Method for non-mechanical breaking of slag crust in a slag channel of a blast furnace

Abstract

A non-mechanical method for breaking the slag crust in a blast furnace slag channel. When a slag crust is formed in the target slag temperature measurement area or flow detection area in the blast furnace slag channel, a high-temperature flame heating gun is used to melt a liquid cutting slag line on the slag crust surface of the blast furnace slag channel with a high-temperature flame with a temperature greater than or equal to 1500 DEG C. Then, a low-melting-point mineral flux with a melting point of 900-1200 DEG C is added to the liquid cutting slag line. Then, the high-temperature flame heating gun is used to sweep the liquid cutting slag line while continuously adding the low-melting-point mineral flux thereto, so that the melting depth is continuously increased and the target closed loop is continuously pushed forward. Finally, the slag crust in the closed loop liquid cutting slag line is removed to expose the active flowing blast furnace slag below, thereby meeting the detection requirements of the blast furnace slag channel slag temperature and flow detection device.

Description

Technical Field

[0001] This invention relates to the field of blast furnace technology, and in particular to a non-mechanical method for breaking the slag shell in blast furnace slag channels. Background Technology

[0002] Under the dual-carbon context, the path to low-carbon and green development for steel enterprises still requires efficient recovery of waste heat from processes. Blast furnace slag waste heat, a high-value and high-quality waste heat resource for steel enterprises, contains nearly 60 kgce of heat per ton of slag. Although numerous technologies for its efficient recovery have been developed both domestically and internationally, a reliable, stable, and mature recovery path has yet to be established. The development of blast furnace slag waste heat recovery technology typically requires real-time online monitoring of the temperature and flow rate of the incoming blast furnace slag, and these monitoring devices all require instruments and sensors capable of visually detecting the surface of the slag.

[0003] During the blast furnace slag removal process, when the molten slag flows out of the skimmer, the slag temperature is typically between 1500 and 1350°C. It enters the blast furnace slag channel, which is generally U-shaped in cross-section. The molten slag must meander through this channel, traversing different lengths and curvatures, before reaching the slag treatment facilities. Furthermore, it usually passes through one or two sections of water-cooled slag channels of a certain length before reaching the treatment facilities. Therefore, as the blast furnace molten slag flows through these channels, the intense high-temperature radiation and heat loss through conduction with the cold slag channels often cause the molten slag to form a crust on the sides and surface during its flow (blast furnace molten slag generally hardens and solidifies when cooled to around 1250°C). This quickly results in two slag shells forming along the flow direction on both sides of the slag surface where it contacts the slag channel, with the molten slag flowing within these shells. In severe cases, the two slag shells merge at the upper surface, completely crusting the slag surface, with the molten slag flowing beneath the sealed shell. This poses significant challenges to real-time online temperature and flow rate monitoring of the molten slag.

[0004] Because both temperature detection and flow rate detection require sensors that can see the flowing slag surface and have a certain size, a completely solidified and sealed slag shell cannot allow infrared and visible light to escape, so the sensor cannot receive signals, and online detection is limited to pauses.

[0005] Typically, blast furnace slag waste heat recovery requires continuous and effective online monitoring of the slag temperature and / or slag flow rate before it enters the waste heat recovery equipment, allowing for real-time adjustment of process parameters. However, the slag in the blast furnace slag trench often forms a crust, and currently, no instrument can penetrate the crust to receive the heat rays emitted by the slag below and thus measure the temperature or flow rate.

[0006] Chinese patent application number 202220948985.0 discloses a device for breaking slag shells on the surface of molten iron, which uses a shell-breaking cone as a mechanical method to break up the slag shells on the surface of molten iron.

[0007] Chinese Patent Application No. 201520185290.1 ​​discloses a novel device for removing slag shells from molten iron ladles, which uses a crane hook to lift a cross-shaped four-claw anchor hook to hook and remove the slag shells from the molten iron ladle.

[0008] Chinese Patent Application No. 201821745586.4 discloses a solidified slag shell removal device for waste heat recovery of liquid slag. When high-temperature liquid slag heat recovery is carried out, the liquid slag is injected into the solidification mold of the waste heat recovery device to cool down. As a result, a solid slag shell is generated on the mold wall and gradually grows and thickens. The slag shell has a large thermal resistance, which inhibits the continued transfer of internal heat to the outside. Therefore, a mechanical removal device is used to remove the slag shell.

[0009] Chinese Patent Application No. 201911004494.X discloses a method for breaking the slag shell in the RH refining vacuum process, which mainly involves operating the ladle to lift relative to the immersion tube and using the strength of the immersion tube to break the slag shell.

