A method for repairing a high-temperature hot blast stove slag fusion erosion interface region

Abstract

The present application belongs to the technical field of hot blast stove repair for blast furnace ironmaking, and particularly relates to a method for repairing slag fusion erosion interface area of an aged hot blast stove, comprising the following contents: (1) repairing: 1. cleaning the interface; 2. brushing high-temperature silica brick mortar to the slag fusion erosion interface; 3. moderately blowing with a blower or naturally drying; 4. uniformly coating high-temperature silica brick mortar on the slag fusion interface and its extended area on the inner wall of the hot blast stove and compacting; 5. moderately blowing with a blower or naturally drying again to ensure drying of the second coating; 6. using gradient creep rate control precision stove baking method to bake the stove; (2) establishing a hot blast stove temperature and pressure state trend sensing system; (3) local reinforcement; (4) vertical strengthening; (5) configuring a prestressed buffer device. The method prevents damage to the refractory lining, prevents the refractory lining from falling off and cannot be timely maintained, and prevents damage to the furnace shell by optimizing the high-temperature silica brick mortar, extending the medium-temperature baking time, local reinforcement, prestressed buffering, and the temperature and pressure state trend sensing system.

Description

Technical Field

[0001] This invention belongs to the field of blast furnace ironmaking hot blast stove repair technology, and particularly relates to a method for compensating and repairing the interface area of ​​slag melting erosion in old hot blast stoves. Background Technology

[0002] With the rapid development of the metallurgical industry, large-scale, high-pressure, and high-temperature hot blast stoves have become the technological trend in ironmaking. At the same time, this has also increased the risk of high-temperature failures in hot blast stoves. Public data shows that in recent years, about 60% of large hot blast stoves in China have experienced failures such as high temperature and red-hot furnace shells, which is a major safety challenge facing the ironmaking industry.

[0003] Inside the hot blast stove, which has been in service for 20 years, the areas with operating temperatures consistently exceeding 900 degrees Celsius are classified as high-temperature working zones. These include the upper part of the regenerator, the dome area, and the hot blast outlet area. Due to factors such as the gas and high temperatures generated during long-term operation, the corresponding working surfaces have suffered damage, which is defined as the slag melting erosion interface area of ​​the aging hot blast stove. Approximately 81% of the hot blast stove structure inside this area is made of silica bricks. Over the extremely long period of production operation, cumulative damage has occurred, and the damage mechanism is as follows: (1) High-temperature chemical reaction erosion: Blast furnace gas contains impurities. Harmful impurities in high-temperature gas adhere to the surface of silica brick materials and undergo chemical reactions, resulting in changes in surface composition or the formation of low-melting-point compounds (such as silicates, aluminates, etc.). (2) Physical erosion: Hot air brings slag into the brick body through pores and cracks, causing the structure to become loose and peel off; (3) Cyclic thermal shock damage: The working mode of the hot blast stove is to burn the furnace, press, and blow air. The pressure changes cyclically, and the temperature ranges from 1000 degrees to 1400 degrees. It is also a process of energy conversion. Temperature fluctuations cause the brick to expand and contract, which exacerbates the expansion of surface cracks and peeling.

[0004] Problems such as damage and detachment of the refractory lining in the later stages of hot blast stove production cannot be maintained in time, leading to an increase in furnace shell temperature, thermal fatigue, and high-temperature creep, which causes damage to the furnace shell. Summary of the Invention

