Industrial Silicon Furnace: Carbon Brick Furnace Eye Repair Guide

Introduction

An industrial silicon furnace, a type of submerged arc furnace, is primarily utilized for smelting industrial silicon solutions. Among all components of the industrial silicon furnace, the furnace eye is the most vulnerable part. It is highly susceptible to erosion from high - temperature slag and silicon solutions, leading to relatively rapid damage. Currently, carbon bricks are the main material used for this part.

1. Damage Mechanisms of Furnace Eye Carbon Bricks

There are two primary types of damage that occur to the carbon bricks used in the bores of industrial silicon furnaces: oxidation and mechanical erosion.

1.1 Carbon Brick Oxidation

Carbon bricks are commonly employed in the bores of industrial silicon furnaces due to their certain advantages. However, they have a significant drawback - a high susceptibility to oxidation. The carbon bricks in the furnace eye are constantly exposed to air over an extended period, which accelerates the oxidation rate. This oxidation process gradually weakens the structural integrity of the carbon bricks, making them more prone to further damage.

1.2 Mechanical Erosion

• Silicon Liquid Discharge: When the silicon liquid is discharged from the industrial silicon furnace, the high - temperature silicon melt flowing out washes against the carbon brcks of the furnace hole. This continuous washing action gradually enlarges the furnace hole, compromising its original shape and function.
• Slag Discharge Issues: In cases where the slag has high viscosity and poor fluidity, slag discharge becomes difficult. If the furnace eye is also hard to open, manual eye - opening operations are required. These operations subject the furnace eye carbon bricks to strong mechanical washing, causing significant damage.
• Intermittent Operation: The industrial silicon furnace operates intermittently. The temperature difference between the silicon output and the plugging hole is large. This rapid change in temperature, from high to low and vice versa, easily causes the carbon bricks to peel off due to thermal stress.
• Unreasonable Current Distribution: An improper current distribution within the submerged arc furnace is also an important factor contributing to the damage of the furnace hole carbon brcks. Uneven current flow can lead to localized overheating or other adverse effects, accelerating the degradation of the carbon bricks.

2. Furnace Eye Repair Methods

The furnace eye is subject to corrosion and mechanical washing by high - temperature furnace gas, molten silicon water, and high - temperature slag, often resulting in an oval - shaped furnace eye. Once the furnace eye becomes too large, it becomes difficult to plug, leading to issues such as run - out and fire. In such cases, the furnace eye needs to be replaced.

2.1 Traditional Furnace Eye Repair Method

In traditional industrial silicon furnaces, technicians are responsible for repairing damaged furnace eyes. The repair process involves the following steps:

• First, they clean up the silicon and slag deposits from the silicon outlet.
• Then, they pour electrode paste both inside and outside the damaged furnace eye.
• Finally, they bind a protective layer using castables.

In the production of the submerged arc furnace, the five furnace holes are used in rotation. The furnace eye must be repaired after 5 - 7 days of use. This frequent repair schedule has a serious impact on the improvement of various technical and economic indicators of the product. Moreover, it has several drawbacks, including high labor intensity, a poor working environment, long time - consumption, high maintenance costs, and low efficiency.

2.2 New Furnace Eye Repair Technology

The traditional furnace eye repair method goes against the policy of cost reduction and efficiency increase. Therefore, a new furnace eye repair technology is urgently needed to address the low - efficiency problem of furnace eye repair. The following is a detailed description of the specific repair technology (a comparison between the new repair technology and the traditional repair process is shown in Figure 1):

• Step 1: Gouging the Damaged Furnace Bore: Use a professional drilling rig to gouge the damaged charcoal brick furnace bore. The depth and diameter of the gouging bore are determined by the degree of damage to the furnace bore. This step aims to remove the severely damaged parts of the carbon bricks, creating a clean and well - defined space for subsequent repair work.
• Step 2: Filling the Furnace Hole with Composite Filler: For the chiseled furnace hole, use a composite filler composed of electrode paste, silicon carbide, pitch, and other materials to fill the furnace hole. The choice of this composite filler is based on its excellent properties. After heating, it has very good fluidity, forming, and bonding capabilities, allowing it to fully sinter with the original furnace hole carbon brick as a whole. Additionally, the silicon carbide material in the filler has certain anti - oxidation and wear - resistance properties, which can effectively slow down the damage caused by oxidation and erosion and extend the life cycle of the furnace eye.
• Step 3: Inlaying a Graphite Carbon Sleeve: The filled furnace eye needs to be inlaid with a graphite carbon sleeve. The graphite carbon sleeve has good wear - resistant mechanical properties and is resistant to oxidation and corrosion. It can effectively protect the furnace eye carbon brick from further damage, providing an additional layer of defense against the harsh operating conditions inside the furnace.
• Step 4: Filling the Gap: Use electrode paste and fine - gap paste to fill the gap between the filler and the graphite carbon sleeve. This step ensures that the furnace hole carbon brick and the carbon sleeve are coked together, creating a strong and integrated structure. It helps to enhance the overall stability and durability of the repaired furnace eye.
• Step 5: Repairing the Chute and Pouring the Protective Layer: Use high - aluminum castable to repair the chute. After the repair is completed, pour a protective layer with electrode paste. This protective layer further safeguards the repaired furnace eye and the surrounding components from potential damage during the production process.

After completing the above repair steps, the repaired furnace eye needs to be baked before it can be put into production. This new technology has been widely promoted in the same industry in China. From its application situation, it can be seen that this technology can effectively extend the life of the furnace eye, reduce the number of furnace eye replacements, lower the cost of furnace eye repair, and improve the output and economic benefits of industrial silicon furnaces.
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