Low-corrosion modification method of air-granulating slag by using slag afterheat and application thereof

Abstract

The application provides a low-corrosion modification method of air-granulated slag by using slag waste heat and application thereof, and specifically comprises the following steps: S1, forming falling slag flow by liquid slag with a temperature of 1400-1600 DEG C; S2, spraying modifier solution in a gas-liquid mixed form into the slag flow, breaking the slag flow into slag droplets, and performing primary modification by using the self waste heat of the slag droplets; S3, dropping the slag droplets after the primary modification into a slag collecting pool pre-provided with modifier solution, allowing the slag droplets to be cooled and granulated, and performing secondary modification in a self waste heat environment to obtain modified air-granulated slag. The application efficiently recycles and utilizes the waste heat of the slag, uses the waste heat as a driving force of the modification reaction, reduces external energy consumption of the modification process while improving activity, realizes energy saving and consumption reduction, significantly improves the cementitious activity of the modified air-granulated slag, and enables the modified air-granulated slag to be directly added into mineral powder as a high-activity component, which not only can effectively improve the overall activity index of the mineral powder, but also can replace part of the mineral powder with a higher price.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical slag treatment technology, and relates to a method for low-corrosion modification of air-quenched slag using residual heat of molten slag and its application. Background Technology

[0002] In the iron and steel metallurgical industry, the large-scale, high-value-added resource utilization of steel slag is a key link in achieving green and low-carbon development. Among the various steel slag treatment processes, hot quenching and drum treatment are currently the most typical technologies. Hot quenching mainly relies on spontaneous reactions under high-temperature conditions to decompose free oxides and stabilize the steel slag; drum treatment uses the synergistic effect of drum rotation and water-cooled rapid freezing to quickly crush and disintegrate the steel slag. Although both technologies can effectively improve the volume stability of steel slag, their processing cycles are relatively long, and the cementitious activity of the products is generally low. This means that their subsequent resource utilization is usually limited to low-value-added applications such as roadbed materials and landfill cover materials, resulting in limited economic and environmental benefits.

[0003] In recent years, the emergence of air quenching technology has brought new breakthroughs to the high-value utilization of steel slag. This technology utilizes high-speed airflow to instantaneously quench molten steel slag, directly producing air-quenched slag particles with controllable particle size and high glass phase content. Its cementitious activity is also significantly superior to that of products from hot quenching and drum quenching methods. However, the overall cementitious activity level of air-quenched slag still falls short of the requirements for high-performance building materials. Its 7-day cementitious activity is approximately 47%, and its 28-day cementitious activity is approximately 63%, which is still significantly lower than that of blast furnace slag, a high-quality cement admixture.

[0004] Invention patent CN108658483A discloses a method for mixing room-temperature converter steel slag with reducing agents and component adjustment materials, followed by high-temperature remelting and calcination (1455-1495°C), water quenching, separation of metallic iron, and finally grinding the secondary slag powder into an auxiliary cementitious material. The main drawback of this method is that it processes already cooled solid slag, requiring a large amount of additional energy for secondary high-temperature remelting, completely failing to utilize the enormous residual heat inherent in the molten steel slag, resulting in high production costs.

[0005] Invention patent CN104016600A discloses a method for high-temperature remodeling and upgrading of steel slag using silica-rich materials, followed by magnetic separation to extract iron. This method improves the volume stability and gelling activity of steel slag through component adjustment, showing certain positive effects. However, it also relies on secondary heating and remodeling of solid steel slag, failing to utilize the residual heat of molten slag, resulting in significant energy consumption issues.

[0006] Invention patent CN113045228A discloses a method for preparing steel slag-based alkali-activated cementitious materials. This method uses finely ground steel slag powder as the main component, and incorporates aluminum ash powder, fly ash, slag powder, silica fume, and a solid alkali activator. After mixing at room temperature, the mixture is used to formulate low-strength concrete or mine backfill materials. This technology uses room-temperature solid steel slag powder as raw material, failing to utilize the high-temperature residual heat carried by molten steel slag when it exits the furnace. It still relies on external alkali activators to react at room temperature, resulting in low energy efficiency. Secondly, the alkaline activators used, such as sodium hydroxide and sodium silicate, are still highly corrosive, requiring high-quality equipment materials. Furthermore, the resulting cementitious material has a 28-day compressive strength of only about 17 MPa, indicating low mechanical properties. Its application is limited to low-value-added fields, such as low-strength concrete and mine backfill, failing to achieve high-value resource utilization.

[0007] In summary, regarding steel slag treatment technologies, from an energy utilization perspective, most existing technologies treat the valuable residual heat of molten slag as a burden requiring energy-intensive cooling, rather than a heat source for driven chemical reactions, thus making it inherently impossible for these processes to escape the predicament of high energy consumption. From a process synergy perspective, existing technologies treat slag treatment and slag modification as separate steps, failing to embed the modification process into efficient granulation processes such as air quenching, thus missing the optimal opportunity to optimize the microstructure of slag particles using high temperatures at the moment of particle formation. From a materials chemistry perspective, to achieve modification, existing technologies typically use highly corrosive chemical activators, which not only increases equipment and environmental costs but also fails to fundamentally solve the core problem of the dense glassy structure and difficulty in activating the activity of air-quenched slag.

[0008] Therefore, although existing steel slag treatment technologies have made some progress in steel slag modification and iron recovery, their inherent technical routes mean that there are still insurmountable obstacles in realizing the high-value utilization of air-quenched slag. As a result, the air-quenched slag produced by steel plants cannot be used as a high-performance admixture due to its low cementitious activity. It can only be mixed into converter tailings and sold at low prices, resulting in extremely scarce downstream application channels and very low product added value, which seriously limits its resource value.

[0009] In view of this, developing a method for low-corrosion modification of air-quenched slag using residual heat of molten slag and its application is of great industrial application value and technical significance. Summary of the Invention

[0010] The purpose of this invention is to solve the technical problems of high energy cost and insufficient cementing activity of air-quenched slag in the prior art for steel slag modification. Specifically, it provides a method for low-corrosion modification of air-quenched slag using residual heat of molten slag and its application.