[0005] The purpose of this invention is to provide a method for compensating and repairing the interface area of ​​slag erosion in old hot blast furnaces, thereby solving the problem of furnace shell damage caused by increased furnace shell temperature, thermal fatigue, and high-temperature creep in the interface area of ​​slag erosion in old hot blast furnaces.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for compensating and repairing the interface area eroded by slag from an aged hot blast furnace includes the following: (a) Repair 1. Clean the interface and remove surface debris. For areas where the slag molten state depth is greater than 40 mm and there is missing brick lining causing furnace lining collapse, partially dismantle and rebuild. For areas where the slag molten interface depth is less than 40 mm, blow clean and confirm. 2. Use a brush to apply high-temperature silica brick mortar to the slag erosion interface, covering all cracked areas with a surface thickness of 1-2 mm. Then, use a brush to horizontally insert the mortar into the damaged area along the direction of the silica brick slag erosion crack, achieving deep repair and bonding of the high-temperature silica brick erosion damaged layer interface. The high-temperature silica brick mortar is a low-expansion silica mortar. 3. Use a hairdryer to blow air gently or let it air dry naturally to ensure the adhesion strength of the mud, for more than 24 hours; 4. After the base layer of fine-grained silica brick mortar has dried, apply a 5-8 mm thick layer of high-temperature silica brick mortar evenly to the slag-melting interface and its extended area of ​​1800-2000 mm on the inner wall of the hot blast stove by coating, and compact it; isolate the slag-melting surface and form a 3-5 mm protective layer on the outside of the working surface. The thermal conductivity of the silica brick mortar is about 3 W / (m·K), reducing the proportion of hot air transported to the outside; 5. Use a hairdryer to blow air gently again or let it air dry naturally to ensure the second coating is dry; 6. The precision furnace drying method with gradient creep rate control is adopted to dry the furnace for 52-60 days, and the furnace drying curve of silica mud is implemented to optimize the low-temperature bonding force of silica mud, effectively eliminating cracks and brick joint opening after long-term operation of silica bricks, and reducing the probability of hot air leakage.

[0007] (II) Establish a temperature and pressure situation perception system for hot blast stoves (III) Local reinforcement Strengthen and repair any cracks or dents in the hot blast stove shell, ensuring that the original strength is greater than 120%; use reinforced plates and distributed welding of reinforcing ribs to improve the load-bearing capacity of localized stress concentrations.

[0008] (iv) Three-dimensional reinforcement of latitude and longitude Three-dimensional reinforcement refers to the horizontal and vertical bidirectional reinforcement of the high-temperature zone of the entire hot blast stove shell to improve the overall structural load-bearing capacity of the hot blast stove shell. Three-dimensional reinforcement is mainly divided into two types: longitudinal reinforcement and latitudinal reinforcement.

[0009] (v) Configure prestressed buffer devices Prestressed buffer devices are installed on the exterior of the furnace shell at locations with micro-textures and high stress points inside the furnace shell. When the parameters of the stress control system change beyond the warning level, the stress buffer device applies appropriate stress as an emergency measure to reduce the stress value of the furnace shell, improve the safe load-bearing capacity of the hot blast stove shell, and extend the furnace service life.

[0010] Preferably, the low-expansion silica mortar in step (a) 2 comprises waste silica brick powder and silica micro powder, with waste silica brick powder accounting for 20-30%, the main phase being phosphogypsum phase, and a particle size ≤0. During the furnace drying process at 200-300℃, the 0.5mm micro-expansion silica slurry, a key component of the refractory slurry, undergoes complete crystal transformation due to the strictly controlled high-temperature calcination of the waste silica bricks. The main crystalline phase is phosphothrene, exhibiting good volume stability. The transformation of quartz to tricrite in the silica slurry results in a volume expansion rate of less than 0.5%, ensuring that the volume expansion rate of the slurry used for bonding the old silica bricks in the molten state is small. This prevents damage to the original gaps during the quartz-to-tricrite transformation, reduces post-firing shrinkage, ensures the repair of the silica brick slag erosion interface, and eliminates the possibility of widening the 10-30mm cracks on the original silica brick surface. The ultra-fine silica powder has good dispersibility and suspends the refractory slurry, improving its workability and preventing sedimentation. Furthermore, the extremely high silica content increases the silica content in the refractory slurry. In the medium- and high-temperature stages, it can also promote sintering and improve the slurry's bonding strength. The extremely fine-particle, low-expansion silica mortar fully penetrates to the depth of the slag-treated surface silica brick, completely filling the cracks in the penetration layer and effectively bonding with the unaffected silica brick layer, thus repairing the damaged surface layer.

[0011] The crystal transformation of silica bricks in hot blast stoves mainly involves the transformation from quartz to tridymite and cristobalite. This process is accompanied by significant volume changes, directly affecting material properties and the operational safety of the hot blast stove. Numerous fissures exist at the slag-molten erosion interface; if the repair slurry expands significantly, it may crack the original silica bricks, causing negative consequences. The thermal stability of siliceous slurry depends on the content of tricrite in the slurry. During the heating process of the hot blast stove, the volume change of quartz phase transformation is very large, causing cracking of the slurry or silica bricks. The core of micro-expansion siliceous slurry is to control the volume change during the phase transformation process, so that quartz is transformed into a volume-stable tricrite phase at high temperature. The tricrite phase has an interlocking structure, which is also beneficial to the high-temperature strength of the slurry.

