inlet connected to the outlet of the secondary return feeder is provided on the top side of the slag temperature control section away from the conical outlet. An oxygen-enriched gas input pipe is connected to the inlet of the slag temperature control section. The slag temperature control section has a double-layer water jacket structure.

[0014] Preferably, the top of the settling and separation section is constricted relative to the bottom, the diameter of the pyrolysis section is smaller than the diameter of the bottom of the settling and separation section, the furnace bricks of the pyrolysis section have a corrugated structure and are inlaid with catalyst, the diameter of the middle part of the dry distillation section is larger than that of the upper and lower parts, the raw material pretreatment unit is connected to the middle part of the dry distillation section, the bottom of the fluidized bed section has a slag chamber, and the diameter of the bottom of the fluidized bed section is larger than that of the top.

[0015] Preferably, the slag chamber at the bottom of the fluidized bed section is equipped with a water jacket, which is connected to a demineralized water input pipe. The water jacket is connected to a waste heat boiler, and the outlet of the waste heat boiler is connected to a steam delivery pipe.

[0016] The present invention provides a gasification reduction ironmaking method for the co-processing of solid and hazardous waste with red mud, which is based on the aforementioned gasification reduction ironmaking system for the co-processing of solid and hazardous waste with red mud. Specifically, it includes the following steps: S1, the solid and hazardous waste is crushed by the raw material pretreatment unit. S2. The crushed material is fed into the gasifier for gasification. S3. The gas generated by the gasifier is fed into the gasification reduction ironmaking unit. The red mud powder is fed into the gasification reduction ironmaking unit through the red mud feeding structure. The reduction ironmaking reaction is carried out in the gasification reduction ironmaking unit. The iron is magnetically separated from the slag after the reaction. S4. The tail gas after the reduction ironmaking reaction is sent to the waste heat comprehensive utilization unit for waste heat utilization.

[0017] The present invention discloses a gasification reduction ironmaking method for the co-utilization of solid and hazardous waste with red mud, based on the aforementioned gasification reduction ironmaking system for the co-utilization of solid and hazardous waste with red mud, specifically comprising the following steps: S1. Solid hazardous waste is crushed and processed by the raw material pretreatment unit; S2. The crushed material is fed into the dry distillation section of the gasifier. The small molecule gas and solid material produced fall and react with the gasifying agent in the fluidized bed section. The gas and particulate solid material rise to the pyrolysis section, where they are pyrolyzed to generate small molecule pyrolysis gas. The pyrolysis gas and the remaining particulate solid material pass through the sedimentation separation section and enter the primary gas-solid separator and the secondary gas-solid separator. Large particulate solid material is separated by the primary gas-solid separator and sent back to the fluidized bed section. Small particulate solid material enters the temperature control section through the secondary gas-solid separator. S3. Red mud powder is fed into the slag cooler through the red mud feeding structure and undergoes initial heat exchange with the reduced red mud powder. It then enters the mixed gas preheater for further heating. The red mud powder is then fed into the pre-reduction furnace to pre-reduce iron oxide with pyrolysis gas. The pre-reduced red mud powder is then fed into the reduction furnace to complete the iron oxide reduction process by countercurrent contact with high-temperature reducing gas. Solid particles are discharged from the reduction furnace and enter the slag cooler for heat exchange before being discharged to the product conveyor belt. The iron powder is separated by a magnetic separator, and the remaining minerals are sent to the brick making machine to make building materials. S4. The air blower sends cold air into the first-stage air preheater and exchanges heat with the reduction tail gas. Then it enters the second-stage air preheater to raise the temperature. The high-temperature air is mixed with steam from the waste heat boiler in the air-steam mixer and then sent to the fluidized bed section of the gasifier as a gasifying agent.

[0018] Preferably, in step S3, the red mud feeding structure feeds the red mud powder into the slag cooler via an inert gas jet.

