Method for reducing tapping hole roughing slag in converter tapping process

Abstract

The invention discloses a method for reducing tapping hole roughing slag in the converter tapping process, and belongs to the technical field of metallurgy. In order to solve the problem that in the converter tapping process, molten steel vortex slag entrapment in the later period and tapping hole gushing slag at the tapping end point fall into a steel ladle, water flow is intermittently jetted before molten steel vortex slag entrapment begins to occur and water flow is continuously jetted at the moment that molten steel is completely discharged and the slag begins to be intensively jetted out from an outlet of a tapping hole from the outside of the converter; the method comprises the following steps of: (1) weakening the vortex intensity of a molten steel surface in a furnace by intermittently destroying a steel flow state in a tapping hole in a tapping process so as to reduce vortex slag entrapment; and (2) reversely driving back furnace slag flowing into the tapping hole from the furnace at a tapping end point and continuously preventing the furnace slag in the furnace from flowing into the tapping hole again by utilizing a water vapor body generated by flash evaporation of heated water and explosion kinetic energy of the water vapor body. The total amount of slag falling from the tapping hole in the tapping process and at the end point can be more conveniently, economically and effectively inhibited by the same water jet system device.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and more specifically, to a method for suppressing the large amount of slag flowing out of the tapping port at the end of the converter tapping process. Background Technology

[0002] The converter steelmaking process is a ferrite purification process in which impurities in molten iron are slagred or gasified in a strong oxidizing atmosphere. The slag at the end of the blowing process is enriched with various harmful compounds. Any slag that enters the ladle with the molten steel during tapping will contaminate the molten steel and have various negative effects on the subsequent deoxidation and refining processes. There are three main possible stages in the process of slag entering the ladle from the tapping spout during the converter tapping process: 1) the floating slag (front slag) flowing out before the molten steel flows out of the tapping spout when the furnace body is tilted; 2) the floating slag (hereinafter referred to as process slag) that is drawn in by the vortex of molten steel above the tapping spout during the middle and late stages of tapping; and 3) the slag that flows directly out of the tapping spout after the molten steel has been completely discharged at the end of tapping (hereinafter referred to as rear slag). The existing method of using a refractory material inverted cone / inverted frustum slag blocking device in the furnace can suppress the problem of process slag in the later stages of tapping to a certain extent, but it cannot reduce the slag entrainment by the molten steel vortex during the middle and even later stages of tapping, and the suppression effect on rear slag is not ideal. The existing method of using a refractory material inverted cone / inverted frustum slag blocking device in the furnace to control process slag, combined with a tapping spout sliding plate device or a tapping spout gas backflushing device to block rear slag, can better suppress the problem of slag entering the ladle, but each method has its own specific defects and shortcomings.

[0003] The technical method of using an inverted cone / truncated cone slag-blocking device made of refractory material thrown into the furnace involves designing the device's quasi-density between that of molten steel and slag. After being inserted into the furnace during the mid-to-late stages of tapping, its guide rod is inserted into the taphole. The inverted cone / truncated cone, which specifically performs the slag-blocking function, remains positioned between the molten steel and slag interface. Only in the later stages of tapping, when the inverted cone / truncated cone approaches the taphole inlet, can it suppress slag entrapment by the eddy currents on the molten steel surface to a certain extent. It can only fall into the taphole to prevent slag from falling into the ladle when the molten steel is almost completely tapped. Therefore, in principle... The timing of its slag-blocking effect is passive. The nearly smooth refractory cone / frustum with only a few shallow grooves on the side, which is suspended high above between the molten steel and slag, cannot avoid the slag vortex generated around it. It cannot enter the core of the slag vortex to interfere with the slag entrainment of the molten steel. Furthermore, it cannot effectively block the slag at the end of the tapping when there are irregularities at the tapping outlet. These problems are the reason why it is necessary to use a combination of pneumatic slag-blocking method or sliding plate slag-blocking method that can only control the slag behind the tapping outlet for dual slag blocking during tapping.

