There are many reasons for the damage of blast furnace tuyere. Generally, there are 3 kinds of molten iron melting loss, wear and crack.
Melting loss of molten iron.
Since the front end of the tuyere extends into the furnace cylinder, the molten iron contacts the tuyere sleeve when the furnace cylinder works fluctuates, the heat flow increases sharply in a very short time, the heat transfer is blocked, and the iron melts copper. When high-temperature molten iron sticks to the tuyere sleeve, the strong heat flow causes the water on the inner wall surface of the tuyere to vaporize into tiny steam bubbles and form a steam film, which is close to the inner wall surface. This phenomenon is called film boiling. The steam film close to the surface of the inner wall isolates the heat exchange between water and the inner wall. Water cannot take the heat away. The temperature of the tuyere wall rises sharply. When the melting temperature of copper exceeds 1083 *, copper is melted, resulting in melting loss of the tuyere.
Wear.
It has two aspects, namely, the inner side of the tuyere sleeve is worn by the jet of coal powder and the outer side is worn by the furnace charge in the furnace cylinder, especially the circulating coke. The wear of burden and coke is easy to occur when the furnace cylinder is not working well, because when the blast furnace is in normal production, the front end of the tuyere extending into the furnace cylinder will form slag skin protection.
Cracking.
It is mainly due to the large temperature difference between the inside and outside of the tuyere wall and the large pressure difference (air pressure and cooling water pressure difference), and this temperature difference and pressure difference are often changed, which cause thermal fatigue and mechanical fatigue to the tuyere. In addition, defects in tuyere material and manufacturing process (casting bubbles, micropores, welding not meeting requirements, etc.) will cause cracks in the tuyere, which should be improved from tuyere material and manufacturing process.