[0010] Chinese patent application number 202210183185.9 discloses a method for solving the slag crust problem inside high-alumina steel ladles: controlling the aluminum content at the LF furnace outlet to exceed the upper limit of the judgment range by 0.5% to 0.7%; adding fluorite at the LF furnace outlet; and adding a slagging agent after the RH furnace treatment begins. This patent protects the crust formation of high-alumina steel slag inside ladles in the steel smelting field, and the fluorite used is a blocky ore, not fine mineral powder.

[0011] In summary, current blast furnace operations require manual mechanical breaking of the slag shell that partially or completely covers the temperature or flow detection zone in order to maintain the normal operation of continuous temperature and flow measurement devices. This is not only unsafe, creating significant safety hazards, but also increases the workers' working hours and intensity at high temperatures. Summary of the Invention

[0012] The purpose of this invention is to provide a non-mechanical method for breaking the slag shell in blast furnace slag channels. This method can safely and reliably expose the active molten slag surface beneath the crust covering the slag surface in the blast furnace slag channel, preventing the splashing of high-temperature molten slag during mechanical breaking of the slag shell and avoiding injuries or property damage, thus preventing safety accidents. At the same time, it will not have a harmful impact on the smooth flow of molten slag in the blast furnace slag channel, and can smoothly restore the normal operation of online detection devices such as molten slag temperature and flow rate measurement, ensuring the smooth progress of blast furnace molten slag waste heat recovery engineering technology.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows:

[0014] A non-mechanical method for breaking the slag shell in a blast furnace slag ditch involves first using a high-temperature flame torch (≥1500℃) to melt a liquid cutting slag line on the crusted slag surface. Then, a low-melting-point mineral flux (900-1200℃) is added to the liquid cutting slag line. The high-temperature flame torch is then used to sweep the liquid cutting slag line, forming a closed loop, while continuously adding low-melting-point mineral flux to increase the melting depth. Ultimately, the slag shell within the closed loop of the liquid cutting slag line falls off, exposing the actively flowing blast furnace slag below, thus meeting the detection requirements of the blast furnace slag temperature and flow detection device.

[0015] Preferably, a high-temperature flame is first used to melt a liquid cutting slag line on the slag crust surface of the blast furnace slag ditch. Then, a low-melting-point mineral flux is added to the liquid cutting slag line and swept and melted by a high-temperature flame. After the low-melting-point mineral flux melts quickly, it, together with the already melted slag shell and slag liquid, forms a high-temperature liquid slag pool. At this time, the high-temperature flame continuously impacts and disturbs the high-temperature liquid slag pool, causing its liquid surface to fluctuate back and forth, so that the slag shell is melted through. This process is repeated along the closed loop of the liquid cutting slag line, where the high-temperature flame moves to form a liquid slag line, low-melting-point mineral flux is added again, and the liquid slag line is blown by the high-temperature flame airflow. Finally, the slag shell surrounded by the melted closed loop liquid cutting slag line falls into the flowing blast furnace slag flow below due to its own weight.

[0016] Preferably, an insulating cover that moves with the high-temperature flame is arranged above the closed-loop liquid cutting slag line to shield the high-temperature flame and the high-temperature radiation of the liquid slag, thereby reducing heat loss and accelerating the melting and cutting speed.

[0017] Preferably, a low-melting-point mineral flux is added to the crusted slag surface within the closed-loop liquid cutting slag line.

[0018] Preferably, the low-melting-point mineral flux is selected from fluorite powder, cryolite powder, or low-melting-point glass powder.

[0019] Preferably, the slag shell size within the closed-loop liquid cutting slag line is 1 / 10 to 1 / 5 of the width of the slag surface of the slag groove crust.

[0020] Preferably, the high-temperature flame heating gun uses oxyacetylene, hydrogen-oxygen, or oxygen-propane, and the flame combustion temperature reaches 2000-3000℃.

[0021] When a crust forms on the surface of the molten slag in the slag trench, the surface temperature of the crust is approximately 600–800℃. Practice shows that the slag crust at this temperature still possesses considerable mechanical strength and is difficult to break without applying significant impact.

[0022] This invention employs a high-temperature flame (≥1500℃) to impact and heat the slag shell, causing it to remelt and fall off, thereby exposing the actively flowing molten slag surface beneath the shell and restoring the operation and normal functioning of the online monitoring equipment. For example, in flow rate detection, a specific area is selected within the slag channel where molten slag flows through the blast furnace to measure the slag flow rate. Since the molten slag temperature reaches over 1400℃, conventional immersion-type molten slag measurement methods are not feasible. Therefore, photoelectric sensing is often used to obtain multiple frames of images, followed by image processing to indirectly calculate the flow velocity, which is then multiplied by the cross-sectional area to obtain the flow rate. This method requires exposing the active molten slag surface.