[0019] The beneficial effects of this invention are as follows: This invention achieves integrated resource utilization of solid hazardous waste and red mud through the synergistic coupling of a raw material pretreatment unit, a pyrolysis gasification and purification unit, a gasification reduction ironmaking unit, and a waste heat comprehensive utilization unit. The segmented reaction in the gasifier and the two-stage gas-solid separation and return structure improve the sufficiency of material reaction and carbon conversion rate. The series connection of the reduction furnace and the pre-reduction furnace enables the cascade utilization of reducing gas, improving gas utilization efficiency and reducing energy consumption. Simultaneously, the red mud, after preheating by a slag cooler, participates in the reduction reaction, further enhancing the iron resource recovery rate. The waste heat comprehensive utilization unit performs multi-stage heat exchange and recovery of the tail gas and uses it for gasification agent preparation, achieving a closed-loop heat cycle and reducing system energy consumption. Overall, it constructs a multi-cycle system of gas, heat, and materials, improving system operational stability and energy utilization efficiency, and obtaining methane-rich tail gas, thus achieving efficient and synergistic resource utilization of solid hazardous waste and red mud. Attached Figure Description

[0020] Figure 1 A schematic diagram of the connection of a gasification-reduction ironmaking system for the coordinated utilization of solid waste and red mud resources. In the diagram: 1. Raw material silo; 2. Series iron separators; 3. Raw material conveyor belt; 4. Primary crusher; 5. Secondary crusher; 6. Feeding device; 7. Double spiral shaftless feeder; 8. Fluidized bed section; 9. Dry distillation section; 10. Slag temperature control section; 11. Cracking section; 12. Sedimentation and separation section; 13. Primary gas-solid separator; 14. Secondary gas-solid separator; 15. Reduction furnace; 16. Pre-reduction furnace; 17. Secondary air preheater; 18. Secondary return feeder; 19. Primary return feeder; 20. Return fan; 21. Slag cooler; 22. Magnetic separator; 23. Product belt conveyor; 24. Brick making machine; 25. Red mud powder silo; 26. Red mud powder screw feeder; 27. Pneumatic conveying fan; 28. Mixed gas preheater; 29. ​​Waste heat boiler; 30. Primary air preheater; 31. Air fan; 32. Air-steam mixer. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. All directional indicators (such as up, down, left, right, front, back, etc.) in the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indicator will also change accordingly.

[0022] like Figure 1 As shown in the figure, this embodiment provides a gasification reduction ironmaking system for the co-processing of solid and hazardous waste with red mud, including a raw material pretreatment unit, a pyrolysis gasification and purification unit, a gasification reduction ironmaking unit, and a waste heat comprehensive utilization unit. The arrows in the figure indicate the flow direction of solid materials or gases.

[0023] The raw material pretreatment unit is used for crushing and granulating solid and hazardous waste. It includes a raw material silo 1, a series of iron separators 2, a raw material conveyor belt 3, a primary crusher 4, a secondary crusher 5, a feeding device 6, and a twin-helix shaftless feeder 7. The raw material silo 1 and the primary crusher 4 are connected by the raw material conveyor belt 3. The series of iron separators 2 are suspended above the raw material conveyor belt 3. The outlet of the primary crusher 4 is connected to the inlet of the secondary crusher 5. The secondary crusher 5 is connected to the inlet of the twin-helix shaftless feeder 7 via the feeding device 6. The outlet of the twin-helix shaftless feeder 7 is connected to the middle of the gasifier. After being discharged from the raw material silo 1, the solid and hazardous waste is conveyed to the primary crusher 4 via the raw material conveyor belt 3. During the feeding process, a series of iron separators 2 remove metallic impurities from the raw materials. After being crushed by the primary crusher 4 and the secondary crusher 5, the raw materials enter the feeding device 6, which is either a feed hopper or a granulator. The materials are then conveyed to the gasifier via a double-helix shaftless feeder 7. Solid hazardous waste, transported from the raw material silo 1 via the raw material conveyor belt 3, undergoes iron impurity removal by a series of iron separators 2, and then is sequentially crushed by the primary crusher 4 and the secondary crusher 5. Finally, it is fed into the gasifier via the feeding device 6 and the double-helix shaftless feeder 7. This two-stage crushing and dispersed feeding method ensures uniform raw material particle size, reduces incomplete reactions during gasification, improves the overall carbon conversion rate, and reduces equipment wear. As an alternative, the double-helix shaftless feeder 7 can adopt a single-helix structure.