[0004] The pneumatic slag blocking method is a technology developed in the 1980s to solve the problem of slag overflow at the end of the converter tapping process. Its core principle is "pneumatic interference + momentum transfer". That is, when the molten steel is completely discharged at the end of the tapping process, high-pressure gas is injected in reverse into the outlet area of ​​the tapping port through a nozzle that is aligned at close range. The airflow forces the slag and molten steel in the tapping port back, thereby blocking the slag from falling directly from the tapping port and forming an air curtain or air column above the tapping port in the furnace to prevent the slag from falling back into the ladle. While this method boasts a high success rate in blocking slag after discharge, it suffers from several fatal flaws, primarily: 1) Due to the significantly lower density of the high-pressure gas compared to the slag, large-diameter single-hole or multi-hole nozzles capable of delivering sufficient gas must be positioned close to the taphole outlet, blowing nitrogen upwards against the slag flow (for optimal results, the nozzle tip must even be flush with or at least level with the taphole outlet plane). This easily leads to partial or complete blockage of the nozzles by steel and / or slag, affecting the success rate and operational efficiency of slag blocking; 2) When the taphole opening experiences severe enlargement or irregularities due to slag erosion and / or mechanical damage, the airflow cannot completely block the slag, and some slag will still enter the ladle; 3) Steel and / or slag adhering to nozzles that are not cleaned in time often impact and damage the refractory bricks at the taphole outlet when the nozzle moves at high speed towards it; 4) The permissible range of variation in the spatial relationship between the nozzle and the taphole outlet is very small. The slag blocking effect is highly dependent on the angle / distance between the nozzle and the outlet of the steel tapping hole. The sticking of steel and slag at the outlet of the steel tapping hole and the sticking of steel and slag at the nozzle and / or swing arm joint of the slag blocking device will seriously affect the success rate of slag blocking; 5) In order to achieve a better effect, the nozzle of the blowing system must adopt a fast swing mode, and the required equipment structure is relatively complex; 6) The blowing gas, nozzle cooling water and fast swing cylinder drive require a lot of media, and there are also many corresponding pipelines, which require a lot of the rotary joint channel of the converter ring trunnion; 7) The maintenance workload of the system device is large and the maintenance requirements are high, including: (1) The nozzle is in a high temperature zone for a long time, which is easy to burn and deform, and needs to be replaced regularly; (2) There is a risk of water leakage in the water-cooled spray gun and swing mechanism, which may cause serious deformation; (3) The frequent splashing of steel slag during the working process may clog the nozzle, which needs to be cleaned and replaced regularly; 7) Spray gun maintenance and nozzle replacement require working time, which affects the continuity of production; 8) It is difficult to meet the process assurance of steel grades with strict requirements for molten steel quality. In summary, the main problems with pneumatic slag blocking technology are unstable slag blocking effect, high maintenance requirements, and significant production time consumption. For steel mills that pursue stable molten steel quality and high-purity steel production, pneumatic slag blocking has been gradually replaced by more reliable slag blocking technologies such as sliding plate slag blocking.

[0005] The converter tapping slide gate slag-blocking technology is an advanced method that uses a hydraulically driven slide gate mechanism to quickly close the tapping spout, effectively controlling the concentrated slag discharge at the tapping endpoint. Its core principle is inspired by the ladle sliding nozzle technology, installing a slide gate system at the tapping spout outlet. The relative misalignment of the upper and lower slide gates controls the opening and closing of the steel flow channel, effectively preventing slag from entering the ladle at the end of tapping. While the slide gate slag-blocking technology is effective in preventing slag from entering the ladle, it does have the following main drawbacks and shortcomings:

[0006] 1) The system is complex and requires high maintenance. (1) The sliding plate slag blocking system includes multiple subsystems such as mechanical, hydraulic and detection, and its structure and construction are much more complex than other slag blocking methods; (2) The sliding plate slag blocking device is large in size, and the space in the converter tapping area is limited. It needs to meet specific geometric size requirements (such as the distance between the tapping port and the support ring, the operating space, etc.) during installation, and the layout and installation are difficult; (3) The system maintenance workload is large and the personnel requirements are high; (4) The refractory materials such as sliding plate bricks need to be replaced regularly (usually about 15 heats). The replacement process involves a long debugging time and a poor working environment.

[0007] 2) High operating costs. The initial investment in the entire system (including the mechanical body, hydraulic station, detection system, and control system) is large, the cost per unit of refractory material consumed is significantly higher than other methods, and the labor costs involved are also relatively high.

[0008] 3) Limitations in process operation. (1) It is impossible to control the eddy slag during the tapping process. It needs to be used in conjunction with other methods to control process slag, especially in the case of large-diameter tapping outlets. (2) It is impossible to resolve the contradiction of both clearing the molten steel and reducing slag outflow at the tapping end. (3) When the tapping outlet is severely eroded and irregularly shaped, it may affect the sealing effect of the nozzle bricks and pose a risk of molten steel leakage. (4) It is highly sensitive to the oxidation and temperature of molten steel, which increases the risk of molten steel leakage, especially in the case of the end target of low-carbon high-temperature blowing.

[0009] 4) It will have some impact on the production rhythm. Changing slide block requires furnace shutdown time, and equipment maintenance also requires dedicated non-operation time, which may affect the overall production efficiency of steel plants with high-paced production. Summary of the Invention

[0010] 1. The problem to be solved

[0011] The purpose of this invention is to address the problems of slag vortex entrainment in the steelmaking converter tapping process and slag overflow into the ladle at the tapping endpoint, and to provide a simple, convenient, and low-cost solution that can simultaneously replace existing technologies for controlling slag entrainment in the process and controlling slag overflow at the endpoint.

[0012] 2. Technical Solution

[0013] The technical solution adopted in this invention is as follows: Water is intermittently sprayed from outside the furnace into the tapping outlet before the molten steel vortex begins to appear and / or continuously sprayed at the moment when the slag begins to surge out in concentrated bursts after the molten steel has been tapped. Utilizing the water vapor generated by the flash evaporation of heated water and its explosive kinetic energy: 1) During the tapping process, the intensity of the vortex on the surface of the molten steel in the furnace is weakened by intermittently disrupting the steel flow state in the tapping outlet, thereby reducing slag entrapment; and 2) At the end of the tapping process, the slag that has flowed from the furnace into the tapping outlet is reversed and continuously prevented from flowing back into the tapping outlet. This achieves effective suppression of slag falling from the tapping outlet into the ladle during and at the end of the tapping process using the same device / system. Specifically:

[0014] Firstly, 1) before the slag above the tapping spout is engulfed by the swirling molten steel in the furnace during / later stages of tapping, water is intermittently sprayed from outside the furnace into the tapping spout. The water vapor generated by the rapid evaporation of heated water and its explosive kinetic energy periodically disrupt the state of the steel flow in the tapping spout, intermittently interfering with the generation of strong swirling slag above the tapping spout, and continuously inhibiting the slag from being engulfed by the molten steel swirling slag into the tapping spout; and / or 2) at the moment when the molten steel is exhausted at the end of tapping and the slag begins to flow out in concentrated bursts, water is continuously sprayed from outside the furnace into the tapping spout. The water vapor generated by the rapid evaporation of heated water and its explosive kinetic energy reverse the flow of slag that has flowed from the furnace into the tapping spout and continuously prevent the slag from flowing back into the tapping spout.