[0023] If the slag shell is thick or the slag surface area to be exposed for observation is large, a certain closed path is needed to form a cutting line so that the slag shell can melt through and fall off. In this case, the process of flame impact heating and melting through the slag shell is slightly slow. Therefore, a high-temperature flame is first used to melt a liquid cutting slag line on a short closed loop. Then, a low-melting-point mineral flux is added to the liquid cutting slag line and swept and melted with a high-temperature flame. After the low-melting-point mineral flux melts quickly, it, together with the already melted slag shell and slag liquid, forms a high-temperature liquid slag pool. At this time, a high-temperature flame heating gun is used to heat the slag pool. The warm liquid slag pool is constantly impacted and disturbed, causing its surface to fluctuate back and forth. Due to the enhanced heat transfer and dissolution and wetting effect of the liquid low-melting-point high-temperature slag flow on the solid slag shell, as well as the possible formation of lower melting-point multi-element eutectic compounds, the thick slag shell will soon be melted through. In this way, the high-temperature flame moves along the closed loop, forming a liquid slag line, then low-melting-point mineral flux is added, and then the flame airflow blows it. The liquid slag line gradually moves along the closed loop. Finally, the shielded slag shell surrounded by the melted closed loop falls into the flowing molten slag below due to its own weight.

[0024] By selecting a closed loop with an appropriate area for the liquid slag melting through the cutting line, the size of the falling solid slag shell can be moderate. This allows it to be gradually heated to softening or even melting temperature by being encased and melted by the flowing slag. It can then smoothly pass through the downstream slag channel to complete its subsequent journey, preventing the downstream slag channel from being impacted and accumulated by too many large falling hardened slag shells, thus avoiding slag channel blockage. In addition, the appropriate size of the opening formed by the falling slag shell after the closed loop is melted through can also prevent excessive radiative heat dissipation from the flowing blast furnace slag below, which would affect the stability of the downstream granulation process and the improvement of waste heat recovery rate.

[0025] The beneficial effects of this invention are:

[0026] This invention uses a high-temperature flame combined with a low-melting-point mineral flux to melt the solidified slag shell. This can safely and efficiently break through the slag shell covering the blast furnace slag trench, exposing the active flowing blast furnace slag beneath the slag shell. This meets the technical requirement that the blast furnace slag trench slag temperature and flow detection device needs to see the active slag, and promotes the development of blast furnace slag waste heat recovery technology.

[0027] Because the blast furnace slag trough shell is broken using a non-mechanical method, it prevents the molten slag from splashing and injuring people or damaging property when mechanically poking the slag shell, thus avoiding safety accidents. At the same time, it does not have a harmful impact on the smooth flow of molten slag in the blast furnace slag trough, and can smoothly restore the normal operation of online detection devices such as molten slag temperature and flow rate measurement, ensuring the smooth progress of blast furnace molten slag waste heat recovery engineering technology. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments.

[0029] Example 1

[0030] A non-mechanical method for breaking the slag shell in blast furnace slag trenches involves placing a high-temperature flame heating gun above the slag trench. When slag shell formation is detected at a target point, affecting online slag temperature or flow rate measurement, the lower gun is ignited to directly heat the slag shell with an impact flame. The slag shell is heated using oxy-acetylene, oxyhydrogen, or oxygen-propane flames. Since the flame temperature of oxy-acetylene, oxyhydrogen, or oxygen-propane combustion reaches 2000–3000℃, after a certain period, the slag shell at the point of concentrated impact by the high-temperature flame will be melted through, especially in thinner slag shells. The high-temperature flame heating gun is then gradually moved along the melt-through opening, forming a closed loop along a preset closed path to liquid-cut the slag line. Simultaneously, low-melting-point mineral flux is continuously added to increase the melting depth. Ultimately, the slag shell obstructing the online slag temperature or flow rate measurement device falls off due to gravity, allowing the temperature or flow rate measuring instrument to see the slag surface, thus restoring normal operation.

[0031] Example 2

[0032] A non-mechanical method for breaking up the slag shell in blast furnace slag trenches involves using high-temperature flames such as oxy-acetylene, oxyhydrogen, or oxygen-propane flames to bake the slag shell when it becomes covered. When only small molten pools or pits form on the surface of the slag shell, but the molten pools do not penetrate the shell, indicating a thick slag shell, a low-melting-point mineral flux is added into the small molten pool or pit. Because the melting temperature of the low-melting-point mineral flux is only 900–1200℃, a larger and deeper liquid molten slag pool quickly forms. The high-temperature flame is then used to impact and reheat the slag pool. While pushing the high-temperature flame to melt and create a liquid cutting slag line, low-melting-point mineral flux is added. This allows the slag pool to form a moving closed loop liquid cutting slag line along a pre-set closed path, thereby completing the cutting of the thick slag shell. Finally, the slag shell covering the closed loop liquid cutting slag line falls into the high-temperature blast furnace slag below due to its own weight and is remelted. The slag shell obscuring the slag surface is removed, and the temperature or flow detection instruments can be observed normally and operate smoothly.

