A high-temperature steel slag air-powdering process

Abstract

This invention discloses a high-temperature steel slag air-crushing and granulation process, belonging to the field of comprehensive resource utilization. The process steps are as follows: Before slag discharge from steelmaking, the total oxygen content in the final steel is controlled to be ≥400 ppm, the binary basicity of the final slag is ≤4.0, and the tapping temperature is ≥1600℃. The slag is then processed using an air-crushing line to obtain granulated steel slag. The air-crushing line includes a slag feeding unit, a granulation unit, and a slag removal unit. The slag feeding unit feeds the high-temperature steel slag into the granulation unit for granulation, and the slag removal unit collects the granulated steel slag. The granulation unit includes at least one gas granulator, at least one water granulator, and a slag pool. The slag pool is filled with cooling water to receive the granulated steel slag. The gas granulator and water granulator are sequentially stacked and installed at the inlet of the slag pool. The gas granulator sprays gas onto the high-temperature steel slag, and the water granulator sprays water onto the high-temperature steel slag. This invention achieves the compatibility of high-temperature steel slag from steelmaking with the air-crushing process, improving the efficiency of air-crushing.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive resource utilization, and specifically relates to a high-temperature steel slag air granulation process. Background Technology

[0002] Steel slag is a byproduct of steelmaking, accounting for approximately 10% of steel production. The properties of steel slag, especially its high-temperature properties such as viscosity and fluidity, are related to its temperature, composition, and mineral composition. These high-temperature properties significantly influence the choice of granulation method and the granulation effect. The treatment and utilization of steel slag is not only an environmental issue but also a resource issue. The prerequisite for realizing the resource utilization of steel slag is how to achieve the cooling and granulation of high-temperature steel slag, i.e., primary treatment of the steel slag; after cooling and granulation, the high-temperature steel slag is further processed into materials for different applications for resource utilization, i.e., secondary processing and utilization of steel slag.

[0003] Currently, the main primary slag treatment technologies used by steel companies both domestically and internationally include hot quenching, drum crushing, air crushing, and hot pouring. Among these, air crushing utilizes high-speed airflow to impact and cut the liquid steel slag stream, dispersing and granulating it into fine droplets, which are then cooled into solid spherical air-crushed slag. The air-crushed slag has a fine and uniform particle size, generally less than 5 mm, and is mainly used by steel companies for recycling in sintering processes, with some used as building materials.

[0004] In actual production practice, the air-crushing process for steel slag requires high slag fluidity. However, online real-time detection and analysis of fluidity are not yet possible. During converter slag discharge, there is a lack of theoretical basis and technical support for determining whether steel slag is suitable for air-crushing, relying more on experience, which introduces many uncertainties. Often, the fluidity of the slag is judged based on experience, resulting in a low processing rate of less than 50% during air-crushing, with most steel slag requiring other treatment methods. This impacts production organization. Furthermore, because the air-crushed steel slag has a fine and uniform particle size (generally less than 5mm), steel companies use it to replace part of the flux for return to sintering, leading to the enrichment of phosphorus (P) in the molten iron.

[0005] Patent application number 200810020597.0, published on September 10, 2008, entitled "High-Temperature Liquid Steel Slag Air-Crushing and Water-Cooling Granulation Method, Apparatus, and Applications Thereof Granulated Steel Slag," describes a method for granulating liquid steel slag flowing from an tundish using a high-speed compressed air stream ejected from a granulator. The granulated slag is then suspended in a water tank for cooling. The compressed air pressure is controlled between 0.59 and 0.70 MPa, and the superheat of the liquid steel slag is controlled above 110°C. The granulation device includes a tundish, a granulator, and a water tank. Its key feature is the inclusion of a rapid heating device for the tundish near the granulator, and an automatic compressed air pressure display device connected to the compressed air pipeline. First, the invention's technical solution, which aims to control the superheat of steel slag above 110℃, cannot be effectively monitored in real-time during actual production. Superheat is the difference between the steel slag's temperature and its melting point, both of which are difficult to obtain in practice. The melting point, in particular, requires offline analysis after sampling, which takes a long time. During this period, the high-temperature steel slag temperature drops, leading to decreased fluidity. Therefore, determining whether steel slag is suitable for air crushing through superheat control is impractical and cannot guide production. Second, the invention's proposed installation of a rapid heating device in the tundish near the granulator increases processing costs and energy consumption, and also increases dust emissions. Third, the invention's use of compressed air to granulate high-temperature steel slag leads to the oxidation of metallic iron in the slag, reducing the recovery of metallic iron. Finally, the invention's proposal to directly feed granulated steel slag into concrete results in a high mud content in the aggregate.

[0006] Patent application number 202010861108.5, published on November 24, 2020, entitled "A Liquid Steel Slag Air Quenching Granulation Production Line and its Production Process," describes a process where compressed air is directly supplied through an air duct to a supersonic gas injector in the granulator. This allows for concentrated air quenching of the liquid steel slag, optimizing the processing. By adjusting the granulator before air quenching, an optimal working position is found to achieve a more ideal granulation effect for the liquid steel slag. A spray water pipe washes away some of the dust before the flue gas enters an exhaust purification tower for further filtration and purification. However, this invention only describes the operation mode of a steel slag air quenching granulation production line and does not consider whether the steel slag itself is suitable for air quenching, nor does it address the uses of the granulated steel slag.