[0024] The pyrolysis gasification and purification unit is used to convert raw materials into pyrolysis gas for reducing iron oxide in red mud and removing particles and harmful impurities, providing a stable gas source for subsequent red mud reduction. The pyrolysis gasification and purification unit includes a gasifier and a gas-solid return structure. The gasifier, along its height, includes a fluidized bed section 8, a dry distillation section 9, a pyrolysis section 11, and a settling separation section 12. A slag temperature control section 10 is located on one side of the gasifier, connected to the dry distillation section 9. The top of the settling separation section 12 contracts and... The elongated, flat section facilitates rapid gas-solid separation. The lower part of the settling separation section 12 has a larger diameter and slower gas velocity, which is beneficial for the initial settling and separation of larger particles. Moving downwards, the cracking section 11 has a smaller diameter than the lower part of the settling separation section 12. The cracking section's furnace bricks have a corrugated structure and are inlaid with catalysts, which can include cracking catalysts and / or hydrogenation catalysts, promoting the final conversion of multi-carbon organic matter into methane. The slag temperature control section 10 has a double-layer water jacket structure, which facilitates the adhesion of high-temperature slag to the walls and its flow into the main furnace. Further down is the dry distillation section 9, which is also the feed section. The gasifier's feed inlet extends into the upper part of the dry distillation section 9 within the gasifier. Here, the material is rapidly and at high temperature dry distilled by the hot gas below, resulting in the rapid precipitation of organic matter. The diameter of the middle section of the dry distillation section is larger than that of the upper and lower sections. The raw material pretreatment unit is connected to the middle section of the dry distillation section, which is beneficial for the lateral distribution of gas and solids and facilitates the reaction. Next is fluidized bed section 8, which has a structure similar to a fluidized bed. It has a slag chamber at the bottom, which is conducive to slag storage. The large diameter at the bottom of fluidized bed section 8 is conducive to the water-coal gasification reaction, while the smaller diameter at the top is conducive to gas disturbance and the dry distillation reaction in the feed section.

[0025] The gas-solid return structure includes a primary gas-solid separator 13, a primary return feeder 19, a secondary gas-solid separator 14, a secondary return feeder 18, and a return fan 20. This structure separates the gas-solid mixture from the gasifier and returns the solid particles to the gasifier. Specifically, the gasifier outlet is located at the top settling and separation section 12 and connected to the inlet of the primary gas-solid separator 13. The solid feed pipe of the primary gas-solid separator 13 is connected to the fluidized bed section 8 via the primary return feeder 19. The gas outlet of the primary gas-solid separator 13 is connected to the inlet of the secondary gas-solid separator 14 via a pipe. The solid feed pipe of the secondary gas-solid separator 14 is connected to the slag temperature control section via the secondary return feeder 18. The return fan 20 is connected to the primary return device 19 and the secondary return device 18 through pipelines. The mixed gasifying agent enters the gasifier from the air distribution plate at the bottom of the fluidized bed section 8 of the gasifier through the pipeline. The mixed gasifying agent enters the fluidized bed section 8 through the air distribution plate. The raw material falls from the dry distillation section 9 and undergoes dry distillation and gasification. The gas rises and enters the primary gas-solid separator 13 after passing through the cracking section 11 and the sedimentation separation section 12. Large particles return to the fluidized bed section 8, and small particles return to the slag temperature regulation section 10 through the secondary gas-solid separator 14. The return fan 20 provides the power for return. This circulation purification method improves the carbon conversion rate and reduces emissions, achieving efficient gasification without secondary pollution.