[0011] To achieve the above objectives, the present invention proposes the following technical solution: Firstly, a method for low-corrosion modification of air-quenched slag utilizing residual heat of molten slag is proposed, comprising the following steps: S1. To receive and form a downward slag flow from liquid slag at a temperature of 1400~1600℃; S2. The modifier solution is sprayed into the slag stream in a gas-liquid mixture to break it into slag droplets, and the slag droplets are modified once by their own residual heat. S3. The slag droplets after the first modification are dropped into a slag collection tank pre-filled with the modifier solution, allowing the slag droplets to cool and granulate, and then undergo a second modification under their own residual heat environment to obtain modified air-quenched slag.

[0012] Furthermore, in S1, the slag flow falls vertically under the action of gravity, and the flow velocity of the slag flow is 0.5~2.0 t / min.

[0013] Furthermore, in S2 and S3, the modifier solution is a mixture of modifier and water, the total concentration of the modifier is 15~25g / L, and the pH value of the modifier solution is 10~12; The modifier comprises a mixture of sodium carbonate and sodium sulfate, wherein the mass ratio of sodium carbonate to sodium sulfate is 1:(1~2).

[0014] Furthermore, in step S2, the modifier solution is mixed with air and then sprayed into the slag stream through a nozzle at a pressure of 0.3~0.7 MPa. The volume ratio of the modifier solution to the air is 1:(1~2).

[0015] Furthermore, the spray direction of the nozzle is spatially orthogonal to the falling direction of the slag flow; The horizontal distance between the nozzle outlet and the center of the slag flow is 0.2~1.0 m.

[0016] Furthermore, in step S3, the residual heat of the slag droplets is 200~400℃, and the reaction time for the secondary modification is 10~20 min.

[0017] Secondly, a low-corrosion modification device for air-quenched slag utilizing residual heat to implement the above method is proposed. The modification device includes a slag liquid supply unit, a liquid supply unit, a first modification unit, and a second modification unit. The slag supply unit is used to receive and guide liquid slag, including a first slag pot and a second slag pot; the first slag pot is disposed above the second slag pot, so that the liquid slag contained in the first slag pot continuously falls into the second slag pot, and the bottom of the second slag pot is provided with a slag outlet, so that the liquid slag forms a slag flow from the slag outlet and falls vertically; The liquid supply unit includes a water replenishment unit, a first liquid supply pipe, and a second liquid supply pipe. The water replenishment unit is used to mix the modifier with water to obtain a modifier solution, and its output port is connected to the input port of the first liquid supply pipe and the second liquid supply pipe, respectively. The first modification unit is located below the slag outlet and includes an air quenching zone and at least one granulator. The slag flow falls into the air quenching zone. The granulator is located in the air quenching zone and includes at least one mixing nozzle. Its spraying direction is towards the slag flow. The output port of the first liquid supply pipe is connected to the granulator, so that the mixing nozzle mixes air with the modifier solution and sprays it into the slag flow, causing it to break up into slag droplets. The second modification unit is located below the air quenching zone and includes a slag collection tank for collecting the slag droplets. The output port of the second liquid supply pipe is connected to the slag collection tank, so that the slag collection tank is pre-filled with the modifier solution and the modifier solution is replenished into the slag collection tank.

[0018] Furthermore, the first modification unit also includes an adjustment mechanism; The granulator is slidably mounted on a horizontal track via the adjustment mechanism, which drives the granulator to move along the horizontal track to adjust the horizontal distance between the nozzle and the center of the slag flow.

[0019] Thirdly, a modified air-quenched slag prepared according to the above-mentioned method of low-corrosion modification of air-quenched slag using residual heat of molten slag is proposed.

[0020] Fourthly, the application of the modified air-quenched slag as described above as an admixture in the preparation of high-performance cementitious materials is proposed, wherein the modified air-quenched slag has a specific surface area of ​​400~600 m². 2 / kg, the amount of the modified air-quenched slag in the cementitious material is 1~5 wt%.

[0021] The beneficial effects of this invention are: The present invention provides a method for low-corrosion modification of air-quenched slag using residual heat of molten slag. This method efficiently recovers and utilizes the residual heat of molten slag as the driving force for the modification reaction. While improving the activity, it reduces the external energy consumption of the entire modification process, achieving energy saving and consumption reduction. It significantly improves the gelling activity of the modified air-quenched slag, enabling it to be directly incorporated into mineral powder as a highly active component. This not only effectively improves the overall activity index of the mineral powder but also replaces some of the more expensive mineral powder, thereby greatly enhancing the added value and market competitiveness of the air-quenched slag.

[0022] On the one hand, the present invention integrates the modification process with the air-quenched granulation process, that is, the air-quenched granulation process and the chemical modification process are integrated into one. Specifically, the air-quenched granulation and the primary modification are carried out simultaneously, followed by the secondary modification. The entire process does not require external energy supply and directly uses the residual heat of the slag as the driving force for the chemical reaction, realizing the in-situ efficient utilization of energy and significantly reducing external energy consumption.

[0023] On the other hand, by optimizing the process path, this invention designs a two-stage modification process that integrates "preliminary modification in the granulation stage" and "deep modification by residual heat in the slag collection pool". This allows the modification reaction to occur simultaneously with the cooling and solidification process of the molten slag, making full use of the high temperature of the slag flow and the residual heat in the slag collection pool. This enables the modifier ions to fully penetrate and react with the glassy structure in the slag, breaking its dense structure. This maximizes the efficiency of the modifier and significantly improves the gelling activity index of the air-quenched slag, so that its 7-day and 28-day activity indices can meet the requirements for high-performance admixtures.

[0024] On the other hand, this invention uses a weakly alkaline solution of sodium carbonate and sodium sulfate in a specific mass ratio as a modifier, and controls its pH value at 10-12. That is, a low-corrosion composite salt is used to replace traditional strong corrosive activators such as NaOH and sodium silicate. While effectively activating the activity, it significantly reduces the corrosiveness of strong acid or strong base modifiers to conventional equipment, extends the service life of related equipment, reduces maintenance costs, system costs and environmental risks, and improves system durability and safety.

[0025] On the other hand, this invention uses the modified, highly active air-quenched slag powder as a key functional component, directly incorporating it into slag powder in a specific proportion for the formulation of high-performance cementitious materials. This application method pioneers a new approach to the high-value utilization of air-quenched slag, achieving partial substitution of the more expensive slag powder and improving the overall performance and economic benefits of composite cementitious materials. Specifically, the modified air-quenched slag not only has high activity itself, but also serves as a highly active component in mineral admixtures, producing a synergistic effect with slag powder, effectively improving the overall activity index of slag powder. It can replace some of the more expensive slag powder, transforming it from a low-end filler into a high-value building material raw material, greatly enhancing product added value and market competitiveness.