[0007] The patent application number 202011271875.7, with a publication date of April 2, 2021, entitled "A Method for Secondary Heating of Converter Slag by Air Quenching," describes a method of secondary heating of converter slag in an alloy furnace to further liquefy the slag before air quenching. This invention primarily addresses the issue of evaluating the fluidity of slag using an alloy furnace for secondary heating. However, it has two shortcomings: firstly, it fails to address the evaluation criteria for good and poor fluidity; and secondly, the secondary heating increases energy consumption and negatively impacts slag processing efficiency.

[0008] Patent application number 202111097064.4, published on December 14, 2021, entitled "A High-Temperature Steel Slag Air Quenching Granulation Heat Recovery System," includes a heat recovery workshop, a waste heat boiler, a jaw crusher, and a rotary cooling cylinder. The heat recovery workshop includes a tilting platform, a heat recovery bed, and baffles. A supersonic nozzle is installed below the tilting platform, a high-pressure fan is installed at the bottom of the heat recovery bed, a jaw crusher is installed at the tail of the heat recovery bed, and a rotary cooling cylinder is installed downstream of the jaw crusher. Cooling water pipes are installed on the circumferential side of the outer wall of the rotary cooling cylinder, and cooling water is connected inside the cooling water pipes. This invention mainly focuses on the recovery of sensible heat from steel slag, only describing the formation of a supersonic jet through a supersonic nozzle to crush and granulate the steel slag, and heat exchange between the steel slag and cold air. It does not consider the adaptability of the steel slag properties to air granulation, the granulation effect, or the utilization of granulated steel slag.

[0009] The patent application number 202111647829.7, with an application publication date of April 12, 2022, entitled "A Steel Slag Air Quenching System and Method," describes an air quenching system comprising a steelmaking furnace, slag pots, a track, a steel slag transport vehicle, a crane, an operating room, an electrical control room, a rotating platform, a transition chute, a movable chute, and an air quenching discharge area. The steel slag transport vehicle includes two slag pots, two slag pot tilting plates, and a frame. The front end of the track leads to the steelmaking furnace, and the rear end of the track is equipped with a rotating platform. A transition chute is located at the rotating platform, and a movable chute is located below the end of the transition chute. The movable chute has a heavy slag discharge area and a tail slag discharge area on its two sides. By moving the movable chute, the steel slag at the transition chute is transported to the heavy slag discharge area or the tail slag discharge area via the movable chute. The invention mainly focuses on improving the operating efficiency of the steel slag air quenching system and reducing equipment wear, but does not consider the performance of steel slag and its adaptability to the air crushing process, nor does it consider the utilization of granulated steel slag.

[0010] Current literature on air quenching or air crushing of steel slag has the following shortcomings: First, most related literature focuses on the innovation and optimization of air crushing devices and equipment systems, rarely considering the high requirements of steel slag fluidity inherent in the air crushing process itself, and how to solve the problem of adapting steel slag properties to air crushing treatment; second, some literature mentions steel slag performance claims, but the content of these claims is difficult to apply in actual production to guide practice; third, some literature claims mention improving steel slag fluidity through heating, melting, and other technical means, which increases energy consumption and affects steel slag treatment efficiency; fourth, the particle size characteristics of granulated steel slag are not fully considered, and the utilization of granulated steel slag is not taken into account, or it is treated in a relatively crude way, such as returning it to sintering or using it for concrete, building materials, etc. Summary of the Invention

[0011] 1. The problem to be solved In response to the aforementioned problems in existing steel slag air crushing processes, this invention provides a high-temperature steel slag air crushing and granulation process. Through optimization and improvement of the steel slag air crushing and granulation process, the steel slag air crushing technology can be made more efficient, stable, safe, and environmentally friendly in practical applications.

[0012] 2. Technical Solution To solve the above problems, the present invention adopts the following technical solution.

[0013] A high-temperature steel slag air-granulation process includes the following steps: before slag discharge from steelmaking, controlling the total oxygen content (TO) in the final steel to be ≥400 ppm and the binary basicity (w) of the final slag to be... CaO / w SiO2 When the ratio (W) ≦4.0 and the tapping temperature (T) ≧1600℃ are simultaneously met, the steel slag from this furnace can be processed using the air crushing line to obtain granulated steel slag; the granulated steel slag is then graded and utilized according to different particle sizes.

[0014] Furthermore, the qualified steel slag is transported to the air crushing treatment line through slag pots for processing, and the time from the end of converter slag discharge to the start of air crushing treatment is controlled to not exceed 30 minutes.