[0012] Preferably, the gradient creep rate control precision furnace drying method in step (a) 6 is designed for drying aging hot blast stoves to repair the silica brick interface. During the furnace drying process, the low-to-medium temperature gradient of the silica brick is controlled at 178-272℃, which is the internal expansion temperature zone of the silica brick. During this stage, the quartz below, i.e., the transformation between β-cristobalite and α-cristobalite variants, undergoes the largest volume change. By controlling the temperature rate and uniformly extending the heating time, the temperature non-uniformity in the thickness direction of the silica brick in the furnace is reduced, eliminating the damage to the lining caused by thermal stress concentration due to expansion. This is beneficial for the bonding and integration of the silica brick slag erosion interface and the new compensation insulation layer. The furnace drying curve after the repair of the aging hot blast stove is determined by the performance of the silica brick, which is the main functional material in the high-temperature zone. Secondly, the low-temperature instability of silica brick is the most difficult to control among all refractory furnace drying curves. The furnace drying curve of the aging hot blast stove is divided into 6 main temperature gradient controls: 1) Low temperature gradient control: room temperature - 178℃: room temperature - 100℃ range. The purpose of this stage is to evaporate the physical water adhering to the hot air furnace spray coating and the inner lining slurry refractory material, and to transform the γ-phosphorus quartz inside the silica brick into β-phosphorus quartz and then into α-phosphorus quartz at 117-163℃. 2) Low-to-medium temperature gradient control (178-272℃) targets the internal expansion temperature zone of the silica bricks. During this stage, the quartz at the bottom undergoes the transformation from β-cristobalite to α-cristobalite, resulting in the largest volume change. By controlling the temperature rate, ensuring uniformity, and extending the heating time, temperature unevenness along the thickness direction of the silica bricks in the furnace is reduced, eliminating the damage to the lining caused by thermal stress concentration due to expansion. 3) Controlling the temperature at 272℃ for 48 hours helps increase the strength of the mud in the gaps of the slag melting damage area in the high temperature zone, restores the adhesion between the surface coating layer of the high temperature silica brick and the slag melting damage area in the high temperature zone, and achieves high adhesion of the working layer on the surface of the silica brick. 4) Medium temperature gradient control 272℃-398℃ to homogenize the transformation of β-cristobalite to α-quartz inside the silica brick; 5) Medium and high temperature gradient control: The heating range is 398-573℃, and the transformation of β-cristobalite to α-quartz inside the silica brick is completed at 573℃; 6) The high temperature gradient control range of 573℃-1149℃ allows the possible β-quartz in the silica bricks to transform into α-quartz, ensuring that SiO2 completes its crystal transformation. The water of crystallization in the silica bricks further precipitates from the outer side of the hot blast furnace, which is far from the high temperature surface.

[0013] Preferably, the specific content of (ii) is to establish a hot blast stove temperature monitoring, stress monitoring, and hot blast pressure interlocking technology system on the hot blast stove: 1. First, according to the parameters, set up monitoring points of the hot blast stove operation temperature-stress-pressure situation perception system in the high temperature and high stress area of ​​the hot blast stove shell to achieve the goal of real-time, unmanned, high-precision, and forward-looking protection intelligent hot blast stove equipment maintenance assistance; 2. Establish a comprehensive intelligent temperature and stress data analysis system for the entire hot blast stove area. The intelligent data analysis guides the real-time stress and temperature trend data of the hot blast stove production. The data acquisition system is set up in key parts of the hot blast stove shell. After receiving information remotely, the analysis system processes it. If the data trend tends to exceed the threshold, the system will notify the blast furnace expert system to carry out a series of process operations such as cooling the furnace shell, adjusting the air supply pressure, controlling the air temperature, and reducing the air volume to keep it within a reasonable range. 3. The temperature and stress data analysis system is synchronously interlocked with the hot blast stove air supply pressure and is included in the blast furnace safety system; by setting up temperature, pressure, stress and deformation monitoring systems, the parameters of stress and deformation in key parts of the hot blast stove can be grasped in a timely manner, and the goal of low stress in long-cycle hot blast stove system can be truly achieved.