[0015] Secondly, the water jet injected into the outlet of the steel tapping hole is a water jet that penetrates the molten metal and flows out of the outlet and enters the outlet. The acute angle between the central axis of the water jet and the central axis of the outlet is 25~65°.

[0016] Furthermore, the system device used for the jet water flow consists of: 1) a single-channel / dual-channel water jet spray gun mechanism; 2) a nozzle installed at the front end of the spray gun; 3) a jet water delivery pipeline and valve group; 4) a converter tapping tilt angle detector for controlling the start of intermittent spraying and the stop of continuous spraying; 5) a slag entrainment detection instrument for controlling the start of intermittent / continuous spraying; and 6) a jet water flow controller.

[0017] Furthermore, the water jet spray gun mechanism is installed on the converter body and is either fixed or retractable / rotating / swinging on a fixed base.

[0018] Furthermore, the nozzle is a liquid jet nozzle.

[0019] The technical principles that differentiate the present invention from existing technologies are as follows:

[0020] 1) The energy required to disrupt the state of the steel flow can be easily obtained by spraying water into the outlet of the steel tapping hole and by utilizing the thermal energy of the molten steel.

[0021] In the later stages of the tapping process, when slag entrainment by molten steel vortex is about to occur, water is intermittently sprayed from outside the furnace into the tapping outlet, penetrating the steel flow. The small amount of water injected into the molten steel during the spraying process causes the water vapor to evaporate rapidly at the high temperature of the molten steel, and the resulting gas explosion and energy disrupt the rotational state of the molten steel flow in the tapping outlet. This is then transmitted upwards by utilizing the continuity of the fluid, affecting the vortex flow field on the molten steel surface above the tapping outlet and weakening the vortex intensity. As a result, the ability of the molten steel vortex to entrain slag disappears instantly or is greatly reduced, thereby achieving the goal of reducing the amount of slag entrained by the molten steel vortex.

[0022] The relevant principles in the aforementioned applications are as follows: (1) When the converter taps steel, the molten steel flowing through the tapping port is affected by various factors such as the morphology of the tapping port inlet area and internal channels, the initial flow state of the molten steel in the furnace, the disturbance of the molten steel rotating in the converter, and even the Coriolis force. As the molten steel level in the furnace decreases, the molten steel above the tapping port rotates and generates a vortex core at the steel-slag interface, which also gradually deepens. Since the molten steel at the vortex core has the highest rotation speed, the negative pressure formed is also the highest. The high-speed rotating molten steel causes the slag and / or furnace gas above the tapping port to be drawn into / flow into the vortex core by the negative pressure and flow into the ladle with the molten steel. (2) Since the ability of the vortex to draw slag and furnace gas is positively correlated with the degree of rotation of the molten steel, the external force can be used to momentarily interfere with and destroy the swirling flow of the molten steel, thereby weakening or even eliminating the vortex flow field and reducing the amount of slag carried into the ladle by the molten steel vortex during the tapping process. When the external force is removed, the molten steel above the tapping port will gradually form a vortex again and continuously strengthen, which will also aggravate the degree of obvious molten steel vortex slag entrainment. The lower the molten steel level, the shorter the time for the molten steel vortex slag entrainment to reappear after the external force is removed. (3) Due to the continuity of the molten steel flow in the tapping port, when the rotation state of the molten steel flow stream in the tapping port is destroyed by an external force, the destructive force will be transmitted upwards and interfere with the flow state of the molten steel in the furnace above the tapping port, thereby destroying and weakening the flow field and intensity of the vortex on the molten steel surface, that is, its ability to entrain slag. (4) Since the water flow from outside the furnace to the outlet of the steel tapping hole is heated and rapidly evaporated into steam gas, the tapping hole channel will be instantly filled with steam and affect the tapping. Also, since the vortex flow field of the molten steel surface above the tapping hole in the furnace needs a time process to go from being weakened by interference to becoming strong again to produce obvious molten steel slag entrainment, it is neither possible nor necessary to continuously or frequently turn on the water jet.

[0023] 2) The energy required to drive back the slag can be easily obtained by injecting water jets into the tapping outlet and by utilizing the thermal energy of the slag.

[0024] At the moment when the molten steel has been completely discharged and the slag begins to gush out in concentrated bursts at the tapping point, a continuous jet of water powerful enough to penetrate the molten metal about to flow out of the tapping point is sprayed. The explosive steam gas, which is nearly 6,000 times the volume of water, is generated by the rapid evaporation of the heated water and its enormous energy drives back the slag that has already flowed into the tapping point from the furnace and continuously prevents the slag from flowing back into the tapping point. At the same time as the water jet is sprayed, the furnace body is rotated to raise the tapping point, thereby blocking the large amount of slag from flowing out at the tapping point.