[0026] The gasification reduction ironmaking unit utilizes the reducing gas generated during gasification to reduce iron oxide in red mud to metallic iron, achieving efficient recovery of iron resources. The unit includes a red mud feeding structure, a slag cooler 21, a pre-reduction furnace 16, and a reduction furnace 15. The red mud feeding structure includes a red mud powder silo 25, a red mud powder screw feeder 26, and a pneumatic conveying fan 27. The outlet of the red mud powder silo 25 is connected to the inlet of the red mud powder screw feeder 26. The outlet of the red mud powder screw feeder 26 is connected to the inlet pipe of the pneumatic conveying fan 27 via a pipeline. The outlet of the pneumatic conveying fan 27 is connected to the slag cooler 21. Under the jet action of the pneumatic conveying fan 27, the red mud powder is fed into the slag cooler 21. The gas inlet of the reduction furnace 15 is connected to the gas outlet of the secondary gas-solid separator 14. The gas inlet of the pre-reduction furnace 16 is connected to the gas outlet of the reduction furnace 15. The gas outlet of furnace 15 is connected to the reducing furnace 15, and the bottom slag outlet of the reducing furnace 15 is connected to the slag cooler 21. The pneumatic conveying fan 27 is connected to the slag cooler 21, the gas outlet of the secondary gas-solid separator 14 is connected to the gas inlet of the reducing furnace 15, the gas outlet of the reducing furnace 15 is connected to the gas inlet of the pre-reduction furnace 16, and the gas outlet of the pre-reduction furnace 16 is connected to the gas inlet of the secondary air preheater 17 via pipelines. The bottom slag outlet of the pre-reduction furnace 16 is connected to the raw material inlet of the reducing furnace 15. Red mud powder is conveyed from the silo to the slag cooler 21 for preheating via the red mud powder screw feeder 26 and the pneumatic conveying fan 27. Then it enters the pre-reduction furnace 16 and the reducing furnace 15 to react with the reducing gas (i.e., pyrolysis gas) fed into the secondary gas-solid separator 14. After reduction, the slag is cooled by the slag cooler 21, conveyed by the product belt conveyor 23 to the magnetic separator 22 to separate iron powder, and the remainder is sent to the brick making machine 24. This combined reduction method solves the problem of red mud utilization and realizes high-value-added resource utilization.

[0027] The waste heat comprehensive utilization unit is used to recover and utilize the high-temperature tail gas generated during the gasification and reduction process in stages, converting heat energy into preheated air and steam required for gasification, thus realizing a closed-loop energy system. The waste heat comprehensive utilization unit includes an air blower 31, a primary air preheater 30, a waste heat boiler 29, a mixed gas preheater 28, a secondary air preheater 17, and an air-steam mixer 32. The outlet of the air blower 31 is connected to the primary air preheater 30, which is connected to the waste heat boiler 29. The waste heat boiler 29 is connected to the mixed gas preheater 28, which is connected to the secondary air preheater 17. The inlet of the air-steam mixer 32 is connected to the secondary air preheater 17 and the waste heat boiler 29. The gas outlet of the gas inlet is connected to the fluidized bed section 8. The slag chamber of the fluidized bed section 8 is equipped with a water jacket, which is connected to the waste heat boiler 29 to supply water to the waste heat boiler 29. The water jacket is connected to a demineralized water input pipe. The gas outlet of the pre-reduction furnace 16 is connected to the heating gas inlet of the secondary air preheater 17. The gas outlet of the slag cooler 21 is connected to the heated gas inlet of the mixed gas preheater 28. The solid hazardous waste raw materials are crushed by the pretreatment system and sent to the pyrolysis gasification and purification system to generate pyrolysis gas. The pyrolysis gas enters the reduction furnace 15 and the pre-reduction furnace 16 of the gasification reduction ironmaking system to reduce red mud. The waste heat of the gas in the pre-reduction furnace 16 preheats the gas entering the fluidized bed section 8. The waste heat is recovered through the waste heat comprehensive utilization system to form a closed loop, realizing the efficient resource utilization of solid hazardous waste. The air fan 31 and the return fan 20 can both be oxygen generators, which can introduce air as needed and adjust the oxygen content of the gas as needed. In this system, the pipelines for material flow can be equipped with corresponding power devices and valves as needed for material flow.

