Sintering flue gas fine dust mineralization fixation and waste heat stepwise recovery method and system

Abstract

The present application relates to the field of steel metallurgy environmental protection and energy saving technology, and particularly relates to a sintering flue gas fine dust mineralization fixation and waste heat cascade recovery method and system, comprising: extracting waste gas from 1#~5# air box of sintering machine head and introducing into a cyclone mineralization tower; the tower is divided into a cyclone acceleration zone, a mineralization reaction zone and an in-situ drying zone along the axial direction, and alkaline adjusting liquid and organic polymer binder are sprayed through a double-fluid atomizing nozzle; in a strong turbulent field of centrifugal acceleration, the fine dust is wetted, collided and formed into agglomerates; the agglomerates are in-situ dried to a water content of less than or equal to 3% by using flue gas sensible heat, and then separated through a first cyclone and a second bag dust collector, and the solid agglomerates return to a sintering batching chamber as nucleating agents, and the purified flue gas enters a waste heat boiler to recover heat energy; through the multi-field coupling design of the cyclone mineralization tower, the synergistic effect of the medicaments and the integration of the cascade waste heat recovery, efficient capture and mineralization fixation of the fine dust in the sintering flue gas, and synergistic removal of multiple pollutants are achieved.

Description

Technical Field

[0001] This invention relates to the field of environmental protection and energy conservation technology in iron and steel metallurgy, specifically to a method and system for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages. Background Technology

[0002] In the sintering process of iron and steel smelting, the 1#~5# wind box area at the head of the sintering machine is in the ignition and pre-burning stage of the sintered ore belt. The flue gas emitted in this area has the four characteristics of "high temperature, high humidity, high corrosion and high fineness": large temperature fluctuation: affected by the sintering conditions, the temperature often fluctuates drastically in the range of 200~450℃, and contains unburned residual carbon; high proportion of fine dust: since the material in this area has not been completely sintered, the dust generated is mostly unreacted raw material (such as limestone, iron ore powder) and volatile ash, of which submicron particles such as PM2.5~PM10 account for more than 30%; the shortcomings of existing dust removal technology include: (1) traditional electrostatic precipitators (ESPs) have difficulty charging fine dust of PM2.5 level, and the driving speed is low, resulting in a sharp drop in collection efficiency (usually less than 80%). A large amount of fine dust escapes downstream, which will not only wear down the booster fan, but more seriously, it will cover the surface of the desulfurization and denitrification catalyst, causing the catalyst channel to be blocked and poisoned and deactivated, greatly increasing the operation and maintenance costs; (2) The temperature of the exhaust gas at the head of the sintering machine is 200~450℃. Although the temperature is high, it is often ignored or inefficiently utilized in the entire sintering system: energy level mismatch: if it is directly used to drive the steam turbine to generate electricity, the boiler flue gas loss will be large due to the high exhaust temperature, and its heat conversion efficiency is far lower than the high-temperature section waste heat, such as the exhaust gas of the annular cooler; (3) corrosion risk: the moisture content of this exhaust gas is as high as 10%~15%, and it is rich in SO x Acidic gases such as HCl. If waste heat is directly recovered, acid dew point corrosion is very likely to occur in the low-temperature section, threatening the boiler life. Existing technologies often choose to mix this part of the waste gas into the low-temperature flue gas or bypass it directly, resulting in a huge waste of high-quality Exergy; (4) "Vicious cycle" of heavy metals and alkali metals: sintering raw materials are often accompanied by volatile elements such as lead Pb, zinc Zn, potassium K, and sodium Na. In the high-temperature zone at the head, these elements volatilize in gaseous form and condense and accumulate on the surface of fine dust due to the temperature drop during flue gas flow; The harm of traditional external circulation: the dust from conventional electrostatic precipitators at the machine head is usually returned to the sintering batch. However, these fine dusts enriched with heavy metals and alkali metals will volatilize again during secondary sintering, forming a vicious cycle of "vaporization-condensation-return-re-vaporization". This not only leads to nodules on the upper part of the blast furnace and erosion of the furnace lining, but also causes an increase in the reduction pulverization rate of sintered ore, which seriously affects the stability of blast furnace ironmaking.

