ZHENGSHAN TECHNOLOGY

The self-baking electrode of the ore heating furnace (electric furnace) is sintered from the electrode paste. In the process of preparing, sintering and using the electrode, every link is essential.This article will discuss in detail the quality requirements of the self-baking electrode paste in the mine heating furnace, the sintering process of the electrode, and the causes and treatment methods of electrode accidents.

1. Quality requirements of electrode paste

The quality of the electrode paste directly affects the use effect of the electrode.High-quality electrode paste needs to meet the following requirements：

Raw material quality：

Anthracite: Anthracite is one of the main raw materials for electrode paste, which requires low volatile content, high calorific value and good thermal stability.Anthracite coal calcined in a rotary kiln or electric calciner can eliminate moisture and volatile components, increase density and strength, and improve electrical conductivity.

Metallurgical coke and petroleum coke: Metallurgical coke is produced by coking coal and other coal types in a coke oven, while petroleum coke is a by-product of petroleum refining.Petroleum coke is easily graphitized at high temperatures and is mainly used to prepare airtight pastes.

Coal asphalt and coal tar: As the binder of the electrode paste, the amount of coal asphalt and coal tar should be added appropriately to ensure that the electrode paste is stirred evenly and avoid particle stratification.

Composition ratio：

The content of anthracite coal in the electrode paste usually accounts for 50%, and the anthracite coal needs to be broken into particle sizes below 20mm to ensure that the particles are densely filled to obtain electrodes with high strength and good conductivity.
The amount of binder added is generally 20% to 24% of the solid material. Too little will cause insufficient electrode strength, and too much will make the electrode paste too thin, resulting in uneven tissue.

Additive：

Adding an appropriate amount of crushed graphite and a small amount of coal tar to the airtight paste can reduce the softening point of the binder and improve the electrical and thermal conductivity of the electrode.

2. Analysis of electrode sintering process

The sintering process of the electrode is a complex process of physical and chemical changes, which mainly goes through the following stages：

Warm-up stage：

When the electrode paste is below 100℃, it is in a solid state.In the area with a temperature of 100~200℃ along the copper tile, the electrode paste begins to soften and gradually melts into a liquid state.

Volatiles discharge stage：

When the temperature rises to 200~600℃, the binder in the electrode paste begins to decompose and the volatiles escape, especially at about 400℃, the volatiles are discharged most intensively.

Sintering stage：

The temperature rises from 600℃ to 800℃, and a small amount of residual volatiles continues to be discharged.After 4 to 6 hours, when the electrode is released from the copper tile pressure, the electrode is basically sintered.

High temperature working stage：

Below the copper tile to the working end of the electrode, the temperature continues to rise, and the electrode shell begins to melt or oxidize and fall off.The internal temperature of the electrode can reach more than 2000℃, the temperature at the working end of the electrode is the highest, the chemical reaction is the most intense, and the consumption is the fastest.

3. Causes and treatment methods of electrode accidents

Electrode accidents are common failures in the operation of mine heating furnaces. The main reasons include：

Electrode paste quality problem：

Insufficient amount of graphite crushed, electro-calcined coal, etc. in the electrode paste, leads to a decrease in electrode strength, which is prone to soft and hard break accidents.

Improper operation：

Improper operations such as excessive power failure time and excessive electrode discharge speed can easily lead to electrode accidents.

Equipment problems：

Equipment problems such as damage to the electrode shell and failure of the pressure-discharge system can also lead to electrode accidents.

The methods for dealing with electrode accidents mainly include：

Electrode hard break treatment：

When the electrode is hard-broken at 8001000mm along the lower edge of the copper tile, a power outage should be immediately, the broken head should be placed below the material surface, and then the electrode 150200mm should be discharged, and the lower voltage should be used to send power.Production gradually resumed through the method of grabbing and discharging electrodes.

When the electrode breaks hard at 50~200mm along the lower edge of the copper tile, the electrode head should be pulled out as much as possible, and then the dead phase roasting should be carried out.

Electrode soft break treatment：

In the event of a soft electrode breaking accident, the power should be cut off immediately, the copper tile should be loosened, and the electrode should be seated back so that the hard head of the electrode is in good contact with the electrode paste.

Preventive measures：

Strictly control the quality of the electrode paste to ensure that the amount of raw materials is appropriate.

Standardize the operation to avoid excessive power failure time and excessive electrode discharge speed.

Check the equipment regularly to ensure the normal operation of the electrode shell and the pressure discharge system.

In summary, the quality requirements of the self-baking electrode paste of the mine heat furnace, the electrode sintering process and the handling of electrode accidents are all important links to ensure the stable operation of the mine heat furnace.By strictly controlling the quality of electrode paste, standardizing operation and strengthening equipment maintenance, the occurrence of electrode accidents can be effectively reduced and the production efficiency and safety of mine heating furnaces can be improved.