[0015] Furthermore, the air-crushing treatment line includes a slag feeding unit, a granulation unit, and a slag removal unit. The slag feeding unit feeds high-temperature steel slag into the granulation unit for granulation, and the slag removal unit collects the granulated steel slag. The granulation unit includes at least one gas granulator, at least one water granulator, and a slag pool. Under the combined action of the gas granulator and the water granulator, the high-temperature steel slag is granulated into droplets. Specifically, the gas granulator cuts the liquid slag flow into small droplets through gas cutting, allowing them to fall evenly into the slag pool. The water granulator enhances the cooling of the droplets, accelerates their solidification, and also cools the chute. The slag pool receives the granulated steel slag and contains cooling water. The high-temperature steel slag, granulated into droplets, falls into the slag pool and is rapidly cooled into slag particles. The gas granulator and the water granulator are stacked sequentially at the inlet of the slag pool. The gas granulator sprays gas onto the high-temperature steel slag, and the water granulator sprays water onto the high-temperature steel slag.

[0016] Furthermore, the gas pressure injected by the gas atomizer is 0.5~0.75MPa to ensure that the compressed air pressure is sufficient to "cut" the liquid slag into small droplets during the slag flow, while preventing large slag pieces from falling into the water pool and causing explosions due to excessively low pressure, or slag particles from being directly sprayed onto the steel retaining wall above the slag pool due to excessively high pressure, causing the retaining wall to deform or even break. The water pressure injected by the water atomizer is 0.2~0.4MPa to ensure the cooling effect on the droplets and chute, while not affecting the air atomization effect and the distribution of slag particles.

[0017] Furthermore, the nozzle of the gas granulator is provided with two sets of vertical jet ports, one set of first horizontal jet ports, and two sets of second horizontal jet ports, all connected to compressed air. The two sets of vertical jet ports are each formed by a plurality of jet holes arranged vertically. The first and second horizontal jet ports are each formed by a plurality of jet holes arranged horizontally. The first horizontal jet port is located between the two sets of vertical jet ports, and the two sets of second horizontal jet ports are respectively arranged parallel above and below the first horizontal jet port. Preferably, the jet hole diameter of the vertical jet ports, the first horizontal jet port, and the second horizontal jet port is 4 mm. The nozzle arrangement of the gas granulator is obtained through simulation optimization. Compared with similar granulators, the main feature is the addition of two sets of second horizontal jet ports. This is mainly because the middle part is a region with high slag density; adding two sets of nozzles at the top and bottom in this region can enhance air granulation and improve the granulation effect.

[0018] Furthermore, the nozzle of the water atomizer has several spray nozzles arranged horizontally, each of which is connected to a water source; preferably, the orifice diameter of the spray nozzle of the water atomizer is 3 mm.

[0019] Furthermore, the spacing between adjacent jet holes of the second lateral jet outlet is greater than the spacing between adjacent jet holes of the first lateral jet outlet.

[0020] Furthermore, the spacing between adjacent jet holes of the second transverse jet outlet is equal to the diameter of one jet hole.

[0021] Furthermore, the slag feeding unit includes a slag pot, a tilting mechanism, and an tundish. The slag pot is rotatably connected to the tilting mechanism. The tundish is installed above the slag pool, and its side wall has a slag outlet facing the slag pool. An inclined impact plate is installed inside the tundish, with the side of the impact plate closer to the slag outlet lower than the side farther from it. Preferably, the angle of inclination of the impact plate is 45°~60°. During operation, the slag pot containing high-temperature steel slag is tilted by the tilting mechanism to pour the high-temperature steel slag into the tundish. The high-temperature steel slag hits the impact plate and flows out through the slag outlet via the impact plate's guide. After being granulated by the granulation unit, it flows into the slag pool. Preferably, when the tilting mechanism tilts, the tilting angle is controlled at 115°~125° to control the slag flow velocity at 2~4 t / min. This facilitates better granulation of the liquid slag flow and avoids problems such as solidification of the liquid steel slag in the slag pot and tundish due to excessively slow slag flow velocity, or unsatisfactory granulation effect and tundish stagnation due to excessively fast slag flow velocity.

[0022] Furthermore, the slag extraction unit includes a bucket slag extractor and a hopper. The bucket slag extractor extends into the bottom of the slag pool and includes a chain conveyor and several slag buckets connected to the chain conveyor. Each slag bucket is a container with drainage holes on its surface. The slag buckets are fed into the bottom of the slag pool via the chain conveyor, and the granulated steel slag is scooped out by the chain conveyor and finally sent to the hopper. Preferably, the operating speed of the slag buckets in the bucket slag extractor is controlled at 0.2~0.3 m / s to ensure that the steel slag is discharged from the bottom of the slag pool in a timely manner, avoiding slag accumulation at the bottom of the slag pool, which could lead to caking or even slag buildup in the slag pool.

[0023] Furthermore, the slag removal unit also includes a conveyor, located at the top of the bucket slag extractor, to transport the granulated steel slag removed from the slag pool by the bucket slag extractor to the silo for collection.

[0024] Furthermore, the air-crushing treatment line also includes a water circulation unit, which includes a sedimentation tank and a circulating water tank. The sedimentation tank is used to collect the cooling water in the slag tank. After sedimentation, the bottom of the sedimentation tank contains steel slag sediment. The cooling water above the sedimentation tank is introduced into the circulating water tank. At the same time, fresh water is introduced into the circulating water tank, and the cooling water in the circulating water tank is pumped into the slag tank to realize the water exchange of the slag tank.

