Causes of Damage to Industrial Silicon Furnace Eyes

Causes of Damage to Industrial Silicon Furnace Eyes

As a key component of the furnace body and furnace cylinder of the industrial silicon submerged arc furnace, the industrial silicon furnace outlet eyes is carefully built with carbon bricks and is responsible for the smooth discharge of high-temperature silicon melt out of the furnace. A submerged arc furnace is usually equipped with five silicon outlet furnace eyes, and carbon bricks have been widely used in the lining of submerged arc furnaces due to their unique properties. 

In recent years, with the rapid development of ferroalloy production technology, the overall service life of the submerged arc furnace lining has been significantly improved, generally up to 5 to 8 years. 

However, the industrial silicon submerged arc furnace eye of the silicon outlet often becomes the short board in the service life of the furnace lining, and often damage occurs only 5 to 7 days after being put into use. Behind this phenomenon, the carbon bricks of the furnace eye gradually deform under the erosion of continuous high-temperature furnace gas, molten silicon water and high-temperature slag and mechanical scouring, forming an elliptical furnace eye, which leads to the expansion of the furnace eye cavity, making it extremely difficult to block the eye, and even causing problems such as eye running and flame spraying.

So, what is the main cause of furnace eye damage?

1. Oxidation erosion

The primary reason is oxidation erosion. The furnace eye of industrial silicon submerged arc furnace generally adopts carbonaceous material - carbon brick, which is favored for its high melting point, excellent thermal shock resistance and high temperature strength. 

However, carbon brick also has a significant disadvantage, that is, it is easy to oxidize. In a high temperature environment above 400℃, the circulating air flow can quickly oxidize the carbon brick; and when the temperature rises to above 600℃, CO2 and water vapor will have a strong oxidizing effect on the carbonaceous material. Since the carbon bricks at the silicon outlet are often exposed to the circulating air rich in oxygen, the oxidation rate is relatively fast. 

Among them, the oxidation rate of oxygen to carbon is particularly rapid, which is 2.5~3 times that of CO2. In the process of using oxygen to blow or burn through the silicon furnace eye, this oxidation reaction will become more intense. 

In addition, the spraying water operation during the maintenance of the furnace eye and the heavier water content in the mud ball blocking the eye will further aggravate the erosion of the furnace eye by water vapor.

2. Mechanical erosion

Another major reason is mechanical erosion. During the silicon outlet process, the high-temperature silicon melt will continuously scour the carbon bricks in the furnace eye, causing the furnace eye to gradually expand. 

Especially when the slag has high viscosity, poor fluidity, poor slag discharge or the furnace eye is difficult to open, when the slag rod is used to carry slag or tools such as oxygen tubes are used to open the eye, strong mechanical scouring will be caused to the furnace eye carbon bricks. 

At the same time, the rapid temperature changes (sudden cooling and heating) during silicon discharge and after plugging the eye will also cause serious damage to the furnace eye carbon bricks, causing them to peel off.

In addition, unreasonable current distribution in the industrial silicon submerged arc furnace is also one of the important reasons for the damage of the furnace eye carbon bricks. When the voltage gradient from the electrode to the furnace eye carbon brick is greater than the voltage gradient between the electrodes, the current will be diverted to the furnace eye carbon bricks, thereby increasing the temperature of this part. This temperature increase will accelerate the chemical erosion and mechanical scouring of the furnace eye carbon bricks by the slag, further shortening the service life of the furnace eye.