[0028] Furthermore, the outlet of the secondary return feeder 18 is connected to the slag temperature control section 10. A conical outlet with an inclined axis is provided on one side of the bottom of the slag temperature control section 10, with the small end of the conical outlet inserted into the dry distillation section 9. An inlet connected to the outlet of the secondary return feeder 18 is provided on the top side of the slag temperature control section 10 away from the conical outlet. An oxygen-enriched gas input pipe is connected to the inlet of the slag temperature control section 10. This embodiment provides a gasification reduction ironmaking method for the co-utilization of solid and hazardous waste with red mud resources. Based on the system of this embodiment, it specifically includes the following steps: S1. Solid and hazardous waste is crushed and processed by the raw material pretreatment unit. Specifically, raw materials such as domestic waste, agricultural and forestry waste, medical waste, and organic hazardous waste are first sent into the raw material silo 1. The raw materials are sent to the primary crusher 4 via the raw material conveyor belt 3 for primary crushing. A series of iron removers 2 are installed above the raw material conveyor belt 3 to remove metal impurities from the material. The pre-crushed material then enters the secondary crusher 5 for further crushing. The crushed raw material is sent to the feed hopper 6. The material is sent to the dry distillation section 9 via the double spiral shaftless feeder 7. S2. The pulverized material enters the dry distillation section 9. During the material's descent, it comes into countercurrent contact with the gasifying agent from the fluidized bed section 8, resulting in a gasification reaction. As the gas and particles rise, they reach the pyrolysis section 11 of the gasifier, where large molecules are cracked and hydrogenated to generate more small-molecule pyrolysis gases. The combustible gas carries the solid particles and continues to rise. After preliminary gas-solid separation in the settling and separation section 12, it enters the primary high-efficiency separator 13. Air, conditioning nitrogen or carbon dioxide, and water spray are mixed and fed into the return fan 20 (the return fan 20 output gas contains 10-40% oxygen and 20-50% water by mass). In the primary high-efficiency separator 13, large solid particles are sent back to the fluidized bed section 8 of the gasifier via the primary return feeder 19 for further gasification reaction to improve carbon conversion rate, while the pyrolysis gas carries the small particles into the gasifier. The secondary gas-solid separator 14 further separates small solid particles, which enter the slag temperature control section 10 for combustion. Combustion-supporting oxygen (60-80% by volume) is introduced through the oxygen-enriched gas input pipe. The small solid particles are fully combusted in the slag temperature control section 10, generating high temperatures. The resulting high-temperature liquid and gas then enter the dry distillation section 9. The slag temperature control section 10 is designed with a double-layer water jacket structure to prevent overheating and burnout. The slag temperature control section 10 is connected to the middle of the dry distillation section 9. The dry distillation section is narrowed at the top and bottom and widened in the middle, allowing for a faster gas flow rate. This enables the feed material to rise from the lower part of the dry distillation section and remain at the upper part, extending the dry distillation time and ensuring more complete distillation. The dry distillation section 9 is connected to the slag temperature control section 10, facilitating higher distillation temperatures and providing sufficient heat to the system. S3. Red mud powder is fed into the pipeline from the red mud powder silo 25 through the red mud powder screw feeder 26. Inert gas (N2 or CO2) is introduced into the axial flow conveyor 27. Under the action of the air flow conveyor fan 27, the red mud powder is conveyed to the slag cooler 21 for preliminary heat exchange with the reduced red mud slag. Then it enters the mixed gas preheater 28 for further heating. The red mud powder is sent to the pre-reduction furnace 16 to pre-reduce iron oxide with pyrolysis gas (mainly CO and H2 participate in the reaction). Then the pre-reduced red mud powder is sent to the reduction furnace 15 to complete the iron oxide reduction process by countercurrent contact with high temperature reducing gas. The solid particles are discharged from the bottom of the reduction furnace 15 and enter the slag cooler 21 for heat exchange before being discharged to the product belt conveyor 23. The iron powder is separated by the magnetic separator 22 and used as raw material for steelmaking. The remaining minerals are sent to the brick making machine 24 to make building materials. S4. Air blower 31 sends cold air enriched with oxygen to primary air preheater 30 for preliminary heat exchange with reduction tail gas, and then enters secondary air preheater 17 for further temperature increase. Demineralized water is fed into the water jacket of the slag chamber at the bottom of fluidized bed section 8 for preheating, and then connected to waste heat boiler 29 to generate steam. High temperature air and steam from waste heat boiler 29 are mixed in air-steam mixer 32 and then sent into fluidized bed section 8 of gasifier as gasification agent. Excess steam from waste heat boiler 29 is sent out.