[0025] Furthermore, the circulating water tank supplies water to the water granulator.

[0026] Furthermore, the air-crushing treatment line also includes a venting unit, which is located above the slag pool. The venting unit includes a blower and a chimney. The blower is used to draw gas from the surface of the slag pool and discharge it from the chimney.

[0027] Furthermore, the venting unit is also equipped with an explosion-proof device, which is a pressure relief valve, to prevent the risk of local pressure rise due to excessive gas pressure in the granulation unit. The limit of the pressure relief valve is set to 0.2 MPa, that is, when the pressure above the granulation unit is greater than 0.2 MPa, the pressure relief valve will automatically open to relieve pressure.

[0028] Furthermore, the steel slag processed by the air crushing line, i.e. the granulated steel slag in silo 33, has a particle size of ≤5mm and is screened into three types with particle sizes of 3~5mm, 1~3mm, and 0~1mm. Among them, 3~5mm is used to replace crushed stone, 1~3mm is used to replace yellow sand, and 0~1mm is used to produce steel slag powder.

[0029] 3. Beneficial effects Compared to existing technologies, the implementation effects produced by the method of this invention are as follows: (1) This invention analyzes a large amount of data from the production practice of air crushing of steel slag, studies the relationship between steel slag performance and air crushing ratio, and studies the relationship between the air crushing granulation process of this invention and key parameters such as the final tapping temperature of the converter, the total oxygen content in the steel and the binary basicity of the steel slag and steel slag performance. It conducts a large number of practical explorations on key technical parameters affecting the air crushing effect and summarizes quantitative technical indicators. For the first time, it proposes a more quantitative, efficient and operable method to solve the adaptability of steel slag performance and air crushing process; it realizes the determination of the adaptability of high-temperature steel slag in steelmaking and air crushing process, and improves the air crushing efficiency; and the granulated steel slag after air crushing granulation process of this invention has a particle size of ≤5mm, and proposes new utilization methods for steel slag with different particle size performance characteristics, realizing more scientific and efficient utilization of air crushed steel slag; (2) The air granulation process of the present invention optimizes the air granulation processing line, improves the automation level of the air granulation processing line, solves the steam emission problem and explosion prevention problem in the production process, and realizes the recycling of water in the air granulation processing line system. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the air-crushing treatment line used in the high-temperature steel slag air-crushing granulation process of the present invention; Figure 2 This is a schematic diagram of the internal structure of the intermediate tundish in the air-jet processing line of the present invention; Figure 3 This is a schematic diagram showing the arrangement of the jet holes on the nozzle of the gas granulator in the air-particle processing line of the present invention; Figure 4This is a schematic diagram showing the arrangement of the spray nozzles on the nozzles of the water granulator in the air-powdering treatment line of the present invention; Figure 5 This is a schematic diagram of the bucket slag extractor in the air crushing process line of the present invention; Figure 6 This is a schematic diagram of the slag hopper of the slag extraction machine in the air crushing processing line of the present invention; Figure 7 This is a schematic diagram of the structure of the slag hopper with screen holes on the slag extraction machine in the air crushing treatment line of the present invention; In the picture: 1. Slag Feeding Unit; 11. Slag Pot; 12. Tilting Mechanism; 13. Intermediate Ladle; 131. Slag Discharge Port; 132. Impact Plate; 2. Granulation Unit; 21. Gas Granulator; 211. Vertical Air Jet Nozzle; 212. First Horizontal Air Jet Nozzle; 213. Second Horizontal Air Jet Nozzle; 22. Water Granulator; 221. Water Spray Nozzle; 23. Slag Pool; 24. Compressed Air; 3. Slag Removal Unit; 31. Bucket Slag Extractor; 311. Chain Conveyor; 312. Slag Hopper; 3121. Connecting Ring; 32. Conveyor; 33. Silo; 4. Water Circulation Unit; 41. Sedimentation Tank; 42. Circulating Water Pool; 5. Exhaust Unit; 51. Blower; 52. Chimney; 53. Explosion-proof Device. Detailed Implementation

[0031] The present invention will now be further described with reference to specific embodiments and accompanying drawings.

[0032] The high-temperature steel slag air-granulation process of this invention comprises the following steps: before slag discharge from steelmaking, controlling the total oxygen content (TO) in the final steel to be ≥400 ppm and the binary basicity (w) of the final slag to be... CaO / w SiO2 The ratio (W) ≦4.0 and the tapping temperature (T) ≧1600℃, along with the final oxygen content TO in the steel, the final slag binary basicity W, and the tapping temperature T, are mainly based on the requirements of steelmaking to achieve the final slag form. For some steel grades, the final indicators can be directly met, while for others, oxygen blowing can be used to improve the slag's oxidizability. When all three indicators are met, the slag from that heat can be processed using an air-crushing line to obtain granulated steel slag. Granulated steel slag is then graded according to different particle sizes: sieved into three types: 3~5 mm, 1~3 mm, and 0~1 mm. The 3~5 mm granulated slag is used to replace crushed stone, the 1~3 mm granulated slag is used to replace yellow sand, and the 0~1 mm granulated slag is used to produce steel slag powder.