[0003] Chinese patent CN200974040Y discloses a novel high-efficiency electrostatic precipitator for dust removal in the sintering machine head process. The core idea is to enhance the collection of fine dust particles by increasing the electric field, optimizing electrode configuration, and adjusting flue gas temperature. This scheme attempts to improve the collection of fine dust particles by increasing the number of electric fields or raising the voltage. However, the PM2.5 particles in the flue gas from the sintering machine head have extremely high resistivity and contain a large amount of unburned carbon, leading to severe back corona discharge. Even with increased electrostatic precipitator power, the PM2.5 collection efficiency still struggles to break through the 85% bottleneck, and it cannot handle heavy metal vapors in the flue gas, let alone recover waste heat.

[0004] Chinese patent CN103925808A discloses a system and method for efficient recovery and utilization of waste heat from sintering machine flue gas. The core of this system is to introduce high-temperature exhaust gas from the sintering machine head / main flue into a waste heat boiler for heat exchange and steam generation. This scheme directly introduces the high-temperature exhaust gas from the machine head into the waste heat boiler. However, due to the high dust concentration and strong adhesion of the flue gas (containing alkali metals and unburned carbon), a dense ash layer easily forms on the boiler heat exchange tube walls, leading to a sharp decrease in the heat transfer coefficient and even severe acid dew point corrosion. To ensure boiler safety, a large amount of cold air must be mixed in for cooling, further reducing the waste heat quality and significantly decreasing power generation efficiency. Summary of the Invention

[0005] To address the technical problems of difficult fine dust capture, low waste heat recovery rate, and easy recycling of heavy metals in existing technologies, this invention provides a method and system for mineralizing and fixing fine dust in sintering flue gas and recovering waste heat in stages. It utilizes the sensible heat of flue gas to achieve in-situ drying of agglomerates without the need for an additional heat source. The purified flue gas enters a waste heat boiler to generate 0.8 MPa saturated steam, increasing boiler steam production by ≥10% compared to conventional direct recovery. The multi-field coupling design of the cyclone mineralization tower solves the problem of difficult fine dust capture. The synergistic effect of reagents (alkaline conditioning liquid + polymer binder) achieves in-situ fixation of heavy metals and synergistic removal of multiple pollutants. Staged waste heat recovery maximizes energy utilization. These three elements work synergistically to form an integrated technical route of pollutant source capture—in-situ mineralization and fixation—energy staged recovery—solid product recycling, achieving a triple unity of low emissions, waste heat power generation / heating, reduced fuel consumption, and resource benefits.

[0006] The technical solution of this invention is as follows: In a first aspect, the present invention provides a method for mineralizing and fixing fine dust from sintering flue gas and for cascaded recovery of waste heat, comprising the following steps: Step (1), gas-solid separation and capture: sintering waste gas at a temperature of 200~450℃ is extracted from the No. 1~5 wind boxes at the head of the sintering machine. The dust concentration of the waste gas is 5~15g / Nm³, the moisture content is 10%~15%, and it contains SO2 500~1500mg / Nm³ and NO.x and alkali metal vapors; Step (2), cyclone mineralization and agglomeration: The waste gas obtained in step (1) is introduced into the cyclone mineralization tower. The cyclone mineralization tower is divided into a cyclone acceleration zone, a mineralization reaction zone and an in-situ drying zone along the axial direction. In the mineralization reaction zone, alkaline conditioning liquid and organic polymer binder are sprayed into the mineralization reaction zone through a dual-fluid atomizing nozzle. Under the combined action of the cyclone field with a centrifugal acceleration of 50~150m / s² and turbulence, the fine dust in the waste gas is wetted, collided and undergoes mineralization reaction to form spherical agglomerates with a particle size of 50~200μm. Step (3), in-situ drying: The sensible heat of the waste gas itself is used to evaporate the surface moisture of the agglomerates in the in-situ drying zone. After drying, the original wet material is transformed into dried solid agglomerates, reducing its moisture content to ≤3%. At the same time, the temperature of the waste gas is reduced to 120-180℃ and carries water vapor evaporated from the material. At this time, the dried solid particles are suspended in the cooled waste gas, forming a gas-solid mixture. Step (4), solid-gas separation and recycling: The gas-solid mixture obtained in step (3) is subjected to primary cyclone separation and secondary bag filter dust removal. The separated solid agglomerates are returned to the sintering batching room as nucleating agents. The temperature range of the purified medium and low temperature flue gas is controlled at 120℃~180℃. It enters the waste heat boiler for heat recovery. The waste heat recovery module is designed with a pressure of 1.0 MPa and generates 0.8 MPa saturated steam.

