How to prevent a burn-through accident of hearth bottom?
The condition of the hearth bottom is an important factor in the life of the first generation of a blast furnace. The accident of burn-through of hearth bottom will cause great danger to the production and operation personnel, and even cause heavy casualties to prevent the occurrence–steelmaking technology
There are many causes of burn through, mainly:
- the designed hearth bottom structure is not reasonable, the used refractory material is inferior, the construction quality is not good, etc.;
- the unreasonable cooling system in production, unstable or high water temperature difference for a long time, especially in areas with poor water quality, scaling of water pipes affects cooling;
- the raw material contains lead which causes great damage to the bottom hearth (accidents in July 1989 and March 1997 of no. 4 furnace of lian gang) and alkali metals (accidents in June 1980 of no. 4 furnaces of Kun gang);
- the furnace condition is not good, the hearth system often out of view accumulation, so the frequent use of fluorite washing furnace, resulting in serious erosion of the hearth;
- the iron mouth is too shallow for a long time (Anshan steel no. 9 furnace accident in August 1950), the iron mouth centerline is wrong (Anshan steel no. 3 furnace accident in September 1975), the operation and maintenance are improper
- when there is an omen, the measures taken are not effective.
Burn through the main signs are:
- the temperature difference of water or the heat flow strength of the cooling wall of the hearth exceeds the specified value or the water is cut off;
- the brick lining in some local areas of the hearth is extremely thin, and the furnace shell is flushed;
- the bottom of the furnace is not normally cooled, the air-cooled tube is extremely red during air cooling, and local areas emit gas;
- abnormal iron production, the amount of iron increased after the slag, even see the next slag, after the iron, each iron loss amount more.
- although the furnace with titanium material has been used, the effect has not been seen due to insufficient dosage.
According to the causes of burn through, the corresponding targeted measures shall be taken to prevent it. Preventive measures are as follows:
- adopt good and reasonable hearth bottom structure, such as the hearth whole pouring + small micro-porous carbon brick structure, etc., and select high-quality refractory materials suitable for hearth bottom working conditions, and carefully build the furnace;
- try not to use lead-bearing charge, limit the alkali load of the human furnace (less than 3kg/t), use slag to discharge alkali when necessary;
- carefully operate to prevent the accumulation of hearth, in order to avoid washing furnace, especially in the middle and later furnace should avoid using fluorite washing furnace;
- grasp the operation in front of the furnace, maintain the normal state of the iron mouth, and release all the slag iron; To control the speed of molten iron, so as to avoid excessive speed, molten iron wash hearth wall;
- pay close attention to the working status of the cooler, strengthen the scientific management of the cooling equipment, take decisive measures to restore it to normal when the water temperature difference and heat flow intensity exceed the normal, such as changing the high-pressure water cooling, changing the single continuous cooling, cleaning the cooler, etc.;
- the use of material containing Ti to protect the furnace, in order to protect the furnace effectively, the amount of material containing Ti to ensure that the molten iron content [Ti] reached 0.08% ~ 0.10%, if the situation is serious, [Ti] can be increased to 0.15%, or even in a short time to 0.2% in order to rescue emergency, in the water temperature difference to fall, then back;
- when the heat flow intensity continues to rise, the wind must stop plugging the wind outlet in the area with the high-temperature difference between water and air, reduce the pressure and stop using the nearby slag mouth, if the temperature is still higher than the specified limit to stop cooling furnace, in After the temperature difference of water drops to the normal value, the cast pig iron is smelted with low pressure and low smelting strength.-steelmaking technology
A reasonable configuration of the hearth structure is the key to ensure the longevity of the blast furnace. Huaxi technology combined the TRE, Beijing university of science and technology, the development of the fourth generation of composite new hearth structure (carbon brick + hearth integral pouring + tuyere, iron casting), enhance the structural integrity and bonding strength of the hearth, and effective to prevent the hot metal or alkali metal penetration, with slag resistance, corrosion resistance, scouring resistance, oxidation resistance, such as the excellent performance, to avoid the tuyere upward, iron mouth at the gas fire, splash phenomenon.
The hearth structure can make the hearth more stable, shorten the construction time, reduce the maintenance times, extend the service life of the blast furnace, and produce more considerable economic benefits.-steelmaking technology