[0026] On the other hand, the device designed in this invention effectively avoids slag particles clogging the pipes, ensures uniform spraying of the modifier solution and stable contact with the slag flow, making the entire process continuous and controllable, suitable for large-scale industrial application; at the same time, this invention achieves high activation of air-quenched slag without introducing highly corrosive chemicals, and successfully guides it to the core raw material market in the building materials field, greatly promoting the resource utilization and high-value utilization of steel slag, which is in line with the development direction of green manufacturing and circular economy.

[0027] In summary, this invention breaks through the existing technical predicament by synergistic innovation of energy, process and materials, and provides a method for modifying wind-quenched slag that can simultaneously achieve high activity, low energy consumption and weak corrosion, laying the foundation for its large-scale and high-value resource utilization.

[0028] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Attached Figure Description

[0029] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures can be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings. The embodiments in the drawings do not constitute any limitation on the invention. Other drawings can be obtained by those skilled in the art based on the following drawings without inventive effort, wherein: Figure 1 This is a schematic diagram of the structure of the air-quenched slag low-corrosion modification device utilizing the residual heat of molten slag in an embodiment of the present invention. Figure 2 This is a schematic diagram of the process flow for the low-corrosion modification method of air-quenched slag using residual heat of molten slag in an embodiment of the present invention.

[0030] Legend: 1. First slag pot; 2. Second slag pot; 3. Liquid slag; 4. Slag outlet; 5. Slag flow; 6. Granulator; 7. Slag droplets; 8. First liquid supply pipeline; 9. Water replenishment unit; 10. Second liquid supply pipeline; 11. Perforated baffle; 12. Modified air-quenched slag; 13. Slag collection pool. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0032] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the features, wholes, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or sets thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] The fundamental reason why existing technologies for the high-value utilization of air-quenched slag have failed to achieve breakthroughs lies in a series of technical bottlenecks caused by inherent defects in the process. First, regarding energy utilization, existing modification technologies generally target solid slag at room temperature, failing to utilize the approximately 1500°C residual heat carried by molten steel slag upon leaving the plant. This necessitates external energy input and secondary heating throughout the modification process, resulting in high system energy consumption and operating costs. Second, regarding process synergy, the core objective of existing air quenching processes is rapid granulation to improve production efficiency. Subsequent modification is often an independent and additional step, causing a momentary disconnect between the modification process and the high-energy state of slag particles. This disconnect makes it difficult for the modifier to fully and efficiently interact with the air-quenched slag, becoming one of the key reasons for the insignificant improvement in its gelling activity. Third, regarding material compatibility and environmental impact, existing technologies generally rely on strongly alkaline chemical activators such as NaOH and sodium silicate to activate the slag. This inevitably leads to severe chemical corrosion of equipment, pipes, pumps, and valves made of ordinary steel, significantly increasing equipment investment and maintenance costs.

[0034] Therefore, the high-value application of air-quenched slag under the current technological background remains an unresolved industry pain point, and a new solution is urgently needed to address the series of chain problems of energy consumption, corrosion and insufficient activity.

[0035] See attached document Figure 2 As shown in the figure, this invention discloses a method for low-corrosion modification of air-quenched slag using residual heat from molten slag. The core of this method lies in integrating the modification process with the air-quenching granulation process. By introducing a modifier during the granulation and cooling stages, the residual heat of the molten slag is directly used to drive the chemical reaction. This significantly improves the gelling activity of the air-quenched slag while simultaneously reducing external energy consumption and equipment corrosion. Specifically, the method includes the following steps: S1. The liquid slag 3 with a temperature of 1400~1600℃ is received and forms a stable slag flow 5 that falls vertically under the action of gravity, and its flow rate is stably controlled within the range of 0.5~2.0 t / min. S2. Prepare a modifier solution by mixing sodium carbonate and sodium sulfate in a mass ratio of 1:(1~2) as a modifier, then mixing the modifier with water to obtain a modifier solution with a total concentration of 15~25g / L, and controlling the pH value of the modifier solution to 10~12; mix the modifier solution with air in a volume ratio of 1:(1~2) and spray it into the slag stream 5 in a gas-liquid mixture form at a pressure of 0.3~0.7 MPa to break it into slag droplets 7, and use the residual heat of the slag droplets 7 to perform a first modification; S3. The slag droplets 7 after the first modification are dropped into the slag collection tank 13 containing the pre-filled modifier solution, allowing the slag droplets 7 to cool and granulate. The slag droplets 7 still carry residual heat of 200~400℃ in the slag collection tank 13. Under this temperature environment, they undergo secondary modification with the modifier solution in the slag collection tank 13. The reaction time is 10~20 min, and modified air-quenched slag 12 is obtained.

[0036] Specifically, the modification method of this invention is based on the air-quenching granulation process. The effective implementation of the air-quenching process requires the slag to be in a high-temperature molten state to ensure its fluidity. Therefore, the temperature range of the high-temperature liquid slag 3 processed by this invention is limited to 1400~1600℃. Within this temperature range, the liquid slag 3 has suitable superheat and fluidity, enabling it to form a stable slag flow 5 and be effectively broken and granulated by the gas-liquid mixture. It also provides the necessary high-temperature driving force for subsequent chemical modification reactions.

[0037] Specifically, wind-quenched slag is a glassy substance formed by rapid cooling of high-temperature molten slag. Its dense structure makes it difficult to realize its potential activity. The aforementioned modifier uses an alkaline activator composed of sodium carbonate and sodium sulfate, in which the OH... - Ions and alkali metal ions Na + It can disrupt the glass network structure, dissolve active silicon and aluminum species, and then recombine them in the hydration environment to form hydration products with gelling properties, such as CSH gel and hydrated aluminosilicate, thereby significantly improving the mechanical properties of the material and greatly enhancing the gelling activity of modified air-quenched slag 12.

[0038] See attached document Figure 1 As shown in the figure, an embodiment of the present invention discloses a low-corrosion modification device for air-quenched slag using waste heat of molten slag to implement the above method. The device includes a slag liquid supply unit, a liquid supply unit, a first modification unit, and a second modification unit.

[0039] The slag supply unit is used to receive and guide the liquid slag 3, and includes a first slag pot 1 and a second slag pot 2. The first slag pot 1 is located above the second slag pot 2, so that the liquid slag 3 contained in the first slag pot 1 continuously falls into the second slag pot 2. The bottom of the second slag pot 2 is provided with a slag outlet 4, so that the liquid slag 3 forms a slag flow 5 from the slag outlet 4 and falls vertically.