[0033] The high-temperature steel slag air-crushing and granulation process of this invention involves an air-crushing treatment line comprising a slag feeding unit 1, a granulation unit 2, and a slag removal unit 3. The key point is that in the granulation unit 2, gas granulators 21 and water granulators 22 are stacked sequentially to first "cut" the high-temperature steel slag flow fed from the slag feeding unit 1 into small droplets using gas cutting, and then "water spraying" to enhance droplet cooling and accelerate solidification. Before granulation, the slag feeding unit 1 uses a buffer in an tundish 13, specifically an inclined impact plate 132 within the tundish 13. This buffers the impact force of the slag flow, pre-cooling the high-temperature slag flow, and guides the high-temperature steel slag into the granulation unit 2. After processing in the granulation unit 2, the slag removal unit 3 is structurally designed to facilitate continuous slag removal and collection. Of course, the air-shredding processing line of the present invention is also provided with a water circulation unit 4 and a venting unit 5. The water circulation unit 4 realizes the replacement of cooling water in the granulation unit 2, and the venting unit 5 realizes the venting and depressurization of high-temperature steam and high-pressure gas during the granulation process of the granulation unit 2. An explosion-proof device 53 is installed to prevent gas explosion in the granulation unit 2.

[0034] The wind-blown debris treatment line in the specific implementation is the optimal solution of this invention, which is composed of... Figure 1 As shown, the air-jet crushing processing line includes a slag feeding unit 1, a granulation unit 2, a slag removal unit 3, a water circulation unit 4, and an air discharge unit 5. The slag feeding unit 1 includes a slag pot 11, a tilting mechanism 12, and an tundish 13. The slag pot 11 is rotatably connected to the tilting mechanism 12, which consists of a pair of supports. The support rods at both ends of the slag pot 11 are mounted on the supports of the tilting mechanism 12, and a pull rope is connected to the bottom of the slag pot 11. The pull rope enables the slag pot 11 to rotate on the supports and adjust the rotation angle, thereby controlling the high-temperature steel slag inside the slag pot 11 to flow out of the tundish 13 at a speed of 2~4 t / min. A slag outlet 131 is provided at the bottom of the tundish 13 near the granulation unit 2, and the slag outlet 131 is set downward, that is, towards the inlet direction of the granulation unit 2. An inclined impact plate 132 is provided inside the tundish 13, that is, the side of the impact plate 132 near the slag outlet 131 is lower than the side of the impact plate 132 away from the slag outlet 131. Preferably, the inclination angle between the impact plate 132 and the bottom of the tundish 13 is 45°~60°, which helps to buffer the slag flow velocity of high-temperature steel slag and guides the high-temperature steel slag in the tundish 13 to be discharged.

[0035] The granulation unit 2 is provided with at least a pair of gas granulators 21 and water granulators 22 stacked sequentially from top to bottom, and a slag pool 23 below the granulators: The nozzle of the gas atomizer 21 has a nozzle diameter of 4 mm and a special arrangement: it is provided with two sets of vertical jet ports 211, one set of first horizontal jet ports 212, and two sets of second horizontal jet ports 213, all connected to compressed air 24. The two sets of vertical jet ports 211 are each composed of 7 jet ports and are respectively set on both sides of the nozzle. The first horizontal jet port 212 is composed of 32 jet ports arranged horizontally on the nozzle, and the first horizontal jet port 212 is centrally located between the two sets of vertical jet ports 211. The two sets of second horizontal jet ports 213 are arranged parallel to each other and centrally located above and below the first horizontal jet port 212, that is, 5 jet ports are centrally arranged at a distance of one jet port above and below the first horizontal jet port 212, with one jet port between each jet port.

[0036] The water atomizer 22 is placed below the gas atomizer 21, and its nozzle has 32 water spray holes 221 arranged horizontally, with a diameter of 3 mm for each water spray hole 221.

[0037] The slag pool 23 contains cooling water. High-temperature steel slag, which is granulated into droplets, falls into the slag pool 23 and is rapidly cooled into slag particles with a particle size of ≤5mm.

[0038] The slag extraction unit 3 includes a bucket slag extractor 31 inserted into the bottom of the slag pool 23, a conveyor 32 for receiving the slag particles extracted by the bucket slag extractor 31, and a hopper 33 for collecting the slag particles from the conveyor 32. The bucket slag extractor 31 consists of a chain conveyor 311 and multiple slag buckets 312 connected to the chain conveyor 311. The running speed of the slag buckets 312 is controlled at 0.2~0.3 m / s. Each slag bucket 312 is equipped with a connecting ring 3121, which secures it to the chain conveyor 311. At least one surface of each slag bucket 312 has screen holes for water filtration. The conveyor 32 is located below the highest point of the bucket slag extractor 31 and is used to carry the slag particles from the slag buckets 312. The hopper 33 is located at the end of the conveyor 32 and is used to collect the slag particles transported by the conveyor 32. The chain conveyor 311 drives the slag hopper 312 into the bottom of the slag pool 23 to remove the granulated slag particles, and then transports them to the top of the chain conveyor 311. The slag particles are then poured onto the conveyor 32 and transported by the conveyor 32 to the silo 33 for collection and utilization.