[0025] 3) As an incompressible liquid, water jets have significant advantages in terms of usage characteristics and transmission properties.

[0026] In the application of jetting into high-temperature melts, water has a higher density, is easier to pressurize, and requires a much smaller amount of water compared to the gas used in pneumatic slag removal. Compared to gas jets, water jets (especially liquid column jets) have a larger transmission mass, less kinetic energy loss, and less stream expansion and dilation. They can be used for long-distance jetting without interference between environmental equipment and are also easier to control in terms of jet direction and focus on the landing point.

[0027] 4) Selection and determination of the angle between the water jet centerline and the steel outlet centerline.

[0028] For the water jet to effectively disrupt the steel flow and / or reverse the flow of slag already flowing into the taphole, it must be injected from outside the furnace in the opposite direction to the steel flow to achieve evaporation and vaporization. Furthermore, the water jet's central axis must intersect the taphole channel at a specific angle, ideally between 25° and 65°. An angle that is too large or too small will negatively impact the slag-blocking effect and cause other adverse effects. If the angle is too small, the lance must be positioned closer to the taphole, making it susceptible to damage from the impact of the steel flow. An almost vertical water jet also hinders the final stage of evaporation and vaporization within the taphole, preventing a tight seal against slag. Conversely, if the angle is too large, while positioning the lance to the side of the taphole provides protection, only a small amount of water can penetrate the taphole, resulting in a shallow penetration and hindering the disruption of the steel flow and the sealing of the slag. In order to ensure that the water jet can maintain a relative position between the tapping angle of the converter and the tapping outlet during the process of adjusting the tapping angle to achieve the maximum molten steel depth at the tapping outlet and during the rapid lifting of the furnace at the end of the tapping process, the spray gun mechanism of the water jet system must be installed on the converter body and be able to maintain a fixed positional relationship between the spray gun nozzle jet axis and the tapping outlet axis and its outlet.

[0029] 5) Selection and determination of water pressure, flow rate, and jet time.

[0030] The core of this technical solution lies in utilizing the gaseous energy and kinetic energy of water vapor, which is generated by the rapid evaporation of molten steel and / or slag flowing into the taphole after being injected from outside the outlet. To ensure the water jet can penetrate the molten flow and enter the taphole outlet, a certain jet velocity and kinetic energy are required. This necessitates specific water pressure requirements before the nozzle that stimulates the water jet's penetration. Furthermore, to suppress vortexing and slag entrainment during tapping, it is crucial to avoid both excessively low water flow rates that would prevent the generated water vapor and its kinetic energy from disrupting the flow of the molten steel within the taphole, and excessively high water flow rates or prolonged intermittent injection times that could lead to excessive evaporation of water vapor, causing flow obstruction or momentary interruption during tapping. Excessive water flow rate or prolonged intermittent spraying can cause excessive water vapor evaporation at the tapping spout, leading to backflow interruption or even water vapor explosion during the tapping process. This can cause impact damage to the refractory material at the tapping spout. Therefore, controlling the water flow rate and duration is crucial. Similarly, to prevent a large influx of slag into the tapping spout at the tapping endpoint, it is also necessary to control the water flow rate. This ensures sufficient water vapor is generated so that the slag flowing into the tapping spout can be fully driven back into the furnace and tightly prevented from flowing out again. However, it also prevents excessive water from being sprayed, which could cause an excessive amount of water vapor to explode and cause impact damage to the refractory material at the tapping spout, or excessive cooling of the refractory material at the tapping spout, resulting in severe thermal shock. Given that the static pressure of the molten steel above the outlet of the tapping vessel in the middle and later stages of tapping is approximately 100-150 kPa, and the dynamic pressure of the freely falling, confined molten steel stream at the outlet is also not large, under the economical industrial water condition of 500-800 kPa, and based on the tapping vessel diameter, strictly following the principles of increasing the jet flow rate and increasing the jet time, by trying various types and parameters of nozzles, it is entirely possible to select and determine the specific and suitable water jet pressure range and flow rate range from the existing liquid column flow nozzle standards. It is also possible to determine the jet time of the intermittent jet water flow aimed at disrupting the state of the tapping steel stream.

[0031] The water flow rate of a jet stream is specifically calculated as Q = q + a * ((D - 100) / 100); where Q is the water flow rate (liters / minute), q is a basic water flow rate of 2 to 3 liters / minute, which is taken comprehensively based on nozzle characteristics and the distance between the nozzle and the steel outlet, D is the nominal diameter of the steel outlet (millimeters), and a is a coefficient with a value range of 1.0 to 2.0, which is related to the angle between the jet stream and the steel flow stream.

[0032] 5) Regarding the time interval of intermittent jet water flow

[0033] The time interval of intermittent water jet injection is crucial for suppressing slag entrainment and vortex formation in the molten steel during tapping. If the interval is too long, exceeding the time required for the vortex on the molten steel surface to re-establish a high-speed swirling slag entrainment state after being eliminated or weakened, excessive slag will enter the ladle. Conversely, if the interval is too short, significantly shorter than the time required for the vortex to re-establish a high-speed swirling slag entrainment state, it will affect the tapping process and cause a slight increase in hydrogen in the molten steel. In practice, the time when obvious slag entrainment reappears after intermittent water jet injection can be statistically analyzed using a slag detection device and the tapping tilt angle of the converter body. This allows for the determination of intermittent water jet injection time intervals with a certain lead time at different tilting angles. Furthermore, the real-time monitoring values ​​from the slag detection device can be used to initiate intermittent water jet injection in advance.