[0014] Preferably, the (iii) local reinforcement also includes the following: Based on the measurement and control parameters and flaw detection records, identify the high temperature and high stress area of ​​the hot blast stove shell. According to the division of the shell area, evenly install the meridional (horizontal) ring steel bars around it, with a spacing of 900-1000 mm. Open the V-shaped bevel at the interface and weld with equal strength. Evenly distribute and install the zonal (vertical) steel bars, with a spacing of 18° per bar. When assembling and connecting, be sure to align with the surface and side of the reinforcing bar as the reference. If the misalignment is too large or the verticality is not aligned during assembly, a certain stress will be generated after welding. Perform appropriate stress relief treatment. While installing the zonal (vertical) steel bars, install the meridional (horizontal) ring hoops from bottom to top. Place the vertical bar joints as low as possible below the ring hoop position to avoid the original weld seam of the furnace shell. The installation sequence is: bottom ring hoop --- longitudinal reinforcing vertical bar --- middle ring hoop --- top ring hoop.

[0015] Preferably, in part (iv), the warp reinforcement is made of steel plate by forming and is horizontally fixed to the hot blast stove shell by welding; the weft reinforcement is achieved by welding steel bars or structural steel and vertically fixing them to the high-temperature area of ​​the hot blast stove, effectively improving the load-bearing capacity of the hot blast stove shell. At the same time, the warp and weft three-dimensional reinforcement prevents cracks in the hot blast stove to a certain extent and extends the service life of the hot blast stove.

[0016] Preferably, there are two types of prestress buffer devices in (v): a bolt pre-tightening device and a flexible steel wire pre-tightening device. When a stress warning is issued, the stress in the area is dispersed to a smaller part by pre-tightening with bolts or flexible steel wires to achieve buffering.

[0017] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The micro-expansion silica slurry uses waste silica brick powder and silica micro powder. The silica micro powder has an ultra-fine particle size and good dispersibility. It plays a role in suspending the refractory slurry in the silica refractory slurry, making the refractory slurry more workable and preventing sedimentation. In addition, due to the ultra-high silica content, it increases the silica content in the silica refractory slurry. In the medium and high temperature stage, it also promotes sintering, improves the slurry bonding strength, organically integrates with the original silica brick slag surface and cracks, and forms a new high temperature working surface, preventing damage to the refractory lining and extending the working layer life of the high temperature area of ​​the old hot blast stove. (2) By extending the medium-temperature baking time, the infiltration layer in the interface area of ​​the silica brick slag melting and damage is sintered with the silica brick unchanging layer into one, the silica brick working surface and the newly added protective layer are strengthened to enhance the bonding, improve the high-temperature performance of the high-temperature working surface layer, and avoid furnace shell temperature rise, thermal fatigue and high-temperature creep causing furnace shell damage. (3) By strengthening the local stress concentration, the bearing capacity of the local stress concentration is effectively improved. Combined with the three-dimensional reinforcement, the high temperature zone of the hot blast stove shell is strengthened horizontally and vertically to improve the overall structural bearing capacity of the hot blast stove shell. The prestressed buffer device is used as an emergency measure to apply appropriate stress, reduce the stress value of the furnace shell, prevent the furnace shell from being damaged, improve the safe bearing capacity of the hot blast stove shell, and extend the service life of the furnace. (4) Establish an intelligent temperature and pressure sensing system and hot air pressure interlock control to realize a system for comprehensive control of hot air furnace operating parameters, eliminate unsafe factors of excessive stress in hot air furnace, prevent the failure to maintain the refractory lining in time, which can lead to increased furnace shell temperature, thermal fatigue and high temperature creep damage to the furnace shell, and promote the intelligent, safe and heat-insulating technology upgrade of hot air furnace equipment system. Detailed Implementation

[0018] The technical solution of the present invention will be further described below with reference to the embodiments.

[0019] The method of this invention was applied in the 4350m section of Taiyuan Iron & Steel Plant in October 2023. 3 The specific implementation plan for application in blast furnaces is as follows: (I) Repair of the slag erosion interface inside the hot blast stove 1. Clean the interface and remove surface debris. For areas where the slag-molten state depth is greater than 40 mm and there is missing brick lining causing furnace lining collapse, partially dismantle and rebuild. For areas where the slag-molten interface depth is less than 40 mm, blow clean and confirm.