[0007] Furthermore, in step (2), the Sotter mean diameter (SMD) of the alkaline conditioning solution droplets is controlled at 30~60μm.

[0008] Furthermore, in step (2), the alkaline conditioning solution is selected from one or more of the following: lime milk with a solid content of 10% to 20%, carbide slag slurry with a solid content of 15% to 25%, or ammonia water with a mass fraction of 5% to 15%.

[0009] Furthermore, in step (2), the organic polymer binder is sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), or modified starch, with a mass fraction of 0.05% to 0.2% and an addition amount of 0.05% to 0.2% of the mass of fine dust. It forms a network polymer bridging structure on the particle surface, enhances the mechanical strength and compressive strength of the agglomerates (≥5 MPa), and prevents breakage during subsequent transportation.

[0010] Furthermore, in step (2), the parameters of the cyclone mineralization tower are configured as follows: gas velocity in the cyclone acceleration zone is 12~18m / s, residence time in the mineralization reaction zone is 3~8s, and gas velocity in the in-situ drying zone is 8~12m / s.

[0011] Furthermore, in step (4), the main components of the separated solid agglomerates are CaSO4, CaO and iron oxides, with a TFe content ≥35%, compressive strength ≥5MPa, heavy metals are encapsulated and solidified by the mineralized shell, and the leaching toxicity meets the GB5085.3 standard.

[0012] Secondly, the present invention provides a sintering flue gas fine dust mineralization fixation and waste heat cascade recovery system, comprising: waste gas from the sintering machine head air boxes 1#-5# in the gradient gas intake module is connected to a cyclone mineralization tower through gas intake pipelines made of 310S stainless steel and regulating valves; the cyclone mineralization tower is divided into three functional zones along the axial direction, namely, a cyclone acceleration zone, a mineralization reaction zone, and an in-situ drying zone along the gas intake direction; it also includes a dual-fluid atomizing nozzle connected to the mineralization reaction zone; the inlet of the dual-fluid atomizing nozzle is connected to a precision metering pump, a stirrer, and a dissolving tank in sequence through a high-pressure liquid supply pipeline; the purified flue gas outlet at the top of the cyclone mineralization tower is connected to a primary cyclone separator and a secondary bag filter in sequence through pipelines; the ash hopper outlet of the bag filter is connected to the sintering batching chamber in sequence through pipelines; and the purified gas outlet is connected to a waste heat boiler through the purified flue gas path.

[0013] Furthermore, the inner diameter of the cyclone mineralization tower is 1.5~3m, the total height is 10~18m, the thickness of the tower body insulation layer is ≥100mm, the contraction angle of the cyclone acceleration zone in the cyclone mineralization tower is 15°~25°, the mineralization reaction zone has a built-in guide cone and cyclone blades, and the diffusion angle of the in-situ drying zone is 10°~20°.

[0014] Furthermore, in the reagent preparation and spraying module, the dissolving tank has a volume of 2-5 m³, the precision metering pump has a flow accuracy of ±1%, and the atomization angle of the dual-fluid atomizing nozzle is 60°~90°.

[0015] Furthermore, the separation efficiency of the primary cyclone separator is ≥95%, and the filtration velocity of the secondary bag filter is 0.8~1.2m / min.