[0040] Specifically, the first slag pot 1 is used to receive the molten slag 3 poured out from the converter, and the second slag pot 2 is used to form a slag flow 5 from the molten slag. The molten slag 3 is transported from the first slag pot 1 to above the second slag pot 2, and the first slag pot 1 is slowly tilted at an angle of 50° to 80°, so that the molten slag 3 falls continuously and stably into the second slag pot 2, and forms a falling slag flow 5 through the slag outlet 4, with a flow rate stable at 0.5 to 2.0 t / min.

[0041] In some alternative embodiments, the tilting angle of the first slag pot 1 is slowly raised to 80° by a crane control system. This angle range ensures that the molten slag 3 flows smoothly into the second slag pot 2, avoiding flow interruption or splashing. The slag outlet 4 at the bottom of the second slag pot 2 adopts a fixed diameter, which, combined with the stable tilting operation, controls the slag flow rate 5 within the process requirement range of 0.5~2 t / min.

[0042] Depending on the actual situation and needs, a device including, but not limited to, a first slag pot 1 and a second slag pot 2 may be set up, and the number of slag pots may be adjusted as needed, including increasing or decreasing.

[0043] The slag outlet 4 is a vertically extending narrow slit shape, which allows the slag flow 5 to fall vertically under the action of gravity and form a stable, flat strip, which is conducive to full contact with the subsequent modifier solution spray for primary modification and air quenching granulation.

[0044] The liquid supply unit includes a water replenishment unit 9, a first liquid supply pipe 8, and a second liquid supply pipe 10. The water replenishment unit 9 is used to mix the modifier with water to obtain a modifier solution. Its output port is connected to the input port of the first liquid supply pipe 8 and the second liquid supply pipe 10, respectively, so as to promptly introduce the modifier solution into the first and second modifier units during the operation of the device and maintain its effective concentration.

[0045] The aforementioned water replenishment unit 9 can be a water replenishment tank, with external connections to a modifier supply pipeline and a water source pipeline, which mixes a specific proportion of modifier with room temperature water in the water replenishment tank and supplies it to the operating device.

[0046] The first modification unit is located below the slag outlet 4 and includes an air quenching zone and at least one granulator 6. The slag flow 5 falls into the air quenching zone. The granulator 6 is located in the air quenching zone and includes at least one mixing nozzle. Its spray direction is towards the slag flow 5. The output port of the first liquid supply pipe 8 is connected to the granulator 6, so that the mixing nozzle mixes air with the modifier solution and sprays it into the slag flow 5, causing it to break into slag droplets 7.

[0047] Specifically, the modifier solution is delivered to the granulator 6 through the first supply pipe 8. The granulator 6 mixes the modifier solution with air at a volume ratio of 1:(1~2) and injects it into the slag stream 5 through an external mixing nozzle at a pressure of 0.3~0.7 MPa, breaking it into slag droplets 7. During this process, the slag stream 5, with a temperature of 1400~1600℃, comes into contact with the gas-liquid mixture at room temperature. After being broken and granulated, its own high-temperature residual heat is approximately 1000~1400℃. This high-temperature residual heat is used as the reaction driving force to drive the alkali-activated reaction, actively destroying the glassy structure of the slag to enhance its hydration activity, that is, driving the Na in the modifier... + SO4 2- CO3 2- The active ions react rapidly with components such as CaO, Al2O3, and SiO2 in the slag to achieve preliminary chemical activation, i.e., primary modification.

[0048] Specifically, the spray direction of the nozzle is perpendicular to the direction of gravity, so that the sprayed modifier solution comes into contact with the slag stream 5; the horizontal distance between the nozzle outlet and the center of the slag stream 5 is 0.2~1.0 m.

[0049] In some optional embodiments, to ensure sufficient mixing of the modifier solution and the slag stream 5, multiple granulators 6 are arranged in parallel according to the width of the slag stream 5 to form a spray curtain covering the entire cross-section of the slag stream 5, ensuring that the slag stream 5 can fully contact the modifier solution spray, thereby completely breaking down and granulating it and fully performing a primary modification; at the same time, the spray angle and atomization effect of the nozzle are optimized to ensure uniform spatial distribution of the gas-liquid mixture.

[0050] Specifically, when the nozzle's spray direction is perpendicular to the direction of gravity and spatially orthogonal to the falling direction of the slag flow 5, uniform crushing of the slag flow 5 can be fully achieved, slag droplet rebound and splashing can be avoided, and the equipment layout can be simplified. While maintaining the nozzle's spray direction orthogonal to the falling direction of the slag flow 5, the angle between the nozzle axis and the horizontal plane, i.e., the spray elevation angle, can be finely adjusted to optimize the interaction area and impact effect between the jet and the slag flow.

[0051] Specifically, atomizer 6 employs a two-fluid internal mixing atomizing nozzle. The nozzle uses existing commercially available products, such as the Lechler VarioJet II nozzle. Its working principle involves pre-mixing compressed air and liquid thoroughly within the mixing chamber inside the nozzle to form a uniform two-phase flow before spraying, thus achieving extremely fine and uniform atomization. Its advantages include high atomization efficiency, uniform and fine droplet size, and good anti-clogging properties, making it particularly suitable for process scenarios requiring high uniformity coverage and reaction.

[0052] In some alternative embodiments, the first modification unit further includes an adjustment mechanism. The granulator 6 is slidably mounted on a horizontal track via the adjustment mechanism, which drives the granulator 6 to move along the horizontal track to adjust the horizontal distance between the nozzle and the center of the slag flow 5. By adjusting the horizontal distance between the granulator 6 and the center of the slag flow 5 and the injection pressure of the external mixing nozzle, it is ensured that the high kinetic energy of the gas-liquid two-phase jet formed by the nozzle of the granulator 6 can stably penetrate the slag flow 5 and effectively break it up. The horizontal distance is precisely adjusted according to the state of the slag flow 5 and the air quenching effect.

[0053] Specifically, the adjusting mechanism is connected to the granulator 6 and drives the granulator 6 to move back and forth on a horizontal track. The horizontal track extends perpendicular to the falling direction of the slag flow 5 to change the horizontal distance between the injection port of the granulator 6 and the center of the slag flow 5.