[0033] Example 3

[0034] A non-mechanical method for breaking the slag shell in blast furnace slag trenches involves first using a high-temperature flame to melt the crusted slag surface in the blast furnace slag trench to create a liquid cutting slag line. Then, a low-melting-point mineral flux is added to the liquid cutting slag line and swept and melted by a high-temperature flame. After the low-melting-point mineral flux melts quickly, it, together with the already melted slag shell and slag liquid, forms a high-temperature liquid slag pool. At this time, the high-temperature flame continuously impacts and disturbs the high-temperature liquid slag pool, causing its liquid surface to fluctuate back and forth, thus melting through the slag shell. This process is repeated along the closed loop of the liquid cutting slag line, where the high-temperature flame moves to form a liquid slag line, low-melting-point mineral flux is added, and the liquid slag line is blown by a high-temperature flame airflow. Finally, the slag shell surrounded by the melted closed loop of the liquid cutting slag line falls into the flowing blast furnace slag below due to its own weight, allowing temperature or flow monitoring instruments to be observed normally and operate smoothly.

[0035] In the above process, in order to enable the low-melting-point slag pool to melt through the slag shell more quickly, an inverted U-shaped heat insulation cover is set above the liquid cutting slag line pushed by the high-temperature flame heating gun. The heat insulation cover is made of refractory material anchored and cast on a thin steel plate. Each cover is roughly similar to a section of flue, allowing the high-temperature flame flue gas to pass through it and cover the pushing liquid cutting slag line to form a certain degree of high-temperature flame and high-temperature slag liquid radiation shielding, reducing the heat loss caused by high-temperature radiation, and better promoting the melting through of the slag shell on the closed-loop liquid cutting slag line.

Claims

1. A non-mechanical method for breaking the slag shell in blast furnace slag trenches, characterized in that, When a slag shell affecting observation is found to form in the target molten slag temperature measurement zone or flow detection zone in the blast furnace slag ditch, a high-temperature flame heating gun with a temperature ≥1500℃ is first used to melt a liquid cutting slag line on the crusted slag surface of the blast furnace slag ditch. Then, a low-melting-point mineral flux with a melting point of 900-1200℃ is added to the liquid cutting slag line. Then, while sweeping the liquid cutting slag line with a high-temperature flame heating gun to form a closed loop of liquid cutting slag line, a low-melting-point mineral flux is continuously added to it to increase its melting depth. Finally, the slag shell in the closed loop of liquid cutting slag line falls off, exposing the actively flowing blast furnace slag below, thus meeting the detection requirements of the blast furnace slag ditch molten slag temperature and flow detection device.

2. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1, characterized in that, First, a high-temperature flame is used to melt the crust on the slag surface of the blast furnace slag trench to form a liquid cutting slag line. Then, a low-melting-point mineral flux is added to the liquid cutting slag line and swept and melted by a high-temperature flame. After the low-melting-point mineral flux melts quickly, it, together with the already melted slag shell and slag liquid, forms a high-temperature liquid slag pool. At this time, the high-temperature flame continuously impacts and disturbs the high-temperature liquid slag pool, causing its liquid surface to fluctuate back and forth, so that the slag shell is melted through. This process is repeated along the closed loop of the liquid cutting slag line, where the high-temperature flame moves to form a liquid slag line, low-melting-point mineral flux is added again, and the liquid slag line is blown by the high-temperature flame airflow. Finally, the slag shell surrounded by the melted closed loop of the liquid cutting slag line falls into the flowing blast furnace slag below due to its own weight.

3. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1 or 2, characterized in that, An insulating cover that moves with the high-temperature flame is placed above the closed-loop liquid cutting slag line to shield the high-temperature flame and the high-temperature radiation of the liquid slag, thereby reducing heat loss and accelerating the melting and cutting speed.

4. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1 or 2, characterized in that, Low-melting-point mineral flux is added to the crusted slag surface within the closed-loop liquid cutting slag line.

5. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1, 2, or 4, characterized in that, The low-melting-point mineral flux is selected from fluorite powder, cryolite powder, or low-melting-point glass powder.

6. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1, 2, 3, or 4, characterized in that, The slag shell size within the closed-loop liquid cutting slag line is 1 / 30 to 1 / 5 of the width of the slag surface of the slag groove crust.

7. The method for non-mechanically breaking the slag shell in blast furnace slag trenches as described in claim 1 or 2, characterized in that, The high-temperature flame heating gun uses oxyacetylene, hydrogen-oxygen, or oxygen-propane, and the flame combustion temperature reaches 2000-3000℃.