[0016] The beneficial effects of this invention are as follows: (1) Through the coupling effect of the strong turbulent flow field and the centrifugal field in the cyclone mineralization tower, combined with the synergistic effect of the alkaline conditioning liquid and the polymer binder, the efficient collection of fine dust is achieved, PM 10 Removal rate ≥85%, PM 2.5 With a removal rate of ≥88%, significantly higher than the collection level of traditional electrostatic precipitators (usually <80%), it effectively reduces the risk of fine particles clogging and poisoning downstream desulfurization and denitrification catalysts, and extends the catalyst life by ≥15%.

[0017] (2) The alkaline conditioning solution reacts with heavy metal ions to form stable hydroxide or sulfate minerals, which are then encapsulated in the aggregate by a network structure formed by the polymer binder, forming a dense mineralized shell. The leaching concentration of heavy metals after solidification is lower than the limit of GB50853 Hazardous Waste Identification Standard. After re-sintering, the volatility of heavy metals is reduced by more than 60%, blocking the path of their circulation and enrichment in the sintering-blast furnace system, and significantly reducing the risk of blast furnace nodules and hearth accumulation.

[0018] (3) The agglomerates are dried in situ using the sensible heat of the flue gas itself, and waste heat is recovered in stages without the need for an additional heat source: First stage: Solid agglomerates at 150-180℃ are directly returned to the sintering batching chamber, recovering 5%-8% of the sensible heat of the waste gas, replacing part of the coke powder, and reducing dye consumption; Second stage: The purified flue gas at 120℃-180℃ directly enters the waste heat boiler, generating 0.8MPa saturated steam for power generation or heating, and the boiler steam production is increased by ≥10% compared with conventional direct recovery. This avoids the problems of ash accumulation and acid dew point corrosion caused by high-temperature flue gas directly entering the waste heat boiler, and improves the stability and safety of system operation.

[0019] (4) Aggregates are returned to the sintering batching chamber as nucleating agents, which optimizes the permeability and heat conduction performance of the sintering material layer, increases the vertical sintering speed by ≥5%, increases the sintering utilization coefficient by ≥2.8%, and simultaneously improves the strength of sintered ore and the yield of finished product, thereby reducing the return rate and energy consumption.

[0020] (5) While achieving dust mineralization, the alkaline conditioning liquid neutralizes acidic gases such as SO2 and HCl in the flue gas, reducing the amount of subsequent desulfurizing agent by 10%~20%; the efficient removal of fine dust reduces the load on the desulfurization and denitrification system, extends the life of the denitrification catalyst by ≥15%, and reduces the replacement frequency and maintenance costs; the steam generated by the waste heat cascade recovery can replace part of the purchased energy, and the overall operating cost is significantly reduced.

[0021] (6) This invention integrates multiple functions such as fine dust collection, heavy metal solidification, and waste heat recovery into a single cyclone mineralization tower. It does not require additional electrostatic precipitator modification or independent waste heat boiler anti-corrosion device. The process is compact, the floor space is reduced by ≥30%, and the investment cost is reduced by ≥20% compared with the segmented treatment mode.

[0022] (7) By reducing emissions at the source and solidifying in situ, the emissions of fine particulate matter and heavy metals are significantly reduced, the pollution load of the sintering process on the surrounding environment is reduced, and the requirements of ultra-low emission standards are met, which is conducive to the realization of the enterprise's green manufacturing and carbon emission reduction goals. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of a sintering flue gas fine dust in-situ mineralization fixation and waste heat cascade recovery system.

[0025] Figure 2 This is a schematic diagram of the axial structure and partitioning of the cyclone mineralization tower in the in-situ mineralization fixation and waste heat cascade recovery system for sintering flue gas fine dust.

[0026] Figure 3 These are local SEM images of the aggregates (scale bar 5μm), showing the outline of the aggregated particles and the overall spherical protrusion morphology.

[0027] Figure 4 This is a high-magnification SEM image (scale bar 5 μm) of the aggregate surface, showing the surface microporous structure and micro / nano spherical protrusion details.

[0028] Figure 5 The image shows a cross-sectional SEM image of the aggregate (scale bar 10 μm), revealing the dense stacking of internal particles, structural transitions, and binder bridging.

[0029] Figure 6 The image is a raw dust (or a localized fracture surface) SEM image (scale bar 5 μm), showing the loose, angular morphology and pore characteristics of the particles before treatment.