[0020] 2. Apply a 30% water-based micro-expanding silica slurry to the slag-erosion interface using a brush. Fill the cracks in the silica bricks with a depth of 10-40 mm using a diffusion coating method. Plug the slurry horizontally into the cracks on the slag-eroded surface of the silica bricks, ensuring no voids. Apply a slurry layer approximately 1 mm thick for the initial repair of the silica brick surface. Ensure the slurry solidifies to bond and fuse the cracks in the silica bricks. After drying and curing, apply a second surface coating with a thickness ≥ 5 mm. The applied material, micro-expanding silica slurry, contains 20% waste silica brick powder. The main phase is phosphogypsum, with a particle size of 0.5 mm. After strict temperature-controlled high-temperature calcination, the crystal transformation is complete, and the main crystalline phase is phosphogypsum, exhibiting good volume stability and high-temperature performance. The micro-expanding silica slurry also includes silica micropowder, with ultra-fine particle size and good dispersibility. This suspends the refractory slurry, improving its workability and preventing sedimentation.

[0021] 3. For expansion joints in the hot blast stove with a width greater than 5 mm, use 1400-degree fiber cotton to fill them with a filling depth greater than 200 mm to meet the expansion and deformation requirements of the lining during the heating period of the hot blast stove; if the brick joints of the inner insulation layer of the working layer of the hot blast stove brick lining are pulled apart (the original design included mortar), use micro-expanding silica mortar to squeeze in from the inside to eliminate irregular gaps caused by hot air intrusion, with an effective pressure of less than 2 kg and an penetration amount of 1.2 times the volume of the gap tested in practice.

[0022] 4. Allow to air dry for 25 hours to ensure the surface is dry and cured.

[0023] 5. After the base layer of fine-grained silica brick mortar has dried, apply a 5 mm thick layer of micro-expansion silica slurry evenly to the slag-melting interface and its extended 2000 mm area on the inner wall of the hot blast stove. Compact the slag-melting surface with a tool to isolate it, forming a protective layer of about 5 mm inside the silica brick working surface. Allow it to dry and cure naturally for another 72 hours to ensure the secondary coating is dry. By adding a protective layer of silica brick, the heat insulation performance is improved. During the next 3-5 years, it will replace the original silica brick slag-melting surface for high-temperature operation, reducing the surface temperature of the furnace shell in the area by about 30 degrees Celsius. At the same time, it effectively eliminates the phenomenon of brick joints opening after long-term operation of silica bricks, reducing the probability of hot air leakage.

[0024] 6. Gradient creep rate control precision oven drying method: Oven drying for 52 days, low temperature gradient 40-178℃ control for 456 hours, heating rate 8℃ / day, low-medium temperature gradient 178-272℃ control for 259 hours, heating rate 10℃ / day, medium temperature constant temperature 272℃ control for 48 hours, medium temperature gradient 272-398℃ control for 168 hours, heating rate 14℃ / day, medium-high temperature gradient 398-573℃ control for 120 hours, heating rate 35℃ / day, high temperature gradient 573-1149℃ control for 192 hours, heating rate 72℃ / day, for a total of 1243 hours, then entering the cooling stage, ready for delivery to production. The temperature curve of this precision furnace drying method helps to increase the strength of the mud in the gaps of the slag melting damage area in the high temperature zone, restore the adhesion between the surface coating layer of the high temperature silica brick and the slag melting damage area in the high temperature zone, and achieve high adhesion of the working layer on the surface of silica brick in the range of 1400 degrees. From the analysis of the surface compensation mechanism of silica brick damaged at the slag melting interface, this method can extend the service life of silica bricks in this area by more than 10 years.

[0025] (II) Establish a temperature and pressure situation perception system for hot blast stoves Establish a technical system for hot blast stove temperature monitoring, stress monitoring, and hot blast pressure interlocking:

[0026] 1. First, according to the parameters, set up monitoring points of the hot blast stove operation temperature-stress-pressure situation perception system in the high temperature and high stress area of ​​the hot blast stove shell to achieve the goal of real-time, unmanned, high-precision, and forward-looking protection intelligent hot blast stove equipment maintenance assistance; 2. Establish a comprehensive intelligent temperature and stress data analysis system for the entire hot blast stove area. The intelligent data analysis guides the real-time stress and temperature trend data of the hot blast stove production. The data acquisition system is set up in key parts of the hot blast stove shell. After receiving information remotely, the analysis system processes it. If the data trend tends to exceed the threshold, the system will notify the blast furnace expert system to carry out a series of process operations such as cooling the furnace shell, adjusting the air supply pressure, controlling the air temperature, and reducing the air volume to keep it within a reasonable range. 3. The temperature and stress data analysis system is synchronously interlocked with the hot blast stove's air supply pressure and integrated into the blast furnace safety system. By setting up temperature, pressure, stress, and deformation monitoring systems, the system can promptly grasp the stress and deformation parameters of key parts of the hot blast stove, truly achieving the goal of low stress in the long-cycle hot blast stove system. Theoretical basis: The stress and temperature of the hot blast stove shell are safety indicators for the stable operation of the hot blast stove, related to internal hot blast pressure, shell structural stability, and lining integrity. When these data exceed thresholds, a series of process operations such as cooling, adjusting air supply pressure, controlling blast temperature, and reducing airflow must be implemented to control them within a reasonable range. This system enables remote intelligent safety control and monitoring of the blast furnace via mechanical parameters. Based on the mechanical, thermal, and ironmaking process theories of the hot blast stove body, and by optimizing the configuration of mechanical and thermal sensors, a sensor network and a field distributed data acquisition system are constructed. Based on mathematical models of temperature, stress state, fatigue life, and load monitoring, automatic early warning and alarm are achieved through simulation analysis. This enables the control and monitoring of the stress state of the blast furnace structure. It not only allows for real-time monitoring of the safety status of the hot blast stove shell but also timely risk warnings, adjustment of production operation pressure, and a significant reduction in the probability of local anomalies in the hot blast stove shell. It is also a key means to improve the safety protection of the hot blast stove.

[0027] (III) Local reinforcement of hot blast stove shell For potential cracks or dents in the hot blast stove shell, reinforcement and repair should be carried out, with the principle being that the strength of the original area is greater than 120%. Reinforcement with overlay plates and distributed welding of supporting stiffeners should be used to improve the load-bearing capacity of localized stress concentrations. It is important to note that the effect of local reinforcement must be fully assessed before welding, and sufficient pretreatment should be performed to ensure that the strength of the welded joint is not weaker than that of the original material.

[0028] (iv) Three-dimensional reinforcement of latitude and longitude Three-dimensional reinforcement refers to the horizontal and vertical bidirectional reinforcement of the high-temperature zone of the entire hot blast stove shell to improve the overall structural load-bearing capacity of the hot blast stove shell. Three-dimensional reinforcement mainly includes two methods: longitudinal reinforcement and longitudinal reinforcement. Based on the measurement and control parameters and flaw detection records, the high-temperature and high-stress areas of the hot blast stove shell are identified. According to the division of the shell area, longitudinal (horizontal) ring steel bars are evenly installed around the perimeter, with a spacing of 900 mm. V-shaped bevels are opened at the joints, and equal strength welding is performed. Lateral (vertical) steel bars are evenly distributed and installed, with a spacing of 18° per bar. When assembling and connecting, it is necessary to align the reinforcing bar surface and side as a reference. If the misalignment is too large or the verticality is not aligned during assembly, a certain stress will be generated after welding. Appropriate stress relief treatment should be performed. While installing the longitudinal (vertical) steel bars, the longitudinal (horizontal) ring hoops are installed sequentially from bottom to top. The vertical bar joints should be placed below the ring hoop position as much as possible to avoid the original weld seams of the furnace shell. The installation sequence is: bottom ring hoop --- longitudinal reinforcing vertical bar --- middle ring hoop --- top ring hoop.

[0029] (v) Configure prestressed buffer devices The furnace shell has micro-textures inside, and a prestressed buffer device is installed on the outside of the furnace shell at the location of the high stress point. The pre-tightening is adjusted appropriately to disperse the stress in this area to the surrounding area until the stress value is lower than the control standard.

[0030] The 4350m³ blast furnace at Taiyuan Iron & Steel Plant was put into operation in October 2006. In 2023, the method described in this embodiment was used to gradually repair the four hot blast stoves. The median temperature of the original high-temperature part was 202 degrees Celsius. After the renovation and maintenance, the median temperature was 176 degrees Celsius. The heat loss of the hot blast stoves was reduced by about 13% after the upgrade.

[0031] Based on the actual temperature data after 28 months of operation of the modified hot blast stove, no high-temperature points appeared, demonstrating good low-carbon and energy-saving effects. The stress test data was reduced by 23%, improving the structural safety factor of the hot blast stove.

Claims

1. A method for compensating and repairing the interface area eroded by slag in an aged hot blast furnace, characterized by comprising the following: (a) Repair 1. Clean the interface and remove surface debris. For areas where the slag molten state depth is greater than 40 mm and there is missing brick lining causing furnace lining collapse, partially dismantle and rebuild. For areas where the slag molten interface depth is less than 40 mm, blow clean and confirm.