[0034] 6) About water jet spray guns

[0035] Waterjet lances come in single-channel and dual-channel versions. In theory, a single-channel lance can simultaneously meet the requirements of suppressing slag entrapment during tapping and blocking slag outflow at the tapping endpoint. However, when conditions permit, a dual-channel lance offers greater flexibility and reliability. Dual-channel lances can use nozzles with identical parameters as backups for each other. Alternatively, one channel can be used to suppress slag entrapment during the process, while both channels can be used simultaneously to block slag outflow at the endpoint. Another option is to use a small nozzle channel to suppress slag entrapment during the process and a large nozzle channel to block slag outflow at the endpoint.

[0036] 7) Regarding the issue of hydrogenation in molten steel injected with jet water

[0037] During the tapping process, the water vapor generated by the intermittent spraying of water into the molten steel stream will inevitably increase the hydrogen content of the steel to a certain extent. However, since the spraying only begins in the middle and late stages of tapping and the spraying time in each intermittent spraying cycle is extremely short while the pause time is dozens of times longer than the spraying time, coupled with the fact that the oxygen content of the tapped steel is often high, the actual effect of the sprayed water stream on increasing the hydrogen content of the molten steel is negligible.

[0038] 8) Safety issues related to water jets

[0039] When a water jet penetrates the molten flow, it is heated and rapidly evaporates into water vapor, generating enormous expansion kinetic energy. When the water flow rate is too high, the large expansion impact of the water vapor can damage the refractory bricks at the tapping point. When the water flow rate is too high, it can also cause more serious splashing of molten steel and / or slag, which may cause injury and damage. On the one hand, when implementing this technical solution, it is necessary to try to gradually increase the flow rate of the water jet from small to large, and to strictly limit the upper limit of the spray water flow rate; on the other hand, given that the energy required for the water vapor gas and its energy to destroy the state of the molten steel flow in the tapping port during the tapping process and to block the slag from flowing out at the tapping end is very small, it is entirely possible to safely and reliably reduce the slag flow at the tapping port during the tapping process. The reasons are as follows: (1) During the middle and late stages of tapping and at the end of the tapping process, the tapping port taps almost vertically downwards. When water is sprayed, the water jet penetrates the molten flow from the tapping port outlet and enters the tapping port. When the water flashes and evaporates, a small amount of weakly downward divergent molten droplets will fall directly into the ladle. When the water flashes and evaporates, a small amount of weakly upward reverse surging molten droplets will remain in the converter; (2) (2) The intermittent water jet can change the state of the molten steel flow in the tapping port by only intermittently spraying for a very short time. The time of the spray pause within a spray cycle is tens of times longer than the spraying time. (3) The tapping port has good permeability and explosion-proof properties. The high-density molten steel / slag itself has a large buffer. The impact of a small amount of water flash evaporation that only needs to disrupt the state of the molten steel flow on the refractory bricks at the tapping port can be well controlled by limiting the maximum water flow rate. (4) After the continuous water jet at the tapping end, the slag will not continue to flow out of the tapping port. The upward-flowing melt (mainly slag) droplets will still remain in the converter. (5) At the same time as the water jet starts at the tapping end, the converter will also tilt and lift the furnace. The static pressure of the slag will gradually decrease, and the slag surface will quickly retreat below the furnace inlet of the tapping port. At this time, the slag will no longer flow out, and the water jet should be stopped immediately. In short, under the strict limitation of water flow rate, there will be no damage to the refractory bricks at the tapping port, and there will be no splashing of molten steel and / or slag that could endanger personal and equipment safety. Beneficial effects

[0040] Compared with existing technologies, the method of the present invention achieves the following beneficial effects:

[0041] 1) The total amount of slag carried by the vortex of molten steel during the later stage of tapping and concentrated in the ladle at the end of tapping is significantly reduced, which correspondingly reduces (1) the amount of phosphorus return to molten steel caused by subsequent slag deoxidation and refining reduction, (2) the consumption of molten steel deoxidation and alloying materials, and (3) the pollution of molten steel by harmful substances in slag.

[0042] 2) Using only the same set of equipment / systems can suppress the slag vortex during the tapping process and block the concentrated slag outflow at the tapping end. In particular, it can significantly reduce the slag vortex during the tapping process, which is difficult to control effectively with existing technologies.

[0043] 3) The disruption of the rotation state of the molten steel stream in the tapping port by the intermittent water jet during the tapping process can also reduce the nitrogen increase in the corresponding part of the furnace gas drawn into the molten steel vortex.

[0044] 4) The liquid jet used has high kinetic energy, low expansion, and focused landing point. The spray gun equipment can be installed on the furnace body at a position far away from the steel tapping outlet, which can safely and stably achieve long-distance spraying.

[0045] 5) Compared with sliding plate slag blocking and pneumatic slag blocking, water jet spraying system is much simpler, lighter and smaller in terms of both system complexity and device construction.