[0030] In the diagram, 1-Sintering machine head air boxes 1#-5#, 2-Gas intake pipeline 310S stainless steel, 3-Swirl mineralization tower, 4-Swirl acceleration zone, 5-Mineralization reaction zone, 6-In-situ drying zone, 7-Reagent preparation and injection module, 8-Solid-gas separation module, 9-Solid agglomerate return path, 10-Purified flue gas path, 11-Sintering batching room, 12-Waste heat boiler, 13-Standardized emission, 14-Flue gas inlet, 15-Purified flue gas outlet. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0032] This invention provides a method for mineralizing and fixing fine dust from sintering flue gas and for cascaded recovery of waste heat, comprising the following steps: Step (1), gas-solid separation and capture: sintering waste gas at a temperature of 200~450℃ is extracted from the No. 1~5 wind boxes at the head of the sintering machine. The dust concentration of the waste gas is 5~15g / Nm³, the moisture content is 10%~15%, and it contains 500~1500mg / Nm³ of SO2 and NO. x and alkali metal vapors; Step (2), cyclone mineralization and agglomeration: The waste gas obtained in step (1) is introduced into the cyclone mineralization tower. The cyclone mineralization tower is divided into a cyclone acceleration zone, a mineralization reaction zone and an in-situ drying zone along the axial direction. The mineralization reaction zone is sprayed with alkaline conditioning liquid and organic polymer binder through a dual-fluid atomizing nozzle. The SMD of the alkaline conditioning liquid droplets is 30~60μm. The alkaline conditioning liquid is selected from one or more of the following: lime milk with a solid content of 10%~20%, calcium carbide slag slurry with a solid content of 15%~25%, or ammonia water with a mass fraction of 5%~15%. The organic polymer binder is sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM) or modified starch. The amount of organic polymer binder added is 0.05%~0.2% of the mass of fine dust. Under the combined action of a swirling flow field with a centrifugal acceleration of 50~150m / s² and turbulence, the fine dust in the exhaust gas is wetted, collided, and undergoes a mineralization reaction to form spherical agglomerates with a particle size of 50~200μm. The parameters of the swirling mineralization tower are configured as follows: gas velocity in the swirling acceleration zone is 12~18m / s, residence time in the mineralization reaction zone is 3~8s, and gas velocity in the in-situ drying zone is 8~12m / s.

[0033] Step (3), in-situ drying: the sensible heat of the waste gas itself is used to evaporate the moisture on the surface of the agglomeration in the in-situ drying zone, so that the moisture content is reduced to ≤3%, and the temperature of the waste gas is reduced to 120-180℃, and carries the water vapor evaporated from the material. At this time, the dried solid particles are suspended in the cooled waste gas, forming a gas-solid mixture. Step (4), solid-gas separation and recycling: The gas-solid mixture obtained in step (3) is subjected to primary cyclone separation and secondary bag filter dust removal. The separated solid agglomerates are returned to the sintering batching chamber as nucleating agents. The separated solid agglomerates are composed of CaSO4, CaO and iron oxides, with a TFe content ≥35% and a compressive strength ≥5MPa. The heavy metals are encapsulated and solidified by a mineralized shell, and the leaching toxicity meets the GB5085.3 standard. The purified medium- and low-temperature flue gas enters the waste heat boiler for heat recovery.