[0054] The second modification unit is located below the air quenching zone and includes a slag collection tank 13 for collecting slag droplets 7. The output port of the second liquid supply pipe 10 is connected to the slag collection tank 13, so that the slag collection tank 13 is pre-filled with a modifier solution and the modifier solution is replenished into the slag collection tank 13.

[0055] Specifically, the modified slag droplets 7 fall into the slag collection tank 13 and are rapidly cooled to form modified air-quenched slag 12. The modified air-quenched slag 12 still carries residual heat of 200~400℃ in the slag collection tank 13. Under this temperature environment, the modifier solution continuously replenished through the second liquid supply pipe 10 further reacts with it to undergo a deep reaction, i.e., secondary modification, for a period of about 10~20 minutes to ensure that the modification is fully carried out.

[0056] The modified air-quenched slag 12 particles that fall into the slag collection tank 13 are homogenized through a deep reaction lasting 10 to 20 minutes under the continuous replenishment of the modifier solution in the slag collection tank 13 and the residual heat environment in the tank. The slag collection tank 13 is made of corrosion-resistant material to provide a deep modification environment for the modified air-quenched slag 12.

[0057] In some optional embodiments, a porous baffle 11 is provided at the connection between the second liquid supply pipe 10 and the slag collection tank 13. The porous baffle 11 is located at the bottom or side wall of the slag collection tank 13 and is made of a high-temperature resistant and corrosion-resistant metal material. The porous baffle 11 has a number of small holes evenly distributed on it. The hole diameter is smaller than the particle size of the modified air-quenched slag 12 to ensure effective blocking of slag particles, while allowing the modifier solution to pass through smoothly, ensuring that the modifier is in full contact with all slag particles, and finally obtaining a high-activity product with stable performance.

[0058] In some alternative embodiments, the above-mentioned apparatus further includes a steam treatment unit for treating the alkaline steam generated during the modification process. The steam treatment unit is located above the air quenching zone or further above the second slag tank 2, and includes a steam treatment chamber and an intake port connected thereto. The intake port faces the area above the air quenching zone and the slag collection tank 13 below, and several spray nozzles are provided on the top of the steam treatment chamber to wash and condense the steam using process water or a weak acidic solution to neutralize any alkaline substances that may be carried therein.

[0059] During operation, the suction inlet draws the steam generated during the secondary modification process into the steam treatment chamber. The steam is then washed, condensed, and neutralized through a spray system until it meets emission standards before being discharged. To conserve resources, the treated washing liquid can be treated with 0.1% waste acid in a wastewater treatment unit, or it can be recycled back to the water replenishment unit 9 via a circulation pipeline to mix with the modifier and form a modifier solution, which is then added to the first and second modification units. This achieves recycling and closed-loop treatment of the washing liquid, preventing environmental pollution and protecting downstream equipment.

[0060] The specific process for implementing a low-corrosion modification method for air-quenched slag using the above-mentioned apparatus and the residual heat of molten slag is as follows: (1) Slag preparation and transportation: The high-temperature liquid slag 3 generated during the steelmaking process is injected into the first slag pot 1 and slowly transported to the top of the second slag pot 2 by a crane. Then, the first slag pot 1 is slowly tilted by a hook at an angle of 50°~80°, so that the liquid slag 3 flows continuously and stably into the second slag pot 2. A stable slag flow 5 is formed through the slag outlet 4 at the bottom of the second slag pot 2, and the slag flow rate is controlled at 0.5~2 t / min.

[0061] (2) Preparation and replenishment of modifier: Sodium carbonate and sodium sulfate are mixed at a mass ratio of 1:1 to 1:2 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 15 to 25 g / L, and the pH value is adjusted to 10 to 12. During the operation of the device, the modifier solution is replenished to the system according to the evaporation and consumption to maintain its effective concentration.

[0062] (3) Granulation and preliminary modification: The modifier solution is delivered to the granulator 6 through the first supply pipe 8. The granulator 6 mixes the air and the modifier solution at a volume ratio of 1:1 to 2:1, and then sprays it onto the slag stream 5 through an external mixing nozzle at a pressure of 0.3 to 0.7 MPa, breaking it into slag droplets 7. During this process, the high-temperature residual heat of the slag droplets 7 itself serves as the driving force for the reaction and undergoes primary modification with the modifier.

[0063] (4) Deep modification: After the slag droplets 7 after the first modification fall into the slag collection tank 13, they are rapidly cooled to form modified air-quenched slag 12. The modified air-quenched slag 12 still carries residual heat of 200~400℃ in the slag collection tank 13. Under this temperature environment, the modifier continuously replenished through the second liquid supply pipe 10 further reacts with it, and the reaction time is about 10~20 min to ensure that the modification is fully carried out.

[0064] (5) Post-processing and product application: The deeply modified air-quenched slag 12 is taken out from the slag collection pool 13, dried, and then ground to a specific surface area of ​​400~600 m². 2 / kg. The obtained high-activity air-quenched slag powder can be used as a high-quality cementitious material admixture, and can be compounded with blast furnace slag powder at a ratio of 1~20 wt% to prepare high-performance cementitious materials.

[0065] Preferably, the obtained high-activity air-quenched slag powder can be used as a high-quality cementitious material admixture, and can be compounded with blast furnace slag powder at a ratio of 1~5 wt% to prepare high-performance cementitious materials.

[0066] The following detailed description, with reference to specific embodiments, further illustrates the low-corrosion modification method for air-quenched slag utilizing residual heat and its applications disclosed in this invention. Unless otherwise specified, the reagents and materials used in the examples and comparative examples are commercially available.

[0067] Example 1 A method for low-corrosion modification of air-quenched slag using residual heat of molten slag includes the following steps: (1) Preparation of modifier: Sodium carbonate and sodium sulfate were mixed at a mass ratio of 1:1.5 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 20 g / L. The pH value was measured to be approximately 11.5.

[0068] (2) Slag preparation: The high-temperature liquid slag 3 after the steelmaking process in a steel plant is injected into the first slag pot 1 and transferred to the top of the second slag pot 2. The tilt angle of the first slag pot 1 is controlled at 60° to form a stable slag flow 5 with a flow rate of about 1.2 t / min.

[0069] (3) Granulation and preliminary modification: The above-mentioned modifier solution is mixed with compressed air at a volume ratio of 1.5:1 and sprayed onto the slag stream 5 through the granulator 6 at a pressure of 0.5 MPa. The horizontal distance between the nozzle outlet of the granulator 6 and the center of the slag stream 5 is 0.6 m. The slag stream 5 is broken into fine slag droplets 7, and the preliminary modification is completed instantaneously at the high temperature of the slag droplets 7.