[0039] The water circulation unit 4 includes a sedimentation tank 41 and a circulating water tank 42. The sedimentation tank 41 is used to receive the cooling water overflowing from the slag tank 23. After the overflowing cooling water is settled in the sedimentation tank 41, the upper part of the cooling water is fed into the circulating water tank 42. At the same time, the circulating water tank 42 is fed with fresh water. The cooling water in the circulating water tank 42 is pumped into the granulation unit 2 for use. That is, on the one hand, the water in the circulating water tank 42 is the water supply source for the water granulator 22, and on the other hand, the water in the circulating water tank 42 is pumped into the slag tank 23 to replenish fresh water, thereby realizing the circulation of cooling water.

[0040] The venting unit 5 is located above the slag pool 23. It is equipped with a blower 51 and a chimney 52. ​​The blower 51 is used to draw in steam and other gases from the granulation unit 2 and discharge them through the chimney 52. ​​An explosion-proof device 53, namely a pressure relief valve, is also provided. The pressure relief valve is set to a limit of 0.2 MPa. That is, when the pressure above the granulation unit 2 is greater than 0.2 MPa, the pressure relief valve will automatically open to relieve pressure and prevent safety hazards caused by excessive gas pressure in the granulation unit 2.

[0041] The operation mode of the above-mentioned air-crushing treatment line is as follows: High-temperature steel slag that meets the air-crushing treatment conditions is loaded into slag tank 11 and hoisted to tilting mechanism 12. Before tilting, it is confirmed that compressed air 24 is turned on, water circulation unit 4 is normal, gas granulator 21 and water granulator 22 are spraying gas and water mist normally, and the blower 51 and bucket slag extractor 31 are confirmed to be in working condition. The slag tank 11 is tilted, and the slag flows through intermediate ladle 13 into the slag pool 23. The slag flow is granulated into droplets under the action of gas granulator 21 and water granulator 22, and falls into slag pool 23 to cool rapidly into slag particles. The slag particles are picked up by bucket slag extractor 31 and then conveyed to silo 33 by conveyor 32 for later use. During the treatment process, fresh water is added to circulating water tank 42, and cooling water is added to slag pool 23 and water granulator 22 through circulating water tank 42. The overflow water from slag pool 23 enters sedimentation tank 41, and the sedimentation tank 41 overflows into circulating water tank 42 after sedimentation. When an abnormality occurs in the air crushing process line, i.e., the internal pressure of the slag pool 23 is too high, the explosion-proof device 53 will automatically open. During normal operation, steam and other gases are drawn out by the blower 51 and discharged through the chimney 52.

[0042] The following are examples and comparative examples of specific air-particle granulation processes using the aforementioned air-particle granulation line and controlling various parameters.

[0043] Example 1 At the end of the converter run, the total oxygen content in the steel was 434 ppm, the binary basicity of the final slag was W=3.5, the tapping temperature was 1657℃, the time interval from the end of slag discharge to the start of the air crushing operation was 18 minutes, the net weight of the high-temperature steel slag in the slag pot was 28t, and the above-mentioned air crushing line was used for processing. The average slag flow velocity was about 3.1 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.51~0.62MPa, the water pressure sprayed from the water granulator 22 was 0.22 MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.30 m / s. When the tilting mechanism 12 tilts at an angle of 120° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 5 tons, and 23 tons are processed, which is 82.1%. A 5 kg slag sample is taken, dried, and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 0, the percentage of 3-5 mm is 7.6%, the percentage of 1-3 mm is 36.4%, and the percentage of 0-1 mm is 56%.

[0044] Example 2 At the end of the converter run, the total oxygen content in the steel was 557 ppm, the binary basicity of the final slag was W=3.6, the tapping temperature was 1648℃, the time interval from the end of slag discharge to the start of the air crushing operation was 23 minutes, the net weight of the high-temperature steel slag in the slag pot was 30 t, and the above-mentioned air crushing line was used for processing. The average slag flow velocity was about 3.5 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.53~0.67MPa, the water pressure sprayed from the water granulator 22 was 0.26 MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.28 m / s. When the tilting mechanism 12 tilts at an angle of 115° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 3 tons, and 27 tons are processed, which is 90%. A 5kg slag sample is taken, dried, and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 0, the percentage of 3-5 mm is 5.4%, the percentage of 1-3 mm is 31.5%, and the percentage of 0-1 mm is 63.1%.