2. Use a brush to apply high-temperature silica brick mortar to the slag melting erosion interface, covering all the cracked areas with a surface thickness of 1-2 mm. Then, use a brush to horizontally insert the mortar into the damaged area along the direction of the silica brick slag melting crack. The high-temperature silica brick mortar is a low-expansion silica mortar.

3. Use a hairdryer to blow dry gently or let it air dry for more than 24 hours; 4. After the base layer of fine-grained silica brick mortar has dried, apply a 5-8 mm thick layer of high-temperature silica brick mortar evenly to the slag-melting interface and its extended area of ​​1800-2000 mm on the inner wall of the hot blast stove by coating, and compact it; isolate the slag-melting surface and form a 3-5 mm protective layer on the outside of the working surface. The thermal conductivity of the silica brick mortar is about 3 W / (m·K), reducing the proportion of hot air transported to the outside; 5. Use a hairdryer to blow air gently again or let it air dry naturally to ensure the second coating is dry; 6. The gradient creep rate control precision drying method is adopted to dry the furnace for 52-60 days, and the silica slurry drying curve is implemented to optimize the low-temperature bonding force of the silica slurry, effectively eliminating cracks and brick joint opening after long-term operation of silica bricks, and reducing the probability of hot air leakage. (II) Establish a temperature and pressure situation perception system for hot blast stoves (III) Local reinforcement Strengthen and repair any cracks or dents in the hot blast stove shell, ensuring that the original strength is greater than 120%; use reinforced plates and distributed welding of reinforcing ribs to improve the load-bearing capacity of localized stress concentrations. (iv) Three-dimensional reinforcement of latitude and longitude Three-dimensional reinforcement refers to the horizontal and vertical bidirectional reinforcement of the high-temperature zone of the entire hot blast stove shell. Three-dimensional reinforcement is mainly divided into two types: longitudinal reinforcement and latitudinal reinforcement. (v) Configure prestressed buffer devices A prestressed buffer device is installed on the outside of the furnace shell at the location of micro-textures and high stress points inside the furnace shell. As an emergency measure, the stress buffer device applies appropriate stress when the parameters of the stress control system change beyond the warning level.

2. The method for compensating and repairing the interface area of ​​slag erosion in an old hot blast furnace according to claim 1, characterized in that, The low-expansion silica slurry in (a) 2 includes waste silica brick powder and silica micro powder. The waste silica brick powder accounts for 20-30%, and the main phase is phosphogypsum phase with a particle size ≤0.5mm. During the furnace baking at 200~300℃, the waste silica brick in the important component undergoes complete crystal transformation due to the strictly controlled high-temperature calcination. The main crystal phase is phosphogypsum phase, and the quartz in the silica slurry transforms into triccite, with a volume expansion rate of less than 0.5%.

3. The method for compensating and repairing the interface area of ​​slag erosion in an old hot blast furnace according to claim 1, characterized in that, The gradient creep rate control precision furnace drying method in section (I) 6 is formulated for drying aging hot blast stoves to repair the interface of silica bricks. During the furnace drying process, the low-to-medium temperature gradient of the silica bricks is controlled at 178-272℃, which is the internal expansion temperature zone of the silica bricks. During this stage, the volume change of the quartz below, i.e., the transformation between β-cristobalite and α-cristobalite variants, is the largest. The furnace drying curve after the repair of aging hot blast stoves is determined by the performance of silica bricks, which are the main functional materials in the high-temperature zone. Secondly, the low-temperature instability of silica bricks is the most difficult to control among all refractory furnace drying curves. The furnace drying curve of aging hot blast stoves is divided into 6 main temperature gradient controls: 1) Low temperature gradient control: room temperature - 178℃: room temperature - 100℃ range. The purpose of this stage is to evaporate the physical water adhering to the hot air furnace spray coating and the inner lining slurry refractory material, and to transform the γ-phosphorus quartz inside the silica brick into β-phosphorus quartz and then into α-phosphorus quartz at 117-163℃. 2) Low-to-medium temperature gradient control (178-272℃) targets the internal expansion temperature zone of the silica bricks. During this stage, the quartz at the bottom undergoes the transformation from β-cristobalite to α-cristobalite, resulting in the largest volume change. By controlling the temperature rate, ensuring uniformity, and extending the heating time, temperature unevenness along the thickness direction of the silica bricks in the furnace is reduced, eliminating the damage to the lining caused by thermal stress concentration due to expansion. 3) Controlling the temperature at 272℃ for 48 hours helps increase the strength of the mud in the gaps of the slag melting damage area in the high temperature zone, restores the adhesion between the surface coating layer of the high temperature silica brick and the slag melting damage area in the high temperature zone, and achieves high adhesion of the working layer on the surface of the silica brick. 4) Medium temperature gradient control 272℃-398℃ to homogenize the transformation of β-cristobalite to α-quartz inside the silica brick; 5) Medium and high temperature gradient control: The heating range is 398-573℃, and the transformation of β-cristobalite to α-quartz inside the silica brick is completed at 573℃; 6) The high temperature gradient control range of 573℃-1149℃ allows the possible β-quartz in the silica bricks to transform into α-quartz, ensuring that SiO2 completes its crystal transformation. The water of crystallization in the silica bricks further precipitates from the outer side of the hot blast furnace, which is far from the high temperature surface.