[0070] (4) Deep modification: The pre-modified slag droplets 7 fall into the slag collection pool 13, and the above-mentioned modifier solution is continuously replenished through the second liquid supply pipe 10, so that the modified air-quenched slag 12 undergoes deep modification in the pool for about 15 minutes.

[0071] (5) Post-processing and testing: The modified air-quenched slag 12 was taken out, dried, and then ground to a specific surface area of ​​about 420 m² / kg to obtain high-activity air-quenched slag powder.

[0072] Example 2 A method for low-corrosion modification of air-quenched slag using residual heat of molten slag includes the following steps: (1) Preparation of modifier: Sodium carbonate and sodium sulfate are mixed at a mass ratio of 1:1 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 18 g / L. The pH value was measured to be approximately 11.0.

[0073] (2) Slag preparation: The high-temperature liquid slag 3 after the steelmaking process in a steel plant is injected into the first slag pot 1 and transferred to the top of the second slag pot 2. The tilt angle of the first slag pot 1 is controlled at 70° to form a stable slag flow 5 with a flow rate of about 1.5 t / min.

[0074] (3) Granulation and preliminary modification: The above-mentioned modifier solution is mixed with compressed air at a volume ratio of 1:1 and sprayed onto the slag stream 5 through the granulator 6 at a pressure of 0.4 MPa. The horizontal distance between the nozzle outlet of the granulator 6 and the center of the slag stream 5 is 0.9 m. The slag stream 5 is broken into fine slag droplets 7, and the preliminary modification is completed instantaneously at the high temperature of the slag droplets 7.

[0075] (4) Deep modification: The pre-modified slag droplets 7 fall into the slag collection pool 13, and the above-mentioned modifier solution is continuously replenished through the second liquid supply pipe 10, so that the modified air-quenched slag 12 undergoes deep modification in the pool for about 10 minutes.

[0076] (5) Post-processing and testing: The modified air-quenched slag 12 was taken out, dried, and then ground to a specific surface area of ​​about 405 m² / kg to obtain high-activity air-quenched slag powder.

[0077] Example 3 A method for low-corrosion modification of air-quenched slag using residual heat of molten slag includes the following steps: (1) Preparation of modifier: Sodium carbonate and sodium sulfate are mixed at a mass ratio of 1:2 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 25 g / L. The pH value was measured to be approximately 12.0.

[0078] (2) Slag preparation: The high-temperature liquid slag 3 after the steelmaking process in a steel plant is injected into the first slag pot 1 and transferred to the top of the second slag pot 2. The tilt angle of the first slag pot 1 is controlled at 50° to form a stable slag flow 5 with a flow rate of about 0.8 t / min.

[0079] (3) Granulation and preliminary modification: The above-mentioned modifier solution is mixed with compressed air at a volume ratio of 2:1 and sprayed onto the slag stream 5 through the granulator 6 at a pressure of 0.6 MPa. The horizontal distance between the nozzle outlet of the granulator 6 and the center of the slag stream 5 is 0.4 m. The slag stream 5 is broken into fine slag droplets 7, and the preliminary modification is completed instantaneously at the high temperature of the slag droplets 7.

[0080] (4) Deep modification: The pre-modified slag droplets 7 fall into the slag collection pool 13, and the above-mentioned modifier solution is continuously replenished through the second liquid supply pipe 10, so that the modified air-quenched slag 12 undergoes deep modification in the pool for about 20 minutes.

[0081] (5) Post-processing and testing: The modified air-quenched slag 12 was taken out, dried, and then ground to a specific surface area of ​​about 435 m² / kg to obtain high-activity air-quenched slag powder.

[0082] Comparative Example 1 The slag from the converter of a steel plant in Example 1 was treated using a traditional air quenching process, that is, using only industrial water as the cooling medium, to obtain ordinary air-quenched slag. The specific steps are as follows: After receiving the high-temperature molten slag, it is directly transported to the air quenching device. In the air quenching zone, the molten slag is crushed and granulated using only a high-speed airflow of 0.5~0.6 MPa. No modifiers are added during the process, and no waste heat is recovered. The granulated air quenching slag particles are cooled with industrial water as the cooling medium and collected to obtain traditional air quenching slag.

[0083] The above-mentioned traditional air-quenched slag was ground under the same conditions as in Example 1 to a specific surface area of ​​about 420 m² / kg to obtain air-quenched slag powder.

[0084] The difference between Comparative Example 1 and Example 1 above is that the modification method of Example 1 was not used, but the traditional air quenching process was used.

[0085] Comparative Example 2 A method for low-corrosion modification of air-quenched slag using residual heat of molten slag includes the following steps: (1) Preparation of modifier: Sodium carbonate and sodium sulfate were mixed at a mass ratio of 1:1.5 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 20 g / L. The pH value was measured to be approximately 11.5.

[0086] (2) Slag preparation: The high-temperature liquid slag 3 after the steelmaking process in a steel plant is injected into the first slag pot 1 and transferred to the top of the second slag pot 2. The tilt angle of the first slag pot 1 is controlled at 60° to form a stable slag flow 5 with a flow rate of about 1.2 t / min.

[0087] (3) Granulation and preliminary modification: The above-mentioned modifier solution is mixed with compressed air at a volume ratio of 1.5:1 and sprayed onto the slag stream 5 at a pressure of 0.5 MPa through the granulator 6. The slag stream 5 is broken into fine slag droplets 7, and the preliminary modification is completed instantaneously at the high temperature of the slag droplets 7.

[0088] (4) Cooling and post-processing: The pre-modified slag droplets 7 fall into the slag collection tank 13, which is pre-filled with conventional industrial water as a cooling medium. After cooling, the air-quenched slag is obtained. After being taken out and dried, it is ground to a specific surface area of ​​about 420 m² / kg to obtain air-quenched slag powder.

[0089] The difference between Comparative Example 2 and Example 1 above is that the modifier solution in the slag collection tank 13 is replaced with conventional industrial water, that is, no secondary modification reaction is carried out.

[0090] Comparative Example 3 A method for low-corrosion modification of air-quenched slag using residual heat of molten slag includes the following steps: (1) Preparation of modifier: Sodium carbonate and sodium sulfate were mixed at a mass ratio of 1:1.5 and added to water replenishment unit 9 to prepare a modifier solution with a total concentration of 20 g / L. The pH value was measured to be approximately 11.5.