[0045] Example 3 At the converter's final stage, the total oxygen content in the steel was 543 ppm, the final slag binary basicity W=3.4, the tapping temperature was 1637℃, the time interval from the end of slag discharge to the start of the air crushing operation was 21 minutes, and the net weight of the high-temperature steel slag in the slag pot was 30 t. The above-mentioned air crushing line was used for processing, in which the average slag flow velocity was about 3.6 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.55~0.73MPa, the water pressure sprayed from the water granulator 22 was 0.28MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.30m / s. When the tilting mechanism 12 tilts at an angle of 120° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 2 tons, and 28 tons are processed, with a processing ratio of 93.3%. A 5kg slag sample is taken, dried, and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage on the 5 mm sieve is 0%, the percentage on the 3-5 mm sieve is 4.8%, the percentage on the 1-3 mm sieve is 29.7%, and the percentage on the 0-1 mm sieve is 65.5%.

[0046] Example 4 At the end of the converter run, the total oxygen content in the steel was 615 ppm, the binary basicity of the final slag was W=3.2, the tapping temperature was 1653℃, the time interval from the end of slag discharge to the start of the air crushing operation was 19 minutes, the net weight of the high-temperature steel slag in the slag pot was 29t, and the above-mentioned air crushing line was used for processing. The average slag flow velocity was about 3.6 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.55~0.65MPa, the water pressure sprayed from the water granulator 22 was 0.24 MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.30 m / s. When the tilting mechanism 12 tilts at an angle of 125° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 0 tons, and 29 tons are processed, with a processing ratio of 100%. A 5kg slag sample is taken, dried, and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage on the 5 mm sieve is 0%, the percentage on the 3-5 mm sieve is 5.3%, the percentage on the 1-3 mm sieve is 26.4%, and the percentage on the 0-1 mm sieve is 68.3%.

[0047] Comparative Example 1 At the end of the converter run, the total oxygen content in the steel is 320 ppm, the binary basicity of the final slag is W=3.6, the tapping temperature is 1624℃, the time interval from the end of slag discharge to the start of the air crushing operation is 20 minutes, the net weight of high-temperature steel slag in the slag pot is 28t, and the above-mentioned air crushing line is used for processing. The average slag flow velocity is about 2.4 t / min, the pressure of compressed air sprayed in the gas granulator 21 is 0.52~0.63MPa, the water pressure sprayed from the water granulator 22 is 0.25MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 is 0.3 m / s. When the tilting mechanism 12 tilts at an angle of 125° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 18 tons. 10 tons are processed, which is 35.7%. A 5kg slag sample is dried and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 5.9%, the percentage of 3-5 mm is 12.7%, the percentage of 1-3 mm is 35.6%, and the percentage of 0-1 mm is 45.8%.

[0048] Comparative Example 2 At the end of the converter run, the total oxygen content in the steel was 436 ppm, the binary basicity of the final slag was W=4.6, the tapping temperature was 1634℃, the time interval from the end of slag discharge to the start of the air crushing operation was 23 minutes, the net weight of the high-temperature steel slag in the slag pot was 29t, and the above-mentioned air crushing line was used for processing. The average slag flow velocity was about 2.5 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.55~0.71MPa, the water pressure sprayed from the water granulator 22 was 0.31 MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.28 m / s. When the tilting mechanism 12 tilts at an angle of 130° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 18 tons. 11 tons are processed, which is 37.9%. A 5kg slag sample is dried and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 6.2%, the percentage of 3-5 mm is 13.5%, the percentage of 1-3 mm is 32.4%, and the percentage of 0-1 mm is 47.9%.

[0049] Comparative Example 3 At the end of the converter run, the total oxygen content in the steel was 496 ppm, the binary basicity of the final slag was W=3.8, the tapping temperature was 1594℃, the time interval from the end of slag discharge to the start of the air crushing operation was 19 minutes, the net weight of high-temperature steel slag in the slag pot was 27 t, and the above-mentioned air crushing line was used for processing. The average slag flow velocity was about 2.7 t / min, the pressure of the compressed air sprayed in the gas granulator 21 was 0.54~0.70 MPa, the water pressure sprayed from the water granulator 22 was 0.30 MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 was 0.26 m / s. When the tilting mechanism 12 tilts at an angle of 120° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 19 tons. 8 tons are processed, which is 29.6%. A 5 kg slag sample is dried and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 7.6%, the percentage of slag on the 3-5 mm sieve is 14.5%, the percentage of slag on the 1-3 mm sieve is 31.2%, and the percentage of slag on the 0-1 mm sieve is 46.7%.

[0050] Comparative Example 4 At the end of the converter run, the total oxygen content in the steel is 459 ppm, the binary basicity of the final slag is W=3.7, the tapping temperature is 1640℃, the time interval from the end of slag discharge to the start of the air crushing operation is 38 minutes, the net weight of high-temperature steel slag in the slag pot is 28t, and the above-mentioned air crushing line is used for processing. The average slag flow velocity is about 2.8t / min, the pressure of compressed air sprayed in the gas granulator 21 is 0.52~0.65MPa, the water pressure sprayed from the water granulator 22 is 0.33MPa, and the running speed of the slag bucket 312 of the bucket slag extractor 31 is 0.30 m / s. When the tilting mechanism 12 tilts at an angle of 130° and the slag flow stops, the remaining steel slag in the slag pot 11 weighs 16 tons. 12 tons are processed, which is 42.9%. A 5 kg slag sample is dried and then passed through 5 mm, 3 mm, and 1 mm sieves. The percentage of slag on the 5 mm sieve is 3.4%, the percentage of slag on the 3-5 mm sieve is 8.6%, the percentage of slag on the 1-3 mm sieve is 36.8%, and the percentage of slag on the 0-1 mm sieve is 51.2%.