[0046] 6) It only consumes less than one liter of water to suppress slag entrapment and block slag flow at the tapping outlet, greatly reducing the cost of slag discharge at the tapping outlet, especially compared with the overall cost of the sliding plate slag blocking method.

[0047] 8) The method of the present invention is simple, easy to implement, flexible and reliable. The related equipment is extremely lightweight and inexpensive, with almost no operating and maintenance costs and very little production time required. Attached Figure Description

[0048] Figure 1 The present invention provides a schematic diagram of a method for reducing slag discharge at the tapping port during the converter steelmaking process, specifically under condition 1 (continuous injection of slag at the tapping end point). In the diagram, 11 represents the inner contour of the converter lining, 12 represents steam and slag, 13 represents the water jet lance and nozzle, 14 represents the water jet, 15 represents the inner contour of the tapping port, 16 represents the central axis of the tapping port, 17 represents the central axis of the water jet, and 18 represents the acute angle formed by the intersection of the central axis of the water jet and the central axis of the tapping port.

[0049] Figure 2 The present invention provides a schematic diagram of working condition 2 (intermittent spraying moment to suppress slag entrainment in the vortex of molten steel during the later stage of the steel tapping process) of a method for reducing slag discharge at the tapping port during the steel tapping process. In the diagram, 21 is the inner contour of the converter lining and the tapping port, 22 is the molten steel and slag, 23 is the water jet lance and nozzle, 24 is the water jet, 25 is the tapping stream and steam, 26 is the central axis of the tapping port, 27 is the central axis of the water jet, and 28 is the acute angle between the central axis of the water jet and the central axis of the tapping port. Detailed Implementation

[0050] The present invention provides a method for reducing slag discharge at the tapping port during the converter steelmaking process, specifically implemented as follows:

[0051] Before the molten steel vortex in the furnace engulfs the slag above the taphole appears during / in the later stages of tapping, water is intermittently sprayed from outside the furnace into the taphole outlet (see instruction manual appendix). Figure 2), utilizing the water vapor generated by the flash evaporation of heated water and its explosive kinetic energy to periodically disrupt the state of the steel flow inside the tapping spout, intermittently interfering with the generation of strong eddies on the molten steel surface above the tapping spout, and continuously inhibiting slag from being drawn into the tapping spout by the molten steel eddies; and / or 2) at the moment when the molten steel is almost completely discharged and the slag begins to concentrate and surge out at the end of the tapping process, continuously spraying water from outside the furnace into the tapping spout outlet (see instruction manual appendix). Figure 1 The system utilizes the water vapor generated by the flash evaporation of heated water and its explosive kinetic energy to reverse the slag that has flowed from the furnace into the taphole, continuously preventing slag from flowing back into the taphole. The trigger for intermittent spraying during tapping can be determined by combining the slag discharge situation from the previous tapping process with the tapping time, or by setting a limit on the instantaneous slag discharge rate of the slag discharge detector, or by presetting the converter tilting angle. The different spray pause times during intermittent water spraying can be differentiated by presetting the converter tilting angle. The trigger for continuous spraying at the tapping endpoint is mainly determined by setting a limit on the instantaneous slag discharge rate of the slag discharge detector.

[0052] The water jet injected into the tapping outlet is a water jet that penetrates the tapping outlet, flows out of the molten metal, and enters the tapping outlet. The acute angle between the central axis of the water jet and the central axis of the tapping outlet is 25° to 65°.

[0053] The system for jet water flow consists of: 1) a single-channel / dual-channel water jet spray gun mechanism; 2) a nozzle installed at the front end of the spray gun; 3) jet water delivery pipeline and valve group; 4) a converter tapping tilt angle detector for controlling the start of intermittent spraying and the stop of continuous spraying; 5) a slag entrainment detection instrument for controlling the start of intermittent / continuous spraying; and 6) a jet water flow controller.

[0054] The water jet spray gun mechanism is fixedly installed on the converter body. It is a fixed or fixed-base spray gun that can be telescopic / rotate / oscillate. Throughout the entire steel tapping process, it maintains a relative positional relationship with the steel tapping outlet to ensure that the water jet is injected into the steel tapping outlet.

[0055] The nozzle installed at the front end of the spray gun is selected as a liquid jet nozzle, preferably a liquid jet nozzle with an elliptical / circular cross section. The jet is injected into the steel outlet from the edge of the outlet, and the central axis of the jet intersects with the central axis of the outlet channel.

[0056] The specific flow rate of the jet water flow can be calculated using Q=q+a*((D-100) / 100); where Q is the water flow rate (liters / minute), q is a basic water flow rate of 2~3 liters / minute based on nozzle characteristics, distance between the nozzle and the steel outlet, D is the nominal diameter of the steel outlet (mm), and a is a coefficient ranging from 1.0 to 2.0 based on the angle between the jet and the steel flow stream.

[0057] During the non-spraying pause in the steel tapping process, a small amount of water is passed through the nozzle. This serves two purposes: firstly, to prevent steel from sticking to the nozzle, and secondly, to cool the spray gun and nozzle. It also allows for the maintenance of a certain water pressure in front of the nozzle to ensure rapid spraying response and accurate water flow during the spraying process.