[0091] (2) Slag preparation: The high-temperature liquid slag 3 after the steelmaking process in a steel plant is injected into the first slag pot 1 and transferred to the top of the second slag pot 2. The tilt angle of the first slag pot 1 is controlled at 60° to form a stable slag flow 5 with a flow rate of about 1.2 t / min.

[0092] (3) Air quenching granulation: Compressed air is injected onto the slag stream 5 at a pressure of 0.5 MPa through the granulator 6, and slag particles are obtained after water quenching.

[0093] (4) Modification and post-treatment: The slag particles are heated to obtain high-temperature slag particles, which are then added to a modifier solution for modification. After cooling, air-quenched slag is obtained. After being taken out and dried, it is ground to a specific surface area of ​​about 420 m² / kg to obtain air-quenched slag powder.

[0094] The difference between Comparative Example 3 and Example 1 above is that the gas-liquid mixture injected by the granulator 6 is replaced with high-speed compressed air, that is, no modification agent solution is used for modification during the granulation stage.

[0095] Performance testing To better verify the performance of the air-quenched slag powder obtained in the above embodiments and comparative examples, the materials prepared in the above comparative examples and embodiments were subjected to performance testing.

[0096] The air-quenched slag powder products obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to gelling activity index testing. Specifically, referring to the GB / T 18046-2017 standard "Granulated blast furnace slag powder for use in cement, mortar and concrete", the gelling activity index was tested at curing ages of 7 days (i.e., 7d) and 28 days (i.e., 28d) under curing conditions of 20±1 ℃ and humidity ≥ 90%.

[0097] The specific test results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0098] Table 1. Performance test results of air-quenched slag powder obtained in the examples and comparative examples Testing items unit Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 7d activity index % 75 70 78 48 62 68 28d activity index % 96 95 98 65 84 89 As can be seen from the results in Table 1, the air-quenched slag prepared by this invention has an excellent gelling activity index, indicating that the alkaline activation reaction in this embodiment of the invention not only requires high temperature to provide initial reaction motive force, but also requires a suitable reaction time and temperature environment to allow the excitation ions to penetrate and reconstruct the glass structure. The two-step modification method, which uses the high temperature of slag flow 5 to complete the initial activation and granulation, and the residual heat of the slag in the slag collection tank 13 to carry out the deep reaction, significantly improves the gelling activity of the air-quenched slag to more than 95%, which is sufficient to be used as a key functional component in high-performance gelling materials, realizing the value leap from "low-end filler" to "high-value admixture".

[0099] As can be seen from the data of Example 1 and Comparative Example 1, the gelling activity index of the air-quenched slag prepared by the conventional method is significantly lower than that of Example 1, indicating that the high-activity modification system and method for air-quenched slag provided by the present invention can significantly improve the gelling activity of air-quenched slag, so that its activity index reaches or even exceeds the level of high-quality slag powder.

[0100] The data from Example 1 and Comparative Examples 2 and 3 show that the performance of the air-quenched slag obtained by performing only one or two modifications, i.e., by using the slag stream 5 to complete the preliminary activation and granulation at high temperature and then directly cooling with water, is significantly lower than that of Example 1. At the same time, the performance of the air-quenched slag obtained by air-quenching the slag droplets and directly modifying them is also significantly lower than that of Example 1. It is clear that the modification of either the first or second stage in the embodiments of this invention cannot effectively stimulate the potential activity of the air-quenched slag.

[0101] In summary, the two-step synergistic approach of preliminary modification and deep modification adopted in this invention has achieved groundbreaking and beneficial results. In the examples, the air-quenched slag treated by the two-step method exhibits an activity index as high as 78% after 7 days and 98% after 28 days, demonstrating a significant improvement in the activity level of the air-quenched slag. The fundamental reason for this lies in the complementary synergistic mechanism formed by the two steps: preliminary modification utilizes the high-temperature residual heat of the molten slag exceeding 1000°C to instantly destroy the dense glassy structure of the slag, creating channels for subsequent reactions; deep modification utilizes the medium-temperature residual heat of 200-400°C to provide a continuous driving force for the full diffusion of modifier ions into the slag particles and for deep chemical reactions. This gradient reaction design of high-temperature opening and medium-temperature deepening overcomes the defects of incomplete or insufficient penetration in a single-step reaction, thereby synergistically maximizing the enhancement of gelling activity.

[0102] To verify the application of the air-quenched slag obtained in the above embodiments and comparative examples as a high-quality cementitious material admixture in the formulation of high-performance cementitious materials, it was compounded with blast furnace slag powder and its performance was tested.

[0103] The air-quenched slag powder products obtained in Examples 1-3 and Comparative Examples 1-3 were compounded with S95 grade blast furnace slag powder. The cementitious activity index of the compound was tested. Specifically, referring to the GB / T 18046-2017 standard "Granulated blast furnace slag powder for use in cement, mortar and concrete", the cementitious activity index was tested after 28 days of curing under curing conditions of 20±1 ℃ and humidity ≥ 90%.

[0104] Specifically, the air-quenched slag powder product obtained in Example 1 is compounded with S95 grade blast furnace slag powder at a mass ratio of 2%, the air-quenched slag powder product obtained in Example 2 is compounded with S95 grade blast furnace slag powder at a mass ratio of 1%, and the air-quenched slag powder product obtained in Example 3 is compounded with S95 grade blast furnace slag powder at a mass ratio of 5%.

[0105] Among them, the S95 grade blast furnace slag powder is a commercially available product with a 28-day activity index ≥95% and a specific surface area of ​​420 m² / kg, meeting the requirements of GB / T 18046-2017 standard.

[0106] The compounding method is as follows: put the above materials into a V-type mixer and mix them at a speed of 30 r / min for 20 minutes to obtain the compound admixture.

[0107] The specific test results are shown in Table 2.

[0108] Table 2. Performance test results of admixtures in the examples Testing items unit Example 1 Example 2 Example 3 Composite doping amount % 2 1 5 28d activity index % 97 95 99 As shown in Table 2, the air-quenched slag prepared in this invention, when used as an admixture and compounded with slag powder, exhibits excellent gelling activity index, reaching 99% after 28 days. This performance surpasses that of single slag powder and fully meets the requirements for S95 grade slag powder. This demonstrates that the modified air-quenched slag powder prepared in Examples 1-3 of this invention achieves a complete equivalent substitution for an equal amount of high-priced slag powder. While maintaining the core performance of the product, it significantly reduces raw material costs, highlighting the high-value application potential of this invention. Furthermore, even at a relatively high substitution rate of 5%, the composite material performance is still superior to the benchmark slag powder, fully proving that the modified air-quenched slag powder prepared in this invention possesses excellent hydration activity and synergistic reinforcing ability, laying the foundation for its large-scale application.