[0051] The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A high-temperature steel slag air-granulation process, characterized in that: The steps are as follows: Before slag discharge from the steelmaking process, control the total oxygen content in the final steel to be ≥400 ppm, the binary basicity of the final slag to be ≤4.0, and the tapping temperature to be ≥1600℃. Then, use the air crushing treatment line to process the slag to obtain granulated steel slag. The particle size of the granulated steel slag is ≤5 mm. The time from the end of converter slag discharge to the start of air crushing treatment should not exceed 30 minutes. The air crushing processing line includes a slag feeding unit (1), a granulation unit (2), and a slag removal unit (3). The slag feeding unit (1) feeds high-temperature steel slag into the granulation unit (2) for granulation, and the slag removal unit (3) collects the granulated steel slag from the granulation unit (2). The granulation unit (2) includes at least one gas granulator (21), at least one water granulator (22), and a slag pool (23). The slag pool (23) is filled with cooling water to receive the granulated steel slag. The gas granulator (21) and the water granulator (22) are stacked and installed at the feed inlet of the slag pool (23). The gas granulator (21) sprays gas onto the high-temperature steel slag, and the water granulator (22) sprays water onto the high-temperature steel slag. The gas pressure of the gas injected by the gas atomizer (21) is 0.5~0.75MPa; the water pressure of the water jet injected by the water atomizer (22) is 0.2~0.4MPa.

2. The high-temperature steel slag air-powdering process according to claim 1, characterized in that: The nozzle of the gas atomizer (21) is provided with two sets of vertical jet ports (211), one set of first horizontal jet ports (212), and two sets of second horizontal jet ports (213), all of which are connected to compressed air (24). The two sets of vertical jet ports (211) are each formed by a number of jet holes arranged vertically. The first horizontal jet port (212) and the second horizontal jet port (213) are each formed by a number of jet holes arranged horizontally. The first horizontal jet port (212) is located between the two sets of vertical jet ports (211), and the two sets of second horizontal jet ports (213) are respectively arranged parallel above and below the first horizontal jet port (212). The water atomizer (22) has several spray nozzles (221) arranged horizontally on its nozzle, and each spray nozzle (221) is connected to a water source.

3. The high-temperature steel slag air-powdering process according to claim 2, characterized in that: The spacing between adjacent jet holes of the second transverse jet hole (213) is greater than the spacing between adjacent jet holes of the first transverse jet hole (212).

4. The high-temperature steel slag air-powdering process according to claim 1, characterized in that: The slag feeding unit (1) includes a slag pot (11), a tilting mechanism (12), and an intermediate ladle (13). The slag pot (11) is rotatably connected to the tilting mechanism (12). The intermediate ladle (13) is installed above the slag pool (23). The side wall of the intermediate ladle (13) is provided with a slag outlet (131) facing the slag pool (23). An inclined impact plate (132) is provided inside the intermediate ladle (13). The side of the impact plate (132) near the slag outlet (131) is lower than the side away from the slag outlet (131). During operation, the slag pot (11) containing high-temperature steel slag is rotated by the tilting mechanism (12) to pour the high-temperature steel slag into the intermediate ladle (13). The high-temperature steel slag hits the impact plate (132) and flows out from the slag outlet (131) through the drainage of the impact plate (132). After being granulated by the granulation unit (2), it flows into the slag pool (23).

5. The high-temperature steel slag air-powdering process according to claim 1, characterized in that: The slag removal unit (3) includes a bucket slag extractor (31) and a silo (33). The bucket slag extractor (31) extends into the bottom of the slag pool (23) and includes a chain conveyor (311) and several slag buckets (312) connected to the chain conveyor (311). The slag buckets (312) are containers with drainage holes on the surface. The slag buckets (312) are sent to the bottom of the slag pool (23) by the chain conveyor (311) and the granulated steel slag is scooped out under the drive of the chain conveyor (311) and finally sent into the silo (33).

6. A high-temperature steel slag air-granulation process according to any one of claims 2 to 5, characterized in that: The air-crushing treatment line also includes a water circulation unit (4), which includes a sedimentation tank (41) and a circulating water tank (42). The sedimentation tank (41) is used to hold the cooling water in the slag tank (23). After sedimentation, the bottom of the sedimentation tank (41) is steel slag sediment. The cooling water above the sedimentation tank (41) is introduced into the circulating water tank (42). At the same time, fresh water is introduced into the circulating water tank (42), and the cooling water in the circulating water tank (42) is pumped into the slag tank (23) to realize the water exchange of the slag tank (23).

7. The high-temperature steel slag air-powdering process according to claim 6, characterized in that: The air crushing process line also includes a venting unit (5), which is located above the slag pool (23). The venting unit (5) includes a blower (51) and a chimney (52). The blower (51) is used to draw gas from the liquid surface of the slag pool (23) and discharge it from the chimney (52).

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