[0034] A system for fixing and recovering waste heat from the mineralization of fine dust in sintering flue gas includes a gradient gas intake module. The waste gas from the 1#-5# wind boxes at the head of the sintering machine is connected to a cyclone mineralization tower via a gas intake pipeline made of 310S stainless steel and a regulating valve. The cyclone mineralization tower is divided into three functional zones along the axial direction. The inner diameter of the cyclone mineralization tower is 1.5~3m, the total height is 10~18m, the thickness of the insulation layer of the tower body is ≥100mm, the contraction angle of the cyclone acceleration zone in the cyclone mineralization tower is 15°~25°, the mineralization reaction zone has a built-in guide cone and cyclone blades, and the diffusion angle of the in-situ drying zone is 10°~20°. Along the air inlet direction are, in sequence, a cyclone acceleration zone, a mineralization reaction zone, and an in-situ drying zone; it also includes a dual-fluid atomizing nozzle connected to the mineralization reaction zone. The inlet of the dual-fluid atomizing nozzle is connected in sequence to a precision metering pump, a stirrer, and a dissolving tank via a high-pressure liquid supply pipeline. The volume of the dissolving tank is 2-5 m³, the flow accuracy of the precision metering pump is ±1%, and the atomization angle of the dual-fluid atomizing nozzle is 60°~90°; the purified flue gas outlet at the top of the cyclone mineralization tower is connected in sequence to a primary cyclone separator and a secondary bag filter via pipelines. The ash hopper outlet of the bag filter is connected in sequence to the sintering batching chamber via pipelines, and the purified gas outlet is connected to the waste heat boiler via the purified flue gas path.

[0035] like Figure 1 As shown, the system draws sintering waste gas from the 1#-5# air boxes 1 at the head of the sintering machine. The waste gas enters the cyclone mineralization tower 3 through the gas intake pipeline (made of 310S stainless steel) 2. Inside the cyclone mineralization tower 3, the waste gas passes sequentially through the cyclone acceleration zone 4, the mineralization reaction zone 5, and the in-situ drying zone 6, completing the wetting, mineralization agglomeration, and in-situ drying processes of the fine dust. The reagent preparation and spraying module 7 includes a dissolving tank with a volume of 2-5 m³, a stirrer, a precision metering pump (flow accuracy ±1%), and a dual-fluid atomizing nozzle. The reagent preparation and spraying module 7 is connected to the mineralization reaction zone 5 of the cyclone mineralization tower 3 through the precision metering pump and the high-pressure liquid supply pipeline. An alkaline adjusting liquid with a pH of 8-10 and an organic polymer binder are sprayed in through the dual-fluid atomizing nozzle. In a strong turbulent flow field with a centrifugal acceleration of 50-150 m / s², Fine dust particles are wetted, collide, and form spherical agglomerates with a particle size of 50~200μm. The gas-solid mixture discharged from the purified flue gas outlet 15 at the top of the cyclone mineralization tower 3 enters the solid-gas separation module 8 through a pipeline. This module consists of a primary cyclone separator and a secondary bag filter. The generated products pass through a cascade waste heat recovery module, which is divided into a solid agglomerate return path 9 and a purified flue gas path 15. A portion of the separated solid agglomerates (150-180℃) enters the sintering batching chamber 11 through the solid agglomerate return path 9 and is recycled as a nucleating agent. Another portion of the purified flue gas (120-180℃) enters the waste heat boiler 12 through the purified flue gas path 15, generating 0.8Mpa saturated steam. After the waste heat boiler 12 recovers the heat energy, the flue gas finally meets the emission standards 13.

[0036] like Figure 2 The diagram shows the axial structure and partitioning of the cyclone mineralization tower. Along the axial direction, from bottom to top, the tower consists of a cyclone acceleration zone 4, a mineralization reaction zone 5, and an in-situ drying zone 6. The cyclone acceleration zone 4 gradually narrows from the flue gas inlet 14 (diameter D1) to the middle diameter D2, with a D2 / D1 ratio of 0.6–0.8 and a contraction angle of 15°–25°. This zone is used to increase the flue gas velocity to 12–18 m / s, creating a strong turbulent flow field to promote the initial dispersion and collision of dust particles. The mineralization reaction zone 5 connects to the cyclone acceleration zone and contains guide cones and 3–5 layers of cyclone blades. The apex angle of the guide cones is 60°–90°, and the blade inclination angle of the cyclone blades is 20°–30°, used to generate a centrifugal acceleration of 50–150°. A stable centrifugal field of m / s² extends the particle residence time to 3-8s, ensuring that the alkaline conditioning liquid and dust are in full contact and undergo a mineralization reaction. The in-situ drying zone 14 is connected above the mineralization reaction zone 13. The tower diameter gradually increases from the middle diameter D2 to the diameter D3 of the purified flue gas outlet 15. The ratio of D3 / D2 is 1.2-1.5, and the diffusion angle is 10°-20°. The gas velocity is reduced to 8-12 m / s. The sensible heat of the flue gas (from 200-450℃ to 120-180℃) evaporates the moisture on the surface of the agglomerates, achieving self-drying and solidification.

