This article describes the main measures to prevent electric furnace lining erosion, which mainly include three aspects.
Keywords: electric furnace lining; erosion; measures
Combining common furnace protection measures at home and abroad, the protection of slag hanging on the furnace lining is the preferred method. However, this method requires changing the furnace type and redesigning the water-cooled furnace wall, which is not easy to implement for the melting furnace of the pilot line that has been put into operation. If it is rebuilt, the cost will be higher. If it is optimized and transformed based on the existing furnace type, it will affect the function of the existing equipment and delay the trial production. Therefore, cooling the furnace lining to allow slagging is a mid- to long-term consideration. At present, the measures taken to prevent furnace lining erosion in the pilot line mainly include three aspects.
Prevent oxidation of metallized pellets and reduce melting point electric furnace smelting load
The raw material of the melting electric furnace is high-temperature metallized pellets produced in the rotary hearth furnace. The metallization rate of the pellets is ≥85%. It is called sponge iron because of its loose and porous structure. The temperature of metallized pellets coming out of the furnace is about 800°C, and the metal iron is highly active shortly after production. If no protective measures are taken, severe secondary oxidation will occur in high-temperature, high-porosity metallized pellets. The metallization rate decreases by 10% to 30%, the FeO content in the pellets increases, and the chemical erosion and physical erosion of the slag on the furnace lining is strengthened.
The metallization rate of the pellets is reduced, which increases the smelting load of the melting furnace. At the same time, more reducing agents are required, making it difficult to add materials. Using water to cool the metallized pellets will effectively prevent secondary oxidation of the pellets, but it will also lose a large amount of sensible heat of the pellets, especially when water enters the melting furnace, worsening the furnace condition, prolonging the smelting cycle, and reducing overall energy utilization. Efficiency decreases.
After repeated exploration and practice, the scientific researchers of the pilot line independently developed a protection method for high-temperature metallized pellets and designed a simple supporting device, which effectively prevented the secondary oxidation and adhesion of high-temperature metallized pellets during storage and transportation. . The sensible heat of the pellets is maintained, the load of the melting electric furnace is reduced, the smelting cycle is significantly shortened, the energy utilization efficiency is significantly improved, and the life of the furnace lining is relatively extended.
Control the smelting temperature and shorten the open arc smelting time
Multiple rounds of test results show that a better vanadium reduction rate can be obtained by adding appropriate reducing agents and controlling the iron tapping temperature reasonably. Therefore, if the tapping temperature is lowered on the original basis, the slag temperature will decrease accordingly. In addition, the tapping temperature is lowered, the smelting time is shortened, and the time for the titanium-containing furnace rod to soak the furnace wall is also shortened accordingly, which plays a certain protective role in the furnace lining.
Due to the particularity of metallized pellets, melting electric furnace smelting is different from ordinary electric arc furnace steelmaking and submerged arc furnace ore smelting, but is somewhere in between. Therefore, the power supply and feeding system are special. On the basis of experiments, a matching power supply and feeding system was developed based on power consumption and melting conditions to avoid waste of electrical energy and reduce radiation losses. At the same time, the feeding position was adjusted, and the material was added between the electrode and the furnace wall to protect the refractory material of the furnace wall.
Carry out thermal gunning repair on areas with serious corrosion of furnace lining
Adjustments to the power supply, feeding system and end-point control temperature have shortened the smelting cycle of the melting furnace to a certain extent, reduced the time for the open arc to radiate the furnace wall, reduced the immersion of the high-temperature titanium-containing furnace lining on the furnace lining, and delayed the erosion of refractory materials. Speed, the life of the furnace lining is extended by 8 to 10 heats.
Since the furnace lining erosion is not uniform, in order to extend the service life of the furnace lining, local spraying repair measures are taken to protect the furnace. However, titanium-containing slag is an important product of the pilot line. If its TiO2 grade is reduced, especially if the SiO2 impurity is high, the subsequent titanium extraction process from titanium-containing slag will be more difficult. Therefore, the type and injection amount of gunning materials need to be strictly controlled. The research team is currently studying the practicality of titanium gunning materials in order to protect the slag grade. At the same time, gunning is generally not carried out in the early stage of furnace service, or a thinner layer is sprayed depending on the situation; the amount of gunning is gradually increased in the later stage of furnace service. However, only the areas behind the electrodes and areas with severe slag and tap hole erosion will be sprayed.
Although the use of gunning materials has a certain impact on the grade of titanium-containing slag, comprehensive consideration has strong economic applicability. If the new gunning material is successfully developed and the impact on the grade of titanium slag is eliminated, the life of the furnace lining will be greatly extended.