4. The method for compensating and repairing the interface area of ​​slag erosion in an old hot blast furnace according to claim 1, characterized in that, The specific content of (ii) is to establish a hot blast stove temperature monitoring, stress monitoring and hot blast pressure interlocking technology system:

1. First, according to the parameters, set up monitoring points of the hot blast stove operation temperature-stress-pressure situation perception system in the high temperature and high stress area of ​​the hot blast stove shell to achieve the goal of real-time, unmanned, high-precision, and forward-looking protection intelligent hot blast stove equipment maintenance assistance; 2. Establish a comprehensive intelligent temperature and stress data analysis system for the entire hot blast stove area. The intelligent data analysis guides the real-time stress and temperature trend data of the hot blast stove production. The data acquisition system is set up in key parts of the hot blast stove shell. After receiving information remotely, the analysis system processes it. If the data trend tends to exceed the threshold, the system will notify the blast furnace expert system to carry out a series of process operations such as cooling the furnace shell, adjusting the air supply pressure, controlling the air temperature, and reducing the air volume to keep it within a reasonable range.

3. The temperature and stress data analysis system is synchronously interlocked with the hot blast stove air supply pressure and is included in the blast furnace safety system; by setting up temperature, pressure, stress and deformation monitoring systems, the parameters of stress and deformation in key parts of the hot blast stove can be grasped in a timely manner, and the goal of low stress in long-cycle hot blast stove system can be truly achieved.

5. The method for compensating and repairing the interface area of ​​slag erosion in an old hot blast furnace according to claim 1, characterized in that, The (iii) local reinforcement also includes the following: Based on the measurement and control parameters and flaw detection records, identify the high temperature and high stress area of ​​the hot blast stove shell. According to the area division of the furnace shell, evenly install the meridional (horizontal) ring steel bars around it, with a spacing of 900-1000 mm. Open the V-shaped bevel at the interface and weld with equal strength. Evenly distribute and install the zonal (vertical) steel bars, with a spacing of 18° per bar. When assembling and connecting, be sure to align with the surface and side of the reinforcing bar as the reference. If the misalignment is too large or the verticality is not aligned during assembly, a certain stress will be generated after welding. Perform appropriate stress relief treatment. While installing the zonal (vertical) steel bars, install the meridional (horizontal) ring hoops from bottom to top. Place the vertical bar joints as low as possible below the ring hoop position to avoid the original weld seam of the furnace shell. The installation sequence is: bottom ring hoop --- longitudinal reinforcing vertical bar --- middle ring hoop --- top ring hoop.

6. The method for compensating and repairing the interface area eroded by slag in an old hot blast furnace according to claim 1, characterized in that, In part (iv), the longitudinal reinforcement is made of steel plate by forming and is horizontally fixed to the hot blast stove shell by welding; the latitudinal reinforcement is achieved by welding steel bars or structural steel and vertically fixing them to the high-temperature area of ​​the hot blast stove.

7. The method for compensating and repairing the interface area of ​​slag erosion in an old hot blast furnace according to claim 1, characterized in that, There are two types of prestress buffer devices in (v): bolt pre-tightening device and flexible steel wire pre-tightening device. When stress warning is issued, the stress in the area is dispersed to a smaller part by pre-tightening with bolts or flexible steel wire to achieve buffering.