[0037] Example 1 A method for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages includes the following steps: Sintering exhaust gas at a temperature of 320±20℃ is extracted from air boxes 1 to 5 at the head of the sintering machine. The exhaust gas has a dust concentration of 8.5 g / Nm³, a moisture content of 12%, an SO2 concentration of 900 mg / Nm³, and a PM2.5 concentration of 2.8 g / Nm³. The cyclone mineralization tower has an inner diameter of 2.5m and a total height of 15m. The gas velocity in the cyclone acceleration zone is 15m / s. The residence time in the mineralization reaction zone is 5s. The gas velocity in the in-situ drying zone is 10m / s. An alkaline conditioning solution, lime slurry (15% solid content, pH 9.5), is added at a flow rate of 200L / h. The organic polymer binder is a 0.1% PAM solution at a flow rate of 50L / h. The final PM1 removal rate is 87.5%, and the PM2.5 removal rate is 88.2%. The agglomerate characteristics include D50=85μm, water content of 2.1%, TFe of 38.5%, Pb content of 0.02%, and compressive strength of 6.2 MPa. In the waste heat recovery, the boiler produces 1.2 t / h of 0.8MPa saturated steam, and the agglomerate return material saves 0.5 kg / t of coke powder in sintered ore. The sintering indicators are a 5.2% increase in vertical sintering speed and a 2.8% increase in utilization coefficient.

[0038] Example 2 Sintering exhaust gas at a temperature of 380±20℃ is extracted from air boxes 1#~5# at the head of the sintering machine. The exhaust gas has a dust concentration of 12g / Nm³, a moisture content of 14%, an SO2 concentration of 1200mg / Nm³, and a PM2.5 concentration of 2.8 g / Nm³. The cyclone mineralization tower has an inner diameter of 3m and a total height of 18m. The gas velocity in the cyclone acceleration zone is 16m / s, the residence time in the mineralization reaction zone is 6s, and the gas velocity in the in-situ drying zone is 9m / s. An alkaline conditioning liquid and an organic polymer binder are added: a calcium carbide slag slurry with a solid content of 20% and a pH of 9.0, with a flow rate of 300... L / h; the organic polymer binder was a 0.15% CMC solution with a flow rate of 80 L / h; the final PM10 removal rate was 86.8%; the PM2.5 removal rate was 88.5%; the agglomerate characteristics were D50=92μm, water content 2.3%, T.Fe=37.2%, and Pb content 0.018%; waste heat recovery included a 12% increase in boiler steam production and an 18% reduction in desulfurizing agent usage; the sintering indicators were a 6.0% increase in vertical sintering speed and a 3.2% increase in utilization coefficient.

[0039] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages, characterized in that, Includes the following steps: Step (1), Gas-solid separation and capture: Sintering waste gas at a temperature of 200~450℃ is extracted from the No. 1~5 wind boxes at the head of the sintering machine. The dust concentration of the waste gas is 5~15g / Nm³, the moisture content is 10%~15%, and it contains 500~1500mg / Nm³. 3 SO2, NO x and alkali metal vapors; Step (2), cyclone mineralization and agglomeration: The waste gas obtained in step (1) is introduced into the cyclone mineralization tower. The cyclone mineralization tower is divided into a cyclone acceleration zone, a mineralization reaction zone and an in-situ drying zone along the axial direction. In the mineralization reaction zone, alkaline conditioning liquid and organic polymer binder are sprayed into the mineralization reaction zone through a dual-fluid atomizing nozzle. Under the combined action of the cyclone field with a centrifugal acceleration of 50~150m / s² and turbulence, the fine dust in the waste gas is wetted, collided and undergoes mineralization reaction to form spherical agglomerates with a particle size of 50~200μm. Step (3), in-situ drying: the sensible heat of the waste gas itself is used to evaporate the moisture on the surface of the agglomeration in the in-situ drying zone, so that the moisture content is reduced to ≤3%, and the temperature of the waste gas is reduced to 120-180℃, and carries the water vapor evaporated from the material. At this time, the dried solid particles are suspended in the cooled waste gas, forming a gas-solid mixture. Step (4), solid-gas separation and recycling: The gas-solid mixture obtained in step (3) is subjected to primary cyclone separation and secondary bag filter dust removal. The separated solid agglomerates are returned to the sintering batching room as nucleating agents. The temperature range of the purified medium and low temperature flue gas is controlled at 120℃~180℃. It enters the waste heat boiler for heat recovery. The waste heat recovery module is designed with a pressure of 1.0 MPa and generates 0.8 MPa saturated steam.