[0029] The material enters the low-temperature gasifier through the feed inlet, located at the position with the larger furnace diameter. The material flows downwards into the narrower section, where the gas flow is greater, causing the material to move up and down repeatedly. Simultaneously, it encounters hot gas rising from the lower fluidized bed section and hot gas from the adjacent upper slag temperature control section. At temperatures of 650-850℃, a rapid dry distillation reaction occurs: CH3CH2CH2CH2CH2......CH3 + 3H2 = nCH4 + mCH3CH3 The tar-like organic matter in the material is precipitated at high temperature. The precipitated solid material contains a lot of residual carbon and moves down into the fluidized bed section, where it reacts with the gasifying agent (oxygen-enriched steam that has been preheated and exchanged heat with hot slag) to produce a water-coal gasification reaction: C + O2 → CO2 + Q, C + H2O → CO + H2, C + CO2 → 2CO. The temperature is 900-1100℃. The slag moves down and exchanges heat with the gasifying agent that has just entered the fluidized bed section. After continuing to move down and exchanging heat with the demineralized water, it is discharged from the furnace body. The hot gas from the coal-water gasification reaction rises and comes into contact with the material coming down from the feed inlet, resulting in a dry distillation reaction. As the material enters the slag temperature regulation section, its temperature rises to 800-950℃. With the rising gas, it enters the cracking section, where the temperature gradually decreases. Under the action of the cracking catalyst, the tar undergoes cracking and hydrogenation reactions: CH3CH2CH2CH2CH2......CH3+H2→nCH4+nCH3CH3. Long-chain carbon chains crack multiple segments of small-molecule alkanes; catalysis accelerates the cracking process, adding hydrogen to unsaturated bonds to become saturated alkanes. Ultimately, most of these are converted into single-carbon methane: CH3CH3+H2→2CH4.