[0109] Specifically, in the embodiments of the present invention, the modified air-quenched slag prepared under the two-stage modification process and the activation of weakly alkaline composite salt significantly destroys its dense glassy network structure, making the internal active SiO2, Al2O3 and CaO components easier to dissolve. When compounded with slag powder, these pre-activated components during the modification process can rapidly provide abundant ions and hydration product nuclei in the early stage of hydration, providing efficient induction and nucleation sites for the alkaline-activated reaction of slag powder, thereby significantly accelerating the hydration reaction kinetics of slag powder.

[0110] The gel products generated during the hydration process of both, such as C-(A)-SH gel, can interpenetrate, intertwine, and fill each other in terms of microstructure. The hydration products of modified air-quenched slag differ from those of slag hydration products in composition and structure. This complementarity promotes the formation of a denser and more uniform composite cementitious system, effectively optimizing the pore structure and improving the overall mechanical strength.

[0111] In addition, the carbonate and sulfate ions introduced into the modifier can continuously provide a mild and stable alkaline environment during subsequent hydration, which not only promotes the further depolymerization of the slag glass but also helps to stabilize the formation of hydration products.

[0112] In summary, the air-quenched slag prepared by this invention, when used as an admixture in the preparation of high-performance cementitious materials, can not only replace 1-5% of slag powder in equal amounts, but also produce a synergistic effect with slag powder, making the performance of the composite material exceed that of slag powder alone, further verifying its high activity value.

[0113] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0114] The above provides a detailed description of a method for low-corrosion modification of air-quenched slag using residual heat of molten slag, as provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for low-corrosion modification of air-quenched slag using residual heat of molten slag, characterized in that, Includes the following steps: S1. To form a falling slag flow from liquid slag at a temperature of 1400~1600℃; S2. The modifier solution is sprayed into the slag stream in a gas-liquid mixture to break it into slag droplets, and the slag droplets are modified once by their own residual heat. S3. The slag droplets after the first modification are dropped into a slag collection tank pre-filled with the modifier solution, allowing the slag droplets to cool and granulate, and then undergo a second modification under their own residual heat environment to obtain modified air-quenched slag.

2. The method for low-corrosion modification of air-quenched slag using residual heat of molten slag according to claim 1, characterized in that, In step S1, the slag flow falls vertically under the action of gravity, and the flow velocity of the slag flow is 0.5~2.0 t / min.

3. The method for low-corrosion modification of air-quenched slag utilizing residual heat of molten slag according to claim 1, characterized in that, In S2 and S3, the modifier solution is a mixture of modifier and water, the total concentration of the modifier is 15~25g / L, and the pH value of the modifier solution is 10~12. The modifier comprises a mixture of sodium carbonate and sodium sulfate, wherein the mass ratio of sodium carbonate to sodium sulfate is 1:(1~2).

4. The method for low-corrosion modification of air-quenched slag utilizing residual heat of molten slag according to claim 3, characterized in that, In step S2, the modifier solution is mixed with air and then sprayed into the slag stream through a nozzle at a pressure of 0.3~0.7 MPa. The volume ratio of the modifier solution to the air is 1:(1~2).

5. The method for low-corrosion modification of air-quenched slag using residual heat of molten slag according to claim 4, characterized in that, The spray direction of the nozzle is spatially orthogonal to the falling direction of the slag flow; The horizontal distance between the nozzle outlet and the center of the slag flow is 0.2~1.0 m.

6. The method for low-corrosion modification of air-quenched slag using residual heat of molten slag according to claim 1, characterized in that, In step S3, the residual heat of the slag droplets is 200~400℃, and the reaction time for the secondary modification is 10~20 min.

7. An apparatus for low-corrosion modification of air-quenched slag using residual heat of molten slag, for implementing the low-corrosion modification method of air-quenched slag using residual heat of molten slag as described in any one of claims 1-6, characterized in that, The modification device includes a slag-liquid supply unit, a liquid supply unit, a first modification unit, and a second modification unit; The slag supply unit is used to receive and guide liquid slag, including a first slag pot and a second slag pot; the first slag pot is disposed above the second slag pot, so that the liquid slag contained in the first slag pot continuously falls into the second slag pot, and the bottom of the second slag pot is provided with a slag outlet, so that the liquid slag forms a slag flow from the slag outlet and falls vertically; The liquid supply unit includes a water replenishment unit, a first liquid supply pipe, and a second liquid supply pipe. The water replenishment unit is used to mix the modifier with water to obtain a modifier solution, and its output port is connected to the input port of the first liquid supply pipe and the second liquid supply pipe, respectively. The first modification unit is located below the slag outlet and includes an air quenching zone and at least one granulator. The slag flow falls into the air quenching zone. The granulator is located in the air quenching zone and includes at least one mixing nozzle. Its spraying direction is towards the slag flow. The output port of the first liquid supply pipe is connected to the granulator, so that the mixing nozzle mixes air with the modifier solution and sprays it into the slag flow, causing it to break up into slag droplets. The second modification unit is located below the air quenching zone and includes a slag collection tank for collecting the slag droplets. The output port of the second liquid supply pipe is connected to the slag collection tank, so that the slag collection tank is pre-filled with the modifier solution and the modifier solution is replenished into the slag collection tank.

8. The device for low-corrosion modification of air-quenched slag utilizing waste heat of molten slag according to claim 7, characterized in that, The first modification unit also includes an adjustment mechanism; The granulator is slidably mounted on a horizontal track via the adjustment mechanism, which drives the granulator to move along the horizontal track to adjust the horizontal distance between the nozzle and the center of the slag flow.

9. A modified air-quenched slag prepared by the low-corrosion modification method of air-quenched slag using residual heat of molten slag according to any one of claims 1-6.

10. The application of the modified air-quenched slag as described in claim 9 as an admixture in the preparation of high-performance cementitious materials, characterized in that, The modified air-quenched slag has a specific surface area of ​​400~600 m². 2 / kg, the amount of the modified air-quenched slag in the cementitious material is 1~5 wt%.

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