2. The method for mineralization and fixation of fine dust from sintering flue gas and graded recovery of waste heat as described in claim 1, characterized in that, In step (2), the Sotter mean diameter (SMD) of the alkaline conditioning solution droplets is 30~60 μm.

3. The method for mineralization and fixation of fine dust from sintering flue gas and graded recovery of waste heat as described in claim 1, characterized in that, In step (2), the alkaline conditioning solution is selected from one or more of the following: lime milk with a solid content of 10% to 20%, carbide slag slurry with a solid content of 15% to 25%, or ammonia water with a mass fraction of 5% to 15%.

4. The method for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages as described in claim 1, characterized in that, In step (2), the organic polymer binder is sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), or modified starch, and the amount of organic polymer binder added is 0.05% to 0.2% of the mass of fine dust.

5. The method for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages as described in claim 1, characterized in that, In step (2), the parameters of the cyclone mineralization tower are configured as follows: gas velocity in the cyclone acceleration zone is 12~18 m / s, residence time in the mineralization reaction zone is 3~8s, and gas velocity in the in-situ drying zone is 8~12m / s.

6. The method for mineralizing and fixing fine dust from sintering flue gas and recovering waste heat in stages as described in claim 1, characterized in that, In step (4), the separated solid agglomerates consist of CaSO4, CaO and iron oxides, with a TFe content ≥35%, compressive strength ≥5MPa, heavy metals are encapsulated and solidified by the mineralized shell, and the leaching toxicity meets the GB5085.3 standard.

7. A system for use in the method according to any one of claims 1 to 6, characterized in that, In the gradient gas intake module, the exhaust gas from the 1#-5# air boxes at the head of the sintering machine is connected to the cyclone mineralization tower via gas intake pipelines made of 310S stainless steel and regulating valves. The cyclone mineralization tower is divided into three functional zones along the axial direction: the cyclone acceleration zone, the mineralization reaction zone, and the in-situ drying zone, in sequence along the air intake direction. It also includes a dual-fluid atomizing nozzle connected to the mineralization reaction zone. The inlet of the dual-fluid atomizing nozzle is connected to a precision metering pump, a stirrer, and a dissolving tank in sequence via a high-pressure liquid supply pipeline. The purified flue gas outlet at the top of the cyclone mineralization tower is connected to a primary cyclone separator and a secondary bag filter in sequence via pipelines. The ash hopper outlet of the bag filter is connected to the sintering batching chamber in sequence via pipelines. The purified gas outlet is connected to the waste heat boiler via the purified flue gas path.

8. The system as described in claim 7, characterized in that, The inner diameter of the cyclone mineralization tower is 1.5~3m, the total height is 10~18m, the thickness of the tower body insulation layer is ≥100mm, the contraction angle of the cyclone acceleration zone in the cyclone mineralization tower is 15°~25°, the mineralization reaction zone has a built-in guide cone and cyclone blades, and the diffusion angle of the in-situ drying zone is 10°~20°.

9. The system as described in claim 7, characterized in that, The dissolving tank in the reagent preparation and spraying module has a volume of 2-5 m³, the flow accuracy of the precision metering pump is ±1%, and the atomization angle of the dual-fluid atomizing nozzle is 60°~90°.

10. The system as described in claim 7, characterized in that, The separation efficiency of the primary cyclone separator is ≥95%, and the filtration velocity of the secondary bag filter is 0.8~1.2m / min.

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