[0030] The gas from the pyrolysis section undergoes gas-solid separation and then reacts with iron oxide powder in the red mud powder in reduction furnace 15 and pre-reduction furnace 16: Fe2O3+3H2→2Fe+3H2O, 3Fe2O3+H2→2Fe3O4+H2O, Fe3O4+4H2→3Fe+4H2O, Fe2O3+3CO→2Fe+3CO2, 3Fe2O3+CO→2Fe3O4+CO2, Fe3O4+4CO→3Fe+4CO2. The tail gas is then heated by the waste heat utilization unit to obtain a gas rich in methane.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources, characterized in that, include: The raw material pretreatment unit is used for crushing and granulating solid hazardous waste. The pyrolysis gasification and purification unit includes a gasifier and a gas-solid return structure. The gasifier includes a fluidized bed section, a pyrolysis section, a cracking section and a sedimentation separation section from bottom to top along the height direction. A slag temperature regulation section is provided on one side of the gasifier and is connected to the pyrolysis section. The gas-solid return structure is used to separate the gas-solid mixture from the gasifier and send the solid particles back to the gasifier. The gasification reduction ironmaking unit includes a red mud feeding structure, a slag cooler, a pre-reduction furnace, and a reduction furnace. The red mud feeding structure is connected to the slag cooler. The gas inlet of the reduction furnace is connected to the gas outlet of the gas-solid return structure. The gas inlet of the pre-reduction furnace is connected to the gas outlet of the reduction furnace. The slag outlet of the reduction furnace is connected to the slag cooler. The red mud feeding structure is connected to the pre-reduction furnace, and the slag outlet of the pre-reduction furnace is connected to the reduction furnace. The waste heat comprehensive utilization unit includes an air blower, a primary air preheater, a waste heat boiler, a mixed gas preheater, a secondary air preheater, and an air-steam mixer. The outlet of the air blower is connected to the primary air preheater, the primary air preheater is connected to the waste heat boiler, the waste heat boiler is connected to the mixed gas preheater, the mixed gas preheater is connected to the secondary air preheater, the air-steam mixer is connected to the secondary air preheater and the waste heat boiler, the gas outlet of the pre-reduction furnace is connected to the gas inlet of the secondary air preheater, the gas outlet of the slag cooler is connected to the gas inlet of the mixed gas preheater, and the outlet of the air-steam mixer is connected to the fluidized bed section.

2. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 1, characterized in that, The raw material pretreatment unit includes a raw material silo, a series of iron separators, a raw material conveyor belt, a primary crusher, a secondary crusher, a feeding device, and a twin-helix shaftless feeder. The raw material silo and the primary crusher are connected by the raw material conveyor belt. The series of iron separators are suspended above the raw material conveyor belt. The outlet of the primary crusher and the inlet of the secondary crusher are connected. The secondary crusher and the inlet of the twin-helix shaftless feeder are connected by the feeding device. The outlet of the twin-helix shaftless feeder is connected to the middle of the gasifier. The feeding device is a feeding hopper or a granulator.

3. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 1, characterized in that, The gas-solid return structure includes a primary gas-solid separator, a primary return feeder, a secondary gas-solid separator, a secondary return feeder, and a return fan. The outlet of the gasifier is connected to the inlet of the primary gas-solid separator. The solid feed pipe of the primary gas-solid separator is connected to the fluidized bed section through the primary return feeder. The gas outlet of the primary gas-solid separator is connected to the inlet of the secondary gas-solid separator through a pipeline. The solid feed pipe of the secondary gas-solid separator is connected to the molten slag temperature control section through the secondary return feeder. The return fan is connected to the primary return feeder and the secondary return feeder through pipelines respectively. Both the air fan and the return fan are oxygen generators.

4. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 1, characterized in that, The red mud feeding structure includes a red mud powder silo, a red mud powder screw feeder, and an air conveying fan. The outlet of the red mud powder silo is connected to the inlet of the red mud powder screw feeder. The outlet of the red mud powder screw feeder is connected to the air inlet section of the air conveying fan through a pipeline. The outlet of the air conveying fan is connected to the slag cooler. The air conveying fan feeds the red mud powder into the slag cooler.

5. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 3, characterized in that, The discharge port of the secondary return feeder is connected to the slag temperature control section. A conical discharge port with an inclined axis is provided on one side of the bottom of the slag temperature control section. The small end of the conical discharge port is inserted into the dry distillation section. The top of the slag temperature control section is provided with an inlet connected to the discharge port of the secondary return feeder on the side away from the conical discharge port. The inlet of the slag temperature control section is connected to an oxygen-enriched gas input pipe. The slag temperature control section has a double-layer water jacket structure.

6. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 5, characterized in that, The top of the settling and separation section is constricted relative to the bottom. The diameter of the pyrolysis section is smaller than the diameter of the bottom of the settling and separation section. The furnace bricks of the pyrolysis section have a corrugated structure and are inlaid with catalysts. The diameter of the middle part of the dry distillation section is larger than that of the upper and lower parts. The raw material pretreatment unit is connected to the middle part of the dry distillation section. There is a slag chamber at the bottom of the fluidized bed section. The diameter of the bottom of the fluidized bed section is larger than that of the top.

7. The gasification-reduction ironmaking system for the synergistic utilization of solid and hazardous waste and red mud resources according to claim 6, characterized in that, The fluidized bed section has a water jacket at the bottom of the slag chamber, which is connected to a demineralized water input pipe. The water jacket is connected to a waste heat boiler, and the outlet of the waste heat boiler is connected to a steam delivery pipe.

8. A method for gasification-reduction ironmaking that combines solid waste and hazardous waste with red mud resource utilization, characterized in that, The gasification reduction ironmaking system based on any one of claims 1-8 for the co-processing of solid and hazardous waste with red mud resource utilization specifically includes the following steps: S1, solid and hazardous waste is crushed and treated by the raw material pretreatment unit; S2. The crushed material is fed into the gasifier for gasification. S3. The gas generated by the gasifier is fed into the gasification reduction ironmaking unit. The red mud powder is fed into the gasification reduction ironmaking unit through the red mud feeding structure. The reduction ironmaking reaction is carried out in the gasification reduction ironmaking unit. The iron is magnetically separated from the slag after the reaction. S4. The tail gas after the reduction ironmaking reaction is sent to the waste heat comprehensive utilization unit for waste heat utilization.

9. A method for gasification-reduction ironmaking involving the co-utilization of solid and hazardous waste and red mud, characterized in that, The gasification-reduction ironmaking system based on the co-processing of solid and hazardous waste with red mud resource utilization as described in claim 3 specifically includes the following steps: S1. Solid hazardous waste is crushed and processed by the raw material pretreatment unit; S2. The crushed material is fed into the dry distillation section of the gasifier. The small molecule gas and solid material produced fall and react with the gasifying agent in the fluidized bed section. The gas and particulate solid material rise to the pyrolysis section, where they are pyrolyzed to generate small molecule pyrolysis gas. The pyrolysis gas and the remaining particulate solid material pass through the sedimentation separation section and enter the primary gas-solid separator and the secondary gas-solid separator. Large particulate solid material is separated by the primary gas-solid separator and sent back to the fluidized bed section. Small particulate solid material enters the temperature control section through the secondary gas-solid separator. S3. Red mud powder is fed into the slag cooler through the red mud feeding structure and undergoes initial heat exchange with the reduced red mud powder. It then enters the mixed gas preheater for further heating. The red mud powder is then fed into the pre-reduction furnace to pre-reduce iron oxide with pyrolysis gas. The pre-reduced red mud powder is then fed into the reduction furnace to complete the iron oxide reduction process by countercurrent contact with high-temperature reducing gas. Solid particles are discharged from the reduction furnace and enter the slag cooler for heat exchange before being discharged to the product conveyor belt. The iron powder is separated by a magnetic separator, and the remaining minerals are sent to the brick making machine to make building materials. S4. The air blower sends cold air into the first-stage air preheater and exchanges heat with the reduction tail gas. Then it enters the second-stage air preheater to raise the temperature. The high-temperature air is mixed with steam from the waste heat boiler in the air-steam mixer and then sent to the fluidized bed section of the gasifier as a gasifying agent.

10. The gasification-reduction ironmaking method for the co-utilization of solid and hazardous waste with red mud according to claim 9, characterized in that, In step S3, the red mud feeding structure feeds the red mud powder into the cold slag machine through an inert gas jet.

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