[0058] The specific applications of the present invention will be further described below with reference to the embodiments:

[0059] Example 1

[0060] Basic conditions: 300-ton top and bottom blown converter, mainly producing high-quality steel, with high requirements for slag blocking effect; nominal diameter of the tapping outlet is 220 mm, and the average tapping time is 5.5 minutes; equipped with a tapping outlet slag detection instrument and a converter tilting angle detection instrument; according to the detection and analysis: (1) when the converter tilts at 85° during the tapping process (about 50% of the steel is tapped), molten steel vortex slag entrainment begins to appear; (2) in the middle and late stages of tapping, the time for the molten steel surface vortex in the furnace to re-form a strong vortex after being disturbed is greater than 15 seconds and 12 seconds respectively; industrial water pressure is 500 kPa.

[0061] Implementation plan: A fixed-base, swing-type single-channel spray gun mechanism; before spraying, the distance between the nozzle and the outlet of the tapping port is approximately 1.2 meters; during the tapping process, when the converter tilts 83° (approximately 45% of the tapping volume), intermittent water jet spraying begins; the acute angle between the water jet's central axis and the tapping port's central axis is 25°; selecting q = 2 L / min, a = 1.0, calculating Q = 3.2 L / min; a circular cross-section liquid column nozzle with an orifice diameter of 1.8 mm; the spraying time of the intermittent water jet during the tapping process is 0.9 seconds. The spraying process is repeated for 15 seconds, 10 seconds, and 7 seconds per pause during the early, middle, and late stages of tapping, respectively. Alternatively, intermittent spraying may be resumed when the slag content in the stream exceeds 3% as indicated by the slag detection instrument. The division between the middle and late stages of tapping is determined by the converter tilting angle. During tapping, the cooling water from the low-pressure open-circuit equipment used by the spray gun mechanism is introduced into the jet water channel to prevent the nozzle from sticking to steel and to prevent the spray gun and nozzle from overheating. At the end of tapping, when the slag content in the tapping stream increases to 40%, continuous spraying begins for 8 seconds, and the converter is tilted simultaneously to end tapping.

[0062] Results achieved: Compared with the original pneumatic slag-blocking method with inverted cone / frustum slag-blocking device for throwing refractory materials in the furnace, the total slag discharge during steelmaking is reduced by more than 20%.

[0063] Example 2

[0064] Basic conditions: 210-ton top and bottom blown converter, mainly producing high-quality steel, with high requirements for slag blocking effect; nominal diameter of the tapping outlet is 170 mm, tapping time is 5-7 minutes; equipped with a tapping outlet slag detection instrument and a converter tilting angle detection instrument; according to the detection and analysis: (1) slag entrainment of molten steel begins to appear at 60% of the tapping time; (2) the time for the slag entrainment on the surface of molten steel in the furnace to re-form a strong vortex after being disturbed in the middle and late stages of tapping is greater than 18 seconds; industrial water pressure is 800 kPa.

[0065] Implementation plan: Replace the slag baffle at the tapping endpoint; a fixed dual-channel spray gun mechanism with a nozzle spacing of 1.6 meters from the tapping outlet; when the tapping outlet is not changed, intermittent water jetting begins at 55% of the tapping time of the previous furnace run; the acute angle between the water jet's central axis and the tapping outlet's central axis is 65°; select q=3 L / min, a=2.0, calculate Q=4.4 L / min; select two elliptical cross-section liquid jet nozzles with a major-minor axis ratio of 1.5 and an equivalent diameter of 1.4 mm (one nozzle per channel). (Only), during the intermittent water spraying process in the tapping process, single-channel spraying is used to prevent excessive instantaneous water volume; the spraying time of the intermittent water flow during the tapping process is 1.2 seconds, the spraying pause time in the middle of the tapping process is 16 seconds, and the spraying pause time in the later stage of the tapping process is 10 seconds; during the spraying pause period in the tapping process, the nozzle is supplied with water at 15% of the spraying flow rate; depending on the strictness of the phosphorus content of the smelting steel grade, when the proportion of slag in the tapping stream increases to 25~60% at the end of the tapping process, dual-channel continuous spraying is performed for 7 seconds, and the converter is tilted at the same time to end the tapping process.

[0066] Results achieved: Compared with the original single slide plate slag blocking method, the amount of slag discharged during steelmaking was reduced by more than 30%, and the overall operating cost was reduced by more than 95%.

[0067] Example 3

[0068] Basic conditions: 120-ton top and bottom blown converter, nominal diameter of tapping outlet is 140 mm; the existing sliding plate slag blocking form is maintained, and intermittent water jetting is implemented during the tapping process to reduce slag runoff; equipped with tapping outlet slag runoff detector and converter tilting angle detector; after detection and analysis: (1) slag entrainment of molten steel begins to appear when the tapping volume is about 70%; (2) the time for the molten steel surface vortex in the furnace to re-form a strong vortex after being disturbed in the middle and late stages of tapping is 16-10 seconds; industrial water pressure is 600 kPa;

[0069] Implementation plan: Fixed single-channel spray gun mechanism, with a distance of 1.5 meters between the spray nozzle and the steel tapping outlet; intermittent water spraying begins when 60% of the steel has been tapped; the acute angle between the central axis of the water jet and the central axis of the steel tapping outlet is 45°; q = 2 liters / minute, a = 1.5, and Q = 2.6 liters / minute are selected; a circular cross-section liquid column nozzle with a diameter of 1.5 mm is selected; the start time of spraying and the starting points of the middle and late stages are determined according to 60% and 80% of the previous furnace tapping time; the spraying time of the intermittent water jet during the tapping process is 1.2 seconds, the spraying pause time in the middle stage of tapping is 15 seconds, and the spraying pause time in the late stage of tapping is 12 seconds; during the spraying pause period in the tapping process, the nozzle is filled with water at 15% of the spray flow rate; at the end of the tapping process, when the slag content in the tapping stream accounts for 60%, continuous spraying is performed for 7 seconds, and the converter is tilted at the same time to end the tapping.

[0070] Results achieved: The total amount of slag discharged during steelmaking was reduced by more than 15% compared to the original method of using only a sliding plate to block slag.

[0071] Example 4

[0072] Basic conditions: 180-ton top and bottom blown converter, nominal diameter of tapping outlet is 160 mm; the existing slag blocking method of throwing refractory material into the furnace into inverted cone / inverted truncated cone slag blocking device (also known as slag blocking rod) is still maintained, and continuous water jetting at the tapping end is implemented to reduce slag at the end; equipped with tapping outlet slag detection instrument and converter tilting angle detection instrument; after detection and analysis: (1) slag vortex of molten steel begins to appear when the tapping amount is about 60%, (2) the time for the vortex of molten steel surface in the furnace to re-form a strong vortex after being disturbed during tapping is greater than 17 seconds; the water pressure of industrial water is 600 kPa;

[0073] Implementation plan: A rotatable single-channel spray gun mechanism with a fixed base; the distance between the spray nozzle and the outlet of the steel tapping hole is 1.3 meters; the acute angle between the central axis of the water jet and the central axis of the steel tapping hole is 35°; q=2.4 liters / min, a=1.5, and Q=3.3 liters / min are selected; a circular cross-section liquid column nozzle with a diameter of 1.8 mm is selected; the spraying pause times in the middle and late stages of steel tapping are 12 seconds and 8 seconds, respectively; during the spraying pause period in the steel tapping process, the nozzle is filled with water at 15% of the spray flow rate; after the slag-blocking bar is thrown in the furnace, if the slag content in the steel tapping stream at the end of the tapping point is 40%, spray continuously for 7 seconds, and at the same time tilt the converter to end the steel tapping.

[0074] Results achieved: Compared with the original method of using an inverted cone / frustum slag-blocking device with refractory material thrown into the furnace, the amount of slag discharged during steelmaking was reduced by more than 15%.

[0075] This specification describes the present invention in detail with reference to specific exemplary embodiments. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description and accompanying drawings are only for illustrative purposes and are not intended to limit the implementation of the invention. Therefore, they do not have substantial technical significance. Any related modifications and adjustments, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed in the invention. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are only for clarity of description and are not intended to limit the scope of implementation. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention. In addition, the background section is intended to illustrate the current state of research and development and significance of this technology, and is not intended to limit the scope of this invention or this application and its application area. More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0076] It should be understood that the term "and / or" used in this article is a description of the relationship between related objects, and is defined to indicate that there can be three relationships. For example, a and / or b can represent three cases: a exists alone, a and b exist simultaneously, and b exists alone. The character " / " in this article is defined to represent an "or" relationship between the preceding and following related objects.

Claims

1. A method for reducing slag discharge at the tapping port during the converter steelmaking process, characterized in that: 1) During / before the molten steel vortex in the furnace is about to engulf the slag above the taphole during the tapping process, water is intermittently sprayed from outside the furnace into the taphole outlet. The water vapor generated by the rapid evaporation of the heated water and its explosive kinetic energy periodically disrupt the state of the steel flow in the taphole, intermittently interfering with the generation of strong vortices on the surface of the molten steel above the taphole, and continuously inhibiting the slag from being engulfed by the molten steel vortex into the taphole; and / or 2) At the moment when the molten steel is exhausted at the end of the tapping process and the slag begins to flow out in a concentrated manner, water is continuously sprayed from outside the furnace into the taphole outlet. The water vapor generated by the rapid evaporation of the heated water and its explosive kinetic energy reverse the flow of slag that has flowed from the furnace into the taphole and continuously prevent the slag from flowing back into the taphole.

2. The method for reducing slag discharge at the tapping port during the converter steelmaking process according to claim 1, characterized in that: The water jet injected into the outlet of the steel tapping hole is a water jet that penetrates the molten metal and flows out of the outlet and enters the outlet. The acute angle between the central axis of the water jet and the central axis of the outlet is 25° to 65°.

3. The method for reducing slag discharge at the tapping port during the converter steelmaking process according to claim 1, characterized in that: The system device for the jet water flow consists of: 1) a single-channel / dual-channel water jet spray gun mechanism; 2) a nozzle installed at the front end of the spray gun; and 3) a jet water delivery pipeline and valve assembly. 4) Converter tapping tilt angle detector used to control the start of intermittent injection and the stop of continuous injection; 5) Instrument for detecting the amount of slag entrainment in the tapping steel flow used to control intermittent / continuous injection; 6) Controller for the jet water flow.

4. A method for reducing slag discharge at the tapping port during the converter steelmaking process according to claim 3, characterized in that: The water jet spray gun mechanism is installed on the converter body and is either fixed or retractable / rotatable / swinging on a fixed base; the nozzle is a liquid jet nozzle.

Images